WO2022232877A1

WO2022232877A1 - A filter system

Info

Publication number: WO2022232877A1
Application number: PCT/AU2022/050417
Authority: WO
Inventors: Michael Charles BREADMORE; Maria Gabriela Paniagua CABARRUS; Rosanne Marieke GUIJT
Original assignee: University Of Tasmania
Priority date: 2021-05-04
Filing date: 2022-05-04
Publication date: 2022-11-10

Abstract

A filter system for filtering particles from an inlet flow of fluid to an instrument for analysis of the fluid, the filter system comprising: a hydrocyclone for separating a feed stream into an overflow stream and an underflow stream; and an H-filter for performing filtration on the overflow stream by diffusion to form a purified stream.

Description

A filter system

Field

The present invention relates to a filter system suitable for use in a portable electrophoresis instrument or in other applications.

Background

Environmental monitoring often includes the analysis of analytes to determine concentration of pollutants or ionic species more generally in bodies of water. Typically, samples are collected from the field, for example rivers and streams, stored and transferred to a qualified laboratory for analysis.

Electrophoresis, encompassing capillary electrophoresis (CE), micellar electrokinetic chromatography (MEKC) and microchip electrophoresis, is a very powerful technique for the analysis of analytes such as ions in a sample Capillary electrophoresis separates and detects charged ions (i.e. anions or cations) through the application of a voltage potential to cause the charged ions to move through a separation capillary at different rates according to their electrophoretic mobility in the presence of a background electrolyte. Where the analytes are neutral (uncharged) species, through control of the background electrolyte composition by, for example, the addition of a surfactant, these analytes can also be separated.

An issue that affects the ability for the CE instrument to be used out in the field is the quality of sample used in the instrument. The capillary of the CE instrument can have an internal channel with a diameter in the region of 10 pm to 50 pm. To put this in perspective, a human hair has a diameter around 70 pm. As can be appreciated, this internal channel can easily be blocked by particulate matter above a certain size which would render the instrument inoperable. It is therefore desirable to prevent such particulate matter from entering the internal channel. The problem of particles in liquid streams can also impact on analytical instruments other than CE instruments. This issue is generally not a problem for lab-based CE instruments as filtration can be performed manually on samples as required. In contrast, a CE instrument that is used in the field may take a sample from a river or stream which may contain significant particulate matter that needs to be addressed without manual intervention.

Attempts have been made to prevent such particulate matter from entering relevant parts of analytical instruments, such as the separation capillary of a CE instrument. Most solutions include a filter system comprising a filter mesh positioned upstream of the capillary that screens out the large particulate matter from the sample. A problem with this solution is that when the filter mesh gets blocked it needs replacing. This issue is generally not a problem for lab-based CE instruments which are easily accessible for servicing. However, CE instrument that are used in the field may be positioned in remote locations that are difficult to access for servicing. The cost of frequent manual intervention (such as filter unblocking) is also desired to be avoided.

Furthermore, to replace the filter mesh, the analysis in CE instrument needs to be ceased. This is undesirable if continuous environmental monitoring is required.

It is desirable to provide a filter system suitable for use with an analytical instrument such as a portable CE instrument that improves at least one of the above disadvantages or at least provides a useful alternative to known systems.

Summary of the Disclosure

The present application provides a filter system for filtering particles from an inlet flow of fluid to an instrument for analysis of the fluid, the filter system comprising: a hydrocyclone for separating a feed stream into an overflow stream and an underflow stream; and an H-filter for performing filtration on the overflow stream by diffusion to form a purified stream. The filter system according to the present invention reduces the amount of particulate matter above particulate matter above a certain size which would otherwise block the internal channel of the CE instrument rendering the instrument inoperable.

Whilst this problem is associated with portable CE instruments, it is not exclusive to portable CE instruments. As can be appreciated, the problem of particles in liquid streams can also impact on analytical instruments other than CE instruments.

In some embodiments, the filter system includes a reservoir located downstream of the hydrocyclone for receiving the overflow stream to transition the overflow stream to a laminar flow regime. Ideally, the overflow stream entering the H-filter to be laminar in order to optimise the rate of diffusion.

A laminar flow regime is typically defined as a flow of fluid having a Reynolds number (Re) less than 2,000. The Reynolds number is the ratio of inertial forces to viscous forces within a fluid that is subjected to relative internal movement due to different fluid velocities. For low Reynolds numbers, i.e. less than 2,000, viscous forces dominate and the fluid particles flow in a straight line. For high Reynolds numbers, i.e. greater than 2,000, inertial forces dominate and the fluid particles flow in vortices. This is known as a turbulent flow regime.

Also provided herein is a filter system for filtering particles from an inlet flow of fluid to an instrument for analysis of the fluid, the filter system comprising: a hydrocyclone for separating a feed stream into an overflow stream and an underflow stream; a reservoir located downstream of the hydrocyclone for receiving the overflow stream to transition the overflow stream to a laminar flow regime; and an H-filter for performing filtration on the laminar flow overflow stream by diffusion to form a purified stream. An advantage to the filter system according to the present invention is that there are no moving parts. Moving parts are potential points of failure.

A further advantage is that the filter system requires no filter paper or mesh that would otherwise need replacing. As such, the filter system according to the present invention can be operated with very little downtime for servicing. The filter system also avoids the need for manual intervention, so that it may be left in the environment for long periods of time (e.g. at least one month, at least 3 months, at least 6 months, at least 12 months or more) without manual intervention.

In some embodiments, the instrument is an electrophoresis instrument, such as a capillary electrophoresis instrument, a micellar electrokinetic chromatography (MEKC) instrument; a microchip electrophoresis instrument; or a gel electrophoresis instrument. Suitably, the instrument is a CE instrument. More suitability, the instrument is a portable CE instrument. Even more suitably, the instrument is the portable CE instrument. However, it is also envisaged that the filter system according to the present invention may be suitable for any instrument used for analysing a flow of fluid and particularly instruments that are sensitive to particulate matter above a certain size.

