Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/04—Devices for withdrawing samples in the solid state, e.g. by cutting
  • G01N1/08—Devices for withdrawing samples in the solid state, e.g. by cutting involving an extracting tool, e.g. core bit
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/04—Devices for withdrawing samples in the solid state, e.g. by cutting
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/0091—Powders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L2300/00—Additional constructional details
  • B01L2300/08—Geometry, shape and general structure
  • B01L2300/0832—Geometry, shape and general structure cylindrical, tube shaped
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/10—Devices for withdrawing samples in the liquid or fluent state
  • G01N2001/1006—Dispersed solids

Definitions

• the components requiring blending are usually powders of different size, density, shape, and cohesiveness. Since such materials often display a considerable tendency to segregate, ultimate mixture homogeneity cannot be taken for granted; quite the opposite, unless the blending process is properly designed and controlled, the result is often a mixture with significant composition fluctuations throughout the powder bed [See, L.T. Fan, Y.-M. Chen, and F.S. Lai, Powder TechnoL, 61 (1990) 255. and M. Poux, P. Fayolle, J. Bertrand, D. Bridoux, and J. Bousquet, Powder TechnoL, 68 (1991) 213.]. Inhomogeneities in the powder blend can result in increased variability in the contents of potent components in tablets, leading not only to decreased therapeutic value but also to direct health risks due to toxicity in super-potent tablets.
• Characterization of mixtures in most industrial processes relies on taking and analyzing discrete samples. Parameters such as sample size (n), number of samples (N), and location of the sampling points can affect the measurement values. Guidelines for selecting the number of samples have been proposed based on theoretical random mixtures (i.e., >30) [Devore, J.L., Probability and Statistics for Engineering and the Sciences, Vol., Brooks/Cole Publishing Company, Monterey, 1982, p. 640] but optimal values of these parameters for real systems displaying incomplete mixing are often unknown.
• Thief samplers belong to two main classes: side sampling and end sampling.
• a typical side sampling probe has one or more cavities drilled or stamped in an inner cylinder enclosed by an outer rotating sleeve.
• the sleeve has holes that align with the cavities, allowing adjacent powder to flow into the cavities. Rotating the sleeve to its closed position traps the particles into the cavities.
• An end sampling thief has a single cavity at the end of the probe that can be remotely opened and closed. In both cases, the thief is introduced into the powder with its cavities closed. Once insertion is complete, the cavities are opened, allowing the powder to flow into them. The cavities are then closed, and thief is withdrawn, removing samples from the mixtures.
• Thief sampling is a rather laborious and cumbersome technique and is rarely practical to take more than 10 or 20 samples.
• the experimentally measured variance, ⁇ e 2 is actually a combination of the true variance resulting from the mixing process, ⁇ m 2 , the variance introduced by sampling error, ⁇ s 2 [Fan, L.T., et al., Powder TechnoL, 61 (1990) 255], and the variance resulting from analytical analysis, ⁇ a 2 , i.e.,
• Carley-Macauley and Donald [Carley-Macauly, K.W., et al., Chem. Eng. Sc , 17 (1961) 493] performed a comparison study between two types of side sampling probes.
• sand particles tended to run down the slit, causing errors greater than the conventional side sampling probe.
• This invention relates to an end-sampling thief probe and a method of using this probe.
• the probe is useful in extracting a sample with minimal disturbance.
• Performance of the thief probe of the invention (a) Minimum disturbances caused by insertion of the probe into particle bed (b) comparison of theoretical (---) and experimental (•, ⁇ , ⁇ ) results for 60 ⁇ m particles over 200 ⁇ m particle and (c) 200 ⁇ m particles over 60 ⁇ m particles.
• a thief probe comprising an outer hollow rod with a hollow conical tip attached at one end of the outer hollow rod and an inner hollow rod with a conical tip attached at one end of the inner hollow rod; said outer hollow rod having an inner diameter of about 1/4 in. to about 63/32 in. and an outer diameter of about 9/32 in. to about 2 in.; the hollow conical tip of the outer hollow rod having an aperture; the aperture of the hollow conical tip of the outer hollow rod being up to about 1/2 of the surface of the hollow conical tip; said inner hollow rod having an inner diameter of about 7/32 in.
