Determination of beryllium in urine by graphite-furnace atomic absorption spectrometry

A method has been developed for the determination of beryllium in urine by graphite-furnace atomic absorption spectrometry. Ammonium 12-molybdophosphate and ascorbic acid were employed as a matrix modifier. The tolerable charring temperature for beryllium in both aqueous solution and urine was raised to 1400 °C in the presence of a matrix modifier. The sensitivity for the determination of beryllium was also improved by a factor of 1.5 in comparison with that obtained by using magnesium nitrate as a matrix modifier. The mechanism of the enhancement effect of ammonium molybdophosphate was ascribed to the effectiveness of the formation of gaseous BeO, which is a precursor of free beryllium. Beryllium in urine can be determined simply by dilution with ascorbic acid solution. The relative standard deviation for seven replicate determinations of beryllium was 1.9% for a urine sample containing 0.029 μg ml^?1 of beryllium.     

Direct determination of chromium in human urine by electrothermal atomic absorption spectrometry

A rapid, accurate and direct method for urinary chromium determinations by graphite-furnace atomic absorption spectrometry is described. Few reagents are used and very little sample preparation and manipulation are required, greatly reducing the incidence of sample contamination. The method of standard additions is used to compensate for changes in sensitivity as the furnace tube ages, and for the widely different matrices encountered in urine samples. Furnace parameters must be carefully controlled. The detection limit is in the order of 0.03 ng Cr ml^-1. Agreement with independent methods is evaluated.     

Determination of chromium in human serum by electro-thermal atomic absorption spectrometry

An accurate and sensitive method for serum chromium determinations by graphite-furnace atomic absorption spectrometry is described. Samples containing a small amount of magnesium nitrate as an ashing aid/matrix modifier are lyophilized and dry-ashed in silanized quartz tubes; the residue is dissolved in 0.1 M HCl. Because of the very low levels of chromium in serum, strict contamination control measures must be used throughout the procedures for collection, storage, preparation and quantitation. Standard curves are prepared by using a bovine serum pool, which also serves as a quality control measure. The uniform nature of sera obviates the need to use the method of standard additions. The detection limit of the method is about 0.03 ng ml^?1 Cr and the accuracy of the method is evaluated by comparison with stable-isotope-dilution mass spectrometry.     

Determination of trace metals in estuarine sediments by graphite-furnace atomic absorption spectrometry

A simple and rapid acid digestion method for the decomposition of estuarine sediments is described. Quantitative recovery of Cd, Pb, Cu, Ni, Co, Be and Co is demonstrated. Sensitive, precise and accurate determination of these trace metals by graphite-furnace atomic absorption spectrometry in combination with the L'vov Platform provides an interference-free technique that permits calibration with simple aqueous solutions of metal standards. The accuracy of the method has been confirmed by analysis of two marine sediment reference materials, MESS-1 and BCSS-1.     

Determination of molybdenum, chromium and aluminium in human urine by electrothermal atomic absorption spectrometry using fast-programme methodology

Rapid and direct procedures for the determination of molybdenum, chromium and aluminium in human urine samples are developed. Fast-programme methodology is used to simplify the heating cycles. Hydrogen peroxide, nitric acid and Triton X-100 are added to the urine samples which are directly introduced into the furnace. For molybdenum, two successive injection steps are required due to the low level of this element in the samples analyzed. Calibration is carried out using aqueous standards for aluminium and the standard additions method for both molybdenum and chromium. The reliability of the procedures is checked by analyzing two certified reference materials.     

Determination of beryllium and selenium in human urine and of selenium in human serum by graphite-furnace atomic absorption spectrophotometry.

