CLINICAL CHEMISTRY
Flame, Flameless, and Plasma Spectroscopy
Nancy W.Alcock University of Texas Medical Branch, Department of Preventive Medicine and Community Health, 700 The Strand, Route JO9. Galueston, Texas 77555-1009
INTRODUCTION AND SCOPE Flame emission photometry, flame atomic absorption s ectrophotometry (FAAS), and gra hite furnace atomic
atsorption spectrophotometry ( G F d S ) or electrothermal vaporization (ETV) atomic absorption are well established analytical techniques for the measurement of individual metals in the clinical laboratory. Introduction of instrumentation in which inductively coupled plasma atomic emission spectrophotometry (ICPAES) could be applied over a broad spectrum of wavelengths provided the first simultaneous multielement technique which was sufficiently sensitive to measure some of the trace metals important to the clinical chemist. Although applied extensively, limitations of ICPAES for trace metal analyses in biological materials include lack of sensitivity required for elements such as chromium and spectral interferences inherent in emission. The development of ICP as a source of metal ions to he introduced into a quadrupole mass spectrometer and subsequent analysis on the basis of massicharge ratio provided anextremely sensitive multielement technique (ICPMS), with detection limits less than 1 ppb for most elements, and the unique capability of detecting all isotopes of the elements. This review summarizes recent developments in FAAS, GFAAS,ICPAES,andICPMS whichhavecurrentorpotential application to the field of clinical chemistry. Flame emission photometry, oncethe gold standard for determinationof alkali metals in serum and urine, has been replaced by either ionselective electrodes or FAAS and will not be discussed. Extensionof ICPMS toincludelaser ablationofsolidsamples and glow discharge will not he discussed. The source for the review is, with few exceptions a Chemical Abstracts search of titles and keywords of literature cited during the five-year period, November 1987 through October 1992. While the review is not intended to be all-inclusive, selected references from the 1645 reviewed give com rehensive coverage of the advances of each technique to Ate. Foreign journals are cited only where contributions are significant and for these the Chemical Abstract accession number is given. Limits of detection for most metals measured by the varioustechniques approximate0.2-1.0mgiL for FAAS, 0.1-lOpg/Lfor GFAAS, 1.0-100 @g/Lfor ICPAES, and 0.001-0.01 rgiL for ICPMS. Four atomic absorption s ectrophotometers are available in the United States, an CY world wide at least six are commercially available for both FAAS and GFAAS. While in general atomic absorption spectrophotometry is a singleelement technique, one commercial instrument has the capability for GFAAS analysis of four elements simultaneously. Little change has occurred in the basic design of instruments during the review period, but emphasis has been placed on improving methods for sample introduction. These include flow injection analysis atomic absorption (FIA) (SIS6),ultrasonic agitation of slurries where an autosampler is available ( S 4 , S6-S8), on-line coup@ to FAAS, GFAAS, ICPAES, and ICPMS with separation techniques such as HPLC or GC where metalloproteins such as metallothionein are being studied or metal speciation confirmed in the case of As, Se, and other metals as indicated in the tables. Speciation can be of importance in assessment of toxicity. Methods of background correction and errors identified with thesecontinueto bestudiedin AAS (S9). Inordertoimprove atomization efficiencies for elements measured by GFAAS, a newly designed Massmann-type stabilized temperature platform furnace has been tested (SIO).In contrasttoearlier furnaces heated from the ends, the new furnace is heated from the sides. The ultimate goal in GFAAS is to determine the absolute mass of an element from interference free measured absorbance.
