Micro‐extraction techniques in analytical toxicology: short review

Abstract

This paper discusses new developments in plasma micro-extraction techniques in the context of established micro-extraction and protein precipitation methodology. Simple liquid-liquid solvent extraction (LLE) of plasma with direct GC or HPLC analysis of the resulting extract has been used for many years. Butyl acetate and methyl t-butyl ether (MTBE) give efficient extraction of many drugs and metabolites from small volumes of plasma or whole blood at an appropriate pH, and form the upper layer, thus simplifying extract removal. Butyl acetate does not interfere with NPD, ECD or MS in GC, whilst MTBE has a relatively low UV cutoff (220 nm). Thus, HPLC eluents that use a high proportion of an organic component allow MTBE extracts to be analysed directly. 'Salting-out' and extractive derivatization using acetic anhydride or phenylboronic acid can be used with appropriate analytes. As regards protein precipitation, an important consideration is lowering the pH, although this is not feasible with acid-labile analytes. More recent developments include sold-phase micro-extraction (SPME) and liquid-phase micro-extraction (LPME). This latter technique especially may prove invaluable as analytes that cannot easily be extracted with LLE can be isolated simply at low cost with a minimum of apparatus.

Determination of cobalt in water samples by atomic absorption spectrometry after pre-concentration with a simple ionic liquid-based dispersive liquid-liquid micro-extraction methodology

“…Recently, efforts have been placed on miniaturizing the LLE procedure to greatly reduce the amount of organic solvent resulting in the development of micro-extraction methodologies such as liquid-phase micro-extraction (LPME), liquid-liquid micro-extraction (LLME), solidphase micro-extraction (SPME), etc. [29,30]. DLLME is a mode of LPME, which is based on the same principles as the traditional LLE, but with the advantages of simplicity, rapidity, low sample volume, low cost, high recovery, and a high enrichment factor [31].…”

Laser capture sampling and analytical issues in proteomics

“…Homogenization, ultrasonication, freeze-thawing, pressure cycling, and bead mills have all been employed for protein extraction [40][41][42][43][44][45][46][47][48]. One method that is effective for a wide range of biological samples is cellular homogenization.…”

Flame Atomic Absorption Spectrometry Determination of Trace Amounts of Nickel Ions in Water Samples after Ligandless Ultrasound-assisted Emulsification Microextraction

“…[18][19][20] A novel microextraction technique, dispersive liquid-liquid microextraction (DLLME), was recently introduced by Berijani et al 19 based on a ternary component solvent system, like homogeneous liquid-liquid extraction and cloud point extraction (CPE). It has the advantages of simplicity, rapidity, low sample volume, low cost, high recovery, and a high enrichment factor.…”