Metals In Foodstuffs Research Articles

Evaluation of 10-years French NRL proficiency tests for lead, cadmium and mercury analysis in foodstuff of animal origin

The French National Reference Laboratory (NRL) for heavy metals in foodstuffs of animal origin at the French Food Safety Agency (AFSSA) regularly organises proficiency tests schemes (PTS) focused on the quantification of the three elements lead (Pb), cadmium (Cd) and mercury (Hg), for the 23 departmental laboratories of the network of laboratories, under its responsibility. The NRL prepares test materials to promote comparability of data and support harmonisation of official analytical procedures in the case of routine analysis. When target values for the analytes are set, the PTS also provide an objective assessment and improvement of the analytical trueness in the daily work of the laboratories. The long-term performance of the network was examined using results of 10 years of PTS in various matrices from different foodstuffs of animal origin (fish, meat and milk products), with 3 different official methods, using Flame- and Electro-Thermal-AAS techniques. In all cases, participants were requested to carry out 3 independent measurements of Pb, Cd and Hg. Moreover, the assessment of the PTS was based on the Z-score approach. From 1998 to 2008, this evaluation applied to 690 results obtained in 41 PTS indicated a frequency distribution of the Z-score value for the three elements Pb, Cd and Hg of 89.2%, 94.5% and 97.7% of acceptable results, respectively. The results of this balance sheet indicated the homogeneity and ability of the laboratories network to provide comparable results of similar quality. Comparison with results obtained by a primary method were presented as complementary information to determine the interest to organize, in the future, PTS based on a certified value.

Rapid analytical method for the determination of organic and inorganic species in tomato samples through HPLC–ICP-AES coupling

A HPLC–inductively coupled plasma atomic emission spectrometer (ICP-AES) hyphenation technique was used to determine the concentration of some organic (i.e., carbohydrates, carboxylic acids) as well as inorganic (metals and anions) compounds in tomato samples. A high efficiency nebulizer (HEN) coupled to a low inner volume cyclonic spray chamber (Cinnabar) was used to interface both techniques. The HPLC–ICP-AES chromatograms for organic compounds were obtained by plotting the 193.03nm carbon emission intensity versus time. In the present work, it was also possible to obtain information about the concentration of several metals in foodstuffs. Finally, by registering the intensity at the sulphur and phosphorous emission wavelengths, the content of anions such as sulphate and phosphate was determined. In general terms, the results obtained with HPLC–ICP-AES did not differ significantly from those found with a refractive index detector. Due to the huge amount of information provided by this hyphenation, it was possible to apply it to the discrimination among different samples of native tomato cultivars.

Simultaneous Analysis of Cadmium, Lead, Mercury, and Arsenic Content in Foodstuffs of Animal Origin by Inductively Coupled Plasma/Mass Spectrometry after Closed Vessel Microwave Digestion: Method Validation

A method validation of the total analysis of cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) in foodstuffs by inductively coupled plasma/mass spectrometry (ICP/MS) after closed vessel microwave digestion is presented. Due to the lack of reference method for ICP/MS techniques in food and, based on the project of the European Committee of Normalization (CEN/TC 275/WG 10), the Agence Française de Normalisation (AFNOR) guidelines NF V03-110 were used for the evaluation of this method based on 2 steps, sample preparation and multielement detection. Several criteria considered as compulsory (linearity, specificity, precision under repeatability conditions, and trueness) have been estimated and discussed, in addition to intermediate precision reproducibility, the limit of detection, and the limit of quantification. Furthermore, a comparison with in-house methods using electrothermal atomic absorption was performed using an external proficiency testing scheme and food samples. The results indicated that this method could be used in the laboratory for the routine determination of these 4 cumulative toxic metals in foodstuffs with acceptable analytical performance.

Solid-Phase Spectrophotometry as an Efficient Method for the Determination of Heavy Metals in Foodstuffs

The complexation of some toxic elements with acid and basic dyes in the solid phase was studied. The results were used for the development of new procedures for determining trace metals in foodstuffs and potable water.