In some embodiments, the filter system forms part of a portable capillary electrophoresis system having the features as described above. The portable capillary electrophoresis system with filtration may thus comprise: a filter system for filtering particles from a feed stream of a fluid, the filter system comprising: a hydrocyclone for separating the feed stream into an overflow stream and an underflow stream; and an H-filter for performing a filtration on the overflow stream to form a purified stream; - an analyser for analysing analytes in a sample solution from the purified stream, the analyser comprising a separation capillary for separating analytes in the sample solution and a detector for detecting the presence of analytes; a pump that is configured to deliver flow of a sample solution from the purified stream to the analyser and a waste outlet; a valve unit for controlling the direction of flow of the sample solution to either the analyser or the waste outlet; and a sensor for measuring a signal from the analyser corresponding to amounts of analytes in the sample solution.

In some embodiments, the purified stream is delivered to an additional reservoir (or “purified stream reservoir”) that is located downstream of the H-filter. A pump unit may be positioned downstream of the additional reservoir to deliver flow from the additional reservoir to the instrument. The pump unit may be a peristaltic pump. The advantage to positioning the additional reservoir between the H-filter and the peristaltic pump is that the additional reservoir acts as a dampener that suppresses the oscillations in flow rate produced by the peristaltic pump. This assists in maintaining laminar flow through the H-filter.

In some embodiments, the hydrocyclone removes particles of greater than 300 pm in size from the feed stream. The efficiency of the removal of particles from the hydrocyclone is dependent on the size of the particles. For example: particles greater than 150 pm in size are removed at an efficiency between 70% and 95%; particles greater than 100 pm in size are removed at an efficiency between 40% and 70%; and particles greater than 50 pm in size are removed at an efficiency between 10% and 40%, such that the overflow stream is substantially free of particles of the indicated size.

The overflow stream following hydrocyclone particle removal is substantially free of particles of greater than 300 pm in size. In some embodiments, it may be substantially free of particles greater than 200 pm in size. In the event that a guide is required, substantially free refers to an amount that is less than 5%, less than 2%, less than 1% or less than 0.1% by mass of the fluid stream of. Most commonly, substantially free means that the mass of the particles of that size is less than 1% by mass of the fluid stream. In the embodiments exemplified below, 100% of the particles of greater than 200 pm in size were removed in the hydrocyclone filtration step. Particle sizes throughout this specification are assessed by reference to the maximum particle diameter, and the degree of particle removal is calculated by reference to the number of particles of that particle size that are separated, as a percentage. For test purposes, the degree of particle removal can be assessed by using a defined standard provided by a manufacturer, with a controlled particle content. An optical microscope is used to verify the particle size of particles in the standard. When testing particle removal using a sample taken from an environmental water source (e.g. one containing soil particles), to allow comparison to the information presented herein, particle size is suitably measured using dynamic light scattering with an optical microscope. Otherwise, any other technique may be used, such as optical microscopy, scanning electron microscopy or dynamic light scattering. Removal of particles of any particular size indicated refers to at least 90% removal, or at least 95% removal, or at least 99% removal, or at least 99.9% removal of the particles. Preferably, references to “removal” of particles of any particular size indicated refers to at least 99% removal.

In some embodiments, the H-filter can separate particulate matter has a size between 0.75 pm and 35 pm from the overflow stream. The H-filter should remove at least 80% and potentially up to 100% of particles having a size greater than 5 pm from the overflow stream. The H-filter preferably removes at least 90% of particles having a size greater than 5 pm from the overflow stream, and potentially up to 100% of such particles. The H-filter preferably removes at least 99% of all particles having a size greater than 5 pm from the overflow stream. The H-filter preferably removes at least 60% of particles having a size greater than 1 pm from the overflow stream, such as between 60% and 90% of said particles. Preferably, the H-filter is effective to remove at least 75% of particles greater than 1 pm in size, such as between 75% and 95% of particles having a size greater than 1 pm. More preferably, the H-filter is effective to remove 80% of all particles having a size greater than 1 pm. As previously discussed, a separation capillary in an electrophoresis instrument typically has an internal channel with a diameter between 10pm and 50pm. Therefore, the H-filter should be effective at separating particle matter of the range that is likely to block the internal channel.

In some embodiments, any particulate matter remaining in the purified stream is less than 1.5 pm in size.

In the context of this application, particle size is considered in terms of the maximum diameter of the particle. For example: a spherical shaped particle having a diameter of 1.25 pm would be considered to have a particle size of 1.25 pm and an elongate particle having a width of 0.5 pm and a length of 1.5 pm would be considered to have a particle size of 1.5 pm.

The present application further provides a method for filtering particles from a fluid, the method comprising:

- applying a centripetal force to the fluid to separate a feed stream of the fluid into an overflow stream and an underflow stream; and

- subjecting the overflow stream to filtration by diffusion to form a purified stream.

In some embodiments, the method further comprises the step of transitioning the overflow stream to a laminar flow regime prior to subjecting it to filtration by diffusion.

- separating a feed stream of the fluid using a hydrocyclone in a first separation step into an overflow stream and an underflow stream; and

- subjecting the overflow stream to particle filtration using an H-filter to form a purified stream.

Also provided herein is a method for filtering particles from a fluid, the method comprising:

- separating a feed stream of the fluid using a hydrocyclone in a first separation step into an overflow stream and an underflow stream;

- directing the overflow stream to a reservoir located downstream of the hydrocyclone and transitioning the overflow stream to a laminar flow regime; and

- subjecting the laminar flow overflow stream to particle filtration using an H-filter to form a purified stream.

The overflow stream produced in the first separation step has a reduced load of particles compared to the feed stream of the fluid. The size of particles separated in each separation step may be as indicated above.

Also provided herein is a method for the detection of analytes in an environmental water source, the method comprising:

- separating a feed stream of a fluid environmental water source using a hydrocyclone in a first separation step into an overflow stream and an underflow stream; and

- subjecting the overflow stream to particle filtration by diffusion using an H-filter to form a purified fluid stream;

- directing the purified fluid stream to an instrument for analysis, the instrument comprising:

- an analyser for analysing analytes in a sample solution taken from the purified fluid stream, the analyser comprising a separation capillary for separating analytes in the sample solution and a detector for detecting the presence of analytes;

- a pump that is configured to deliver fluid flow to the analyser and a waste outlet;

- a valve unit for controlling the direction of fluid flow to either the analyser or the waste outlet;

- a sensor for measuring a signal from the analyser corresponding to amounts of analytes in the sample solution;

- operating the pump to deliver sample solution to the waste outlet;

- actuating the valve unit so that fluid flow is delivered to the analyser only;

- receiving a signal from the sensor corresponding to amounts of analytes in the controlled volume of sample solution at the analyser; and

- processing the signal from the sensor to determine the amounts of analytes in the controlled volume of sample solution.

