Daniele C.M.B. Santos

Sample Preparation for the Determination of Metals in Food Samples Using Spectroanalytical Methods—A Review

Abstract The present article gives an overview of recent publications and modern techniques of sample preparation for food analysis employing atomic and inorganic mass spectrometric techniques, such as flame atomic absorption spectrometry, chemical vapor generation atomic absorption and atomic fluorescence spectrometry, graphite furnace atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry. Among the most frequently applied sample preparation techniques for food analysis are dry ashing, usually with the addition of an ashing aid, and acid digestion, preferably with the assistance of microwave energy. Slurry preparation, particularly with the assistance of ultrasound, is increasingly used to reduce acid consumption and sample preparation time. Direct analysis of solid samples is gaining importance in the field of food analysis as it offers the highest sensitivity, avoids the use of acids and other aggressive reagents, makes possible the analysis of micro‐samples, and can be applied for fast screening analysis, e.g., of fresh meat.

Evaluation of digestion procedures for simultaneous determination of Ca, P, Mg, K and Na in biodiesel by inductively coupled plasma optical emission spectrometry

In the present work, the efficiency of two procedures for the digestion of biodiesel was investigated for the simultaneous determination of Ca, P, Mg, K and Na by axial view ICP OES. In the open system with conventional heating, concentrated nitric and sulfuric acids were added to the samples, and the addition of hydrogen peroxide completed the digestion. In the microwave-assisted closed system, complete digestion was performed using concentrated nitric acid and hydrogen peroxide. The analytical performances were evaluated through limits of quantification, precision of the overall procedures, final acidity of the digests, and residual carbon contents. The contents of residual carbon for the biodiesel samples digested were 0.358 ± 0.012% using the open system with conventional heating and 0.614 ± 0.023% using the microwave-assisted closed vessel system, demonstrating the high efficiency of both proposed procedures. The optimized microwave-assisted decomposition procedure produced the fastest, safest and most accurate analytical results with recoveries of 89.0-103.0% and deviations lower than 5% in most cases. Low limits of detection were obtained (< 0.40 µg g-1), adequate for the established limits set out in Brazilian legislation for these analytes. Three biodiesel samples produced from different oil sources were analyzed. In comparison with other procedures proposed in the literature, the developed procedure using the microwave-assisted closed system is advantageous because it neither require organic standard solutions for calibrations nor use toxic organic solvents.

Bioaccessibility assessment of toxic and essential elements in produced pulses, Bahia, Brazil

The objective of this study was to analyze the effect of heat treatment on the bioaccessibility of major (K, Ca, Mg, P) and trace elements (As, Ba, Cu, Fe, Mn, Cd, Cr, Hg, Mo, Ni, Pb, Se, Sb, Sn, and Zn) in three different pulse species: Vigna unguiculata L. Walp (cowpea beans), Cajanus cajan L. (pigeon pea) and Lablab purpureus L. Sweet (mangalo). Analyte concentrations were determined in the samples by inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. The results showed that thermal processing can affect the concentrations of the elements investigated in pulse samples. The influence of the heat treatment can range between legume species and chemical elements, as well as with the type of heat treatment, dry, wet, conductive heating and using microwaves.

Sequential Injection Chemiluminescence Methodology for Ozone Evaluation

A sequential injection methodology with chemiluminescence detection for the evaluation of residual ozone in waters is presented. The procedure is based on the reaction between luminol and ozone without catalysts. Linear calibration plots were obtained for ozone concentrations between 0.05 and 2.0 mg L−1, with a detection limit of 0.04 mg L−1. The developed methodology was applied to the determination of residual ozone in ozonized waters and the results complied with those furnished by the spectrophotometric reference procedure (relative deviations < 6.3%). The method exhibited good precision (RSD < 3.5%) and the sampling rate was about 140 determinations per hour.

Toxic Elements and Microbiological Content of Food: Evidence from a Case Study in a Brazilian City Heavily Contaminated by Lead and Cadmium

-1 ) and E. coli was higher than recommended levels. The range of toxic elements revealed higher concentrations of lead in chicken muscle (1.25-11.58 mg kg -1 ) and cadmium in eggs (0.45-1.06 mg kg -1 ). Finally, the risk to the inhabitants of Santo Amaro was evident and reinforces the importance of effective actions of local authorities.