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CLIN.CHEM.32/9, 1660-1665 (1986)
RoutineMeasurementof Calcium,Magnesium,Copper,Zinc, and Ironin
CoupledPlasmaEmissionSpectroscopy
Urineand Serum by Inductively
David E. Nixon,1 Thomas P. Moyer,’ Peter Johnson,’ John T. McCall,’ Anders B. Ness,2 Wayne H.
Fjerstad,2 and Mark B. Wehde2
We describe an inductivelycoupled plasma atomicemission (1-5). Comprehensive reviews of this technique have been
spectrometer that has been adapted to perform routine, published (6, 7). Briefly, the advantages of ICP are:
simultaneous, direct analyses of calcium, magnesium, cop- Multi-element
#{149} analysis is truly simultaneous.
per, zinc, and iron in serum or urine without sample digestion The
#{149}dynamic range of linear calibration typically covers
or pretreatment. The system, constructed with inexpensive, four to five orders of magnitude of concentration.
readily available components, can analyze 1-mL or smaller #{149} detection limits and sensitivities are as good as if not
The
samples. Results correlate nearly perfectly with those de- better than thosefor FAAS.
rived by standard atomic absorption techniques (r = 0.98 to Solute-vaporization-type
#{149} interferences do not occur.
The obvious advantages, then, of this technique are that
0.997). Using certified serum and urine samples from various
these five elements can be determined in one sample simul-
sources, we demonstrate that the instrument yields accurate
taneously, with no serial dilutions of specimens, and the
results with a precision better than certified values. The
completeanalysis can be performed on one instrument.
instrument is sensitive to one order of magnitude less than
In the last 15 years, numerous papers dealing with the
the lower limit of the normal range in serum or urine for all
ICP determination of analytes in biomedical samples have
elements tested, and respondslinearlyto concentrations two been published [see reviews by Delves (8), Morrison (9),
orders of magnitude higher than the upper limit of the normal Mermet and Hubert (10), and Barnes (11)]. Trace elements
range. With the system described here, these five elements have been determined in urine, serum, blood, tissue, and
can be assayed with the same or less technical effort than other biological specimens. Most of this research has been
needed for a single element by atomic absorption. published by instrument manufacturers, universities, and
laboratoriesassociated with the federal government.Except
AddItIonal Keyphrasee: atomic absorption spectrophotometry for Schramel et al. (12), we know of no other reported ICP
compared multi-element analysis results for more than control specimens or, at best, a few
pooled clinical samples.Unfortunately, an overviewof these
Historically, flame (FAAS) and graphite furnace atomic papers yields little methodology that is directly transferable
absorption spectrophotometry (GFAAS) have been used by to the clinical laboratory facing routine analyses of many
many clinical laboratories to determine calcium, magne- urine and serum specimens each day.
sium, copper, zinc, and iron in serum and urine.3 Although Here we describethe direct, routine, automated determi-
these techniques provide excellent results, each has limita- nation of Ca, Mg, Cu, Zn, and Fe in urine or serum by ICP.
tions unique to atomic absorption spectrophotometry: We describethe complete analytical facility and stream-
#{149} one element can be determined at a time.
Only lined sample treatment and calibration procedures that
Limited dynamic range forces the dilution of high sam-
#{149} allow the direct determination of these five elements with
ples. no sample digestion or preconcentration. To establish accu-
#{149} techniques have limited sensitivity for Cu.