In some embodiments, the instrument is a capillary electrophoresis instrument. The instrument may be a portable capillary electrophoresis instrument, in particular. However, it is also envisaged that the instrument may be any instrument suitable for measuring amounts of analytes a sample solution, for example through micellar electrokinetic chromatography (MEKC), microchip electrophoresis or gel electrophoresis.

The analyser serves to separate analytes in the sample solution and detect the presence of analytes. Components suitably include a separator for separating the analytes, and a detector for detecting the presence of the analytes.

In some embodiments, the sample solution is taken from an ‘environmental water source’. An ‘environmental water source’ is any water source that is open to the external environment. Such water sources include water from: natural waterways (i.e. rivers, streams, lakes, canals), runoff water from factories, chemical plants or power stations; man-made waterways (i.e. reservoirs, dams), drinking water, aquaculture streams or other outdoor bodies of water. In some embodiments, the instrument includes a fluid conduit for collection of sample solution from an environmental water source. The fluid conduit may provide for continuous collection of sample solution from the environmental water source. The pump operates to deliver fluid flow of sample solution to an analyser or to the waste outlet, depending on the timing in the sample analysis sequence and the assessment of the signal from the sensor. The sample solution may be subjected to analysis in combination with a reagent. The reagent may be combined with the sample solution prior to pumping or delivery to the analyser. The reagent may be any reagent that enables or improves detection of the analytes in the sample solution. Examples include fluorescent reagents (such as fluorescein isothiocyanate, fluorescamine, amine-reactive labelling dyes such as Cy5® NHS esters and analogues thereof, other reactive dyes and similar molecules) and colourimetric reagents (such as 4-(2- pyridylazo)resorcinol, ethylenediamine tetraacetic acid and 1 , 10- phenanthroline).

The process of electrophoretic separation also requires a background electrolyte to be delivered to the analyser. The background electrolyte may be delivered to the analyser in advance of the sample solution and following delivery of the sample solution. A second pump may be used to deliver the background electrolyte solution to the analyser. Valves may also be used to control direction of flow of background electrolyte to either a waste outlet (such as the waste outlet referred to previously or another waste outlet), or to the analyser. Wastes may be collected to one waste reservoir.

The background electrolyte may be of any suitable composition as known in the art for the analytical technique being performed. The background electrolyte may comprise one or more buffers, and any other typical electrolyte components. As examples, the background electrolyte may be selected from any one or combination of the following: sodium tetraborate (Na2B40z); N- tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS); tris(hydroxymethyl)aminomethane)(TRIS); N-cyclohexyl-2-aminoethanesulfonic acid (CHES), N-cyclohexyl-3-aminopropanesulfonic acid (CAPS); N-(2- Hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES); 2-(N- Morpholino)ethanesulfonic acid(MES), bis(2-hydroxyethyl)amino- tris(hydroxymethyl)methane (BIS-Tris), acetic acid (CH3COOH), formic acid (HCOOH), phosphoric acid (H3PO4), ammonia (NH3), sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH). . In embodiments where the analyte is a neutrally charged species, the background electrolyte may comprise a charge surfactant. An example of a charged surfactant is sodium dodecyl sulphate. The charged surfactant interacts with neutrally charged analytes, and the analytes are separated in the separation capillary on the basis of the extent to which they interact with the charged surfactant. This may be used in the case of MEKC. For charged analytes, neutral surfactants can also be used to affect the separation, including surfactants such as Brij 35 and Tween 20.

In some embodiments, the detector is an optical sensor. The detector may be a contactless conductivity detector. The detector may alternatively be an electrochemical detector.

The analytes that may be the subject of analysis may depend on the condition being monitored in the water source. In some embodiments, the analytes to be detected may be selected form one or more of anions such as nitrate, nitrite, phosphate, ammonium, sulphate, fluoride, chloride perchlorate, and/or cations such as zinc, copper, cobalt and heavy metals and the like. Suitably, the detector can detect the presence of two or more ionic species selected from the above. More suitably, the detector can detect the presence of three or more species from the above.

In some embodiments, the waste outlet is connected to a waste reservoir. The waste outlet may be fully or partially submerged by fluid within the waste reservoir and thus the flow of fluid from the waste outlet being affected by the level in the waste reservoir. Alternatively, the waste outlet may be arranged (for example as a weir) such that the flow of fluid from the waste outlet can free discharge under gravity. In some embodiments, the separation capillary is a fused silica capillary.

In some embodiments, the separation capillary has an internal channel having diameter of 100pm or less. Suitably, the capillary has an internal channel having a diameter of 80pm of less. Even more suitably, the capillary has an internal channel having a diameter between 10pm and 50pm.

In some embodiments, the processor can determine the amounts of analytes in the sample solution on a parts-per-million scale. Suitably, the increments of analysis are 1 or 0.1 parts-per-million or less.

In some embodiments, the processor can determine the amounts of analytes in the sample solution on a parts-per-billion scale.

In some embodiments, the processor can determine the amounts of analytes in the sample solution on a microMol/litre scale.

In some embodiments, the pump is a peristaltic pump comprising a rotor. An advantage to using a peristaltic pump is that it can be miniaturised. However, it is also envisaged that the pump may any other kind of positive displacement pump, such as a diaphragm pump, a gear pump, a lobe pump, or a vane pump.

The applicant has found that increasing or decreasing the number of lobes on the pump rotor can alter the frequency of the oscillations in pressure and flow rate produced during the pumping cycle.

In some embodiments, a discharge outlet of the pump delivers fluid flow through a main conduit and a bypass line that extends off the main conduit; the main conduit delivers fluid flow to the analyser and the bypass line delivers fluid flow to the waste outlet, the valve unit being positioned on the bypass line. The valve unit may be actuated to a closed position such that the pump unit delivers fluid flow along the main conduit to the analyser only. Adopting a bypass line avoids the use of a modulating control valve.

