Gordon S. Fell

Environmental exposure to metals of newborns, infants and young children

Anthropogenic emissions, such as those from combustion of fossil fuel, waste incineration and industrial use, contribute to higher levels of metal pollutants, including Cd, Pb and Sb, in the urban environment. These widespread and persistent environmental pollutants have the potential for developmental and reproductive toxicity. Health risks are particularly associated with exposure in utero and the early years of life, since the developing organism is at greater risk from permanent damage, and both absorption and retention can be considerably greater in infants than adults. In order to assess risk to humans, the information on environmental levels of pollutants (environmental monitoring) should be integrated with information on biomarkers of exposure, effect or susceptibility in biological fluids or tissues (biological monitoring). The analysis of tissue from the target organ obtained at autopsy provides a direct record of the accumulation of toxins and allows temporal and geographical trends to be studied. Few literature reports on tissue content of potentially toxic elements include data on newborns and young children since collections of autopsy samples in this age range are rare. Existing data are sometime questionable, because of inadequate sensitivity of the analytical techniques, insufficient control of contamination and lack of validation. Our recent work aimed to establish reliable reference values for the content of Cd, Pb and Sb in the liver of pediatric subjects.

Evaluation of inductively coupled argon plasma mass spectrometry (ICP-MS) for simultaneous multi-element trace analysis in clinical chemistry

The suitability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of trace amounts of inorganic elements in clinical samples has been investigated. Protein solutions, which were known to be free from biohazards, were obtained in sufficient amounts to allow the preparation of three pools of material of differing trace metal content. Freeze-dried portions were distributed to four different laboratories with established expertise in trace element analysis.The elements Mg, Al, Cr, Mn, Fe, Ni, Cu, Zn and Se as determined by ICP-MS showed reasonable agreement with the values obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES), simultaneous multi-element atomic absorption continuum source (SIMAAC) spectrometry and by established flame and graphite furnace atomic absorption spectrometry (FAAS and GFAAS) procedures.A commercial source of freeze-dried urine with assigned values for a range of trace elements was analysed by ICP-MS. Acceptable results were obtained for elements with mass numbers greater than 81 (e.g., Pb, Cd, Hg and Tl). However, with the exception of Co, results obtained for the first row transition elements, as well as for As and Se, were severely degraded by polyatomic interferences. Acid digests of dried bovine liver (NBS SRM 1577) were also analysed by ICP-MS and acceptable agreement with the certified values found for Mn, Fe, Cu, Co, Rb, Zn, Sr and Mo. Modification of the sample preparation procedure by precipitation of chloride prior to analysis by ICP-MS has been found to offer advantages for some elements.

Determination of aluminium in blood plasma or serum by electrothermal atomic absorption spectrometry

Abstract A carbon-furnace atomic absorption method is used to determine aluminium in blood serum or plasma, diluted (1 + 2) with purified water prior to injection (20 μl) into the furnace. Procedures are described to reduce contamination during sample collection, storage and preparation of samples. A study of the interferences of inorganic ions shows that the temperature programme developed minimises these, allowing the use of aqueous standards for calibration. Ashing at 1400°C, prior to atomisation, also removes non-specific background effects, and optical correction is not required. A sample throughput of 50 duplicate analyses per day is possible and the precision (between batch) at 24 μg Al l-1 was 11.2% (n = 10) and at 340 μg Al l-1 was 6.3% (n = 18). Down to 4 μg Al l-1 can be determined. Reference values for a healthy population were 4.1–20 μg Al l-1 (mean 10.2).

Cadmium concentrations in human kidney in the UK: 1978-1993

Almost 2700 samples of human renal cortex have been collected from throughout the UK over a 16 year period from 1978 to 1993. The mean Cd concentration was 19 micrograms g-1 and the median 16 micrograms g-1. Smokers were, on average, about 5 micrograms g-1 higher than non-smokers. Cd increased from low concentration in the young to a maximum of 23 micrograms g-1 in middle age followed by a decrease in old age. Subjects who had died of renal disease had lower Cd concentrations. Geographical variations in the UK are small and the concentrations appear to be static over the 16 year period. Some 3.9% of the population had Cd concentrations > 50 micrograms g-1, the critical level at which beta 2-microglobulin appears in urine.

Determination of selenium in human hair and nail by electrothermal atomic absorption spectrometry

A microwave digestion procedure was used to prepare samples for determination of total Se by electrothermal atomic absorption spectrometry (ETAAS) with palladium modification. Conversion of organoselenium compounds to inorganic selenium was achieved by heating 100 mg hair with 0.5 ml concentrated nitric acid for 1 min and then, after the addition of 0.5 ml hydrogen peroxide (30 vols.), reheating for a further 8 min. The accuracy of the method was confirmed by analysis of certified hair reference materials containing 2.00 and 0.58 µg g–1 Se. The detection limit is 0.02 µg g–1 Se. A variation of the procedure was used to analyse nail samples. Digestion was achieved by heating 100 mg of nail with 1 ml nitric acid for 2 min and, after the addition of 1 ml hydrogen peroxide, for a further 33 (3 × 11) min. The detection limit for this procedure is 0.03 µg g–1 Se. Analysis of hair reference materials and both hair and nail samples by neutron activation analysis and ETAAS showed reasonable agreement between the techniques. The ETAAS procedure is more rapid and convenient. Analysis of 25 hair samples gave a range of 0.31–0.76 µg g–1 Se (mean value 0.52 ± 0.11 µg g–1) and for 27 nail samples a range of 0.17–0.66 µg g–1 Se (mean value 0.46 ± 0.16 µg g–1) was obtained.

