Enantiomeric fraction of styrene glycol as a biomarker of occupational risk exposure to styrene.

This work reports a new analytical approach for monitoring the enantiomeric ratios of styrene glycol (SG), encountered during the manufacture of plastics, by chiral liquid chromatography and the application as a biomarker for exposure to styrene. The isomers were separated using an AGP column running in the reverse phase and isocratic mode with a mobile phase consisting of 20 mM phosphate buffer saline (pH 4.15) and methanol at a flow rate of 0.8 mL/min. Photometric, polarimetric, and circular dichroism detectors were employed. The chromatographic enantioselective resolution (Rs) and selectivity index (α) values were determined to be 1.60 and 1.48 (by photometric detection), respectively. Calibration curves used for the quantification of the SG enantiomers were linear with a correlation coefficient >0.99; the detection limits were in the range of 0.03-0.16 µg, depending on the detector used. Recovery assays on synthetic samples (in triplicate) covering the full range of enantiomeric fractions (0.0-1.0) show accuracy values below 5% for the enantiomeric fraction (EF) in every case. An alternative method based on the measurement of anisotropy factors for the determination of EF, which is faster and does not require the separation of enantiomers, has also been developed. The enantiomeric excess of the toxicant biomarker styrene glycol has been determined. No previous direct enantioselective determination of styrene glycol was published.

Enantioseparation of the fungicide imazalil in orange juice by chiral HPLC. Study on degradation rates and extractive/enrichment techniques.

Imazalil ([1-(ß-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).

Enantiomeric resolution of bupivacaine by high-performance liquid chromatography and chiroptical detection.

This work reports a new analytical procedure for the separation and determination of the enantiomers of bupivacaine and the determination of the enantiomeric purity. The isomers were separated using a Chirex 3020 (250 mm x 4.6 mm) with a mobile phase of n-hexane:dichloroethane:ethanol (82:9:9, v/v/v) at a flow-rate of 1 ml min(-1) and UV, polarimetric and circular dichroism (CD) detection. Obtained retention times were 5.93 and 7.53 min (R and S) with a resolution of Rs=2.36. Precisions (RSD) were 1.83 and 2.02% (CD detection) and 3.07 and 1.26% (UV detection) for R- and S-enantiomers, respectively (at 10 microg level). Detection limits were 0.5 and 0.5 microg (R and S) with CD detection, and 0.9 and 0.3 microg with UV detection. Polarimetric detection was inadequate to perform a quantitative method at similar concentration ranges as UV and CD because of poor sensitivity. A procedure for determination of enantiomeric purity using a conventional chromatographic column (RP18, Luna) coupled to a CD detector and anisotropy factor (CD/UV) as analytical signal was also developed. Obtained results show that RSDs of 6.7-1.6% were obtained in the range of 0-100% enantiomeric purity.

Development and characterisation of an immunoaffinity chromatographic column for the on-line determination of the pesticide triclopyr.

An immunoaffinity column for the selective extraction and concentration of the herbicide triclopyr from water samples and quantification on line by HPLC has been developed. The immunoaffinity device was prepared by immobilising triclopyr antibodies to hydrazide derivatized azlactona beds. Efficient desorption of bound triclopyr was achieved with 70% ethanol/water solution. The column was evaluated regarding selectivity, recovery, capacity, saturation volume and reusability. Obtained results show that immunoaffinity chromatography (IAC) can be used for quantitative extraction, concentration and determination of triclopyr from water samples.

Enzyme-linked immunosorbent assay by image analysis using a charge-coupled device array detector.

This paper describes a fluorescence enzyme-linked immunosorbent assay (ELISA) for the quantification of (+/-)-2-(2, 4-dichlorophen-oxy)propionic methyl ester (dichlorprop methyl ester). Antibodies for dichlorprop methyl ester were produced by immunizing rabbits with a conjugate of dichlorprop methyl ester with bovine serum albumin. Data acquisition on microtiter wells is performed by a spectrofluorometer through a fiber optic and by a charge-coupled device camera. A correlation was obtained between the image analysis data on ELISA and the data acquired by the spectrofluorometer. The results demonstrate that the fluorescence image analysis performed by the charge-coupled device detector is applicable to ELISA, and the analysis time, sensitivity, and precision of the ELISA procedure are compared to conventional fluorescence ELISA performed by the spectrofluorometer. The ELISA procedure was selective for structurally similar compounds or usually found in formulation pesticides. Concentrations for 50% displacement curves were dichlorprop, 83.59 microg/ml, and 2,4,5-T, 388.23 microg/ml; triclopyr, ioxynil, bentazone, and MCPA had no response.

Thermodynamic parameters for the molecular inclusion reaction of dulcin with beta-cyclodextrin. spectrofluorimetric determination of dulcin.

The inclusion of dulcin in alpha- and beta-cyclodextrin has been studied by fluorescence spectroscopy. To quantitatively describe complex formation between the beta-cyclodextrin and dulcin, an association constant of 290 M(-1) at 21 degrees was obtained. The thermodynamics associated with the complex formation between dulcin and beta-cyclodextrin in aqueous solution has been studied. The obtained value of DeltaG(0) = -13.7 kJ/mole at 21 degrees , together with DeltaH(0) = -33.6 +/- 2.3 kJ/mole and DeltaS(0) = -67.2 +/-8.3 Jmole(-1) K(-1) indicate that dulcin has a very marked tendency to associate with beta-cyclodextrin in water. The inclusion complex of dulcin in beta-cyclodextrin has been used to determine dulein in the range 0.13-5 mug/ml the method has been applied to determine dulcin in soft drinks.

Environmentally shifted fluorescence lifetimes for multicomponent phase-modulation fluorimetric analysis.

Several cyclodextrins, surfactants, and a series of three organic solvents-methanol, isoamylic alcohol, and hexanol-with different polarities and viscosities, were used to study the influence of the microenvironment on the fluorescent behavior of three diuretics-furosemide, triamterene, and piretanide. We concluded that on going from methanol to hexanol, the fluorescence lifetime of furosemide from 0.91 to 2.10 ns, that of triamterene from 4.54 to 4.44 ns, and that of piretanide from 5.24 to 10.37 ns. At 40 MHz, the phase shifts (excitation/emission) produced by furosemide, triamterene, and piretanide were 12.0, 29.6, and 30.2° in methanol and 27.8, 48.1, and 69.0° in hexanol. A three-factor, three-level factorial design allowed us to establish a calibration matrix of the three diuretics that covered the three ranges from 10 to 40, 1.5 to 6, and 0.1 to 0.4 µM for furosemide, piretanide, and triamterene, respectively. Data processing incorporated PLS adjustment values. The function was fitted to a phase-resolved fluorescence intensity at the three phase angles selected. Percentages recoveries were from 88 to 115%.

Analytical applications of 1,10-anthraquinones: A review.

Analytical aspects of the chemistry in solution of 1,10-anthraquinone (AQ) derivatives is reviewed. The information about photometric and fluorimetric determination of inorganic species has been condensed and presented in tabular form.