Graphite Furnace Atomic Absorption Research Articles

Use of iridium plus rhodium as permanent modifier to determine As, Cd and Pb in acids and ethanol by electrothermal atomic absorption spectrometry

The most severe interferences in atomic absorption spectrometry are caused by the presence of anions when they are in different concentrations in the samples and in the calibration solutions. The analyte addition technique or matrix matching calibration can be employed to minimize or compensate the non-spectral interferences, but they are time consuming or difficult to be carried out. The use of chemical modifiers usually allows higher pyrolysis temperatures and consequently the removal of components of the sample matrix, equalizing the analyte signal in the sample and in the calibration solution. In this work, a mixture of Ir and Rh is proposed as permanent modifier to determine As, Cd and Pb in diluted hydrochloric, sulfuric and phosphoric acids and in ethanol and methanol by electrothermal atomic absorption spectrometry (ET AAS) with calibration against 1% v/v nitric acid aqueous solutions. The performance of the proposed permanent modifier was compared to that of Pd plus Mg nitrates in solution. Better recoveries, low background levels and faster analysis were obtained with the permanent modifier. The permanent modifier was also successfully employed for the determination of As, Cd and Pb in different concentrations of sulfuric and hydrochloric acids. For the phosphoric acid, the proposed modifier was only efficient for acid concentrations up to 2% v/v for As and up to 5% v/v for Cd and Pb. The precision, expressed as the relative standard deviation ( n=3), was lower than 10%, for all samples, including ethanol and methanol.

Lead levels in primary teeth of children living in Mexico City.

The aim of this study was to discover the lead concentration in primary teeth extracted in the peripheral clinics of the Faculty of Dentistry, UNAM (Mexico City). One hundred healthy primary teeth were collected from 2 to 13-year-old children (52 girls and 48 boys). Sixty-six were maxillary teeth and 34 were mandibular teeth. Lead concentrations were measured by Graphite Furnace Atomic Absorption Spectrophotometry. Our results indicate that lead concentration in the 10-13-year-old group (7.7 micro g/g(-1)) was higher than in the other groups. Geometric mean lead concentration was higher in girls than in boys (7.3 micro g/g(-1) and 6.3 micro g/g(-1), respectively). Maxillary teeth had higher lead concentrations than mandibular teeth and primary canines showed the highest mean lead concentration followed by incisors and molars. Teeth from children living in the south-east area (which according to the Mexico City's Pollution Center data is the more polluted area), presented the highest lead concentration but no statistically significant difference was found among teeth from the different areas. Our results suggest that age, gender and place of residence are not related to the lead concentration in human primary teeth. This fact seems to indicate the ubiquitous presence of lead in the whole atmosphere of Mexico City and suggests that zones of residence do not appear to influence tooth lead concentration.

Determination of Cd, Cu, Fe, Pb and Tl in gasoline as emulsion by electrothermal vaporization inductively coupled plasma mass spectrometry with analyte addition and isotope dilution calibration techniques

The presence of some elements can be undesirable in gasoline, not only by the possibility of damage of the motor parts and poor performance of the fuel, but also because of the pollution caused by the release of toxic metals to the atmosphere by the combustion of the fuel. The gasoline sample preparation as emulsion is an adequate method for the sample introduction for sensitive analytical methods. In this work, external calibration with aqueous standards, analyte addition and isotope dilution calibration techniques were employed for the determination of Cd, Cu, Fe, Pb and Tl in gasoline by electrothermal vaporization inductively coupled plasma mass spectrometry. The concentrations of Cu and Fe were additionally determined by electrothermal atomic absorption spectrometry. The ETV program for the analytes in a gasoline sample emulsion was optimized and the determination was carried out without modifier at 400 °C pyrolysis and 1900 °C vaporization temperatures. In these conditions, the external calibration against aqueous standards could not be applied for the analysis of gasoline as emulsion, since the results of recovery tests were not acceptable. The determination by analyte addition or isotope dilution employing these conditions could be carried out for Cd, Cu, Pb and Tl, but not for Fe. The use of 10 mg Pd in solution as chemical modifier allowed the determination of all studied analytes together, at 800 °C pyrolysis and 2100 °C vaporization temperatures. The limits of detection for the analytes in gasoline, by analyte addition or by isotope dilution, were better than 5 μg l −1. The measured concentrations for all analytes by analyte addition and by isotope dilution calibration techniques were mostly in agreement and the precision for both calibrations were also similar and adequate. Agreement was also found with concentration results for Fe and Cu obtained by ET AAS, without modifier.

