A capillary micellar electrokinetic chromatography method for the stereoselective quantitation of bioallethrin in biotic and abiotic samples.

A capillary micellar electrokinetic chromatography (MEKC) method was developed enabling the stereoselective separation of the insecticide bioallethrin. The use of sodium deoxycholate bile salt and acetyl-ß-cyclodextrin (acetyl-ß-CD) made possible the separation of bioallethrin stereoisomers with a high enantioresolution (7.4) in a short analysis time (6.5min). The analytical characteristics of the developed method were evaluated in terms of linearity, accuracy, precision, and limits of detection (LOD) and quantitation (LOQ) showing a good performance for the quantitation of bioallethrin stereoisomers with LODs of 0.2 and 0.3mg/L. The developed method was applied to the stereoselective analysis of a commercial bioallethrin pediculicide formulation and to evaluate the toxicity of bioallethrin stereoisomers on the growth of the unicellular freshwater green alga Pseudokirchneriella subcapitata and on the germination of the higher plant Sorghum bicolor (non-target organisms). The analysis of the commercial pediculicide showed a good agreement between the contents determined for the two stereoisomers and those labelled in the commercial samples. Different toxic responses and biodegradation profiles were found for each stereoisomer in ecotoxicity assays. The mixture of S/R stereoisomers of bioallethrin resulted more toxic than S-bioallethrin for green algae, with EC50 values of 1.10±0.06 for the mixture and of 1.73±0.05mg/L for the pure S-biallethrin (esbiol). Germination of plants seeds was also affected.

Enantioseparation of esbiothrin by cyclodextrin-modified microemulsion and micellar electrokinetic chromatography.

A comparison between chiral cyclodextrin-modified microemulsion electrokinetic chromatography (CD-MEEKC) and cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) for the enantiomeric separation of esbiothrin was carried out. For both methods, the separation conditions were optimized by varying CD types and concentration, running buffer pH and compositions, organic modifiers, and temperature. The optimal CD-MEEKC conditions were 0.8% n-heptane, 2.3% SDS, 6.6% n-butanol, 90.3% 10 mM sodium tetraborate containing 3% (w/v, the ratio of CD mass to microemulsion volume) methyl-beta-cyclodextrin, pH 10, 25 degrees C. The optimized CD-MEKC conditions were 3.3% SDS, 96.7% 10 mM sodium tetraborate containing 5% (w/v) beta-CD, pH 10, 25 degrees C. The difference in physicochemical properties of the buffer and CDs resulted in different optimal CD type. The competitive distribution between the microemulsion (or micelle) and chiral CD contributed to the chiral separation. Both methods provided excellent separation (R(s) approximately 3) with similar migration time (ca. 15 min). CD-MEEKC provided higher separation efficiencies (>300000) than CD-MEKC (>200000). The LODs for CD-MEEKC and CD-MEKC were 4.7 microg/mL and 3.2 microg/mL, respectively. The RSDs of migration time and peak area for CD-MEEKC were slightly higher than for CD-MEKC. Both the demonstrated CD-MEEKC and CD-MEKC methods provided high efficiencies, low LODs, and reproducible enantioseparations of esbiothrin.

Enzyme-linked immunosorbent assay (ELISA) and sol-gel-based immunoaffinity purification (IAP) of the pyrethroid bioallethrin in food and environmental samples.

Enzyme-linked immunosorbent assay (ELISA) and sol-gel-based immunoaffinity purification (IAP) methods for the pyrethroid bioallethrin were developed and applied for monitoring bioallethrin in spiked food, soil, and dust samples. Attempts to determine bioallethrin content in fruit and vegetable extracts revealed high variability between sample preparations and marked interferences with the assay. Sol-gel IAP followed by solid-phase sample concentration was effective in removing the interfering components and resulted in high recovery of bioallethrin from spiked crude acetonic extracts of fruits and vegetables, even in the presence of high extract concentrations (28%). Solid-phase treatment alone failed to remove the interfering components from the spiked sample. Gas chromatography-mass spectrometry analysis of the IAP samples revealed bioallethrin as a doublet unsolved peak because of the cis and trans isomer present in the standard with confirmation of its mass. Unlike fruit and vegetable extracts, soil and dust samples did not interfere with the ELISA, and the bioallethrin content in those samples could be determined with high precision without the need of any further purification.

[Determination of optical purity of SR-bioallethrin enantiomers by chiral high performance liquid chromatography].

A chiral stationary phase(CSP) was prepared by coating cellulose-tris (3,5-dimethylphenylcarbamate) onto aminopropylated spherical silica gel. On the CSP, the chiral separation of the bioallethrin enantiomers has been investigated and under the optimum conditions the optical purity of three samples of SR-bioallethrin enantiomers was determined by peak area. The results show that the method established is very ideal for determining the optical purity and evaluating the quality of the samples.

Carbon-based quantitation of pyrethrins by supercritical-fluid chromatography.

All six insecticide active ingredients in pyrethrum extract were quantified by supercritical fluid chromatography and carbon calibration. Allethrin is a suitable reference compound for carbon calibration and pyrethrins calibrations. Carbon quantification in SFC is also applied to pyrethroids (phenothrin, permethrin, cypermethrin, fenvalerate and deltamethrin) and alkanes. Halogen substitution on pyrethroids requires halogens on the reference calibration compound. The method was applied to commercial extracts.