Liquid Chromatography/Mass Spectrometry in Environmental Analysis

Abstract

AbstractOn‐line liquid chromatography/mass spectrometry (LC/MS) has become a powerful technique in environmental analysis because of the separation capabilities of liquid chromatography (LC) and the detection and identification potential of mass spectrometry (MS), the characteristics of both methods making coupling very attractive. Among the interfacing systems used to couple LC with MS, those based on the atmospheric pressure ionization (API) offer advantages in terms of sensitivity and capability to analyze highly polar, ionic, heat sensitive and high‐molecular‐weight substances. Further, the on‐line coupling of chromatographic separations with element‐selective detection systems such as inductively coupled plasma mass spectrometry (ICP/MS) is an attractive technique for trace element speciation.The main advantage of LC/MS lies in its ability to provide qualitative information (including molecular mass and fragmentation pattern) on the detected peaks. In addition, when all the ionization parameters are optimized, quantitative analyses can be carried out and low detection limits (at the ppb level) are obtained performing selective ion detection.In environmental analysis, universal, selective and sensitive methods are needed to afford the assay of a wide variety of target and nontarget substances. Even though gas chromatography/mass spectrometry (GC/MS) is extensively applied to the analysis of organic contaminants in several matrices, LC/MS offers major advantages over GC/MS for analyzing polar, nonvolatile and thermolabile compounds. Ultraviolet (UV) or diode‐array detector (DAD) are commonly used to perform detection in high‐performance liquid chromatography (HPLC). However, UV‐based detection methods for HPLC have several disadvantages deriving from nonspecific detection and lack of sensitivity. A more reliable identification is sometimes possible using DAD for certain compound classes, e.g. nitrophenols, in environmental samples; however, structural information is lacking for some classes of pollutants, among which are some pesticides, because their UV spectra are often almost identical. Using unspecific LC detectors, detection may be complicated by false‐positive results; in such cases, MS has proved to be an extremely valuable technique for unequivocal identification of micro‐contaminants in a variety of environmental samples.This overview discusses recent instrumental developments concerning mass analyzers of the mass spectrometers and on‐line sample treatment procedures, with emphasis on the environmental field. Among the environmental applications of LC/MS, methods for the analysis of pesticides, polycyclic aromatic hydrocarbons (PAHs), dyes, surfactants, inorganic and organometallic compounds in environmental samples are discussed.