In some embodiments, the valve unit is a solenoid valve. The valve unit may have a valve member that is a selected from any one of a poppet, gate, butterfly or needle valve member.

In some embodiments, the portable capillary electrophoresis instrument includes a pair of electrodes for providing a voltage potential across the sample solution in the separation capillary. The voltage potential produces an electrical field which drives electro-kinetic/electro-osmotic movement of the analytes in the sample solution to separate the analytes. The pair of electrodes may comprise: (a) a negatively charged electrode (cathode) and a grounded electrode, or (b) a positively charged electrode (anode) a grounded electrode, or (c) a cathode and an anode.

In some embodiments, the portable capillary electrophoresis instrument comprises a controller for controlling the flow of fluid to the analyser and the voltage applied to the pair of electrodes to produce the following sequence of steps:

(1 ) injection of sample into the separation capillary without flow of background electrolyte through the separation capillary;

(2) injection of background electrolyte through the separation capillary to flush sample from the separation capillary without the application of voltage potential across the pair of electrodes; and

(3) application of a voltage potential across the pair of electrodes following the flushing step, with flow of background electrolyte through the separation capillary, to effect separation of the analytes in the sample solution.

In some embodiments, steps (1) and (2) are performed by a single pump unit. Alternatively, steps (1) and (2) may be performed by separate pump units.

In some embodiments, the portable electrophoresis instrument can perform up to 5,000 samples per litre of background electrolyte. Suitably, the portable electrophoresis instrument can perform up to 6,000 samples per litre of background electrolyte. Even more suitably, the portable electrophoresis instrument can perform up to 7,000 samples per litre of background electrolyte. The number of samples analysed per litre of background electrolyte may be at least 1000 per litre, at least 2000 per litre, at least 3000 per litre or at least 4000 samples per litre of background electrolyte. This allows for many analytical cycles to be performed with low consumption of consumables, to allow for the device to remain in the environment for long time periods without the need for manual intervention.

In some embodiments, the portable electrophoresis instrument is housed in a box having the following range of dimensions: 15 to 50 cm in length; 5 to 30 cm in width; and 2 to 20 cm in depth. Suitably, the portable electrophoresis instrument can be housed in a box having the following range of dimensions: 15 to 30 cm in length; 10 to 20 cm in width; and 5 to 10 cm in depth. Even more suitably, the portable electrophoresis instrument can be housed in a box having the following dimensions: 21 cm in length; 10 cm in width; and 7 cm in depth.

In some embodiments, the portable electrophoresis instrument weighs less 5.0 kg. Suitably, the portable electrophoresis instrument weighs less than 2.5 kg. More suitably, the portable electrophoresis instrument weighs less than 1.0 kg.

In some embodiments, the analyser serves to separate analytes in the sample solution and detect the presence of the analytes. The analyser suitably comprises a separation capillary for separating analytes in the sample solution and a detector for detecting the presence of analytes.

In some embodiments, the instrument defined in the above described method is a CE instrument. Suitably, the instrument is a portable CE instrument. More suitably, the instrument is the portable CE instrument as previously described. However, it is also envisaged that the above described method could similarly be used with other instruments for measuring amounts of analytes a sample solution, for example micellar electrokinetic chromatography (MEKC), microchip electrophoresis, gel electrophoresis.

Brief Description of Drawings

Notwithstanding any other forms which may fall within the scope of the filter system, portable electrophoresis instrument and method as set forth in the Summary, specific embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a portable capillary electrophoresis system comprising a portable capillary electrophoresis instrument and a filter system according to an embodiment of the present invention;

Figure 2 is a side view of a hydrocyclone of the filter system shown in Figure 1 ;

Figure 3 is a plan view of the H-filter of the filter system shown in Figure 1 ;

Figure 4 is a schematic view of the H-filter shown in Figure 3;

Figure 5A is a side view of the outlet sample reservoir (OSR) of the filter system shown in Figure 1 ;

Figure 5B is a front view of the outlet sample reservoir (OSR) of the filter system shown in Figure 1 ;

Figure 6A is a side view, in schematic, of the outlet sample reservoir (OSR) shown in Figure 5A;

Figure 6B is a front view, in schematic, of the outlet sample reservoir (OSR) shown in Figure 5B; Figure 7 is a plan view of the H-filter unit and outlet sample reservoir (OSR) of the filter system shown in Figure 1 ;

Figure 8 is a line graph showing the size and volume frequency of particulate matter separated from the solution using the hydrocyclone;

Figure 9 is a line graph showing the size and volume frequency of particulate matter separated from the solution using the H-filter; and Figure 10 is a bar chart showing the percentage of different sizes of particulate matter separated from the solution using the H-filter.

Figure 11 is a schematic view the portable capillary electrophoresis instrument shown in Figure 1 ;

Detailed Description of Specific Embodiments

Figure 1 shows an embodiment of a portable capillary electrophoresis system according to the present invention. The portable capillary electrophoresis system comprising a portable electrophoresis instrument 10 and a filter system 100.

The portable capillary electrophoresis (CE) instrument 10 includes: an input system 12; an analyser 14; waste systems 16a, 16b; a background electrolyte (BGE) system 18; and a series of conduits that connect the systems together.

The filter system 100 is positioned upstream of, and fluidly connected to, the instrument 10. The filter system 100 filters particles from an inlet flow of fluid entering the instrument 10. The filter system 100 comprises: a hydrocyclone 110; reservoirs 104, 106, 108, 130; an H-filter unit 120; and peristaltic pumps

102a, 102b, 102c. Filter System

Figure 2 shows the hydrocyclone 110, which is 3D printed from Visijet® M3 crystal. The hydrocyclone 110 is a solid block with a centrally positioned cone shaped recess 112 and a series of internal channels 114a, 114b, 116, 118 intersecting with the recess 112. The cone shaped recess 112 is arranged in the solid block such that the narrowest end of the cone points in a downward direction. The channels comprise: a pair of feed stream inlet channels 114a, 114b that intersect tangentially with the cone shaped recess 112, on opposing positions on the recess 112; and overflow and underflow stream outlets channels 116, 118 that intersect with opposite ends of the recess 112 along its longitudinal axis.