Development of methodologies to determine aluminum, cadmium, chromium and lead in drinking water by ET AAS using permanent modifiers

In this work, methodologies were developed to determine aluminum (Al), cadmium chromium and lead in drinking water by electrothermal atomic absorption spectrometry using permanent modifiers. No use of modifier, iridium, ruthenium, rhodium and zirconium (independently, 500 μg) were tested to each one analyte through the pyrolysis and atomization temperatures curves. As the matrix is very simple, did not had occurred problems with the background for all metals. The best results obtained for cadmium and chromium was with the use of rhodium permanent modifier. For lead and aluminum, the best choice was the use of zirconium. The selection for the modifier took into account the sensitivity, form of the absorption pulse and low atomization temperature (what contributes to elevate the useful life of the graphite tube). For aluminum using zirconium permanent, the best pyrolysis and atomization temperatures were respectively, of 1000 and 2500 °C with a characteristic mass (1% of absorbance, m o) of 19 pg (recommended of 20 pg). For cadmium, with use of rhodium the best temperatures for the pyrolysis and atomization were respectively of 400 and 1100 °C, with a symmetrical peak and with a m o of 1.0 pg (recommended of 1.0 pg). For chromium with rhodium permanent, the best temperatures for pyrolysis and atomization were respectively of 1000 and 2200 °C, with symmetrical peak and m o of 5.3 pg (recommended of 5.5 pg). For lead with zirconium permanent, the best temperatures for pyrolysis and atomization were of 700 and 2400 °C, with symmetrical peak and with m o of 30 pg (recommended of 20 pg). Water samples spiked with each one of the metals in four different levels inside of the acceptable values presented recoveries always close to 100%. The detection limits were of 0.1 μg l −1 for cadmium; 0.2 μg l −1 for chromium; 0.5 μg l −1 for lead and 1.4 μg l −1 for aluminum.

Inorganic analysis of dust fall and office dust in an industrial area of Jordan

This article deals with the determination and comparison of heavy metals and water-soluble anions and cations in indoor dust and outdoor dust fall in the petroleum refinery area in Jordan. Three sampling sites were considered in the Jordanian petroleum refinery complex for the collection of dust fall and office dust samples. These samples were analyzed for water-soluble anions (F −, Cl −, Br −, NO 3 −, C 2O 4 2−, and SO 4 2−) and cations (Li +, Na +, K +, Mg 2+, and Ca 2+) using auto-suppressed ion chromatography. Heavy metals (Pb, Cd, Cu, Zn, Cr, Fe, and Al) were determined using flame or graphite-furnace atomic absorption. No correlations were found between heavy metal concentrations in dust fall and office dust samples, indicating different sources. High enrichment factors for heavy metals were found in dust-fall samples, except for Fe and Cr. Zinc showed the highest and cadmium the lowest flux rates.

Lead Levels in Urine of Never-Smoking Adult Women in Non-Polluted Areas in Japan, with References to Cadmium Levels in Urine

The present study was initiated to assess current level of general population exposure to lead (Pb) in terms of Pb in urine (Pb-U). For this purpose, spot urine samples were collected from 2,332 never-smoking adult women in 10 areas all-over Japan, and were subjected to analysis for Pb-U by graphite furnace atomic absorption (GFAA). Data on cadmium in urine (Cd-U) as measured by GFAA were cited from a previous publication). The grand geometric means (GM) for Pb-U as observed, as corrected for creatinine (cr) and as corrected for a specific gravity of 1.016 were 1.06 microg/l, 1.28 microg/g cr and 1.14 microg/l, respectively, with small intra- and inter-variations with geometric standard deviations of about 2 or less. Arithmetic means of the 10 GMs (one each for the 10 areas) were 1.05 microg/l, 1.19 microg/g cr and 1.18 microg/l, respectively. The levels observed appeared to be lower than levels reported for other populations in the world. Chronological comparison within Japan suggested a gradual decrease in Pb-U in past over 20 yr. No close correlation was detected between Pb-U and Cd-U.