For human urine beryllium (Be), each sample (500 microl) was diluted (1+1) with Nash reagent (containing 0.2% (v/v) acetylacetone and 2.0 M ammonium acetate buffer at pH 6.0) and then a 20-microl volume of Triton X-100 (0.4%, v/v) aqueous solution was added. An aliquot (10 microl) of the diluted urine mixture was introduced into a graphite cuvette and was atomized according to a temperature program. The method detection limit (MDL, 3sigma) for Be was 0.37 microg/l in the undiluted urine sample and the calibration graph was linear up to 65.0 microg/l. Calibration graphs were prepared by the standard addition method. Accuracies of 98.6-102% were obtained when testing standard reference material (SRM 2670) freeze dried human urine samples. Precision (relative standard deviation, RSD) for urine Be was < or = 2.3% (withinrun, n = 5) and was < or = 3.0% (between-run, n = 3). For human urine and serum selenium (Se), samples (100 microl) were diluted with HNO3 (0.2%, v/v) to make a (1+1) dilution for urine analysis or a (1+4) dilution for serum analysis. An additional aliquot (10 microl) of Triton X-100 (0.1%, v/v) was added to each 200 microl of (1+1) diluted urine (or 20 microl of the Triton X-100 was added to each 500 microl of (1+4) diluted serum) sample. After the diluted sample mixture (10 microl) was introduced into a graphite cuvette, the corresponding chemical modifier (10 microl, containing Ni2+ + Pd + NH4NO3 in HNO3 (0.2%, v/v)) was added to it and the mixture was atomized. The MDL (3sigma) for Se in urine and in serum was 4.4 and 21.4 microg/l in undiluted sample, respectively, and the calibration graphs were linear up to 150 and 400 microg/l. Accuracies of urine Se were 98.9 - 99.4% by testing SRM 2670 (NIST) urine standards with RSD (between-run, n = 3) within 2.9%; and that of serum Se was 97.2% when testing a certified second-generation human serum (No. 29, #664) with RSD (between-run, n = 3) of 1.4%. The proposed method can be applied easily, directly, and accurately to the measurement of Be and Se in real samples (including six urine Se and four serum Se from patients of Blackfoot Disease in Taiwan).     

Determination of chromium in sea water by atomic absorption spectrometry

A method for the determination of chromium in sea water is described which requires minimal sample preparation. The chromium from filtered samples is oxidized with permanganate, extracted with ammonium pyrrolidine dithiocarbamate into MIBK, and analyzed by atomic absorption spectrometry in a fuel-rich air-acetylene flame. Non-filterable solids are extracted with 12 M hydrochloric acid and analyzed. Detection limits for the methods are 0.05 μg 1^-1 in the soluble phase and 0.06 μg 1^-1 in the particulate phase.     

Silica gel analysis by slurry-sampling graphite-furnace atomic absorption spectrometry

Analytical conditions for the determination of cadmium, lead, copper, iron, aluminium and titanium in commercial silica gel samples by slurry-sampling graphite-furnace atomic absorption spectrometry are established. The influence of the silica matrix on the background absorption is described. Stability tests for slurries have been carried out. Results are calculated by the method of standard additions. Statistical evaluations of the results indicate that the slurry method is reproducible and its precision is comparable to other methods used. Advantages of this method are simplicity and short time of analysis.Presented at the 5th International Colloquium on Solid Sampling with Atomic Spectroscopy, May 18–20, 1992; Geel, Belgium. Papers edited by R.F.M. Herber, Amsterdam     

Determination of aluminium and chromium in serum by atomic absorption spectrometry

Summary The optimal conditions for the determination of aluminium and chromium in blood serum are proposed. Several sample pretreatment procedures for the purpose are compared. The best results are obtained by sample dilution with nitric acid (0.1 mol/l) and addition of Mg(NO₃)₂ as modifier with a magnesium concentration of 0.2 mg/ml. This procedure has been used for studying the intestinal intake of aluminium by patients after oral administration of aluminium compounds.     

Determination of chromium, copper and lead in river water by graphite-furnace atomic absorption spectrometry after coprecipitation with terbium hydroxide.

Coprecipitation with terbium hydroxide quantitatively recovered trace amounts of chromium(III), copper(II) and lead(II) at pH 8.4 - 10.8, 8.0 - 11.5 and 8.7 - 11.5, respectively. The precipitate was dissolved in 0.85 mol dm(-3) nitric acid, and the analytes were determined by graphite-furnace atomic absorption spectrometry (GF-AAS). The presence of terbium (up to 7 g dm(-3)) did not interfere with the determination. The detection limits were 0.3 microg dm(-3) for chromium, 0.4 microg dm(-3) for copper and 0.5 microg dm(-3) for lead, when the analytes in 200 cm3 of the sample solution were concentrated into 10 cm3. The ions added to river or seawater were quantitatively recovered. Chromium and copper in a contaminated river water were successfully determined.     