NancyW.Alcock Isan A s s a h t e Pmfessa in the Department of Reventlve MBdiclne and Communky Health at the Unlversky of
Texas Medical Branch. Galveston. TX, where she Is the Director of the Nutrition Assessment Research Laboratory. She received her B.Sc. at the Universky of Tasmania and her Ph.D. at the Unberslty ' of London, England. Shelsa Dlplomateof the American Board of Cllnlcal Chemistry. Inc.. and a Fellow ofme National Academy of Clinical Biochemistry (FACB). and a Fellow of the New York Academy of Medicine. She is a member of the American Association for Cancer Research (AACR) and American Association for Cllnlcal Chemistry (AACC) and has served as chairperson of the Nutrition Division of AACC. She Is a member of the editorial board of Magnesium and Trace Metals. Her research interests are In trace metals In human nutrition. and In metals as chemotherapeutic agents. She has had extensive experience In flame emission spectrophotometry and atomic absorption spectrophotometry and, more recentiy. in inductively coupled plasma mass spectrometry. materialsbyAASwitha roto htrument,werepresented ( S I I ) . General m e t h d and?& application to the determination ofspecificelements wereextensivelyreviewed (S12). Arecentreviewofelementalanalysisofbodyfluidsandtissuea critically evaluates the application of electrothermal vaporization atomic absorption spectrophotometry (ETV) (SI3). The versatility of FAAS and GFAAS for the analysis of 16 elements normally present in foods is reviewed (S14). A review of pertinent references on chemical modification in ETV (S15)coveredthe period 1973-1989. Inafurther review (S16) platforms and modifiers used in ETV have been discueaed. Background correction in AAS was discussed a t length (5'9). While this is not a serious problem in FAAS, correction of the potentially large background in GFAAS is mandatory. In the review cited, four background correction systems-continuum source (Dd, Zeeman, simultaneous multielement atomic absorption continuum (SIMAAC) correction, and a system proposed by Smith-Hieftje (SI 7). (SH) correction-are analyzed. Errors inherent in each of the four systems are discussed and the advantages and disadvantages assessed. The system requirements and performance characteristics of ICPAES for simultaneous or rapid sequential multielement determinationofmajor,minor,and trace metalsarereviewed (S18). The versatility of this technique, which covers a wide range of concentrations for metals, is a significant advantage. The application of ICPAES and direct-current plasmaatomic emission spectrophotometry (DCPAES) to multielement analysis in biomedical and environmentalsamples is reviewed (S19). The featuresand IimitationsofICPAESarecompared with those of ICPMS in a concise but informative review (S20). A b w k (S21) on the applications of ICPMS covers a broad area. Basic principles and instrument performance are discussed a t length (S22). Important aspects of isotope ratio measurements (S23)and their application using stable isotope tracers in metabolic studies of individual elements is reviewed (S24). A more recent handbook has now been published (S2.5). Two publications review the application of ICPMS tobiologicalmaterials (S26,S27). Areviewofpractical aspects of ICPMS (S28) includes a discussion of mass discrimination, chemical and isobaric interferences, molecular and ionization interferences, and matrix effects. The list of interferences and discussion of isotope dilution and isotope ratiometbodology areofparticularvaluetotheuserof ICPMS.
REVIEWS AND BOOKS
GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROPHOTOMETRY
A description of equipment, and a discussion of principles and difficulties with multielement analysis of biological
The advances in graphite furnace atomic absorption spectrophotometry (GFAAS) or ETVAAS have been focused ANALYTICAL CHEMISTRY, VOL.
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Table 8-1. GFAAS Coupled with HPLC/GC/Other Separation Sources anal* sample type separation source
As,Se Cd, Zn, Cu
speciation kidney metallo-
thionein metallothionein: liver, kidney
Cd
Cr
Sn
urine extract,
HPLC HPLC
Table S-11. GFAAS Analysis of Selected Analytes analyte tissue, fluidhreatment ref
S38 s39
GC
AS
Au, Cu, Ag Bi
HPLC
540 541
anion exchange
S42 s43
Cd Cd Cd, Co, Cr,
s44
Cr
GFAAS-ICPAES, GFAAS-fluorinated, vaporization GC
Mn, Ni, Pb
speciation: mono-, di-, tributyltin
Fe
pr
F
1
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ANALYTICAL CHEMISTRY, VOL. 65, NO. 12, JUNE 15,
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Se Te T1, Ag, Au multielement
multielement multielement
ref
S52 s53 554
blood
s55
Pd modifier urine, Pt modifier
S56 s57 S58 542 s59
serum, protein precipitation saliva anion exchange pretreatment serum, automated probe for
elevated levels fluorination, ETV-ICPAES granulocytes
Mo
