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Cadmium was continuously extracted with diluted nitric acid from legumes and dried fruit samples using a simple, rapid and continuous ultrasound-assisted extraction system. A minicolumn packed with a chelating resin (Chelite P, with aminomethylphosphoric acid groups) was placed between the extraction unit and the detector for cadmium preconcentration. The cadmium content in the acid extract was retained into the minicolumn, and elution was carried out with hydrochloric acid, with this trace metal continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 2(6) x 3/16) was used to optimize the continuous leaching procedure and the preconcentration step. The method allowed a total sampling frequency of 10 and 14 samples per hour for legumes and dried fruit, respectively. The procedure displayed good precision (2.0 and 2.5%, respectively, expressed as relative standard deviations) for samples containing 0.202+/-0.005 microg g(-1) Cd (broad bean) and 0.239+/-0.004 microg g(-1) Cd (peanut). Detection limits of 0.014 microg g(-1) Cd for 60 mg of legume samples and 0.011 microg g(-1) Cd for 80 mg of dried fruit samples were obtained. The method was successfully applied to the determination of trace amounts of cadmium in legumes and dried fruit samples.

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A new sensitive and low-cost method that combines continuous acid extraction, online preconcentration, and flame atomic absorption spectrometry for cadmium determination at g levels in solid and semisolid milk products is described. A continuous ultrasound-assisted extraction system is used to carry out the dynamic acid extraction step. The acid extract is preconcentrated online on a minicolumn packedwith a chelating resin (Chelite P,with aminomethylphosphoric acid groups), and the retained cadmium is elutedwith hydrochloric acid and continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 263/16) is used to optimize the continuous extraction and the preconcentration step. The method allowed a total sampling frequency of 28 samples/h. A good precision of the whole procedure (3.0% relative standard deviation) for a cheese sample containing 0.103 0.004 g/g Cd (dry mass), a high enrichment factor (20.5), and detection and quantification limits of 0.014 and 0.067 g/g, respectively, for a 60 mg of sample were obtained with this methodology. The method was successfully applied to the determination of trace amounts of cadmium in solid and semisolid milk products, such as cheese and yogurt samples.

Iron was extracted on-line from solid meat samples by a simple and rapid continuous ultrasound-assisted extraction system (CUES). The CUES is connected to a flow injection manifold, which allows the on-line flame atomic absorption spectrometric determination of iron. A Plakett-Burman design was used for the optimisation of the CUES. The method achieved a total sampling frequency of 11 samples per hour with a relative standard deviation for the complete procedure of 0.4%. The detection limit was 0.6 microg g(-1) (dry mass) for a sample amount of 30 mg. Accurate results were obtained by measuring the certified reference materials BCR-186 (pig kidney) and BCR-184 (bovine muscle). The analytical procedure was applied to different real meat samples with satisfactory results.