Thierry Guérin

Optimisation of selective alkaline extraction for Cr(VI) determination in dairy and cereal products by HPIC-ICPMS using an experimental design.

This study presents the optimisation through an experimental design then the validation of a method to determine Cr(VI) in certain foodstuffs by high-performance ionic chromatography with inductively coupled plasma mass spectrometry. This method is free from interferences possibly associated with chloride and organic or inorganic carbon. Analytical performances assessed by the accuracy profile method were satisfactory in terms of linearity, specificity, sensitivity, accuracy, repeatability and intermediate precision. Limits of quantification ranged from 0.6μg.kg(-1) in dairy products to 0.8μg.kg(-1) in cereal products. The method was applied to the determination of Cr(VI) in dairy and cereal products from different brands and origins. Despite the methods very high sensitivity, Cr(VI) was not found in all the studied samples. This confirms the results of the most recent studies using an on-line speciation method, and invalidates older studies that found traces of Cr(VI) in food by using a less specific off-line speciation method.

Micropollutants and chemical residues in organic and conventional meat

The chemical contamination levels of both conventional and organic meats were assessed. The objective was to provide occurrence data in a context of chronic exposure. Environmental contaminants (17 polychlorinated dibenzodioxins/dibenzofurans, 18 polychlorinated biphenyls (PCBs), 3 hexabromocyclododecane (HBCD) isomers, 6 mycotoxins, 6 inorganic compounds) together with chemical residues arising from production inputs (75 antimicrobials, 10 coccidiostats and 121 pesticides) have been selected as relevant compounds. A dedicated sampling strategy, representative of the French production allowed quantification of a large sample set (n=266) including both conventional (n=139) and organic (n=127) raw meat from three animal species (bovine, porcine, poultry). While contamination levels below regulatory limits were measured in all the samples, significant differences were observed between both species and types of farming. Several environmental contaminants (Dioxins, PCBs, HBCD, Zn, Cu, Cd, Pb, As) were measured at significantly higher levels in organic samples.

Development and application of a method for Cr(III) determination in dairy products by HPLC–ICP-MS

This study describes the development of an analytical approach for the determination of Cr(III) in dairy products by microwave assisted extraction, complexation in situ by ethylenediaminetetraacetate (EDTA) and high performance liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). The extraction step was optimised by using an experimental design. A limit of quantification of 38µgkg-1dry weight (d.w.) was obtained whereas the bias (%) measured ranged from 10 to 18%. The repeatability and intermediate precision varied between 1.2-5.0% and 7.5-13.5%, respectively. The method was applied to the analysis of several dairy samples beforehand characterized in terms of Cr(VI) and total chromium (Crtotal). Cr(III) concentrations ranged from <13 to 255µgkg-1d.w. The results showed a good agreement between Cr(III) and Crtotal concentration levels.

Optimization and validation of the methods for the total mercury and methylmercury determination in breast milk

The objective of the work was to develop and validate methods for the total Hg and methylmercury (MeHg) in breast milk that could be further used to obtain first data on chemical contamination of French breast milk. For total Hg determination, the potential of two techniques, namely Advanced Mercury Analyzer (AMA) and ICP MS, was compared. For MeHg determination, ICP MS detection associated to a quantification by isotopic dilution was used and the potential of a preliminary separation by gas or liquid chromatography was evaluated and discussed. The optimization studies have shown that AMA for total Hg determination and HPLC - ID - ICP MS, after a preconcentration step by freeze-drying, for MeHg quantification were the most relevant methods to use for epidemiologic studies. The figures of merit for both methods were evaluated by means of accuracy profiles in terms of limits of quantification (1.82 and 1.35µg Hg/kg dry weight, corresponding to 0.22 and 0.16µg Hg/kg wet basis for total Hg and MeHg, respectively), repeatability (2-11% and 3-8% for total Hg and MeHg respectively), intermediate precision reproducibility (4-12% and 4-8% for total Hg and MeHg respectively) and trueness bias (-0.1-9% and -4-0% for total Hg and MeHg respectively). The methods were then applied to 180 breast milk samples. Total Hg concentrations ranged from <LD to 16.9µg Hg/kg wet basis (<LD to 142µg Hg/kg dry weight) and the MeHg contents from <LD to 0.43µg Hg/kg wet basis (<LD to 3.67µg Hg/kg dry weight).

Effects of pan cooking on micropollutants in meat.

This work presents the effects of pan cooking on PCBs, PCDD/Fs, pesticides and trace elements in meat from a risk assessment perspective. Three different realistic cooking intensities were studied. A GC×GC-TOF/MS method was set up for the multiresidue analysis of 189 PCBs, 17 PCDD/Fs and 16 pesticides whereas Cd, As, Pb and Hg were assayed by ICP-MS. In terms of quantity, average PCB losses after cooking were 18±5% for rare, 30±3% for medium, and 48±2% for well-done meat. In contrast, average PCDD/F losses were not significant. For pesticides, no loss occurred for aldrin, lindane, DDE or DDD, whereas losses exceeding 80% were found for dieldrin, sulfotep or phorate. Losses close to the margin of error were observed for trace elements. These results are discussed in light of the physicochemical properties of the micropollutants as well as of water and fat losses into cooking juice.

