WO1993017321A1 - Dispositif de preconcentration et d'absorption atomique electrothermique - Google Patents

Dispositif de preconcentration et d'absorption atomique electrothermique Download PDF

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Publication number
WO1993017321A1
WO1993017321A1 PCT/AU1993/000079 AU9300079W WO9317321A1 WO 1993017321 A1 WO1993017321 A1 WO 1993017321A1 AU 9300079 W AU9300079 W AU 9300079W WO 9317321 A1 WO9317321 A1 WO 9317321A1
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WO
WIPO (PCT)
Prior art keywords
sample
electrodeposited
tube
atomic absorption
metal
Prior art date
Application number
PCT/AU1993/000079
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English (en)
Inventor
Jaroslav Petr Matousek
Harry Kipton James Powell
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Unisearch Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of WO1993017321A1 publication Critical patent/WO1993017321A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G01N21/74—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited using flameless atomising, e.g. graphite furnaces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/40—Concentrating samples

Definitions

  • This invention relates to a method and apparatus for the determination by electrothermal atomic absorption spectrophotometry of a variety of elements which are affected by severe matrix interferences, in particular to a method and apparatus whereby matrix interferences are substantially eliminated through the removal of the matrix prior to atomisation of a sample.
  • This invention also relates to a method for the determination by electrothermal atomic absorption spectrophotometry of a variety of elements, in particular to a method whereby a metal is electrodeposited onto the inside surface of a graphite tube, disposed within the furnace assembly, prior to or concurrent with the introduction of a sample for analysis.
  • a concentrate Once a concentrate is obtained, it may be analysed using a variety of instrumental techniques, including neutron activation, optical emission spectrometry, mass spectrometry and flame and electrothermal atomic absorption spectrophotometry.
  • instrumental techniques including neutron activation, optical emission spectrometry, mass spectrometry and flame and electrothermal atomic absorption spectrophotometry.
  • Electrothermal (graphite furnace) atomic absorption spectrophotometry is one instrumental technique which has sufficient sensitivity to permit the measurement of trace elements in sea water without a preconcentration step.
  • the matrix introduces significant background absorbance problems since most elements are covolatilised with the bulk of the matrix. Accordingly, the use of direct determination by this technique has achieved only limited success.
  • chemical modifiers have been used leading to the development of methods for the analysis of several elements. These elements, for example iron, have high atomisation temperatures and must be present in relatively high concentrations. Thus, typically under optimum conditions, the detection, limits for heavy metals in sea water are generally above l ⁇ gL ⁇ .
  • Matousek and Grey described a method for the analysis of an element that is capable of being electrodeposited onto a graphite surface from a sample which includes the element in low aqueous concentration and a matrix that interferes in the atomic absorption spectrophotometric determination of that element comprising: a) placing an aliquot of the sample within the inside of a pyrolytic graphite tube disposed in the furnace assembly of an atomic absorption spectrophotometer; b) positioning an anode within the pyrolytic graphite tube so as to be in contact with the sample therein; c) subjecting the sample to electrolysis by applying a potential to the anode and the pyrolytic graphite tube as the cathode so as to electrodeposit the element in the sample onto the inner surface of the pyrolytic graphite tube; d) removing the electrolysed solution; e
  • this invention consists in a method for the analysis of an element that is capable of being electrodeposited onto a graphite surface from a 20 sample which includes the element in low aqueous concentration and a matrix that interferes in the atomic absorption spectrophotometric determination of that element comprising: a) placing an aliquot of the sample within the inside of 25 a pyrolytic graphite tube disposed in the furnace assembly of an atomic absorption spectrophotometer using an electrically conductive capillary tube which is maintained in electrical contact with the sample therein; 30 b) subjecting the sample to electrolysis by applying a potential to the capillary tube as the anode and the pyrolytic graphite tube as the cathode so as to electrodeposit the element in the sample onto the inner surface of the pyrolytic graphite tube; 3.5 c) removing the electrolysed solution; d) washing the electrodeposited element to remove the matrix; and e) subjecting the washed electrodeposited element to electrothermal
  • this invention further consists in an automatic sample loader for use in the analysis of an element that is capable of being electrodeposited onto a graphite surface from a sample which includes the element in low aqueous concentration and a matrix that interferes in the atomic absorption spectrophotometric determination of that element, said sample loader having an electrically conductive capillary tube adapted to hold an aliquot of a sample or other solution, the capillary tube being adapted to be positioned automatically within the opening of a pyrolytic graphite tube, such that a sample discharged into the pyrolytic graphite tube from the capillary tube will remain in electrical contact with said capillary tube and wherein the capillary tube is provided with a means to connect it to a source of potential to form it into an anode.
  • this invention further consists in an apparatus for the analysis of an element that is capable of being electrodeposited onto a graphite surface from a sample which includes the element in low aqueous concentration and a matrix that interferes in the atomic absorption spectrophotometric determination of that element