In use, a feed stream containing particulate matter travels through the inlet channels 114a, 114b and into the recess 112. Once inside the recess 112, the direction of the feed stream is guided by the wall of the cone shaped recess 112 to form a vortex flow. The vortex flow inside the hydrocyclone gives rise to a low-pressure zone along the longitudinal axis. The particulate matter is separated from the feed stream by the accelerating centrifugal force based on size, shape, and density of the particles. Large, heavy, fast settling particles move towards the wall of the recess 112 and follow the flow out through the underflow stream outlet channel 118 due to the influence of high centrifugal forces. In contrast, for the very fine and slower settling particles, the centrifugal force is overborne by the drag forces and turbulent diffusion and hence they remain dispersed inside the vortex. The smaller particles towards the centre of the vortex move into the low-pressure zone, and travel in an upward direction through the overflow stream outlet channel 116.

The separation of a particle in the vortex is governed by the ratio of the centrifugal force (F_c, see equation 1 below) to buoyancy (Ft_>, see equation 2 below) and drag forces (Fd, see equation 3) acting on the particle. F_d = —3pO_rmn_g (equation 3)

Where m particle mass;

Vt tangential velocity; r radial distance;

Dp particle diameter;

PP particle density; Pf fluid density; Vr radial velocity; and m viscosity.

Figure 3 shows the H-filter unit 120, which is similarly 3D printed from Visijet® M3 crystal. The H-filter unit 120 comprises a solid block with a series of internal channels 122a, 122b, 123, 124a, 124b that approximate the appearance of the letter ‘FT when viewed from above. (It is noted that the expression H-filter does not require the channels to be in a precise Ή” pattern, and that some variation in the arrangement of the channels is permitted.) The internal channels comprise a main channel 123 which extends along the longitudinal axis of the block, the channel defining a first end and a second end. A pair of inlet channels 122a, 122b bifurcate away for the first end of the main channel 123. Each inlet channel 122a, 122b has a respective inlet opening 121a, 121 b. A pair of outlet channels 124a, 124b bifurcate away from the second end of the channel 123. Each outlet channel 124a, 124b has a respective outlet opening 125a, 125b.

Figure 4 shows a schematic of the H-filter unit 120 with dimensions applied to each of the channels. The main channel 123 has a length of 20.0 mm, a width of 1.5 mm and a depth of 1.0 mm. The inlet and outlet channels 122a, 122b,

124a, 124b each have a length of 10mm, a width of 0.75mm and a depth of 1.0mm.

The H-filter unit 120 separates particulate matter from a cyclone overflow stream by diffusion. Diffusion is the net movement of something from a region of high concentration to a region of low concentration via a concentration gradient. The cyclone overflow stream has a relatively higher concentration of particles than the purified stream and thus the particles in the overflow stream move towards the purified stream. The H-filter requires the overflow stream and the purified stream to enter into the H-filter and pass alongside each other as separate streamlines within an internal channel of the H-filter. In order to maintain separate streamlines, the fluid flow of the overflow stream and the purified stream must be laminar.

The cyclone overflow stream, containing a high concentration of particles, enters the H-filter unit 120 via one of the inlet opening 121 b and travels along the inlet channel 122b towards the main channel 123. A separate water supply, which is held in reservoir 108 in Figure 1 and provides a separate water stream, is delivered to the H-filter via the pump unit 102c and enters the H-filter unit 120, via the other inlet opening 121a, and travels along the inlet channel 122a towards the main channel 123. The separate water stream contains no particles, or only a very low concentration of particles (relative to the cyclone overflow stream). Preferably the separate water stream is substantially particle free. The water stream may, for example, be a distilled water stream. Once inside the main channel 123, the overflow stream and the separate water stream travel alongside each other as separate streamlines. The smaller particles diffuse from the overflow streamline and into the separate water streamline, whereas larger particles in the overflow streamline do not have time to diffuse across the streamlines. The separate water streamline is loaded with substances (including dissolved substances, molecules and particles up to a cut-off particle size) during the time that the streams travel alongside one another, and through this process the separate water stream takes on the composition of the overflow stream other than for the larger particles which do not pass across. Accordingly, the separate water stream becomes what is referred to herein as a “purified stream”. The purified stream which is free of the larger particles from the cyclone overflow stream exits from the main channel 123 along the outlet channel 124a and out of the H-filter 120 via the outlet opening 125a. In contrast, the depleted overflow streamline containing the remaining larger particles that did not pass into the purified stream exits the from the main channel 123 along the outlet channel 124b and out of the H-filter 120 via the outlet opening 125b.

The diffusion length is given by equation 4 below, which defines the average distance (x) a molecule in the solution diffuses for a given time (t) and diffusion coefficient (D). The diffusion coefficient (D) is expressed in equation 5 as being proportionate to temperature (T) and the boltzmann constant (k) and being inversely proportionate to viscosity (m) and molecule radius (R_v). As such, the diffusion can be tuned by selecting the flow rate of the fluid through the H-filter, as this is equivalent to altering the amount of time a particular molecule spends in the main channel 123. The diffusion may also be tuned by selecting the viscosity (m) of the fluid in the H-filter. = V2 Dt (equation 4)

D = (equation 5)

Figures 5A, 5B, 6A, 6B show an outlet sample reservoir (OSR) 130. The OSR 130 is 3D printed from Visijet® M3 crystal in the form of a solid block with a pair of cuboid shaped internal chambers 132a, 132b. Each chamber 132a, 132b has a volume of 350 mI_. Each chamber 132a, 132b has a respective inlet opening 134a, 134b located in a front face of the block and a respective outlet opening 136a, 136b located in a top face of the block. Figure 10 shows the OSR connected to the H-filter unit 120. The inlet openings 134a, 134b of the OSR 130 are connected to the respective outlet openings 125a, 125b of the H- filter unit 120. A constant fluid level is maintained in the chambers 132a, 132b by overfilling the chambers. This ensures a constant static head which assists in maintaining laminar flow through the H-filter unit 120. A small fraction of flow from the first chamber 132a is pumped out through the outlet opening 136a and into the CE instrument 10 by the sample pump unit 22. Flow from the second chamber 132b is pumped out through the outlet opening 136b and into a waste reservoir 138 via a waste pump unit 102d.

