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An optimized method for the simultaneous determination of Cr(III) and Cr(VI) in aqueous solutions using ion chromatography with chemiluminescence detection is described. Excellent resolution of the two chromium species was obtained using a single mixed-bed ion-exchange column with continuous elution. After postcolumn reduction of Cr(VI) to Cr(III), the light emitted during the Cr(III)-catalyzed oxidation of luminol with hydrogen peroxide was measured. Parameters affecting the postcolumn reactions such as reductant concentration, reductant mixing, point of luminol introduction, and luminol flow rate were optimized. The calibration curves in the range tested (0.01-50 μg L(-)(1)) were linear, and detection limits of 0.002 μg L(-)(1) for both Cr(III) and Cr(VI) were obtained. The results of the analyses of the water reference materials LGC CRM6010 and NIST SRM1643d with certified chromium values of 49 ± 4 and 18.53 ± 0.20 μg L(-)(1) and found to contain only Cr(III) were 49.2 ± 1.8 and 19.0 ± 1.5 μg L(-)(1), respectively. Values of 10.6 ± 0.5 and 10.1 ± 0.5 μg L(-)(1) were obtained when a simulated water sample containing 10 μg L(-)(1) Cr(III) and Cr(VI) was analyzed.

An interlaboratory trial for the determination of patulin in apple juice and fruit puree was conducted, involving 17 participants representing a cross section of industry, official food control, and research facilities. Mean recoveries reported ranged from 74 (10 ng/g) to 62% (25 ng/g) for apple juice and from 72 (25 ng/g) to 74% (10 ng/g) for fruit puree. Based on results for spiked samples (blind pairs at 2 levels), as well as naturally contaminated samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) in juice ranged from 8.0 to 14.3% and in puree from 3.5 to 9.3%. The relative standard deviation for reproducibility (RSDR) in juice ranged from 19.8 to 39.5% and in puree from 12.5 to 35.2%, reflecting HORRAT values from 0.6 to 1.0 for juice and 0.4 to 0.9 for puree. The method showed acceptable within-laboratory and between-laboratory precision for each matrix, as required by current European legislation.

An interlaboratory study was conducted for the determination of deoxynivalenol in baby food and animal feed by high-performance liquid chromatography with UV detection. The study included 14 participants representing a cross section of industry, official food control, and research facilities. Mean recoveries reported ranged from 89% (at 120 g/kg) to 85% (at 240 g/kg) for baby food and from 100% (at 200 g/kg) to 93% (at 400 g/kg) for animal feed. On the basis of the results for spiked samples (blind duplicates at 2 levels), as well as those for naturally contaminated samples (blind duplicates at 3 levels), the relative standard deviation for repeatability (RSDr) in analyses of baby food ranged from 6.4 to 14.0% and in analyses of animal feed, from 6.1 to 16.5%. The relative standard deviation for reproducibility (RSDR) in analyses of baby food ranged from 9.4 to 19.5% and in analyses of animal feed, from 10.5 to 25.2%. The HorRat values ranged from 0.4 to 1.0 and from 0.7 to 1.3, for baby food and animal feed, respectively. The method showed acceptable performance for within-laboratory and between-laboratory precision for each matrix, as required by European legislation.

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