Trace analysis of environmental matrices by large-volume injection and liquid chromatography-mass spectrometry

The time-honored convention of concentrating aqueous samples by solid-phase extraction (SPE) is being challenged by the increasingly widespread use of large-volume injection (LVI) liquid chromatography–mass spectrometry (LC–MS) for the determination of traces of polar organic contaminants in environmental samples. Although different LVI approaches have been proposed over the last 40 years, the simplest and most popular way of performing LVI is known as single-column LVI (SC-LVI), in which a large-volume of an aqueous sample is directly injected into an analytical column. For the purposes of this critical review, LVI is defined as an injected sample volume that is ≥10% of the void volume of the analytical column. Compared with other techniques, SC-LVI is easier to set up, because it requires only small hardware modifications to existing autosamplers and, thus, it will be the main focus of this review. Although not new, SC-LVI is gaining acceptance and the approach is emerging as a technique that will render SPE nearly obsolete for many environmental applications.In this review, we discuss: the history and development of various forms of LVI; the critical factors that must be considered when creating and optimizing SC-LVI methods; and typical applications that demonstrate the range of environmental matrices to which LVI is applicable, for example drinking water, groundwater, and surface water including seawater and wastewater. Furthermore, we indicate direction and areas that must be addressed to fully delineate the limits of SC-LVI

Capillary zone electrophoretic separation of beta-blockers using citrate buffer at low pH

no abstrac

Enantiomeric separation by capillary electrophoresis using a soluble neutral beta-cyclodextrin polymer

Enantiomers of several racemic basic compounds of pharmaceutical interest and three tryptophan derivatives were investigated by capillary electrophoresis employing a soluble ß-cyclodextrin polymer and native ß-cyclodextrin. The effects of the concentration of the polymer added to the background electrolyte and of the pH of the buffer on the effective mobility and resolution of the studied compounds were examined. The ß-cyclodextrin polymer showed a higher stereoselectivity than the parent ß-cyclodextrin. Enantionselectivity and resolution were influenced by the concentration of the ß-cyclodextrin polymer and the background electrolyte. A pH study, carried out in the pH range 2.7–6, showed that an increase in pH caused a general decrease in both resolution and selectivity. The best results for the enantiomeric separation of the basic compounds studied were obtained at pH 2.7

Capillary electrophoretic separation of herbicidal enantiomers applying ergot alkaloids

The capillary electrophoretic separation of some herbicidal enantiomers is shown applying 1-allylterguride as chiral selector. Baseline separation is shown for the enantiomers of fluazifop, halossifop and fenoxaprop, whereas the optical isomers of flamprop could be partially resolved. Separation times are short compared to similar analyses, applying HPLC and a terguride chiral stationary phase. The degree of dissociation of the acidic analytes, as well as the amount of methanol present in the background electrolyte, are shown to have a major influence on enantioresolution, as expected form earlier studies