Dietary exposure to cadmium and health risk assessment in children – Results of the French infant total diet study

Besides specific occupational activities or smoking, food is the main route of cadmium exposure for the general population. In France a total diet study previously conducted for adults and children over 3 years old revealed that health concerns due to Cd dietary exposure existed for both adults and children. This study showed that the Cd tolerable weekly intake, based on potential nephrotoxicity effects, is exceeded by a high proportion of children under 3 years old. Nephrotoxicity results from the accumulation of cadmium in the kidney and appears typically after long-term exposure (40-50 years). Despite the exceeding of the tolerable weekly intake observed during the first three years of childhood, due to low body weights compared to adults, the accumulation rate of cadmium is much lower during the whole childhood period (from 0 to 17 years of age) than during adulthood. These data suggest that dietary exposure to cadmium should be reduced for both children and adults to prevent health concerns associated with nephrotoxicity in later life. Moreover, recent literature suggests that Cd can induce other adverse health effects (especially endocrine disruption or neurotoxicity) that could be triggered at even lower doses than those triggering nephrotoxicity.

Levels of lead in foods from the first French total diet study on infants and toddlers

Infants and toddlers are highly vulnerable to exposure to lead due to its higher absorption in small children than in adults. This study describes the optimisation and validation of a very sensitive method for the determination of low levels of lead in foods mostly consumed by infants and toddlers. This method, based on inductively coupled plasma-mass spectrometry with a programmable temperature cyclonic spray chamber, attained a limit of quantification (LOQ) of 0.6 or 0.9µgPbkg-1 for a liquid or a solid sample, that was improved by a factor 5.6-8.3 compared to the previous method (LOQ: 5µgkg-1). The analytical method was then applied to 291 food samples from the first French total diet study on infants and toddlers. Lead was detected in most samples at relatively low concentrations (range 0.0-16µgkg-1). The highest lead concentrations were mainly found in processed food products (e.g. products containing chocolate).

Simultaneous liquid chromatography–tandem mass spectrometry analysis of brominated flame retardants (tetrabromobisphenol A and hexabromocyclododecane diastereoisomers) in French breast milk

TBBPA and HBCDs are the two classes of flame retardants that are still allowed for use by the European Commission. In May 2013, HBCDs were listed as Persistent Organic Pollutants under the Stockholm Convention, and they were banned with an exemption on EPS/XPS for cavity wall insulation. This study describes the development and optimisation of a rapid LC-ESI-MS/MS method using isotopic dilution quantification including a simplified extraction step using a mixture of solvents and sulphuric acid hydrolysis followed by the one-shot analysis of TBBPA and each of the α-, β- and γ-HBCD diastereoisomers. The limits of detection and quantification (LOD and LOQ) were 0.5 and 2.5xa0ngxa0g-1 (lipid weight, lw) for TBBPA and HBCD diastereoisomers, respectively. The method was applied to analyse 106 samples of individual mature breast milk. TBBPA was quantified in 42% of these samples within a range of <LOQ to 15.1xa0ngxa0g-1 lw. HBCD diastereoisomers were quantified in 8%, 3% and 3% of the collected samples for α-, β- and γ-HBCDs, respectively. The α-form was predominant in each quantifiable breast milk sample. The rapid newly developed LC-MS/MS method appears to be suitable for simultaneously analysing and quantifying TBBPA and HBCDs (three isomers) in human breast milk with the aim of establishing BFR multi-contamination profiles of breast milk samples.

Extended Targeted and Non-Targeted Strategies for the Analysis of Marine Toxins in Mussels and Oysters by (LC-HRMS)

When considering the geographical expansion of marine toxins, the emergence of new toxins and the associated risk for human health, there is urgent need for versatile and efficient analytical methods that are able to detect a range, as wide as possible, of known or emerging toxins. Current detection methods for marine toxins rely on a priori defined target lists of toxins and are generally inappropriate for the detection and identification of emerging compounds. The authors describe the implementation of a recent approach for the non-targeted analysis of marine toxins in shellfish with a focus on a comprehensive workflow for the acquisition and treatment of the data generated after liquid chromatography coupled with high resolution mass spectrometry (LC-HRMS) analysis. First, the study was carried out in targeted mode to assess the performance of the method for known toxins with an extended range of polarities, including lipophilic toxins (okadaic acid, dinophysistoxins, azaspiracids, pectenotoxins, yessotoxins, cyclic imines, brevetoxins) and domoic acid. The targeted method, assessed for 14 toxins, shows good performance both in mussel and oyster extracts. The non-target potential of the method was then challenged via suspects and without a priori screening by blind analyzing mussel and oyster samples spiked with marine toxins. The data processing was optimized and successfully identified the toxins that were spiked in the blind samples.

Mercury in foods from the first French total diet study on infants and toddlers

A very sensitive method using a direct mercury analyser was developed and validated according to the accuracy profile procedure to determine mercury levels in foods mainly consumed by infants and toddlers. Total mercury was not detected (LOD of 0.30µg.kg-1 fresh weight) in 92.4% of the 291 food samples analysed or at relatively low concentrations, lesser than or equal to LB/UB 0.5/1.0µg.kg-1 in all samples, except in fish samples (mean LB/UB 25µg.kg-1 with a maximum of 53µg.kg-1). Levels of total mercury in these foods were in all cases within permitted Regulatory limits of 500 or 1000µg.kg-1 in fishery products and muscle meat of fish.