FAAS racy, we analyzed 24-h urine collections and serum speci-
#{149} is sensitive to solute-vaporization
FAAS interferences mens by this technique and by FAAS and GFAAS. Certified
such as the depression of the Ca signal by phosphate. urine and serum control specimens were also analyzed and
Early investigators of inductively coupled plasma (ICP) the results compared with values obtained by either FAAS
techniques found that many of the limitations associated or GFAAS (for copper).
with FAAS techniques were effectively eliminated by ICP
Materials and Methods
Department of’ Laboratory Medicine (H-400) and2 Engineering, Multi-Element ICP System
Mayo Clinic, Rochester, MN 55905. A schematic diagram of the entire ICP system is shown in
Nonstandard abbreviations: FAAS, flame atomic absorption of
Figure 1. The components our six-element direct-reading
spectrophotometry; GFAAS, graphite atomic absorption spec-
trophotometry;ICP, inductively coupled plasma atomic emission system are identified in Table 1.
spectroscopy. The 1-rn-focal-length spectrometer was designed as a
Received April 17, 1986; accepted June 6, 1986. convertible instrument, with both a grating drive and an
1660 CLINICAL CHEMISTRY, Vol. 32, No. 9, 1986
master program of the IBM-PC controls the preparation of
the ICP for analysis; the compilation of patients’ demo-
graphic data from our Laboratory Information System; the
collection and calculation of data for calibration, control,
and sample results; and the management of analysis ifies.
The fused quartz plasma torch is based on a design by
Scottet al. (1). The preciselyboredand ground quartz tubing
was obtained from Wilmad Glass Co., Inc., Buena, NJ
08310. We restricted the aerosoltip of our torch to 1.2 mm,
to direct a narrow stream of argon and sample aerosol into
the ICP. The nebulizer used for sample introduction is a
modified flxed-crossflow device (Model N058-0368) with
spray chamber (Model N058-0368; both from Perkin-Elmer
Corp., Norwalk, CT 06856). We replaced the standard
molded plastic gas inlet to the nebulizer with a smaller-
diameter bored capillary, i.e., a precision-bore (0.1778 mm)
FIg. 1. Schematic diagramof ICP system glass capillary 2.54 mm (o.d.) x 13.5 mm long (Wilmad
Glass Co.), attached to a stainless-steel stop ring 2.21 mm
Table 1. Components of the System for ICP long x 5.23 mm (o.d.) x 2.54 mm (i.d.). This replacement
capillary has essentially the same outside dimensions as the
original Perkin-Elmer molded capillary except for overall
Plasma Plasma-Therm. Inc., Kresson, NJ length. We increased the path-length of penetration into the
High-frequency generator Model HFS-2500E
nebulizer body to bring the gas orifice closer to the back of
Torch One-piece quartz construction
18 mm I.d. plasma tube the sample needle. No modification of the standard Perkin-
14 mmi.d.auxiliaryubet Elmer nebulizer body was needed. The modifications to
Flow meters 1.2mml.d. aerosol tip produce this sample introduction system are shown dia-
Linde 201-4335; 201-4334 grammatically in Figure 2. A more detailed discussion of
Monochromater McPhersonModel216 (1-rn focal these modifications is presented elsewhere (ms. accepted for
length)
Grating 1200 grooves/mm;300-nm blaze publication in Anal Chem).
angle The other nebulizer evaluated was a flxed-crossflow de-
Slits Entrance: 25 m x 4 mm vice (Model 90-790; Jarrell-Ash, Division of Allied Analyti-
Exit: ARL 6910-250 ,..Lm x 4 mm cal, Waltham, MA 02254).
Optics 25 mm x 200 mm focal length, Instrument-operating conditions are summarized in Ta-
planoconvex ble 2. These settings are compromise conditions,attainable
Filter Acton Research Model 395/BR
Photomultipliers Hamamatsu R760 13 mm diam. with any commercially available ICP. We selected these
Computer IBM-PC conditions to optimize the system for Cu analysis. In healthy
Electronics Computer interface-Mayo design
Multichannel readout-Mayo design Precision capitlary
gas orifice
HV and signal boards-Mayo design Critical distance 0.18 mmID
Nebulizers M
Jarrell-Ash odel90-790 minimized
Perkin-ElmerModelN058-0368
Pump Gilson 2;
MinIpuls 10 roller
High pressure
exit slit-frame for multi-element analysis.It canbe operated gas inlet
as a monochromator, a spectrograph for permanent film
records, and a direct-reading polychromator overa spectrum
of approximately 170 nm. A polychromator slit-frame, the
housing for the photomultiplier tubes, and a three-point Solution uptake
self-centering mount were designedand constructed by the tube
Section of Engineering at Mayo Clinic. The emission wave- Fig. 2. Schematic diagram of the modification of the Perkin-Elmer
lengths (nm) isolated for each element on the slit-frame are: nebulizerto allowincorporation ofa precision-bore glass capillary
Zn(I) 213.856, Fe(U) 259.940, MgUI) 293.654, Ca(II) 315.887,
Cu(I) 324.754, and Y(H) 360.073.
