M.L. Cervera

A review of non-chromatographic methods for speciation analysis.

This manuscript overviews relevant scientific literature concerning speciation of trace elements by using non-chromatographic methods. The main principles of the different strategies proposed in the published works and their advantages and drawbacks are discussed in order to provide to the readers an appropriate picture of the state-of the-art of fast and cheap methodologies available to obtain information about the presence of different chemical forms of trace elements in environmental, clinical and food samples. A selection of the methods proposed for the speciation of the different elements studied was also provided together with their main features.

Rapid and quantitative release, separation and determination of inorganic arsenic [As(III)+As(V)] in seafood products by microwave-assisted distillation and hydride generation atomic absorption spectrometry

A precise, simple and rapid method is described for the determination of inorganic arsenic [As(III)+As(V)] in seafood products. The inorganic species were isolated from the matrix by microwave-assisted distillation and determined by hydride generation atomic absorption spectrometry (HGAAS). The microwave and chemical parameters were optimized in order to obtain quantitative inorganic arsenic recoveries. The analytical features of the method are as follows: detection limit 10 ng g –1 (dry mass) or 2 ng g –1 (fresh mass); precision (RSD) 4%; recoveries 106±3% for As(III) and 113±4% for As(V). Under the optimized conditions, arsenobetaine, arsenocholine and tetramethylarsonium ion added to samples of seafood were not distilled; however, minor species were distilled and were detected in various percentages: 109% monomethylarsonic acid; 11% dimethylarsinic acid; 0.2% trimethylarsine oxide. The concentrations expressed as arsenic contributed by these species would imply a mean overestimate of inorganic arsenic of about 24 ng g –1 dry mass (dm). The concentrations of inorganic arsenic found in natural seafood samples ranged between 0.053 and 1.145 µg g –1 (dm) (mean moisture content 78%). The procedure was compared with an alternative methodology in which acid digestion-solvent extraction-HGAAS was used for the determination of inorganic arsenic. A Students t-test for paired samples of the data obtained by the two methodologies showed no significant differences (P-value 0.66).

Chemometric determination of arsenic and lead in untreated powdered red paprika by diffuse reflectance near-infrared spectroscopy.

It has been evaluated the potential of near-infrared (NIR) diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) as a way for non-destructive measurement of trace elements at microg kg(-1) level in foods, with neither physical nor chemical pre-treatment. Predictive models were developed using partial least-square (PLS) multivariate approaches based on first-order derivative spectra. A critical comparison of two spectral pre-treatments, multiplicative signal correction (MSC) and standard normal variate (SNV) was also made. The PLS models built after using SNV provided the best prediction results for the determination of arsenic and lead in powdered red paprika samples. Relative root-mean-square error of prediction (RRMSEP) of 23% for both metals, arsenic and lead, were found in this study using 20 well characterized samples for calibration and 13 additional samples as validation set. Results derived from this study showed that NIR diffuse reflectance spectroscopy combined with the appropriate chemometric tools could be considered as an useful screening tool for a rapid determination of As and Pb at concentration level of the order of hundred microg kg(-1).

Determination of inorganic arsenic in seafood products by microwave-assisted distillation and atomic absorption spectrometry

A precise and accurate procedure is proposed for the determination of inorganic As in seafood products by employing microwave-assisted distillation and atomic absorption spectrometry (AAS). The effect of the amount of HCl, the prior reduction of AsV to AsIII and the different parameters that control the distillation of AsCl3 were studied. Organoarsenic compounds are not decomposed by the microwave-assisted distillation procedure. The inorganic As was determined by hydride generation AAS. The methodology developed has a detection limit of 0.068 µg g–1(dry mass) or 0.023 µg g–1(wet mass) of mussel product, and a relative standard deviation of 9%. The percentage recovery for AsIII was 97 ± 3% and for AsV, 100 ± 3%. The proposed procedure has been applied to the analysis of real samples of seafood products, in which the total As was also determined by inductively coupled plasma atomic emission spectrometry.

Comparison of dry mineralization and microwave-oven digestion for the determination of arsenic in mussel products by platform in furnace Zeeman-effect atomic absorption spectrometry

Two digestion procedures were compared in order to obtain an accurate method for the determination of As in mussel products using platform in furnace Zeeman-effect atomic absorption spectrometry. One procedure was based on dry mineralization of the samples and the other on microwave-oven sample digestion in closed polytetrafluoroethylene reactors. Microwave-oven digestion with HNO3 and H2O2 allows the accurate determination of As in certified oyster and mussel tissue samples and provides results comparable to those found by dry mineralization of real mussel product samples, with a sensitivity of 3.9 absorbance units per µg ml–1 and a relative standard deviation of 5% in the analysis of samples containing 8 µg g–1 dry mass of As. Experimental conditions for the determination of As in real samples were optimized and a series of real samples analysed in order to determine the analytical characteristics of the proposed procedure. Sample treatment time was reduced from 2–3 d using dry mineralization, to 20 min per sample using microwave-oven digestion.