on mechanisms for reducing analysis time, which is a distinct disadvantage of the technique. Instruments ca able of ), simultaneous multielement analysis ( S ~ S S N mo8fication of temperature pro ams, utilization of a platform, and experimentation witrdifferent matrix modifiers have been tested (829,S35-S37). Altered platform and/or tube designs have also been developed. Newer instruments from one manufacturer have the newly designed tube with platform incorporated which is heated from the sides to produce more efficient atomization. A plication of an ultrasonic probe to an autosampler cup enabres the introduction of sample in the form of a slurry, thus minimizing sample preparation where this treatment is appropriate. In addition, sample pretreatment using microwave digestion has become increasingly opular, thus considerably reducing the total analysis time. se of different modifiers for specific elements where sensitivity is a problem has been advantageous. A review ( S I 4 of chemical modification in ETVAAS for the period 1973-1989 considers the analyte, matrix modifier, and sample matrix. Cou ling HPLC, GC anion exchange chromatographywith GFAA! h as enabled speciation of metals, and identification made of those bound to proteins such as metallothionein. ETV has also been the source of sample introduction into ICPAES and ICPMS. Some of these applications are summarized with references in Table S-I. A protot e multielement atomic absorption spectrophotometer w i g a continuum source and an echelle polychromator which was modified for wavelen h modulation was successfullyused for both flame and grap ite furnace analysis of several elements in biological materials (832). Although a two-channel atomic absorption system was described for increasing efficiency of inorganic analyses in environmental samples (S34),its application has not been widely reported. A multielement system using palladium chloride as matrix modifier was used to simultaneously measure Cd, Cr, Ni, and P b in urine (S45). Matrix matching for calibration curves was recommended. The potential use of continuum source AAS for multielement analysis and the advantages of palladium as a matrix modifier compared with ruthenium and reduction in analysis time to a proximately 1 min by introduction of the sample into a tu%e heated to 120 OC (5'35) appears to be promising. Analysis in less than 60 s when sample was introduced into a heated tube, with relative standard deviations of absorbance of less than 4% for several elements, was also reported (5'36). A miniature cup solid sampling technique was used for multielement analyses in biological materials (S3I). A number of elements were determined usin an autoprobe solid sampling GFAAS (S46). The accuracy an$ precision attained was comparable to that of other solid sampling techniques. Synthetic reference materials for use with sohd sampling techniques were prepared for eight elements (S47) and limits of detection ranged from 0.003 to 0.14pg/g. The accuracy and precision for the rapid analyses re uiring no sample preparation were adequate for routine app ication. Where autosamplers are used, modification of software mav_ Drovide simificant time reduction. e.g., rinsing time. Solid samples in the form of a slurry have been introduced into the graphite furnace after ultrasonic itation (S48850). An automated ultrasonic slurry s a m z r is available 484R
blood, urine, tissue serum, CSF urine, Pd vs Ni modifier
Ag A1
teeth speciation, HPLC Pt modifier urine, extraction of I complexes continuum source miniature cup solid sampling urine, serum, biological reference materials Rh, Pd, Pt modifiers
S60 S61 S62 S63
564 565 532 531 S66 533
commercially (S7).Appropriate calibration curves must be generated to assess matrix effects. Sample treatment with poly(tetrafluorethy1ene)was used as a fluorinating agent prior to slurry introduction into the graphite furnace and subsequent detection of molybdenum in food samples by ICPAES (S8).Lanthanum was determined in food and water samples using a tungsten-lined graphite tube (551). Good sensitivity with lower atomization temperature and negligible memory effects were achieved. Matrix interference was absent. This observation suggests investigation of response by other metals and experimentation with different tube linin s. Some specifictreatments for analysis of selected analytesy!l GFAAS are summarized in Table S-11.
FLAME ATOMIC ABSORPTION SPECTROPHOTOMETRY FAAS has been widely used for metal analyses in biological materials since its introduction in 1955. While it is a much more rapid technique than GFAAS, it re uires alarger sample volume and is much less sensitive. G F h S is 2-3 orders of magnitude more sensitive than FAA, depending upon the element. As with GFAAS, emphasis during the review period has been placed on methods of sample introduction and in some cases preconcentration of analyte, either on line or presampling. Table S-I11summarizes the various methods developed to improve a plicability of the flame technique. Flow injection systems (gI-S6, S72) combined with a slotted uartz tube (872,8781,a dialysis unit permitting large sam le Iilution (S5), on-line microwave digestion ( S I ) , varia le sample volume (S2), slurry nebulization (SS),and on-line precipitation of analyte and subsequent dissolution ( S I ) demonstrate the potential for both increased sensitivity of this technique and marked reduction in analysis time and hence increased sample throughput. A continuous flow system for sample introduction between two air plugs permitted analysis of 400 measurements per hour (5'67). HPLC pretreatment has been coupled with FAA for the measurement of Cd, Cu, and Zn in metallothionein (S69,570) and magnesium in chlorophyll (S73) with a thermospray nebulizer. Using a continuum source with echelle olychromator, multielement anal is in biological m a t e r i d by FAA has been reported (S32). g e - d r o p analysis proved successful for Cu, Co, and Ni following an extraction of pe perbush reference material digests into chloroform (S7I). #he use of very small volumes of the order of 50-100 pL by a one-drop technique is appropriate for many elements and worthy of testing when only small sample volume is available.