Table 2. OperatIng CondItIons for the ICP System
In the polychromator mode, the electronic amplifier is
placed directly behind the photomultiplier tube8, supplying
the high voltage for eachphotomultiplier and the first stage Forwardpower 1300W
of amplification for the signals. Each amplified signal is Reflected power <5W
Gas flow rates
converted first to a frequency signal and then to a light Plasma 15 Ljmin
pulse for transmission. This entire circuit is contained inside Auxiliary Normally off
the spectrometer to avoid being influenced by the high- Aerosol Varies with nebulizer
frequency magnetic fields emitted by the ICP. Each digi- Back pressure 345 kPaa
tized light signal is reconverted to an electronicfrequency Samplepump rate 2.92 mUmln
signal, then sent to an intermediate microprocessor in the Observation height 11 mm
Signalintegration lOs
autosampler. This processor and bus serve as the link aModlfj Perkin-Efmer.
between an IBM-PC computer and the spectrometer.The
CLINICAL CHEMISTRY, Vol. 32, No. 9, 1986 1661
subjects, urinary Cu excretion ranges from 10 to 60 ig/24 h
or approximately 8 to 50 gfL of urine, whereas the concen- Table 3. ComposItIon of Calibrating Standards and
trations of Ca, Mg, Zn, and Fe in urine are significantly Blanks
higher; thus, the detection limit and sensitivity for copper Component and composition Reagent
are more critical and were used to define optimum operating Blank AqueousHNO3, 10 mL/L
parameters. Urine diluent AqueousHNO3, 20 mLJL,containing
100 g of V per liter
Materials Urine standard,mg/L
Ca, 100
Reagents. Stock solutions of Ca, Mg, Cu, Zn, and Fe were Mg, 100
purchased as Baker Instra-Analyzed Atomic Spectral Stan- Zn, 0.50
dards (J. T. Baker Chemical Co., Phillipsburg, NJ 08865). Fe, 0.50
Yttrium stock solution was prepared from yttrium nitrate Cu, 0.050
purchased from Fisher Scientific Co., Chemical Manufac- Serumdiluent Triplydistilledwater
Serum standard,mg/L
turing Div., Fair Lawn, NJ 07410. Concentrated nitric acid Ca, 122.2
was distilled in glass, then redistilled in a Teflon-coated, Mg, 71.7
sub-boiling still and stored in Teflon bottles. Water was Zn, 2.85
triply distilled and stored in carboys dedicated to this use. Fe, 2.18
Controls. The plasma protein control was Lab-Trol Chem- Cu, 1.89
istry Control (lot no. LT1O7-1-15; American Dade, Div. of
American Hospital Supply Corp., Miami, FL 33152). The
urinary Ca, Mg, Zn, and Fe. Urinary copperwas determined
urine control was Urichem Level U (lot no. 523-022; Fisher
with a Perkin-Elmer Model 5000 graphite furnace equipped
Diagnostics, Div. of Fisher Scientific Co., Orangeburg, NY
with a Model HGA 500 temperature controller and a Model
10962).