Evaluation of zirconium as a permanent chemical modifier using synchrotron radiation and imaging techniques for lithium determination in sediment slurry samples by ET AAS

In the present paper, lithium was determined in river sediment using slurry sampling and electrothermal atomic absorption spectrometry (ET AAS) after L’vov platform coating with zirconium (as a permanent chemical modifier). The performance of this modifier and its distribution on the L’vov platform after different heating cycles were evaluated using synchrotron radiation X-ray fluorescence (SRXRF) and imaging scanning electron microscopy (SEM) techniques. The analytical conditions for lithium determination in river sediment slurries were also investigated and the best conditions were obtained employing 1300 and 2300 °C for pyrolysis and atomization temperatures, respectively. In addition, 100 mg of sediment samples were prepared using 4.0 mol l −1 HNO 3. The Zr-coating permitted lithium determination with good precision and accuracy after 480 heating cycles using the same platform for slurry samples. The sediment samples were collected from five different points of the Cachoeira river, São Paulo, Brazil. The detection and quantification limits were, respectively, 0.07 and 0.23 μg l −1.

Iron analysis in atmospheric water samples by atomic absorption spectroscopy (AAS) in water-methanol.

To distinguish between Fe(II) and Fe(III) species in atmospheric water samples, we have adapted an analytical procedure based on the formation of a specific complex between Fe(II) and ferrozine (FZ) on a chromatographic column. After elution of Fe(III), the Fe(II) complex is recovered with water-methanol (4:1). The possibility of trace iron measurements in this complex medium by graphite-furnace atomic-absorption spectrometry has been investigated. A simplex optimization routine was required to complete the development of the analytical method.

Optimum phase-behavior formulation of surfactant/oil/water systems for the determination of chromium in heavy crude oil and in bitumen-in-water emulsion

An “oil in water” formulation was optimized to determine chromium in heavy crude oil (HCO) and bitumen-in-water emulsion (Orimulsion-400®) samples by transversally heated electrothermal atomic absorption spectrometry (TH-ET AAS) using Zeeman effect background correction. The optimum proportion of the oil–water mixture ratio was 7:3 v/v (70 ml of oil as the internal phase) with a non-ionic surfactant concentration (Intan-100) in the emulsion of 0.2% w/w. Chromium was determined in different crude oil samples after dilution of the emulsions 1:9 v/v with a 0.2% w/w solution of surfactant in order to further reduce the viscosity from 100 to 1.6 cP and at the same time to bring the concentration of chromium within the working range of the ET AAS technique. The calibration graph was linear from 1.7 to 100 μg Cr l −1. The sensitivity was of 0.0069 s l μg −1, the characteristic mass (m o) was of 5.7 pg per 0.0044 s and the detection limit (3σ) was of 0.52 μg l −1. The relative standard deviation of the method, evaluated by replicate analyses of three crude oil samples varied in all cases between 1.5 and 2.6%. Recovery studies were performed on four Venezuelan crude oils, and the average chromium recovery values varied between 95.9–104.8, 90.6–107.6, 95.6–104.0 and 98.8–103.9% for the Cerro Negro, Crudo Hamaca and Boscán crude oils and for the Orimulsión®-400, respectively. The results obtained in this work for the Cerro Negro, Crudo Hamaca and Boscán crude oils and for the Orimulsión®-400 following the proposed procedure were of 0.448±0.008, 0.338±0.004 0.524±0.021 and 0.174±0.008 mg Cr l −1, respectively, which were in good agreement with the values obtained by a tedious recommended standard procedure (respectively: 0.470±0.05, 0.335±0.080, 0.570±0.021 and 0.173±0.009 mg Cr l −1).

Determination of cadmium in human urine by electrothermal atomic absorption spectrometry

In the present work, a fast acid digestion method was applied to the determination of cadmium in urine samples by electrothermal atomic absorption spectrometry (ET AAS). The pyrolysis and atomization temperatures were 400 and 1200 °C with a characteristic mass of 1.3 pg. Quantification was made with matrix matching calibration curves. The method was validated by the analysis of certified urine samples. Differences were not observed among the levels of the metal in populations from metropolitan and rural areas. The limit of detection (LOD, k=3, n=10) was 0.08 μg l −1. Coefficients of variation for intra- and interassay studies were 5.5 and 12.7%, respectively. Recovery of spiked samples showed acceptable values. Significant correlation was observed among sex, with higher values for women. Age also showed an influence on urinary Cd levels, being higher for individuals over 46 years. No correlation was found between either tabagism or alcoholic beverage intake and of urinary cadmium levels.