E
INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROPHOTOMETRY ICPAES, a multielement technique, is intermediate in sensitivity between GFAAS and FAAS. Advances during the
CLINICAL CHEMISTRY
Table 8-111. Modifications of Sample Introduction for FAA for Selected Analytes anal* sample type/treatment how introduced0 Ca Ca, Fe, Mg, Zn Ca, Mg, Zn, Fe, Cu, Pb, Cd, Sn Ca,Mg,Na,K
continuous flow system, sample between 2 air bubbles organic-based reference samples, tissues, slurry urine wine
Cd Cd, Co, Ni
metallothionein biological samples
Cd, Zn, Cu Cu, Co, Ni Cu, Pb, Cd, Au
metallothionein CHCl, extract, plant urine
Mg
chlorophyll
Na, K, Ca, Mg
serum
Na, K, Mg, Ca Fe, Zn, Pb, Cd Pb
milk
Pb, Cd, Cr, Zn, Cu
shellfish
Pb/Cu
sediment/urine
Zn
plasma, blood, cells
a
urine
FIA, on-line microwave
digestion on-line reversed-phase HPLC FIA with dialysis unit
anion exchange FIA, on-line coprecipitation without filtration precipitate dissolved HPLC 1drop FIA, slotted quartz tube atomizer HPLC, thermospray nebulizer FIA with variablevolume injector direct dispersion coprecipitation preconcentration with Bi(NO& microwave (closed) wet, dry ash comparison stainless steel cover and slotted quartz tube atomizer automated FIA
comments
ref
400 measurementdh
567
1-2 min/sample
54 568
large dilutions possible, 120-150 samples/h
55 569 51 570 571 572 573
52 574
575 576
3-9-fold increase in sensitivity
577 53
FIA, flow injection analysis.
review period have focused on reconcentration of sample prior to introduction into the ICE! Methods of concentration include on-line column treatment (S79-S83),precipitation of metals with ammonium pyrrolidinedithiocarbamate(S84), generation of hydride vapor for H (S85),Sn, and Ge (S86), and methyl borate vapor for B (&?7) have been described. Low-temperature digestion (150 OC) was used for retention of B (888). Chemical enhancement of signal by KC1 was demonstrated for Al(S89).A miniature cup was used for E T vaporization of sample prior to introduction into the ICP (S90). Solid powder samples deposited on Ag films were vaporized by capacitive discharge (S91). A low-volume vaporization chamber and a magnetic field normal to the electrical field improved plasmal sample interaction. A 60/ 40 mixture of Arlo2 carried the aerosol from the capacitive discharge plasma into the ICP. Recyclin nebulizers (S92, 593)utilizing the sample usually directef to a waste drain permitted continuous nebulization for as long as 30 min with 2-mL samples (S92). Various attempts to recognize spectral or chemical interferences have been described. A sequential automated fast analysis ($94)permitted higher wavelength resolution. Matrix interferences were found to be more pronounced using a thermospray system for sample introduction rather than with a V mve nebulizer (S95). However, in the presence of HCl,d%l04, or interferences with the two methods of sample introduction were similar. A back ound correction system (S96) with alternate peak and bagground measurements in a single-channel ICPAES with discrete nebulization was described. With this system a quartz refraction plate was inserted in an optical pass and vibrated a t 160-ms intervals with a s uare wave. This permitted the center and wing of a spectralline to be measured alternately. The effects of sampling frequency on background correction was examined for both peak hei h t and peak width measurements. Spectral interferences to b o a t the 238.9-nm emission line in the presence of hi h Fe concentrations, and a t 228.6 nm in the resence of hi$ Ti concentrations, were investigated in f J s (S97). High concentrations of Ti also interfered with the signal for V at 292.4 nm. A one-drop (100 pL) sample introduction enabled multielement analysis of very small masses of tissue (S98). A carbonaceous slurry obtained by heating reference materials to 350 "C with concentrated HzSO, (S99)was successfully processed by the
nebulizer. A summar of various applications for some elements is shown in Jable S-IV.