Patients’ specimens. Serum and urine samples were select-
AS 40 autosampler. These two instruments were used daily
for the serum and urine analyses described here. Procedures
ed without conscious bias from among those sent to our
laboratory for routine analysis for metals. All serum sam- for their use have been described elsewhere (13, 14).
pleswere drawn into acid-leached “Monovette” lO-mLplas-
tic syringes (no. 02.263.100; W. Sarstedt, Inc., Princeton, NJ Results and Discussion
08540). These syringes had been disassembled, leached in
10 milL nitric acid for seven days, rinsed in water, air- Our goal was to accomplishsimultaneous multi-element
dried, reassembled, and sterilized with ethylene oxidebefore analysis of serum or urine in a routine clinical laboratory
use for specimen collection. No beads were usedwith these situation. To assess the viability of the ICP approach, we
syringes. After inserting the needle (no. 5175; Becton Dick- evaluated critical factors such as detection limit, range of
inson Co., Rutherford, NJ 07070) into the vein, we drew calibration, accuracy, and precision after making the critical
several milliliters of blood into a disposable syringe to hardware or software choices(e.g., wavelengths, nebulizer,
cleanse the needle, then attached the Sarstedt syringe and and calibration technique).
drew approximately 8 mL of blood. We let the blood clot for Atomic emission spectra from an ICP are rich in atom and
10 mm, removed the plunger stem, and centriftiged the ion lines, some very intense and some very weak. An
syringe at 3400 rpm for 5 mm. The serum was then emission wavelength can usually be found that provides
decanted into an acid-leached 6-mL plastic screw-top vial adequate sensitivity while avoiding matrix interferences.
(Sarstedt), and the tubes were capped tightly until assay The high concentrations of Ca and Mg in urine and serum
that same day. warrant the choice of weak ion wavelengths for these
The 24-h urine specimens were collected into acid-washed elements in order to avoid multiple sample dilution. The Ca
plastic bottles, then sufficient hydrochloric acid was added to and Mg wavelengths listed in Methods are 260 and 400
adjust the urine pH to less than 2. The specimens were times weaker than the most intense lines, although re-
thoroughly mixed for 2 h, the total volume was measured, searchers commonly choose the most-sensitive Ca and Mg
and aliquots were stored in smaller acid-leached bottles at ICP wavelengths for biomedical analyses (12). ICP charac-
until
-20 #{176}C assay. teristically has a wide dynamic concentration range, but for
analyses involving the more sensitive wavelengths, addi-
Other Procedures tional dilutions must be made for very high analyte concen-
Calibration. Reagents prepared for urine or serum cali- trations. Thus the choiceof the most sensitive wavelength,
bration are listed in Table 3. For the analysis of urine when unnecessary, compromises and negatesthe real power
samples, we calibrated the ICP with an aqueous acidic of ICP-simultaneous multi-element analysis.
standard prepared from stock solutions. All samples were When sera are diluted 10-foldand urine specimens dilut-
diluted with an equal volumeof 20 mL/L nitric acid contain- ed twofold,detection limits are more than adequate,even in
ing yttrium internal standard. the case of urine copper. The weak wavelengths we chosefor
For serum specimens, triply distilled water was the Ca and Mg are adequate for detecting these analytes in
preferred diluent, to avoid precipitation of protein. Calibrat- biomedical samples and provide linear dynamic ranges
ing standards, controls, and samples were diluted 10-fold sufficient to determine abnormally high analyte concentra-
with water before assay. The ICP was calibrated with tions with no further dilution. On the other hand, we chose
Cation-CalTM Calibration Reference (American Dade). The the most sensitive wavelengths for Cu, Zn, and Fe because
concentrations listed in Table 3 were confirmed by FAAS. normal concentrationsof these analytes are in the .ug/L
Atomic absorption spectrometers. We used a Perkin-Elmer range. With the most sensitivewavelength selected for Fe,
Model 460 FAAS with an air-acetylene single-slot burner the range is adequate to assay without dilution Fe concen-
for all serum results comparisons and for the analysis of trations in urine from patients with hemochromatosis.