Elimination of chloride interference on the determination of selenium in serum by inductively coupled plasma mass spectrometry

The presence of chloride ions in sample solutions may cause interferences in the determination of certain elements (particularly V, Cr and As) by inductively coupled plasma mass spectrometry (ICP-MS). This may be problematic in clinical samples such as tissue, protein and urine where the measurement of elements, present at physiologically active levels, can be impaired by these spectral interferences. A procedure is described whereby a chromatographic separation is employed to de-salt serum samples, rendering a sample solution free of chloride. Using this procedure, ICP-MS can be used to measure the Se content of serum solution accurately without interference.

Determination of aluminium in dialysate fluids by atomic-absorption spectrometry with electrothermal atomisation

Matrix effects in the determination of aluminium in dialysate fluids by electrothermal atomic-absorption spectrometry are overcome by the addition of nitric acid (to give a final concentration of 2%V/V) to the fluid. Analyses may be made by a rapid two-step heating programme giving a total time per injection of 59 s; in the first step, drying and ashing are combined. A detection limit of 1 µg l–1 is achieved and reproducibility is better than 2% in the range 30–120 µg l–1. Concentrations of aluminium of <1–11 µg l–1 were determined in various batches of commercially supplied peritoneal dialysis fluid. Haemodialysate fluid concentrations varied from <1 to 31 µg l–1 with 62% of the samples examined having concentrations less than 5 µg l–1.

Factors influencing lead concentrations in shed deciduous teeth

Data collected for the Edinburgh Lead Study have been used to investigate lead concentrations in childrens naturally shed deciduous teeth. A within-child multiple-regression analysis has shown that the upper jaw has a higher concentration of lead than the lower, and that there is a gradient of decreasing concentration from the front to the back of the mouth. Even after the effects of jaw and tooth type have been allowed for, the concentration is still found to be negatively correlated with the weight of the tooth and with the age at which the tooth was shed. No statistically significant effects could be attributed to caries, fillings, or the incomplete resorption of roots. A single-valued index of tooth lead has been derived for each child, taking into account the fact that children gave different types of teeth.

Improved molecular fluorescence method for the determination of selenium in biological samples

A procedure for the determination of selenium in whole blood and urine has been improved by optimization of the digestion and derivatization procedures. An overnight pre-digestion step with 4 + 1 concentrated nitric-perchloric acids reduced the time of mineralization at 170 degrees C from 4 h to 30-45 min. Conversion of all the selenium to selenite (SeIV) was optimized by addition of 1 ml of concentrated hydrochloric acid, with heating to 100 degrees C for 30 min. The rate of formation of the 2,3-diaminonaphthalene (DAN) complex of selenium was improved by heating to 70-100 degrees C for a minimum of 30 min. Co-addition of hexane during derivatization simplified the extraction procedure. The modified method was applied successfully to the analysis of Seronorm quality control whole blood and urine (83 and 24 micrograms l-1 Se, respectively). Samples from 12 healthy adults, gave results in expected ranges (mean concentrations of 75 +/- 8 micrograms l-1 in blood and 25 +/- 8 micrograms l-1 in urine). The structure of the Se-DAN complex was investigated using elemental analysis, FTIR spectrometry, 1H and 13C NMR spectroscopy, and FAB MS. The information obtained indicates that the selenodiazo group does not contain an Se-O bond or protonated nitrogens, as proposed in other studies.

Direct determination of cadmium in urine by electrothermal atomisation atomic absorption spectrometry

Omission of the ashing stage in the determination of chromium in urine by electrothermal atomisation atomic absorption spectrometry (ETA-AAS) led to an increase in the background absorbance, but the values found were still within a range which a deuterium-arc background correction system is capable of correcting. Rapid three-stage furnace programmes omitting the ashing stage were developed for two systems: one for an instrument with deuterium-arc background correction using an uncoated tube and the other for a Zeeman-effect system using a pyrolytically coated tube. Cycle times of 53 and 70 s, respectively, were achieved for these methods which were developed for monitoring occupational exposure. Small matrix effects were overcome by adding a surfactant, Triton X-100, to the diluent. Samples and standards were diluted 1 + 1 with 1%V/V HNO3 and 0.25%V/V Triton X-100. Results obtained by the two methods agreed well (r= 0.997) and also with those obtained by a slower method using an ashing stage (r= 1.000). It was concluded that Zeeman-effect background correction was unnecessary for this determination and that faster and more precise results could be obtained with the simpler system using deuterium-arc background correction.