Cloud point formation based on mixed micelles in the presence of electrolytes for cobalt extraction and preconcentration

A new micelle-mediated phase separation of metal ions, applied for preconcentrating trace levels of cobalt as a prior step to its determination by flame atomic spectroscopy, has been developed. Two methods were proposed employing both Triton X-100 and sodium dodecyl sulfate (SDS) as a mixed micellar system while the phase separation was induced by HCl or NaCl addition. Cobalt was complexed with pyridylazo compounds (PAN, PAR, 5-Br-PADAP) in an aqueous surfactant medium and it was concentrated in the surfactant rich phase after phase separation. The chemical variables affecting the cloud point extraction were evaluated, optimized and successfully applied to cobalt determination in pharmaceutical samples. Under the optimized conditions, the preconcentration system permitted limits of detection as 1.1 and 1.6 μg l −1 cobalt, respectively, when HCl and NaCl were used. Both proposed methods showed linear calibration within a 25–200 μg l −1 cobalt range. The extraction efficiency was investigated at different cobalt concentrations (40–185 μg l −1) and good recoveries (98–102%) were obtained by using NaCl as electrolyte. The results obtained were compared with those observed with ET AAS.

Determination of chromium and selected elements in multimineral and multivitamin preparations and in pharmaceutical raw material

The content of elements in pharmaceutical preparations is one of the indispensable factors of the evaluation of their quality. In the present work, the following macro- and microelements Ca, Cr, Cu, Fe, Mg, Mn, Mo, P, Se and Zn were determined in multimineral and multivitamin preparations and in pharmaceutical raw material. Inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ET AAS) were used throughout the study. The examined samples were dissolved in a high-pressure microwave system using concentrated nitric acid. The effect of the carbon residue in the digest solution on the determination result was eliminated by introducing an equation correcting the ArC + interference with 52Cr.

Survey of lead, cadmium, iron, copper and zinc in Kasar cheese

Lead, cadmium, iron, copper and zinc contents of Kaşar cheese sold in the markets of Ankara, Turkey, were determined over 12 months. A total of 240 samples comprising 10 different brands were analysed. Graphite-furnace atomic absorption was employed for the determination of lead and cadmium, and flame atomic absorption for iron, copper and zinc. The mean (range) of the lead, cadmium, iron, copper and zinc content of the samples were 86 (10–421) μg kg-1, 1.8 (0.3–8.3) μg kg-1, 4.2 (1.0–14.1) mg kg-1, 0.7 (0.3–1.6) mg kg-1 and 37.7 (26.5–63.0) mg kg-1, respectively. The samples in November, December and January contained higher amounts of lead than those in other months (p < 0.01). Moreover, important differences existed in lead content of the samples between different cheese producers (p < 0.01). The differences in cadmium and iron content of the samples for different months were important (p < 0.01). The iron content of the samples among manufacturers also varied significantly (p < 0.01). However, there were no significant differences in copper and zinc contents of the samples over 12 months (p > 0.05). These findings suggested that some contamination occurred during milk production and/or manufacturing of cheese depending on the equipment used. For a consumption of 100 g Kaşar cheese, one would ingest approximately 8.6 μg (4% of the provisional tolerable daily intake, PTDI) of lead, 0.2 μg (0.3%) of cadmium, 0.4 mg (0.9%) of iron, 0.07 mg (2%) of copper and 3.8 mg (6%) of zinc. Therefore, it was concluded that Kaşar cheese is not a significant contributor to the intake of investigated heavy metals.

Determination of cadmium in biological samples solubilized with tetramethylammonium hydroxide by electrothermal atomic absorption spectrometry, using ruthenium as permanent modifier

The feasibility of Ru as a permanent modifier for the determination of Cd in biological samples treated with tetramethylammonium hydroxide (TMAH) by ET AAS was investigated. The tube treatment with Ru was carried out only once and lasted for about 300 atomization cycles. The pyrolysis and atomization temperatures, 750 °C and 1300 °C, respectively, were chosen from the temperature curves. The sample dissolution procedure was very simple: a sample aliquot was mixed with a small volume of a 25% m/v TMAH solution, the volume was made up to 50 ml and the mixture was kept at 60 °C for 1 h. Six certified biological reference materials were analyzed and the obtained Cd concentrations are within the 95% confidence interval of the certified values, proving the accuracy of the proposed procedure for a variety of biological samples. The calibration curve, with correlation coefficient higher than 0.99, was established for a working range up to10 μg l −1. The precision was good as demonstrated by relative standard deviations below 3%, except for one sample. The limit of detection (3σ) was 0.05 μg l −1 and the characteristic mass was 1.30 pg, obtained in the presence of the Ru modifier.