CHEMISTRY,
1662 CLINICAL Vol.32, No.9, 1986
Table 4. DetectIon Limits and Sensitivities Produced by Nebulizers
Detection limits, mg/L Sensltlvitya
Nebulizer Ca Mg Cu Zn Fe Ca Mg Cu Zn Fe
Jarrell-Ash 0.024 0.090 0.006 0.003 0.004 0.056 0.034 1.96 1.70 0.66
Perkin-Elmer 0.114 0.172 0.002 0.006 0.010 0.010 0.019 1.05 0.40 0.16
Modified Perkin-Elmer 0.050 0.147 0.002 0.002 0.006 0.064 0.033 2.13 1.81 0.69
a Calibration
curve slope (or net intensity/elementconcentration in 1zg/L).
Nebulizers elements-variations in stray light may impinge on one or
The nebulizer creates a fine mist of sample aerosol more of the analyte channels (2). These variables can also
suspended in a carrier gas, which is swept into the excita- affect the sample flow into the nebulizer. For analyte
tion source. Unlike atomic absorption nebulizers with wide- concentrations >10-fold the detection limit, this variance in
bore orifices for gas and sample, nebulizers designed for ICP stray light signal or nebulization efficiency has little effect
have gas orifices small enough to produce a high-velocity jet on the final result. However, when analyte content is near
stream (>500 mIs) past the sample orifice and a sample the detection limit (as is the case for urinary copper), these
orifice large enough to allow the free aspiration of material contributions must be taken into consideration.
such as urine or diluted serum without clogging (15-18). Investigators have taken several approachesto this prob-
The efficiencyand uniformity of this nebulization process lem. Some simply do not report values for urinary copper
directly influences detection limits and sensitivity. (19,20), whereas others make a complete extraction of the
We evaluated pneumatically operated crossflow nebuliz- analytes from the urinary matrix, using a resin (21, 22).
era from Jarrell-Ash and Perkin-Elmer. Although the Jar- More typical solutions have either centered on making
rell-Ash nebulizer produced excellent detection limits and corrections by using expensive computer-controlled, stepper-
sensitivities (Table 4), the presence of any particulate mat- motor-driven, direct-reading instruments to measure back-
ter in the sample, e.g., aggregated protein, clogged the ground excursions at the wavelength adjacent to the analyte
sample-uptake tube, necessitating stopping the ICP and wavelength or using an internal standard element to gauge
cleaning the aspiration tip. This considerably interrupted the signal fluctuations from the urine alone (23-25).
operation, with blockages occurring at least once for each 6 Our approach is to add yttrium at a low concentrationto
h of operation. each urine specimen as an internal standard (25). Added at
The nebulizer from Perkin-Elmer offers a different ap- a concentration near the upper normal copper concentration
proach. It is completely demountable, and the inexpensive (50 zg/L), this providesa sensitive corrector of significant
gas and sample needles, made of molded plastic, are easily background shifts. Other investigators have used the inter-
replaced, because new needles fit prebored holes in the nal standard approach for background corrections (23,24),
nebulizer body. Sample-needle penetration and alignment but they addedthe internal standard at concentrations500-
are predetermined by a stop ring molded on the needle. fold greater than the expected analyte concentration. An
However, this system is not self-aspirating. The stock Per- internal standard addedat low concentrationcan correct for
kin-Elmer nebulizer produced sensitivities (calibration re- background shifts, as demonstrated by the close correlation
sponses) ranging from 18% to 54% of those attained with the of urinary copper measured by ICP and GFAAS shown in
Jarrell-Ash design (Table 4). When serum or urine samples Table 5. When we added yttrium at 5000 ugfL, however,
were pumped into this device, a visible stream of iridescent background changeswere not detectedand the correlation
particles traversed the aerosol channel of the ICP, which was not acceptable.