Determination of ultrafiltrable zinc in human milk by electrothermal atomic absorption spectrometry.

Percentages of non-protein-bound zinc in human milk have been reported by different workers, but ultrafiltration and zinc determination in human milk have not been comprehensively examined. However, zinc contamination and zinc membrane binding have been described for the determination of non-protein-bound zinc in serum. In this work, ultrafiltration was studied in terms of zinc contamination and zinc membrane binding. An MPS-1 micropartition system fitted with a YMT membrane was used. Zinc contamination was found to be less than 276 nmol dm-3 and the zinc recovery was 85 +/- 4%. The conditions for electrothermal atomic absorption spectrometry were also studied. The detection limit was found to be 26.4 nmol dm-3 and the upper linear range was 4 mumol dm-3. The precision varied from 3% (within-run) to 17% (between-run). The recovery of standard additions was 95 +/- 7% (n = 30, different human milk ultrafiltrate samples). Physiological values varied from 0.46 to 84 mumol dm-3 (4-56% of zinc in whole human milk). Expressed in mumol dm-3, zinc in human milk ultrafiltrate decreased slightly through the lactation period, whereas expressed as a percentage of the total zinc in milk, zinc in human milk ultrafiltrate remained constant from day 2 to day 69 post partum.     

Determination of vanadium in urine by electrothermal atomic absorption spectrometry

After wet ashing of the urine sample with nitric acid, vanadium is chelated with cupferron, extracted into 4-methylpentan-2-one and determined by atomic absorption spectrometry with a pyrolytically-coated graphite furnace atomizer. The sensitivity allows the precise determination of 1–500 μg V l^-1 in urine. The coefficient of variation for triplicate urine measurements is <8% for 10 μg V l^-1.     

Determination of selenium in human milk by electrothermal atomic absorption spectrometry and chemical modification

A method was developed for the determination of selenium in human milk using electrothermal atomic absorption spectrometry. The use of chemical modifiers as well as their implications during the pyrolysis step was examined. The chemical modifiers that were studied were Zr, Ir as well as the mixed modifier Zr-Ir. The Ir modifier stabilized selenium at 1000 °C, Zr at 800 °C, while the mixed modifier at 1200 °C. The effect of modifier mass was studied and was found that better results are achieved with addition of 2 μg Zr and 2 μg Ir. The characteristic masses of selenium in the presence of Zr, Ir and the mixed modifier were found to be 73.3, 18.0 and 14.7 pg, respectively, while the corresponding limits of detection were found 2.0, 0.50 and 0.41 μg l⁻¹. Consequently better results were obtained with the mixed modifier. The developed method was applied for the determination of selenium in human milk, which was digested with a HNO₃ + H₂O₂ mixture in a microwave oven. The limit of detection of the method was 1.37 μg l⁻¹, the characteristic mass, m₀, was 48.8 pg and the repeatability was less than 5% as R.S.D.(%). Matrix matched calibration was used. Recoveries were estimated to be 93-105%. The method was applied to breast milk of Greek women (n = 9) and the Se content was found to be in the range 16.7-42.6 μg l⁻¹ with mean value 27.4 ± 5.5 μg l⁻¹.     

Determination of chromium in gallium arsenide by electrothermal atomic absorption spectrometry

The sample is decomposed with 50% (v/v) aqua regia and the diluted solution is injected into the graphite furnace. The temperature program developed minimizes non-specific background signals, so that correction is not required. For a 100-mg sample, the 3σ detection limit is 70 ng Cr g^?1. The relative standard deviation of the overall procedure is 5–7%.     