Elemental composition of seasoning products.

The elemental composition of seasoning products, like spices garlic and onion, has been reviewed paying special attention to methods proposed in the literature to determine specific elements or as much as possible components of these products which are widespread used in food preservation or food flavouring and can contribute to the intake of both, essential and toxic elements. Sample treatment and metal speciation aspects have been critically revised concerning onion, garlic and pepper (the most commonly studied products).

Critical review of the atomic spectrometric analysis of arsenic in foods

The literature on the determination of arsenic in foods by atomic spectroscopy involving hydride generation, platform furnace Zeeman and inductively coupled plasma has been critically reviewed. Hydride generation has been largely displaced as a powerful tool by platform furnace Zeeman, using the STPF (stabilized temperature platform furnace) concept for the control of interferences. Inductively coupled plasma with conventional pneumatic nebulization has been little used. An alternative is to employ hydride generation-ICP with extraction of the arsenic in an organic phase. This technique permits proper control of interferences together with an increase in sensitivity. Depending on the contents present in the foodstuff and the technique available, the sample can be solubilized by either wet or dry digestion.

Determination of inorganic species of Sb and Te in cereals by hydride generation atomic fluorescence spectrometry

Neste trabalho foi desenvolvido um sistema nao cromatografico rapido, sensivel e simples para a determinacao de Sb(III), Sb(V), Te(IV) e Te(VI) em amostras de cereais. O procedimento baseia-se na extracao assistida por ultra-som e na determinacao por espectrometria de fluorescencia atomica acoplada com geracao de hidretos (HG AFS). Foram realizados estudos preliminares com o intuito de avaliar a eficiencia da extracao usando 1 mol L-1 acido fosforico, 1 mol L-1 acido nitrico, agua regia, 1 mol L-1 acido sulfurico e 6 mol L-1 acido cloridrico. A extracao com agua regia apresentou uma evidente interconversao das especies durante o processo. No entanto, o H2SO4 apresentou-se como o melhor agente de extracao com eficiencias maiores do que 90% em relacao ao conteudo total de Sb e Te (ambos os elementos foram previamente quantificados), nao apresentando interconversao nenhuma. Estudos de recuperacao para diferentes niveis de adicao das especies comprovaram a nao interconversao das especies. O metodo forneceu limites de deteccao na faixa de 0,1 a 1,0 ng g-1 com desvios padrao relativos de 5,4-9,2% para 10 analises independentes de amostras que continham baixas concentracoes de especies de Sb e Te.

Authentication of Alicante's Mountain cherries protected designation of origin by their mineral profile.

Chemometric analysis of inductively coupled plasma optical emission spectroscopy (ICP-OES) data was employed to verify the origin of cherry samples of different areas of Spain: Aragón, Cáceres, Castellón, Huesca and Alicantes Mountain Protected Geographic Indication (PGI). The ability of multivariate analysis methods, such as discriminant analysis (DA), was used to achieve cherry classification from their mineral content. The study was performed using 22 variables (concentrations of Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Sr, Ti and Te) and 23 variables (concentrations of Al, As, B, Ba, Be, Bi, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mo, Na, Ni, Pb, Se, Sr, Ti, Tl and V), for cherry stone and edible part, respectively, and the best discrimination was found on using edible part mineral composition which permits a correct classification of 100% of the considered samples.

Fast determination of fish mineral profile. Application to Vietnamese panga fish.

A methodology, based on inductively coupled plasma optical emission spectrometry after microwave-assisted digestion with HNO3/H2O2, was developed to determine the mineral profile of panga fish samples imported from Vietnam. A total of 42 essential and toxic elements were studied in seven samples taken from the local market. Preliminary studies were focused on selecting the best wavelength and the required dilution of samples in order to provide the highest sensitivity to maximize the number of analytes to be determined without spectral or matrix interferences. Adequate accuracy was assured by the analysis of certified reference material TORT-2. Mercury was also determined by a direct method based on atomic absorption spectrometry. Results obtained indicated a low mineral profile, fourteen elements were found at quantitatively levels, Na (6000 µg g(-1)) K (1800 µg g(-1)) Mg (173 µg g(-1)), Ca (80 µg g(-1)), Zn (2.44 µg g(-1)), Fe (1.6 µg g(-1)), Al (1.1 µg g(-1)), Sr (0.4 µg g(-1)) and B, Ba, Hg, Mn, V (under 0.1 µg g(-1)). Additionally data were compared with those previously reported in literature and an estimation of daily intake was calculated and compared with recommended or tolerable guidelines values. Levels of As, Cd, Pb and Hg were far below the established values by the European Community.