suggested that the stock Perkin-Elmer nebulizer produced ICP detection limits are 20- to 50-foldmore sensitivethan
large aerosol droplets. Under our conditions of operation, the normal serum concentrations of Cu, Zn, and Fe. Normal
these droplets were transported through the ICP too rapidly, concentrationsof stray-light-producing elements such as
sothat atomization was incomplete. The net result was poor calcium are significantly lower and much less variable in
analytical performance. diluted serum than in urine. We have alsoobserved that the
To retain the detection limit and sensitivity performance nebulization characteristics of diluted serum samples are
of the Jarrell-Ash design and the serviceability of the nearly identical. These observationssuggest that, unlike
Perkin-Elmer unit, we replaced the original gas orifice of urine analysis, internal standard correctionsare of minor
the Perkin-Elmer nebulizer with a glass capillary having a value in serum analysis.
diameter 75% of the original. We also extended the capillary Some investigators have suggested that sera must be
to bring the high-velocity gas stream closer to the rear of the digestedbeforeanalysis (20,26). Others have usedaqueous
sample orifice (Figure 2). The net result of this modification calibrating solutions for serum analyses (24, 27). Tech-
is presented in Table 4. With this simple substitution and no
modification to the nebulizer body, sensitivities were im- Table 5. Regression Relationships for Patients’
proved fourfold and detection limits were improved by a Samples Analyzed by Atomic Absorption (a) and ICP (
factor of two. Overall performance of the device was equiva- Urine (n = 160) Serum (n = 169)
lent to or better than the Jarrell-Ash fixed-croasfiow nebu-
lizer, and the ease of maintenance of the stock Perkin-Elmer Regression Regression
nebulizer is retained. These modifications are critical to equation r equation r
making our system sensitive and trouble-free. Ca y= 0.97x + 3.2 0.997 y = 0.98x + 0.17 0.996
Mg y= 0.91x- 1.8 0.95 y= 1.Olx- 0.05 0.98
Calibration Cu y= 0.93x + 4.1 0.97 y = 1 .05x - 0.05 0.98
Zn y= 0.90x + 78.6 0.996 y = 0.98x + 0.03 0.98
Because of the variations inherent with urine speci- Fe y= 0.87x - 12.1 0.997 y = 0.99x + 0.00 0.997
mens-salt content, total volume, organic matter, and other
CLINICAL CHEMISTRY, Vol. 32, No.9, 1986 1663
Table 6. Results for the Analysis of Serum and Urine Controls with the Modified Perkin-Elmer Nebullzer
Concn, mg/L (! ± 2 SD)
Ca Mg Fe Zn Cu
Fisher Urichem Urine Control
1CP 94 ± 4 159 ± 10 0.08 ± 0.02 0.42 ± 0.04 0.20 ± 0.02
Certifiedvalue 104 ± 11 163 ± 10 0.09 ± 0.028 0.48 ± 0.08 0.19 ± 0.05
Dade Lab-trolPlasma ProteinControl
ICR 98.4 ± 2.1 25.2 ± 2.2 0.64 ± 0.09 0.35 ± 0.05 0.92 ± 0.08
Certified value 99.0 ± 3.0 25.0 ± 1.6 0.63 ± 0.11 0.31 ± 0.048 0.91 ± 0.08’
by
‘values notcertified;determined FAAS. n = 10.
400 accomplished simultaneously by ICP from the detection
limit (which is 10-fold less than normal range) to 104-fold
above the detection limit (approximately 102-fold above the
normal range) with no sample dilution or pretreatment.
300
‘5. References
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n = 99 Chem 1974;46:1155A.
R = 0.996
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calibration curves from aqueous standards, we observed 8. Delves HT. The analysis of biological and clinical materials
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materials by ICP [Review]. ICP Inf Newsl 1984;1O:299-301.
Assays of Samples and Controls 12. Schramel P, Liii G, Hasse S. Mineral and trace elements in
To test the validity of our wavelength selections, calibra- urine. J Clin Chem Clin Biochem1985;23:293-301.