INDUCTIVELY COUPLED PLASMA MASS SPECTROPHOTOMETRY ICPMS is unique among the techniques reviewed in that the instrumentation permits quantitation of separate stable isoto es of elements. Enrichment approximating 100% of a m e d isotope which normally has a very low abundance is ideal for use as a tracer in metabolic studies. The use of stable isotopes in humans opens a broad field for the study of the biological role of metal ions which was not possible where appropriate radioactive materials have been available, but their use is not permitted due to radiation exposure. The measurement of isotope dilution is a definitive analytical tool for quantitating the concentration of a given element. In addition, absorption, bioavailability, and body pool size for a given element can be determined following administration of one or more enriched isotopes either orally or intravenously and monitoring isotope ratios. Two ICP instruments commercially available in the United States predominate, althou h two similar instruments are now available in Japan. t least one other instrument continues to be marketed on a small scale. The cost of instrumentation is a disadvantage for use in routine clinical chemistry analysis, but availability of an instrument in an academic or research institution offers an opportunity to take advantage of the capabilities of this technique. Interferences to the madcharge ratio of the singly charged positive ions of the isotope to be measured include isobaric overlapping, analyte oxide, analyte hydroxide, doubly charged ions, argon oxide, and argon nitride. A sample's matrix may enhance or suppress ionization and the judicious use of calibration with matrix-matched standards is recommended. Internal standards help to compensate for ionization interferences. Choice of one or more suitable internal standards in close proximity to the particular masses of interest is desirable. Multiple internal standards may be used to cover a broader spectrum of masses.
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Table 9-IV. Sample and/or Instrument Parameters for ICPAES Analyses of Selected Elements preconcn or modification comment sample type element preconcentration pH dependency 3.9-7.9-fold biological, Cu, Fe, Zn, Cr, enhancement environmental Ni, Mn, V exclusion chromatography complexes with A1 ATP, dopamine, epinephrine activated C impregnated 10-foldenhancement biological reference Cd with 8-quinolinol; elution material aqueous solutions iminodiacetic acid-ethyl 10-100-fold enhancement urine, water Cd, Co, Cu, Pb cellulose chelating resin FIA on line speciation for Se serum, breast HPLC, sequential Se, Cu, Fe, Zn, ICPAES milk, RBC Mg, Ca preconcentration with biological samples, Cd, Co, Cu, Pb, ammonium pyrrolidine water Mo, Ni dithiocarbamate precipitation blood, urine hydride generation HI3 argon carrier carries vapor into ICP limit of detection, Sn 30 pg/mL, miniature continuous Ge, Sn flow hydride generator Ge 0.15 ng/mL eliminated Fe interference on-line generation soils B of gaseous methyl borate continuous flow into ICP retention of B low-temperature (150 "C) citrus leaf digestion reference material KCl treatment enhanced signal Al, Cu, Zn serum and other matrices biological materials, ETV miniature cup Al, Pb, Cu, Mn, vaporization environmental Zn particulates biological materials powdered samples Mn, V, Ni on Ag films recycling nebulization certified reference continuous flow 30 min; 2-mL Mg, Ca, P, Al, system sample materials Cu, Co, Fe, Mn, Zn recycling nebulizer argon carrier saturated with serum, aqueous Ca, Cu, Mg,P, Pt water vapor HPLC metallothioneins specific elements carbonaceous slurry results agree well with flame reference materials Mg, Ca, K,Na, and GFAAS Fe, Mn, Cu, Zn reference materials background correction Al, Fe system 1-drop (100 pL) analysis dilution not required fresh liver Cu, Pb, Mn, Cd yttrium internal standard, liver non-heme iron non-heme Fe 2.5 N HCl, 10% TCA While the basic instrument capabilities have not changed significant1 during the period of this review, more compact design a n 2 better sensitivity (-0.1-1.0 ppt) have been achieved. The development of a com act instrument with detection limits similar to those of G d h S directed specifically toward analysis of environmental samples has the advantage of the ra id multielement mass spectrometry capability. Turbomofecular umps have replaced diffusion pumps in some instruments, ence permitting vacuum to be attained without oil contamination of the ion lenses, necessitating frequent cleaning. Introduction of an ETV considerabl minimizes the interference from argon oxide and argon nitridre where these contribute isobaric interference to iron isotopes which are of im ortance in biological investi ations. An autosampler availabg from one manufacturer of t