• the hollow conical tip of the inner hollow rod having an aperture; the aperture of the hollow conical tip of the inner hollow rod being up to about 1/2 of the surface of the hollow conical tip; the outer hollow rod being shorter in length than the inner hollow rod by about 3 in.; the inner hollow rod being mounted in the outer hollow rod and rotatable about the axis of the inner and outer hollow rods; said inner and outer hollow rods being rotatable to an open position and a closed position; the open position being defined as the point where the apertures of the hollow conical tips of the inner and outer hollow rods are aligned so as to expose the cavity in the hollow conical tip of the inner hollow rod; and the closed position is the point where the inner and outer apertures of the inner and outer hollow conical tips are aligned so as not to expose the cavity in the hollow conical tip of the inner hollow rod.
• An embodiment of the invention is a thief probe comprising an outer hollow rod with a hollow conical tip attached at one end of the outer hollow rod and an inner hollow rod with a inner hollow conical tip attached at one end of the inner hollow rod; said outer hollow rod having an inner diameter of about 1/4 in. to about 63/32 in. and an outer diameter of about 9/32 in. to about 2 in.; the hollow conical tip of the outer hollow rod having an aperture; the aperture of the hollow conical tip of the outer hollow rod being up to about 1/2 of the surface of the hollow conical tip; said inner hollow rod having an inner diameter of about 7/32 in. to about 61/32 and an outer diameter of about 8/32 in.
• the hollow conical tip of the inner hollow rod having an aperture; the aperture of the hollow conical tip of the inner hollow rod being up to about 1/2 of the surface of the hollow conical tip; the outer hollow rod being shorter in length than the inner hollow rod by about 3 in.; an inner solid rod having a diameter of 6/32 in.
• said inner solid rod being mounted in the inner hollow rod and being adjustable in height, so as to define the size of the cavity of the inner hollow rod;
• the inner hollow rod with the mounted inner solid hollow rod being mounted in the outer hollow rod and rotatable about the axis of the inner and outer hollow rods;
• said inner and outer hollow rods being rotatable to an open position and a closed position; the open position being defined as the point where the apertures of the hollow conical tips of the inner and outer hollow rods are aligned so as to expose the cavity in the hollow conical tip of the inner hollow rod; and the closed position is the point where the inner and outer apertures of the inner and outer hollow conical tips are aligned so as not to expose the cavity in the hollow conical tip of the inner hollow rod.
• An embodiment of the invention is a thief probe comprising an outer hollow rod with a hollow conical tip attached at one end of the outer hollow rod and an inner hollow rod with a inner hollow conical tip attached at one end of the inner hollow rod; said outer hollow rod having an inner diameter of about 7/16 in. and an outer diameter of about 8/16 in.; the hollow conical tip of the outer hollow rod having an aperture; the aperture of the hollow conical tip of the outer hollow rod being up to about 1/2 of the surface of the hollow conical tip; said inner hollow rod having an inner diameter of about 11/32 in.
• the hollow conical tip of the inner hollow rod having an aperture; the aperture of the hollow conical tip of the inner hollow rod being up to about 1/2 of the surface of the hollow conical tip; the outer hollow rod being shorter in length than the inner hollow rod by about 3 in.; the inner hollow rod being mounted in the outer hollow rod and rotatable about the axis of the inner and outer hollow rods; said inner and outer hollow rods being rotatable to an open position and a closed position; the open position being defined as the point where the apertures of the hollow conical tips of the inner and outer hollow rods are aligned so as to expose the cavity in the hollow conical tip of the inner hollow rod; and the closed position is the point where the inner and outer apertures of the inner and outer hollow conical tips are aligned so as not to expose the cavity in the hollow conical tip of the inner hollow rod.
• a thief probe as described above, wherein the non-reactive material is selected from the group consisting of: aluminum, copper, steel and bronze.
• a thief probe as described above, wherein the non-reactive material is aluminum.
• a method for improved ending-sampling of a solid mixture comprising the steps of:
• the Globe Pharma thief probe has a side-sampling design as described above.
• the thief probe has two cavities, and removable dies fit into the cavities in order to control sample volume.
• the lower cavity contained a 0.2 ml die while the upper one was filled with a solid die.
• insertion of the Globe Pharma thief creates significant disturbances in the mixture (Fig. 7a). Particles from upper layers are dragged deeply into lower layers as the thief penetrates the granular bed. Once the thief is opened, the sample flowing into the thief will be contaminated with particles from positions along the path of insertion and will not necessarily reflect the true composition of the system at the sampling location before the thief was inserted.
• Fig. 7b and 7c Data comparing actual sample composition to theoretical composition expected from sampling location are shown in Fig. 7b and 7c for the Globe Pharma probe.
• the graphs show the percentage of the particles in the top layer that are contained in each sample.
• Figure 7b shows results obtained for 60 ⁇ beads on top of 200 ⁇ beads
• Figure 7c corresponds to 200 ⁇ beads on top of 60 ⁇ beads. If the probe accurately samples the desired location, the percentage of particles from the top layer should be zero once the opening crosses the interface between the top and bottom layers. However, as shown in Figs. 7b and 7c, large sampling errors are incurred, and the samples are composed entirely of particles from the top layer regardless of sampling location.
• the second thief tested is an end- sampling thief.
• the thief probe consists of two concentric hollow pipes, both ending in a pointed cone (an inner and an outer rod each having a hollow conical tip) (Fig. 8a). Half of each cone has been removed (each hollow conical tip having an aperture) so that the sampling cavity of the thief can be set to an open position (when the aperture of the inner and outer hollow rods align so as to expose the cavity) and closed position (when the aperture of the inner and outer hollow rods align so as not to expose the cavity, the apertures are at 180 degrees to each other) by rotating the inner hollow pipe (inner hollow rod).
• the outer hollow rod having an inner diameter of about 7/16 in. and an outer diameter of about 8/16 in.
• the thief can be constructed from any material which will not react with the samples being taken. Examples of such materials are aluminium, copper, steel and bronze. The material used to construct the thief used in the experiments described is aluminium. Additionally, it should be noted that the clearance between the inner and outer hollow rods should be minimized. However, if the clearance allows for particles to flow into the thief when in the closed position, a gasket can be employed to fill in this clearance and prevent this from occurring.
• the thief is used as follows: the thief is inserted in the closed position into a vessel containing a powder mixture to be sampled to the desired depth, the inner hollow rod is rotated to the open position exposing the cavity of the inner hollow conical tip, the thief is inserted further into the powder bed, the inner hollow rod is rotated to the closed position closing the cavity of the inner hollow conical tip, and then the thief containing a sample of the powder mixture is removed from the mixture. Samples of consistent size were obtained by controlling the depth of insertion after the cavity of the thief probe is opened, as well as the diameter of the thief probe. Additionally, a stopper may be used to set the sample size, as shown in Fig. 4-6. As shown in Fig.
• the pointed cone design of this thief introduces much smaller disturbances of the granular structure than the previous device. Disturbances are minimal near the tip of the probe, where the sampling takes place. Quantitative comparison of theoretical and experimental sampling data is shown in Fig. 8b for 60 ⁇ particles on top of 200 ⁇ particles, and in Fig. 8c for 200 ⁇ particles on top of 60 ⁇ particles. The data indicates that the thief probe of the invention performs much better than the Globe Pharma thief probe.

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• Sampling And Sample Adjustment (AREA)

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• 1997
  • 1997-10-21 WO PCT/US1997/019062 patent/WO1998018558A1/en not_active Application Discontinuation
  • 1997-10-21 JP JP10520569A patent/JP2001503147A/ja active Pending
  • 1997-10-21 EP EP97913724A patent/EP0934117A1/en not_active Withdrawn
  • 1997-10-21 CA CA002268849A patent/CA2268849A1/en not_active Abandoned

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