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clinical specimens; we alsoanalyzed certified, commercially 14. Halls DJ, Fell OS, Dunbar PM. Determination of copper in
available urine and serum controls (Table 6). urine by graphite furnace atomic absorption spectrometry.Cliii
Regression relationships, with FAAS or GFAAS as the Chim Acts 1981;114:21-7.
independent variable, are shown in Table 5 for urine and 15. Wohlers CC, Hoffman CJ. Improvementsin nebulizer design
serum samples. Agreement between the ICP and FAAS for the inductively coupledplasma.ICP Inf Newsl 1981;6:500-7.
results was excellent for all elements in serum. Close 16. Novak JW Jr, Lillie DE, Boorne AW, Browner RF. Fixed
correlation of urine results was obtained, although the slope croesfiow nebulizer for use with inductively coupled plasmas and
values suggest a bias by one method-probably because flames. Anal Chem 1980;52:576-9.
additional dilution is not required for ICP. In Table 5 the 17. Gustavsson A. The determination of some nebulizer character-
data for urine constituents range from abnormally low to istics. Spectrochim Acta 1984;39B:743-6.
abnormally high. For urine copper, the comparison of ICP 18. Fjjishiro Y, Kubota M, Ishida K A study of designs of a
results was made with those obtained from GFAAS. Figure S
croesfiownebulizer for ICP atomicemissionspectrometry. pectro-
chim Acts 1984;39B:617-20.
3 illustrates the near perfect correlation of these two tech-
19. DelvesHT, Bunker V, Husbands AP. A comparison of induc-
niques for urinary calcium, which is typical for the elements tively-coupledplasma optical emission spectroecopy and atomic
and sample types studied. With our choice of wavelengths, absorption spectroscopy for multielementalanalysesofdiets, faeces,
calibration technique, and modified nebulizer, accurate and urine. Proc 2nd hit Workshop,Trace Elem Anal Chem Med
analysis of urine and serum Ca, Mg, Cu, Zn, and Fe can be Biol. Berlin: Walter de Gruyter & Co. 1983:119-22.
1664 CLINICALCHEMISTRY, Vol. 32, No.9, 1986
20. SuddendorfRF, Smith GL. Inductively coupledplasma (ICP) 24. Uchida H, Nqjiri Y, Haraguchi H, Fuwa K. Simultaneous
emission 8pectroecopy: concepts and clinical applications. Cliii Lab
J multi-element analysis by inductively-coupled plasma emission
Autom 1983;3:256-62. spectrometry utili.ing micro-sampling techniques with internal
standard. Anal Chim Acts 1981;123:57-63.
21. Barnes RM, Genna JS. Concentration and spectrochemical 25. Nixon DE, McCall JT. A comparison of inductively coupled
determination oftracemetals in urine with a poly(dithiocarbamate) plasma and atomicabsorption spectrometry for the direct determi-
resin and inductively coupled plasma-atomic emission spectrome- nationofCa, Mg, Fe, Zn, and Cu in urine without preconcentration.
try. Anal Chem 1979;51:1065-70. 17thGreat Lakes Regional ACSMeeting, June 1-3, 1983;paper no.
85. Washington, DC: Am. Chem.Soc.
22. Barnes RM, Fodor P, Inagaki K, Fodor M. Determination of 26. Mianzhi Z, Barnes RM. Determination of major, minor, and
trace elements in urine using inductively coupled plasma spectroe- trace elements in human serum by using inductively coupled
copy with poly(dithiocarbamate) chelating resin. Spectrochim Acts plasma-atomic emission spectroecopy.ApplSpectroec 1985;39:793-
1983;38B:245-57. 6.
27. Herber RPM, Pieters JH, Elgerema JW. A comparison of
23. Kimberly MM, Paschal DC. Screening for selected toxic ele- inductively coupled plasma atomic emission spectrometry and
ments in urine by a sequential-scanning inductively-coupled plas- electrothermal atomization atomic absorption spectrometry in the
ma atomic emission spectrometer. Anal Chim Acta 1985;174:203-. determination ofcopperand zinc in serum. Freeenius Z Anal Chem
10. 1982;313:103-7.
CUNICAL CHEMISTRY, Vol. 32, No.9, 1986 1665
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