  • an atomic absorption spectrometer incorporating a graphite furnace assembly, an automatic sample loader of the said aspect; a pyrolytic graphite tube disposed within the furnace assembly of the atomic absorption spectrophotometer so as to permit the drying, if required, ashing and atomisation of a sample contained therein and having an opening adapted to permit the entry of the capillary tube therein; and a source of potential connected to the capillary tube so as to form an anode and to the pyrolytic graphite tube so as to form a cathode.
  • the present inventors sought to provide an improved method whereby the pyrolytic graphite tubes are protected and are thus capable of being used for a substantially larger number of samples.
  • the protection of pyrolytic graphite tubes used in these analyses has now been achieved surprisingly by firstly electrodepositing a protective metal onto the inside surface of the graphite tube and then depositing the analyte from the sample for analysis on the protective metal deposit.
  • the deposition of the analyte from the sample may be the electrodeposition Of the first aspect method or a deposition of an analyte in an aqueous sample followed by evaporation of the sample to dryness.
  • protective metal and the analyte from the sample may also be codeposited or a portion of the protective metal electrodeposited followed by a codeposition of protective metal and analyte from the sample.
  • salts of metals such as palladium may be beneficially used as chemical modifiers in electrothermal atomic absorption spectrophotometry.
  • this invention further consists in a method for the analysis of an element that is capable of being determined using electrothermal atomic absorption spectrophotometry comprising (a) electrodepositing a metal onto the inside of a pyrolytic graphite tube either prior to the introduction of a sample containing the element or concurrently with deposition of the element from the sample into said tube;
  • a volume of acid typically about 40 ⁇ L for a 25 * JL sample is added to the electrodeposited metal and analyte and electrolysed, typically for about 60 seconds. The residual solution is then removed. It has been found that 3% nitric acid is a suitable medium and elements such as lead, cadmium, copper and manganese may be treated in this way. The previously described procedure of drying, ashing and atomisation is then carried out.
  • this invention still further consists in an improvement to the technique of analysis by hydride generation, the improvement comprising electrodepositing a hydride collecting metal onto the inside surface of a graphite tube prior to introducing the hydride into the tube.
  • the method of the first aspect of this invention represents a substantial advance over the prior art in that electrodeposition takes place wholly on the inner surface of a pyrolytic graphite tube, substantially all of an element in a relatively small sample may be deposited, the deposited element is washed free of interfering matrix and the pyrolytic graphite tube is retained within the furnace assembly of an atomic absorption spectrophotometer.
  • the use of relatively high voltage during electrodeposition also permits rapid deposition of substantially all of an element in a sample.
  • using the apparatus of this invention allows the method to be used for rapid, repetitive analysis of many samples.
  • samples to which this method may be applied comprise particularly environmental samples, such as ground waters, sea water and the like, and biological fluids, such as serum. Whilst these latter samples may be aqueous in nature, desirably protein and other interfering organic materials in the matrix should be removed. This is required as proteins, for example, interfere with the electrodeposition procedure-.
  • a sample can be deposited following the electro deposition of the protective metal, reagents added, the residue dried and ashed and then redissolved prior to electrodeposition using the present invention.
  • the volume of sample to be deposited in the pyrolytic graphite tube will usually be about 5-100 ⁇ L, typically about 50 ⁇ L.
  • the sample would include an electrolyte at a concentration of at least 0.05M as NaCl and a buffer, such as acetate in a concentration of about 0.02M.
  • a proportion of the sample may be lost through the orifice owing to capillary action.
  • the present inventors have found that one way of controlling this is to incorporate a small amount of surfactant in the sample.
  • An example of a suitable surfactant is Triton X-100 which is incorporated in a concentration of about 0.005% w/v.
  • a potential is then applied to the capillary tube as anode and the graphite tube as cathode.
  • the potential should be constant, typically about 3-6 volts. Alternatively, constant current may be used.
  • the pyrolytic graphite tube may be coated with pyrolytic graphite or may be totally pyrolytic graphite for improved lifetime.
  • a sample aliquot is taken up into the capillary tube of the automatic sample loader, which then functions to place the sample aliquot into the pyrolytic graphite tube.
  • the capillary tube enters the pyrolytic graphite tube, discharges a sample therein and then remains positioned within the pyrolytic graphite tube to an extent sufficient such that the capillary tube remains in electrical contact with a sample aliquot throughout electrodeposition.
  • the capillary tube must be electrically conductive and desirably should be unreactive towards a sample. Accordingly, a capillary tube may be formed from materials such as platinum and platinum/iridium alloy.
  • the electrolysed solution is removed and the deposited element is washed to remove interfering matrix.
  • the apparatus of the invention accomplishes this step through withdrawal of the capillary tube from the pyrolytic graphite tube, collection of a washing medium, discharge of the washing medium into the pyrolytic graphite tube where the element has been electrodeposited, and then withdrawal of the washing fluid in the pyrolytic graphite tube into the capillary tube by suction.
