Application of different extraction methods for the determination of selected pesticide residues in sediments.

Using several extraction methods including the QuEChERS approach, samples of both model and natural sediments were prepared. For the isolation of the target group of pesticides, two variants of two complementary extractions had to be used. Resulting extracts were analysed with LC/MS/MS. Selected methods furnishing the best results were validated in the terms of linearity and repeatability. Their limits of detection ranged from 0.1 to 2 ng/g, their limits of quantification from 1 to 6 ng/g and their recovery percentage varied between 46 % and 102 %.

Determination of the purity of ampicillin by micellar electrokinetic chromatography and reversed phase liquid chromatography on a monolithic silica column.

A micellar electrokinetic chromatographic (MEKC) method and a fast reversed-phase liquid chromatographic one have been developed for determining the purity of ampicillin. MEKC separation of ampicillin and its related substances was performed with the use of an untreated fused-silica capillary and 40 mM phosphate-borate buffer, pH 7.5 containing 75 mM SDS. The HPLC method employed a monolithic silica C18 column and a mobile phase composed of phosphate buffer, pH 5.2 and ACN, the flow rate being 4.0 mL/min. Both methods were successfully validated. Linearity, relative response factors, limits of quantitation, intermediate precision, and accuracy were evaluated. The methods proved to be fast, reliable, and sufficiently sensitive and, accordingly, well-suited for control of purity of ampicillin substance, injections, and capsules. A combination of both methods can be very useful in the confirmation of impurity profiles.