Determination of Metals in Foodstuffs by Atomic Absorption Spectrophotometry after Dry Ashing: NMKL Interlaboratory Study of Lead, Cadmium, Zinc, Copper, Iron, Chromium, and Nickel

An interlaboratory study of a method for determination of lead, cadmium, zinc, copper, iron, chromium, and nickel in foodstuffs by atomic absorption spectrophotometry (AAS) after dry ashing at 450 degrees C was conducted in 16 laboratories. The study was preceded by a practice round of familiarization samples and another round in which solutions were distributed and the metals were determined directly by AAS. The study included 5 different foods (liver paste, apple sauce, minced fish, wheat bran, and milk powder) and 2 composite diets. A single analysis was carried out on each sample. Suitable sample combinations were used as split level combinations for determination of the repeatability standard deviation. The relative reproducibility standard deviation for each of the elements ranged as follows: lead, 74-18% at 0.025-0.28 mg/kg; cadmium, 80-11% (0.002-0.51 mg/kg); zinc, 12-7% (44-72 mg/kg); copper, 47-10% (0.48-41 mg/kg); iron, 35-9% (2-228 mg/kg); chromium, 48-21% (0.008-0.22 mg/kg); nickel, 64-39% (0.025-0.39 mg/kg).

Slurry atomisation of foodstuffs in electrothermal atomic absorption spectrometry

A simple and rapid method is described for the determination of trace metals in foodstuffs. The procedure combines slurry sample introduction with an oxygen ash step that helps to remove much of the organic matrix before the atomisation stage. A thickening agent, Viscalex HV 30, is used to give stable suspensions containing 0.1–10% m/V powdered sample material and calibration is achieved by “within tube” standard additions. The method has been applied successfully to the determination of Cd, Cu and Pb in a variety of vegetable and protein foodstuffs, and Cd, Cu, Mn, Pb and Zn in single cell protein. Detection limits vary depending on the slurry concentration used and the matrix analysed, but values of 1 ng g−1 for Cd in brussel sprouts and 13 ng g−1 for Pb in liver were achieved. The effects of particle size distribution on signal precision and matrix interferences have been evaluated.

Determination of trace amounts of heavy metals in foodstuffs by anodic stripping voltammetry. Optimization of apparatus parameters

The use of differential pulse anodic stripping voltammetry in the determination of heavy metals (Cd, Pb, Cu, As) in foodstuffs was studied. Preconcentrating from solutions and dissolution took place on a thin film mercury electrode. A factorial experiment served to determine the effects of variable parameters of the apparatus, a polarographic analyzer: pulse amplitude, pulse period, and potential scan of the working electrode during dissolution. The first two parameters are significant but the scan rate is not. The apparatus parameters were optimized further by the method of response surface fitting near optimum.

Automated digestion and extraction apparatus for use in the determination of trace metals in foodstuffs.

An automated system has been constructed that uses a displacement technique to transfer foodstuffs, previously converted into a fluid state, into a modified Technicon digestor where a wet oxidation is carried out at 400 °C with the aid of sulphuric acid, nitric acid and hydrogen peroxide. The digest is pumped into a neutralisation unit where its pH is adjusted to a pre-set value and then flows into an extraction unit where the metals of interest are chelated and extracted into an immiscible organic solvent. Finally, the organic phase is separated and collected for subsequent analysis by plasma-emission spectrometry. The operation of the system is fully automatic and it processes 5–8-g samples at the rate of three per hour. Results obtained with the automatic system for the determination of iron, copper and zinc in a wide range of foodstuffs compare favourably with those obtained by manual techniques. Some preliminary results for the determination of cadmium, cobalt, nickel and lead are presented.

An atomic absorption experiment in food chemistry.

The nutritional importance of trace amounts of certain metals in foodstuffs is is well established. This undergraduate analytical service course allows students to go through the entire process of ...

Safety and legal aspects of food additives. Determination of trace amounts of metals in foodstuffs by atomic-absorption spectroscopy

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