Marianela Savio

Multielemental analysis in vegetable edible oils by inductively coupled plasma mass spectrometry after solubilisation with tetramethylammonium hydroxide.

Trace metals have negative effects on the oxidative stability of edible oils and they are important because of possibility for oils characterisation. A single-step procedure for trace elemental analysis of edible oils is presented. To this aim, a solubilisation with tetramethylammonium hydroxide (TMAH) was assayed prior to inductively coupled plasma mass spectrometry detection. Small amounts of TMAH were used, resulting in high elemental concentrations. This method was applied to edible oils commercially available in Argentine. Elements present in small amounts (Cu, Ge, Mn, Mo, Ni, Sb, Sr, Ti, and V) were determined in olive, corn, almond and sunflower oils. The limits of detection were between 0.004 μg g(-1) for Mn and Sr, and 0.32 μg g(-1) for Sb. Principal components analysis was used to correlate the content of trace metals with the type of oils. The two first principal components retained 91.6% of the variability of the system. This is a relatively simple and safe procedure, and could be an attractive alternative for quality control, traceability and routine analysis of edible oils.

On-line flow injection solid phase extraction using oxidised carbon nanotubes as the substrate for cold vapour-atomic absorption determination of Hg(II) in different kinds of water

A study was carried out to investigate the concentrations of Hg(II) in different categories of water samples at ng L−1 levels. The capabilities of oxidised carbon nanotubes (ox-CNTs) were studied to assess if this substrate serves as an efficient material for Hg(II) preconcentration using an on-line flow injection cold vapour-atomic absorption spectrometry (FI-CV-AAS) system. Carbon nanotubes are characterized by a marked tendency to aggregate, which negatively affects the retention of Hg whenever integrated in flow systems as a packed column. For this reason, the preconcentration was carried out in a microcolumn filled with a mixture of ox-CNTs and a low molecular weight polyethylene. The preparation of the microcolumn was studied in detail. Concerning column design, the best performance was achieved when packing the substrate in a microcolumn of 2.25 mm (i.d.) × 20 mm length. The effect of chemical and physical parameters including the pH of the solutions, the eluent type and the concentration was systematically examined. Mercury was retained at pH 5.0 and 15% (v/v) HCl was the best alternative for Hg(II) elution. Under optimal conditions, the adsorption capacity of the substrate was found to be 3.2 mg g−1 reaching a preconcentration factor (PF) of 150. The high adsorption capacity of this substrate allowed reaching a detection limit (3σ) of 1.9 ng L−1, when using a sorbent column containing only 1.0 mg of ox-CNTs. The limit of quantification (10σ) resulted to be 6.3 ng L−1. Precision, expressed as relative standard deviation (RSD), turned out to be 1.6% at the 0.1 μg L−1 level (n = 8). The system was evaluated for quantitative determination of Hg in river water, sea water and effluents.

Optimization of methods to assess levels of As, Bi, Sb and Se in airborne particulate matter by FI-HG-ICP OES

A study was undertaken to assess the level of selected trace elements namely, As, Bi, Sb and Se in airborne particulate matter collected on ash-free glass-fibre filters from urban and industrial areas of Argentina. For sample digestion, a simple acid treatment with HCl + HF is proposed with the aim to minimize contamination and reduce sample treatment steps. A flow injection-hydride generation system in combination with inductively coupled plasma optical emission spectrometry was used. While, Se and Bi could be determined directly from the digest, As and Sb needed a pre-reduction with KI, and H3BO3 to avoid the interference of F− ions that may cause losses via volatile compounds such as AsF3 and Sb(V) complexes. Limits of detection (3σ) of 0.3 ng m−3 for As; 0.09 ng m−3 for Bi, and 0.1 ng m−3 for Sb and Se were achieved. Precision resulted in better than 6.1% accuracy for all the elements determined. Accuracy test was assessed by means of the certified reference material, NIST 1648 (urban particulate matter).

Study of matrix effects and spectral interferences in the determination of lead in sediments, sludges and soils by SR-ETAAS using slurry sampling.

An interference-free, fast, and simple method is proposed for Pb determination in environmental solid samples combining slurry sampling and electrothermal atomic absorption spectrometry. Samples were ground to an adequate particle size and slurries were prepared by weighing from 0.05 g to 0.20 g of dry sediment, adding nitric acid, and a solution containing 0.1% Triton X-100. Ultrasonic agitation was employed for slurries homogenization. Analytical variables including acid pre-treatment conditions, particle size, slurry stability, temperature program of the graphite furnace, and type and concentration of the chemical modifier were studied. The undesirable effects of potential non-specific and spectral interferences on Pb signal were also taken into account. Continuum source and self-reversal methods for background correction were evaluated and compared. For calibration, synthetic acid solutions of Pb were employed. Calibration was linear within the range 1-30 microg L(-1) and 5-30 microg L(-1) when the 217.0 nm and 283.3 nm analytical lines were used. Correlation coefficients of 0.9992 and 0.9997 were obtained. Using optimized conditions, limits of detection (3sigma) of 0.025 microg g(-1) and 0.1 microg g(-1) were achieved for the 217.0 nm and 283.3 nm analytical lines, respectively. The method was successfully applied to the determination of lead in soil, contaminated soil, municipal sludge, and sediment samples. The accuracy was assessed by the analysis of two certified reference materials: municipal sludge (QC MUNICIPAL SLUDGE A) and lake sediment (TRAP-LRM from IJS).

Single-step solubilization of milk samples with N,N-dimethylformamide for inductively coupled plasma-mass spectrometry analysis and classification based on their elemental composition

A single-step procedure for trace elements analysis of milk samples is presented. Solubilization with small amounts of dymethylformamide (DMF) was assayed prior to inductively coupled plasma mass spectrometry (ICPMS) detection with a high efficiency sample introduction system. All main instrumental conditions were optimized in order to readily introduce the samples without matrix elimination. In order to assess and mitigate matrix effects in the determination of As, Cd, Co, Cu, Eu, Ga, Gd, Ge, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sm, S, Sr, Ta, Tb, V, Zn, and Zr, matrix matching calibration with (103)Rh as internal standard (IS) was performed. The obtained limits of detection were between 0.68 (Tb) and 30 (Zn) μg L(-1). For accuracy verification, certified Skim milk powder reference material (BCR 063R) was employed. The developed method was applied to trace elements analysis of commercially available milks. Principal components analysis was used to correlate the content of trace metals with the kind of milk, obtaining a classification according to adults, baby or baby fortified milks. The outcomes highlight a simple and fast approach that could be trustworthy for routine analysis, quality control and traceability of milks.

Nutritional analysis of Spirulina dietary supplements: Optimization procedure of ultrasound-assisted digestion for multielemental determination

Arthrospira platensis and Arthrospira maxima are a type of blue-green microalga used as a dietary supplement (Spirulina). A low time-consuming ultrasound-assisted digestion (UAD) of Spirulina supplements for multielemental determination by microwave induced plasma atomic emission spectrometry (MPAES) was performed. Several parameters such as acid concentration (AC), thermostated water bath (TWB), digestion time (DT) and UAD - probe or bath - affecting the digestion process were evaluated through a full factorial design. Under the optimal conditions -100 °C for TWB, 5% for AC and 10 min for DT- and selecting the bath as the proper UAD system, the concentrations of 15 analytes (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, V, Zn) were reported. The values are in accordance with the recommendation established by Food and Drug Administration (FDA) excepting for Cd. The knowledge of Spirulina multielemental composition contributes to an outstanding nutritional and toxicological report for human health.