L. Toribio

Chiral packed column subcritical fluid chromatography on polysaccharide and macrocyclic antibiotic chiral stationary phases

Abstract The polysaccharide chiral stationary phases (CSPs) Chiralcel OD and Chiralpak AD, and the macrocyclic antibiotic CSPs Chirobiotic V and Chirobiotic T were evaluated in packed column subcritical fluid chromatography (pSFC) for the separation of different types of racemic compounds (β-blockers, β-agonists, benzodiazipines, non-steroidal anti-inflammatory drugs, barbiturates, free and derivatized amino acids, etc.). The same conditions and program could be applied to check the applicability and enantioselectivity of one of the CSPs for a given racemic mixture. The conditions are: temperature 30°C, pressure 200 bar, flow-rate 2 ml/min, carbon dioxide, modifier methanol containing 0.1% trifluoroacetic acid (TFAA) and 0.1% triethylamine (TEA) with a gradient from 5% (5 min) to 30% at 5%/min. A resolution of 0.4 under those conditions generally indicates that baseline separation can be realized on the CSP by fine-tuning the different parameters of the SFC separation. The best CSP for pSFC proved to be Chiralpak AD which provided separation for 70% of the 44 substances tested, followed by Chiralcel OD (66%), Chirobiotic T (50%) and Chirobiotic V (48%). For comparison, the enantio-selectivity in pSFC of the brush type CSPs Chirex 3022 with π-donor characteristics and Chirex 3005 with π-acceptor characteristics was also evaluated. As expected, these phases perform poorly under SFC conditions, on Chirex 3022 (34%) and on Chirex 3005 (20%).

Analysis of pesticide residues in wine by solid-phase extraction and gas chromatography with electron capture and nitrogen-phosphorus detection.

A feasible and reproducible method for multiresidue analysis of several common pesticides, of different polarities, in wine samples is proposed. The method combines a solid-phase extraction on polymeric cartridges eluted with ethyl acetate and a gas chromatographic determination using electron capture and nitrogen-phosphorus detection. To avoid the matrix effect, previous washing of the cartridges with a mixture of water-2-propanol (90:10) and further clean-up of the extract on Florisil cartridges, together with a calibration using spiked extracts, are recommended.

High-performance liquid chromatographic determination of methyl anthranilate, hydroxymethylfurfural and related compounds in honey☆

A high-performance liquid chromatographic method for determining 5-hydroxymethyl-2-furaldehyde (hydroxymethylfurfural), 2-furaldehyde (furfural), furan-2-carboxylic acid (2-furoic acid), furan-3-carboxylic acid (3-furoic acid), furan-3-carboxaldehyde (3-furaldehyde) and 2-aminobenzoic acid methyl ester (methyl anthranilate) in honey and honeydew samples is described. To prevent matrix interference and to isolate the compounds, a clean-up step which implies a solid-phase extraction on polymeric cartridges and an elution with 0.5 ml methanol is recommended. The compounds are separated on a reversed-phase column with a gradient of (A) 1% aqueous acetic acid-acetonitrile (97:3, v/v) and (B) acetonitrile-water (50:50, v/v), with UV detection at 250 nm. The method is applied to the analysis of samples from different botanical origin.

Supercritical fluid chromatography in food analysis

In the last years, supercritical fluid chromatography (SFC) has increased its acceptance between scientists. The unique selectivity, short analysis times, low consumption of organic solvents as well as the improvements in instrumentation have contributed to expand its use. These characteristics make SFC a powerful tool when food analysis requires individualized evaluation of several compounds in very complex samples. In this work, the advantages and main applications of SFC in food analysis are reviewed, focusing special attention onto analytical and preparative separations.

