No abstract

Sediment samples from 25 sites in 17 rivers of the Pantanal (Brazil) were analyzed with the objective of evaluating pesticide contamination in sediments. Samples were extracted with an acetone, ethylacetate, and water mixture 2:2:1 (v/v/v). The extract was purified by flash chromatography with aluminum oxide and florisil. A multiresidue gas chromatography-mass spectrometry method was applied to monitor 23 pesticides of different chemical classes (organochlorine, organophosphorus, triazines, anilides and pyrethroids) with some of their degradation products. Compounds identified in sediment samples included lambda -cyhalothrin (1.0 to 5.0 micro g kg(- 1)), p,p'-DDT (3.6 micro g kg(- 1)), deltamethrin (20.0 micro g kg(- 1)) and permethrin (1.0 to 7.0 micro g kg(- 1)).

Establishing fast, simple, low-cost, and efficient sample preparation procedures to determine elements in foodstuffs is a relevant aspect for nutritional and health purposes. For this reason, the recently proposed closed-vessel conductively heated digestion system (CHDS) was evaluated for the digestion of milk powder, chocolate powder, and soluble coffee samples aiming for Ca, Cu, Fe, K, Mg, Mn, Na, and Zn determinations by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and Cd, Mo, and Se determinations by inductively coupled plasma mass spectrometry with tandem configuration (ICP-MS/MS). The accuracy was evaluated by analyzing two milk certified reference materials digested by the CHDS and a microwave oven for comparison. When using the CHDS, recoveries for the analytes varied from 91 to 104 %. For microwave digestions, recoveries within the 94-109 % intervals were obtained. The method was then applied to the samples. For comparative purposes, the analytes were also determined in the samples after microwave digestion, and the results between the two digestion systems showed no differences based on a paired t test at a 95 % confidence level. Similar analytical blanks were obtained because quartz digestion tubes were used in both digestion systems. The CHDS with quartz tubes is an interesting alternative for laboratories dedicated to large-scale routine analysis because volatile elements usually found in very low concentrations in food samples such as Cd and Se can also be determined.

In this work, an improved conductively heated digestion system (CHDS) with closed vessels, which provides simpler, easier and safer digestion of raw chicken, beef and pork meat samples aiming at Ca, Cu, Fe, K, Mg, Mn, Na, P, S, and Zn determinations by ICP OES and As, Cd, Cr, Mo, Pb and Se by ICP-MS/MS, was evaluated.

This study reports the use of background signals and multivariate calibration as a procedure to assess total concentration of concomitants in thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). TS-FF-AAS employs a metal tube atomizer above an air/acetylene flame and the atoms residence time is longer than that observed in FAAS (flame AAS). As a result, elevated background signals are obtained. The main purpose of this study is to make use of the background signals to predict the total concentration of concomitants. Background signals of 29 solutions containing Cd (25 mg L À1 ), Pb (500 mg L À1 ) and four concomitants (Ca, K, Mg and Na-total concentration values ranging from 0 to 5.52 g L À1 ) were recorded at two wavelengths: 228.8 nm for Cd and 283.3 nm for Pb. With the help of partial least squares, calibration models using either each wavelength alone or a combination of both were constructed to predict the total concentrations of concomitants. The best model showed root mean square error of validation (RMSEV) of 0.35 g L À1 using background signals at 283.3 nm. A pharmaceutical sample containing 3 g L À1 of the total concentration of Ca, K, Mg and Na was analyzed and 3% was the relative error. This sample and those used in the calibration/validation sets were also analyzed using X-ray fluorescence (XRF) and a good agreement was observed. This study extends the possibilities for the use of background signals in spectrometric techniques.

No abstract

A high-throughput, low cost and efficient device based on conductive heating and closed-vessels was developed and applied to plant digestion.

This paper presents some recent applications of Flame Atomic Absorption Spectrometry (FAAS) to different matrices and samples. The time window selected was from 2006 up to March, 2011, and several aspects related to food, biological fluids, environmental, and technological samples analyses were reported and discussed. In addition, the chemometrics application for FAAS methods development was also taken into account, as well as the use of metal tube atomizers in air/acetylene flame. Preconcentration methods coupled to FAAS were discussed, and several approaches related to speciation, flotation, ionic liquids, among others were discussed. This paper can be interesting for researchers and FAAS users in order to see the state of the art of this technique.