Imazalil ([1-(β-allyloxy-2,4-dichlorophenethyl)imidazole]) is a systemic chiral fungicide used in postharvest protection of citruses against fungi development for during storage and transportation. The chemical structure of imazalil shows an asymmetric carbon in the C7 position. These enantiomers may have different toxicity. A method for both chiral enantiomers extraction and determination in orange juice is developed in order to provide their concentration and to study the degradation rates in orange juice. Spiked imazalil was extracted from orange juice by dispersive liquid-liquid micro extraction and solid phase extraction. Recovery assays of imazalil enantiomers from spiked orange juice samples showed that solid phase extraction is a better choice in order to obtain higher recovery values. Obtained chromatographic data show that within 24h the (-)-imazalil enantiomer decreases from 0.548 to 0.471 (expressed as enantiomer fraction).
A facile approach for the enantiomeric excess determination of enantiomeric mixtures without the necessity of pure enantiomer standards is presented. Promethazine and trimeprazine commercial nonracemic mixtures were used as cases study to probe the validity of the method. Chromatographic resolutions obtained with a chiral column AGP in reverse phase mode were 1.32-1.16 (promethazine) and 1.20-0.93 (trimeprazine) for the three detectors (circular dichroism, photometric and fluorimetric) in series. Results obtained showed that enantiomeric excess was 10.4, 8.71 and 8.58% for promethazine and 1.60, 1.23 and 1.80% for trimeprazine (medium values of 9.23 ± 1.01% and 1.54 ± 0.29%, respectively). Recovery assay over human serum samples, at three concentration levels, spiked with prometazine and submitted to solid-phase extraction, gave values of 99.09-93.48% [S-(-) enantiomer] and 98.51-91.89% [R-(+)-enantiomer]. Detection limits of promethazine enantiomers were between 0.02 µg (fluorimetric) and 1 µg (circular dichroism), and 0.02-1.1 µg for trimeprazine.
A flow injection system with chemiluminescence detection for the determination of asulam, enhancer of the system luminol-H(2)O(2)-horseradish peroxidase, is proposed. The method shows a moderate selectivity against other pesticides usually present in formulations of herbicides and in water. The procedure was applied to the determination of asulam in tap water samples and a recovery study was carried out in order to validate the method. The obtained results show acceptable recovery values (between 88.3 and 93.9%). The detection limit for asulam was 0.12 ng/mL. The precision of the method expressed as relative standard deviation was 1.55% (n = 8), at the 19 ng/mL level.
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