Development and validation of an LC assay for sumatriptan succinate residues on surfaces in the manufacture of pharmaceuticals

A high performance liquid chromatographic (HPLC) method for the assay of sumatriptan succinate residues in swabs collected from manufacturing equipment surfaces was developed and validated in order to control a cleaning procedure. The swabbing procedure using two cotton swabs moistened with water was validated applying a wipe-test and a HPLC method developed to determine low quantities of the drug. The HPLC method involves a C18 column at 25 degrees C, a mixture of ammonium phosphate monobasic (0.05 M)-acetonitrile (84:16, v/v) as a mobile phase and UV detection at 228 nm. Using the proposed method, the average recoveries obtained are of 88.5% for vinyl, 94.2% for glass and 95.2% for stainless steel plates with RSD of 5.5 (n=36), 2.3 (n=36), 2.2% (n=36), respectively. The method was successfully applied to the assay of real swab samples collected from the equipment surfaces.

Determination of glutathione, cysteine and N-acetylcysteine in rabbit eye tissues using high-performance liquid chromatography and post-column derivatization with 5,5′-dithiobis(2-nitrobenzoic acid)

A high-performance liquid chromatographic method to determine glutathione, cysteine and N-acetylcysteine in rabbit retina, vitreous and lens has been developed. The thiols are separated using a 25 x 0.46-cm octadecylsilane column with 0.5 M phosphate buffer, pH 3, as mobile phase. The detection, at 412 nm, involves a post-column derivatization with 5,5-dithiobis(2-nitrobenzoic acid) in presence of cationic micelles of hexadecyltrimethylammonium bromide that enhances the sensitivity. The detection limits are 0.21, 0.92 and 0.61 mumol/g wet sample for glutathione, cysteine and N-acetylcysteine, respectively.

Gas chromatography with electron-capture and nitrogen–phosphorus detection in the analysis of pesticides in honey after elution from a Florisil column: Influence of the honey matrix on the quantitative results

A modified procedure to extract pesticides from honey samples that involves loading the honey onto a Florisil packed column and subsequently eluting it with an n-hexane-dichloromethane mixture is proposed. Anomalous high gas chromatographic responses and subsequently very high recoveries for the pesticides in the extracts were obtained by a conventional calibration with pesticide solutions in organic solvent. This effect was attributed to the honey matrix and can be circumvented by using spiked honey extracts as calibration standards.

Quality assurance of commercial beeswax: II. Gas chromatography–electron impact ionization mass spectrometry of alcohols and acids

Gas chromatography with mass spectrometric detection was used to find the fraction of alcohols and acids present in pure beeswax from Apis mellifera. Some new compounds not described till now were found, such as a family of unsaturated linear fatty acids, several hydroxyacids and 1,2,3-propanetriol monoesters. The chromatographic profiles obtained from pure beeswax and bee-rejected foundation beeswax can be used to discriminate them; they mainly differ in the amount of some acids and alcohols.

High-performance liquid chromatographic determination of benomyl and carbendazim residues in apiarian samples☆

Simple procedures for the extraction and chromatographic determination of benomyl and carbendazim in honey, bees wax, larvae, bees and pollen are proposed. The fungicides were extracted from honey, larvae and bees using ethyl acetate, while methanol was more suitable for wax and pollen samples. Pollen extracts need a further clean-up step with n-hexane. The determination is carried out by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection. The procedures have been applied to the analysis of benomyl on honey and larvae samples from hives whose bees were nourished with artificial food mixed with benomyl.

Applications of the Chiralpak AD and Chiralcel OD chiral columns in the enantiomeric separation of several dioxolane compounds by supercritical fluid chromatography.

Two chiral columns based on polysaccharide derivatives (Chiralpak AD and Chiralcel OD) have been tested for the chiral separation of several dioxolane compounds, using supercritical fluid chromatography. The compounds studied included ketoconazole and some of its precursors. The effect of the different modifiers and the pressure, on the chromatographic parameters was also evaluated. In general, the alcohol modifiers provided better results than acetonitrile, and all the compounds could be separated with these two columns, but the selection of the column depends on the kind of compound.