  • a further sample aliquot may be discharged directly into the pyrolytic graphite tube containing the previously electrodeposited element without any intervening washing. Washing may then occur following the electrodeposition of the second sample aliquot. In either case, it will be evident that the amount of electrodeposited element may be increased as required through the repeated electrodeposition of elements from a plurality of sample aliquots. In effect, this procedure will serve as an efficient means of enhancing concentration, thereby improving the limit of detection.
  • a matrix can be removed by washing with lOO ⁇ L distilled water. Using this procedure, the background absorption by the matrix will be reduced to approximately 1% of-the original value.
  • ⁇ fiemical modifier may be applied to the electrodeposited element in an amount of about 50 ⁇ L. It may be either left ⁇ I&wthe pyrolytic graphite tube and dried prior to atomisation, or removed after a preset time.
  • the electrodeposited element is then ashed and atomised-as graphite furnace atomic- absorption speetrogfi ⁇ tometry.
  • a wide range ⁇ S-elements may be analysed using this method, including copper, lead, cadmium, zinc, manganese, nickel, chromium, cobalt, silver, gold, mercury, -- palladium ? -platinum, antimony, tin, bismuth, iridium, " arsenic, " selenium and gallium.
  • a suitable apparatus for this purpose is-a GBC PAL 2000 programmable Autoloader modified by using an electrically conductive sampling capillary. This GBC unit may be reprogrammed to perform sample loading, electrolysis, solution removal and several washing and chemical treatment steps as required.
  • the following general protocols may be followed:- (a) electrodeposition of a metal onto the graphite surface followed by electrodeposition of the analyte from the sample; (b) electrodeposition of a metal onto the graphite surface followed by the deposition of the aqueous sample and subsequent drying;
  • wash cycles may be used between or following particular deposits as required.
  • a variety of metals may be deposited including palladium, platinum, ruthenium, rhodium, iridium, osmium, gold and the like.
  • the metal to be deposited will be selected on the basis of its volatility and in some cases its functionality as a modifier. Furthermore, to minimize furnace contamination the selected metal will desirably be one which is not frequently analyzed.
  • the metals will be in aqueous solution in a concentration in the range of the order of lOppm-lOOppm. A volume of this solution in the range of about 25-75 ⁇ L may be deposited in the graphite tube.
  • electrodeposition of the metal occurs in about 60 seconds using 5.2V with the current in the range of 15-30mA. It has been found that when palladium is the electrodeposited metal and lead is to be analyzed in the sample in a sodium chloride matrix, a graphite tube may be fired at least 170 times with no microscopically visible signs of tube deterioration. This is in marked contrast to the use of the first aspect method where after 70-80 firings, the pyrolytic coating was extensively fractured and raised.
  • the concentration of metal required is substantially less than modifier metal salt solutions used in the prior art. Typically only 0.5-5% as much metal is required.
  • electrodeposition of a metal as a protective agent to prevent the formation of carbides of refractory elements such as vanadium, chromium, molybdenum and the like.
  • semi-metals and non-metals may be determined by direct formation of a hydride in the graphite tube. In this procedure, following electrodeposition of a metal, the sample is electrolyzed in situ to generate nascent hydrogen at the cathode which then reacts with analyte to form hydride. It is also possible to generate nascent oxygen at the anode which is then used to oxidize organic matter using a TiOumble coated electrode.
  • Figure 1 is a schematic representation of an Autoloader of the invention
  • Figures 2, 3 and 4 each graphically represents the output of an electrothermal atomic absorption spectrophotometric analysis of lead in aqueous samples.
  • this apparatus comprises a pyrolytic graphite tube 10, shown in cross-section, an opening 11 therein with the platinum/iridium capillary sampling tube 13 disposed therein.
  • the platinum/iridium capillary tube 13 and the pyrolytic graphite tube 10 are connected to a constant voltage or current supply 16 with the platinum/iridium capillary tube as anode and the pyrolytic graphite tube as cathode
  • a teflon spacer 12 is disposed in the opening 11 with the capillary tube 13 passing therethrough.
  • the spacer serves to both seal the opening and insulate the capillary tube 13 from the graphite tube 10.
  • capillary tube 13 is connected to plastic tube 17 which in turn is in fluid communication with a solution.
  • An arm 14 permits the capillary sample tube 13 to be moved into opening 11 of the pyrolytic graphite tube and away to withdraw a sample, wash solution or the like.
  • the method of analysis used was the method of the first aspect, i.e., there was no electrodeposition of a protective metal.
  • the sample solution consisted of 0.02ppm Pb in 0.5MNaCl and 25 ⁇ L was electrodeposited.
  • the sample contained 0.5ng Pb.
  • the method of analysis used was conventional electrothermal atomic absorption spectrophotometric and the sample consisted of an aqueous solution of 5 ⁇ L of 0.lppm Pb. Thus the sample contained 0.5ng Pb.
  • Fig. 2 the method of analysis used was the method of the first aspect, i.e., there was no electrodeposition of a protective metal.
  • the sample solution consisted of 0.02ppm Pb in 0.5MNaCl and 25 ⁇ L was electrodeposited.
  • the sample contained 0.5ng Pb.
  • the method of analysis used was conventional electrothermal atomic absorption spectrophotometric and the sample consisted of an aqueous solution of 5 ⁇ L of 0.lppm Pb.
  • the sample
  • the method of analysis used is one of the protocols of the present invention whereby 25 ⁇ L of lOppm Pd(N0 3 ) 2 was firstly electrodeposited followed by electrodeposition of 25 ⁇ L of 0.02ppm Pb in 0.5MNaCl.
  • the sample contained 0.5ng lead.

