Malcolm Baxter

1997 UK Total Diet Study dietary exposures to aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc

Concentrations of aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc were determined in samples from the 1997 UK Total Diet Study and used to estimate dietary exposures of the general UK population. Population average dietary exposures to aluminium (3.4mg/day), arsenic (0.065mg/day), cadmium (0.012mg/day), chromium (0.10mg/day), copper (1.2mg/day), mercury (0.003mg/day), nickel (0.13mg/day), tin (1.8mg/ day) and zinc (8.4mg/day) are similar to those from previous UK Total Diet Studies and are below the appropriate PTWIs, PMTDIs and TDIs. Dietary exposure of the UK population (0.026 mg/day) to lead is falling as a result of measures taken to reduce lead contamination of the environment and food and is well below the PTWI. There has been little change in UK estimates of selenium exposure since the 1994 Total Diet Study but current estimates (0.039mg/day) are lower than those derived from earlier Total Diet Studies.

Dietary exposure estimates of 30 elements from the UK Total Diet Study

Dietary exposures of consumers to 30 elements (aluminium, antimony, arsenic, barium, bismuth, boron, cadmium, calcium, chromium, cobalt, copper, germanium, gold, iridium, iron, lead, lithium, manganese, mercury, molybdenum, nickel, palladium, platinum, rhodium, ruthenium, selenium, strontium, thallium, tin and zinc) estimated from the UK 1994 Total Diet Study are reported, and compared with those from previous UK Total Diet Studies and those from other countries. Dietary exposure estimates were generally low and, where comparisons are possible, similar to those from other countries and below the relevant Provisional Tolerable Weekly Intakes and Provisional Maximum Tolerable Daily Intakes. For most of those elements included in previous UK Total Diet Studies, dietary exposures have declined.

Isotopic and Elemental Data for Tracing the Origin of European Olive Oils

H, C, and O stable isotope ratios and the elemental profile of 267 olive oils and 314 surface waters collected from 8 European sites are presented and discussed. The aim of the study was to investigate if olive oils produced in areas with different climatic and geological characteristics could be discriminated on the basis of isotopic and elemental data. The stable isotope ratios of H, C, and O of olive oils and the ratios of H and O of the relevant surface waters correlated to the climatic (mainly temperature) and geographical (mainly latitude and distance from the coast) characteristics of the provenance sites. It was possible to characterize the geological origin of the olive oils by using the content of 14 elements (Mg, K, Ca, V, Mn, Zn, Rb, Sr, Cs, La, Ce, Sm, Eu, U). By combining the 3 isotopic ratios with the 14 elements and applying a multivariate discriminant analysis, a good discrimination between olive oils from 8 European sites was achieved, with 95% of the samples correctly classified into the production site.

Elements in rice from the Swedish market: 1. Cadmium, lead and arsenic (total and inorganic)

A survey of the levels of cadmium, lead and arsenic in different types of rice available on the Swedish retail market was carried out in 2001–03. The types of rice included long and short grain, brown, white, and parboiled white rice. The mean levels found were as follows: total As: 0.20 mg kg−1, inorganic As: 0.11 mg kg−1; Cd: 0.024 mg kg−1; and Pb: 0.004 mg kg−1. ICP-MS was used for the determination of As (total and inorganic) after acid digestion. Lead and cadmium were determined using graphite furnace atomic absorption spectrometry (GFAAS) after dry ashing. In countries where rice is a staple food, it may represent a significant contribution in relation to the provisional tolerable weekly intake for Cd and inorganic As.

Bromine and iodine in 1997 UK total diet study samples

Concentrations of bromine and iodine were analysed in samples from the 1997 UK Total Diet Study (TDS) using ICP-MS. The data has been used to estimate dietary exposures of UK consumers to these elements from the typical UK diet. Samples for the 20 TDS food groups were obtained from 20 towns in the UK in 1997 and analysed in 1998/99 for total bromine and total iodine concentrations. These samples were also analysed for 12 other elements. The UK regulatory authority had considered iodine recently, but had not considered bromine before. This survey provides up-to-data baseline data for those two elements. Iodine concentrations are similar to those found in recent surveys. Levels of bromine were consistent with previous data where available. Dietary exposures to bromine and iodine were calculated to see if there were any risks to health from the levels of these elements found in the UK diet. The estimated population average exposure to iodine was 0.25 mg d-1, which is within the range of previous estimates (1995, 0.21 mg d-1; 1991, 0.17 mg d-1; 1985, 0.28 mg d-1). The estimated population average exposure to bromine was 3.6 mg d-1.

A review of analytical methods for lead, cadmium, mercury, arsenic and tin determination used in proficiency testing

The methods used by laboratories participating in FAPAS® proficiency testing covering trace metals have been reviewed. Techniques that tend to give the highest percentage of satisfactory z-scores are identified. Comparisons are made of digestion and extraction techniques, use of atomic absorption spectrophotometry (AA: graphite furnace and flame) and inductively coupled plasma techniques (ICP-OES and ICP-MS). It does not follow that one technique is more accurate than the others, because some individual laboratories consistently achieve satisfactory results using any of the five main digestion techniques and any of the major detection techniques. The results do, however, give an indication of which techniques are easier to perform correctly and with a high standard of accuracy. There are also other factors that may influence results such as instrument set-up, background correction and data analysis.