Referring back to Figure 1 , an inlet flow enters into the filter system 100 via a first pump unit 102a and is pumped along a first conduit to the hydrocyclone 110. The first conduit divides into two conduits immediately before reaching the hydrocyclone 110. Each of the two conduits fluidly connects to the respective inlet channels 114a, 114b of the hydrocylone 110. Flow enters into the recess 112 and forms a vortex flow inside the hydrocyclone. Large, heavy, fast settling particles move towards the wall of the recess 112 and follow the flow out through the underflow stream outlet channel 118 due to the influence of high centrifugal forces and into an underflow reservoir 106. What remains of the feed stream, containing dissolved substances, molecules and smaller particles, exits the recess through the overflow stream outlet channel 116 and along a third conduit to an overflow stream reservoir 104. A second pump unit 102b draws a laminar flow of overflow fluid from the overflow stream reservoir 104 and along a fourth conduit to the H-filter unit 120 where it enters the second inlet channel 122b via the second inlet opening 121b. A third pump unit 102c draws a laminar flow of water (for example, distilled water, or substantially pure water) from a water reservoir 108 and along a fifth conduit to the H-filter unit 120, where it enters the first inlet channel 122a via the first inlet opening 121 a. The overflow fluid flow and the separate stream of water travel along the respective inlet channels 122a, 122b and into the main channel 123. Due to being laminar, the overflow stream and separate water stream form separate streamlines within the main channel 123 that do not mix. However, dissolved substances, molecules and small particles diffuse from the overflow stream into the separate water stream to produce the purified stream. The residual overflow stream, containing the residual larger particles, exits the main channel 123 via the outlet channel 124b, travels through the outlet opening 125b and enters into the second chamber 132b of the OSR 130 via inlet opening 134b. A fourth pump 102d pumps the residual components of the overflow stream from the second chamber 132b along a sixth conduit and into a waste reservoir 138. The purified stream, containing dissolved substances, molecules and small particles that diffused over from the overflow streamline, exits the main channel 123 via the outlet channel 124a, travels through the outlet opening 125a and enters into the first chamber 132a of the OSR 130 via inlet opening 134a. The sample pump unit 22 pumps fluid from the first chamber 132a along a seventh conduit and into the CE instrument 10.

All pump units 102a, b, c and d are miniature peristaltic RP-Q1 Series pumps.

All of the conduits that connect the above described components are Teflon tubes of 0.75 mm internal diameter.

Figure 8 is a line graph showing the size and volume frequency of particulate matter separated from the solution using the hydrocyclone 110. As can be seen from the graph, the hydrocyclone removes particles of greater than 200 pm in size from the feed stream. In other words, the hydrocyclone 110 effectively filters particles above 200 pm in size from the feed stream.

Figure 9 is a line graph showing the size and volume frequency of particulate matter separated from the solution using the H-filter unit 120. Figure 10 is a bar graph showing the percentage of different sizes of particulate matter separated from the solution using the H-filter unit 120. As can be seen from these graphs, the H-filter unit 120 removes 99% of particulate matter having a size greater than 1 26pm when producing the purified stream from the laminar flow overflow stream.

The capillary of the CE instrument has an internal channel with a diameter of 25 pm. By removing substantially all particulate matter having a size greater than 1.5 pm, the risk of blocking the capillary is significantly reduced.

The advantage to the filter system 100 according to the present invention is that there are no moving parts. The hydrocyclone 110 and H-filter 120 operate solely on fluid dynamic principles. The hydrocyclone 110 separates particles from a solution based on the ratio of their centripetal force to fluid resistance. The H-filter 120 separates particles from a solution based on diffusion.

Reducing the number of moving parts in a system reduces the number of potential points of failure of the system. As such, the filter system 100 according to the present invention can be operated with very little downtime for servicing.

Portable Capillary Electrophoresis (CE) instrument

Figure 11 shows the portable capillary electrophoresis (CE) instrument 10 of the portable capillary electrophoresis system shown in Figure 1.

A cross-piece 20, being a junction between four conduits, fluidly connects the analyser 14 to the waste systems 16a, 16b, the input system 12, and the BGE system 18.

The input system 12 comprises: a sample pump unit 22; a complexation reaction reagent and internal standard (CRR + IS) pump unit 24; a T-piece 26 and a reaction/mixing loop 28.

The sample pump unit 22 is configured to deliver an injection of sample solution into the instrument 10.

The CRR + IS pump unit 24 is configured to deliver an injection of a mixture of complexation reaction reagent (CRR) and internal standard (IS) into the instrument 10. The CRR forms a ‘complex’ with the sample solution. The formation of a complex is generally indicated by a colour change which makes the analytes more visible to an optical sensor during the analysis. The IS is a solution containing a known quantity of analytes of a particular type. The IS behaves in a predictable manner during electrophoretic separation which enables for the results of the analysis of the sample solution to be calibrated.

As such, the IS ensures the performance reliability of electrophoretic separation.

The reaction/mixing loop 28 is a helical conduit for mixing the CRR, IS and sample solution together. The reaction mixing loop 28 works by mixing the reagents by diffusion but also secondary flows (i.e. vortices) due to the geometry of the helical conduit.

The T-piece 26 is a three-branch junction for fluidly connecting three conduits together. Outlets of the sample pump unit 22 and CRR + IS pump unit 24 are fluidly connected to opposing branches of T-piece 26. The remaining branch of the T-piece 26 fluidly connects to an inlet of the reaction/mixing loop 28. An outlet of the reaction mixing loop 28 fluidly connects to a branch of the cross piece 20.

The analyser 14 analyses the analytes in the sample solution. The analyser 14 comprises a fused silica capillary (FSC) 30 and an optical sensor 32. The FSC 30 has a length of 50cm, an external diameter of 360 pm, and an internal channel with a diameter of 25 pm. The optical sensor 32 comprises a light- emitting diode (LED), a photodetector, and an optical interface.

The optical sensor 32 is positioned around the capillary 30 with the LED positioned on one side of the capillary 30 and the photodetector positioned on an opposing side of the capillary 30. The LED emits light of a particular wavelength and/or frequency through the capillary 30 and the photodetector receives light from the LED. The analytes in the capillary 30 alter the wavelength and/or frequency of the light as it passes through the capillary 30.

