A. García Pareja

Micellar liquid chromatography of plant growth regulators detected by derivative fluorometry

Abstract A micellar liquid chromatographic method with fluorimetric detection was developed for the determination of the plant growth regulators indol 3-yl acetic acid (IAA), 2-(1-naphthyl) acetic acid (1-NAA), indol 3-yl propionic acid (IPA), 2-(2-naphthyl) acetic acid (2-NAA), indol 3-yl butyric acid (IBA), 2-(1-naphthyl) acetamide (1-Namide) and indol 3-yl acetic acid ethyl ester (IAA ethyl ester). Extraction of plant hormones was performed with methanol, followed by purification with ethyl acetate, solid-phase extraction and again partitioning against diethyl ether. Sodium dodecylsulphate (10 mM) is used as mobile phase to elute the compounds in a maximum run-time of 23 min. Partially or unresolved peaks are separated by calculation of the 1st derivative chromatogram. Detection limits are between 0.30 μg g−1 and 1.10 μg g−1.

Liquid Chromatographic Determination of Asulam and Amitrole with Pre-Column Derivatization

Abstract A liquid chromatographic pre-column derivatization method with fluorimetric detection for the simultaneous determination of asulam and amitrole was developed. The separation was accomplished in less than 15 min. R.S.D.s (n = 10) of 1.13% and 1.6% (concentration) and 1.4% and 0.97% (retention time), were obtained for asulam and amitrole respectively. Recoveries from spiked tap water ranged from 90% to 118%, and detection limits of 0.04 ng for asulam and 7.5 ng for amitrole, were obtained.

Enantiomeric resolution of pyrethroids by high-performance liquid chromatography with diode-laser polarimetric detection

Liquid chromatographic separation of the pyrethroid insecticides, bifenthrin and fenpropathrin, has been investigated with various achiral and chiral stationary phases. The identification of enantiomers of fenpropathrin and bifenthrin has been carried out by using two detectors in high-performance liquid chromatography: a UV spectrometer and a diode-laser polarimeter. Optimization of the mobile phase has been performed dealing regard to analyte resolution and polarimetric signal values.

Ion-pair reversed-phase liquid chromatography with fluorimetric detection of pesticides

Abstract The pesticides asulam, propoxur, coumatetralyl, biphenyl-2-ol and thiabendazole were separated by ion-pair reversed-phase liquid chromatography with fluorescent detection. The mobile phase contained methanol, acetic acid and sodium cholate as ion-pair reagent. In addition, tetramethylammonium hydrogensulphate and triethylamine were added to elute the pesticides. Separations were accomplished in less than 20 min. Interferences from nineteen pesticides were studied and recoveries from synthetic mixtures ranging from 90 to 110%. Recoveries from spiked apples and wheat grains ranged from 94 to 105% with relative standard deviations between 1.4 and 9.2% and detection limits between 0.1 and 1.9 ng.

HPLC Determination of Tryptophan Enantiomers with Photometric, Fluorimetric and Diode-Laser Polarimetric Detection

SummaryThe combined utilization of photometric, fluorimetric and polarimetric detection liquid chromatography detectors in series for the identification and quantification of D-tryptophan and L-tryptophan was evaluated. Detection limits of about 1 μg were established with the range of linearity extending to about 100 μg. The relative standard deviation of the D-form and L-form tryptophan were 7.32 and 4.22%, respectively. The amount unknown of tryptophan enantiomers in the different mixtures was determined with an accuracy of 1.58% at the 40 μg injection level.

Spectrofluorimetric determination of the organophosphorus insecticide quinalphos in citrus fruits

Abstract The simple spectrofluorimetric method described for the determination of quinalphos in citrus fruits has a limit of detection of 3 ng ml −1 . The extracted insecticide is weakly fluorescent and is hydrolyzed in alkaline medium to give the strongly fluorescent quinoxalin-2-ol. Factors affecting the rate of hydrolysis are described in detail. Methods are developed based on normal and synchronous spectrofluorimetry. Recoveries are in the range 95–99% with relative standard deviations 2.5-4%. The method is suitable for determining quinalphos in spiked citrus fruit. The proposed method is compared with a liquid-chromatographic method.

HPLC enantiomeric resolution of (+)-cinchonine and (-)-cinchonidine with diode-laser polarimetric detection

Abstract The combination of UV and diode-laser polarimetric detection of chiral molecules offers significant advantages in high performance liquid chromatography. The method described here circumvents the derivatization step and the use of chiral stationary or mobile phases for the resolution of enantiomers. Data acquisition of the polarimeter was performed with AC/DC interface and software Pico ADC-100 coupled to the polarimeter detector. Quantitative methods in the range 1-150 μg and 1-600 μg of (+)-cinchonine and (-)-cinchonidine, respectively, were established. Enantiomeric ratio determined by using UV and diode-laser polarimetric data without chiral separation is discussed. Manuscript 1080

Normal-Phase Liquid Chromatography on Amino-Bonded-Phase Column of Fluorescence Detected Pesticides

Abstract A liquid chromatographic method with fluorimetric detection is developed for the simultaneous determination of aminocarb, carbaryl, carbendazim, fuberidazole and 1-naphthylacetamide. An amino-bonded column was used and the optimun mobile phase was selected through fitting a mathematical model to experimental data. Separations were accomplished in less than 20 min. Recoveries from spiked grapes ranged from 90 % to 103 % and detection limits between 5.5 × 10−3 mg kg−1 for fuberidazol and 0.08 mg kg−1 for 1-naphthylacetamide and relative standard deviation lower than 6 %.