Mercury, arsenic, lead and cadmium in fish and shellfish from the Adriatic Sea

The aim was to measure concentrations of total mercury, total arsenic, lead and cadmium in common edible fresh fish and shellfish from various areas of the Adriatic Sea. Estimates of intake of these elements were made through seafood consumption by the general population. Samples were either wet digested for mercury and arsenic, or dry ashed for lead and cadmium analysis. Mercury was measured by cold vapour atomic absorption spectrometry (CV AAS) and arsenic, lead and cadmium by electrothermal atomic absorption spectrometry (ET AAS). Quality control procedures of analytical methods, which included analyses of dogfish muscle-certified reference material DORM-2, confirmed the acceptability of methods. The highest mercury and arsenic concentrations were found in hake (Merluccius merluccius) and the lowest in mackerel (Scomber scombrus). The respective values in hake were 0.373 ± 0.075 and 23.3 ± 3.6, and in mackerel 0.153 ± 0.028 and 1.06 ± 0.29 mg kg-1 fresh weight (mean ± SD). Lead and cadmium concentrations were about 10 times higher in shellfish than in analysed fish. The highest lead and cadmium concentrations were found in mussel (Mytilus galloprovincialis) and the lowest in hake. Respective lead and cadmium values in mussel were 0.150 ± 0.009 and 0.142 ± 0.017, and in hake were 0.007 ± 0.004 and 0.002 ± 0.001 mg kg-1 fresh weight. The concentrations of analysed elements were below acceptable levels for human consumption set by the Croatian Ministry of Health, except for total arsenic. The estimated intake of those trace elements included in this study through seafood consumption by the general population did not exceed the provisional tolerable weekly intake recommended by the Joint FAO/WHO Expert Committee on Food Additives.

Lead in Young Herring Gulls: Paradoxical Effects of Exercise on Tissue Concentrations

Exposure to lead prenatally and early in life affects physiological, behavioral, and intellectual development in humans and other animals. The movement and storage of lead within tissues and organs and its elimination from the body influence the amounts reaching sensitive target organs such as the developing brain. In this study, young herring gulls, Larus argentatus, were used to examine the effect of mild exercise on the deposition of lead in bone, to clarify possible differences between free-ranging birds in nature and confined birds in the laboratory. Forty 2-day-old chicks were randomly assigned to one of four groups: lead treatment with and without exercise, and controls with and without exercise. Chicks in the lead treatment group received a single intraperitoneal injection of lead acetate solution (100 mg/kg); weight-matched control chicks were injected with an equal volume of isotonic saline at the same age. Chicks in the exercise groups were taken outside and encouraged to move about for 2.5 h/d; others were confined in standard cages. Chicks were sacrificed at 45 d of age and lead was analyzed by graphite furnace atomic absorption. The interaction of exercise and lead dose significantly influenced the amount of lead in the three bones examined (rib, humerus, tibiotarsus), but not in the other tissues. For the lead-treated birds, mean bone lead levels were lower in the exercised versus nonexercised birds, while the reverse was true for control chicks. The data suggest that lead storage can be partly ameliorated by exercise, that young chicks would be the most affected by lead, and that older chicks that move and have larger territories in which to move may suffer lesser effects than those in dense territories.