As such, the presence of analytes in the sample solution in the capillary 30 can be determined. During electrophoresis, the optical sensor 32 can be used to measure the migration time and migration distance data of the analytes. This data can then be processed to determine the amounts of specific analytes in the sample solution.

The waste system 16a comprises a background electrolyte (BGE) chamber 33, a valve unit 34 and a waste vial 35. These components are fluidly connected to each other, with the BGE chamber 33 positioned upstream, the waste vial 35 positioned downstream and the valve unit 34 disposed between the BGE chamber 33 and the waste vial 35. The BGE chamber 33 fluidly connects to a branch of the cross-piece 20.

The BGE chamber 33 contains a small amount of BGE to provide buffer capacity during electrophoresis to avoid pH changes due to electrolysis. The BGE chamber 33 is made by locking a male luer adapter and a 23G metal needle. The metal needle is grounded outside to build a circuit loop for carrying out electrophoresis. The grounding of the metal needle provides a grounded electrode 31 at a position suitable to apply a voltage potential across the separation capillary 30. A grounded electrode may be provided elsewhere provided the required voltage potential is applied across the separation capillary for performing the analyte separation.

The valve unit 34 controls the direction of flow to either the analyser 14 or the waste vial 35. The valve unit 34 is a three-way miniature solenoid valve.

The waste vial 35 is a reservoir that sample solution is discharged to when not being analysed by the analyser 14. The waste vial 35 is 1.5 imL centrifuge tube. Two openings are provided in a side wall of the waste vial 35: a top opening 40, located near the top of the waste vial 35; and a bottom opening 38, located beneath the top opening 40. When the valve unit 34 is in an open position, sample solution flows through the valve unit 34 into the first the waste vial 35 through the bottom opening 38, leaving the waste vial 35 through the top opening 40 and into a waste bag 42. This design ensures a constant liquid level in the waste vial 35 to assist in maintaining a steady hydraulic head in the system.

The background electrolyte (BGE) system 18 comprises a BGE pump unit 44 that delivers a BGE solution into the separation capillary 30 via the cross-piece 20. For further description of background electrolytes and the steps performed in capillary electrophoresis for the detection of ions, reference is made to WO201 4/026224, the entirety of which is incorporated by reference.

The waste system 16b comprises an auxiliary BGE pump unit 46 and an auxiliary waste vial 48. The auxiliary waste vial 48 is a 1.5 mL centrifuge tube. However, a larger reservoir may be provided as required for longer-term monitoring. Two openings are provided in a side wall of the auxiliary waste vial 48: a top opening 54, located near the top of the auxiliary waste vial 48; and a bottom opening 50 located beneath the top opening 54. The auxiliary BGE pump unit 46 is fluidly connected to the bottom opening 50 in the auxiliary waste vial 48. The auxiliary BGE pump unit 46 delivers a BGE solution into the auxiliary waste vial 48. The purpose of the auxiliary BGE pump unit 46 is to periodically replace the BGE solution in the auxiliary waste vial 42. The reason for replenishing the BGE solution is that the pH of the BGE solution can change over time due to electrolysis. Changes in pH can affect the accuracy/precision of the analysis. The auxiliary waste vial 42 also comprises a central opening 52, positioned intermediate the top opening 54 and the bottom opening 50, which receives flow of fluid from the analyser 14. As flow of fluid enters the central opening 52 from the analyser 14 into the auxiliary waste vial 48, flow exits the auxiliary waste vial 48 under gravity through the top opening 54 and into a waste bag 56. This design ensures a constant liquid level in the auxiliary waste vial 48 to assist in maintaining a steady hydraulic head in the system.

The auxiliary waste vial 48 also contains an electrode 58 for applying a high voltage (approximately 8.5 kV) between the electrodes 58, 31 to initiate electrophoretic separation of the sample solution. The counter electrode 31 is the grounded electrode referred to previously. Depending on whether a positive or negative potential is applied, this electrode may function as a cathode or an anode.

The pump units 22, 24, 44 and 46 are miniature peristaltic RP-Q1 Series pumps. Peristaltic pumps, also known as roller pumps, are a type of positive displacement pump which comprises flexible tube fitted inside a circular pump casing and a centrally located rotating pump rotor with rollers or lobes attached around the circumference of the rotor. The rollers/lobes are configured to compress the flexible tube and squeeze a fluid along the flexible tube as the rotor rotates. This process is called peristalsis and found in many biological systems such as the gastrointestinal tract. The advantage to using a peristaltic pump is that the pump unit can be miniaturised.

Check valves 60, 62 are positioned at the discharge of pumps units 24, 44 to prevent reverse flow through these pumps when only the sample pump unit 22 is producing flow of fluid. This assists in maintaining a steady hydraulic head in the system during the analysis of the sample solution.

The conduits that connect all of the above described components are Teflon tubes of 0.75 mm internal diameter. The tee piece 26, cross piece 20 and other fittings are made of polyetheretherketone (PEEK). Any other suitable materials may be used.

The instrument 10 also includes a controller comprising a processor, non- transitory memory and sensors. The sensors comprise an optical sensor 32 that measures a signal corresponding to the amounts of analytes in the sample solution. The processor and non-transitory memory are in the form of a laptop and a data acquisition (DAQ) module. The processor processes data from the voltage sensor and optical sensor 32 and controls the pump units 22, 24, 44, 46 and valve unit 34 based on a programmed sequence. The memory stores instructions executable by the processor and data from the voltage sensor and optical sensor 32. The memory includes, for example, a program storage area and a data storage area. The program storage area and the data storage area can include combinations of different types of memory, such as read-only memory (“ROM”), random access memory (“RAM”) (e.g., dynamic RAM [“DRAM”], synchronous DRAM [“SDRAM”], etc.), electrically erasable programmable read-only memory (“EEPROM”), flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic memory devices.

Controller/method

At the start of the electrophoresis process the sample and CRR+IS pump units 22, 24 are both delivering flow and the valve unit 34 is in the open position.