i e ETV makes the analvsis of larae numbers of samdes feasible. Investigations of iron agsorption in womei have been Dublished usinn the ETV/ICP/MS (S102-Sl04). A detailed hescription (SJ05)for attaining optimum instrumental parameters for the recise measurement of isotopes using ICPMS considerexdwell time, cycle time, radio frequency (rf) power level, flow rate of the sample solution, flow rates of the argon plasma nebulizer, and auxiliary and coolant gas. The present review is focused on isoto e dilution applications, the use of isoto e ratios for metaiolic studies with a number of elements &at are of particular interest in the clinical arena, modifications reported for sample introduction into the ar on plasma, semi uantitative analysis, interferences to particufar elements, an% applications of the ETV. Pub-
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ANALYTICAL CHEMISTRY, VOL. 65, NO. 12, JUNE 15, 1993
ref s79 S80 581
582 583 584
585 S86
S87 S88 S89 S90
s91 592 593 Sl00 s99 S96 S98 SlOl
lications on the application of ICPMS to analysis of biological materials have escalated over the last 5 years. Table S-V lists some of the publications that are of particular interest in the clinical field. Other anal s of potential importance measured in biological materi s by this technique include halogen anions (S130, S131), 23r'h/230Th (S132),T h and U in human tissues and diet (S133-S135), Au in drugs after HPLC separation (S136) or with sample introduction by FIA (S137), Mo (S138), as speciation after HPLC separation (S13W3141), Sr levels in urine and plasma and @Sr/@Srin bioavailability studies (S142-S144), Cd in metalloproteins using FIA after on-line HPLC (SI16, S145)or size exclusion chromatography (S146),and identification of organomerc metabolites in biological materials following extraction m 3 toluene (S147). A tungsten spiral ETV was described for sample introduction (S148).Argon chloride interference was successfully removed by the addition of 4.5% N to the coolant and nebulizer as (S149). This was beneficial for analysis of Se and V a n t of As (S150). Semiquantitative analytical capability in ICPMS enables rapid analysis of an unknown solution and provides a basis for quantitative analysis of analytes found to be present in abnormal amounts. Analysis of saliva for endogenous and exogenous metals employed this technique (S151). While commercially available instruments use an argon plasma as an ion source for ICPMS, a helium/argon mixture was investigated as an alternative (S152). Development of a helium plasma source would offer distinct advantages such
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CLINICAL CHEMISTRY
Table S-V.Selected Applications of ICPMS
element
sample type
isotope/element
Fe
erythrocytes
Fe, Ni
speciation in proteins erythrocytes biological samples
Ni Zn
urine biological samples
total element
speciation of proteins
total Zn
absorption in infants hair
6IZn/lQZn WU/@CU
plasma/serum
"CU/Wu
metalloproteins plasma, erythrocytes, urine, feces biological materials biological samples aqueous samples
total element % 3
cu
Cu, Cd Mg Se
Pb
Hg multielement Cd, Cu, Fe, Mn, Mo, Zn V, Cr, Ni, Co, Cu, Mo, Pt, Hg, Bi Fe, Co, Cu, Zn, Rb, Mo, CS 24 elements
inorganic, Pb2+, organic compds blood and environmental materials blood, teeth, paint, environmental materials whole blood
67Fe/MFe wFe/mFe 5lFe @FeI6lFe total element
Fe absorption ETV introduction HPLC on l i e detection incorporation of Fe into Hb resolve interferences by principal component analysis principal component analysis isotope dilution for quantitation preconcn by extraction RPHPLC, on-line time-resolved software
UMg,zMg,26Mg s2Se spike %e, We, 82Se total element isotopic abundance8 mPb/mPb
commenta
ref S102,5103 5104 5106,5107 5108 5109 SllO Slll
5112 5113 5114
ArNa+ interference remove Na by ion exchange remove ArNa+, PO2+ by size exclusion chromatography HPLC, FIA, ICPMS Mg absorption in infants, exchangeable pool size Mg isolated as ammonium phosphate hydride generation hydride generation VB nebulizer detection limits: nebulizer 20-60 ng, hydride 0.6-1.8 ng HPLC separation
5121
compared with reference materials
5122
good stability of measurements in blood over 4 months
5123
accurate, specifies condition
5124
prepared in 50% HCl, EDTA, cysteine
5125
5115 5116 5117 5118 5119 5120
blood, urine
mPb/mlPb mPb/mPb total element
liver
total element
HNOs digestion
5126
urine, seawater
total element
metal complexes absorbed on resin
5127
serum
total element
dilution with "03 correction for polyatomic ions with appropriate blank
5128
3 biological reference materials
total element
5 internal standards wed good results if significantly above detection limits
5129
as elimination of many isobaric interferences due to argon.
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