Environmental analysis improving selectivity

The use of collision-induced dissociation (CID) and MS/MS techniques in conjunction with the API interfaces has dramatically impacted the fleld of environmental analysis. These techniques are now preferred for the determination of triazine compounds in water, soil, crops, etc., owing to the significant improvements in selectivity obtained via the monitoring of precursor-product ion pairs and increased sensitivity due to the reduction of chemical noise. 

The quantitation of trace and ultratrace components in complex samples of environmental, clinical, or industrial origin represents an important task of modern analytical chemistry. In the analysis of such dilute samples, it is often necessary to employ some type of preconcentration step prior to the actual quantitation. This happens when the analyte concentration is below the detection limit of the instrumental technique applied. Besides its main enrichment objective, the preconcentration step may serve to isolate the analyte from the complex matrix, and hence to improve selectivity and stability. 

Stationary phase technology has also seen significant improvements over the past years. The silica base material is nowadays often a hybrid material, synthesized from tetraalkoxysilanes and functionalized trialkoxysilanes, for example, methyl-trimethoxysilane (MTMS). The introduction of alkyl-trialkoxysilanes into the silica backbone makes the material more resistant to hydrolytic attack and also improves their separation behavior for basic analytes.30 C18 (= octadecylsilane) stationary phases are still the materials typically used in environmental analysis, and the enormous choice of materials with gradually different properties allows columns to be selected that are particularly well suited to a given separation task.31 Reversed phase separations with materials of shorter alkylsilane chain length (C8, C4, and Cl) are less frequently used. 

It is important to note that LCA is a tool to evaluate all environmental effects of a product or process throughout its entire life cycle. This includes identifying and quantifying energy and materials used and wastes released to the environment, assessing their environmental impact, and evaluating opportunities for improvement. LCA can also be used in various ways to evaluate alternatives including in-process analysis, material selection, product evaluation, product comparison, and policy-... 

Much of the work in the past decade on IC development has been in the areas of selectivity improvement to allow more complex application (particularly relevant to environmental analysis), and improved detection methods for enhanced sensitivity and selectivity. 

On the basis of the diversity of applications presented in this chapter, it becomes clear that CE has found a niche among separation techniques for environmental analysis. Future directions will likely include refinement of preconcentration strategies and further detector improvements to achieve the desirable low-concentration limits of detection. In addition, with the consolidation of CE-MS technology, more robust methods are likely to emerge with enhanced sensitivity and superior selectivity, improving further the acceptance of CE in the routine determination of pollutants in real samples. 

Immunoassays represent very selective and sensitive techniques that have found application in several areas such as clinical chemistry, bioanalysis, pharmaceutical analysis, toxicological analysis, and environmental analysis. The first immunoassays developed were radioimmunoassays, which are very sensitive however, one drawback is the need to work radiochemicals. To circumvent the drawbacks, other labels such as enzymes in combination with photometric measurement have been introduced, however, at the expense of sensitivity. With the development of fluoro-immunoassays (FIAs) an improvement in sensitivity was obtained and by introducing chemiluminescence in immunoassays, a sensitivity equivalent to radioimmunoassays was achieved. In this article, different variations and techniques of luminescence immunoassays are described. 

Yang and Cheng (2003) have also reported the metal uptake abiUties of macro cyclic diamine derivative of chitosan. The polymer has high metal uptake abilities, and the selectivity property for the metal ions was improved by the incorporation of azacrown ether groups in the chitosan. The selectivity for adsorption of metal ions on polymer was found to be Ag+> Co >Ci. These results reveal that the new type chitosan-crown ethers will have wide ranging applications for the separation and concentration of heavy metal ions in environmental analysis. 

Given the concerns about the use of toxic organic solvents in food chemistry, many new techniques have been developed to overcome or minimize this problem. For instance, environmentally clean extraction techniques, such as those based on the use of compressed fluids (pressurized liquids, PLE supercritical fluids, SFE and subcritical water, SWE or PHWE), are widely used as alternatives to conventional procedures, such as solid—liquid extraction (SEE), liquid—liquid extraction (LLE), and the like. These alternative processes have in common the use of lower amount of solvents (from hundred milliliters to few milliliters), the lack of toxic residues, higher efficiency extraction (in terms of yields and energy used), and the improved selectivity of the process. SFE has been used in food analysis as a sample preparation technique, mainly for lipophilic compounds, while PLE has been extensively used for many compositional food applications, because the selectivity of this technique... 

Historically, electrochemical stripping analysis, commonly using anodic stripping voltammetry (ASV), has been widely recognized as a powerful technique for heavy-metal detection because of the simplicity of the instrument as well as its moderate cost and portability. Moreover, the ASV technique combined with SPEs can handle all scenarios that require rapid, inexpensive, sensitive, and accurate determination in the field of environmental monitoring. Most studies of heavy-metal determination using SPEs show that mercury, gold, silver, bismuth, or other materials that modify the surface of SPEs can improve selectivity or sensitivity. ... 

The accurate measurement of a specific compound in a complex matrix, that is known as one of the oldest and most important challenges in analytical chemistry, can be carried out by following two main approaches (1) improving selectivity toward the detection system by using selective (bio)sensors, or (2) improving selectivity toward separation systems with nonspecific detectors coupled after the separation of sample mixture. In this section, according to this principle, an overview of the utilization of microfiuidic platforms with electrochemical detection for environmental analysis will be presented. First, selected examples of those microfiuidic platforms used as separation systems will be reported, followed by the implementation of (bio)sensors in microfiuidic platforms for the analysis of species of environmental interest. 

The purpose of this chapter is to describe the analytical methods that are available for detecting and/or measuring and monitoring lead in environmental media and in biological samples. The intent is not to provide an exhaustive list of analytical methods that could be used to detect and quantify lead. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used to detect lead in environmental samples are the methods approved by federal organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that refine previously used methods to obtain lower detection limits, and/or to improve accuracy, precision, and selectivity. 

Methods for determining acrylonitrile in environmental samples are quite good. It may be assumed that the normal incentives for both research and the development of commercial methods of analysis will result in new analytical methods for acrylonitrile that have improved sensitivity and selectivity. Degradation products of acrylonitrile in environmental media are difficult to determine. This difficulty is not as much an analytical problem as it is a problem of knowing the fundamental environmental chemistry of these compounds in water, soil, air and biological systems. 

Here, the mixture analytical FIA-MS-MS approach reached its limitation to identify compounds. Hence, LC separations prior to MS analysis are essential to separate compounds with the same m/z ratio but with different structures. The behaviour in the LC separation will be influenced by characteristic parameters of the surfactant such as linear or strongly branched alkyl chain, the type, the number and the mixture of glycolether groups—PEG and/or PPG—and the ethoxylate chains. The retardation on SPE materials applied for extraction and/or concentration also depends on these properties and can therefore be used for an appropriate pre-separation of non-ionic surfactants in complex environmental samples as well as in industrial blends and household detergent formulations. A sequential selective elution from SPE cartridges using solvents or their mixtures can improve this preseparation and saves time in the later LC separation [22],... 

Research is being conducted at the State University of New York at Albany, sponsored by the National Institute of Environmental Health Sciences, to improve chemical analysis of environmental media for PCBs and selected pesticides, including mirex. No other studies involving mirex or chlordecone were located in the FEDRIP database. 

---