The sample pump unit 22 delivers a flow of sample solution at a flowrate of approximately 0.2 mL/min. The CRR+IS pump unit 24 delivers flow of a solution containing a complexation reaction reagent and an internal standard at a flowrate of approximately 0.2 mL/min). The solutions from both pump units 22, 24 are mixed together in the reaction/mixing loop 28 to form a complex solution. The complex solution then enters the cross-piece 20 and primes the cross-piece 20. Once the cross-piece 20 is primed, the CRR+IS pump unit 24 and sample pump unit 22 are both stopped. While the valve unit 34 is in the open position, the majority of flow from both pump units 22, 24 is delivered through the cross-piece and to the waste vial 35. This is because the headloss due to friction through the capillary 30 is such that the hydraulic gradient is less favourable in the direction towards to auxiliary waste vial 48 than the waste vial 35. The sample pump unit 22 is then restarted and the valve unit 34 is actuated to close and reopen again at specific time intervals to deliver a controlled volume of sample solution to the analyser 14. Actuating the valve unit 34 to the closed position redirects fluid flow from the sample pump unit 22 through the capillary 30 to the auxiliary waste vial 48 because the valve unit 34 obstructs the fluid flow path to the waste vial 35. Actuating the valve unit 34 to the open position redirects fluid flow from the sample pump unit 22 back to the waste vial 35 due to the favourable hydraulic gradient in this direction.

After sample solution has been delivered through the capillary 30, the cross piece 20 and the BGE chamber 33 are flushed with BGE from BGE pump unit 44 for 60 s at approximately 0.3 mL/min. A voltage of approximately 8.5kV is applied to the sample solution via the electrodes 58, 31. The voltage causes the analytes in the sample solution to migrate under elecro-kinetic/electro-osmotic movement. The photodetector in the optical sensor 32 measures a signal corresponding to the absorbance of light frequency/wavelength from the LED. This signal is recorded with a DAQ frequency of 20 Hz. A signal corresponding to the current through the electrodes 58, 31 is also recorded with a DAQ frequency of 20 Hz. The signals of current and absorbance are used to determine the amount of analytes in the sample solution, based on migration speed and distance of the analytes, during electrophoresis. Amounts of analytes are calculated in accordance with practices known in the art.

The cross piece 20, BGE chamber 33 and capillary 30 are then flushed again with BGE from the BGE pump unit 44. The auxiliary waste vial 48 is then refilled with BGE using the auxiliary BGE pump unit 46 at approximately 0.3 mL/min to ready the device for the next electrophoresis cycle.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A filter system for filtering particles from an inlet flow of fluid to an instrument for analysis of the fluid, the filter system comprising: a hydrocyclone for separating a feed stream into an overflow stream and an underflow stream; and an H-filter for performing filtration on the overflow stream by diffusion to form a purified stream.

2. The filter system of claim 1 , further comprising a reservoir located downstream of the hydrocyclone for receiving the overflow stream to transition the overflow stream to a laminar flow regime.

3. The filter system of claim 1 or claim 2, wherein the purified stream is delivered to an additional reservoir that is located downstream of the H-filter.

4. The filter system of claim 3, wherein a pump unit is positioned downstream of the additional reservoir to deliver fluid flow from the additional reservoir to the instrument.

5. The filter system of claim 4, wherein the pump unit is a peristaltic pump.

6. The filter system of any one of the preceding claims, wherein the hydrocyclone is effective to remove particles greater than 300 pm in size.

7. The filter system of any one of the preceding claims, wherein the H-filter is effective to produce a purified stream that is substantially free of particles greater than 1.5 pm in size.

8. The filter system of any one of the preceding claims, wherein any particulate matter remaining in the purified stream is less than 1.5 pm in size.

9. The filter system of any one of the preceding claims, wherein the instrument is a portable capillary electrophoresis instrument.

10. A portable capillary electrophoresis system comprising a portable capillary electrophoresis instrument and the filter system of any one of claims 1 to 9.

11. The portable capillary electrophoresis system of claim 10, wherein the portable capillary electrophoresis instrument comprises an analyser for analysing analytes in a sample solution from the purified stream.

12. The portable capillary electrophoresis system of claim 11 , wherein the analyser comprises a separation capillary for separating analytes in the sample solution.

13. The portable capillary electrophoresis system of claim 12, wherein the analyser comprises a detector for detecting the presence of analytes in the sample solution.

14. The portable capillary electrophoresis system of claim 13, wherein the portable capillary electrophoresis instrument comprises a pump that is configured to deliver flow of a sample solution from the purified stream to the analyser and a waste outlet.

15. The portable capillary electrophoresis system of claim 14, wherein the portable capillary electrophoresis instrument comprises a valve unit for controlling the direction of flow of the sample solution to either the analyser or the waste outlet.

16. The portable capillary electrophoresis system of claim 15, wherein the portable capillary electrophoresis instrument comprises a sensor for measuring a signal from the analyser corresponding to amounts of analytes in the sample solution.

17. A method of using the filter system of the portable capillary electrophoresis system of any one of claims 9-16, the method comprising the steps of:

- separating a feed stream of the fluid using the hydrocyclone in a first separation step into an overflow stream and an underflow stream; and

- subjecting the overflow stream to particle filtration using the H-filter to form a purified stream.

18. A method of using the filter system of any one of claims 1 -8, the method comprising the steps of:

19. A method for the detection of analytes in an environmental water source using the portable capillary electrophoresis instrument in the portable capillary electrophoresis system of claim 16, the method comprising:

- operating the pump to deliver sample solution to the waste outlet;

20. A method for filtering particles from a fluid, the method comprising: applying a centripetal force to the fluid to separate a feed stream of the fluid into an overflow stream and an underflow stream; and subjecting the overflow stream to filtration by diffusion to form a purified stream.

21. The method of claim 20, further comprising the step of transitioning the overflow stream to a laminar flow regime prior to subjecting it to filtration by diffusion.

22. A method for filtering particles from a fluid, the method comprising:

- separating a feed stream of the fluid using a hydrocyclone in a first separation step into an overflow stream and an underflow stream; and - subjecting the overflow stream to particle filtration using an H-filter to form a purified stream.

23. The method of claim 17, 18 or 22, further comprising the step of directing the overflow stream to a reservoir located downstream of the hydrocyclone and transitioning the overflow stream to a laminar flow regime prior to filtration in the H-filter.