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Abstract

Procédé et appareil de détermination spectrophotométrique par absorption atomique électrothermique de divers éléments influencés par des perturbations matricielles sévères. Selon un de ses aspects, le procédé se fonde sur le dépôt électrolytique direct de l'élément à analyser dans la surface interne d'un tube en graphite placé dans l'ensemble à four. Selon un second aspect du procédé, on effectue, avant le dépôt de l'élément à analyser, ou en même temps que celui-ci, le dépôt électrolytique du métal protecteur de la surface interne du tube en graphite. L'appareil précité comporte: un spectromètre d'absorption atomique comprenant un ensemble à four en graphite; un enfourneur (14, 15) automatique d'échantillons possédant un tube capillaire électroconducteur (13) adapté pour contenir une aliquote d'un échantillon ou d'une autre solution; un tube en graphite pyrolytique (10) placé à l'intérieur de l'ensemble à four du spectrophotomètre d'absorption atomique de manière à permettre, le cas échéant, le séchage, le cendrage et l'atomisation d'un échantillon contenu dans ledit tube, et doté d'un orifice (11) adapté pour permettre l'introduction du tube capillaire (13); et une source de potentiel (16) reliée au tube capillaire (13) de manière à former une anode, et au tube en graphite pyrolytique (10) de manière à former une cathode.
PCT/AU1993/000079 1992-02-25 1993-02-25 Dispositif de preconcentration et d'absorption atomique electrothermique WO1993017321A1 (fr)

Applications Claiming Priority (4)

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AUPL106992 1992-02-25
AUPL1069 1992-02-25
AUPL482592 1992-09-18
AUPL4825 1992-09-18

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19603643A1 (de) * 1996-02-01 1997-08-07 Bodenseewerk Perkin Elmer Co Elektrothermische Atomisierungseinrichtung für die analytische Spektrometrie
CZ302757B6 (cs) * 2005-12-08 2011-10-19 Ústav analytické chemie AV CR, v.v.i. Zpusob prekoncentrace bizmutu pro jeho stanovení metodou atomové absorpcní spektrometrie a atomizátor pro prekoncentraci bizmutu
CN106124437A (zh) * 2016-08-18 2016-11-16 浙江华才检测技术有限公司 一种直接进样快速测定乳制品中铬含量的方法
WO2017070472A1 (fr) 2015-10-21 2017-04-27 The United States Of America, As Represented By The Secretary, Department Of Health And Human Services Adnc à codons optimisés pour une atp7a de taille réduite, et utilisation pour le traitement de troubles du transport du cuivre