Automated direct determination of chromium in blood and urine by electrothermal atomic absorption spectrometry

A simple direct procedure for the determination of chromium in whole blood and urine by graphite-furnace atomic absorption spectrometry is described. Whole blood samples are diluted with 0.1% Triton-X solution before injection, whereas urine samples are injected directly. Calibration is done by direct comparison against matrix-matched standards. Between-run precision is 5.4% at 154 nmol l^?1 for urine and 3.6% at 142 nmol l^?1 for blood. The detection limits are 3.8 nmol l^?1 for urine and 11.5 nmol l^?1 for blood, each for a 20μl sample. The calibration range extends up to 770 nmol l^?1 for both blood and urine. This allows the determination of chromium in both occupationally exposed and unexposed groups. The graphite-furnace conditions for each matrix are similar. Elimination fo sample pretreatment minimizes the risk of contamination and allows a rapid sample throughput of 50–60 samples per day. The methods described are particularly suited for the screening and surveying of populations occupationally exposed to chromium.     

Determination of copper in milk powder by electrothermal atomic absorption and atomic emission spectrometry

Summary Electrothermal atomic absorption spectrometry (ETA-AAS) and atomic emission spectrometry (ETA-AES) have been applied to the determination of copper in powdered milk. A homogeneous dispersion procedure for the preparation of the milk powder is described which was found to be simple, rapid and less susceptible to contamination than dry ashing or wet digestion methods. Both ETA-AAS and ETA-AES techniques were found to provide satisfactory results using conventional tube wall atomisation only when the method of standard additions was employed. The application of graphite probe atomisation in ETA-AES and ETA-AAS allowed the development of direct methods for the determination of copper in milk powder using aqueous standard calibration curves. The accuracy of the probe ETA-AAS method was confirmed using new reference materials prepared by the EEC Community Bureau of Reference. Acceptable agreement was obtained for the other procedures using a commercial milk powder sample with a copper content of 6.0g g^–1.     

Determination of manganese in serum and urine by electrothermal atomic absorption spectrometry

Manganese is determined in serum and urine by graphite-furnace atomic absorption spectrometry after dilution (1 + 1) with distilled water. Simple aqueous standards are used for calibration. Background absorption from the matrix is decreased by attention to the heating programme, sample dilution and gas flow-rate during atomisation. Remaining background absorption is removed by a deuterium-arc background correction system. To obtain accurate results, great care is needed in collecting samples to avoid contamination. Blood is collected through a plastic cannula, because stainless steel needles introduce considerable contamination. The mean normal concentration of manganese in serum was found to be 0.58 μg l^?1 (it- = 9) which is in agreement with other literature values. For urine, the mean normal concentration found was 0.7 μg l^?1 (it- = 16). Patients on total parenteral nutrition with manganese supplements show elevated serum and urine manganese concentrations.     

Determination of silver in sea water by coprecipitation with cobalt pyrrolidinedithiocarbamate and Zeeman graphite-furnace atomic absorption spectrometry

A preconcentration technique is described for silver, which allows the precise and accurate determination of silver in sea water at nanogram per liter levels. Silver is co-precipitated with cobalt(II) pyrrolidinedithiocarbamate from 200-ml samples. The precipitate is dissolved in concentrated nitric acid and silver is quantified by Zeeman graphite-furnace atomic absorption spectrometry, with acid phosphate matrix modification. The detection limit is 0.1 ng l^?. The method is simple and rapid, and also allows the simultaneous extraction of lead, copper, cadmium, and nickel.     

Determination of cobalt and nickel by graphite-furnace atomic absorption spectrometry after coprecipitation with scandium hydroxide.

Trace amounts of cobalt and nickel in a water sample were quantitatively coprecipitated with scandium hydroxide at pH 8.0-10.5. Because the coprecipitant could be easily dissolved with 1 mol dm(-3) nitric acid, and the presence of up to 10 mg cm(-1) of scandium did not interfere with the graphite-furnace atomic absorption spectrometric determination of cobalt and nickel, the volume of the final solution prepared for the determination could be minimized down to 0.5 cm3. The concentration factor was 400-fold and the detection limits (signal to noise = 2) were 5.0 pg cm(-3) of cobalt and 10.0 pg cm(-3) of nickel in 200 cm3 of the initial sample solution. The 27 diverse ions investigated did not interfere with the determination in at least a 500-fold mass ratio to cobalt or nickel. The proposed method was successfully applied to the determination of trace amounts of cobalt and nickel in river-water samples.