Clean-up of aqueous acetone vegetable extracts by solid-matrix partition for pyrethroid residue determination by gas chromatography-electron-capture detection.

Disposable, ready-to-use cartridges filled with macroporous diatomaceous material are used to carry out a partition clean-up that, in a single step, is capable of transferring pesticide residues from aqueous acetone extracts into light petroleum-dichloromethane (75:25, v/v). This procedure takes the place of some functions (such as separatory-funnel partition, drying over anhydrous sodium sulphate and partial adsorption clean-up) usually performed by separate steps in classical schemes. Fourteen pyrethroid pesticides, including tefluthrin, tetramethrin, cyphenothrin, cyfluthrin, flucythrinate, tau-fluvalinate, deltamethrin, bioallethrin, fenpropathrin, lambda-cyhalothrin, permethrin, alpha-cypermethrin, esfenvalerate and tralomethrin were determined using the described procedure with satisfactory recoveries for most of them, at spiking levels ranging from 0.08 to 0.82 mg/kg for the different compounds. Crops subjected to the described procedure included strawberry, apple, and orange gave extracts containing a mass of co-extractives that was between 5 and 30 mg. Compared with classical schemes, the described procedure is simple, less labour intensive, allows parallel handling of several extracts and does not require the preparation and maintenance of equipment. Troublesome emulsions such as those frequently observed in separation funnel partitioning do not occur.

Selective extraction of pyrethroid pesticide residues from milk by solid-matrix dispersion.

A rapid procedure has been developed that allows a single-step, selective extraction and clean-up of pyrethroid (PYR) pesticide residues from milk dispersed on solid-matrix diatomaceous material filled into disposable cartridges and eluted by means of light petroleum saturated with acetonitrile and ethanol. The extract was cleaned up by high-performance size-exclusion chromatography. Determinations were carried out by gas chromatography with electron-capture detection. Recovery experiments were carried out on homogenized commercial milk (3.6% fat content) that was spiked with solutions of 14 PYR pesticides, viz., tefluthrin, tetramethrin, cyphenothrin, cyfluthrin, flucythrinate, fluvalinate, deltamethrin, bioallethrin, fenpropathrin, lambda-cyhalothrin, permethrin, alpha-cypermethrin, esfenvalerate and tralomethrin, at levels ranging from 0.04 to 0.41 mg/kg for the different PYR pesticides. Average recoveries were in the range 60-119% for the different PYR pesticides, with relative standard deviations from ca. 2.5 to 14.4%. Coextracted fatty material amounted to an average of ca. 5 mg/ml of milk. The sole extraction step requires about 30 min. The main advantages of the procedure are that extraction of PYR pesticides (with a minimum carry over of fat) is performed in a single step, emulsions do not occur, several samples can be run in parallel by a single operator, reusable glassware is not needed and simple operations are required.

Anatoxin-A and a previously unknown toxin in Anabaena planctonica from blooms found in Lake Mulargia (Italy).

Algal extracts of Anabaena planctonica from Lake Mulargia in Italy were tested for toxins by mouse bioassay, the Microtox system, and GC-MS and HPLC chromatography. Anatoxin-a was identified by GC-MS after derivatization with pentafluorobenzyl bromide. Hepatotoxins were also present and are perhaps related to the microcystins present in other species of Anabaena.

Fatty acid profiles in the family Leptospiraceae.

Fatty acid profiles of six leptospira strains representative of genera, species, and serogroups within the family Leptospiraceae were determined by gas liquid chromatography (GLC) of fatty acid methyl ester (FAME) derivatives. The influence of methodological and biological variables on FAME profiles of the same strain was tested. FAME profiles were sharply affected by the fatty acid composition of the culture medium but not by the growth phase. Twenty-four FAME peaks were selected on the basis of their presence in repeated gas chromatographic runs of single strains. Inter-strain divergences of FAME profiles were quantified by linear regression analysis (LR). Step-wise divergences in FAME profiles were observed between strains at serogroup, species, and genus levels.