Determination of As, Cd, Pb and Se in DORM-1 dogfish muscle reference material using alkaline solubilization and electrothermal atomic absorption spectrometry with Ir+Rh as permanent modifiers or Pd+Mg in solution

In this work, tetramethylammonium hydroxide (TMAH) was used to solubilize the DORM-1 dogfish muscle certified reference material as a model substance for the determination of As, Cd, Pb and Se by electrothermal atomic absorption spectrometry (ET AAS). The sample was mixed with a small amount of TMAH and heated to 60 °C for 10 min in a water bath. After dissolution, As and Se were determined using palladium and magnesium nitrates as a chemical modifier added in solution. For Cd and Pb, best results were obtained with a mixture of 250 μg of each of iridium and rhodium as permanent modifiers. In both cases, the calibration was performed with aqueous solutions in 0.2% v/v HNO 3. The temperature program for each analyte was optimized using pyrolysis and atomization curves established with the fish reference material. The detection limits in dry samples and the characteristic mass values were: Cd 0.005 μg g −1 and 0.9 pg; Pb 0.04 μg g −1 and 7.6 pg; As 0.4 μg g −1 and 13 pg and Se 0.6 μg g −1 and 20 pg, respectively. Results from the determination of these elements in the DORM-1 certified fish reference material were within the 95% confidence interval of the certified values.

Determination of total chromium traces in tannery effluents by electrothermal atomic absorption spectrometry, flame atomic absorption spectrometry and UV–visible spectrophotometric methods

Three different analytical methods comprising colorimetric method with 1,5-diphenyl-carbazide, electrothermal atomic absorption spectrometry (ET AAS) and flame atomic absorption spectrometry were utilized in a study to determine traces of chromium (Cr) in synthetic tannery effluent from laboratory scale treatment process variations. All the results obtained using the three different methods showed good agreement and met the requirement of Brazilian regulation for total Cr for effluent discharges (<0.5 mg l −1). However, ET AAS has been the proposed method because it was faster, less laborious, needed smaller volume of sample and presented lower limit of quantification (LOQ=2.2 μg l −1).

Correlates of bone and blood lead levels among middle-aged and elderly women.

In 1993-1995, the authors evaluated risk factors for elevated blood and bone lead levels in 264 Boston, Massachusetts, area women previously selected for a case-control study of lead and hypertension. Bone lead was measured at the tibia and patella with K x-ray fluorescence. Blood lead was analyzed by graphite furnace atomic absorption. Participants were aged 46-74 years and had mean lead levels of 3 (standard deviation, 2) micro g/dl (blood), 13 (standard deviation, 9) micro g/g (tibia), and 17 (standard deviation, 11) micro g/g (patella). In multivariate linear regression models, use of postmenopausal estrogen (inverse) and alcohol intake (positive) were significantly associated with blood lead levels. Both bone lead measures were significantly and positively associated with blood lead but only among postmenopausal women not using estrogen; for example, an increase from the first to the fifth quintile of tibia lead level (19 micro g/g) was associated with a 1.7- micro g/dl increase in blood lead (p = 0.0001) in this group. Older age and lower parity were associated with higher tibia lead; only age was associated with patella lead. The observed interaction of bone lead with estrogen status in determining blood lead supports the hypothesis that increased bone resorption, as occurs postmenopausally because of decreased estrogen production, results in heightened release of bone lead stores into blood.

Determination of gallium in soil by slurry-sampling graphite-furnace atomic-absorption spectrometry.

A graphite-furnace atomic-absorption spectrometric method, utilizing ultrasonic slurry-sampling has been developed for the determination of Ga in soils. Calibration with aqueous standards and with slurries prepared from a certified soil reference material were both employed. When calibration with soil slurries was used no modifier was needed. Because lower and more variable sensitivity was obtained for Ga in aqueous standards than for Ga in slurry soil samples, external calibration with aqueous Ga standards required a suitable chemical modifier to level out the sensitivity difference. Of the many potential modifiers tested, i.e. Al, As, Co, Mg, Mo, Ni, Pd, Pd+Mg, Se, and Te, Ni was found to be best. When Ni (1.0 mg mL(-1), 10 micro L) was injected to the graphite tube with the aqueous standards or slurry samples (10 micro L) accurate results were obtained. Both methods of calibration gave acceptable accuracy and precision. The repeatability was <or=4.6% (RSD) for slurry sampling for both methods of calibration. The intermediate precision for analyses performed on three different days was 7.3% and 4.8% when using aqueous standards and slurry standards, respectively. The limit of detection for Ga was 3.0 micro g L(-1)in soil slurry solution, equivalent to 0.08 micro g g(-1) in the soil samples. Results from slurry sampling were compared with results from microwave-digested samples. Chemical interference was observed when the acid-mixture used to dissolve the samples contained HF. This interference was eliminated when Ni was added as chemical modifier. The repeatability was <or=7.2% (RSD) for analysis of decomposed samples.