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DE2504179A1 (de) * 1975-02-01 1976-08-05 Bbc Brown Boveri & Cie Werkstoff fuer wasserstoffhaltige atmosphaere
GB2066981A (en) * 1979-11-12 1981-07-15 Bodenseewerk Perkin Elmer Co Introduction of sample material into a graphite tube in atomic absorption spectroscopy
GB2071314A (en) * 1980-03-08 1981-09-16 Bodenseewerk Perkin Elmer Co Graphite tube for atomic absorption spectroscopy
GB2071845A (en) * 1980-03-14 1981-09-23 Bodenseewerk Perkin Elmer Co Atomic absorption spectroscopy
EP0261296A1 (fr) * 1986-09-25 1988-03-30 Laude, Lucien Diégo Appareillage pour le dépôt électrolytique ponctuel assisté par laser de métaux sur des solides
EP0296480A2 (fr) * 1987-06-19 1988-12-28 The Perkin-Elmer Corporation Procédé et dispositif d'atomisation électrothermique d'échantillons
EP0477541B1 (fr) * 1990-08-30 1997-03-05 Waters Investments Limited Appareil pour recueillir sur une membrane des fractions isolées par électrophorèse capillaire

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Publication number Priority date Publication date Assignee Title
DE2504179A1 (de) * 1975-02-01 1976-08-05 Bbc Brown Boveri & Cie Werkstoff fuer wasserstoffhaltige atmosphaere
GB2066981A (en) * 1979-11-12 1981-07-15 Bodenseewerk Perkin Elmer Co Introduction of sample material into a graphite tube in atomic absorption spectroscopy
GB2071314A (en) * 1980-03-08 1981-09-16 Bodenseewerk Perkin Elmer Co Graphite tube for atomic absorption spectroscopy
GB2071845A (en) * 1980-03-14 1981-09-23 Bodenseewerk Perkin Elmer Co Atomic absorption spectroscopy
EP0261296A1 (fr) * 1986-09-25 1988-03-30 Laude, Lucien Diégo Appareillage pour le dépôt électrolytique ponctuel assisté par laser de métaux sur des solides
EP0296480A2 (fr) * 1987-06-19 1988-12-28 The Perkin-Elmer Corporation Procédé et dispositif d'atomisation électrothermique d'échantillons
EP0477541B1 (fr) * 1990-08-30 1997-03-05 Waters Investments Limited Appareil pour recueillir sur une membrane des fractions isolées par électrophorèse capillaire

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Title
ANALYTICAL CHEMISTRY, Vol. 49, No. 13, Issued November 1977 (Washington), G.E. BATLEY & J.P. MATOUSEK, "Determination of Heavy Metals in Seawater...", pages 2031-2034. *
ANALYTICAL CHEMISTRY, Vol. 52, No. 11, Issued September 1980 (Washington), G.E. BATLEY & J.P. MATOUSEK, "Determination of Chromium Speciation in Natural Waters...", pages 1570-1574. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5866431A (en) * 1996-01-02 1999-02-02 Bodenseewerk Perkin-Elmer Gmbh Electrothermal atomization means for analytical spectrometry
DE19603643A1 (de) * 1996-02-01 1997-08-07 Bodenseewerk Perkin Elmer Co Elektrothermische Atomisierungseinrichtung für die analytische Spektrometrie
AU729400B2 (en) * 1996-02-01 2001-02-01 Perkin Elmer Bodenseewerk Zweigniederlassung Der Berthold Gmbh & Co. Kg Electrothermal atomization means for analytical spectrometry
CZ302757B6 (cs) * 2005-12-08 2011-10-19 Ústav analytické chemie AV CR, v.v.i. Zpusob prekoncentrace bizmutu pro jeho stanovení metodou atomové absorpcní spektrometrie a atomizátor pro prekoncentraci bizmutu
WO2017070472A1 (fr) 2015-10-21 2017-04-27 The United States Of America, As Represented By The Secretary, Department Of Health And Human Services Adnc à codons optimisés pour une atp7a de taille réduite, et utilisation pour le traitement de troubles du transport du cuivre
CN106124437A (zh) * 2016-08-18 2016-11-16 浙江华才检测技术有限公司 一种直接进样快速测定乳制品中铬含量的方法
CN106124437B (zh) * 2016-08-18 2019-01-18 浙江华才检测技术有限公司 一种直接进样快速测定乳制品中铬含量的方法

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