On-line removal of interferences in the analysis of biological materials by flow injection inductively coupled plasma mass spectrometry

A method of matrix elimination was developed that facilitates the interference-free determination of the trace metals vanadium, manganese, copper, zinc, cadmium and lead in biological matrices by inductively coupled plasma mass spectrometry. The method involves chelation of the analytes onto an iminodiacetate-based resin in a microcolumn with simultaneous matrix removal. The analytes are then eluted into the spectrometer with 3 mol l–1 nitric acid using a flow injection procedure. Analysis of certified reference materials yielded results in reasonable agreement with the certified values. Recovery tests showed close to 100% recoveries for manganese, copper, cadmium and lead, 90% recovery for vanadium and 85% recovery for zinc. The limit of detection (3σ) for these analytes using a 175 µl sample loop ranged from 0.6 to 9.9 ng ml–1i.e., from 75 to 1800 pg or from 50 to 825 µg kg–1 dry mass of sample. The same chromatographic system was applied to chromium determinations, but proved unsuccessful.

Levels of phytoestrogens, inorganic trace-elements, natural toxicants and nitrate in vegetarian duplicate diets

Abstract Vegetarian duplicate diets were collected in summer (16) and winter (19) and were analysed for the levels of 13 phytoestrogens, nitrate, 12 trace elements, two glycoalkaloids and three furanocoumarins. Phytoestrogens were analysed by paired hydrolysed and non-hydrolysed assays. The mean total isoflavone concentration in diets, without hydrolysis, was 14 mg kg −1 in summer and 15 mg kg −1 in winter, corresponding to an overall hydrolysed aglycone concentration of 10 mg kg −1 . The tin concentration was higher in winter than in summer diets at 4.6 and 2.2 mg kg −1 . The nitrate concentration was 51 mg kg −1 in summer and 45 mg kg −1 in winter. The furanocoumarins psoralen, xanthotoxin and bergapten were present at a combined average concentration of 0.075 mg kg −1 . The glycoalkaloid α-chaconine was observed in only one sample at 14 mg kg −1 with an LOD of 0.8 mg kg −1 . Only minor compositional differences were observed between the summer and winter diets. Daily intakes were calculated and these values were compared with existing compositional data on food and with the appropriate recommended safe exposure levels. For isoflavones a mean aglycone equivalent intake of 10.5 mg day −1 was calculated. The mean tin intake was significantly higher in winter than in summer at 5.5 and 2.1 mg day −1. Nitrate intake from these diets was 53 mg day −1 , if the theoretical liquid portion of diet were considered, the resulting estimated total of 84 mg day −1 is similar to that of the UK average. Other than an increase in tin intake during winter, exposure of vegetarians to individual phytoestrogens, natural toxicants and inorganic trace-elements was comparable to that of the general population. No individual level of any analyte in any single diet sample exceeded recommended intake levels.

Reduction of polyatomic interferences in inductively coupled plasma mass spectrometry by selection of instrumental parameters and using an argon–nitrogen plasma: effect on multi-element analyses

The effect of instrumental parameters and argon-nitrogen plasmas on polyatomic ion formation has been studied in order to reduce their magnitude in routine multi-element analysis without losing detection capability. Special emphasis was placed on the chlorine based polyatomic interferences on V, Cr, Zn, As and Se. A significant reduction in signals from polyatomic ions was attained by using a high aerosol carrier gas flow rate (0.955 l min–1) instead of the default flow rate (0.755 l min–1), or by adding nitrogen (8%) to the aerosol carrier flow. The ArCl+ interference produced by 0.05% Cl (the maximum concentration expected in digested food stuff samples) was effectively removed by both methods and ClO+ and ClO2+ by addition of nitrogen. Detection limits for elements along the mass range (from Li to U) were, on average, 2–3 times higher with the mixed gas plasma. This slight degradation of detection limits was not judged to be deterimental to multielement determinations in five reference materials when the results from using an argon-only plasma (with low and high aerosol carrier flow rates) were compared with the results from the argon–nitrogen plasma.

Absorption of selenium from wheat, garlic, and cod intrinsically labeled with Se-77 and Se-82 stable isotopes.

There is limited information on the absorption of selenium from different foods in humans because of technical difficulties associated with isotopic labeling of dietary selenium. Wheat, garlic, and cod fish were intrinsically labeled with Se-77 or Se-82 stable isotopes. Labeled meals were fed in random order to 14 adults, with a minimum washout period of six weeks between each test meal. Apparent absorption was measured as luminal loss using a fecal monitoring technique over an 8-day period. Plasma appearance of the isotope was measured at 7, 24, and 48 hours post-ingestion. Selenium absorption (+/- SD) was significantly higher (p < 0.001) from wheat (81.0 +/- 3.0%) and garlic (78.4 +/- 13.7%) than from fish (56.1 +/- 4.3%). Lowest plasma concentration was observed after the fish meal at all three time points, with a peak at 24 hours, whereas wheat produced the highest plasma concentration at all three time points and peaked at 7 hours. Selenium absorption from wheat and garlic was higher than from fish, and inter-individual variation was low. Form of selenium and food constituents appear to be key determinants of post-absorptive metabolism.