Analytical methods spectrometry

Non-exhaustive summary of analytical methods using mass spectrometry. 

Mass spectrometry (Section 13 22) Analytical method in which a molecule is ionized and the vanous 10ns are exam ined on the basis of their mass to charge ratio... 

Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of... 

The nitroparaftins have been determined by procedures such as fractionation, titration, colorimetry, kifrared spectroscopy, mass spectrometry, and gas chromatography. The early analytical methods and uses of polynitroparaftins as analytical reagents have been reviewed (11). More recent quaHtative and quantitative methods have also been reviewed (83). 

Analytical methods iaclude thin-layer chromatography (69), gas chromatography (70), and specific methods for determining amine oxides ia detergeats (71) and foods (72). Nuclear magnetic resonance (73—75) and mass spectrometry (76) have also been used. A frequentiy used procedure for iadustrial amine oxides (77) iavolves titratioa with hydrochloric acid before and after conversion of the amine to the quaternary ammonium salt by reaction with methyl iodide. A simple, rapid quaHty control procedure has been developed for the deterrniaation of amine oxide and unreacted tertiary amine (78). 

There are a variety of analytical methods commonly used for the characterization of neat soap and bar soaps. Many of these methods have been pubUshed as official methods by the American Oil Chemists Society (29). Additionally, many analysts choose United States Pharmacopoeia (USP), British Pharmacopoeia (BP), or Pood Chemical Codex (FCC) methods. These methods tend to be colorimetric, potentiometric, or titrametric procedures. However, a variety of instmmental techniques are also frequendy utilized, eg, gas chromatography, high performance Hquid chromatography, nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry. 

A definitive method for stmctural deterrnination is x-ray crystallography. Extensive x-ray crystal stmcture deterrninations have been done on a wide variety of steroids and these have been collected and Hsted (270). In addition, other analytical methods for steroid quantification or stmcture determination include, mass spectrometry (271), polarography, fluorimetry, radioimmunoassay (264), and various chromatographic techniques (272). 

Numerous methods have been pubUshed for the determination of trace amounts of tellurium (33—42). Instmmental analytical methods (qv) used to determine trace amounts of tellurium include atomic absorption spectrometry, flame, graphite furnace, and hydride generation inductively coupled argon plasma optical emission spectrometry inductively coupled plasma mass spectrometry neutron activation analysis and spectrophotometry (see Mass spectrometry Spectroscopy, optical). Other instmmental methods include polarography, potentiometry, emission spectroscopy, x-ray diffraction, and x-ray fluorescence. 

The complex of the following destmctive and nondestmctive analytical methods was used for studying the composition of sponges inductively coupled plasma mass-spectrometry (ICP-MS), X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and atomic absorption spectrometry (AAS). Techniques of sample preparation were developed for each method and their metrological characteristics were defined. Relative standard deviations for all the elements did not exceed 0.25 within detection limit. The accuracy of techniques elaborated was checked with the method of additions and control methods of analysis. 

Identification of stmctures of toxic chemicals in environmental samples requires to use modern analytical methods, such as gas chromatography (GC) with element selective detectors (NPD, FPD, AED), capillary electrophoresis (CE) for screening purposes, gas chromatography/mass-spectrometry (GC/MS), gas chromatography / Fourier transform infra red spectrometry (GC/FTIR), nucleai magnetic resonance (NMR), etc. 

All instmmental analytical methods can be analyzed as the spectrometry of zeroth, first, second and higher orders. 

Inductively coupled plasma-mass spectrometry (ICP-MS) is a multielement analytical method with detection limits which are, for many trace elements, including the rare earth elements, better than those of most conventional techniques. With increasing availability of ICP-MS instalments in geological laboratories this method has been established as the most prominent technique for the determination of a large number of minor and trace elements in geological samples. 

The abundance of a trace element is often too small to be accurately quantihed using conventional analytical methods such as ion chromatography or mass spectrometry. It is possible, however, to precisely determine very low concentrations of a constituent by measuring its radioactive decay properties. In order to understand how U-Th series radionuclides can provide such low-level tracer information, a brief review of the basic principles of radioactive decay and the application of these radionuclides as geochronological tools is useful. " The U-Th decay series together consist of 36 radionuclides that are isotopes (same atomic number, Z, different atomic mass, M) of 10 distinct elements (Figure 1). Some of these are very short-lived (tj j 1 -nd are thus not directly useful as marine tracers. It is the other radioisotopes with half-lives greater than 1 day that are most useful and are the focus of this chapter. 

In looking for the mechanism, many intermediates are assumed. Some of these are stable molecules in pure form but very active in reacting systems. Other intermediates are in very low concentration and can be identified only by special analytical methods, like mass spectrometry (the atomic species of hydrogen and halogens, for example). These are at times referred to as active centers. Others are in transition states that the reacting cheimicals form with atoms or radicals these rarely can be isolated. In heterogeneous catalytic reaction, the absorbed reactant can... 

Although GC/MS is the most widely used analytical method that combines a chromatographic separation with the identification power of mass spectrometry, it is not the only one. Chemists have coupled mass spectrometers to most of the instruments that are used to separate mixtures. Perhaps the ultimate is mass spectrometry/mass spectrometry (MS/MS), in which one mass spectrometer generates and separates the molecular ions of the components of a mixture and a second mass spectrometer examines their fragmentation patterns ... 

Electrospray ionization mass spectrometry (ESI-MS) is an analytical method for mass determination of ionized molecules. It is a commonly used method for soft ionization of peptides and proteins in quadmpole, ion-trap, or time-of-flight mass spectrometers. The ionization is performed by application of a high voltage to a stream of liquid emitted from a capillaty. The highly charged droplets are shrunk and the resulting peptide or protein ions are sampled and separated by the mass spectrometer. 

Nuclear magnetic resonance (NMR) spectrometry has seldom been used as a quantitative analytical method but can have some practical importance in the characterization of surfactants [296-298]. 13C-NMR spectrometry has been used for the qualitative and also quantitative analysis of dodecyl, tetradecyl, and cetyl sulfates [299]. H- and, 3C-NMR spectra of sodium dodecyl sulfate are given by Mazumdar [300]. 

Castiglioni S, Bagnati R, Calamari D, Fanelli R, Zuccato E (2005) A multiresidue analytical method using solid-phase extraction and high-pressure liquid chromatography tandem mass spectrometry to measure pharmaceuticals of different therapeutic classes in urban waste-waters. J Chromatogr A 1092 206-215... 

Gros M, Petrovic M, Barcelo D (2006) Development of a multi-residue analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS-MS) for screening and trace level determination of pharmaceuticals in surface and wastewaters. Talanta 70 (4) 678-690... 

For many years, electron ionization, then more usually known as electron impact, was the only ionization method used in analytical mass spectrometry and the spectra encountered showed exclusively the positively charged species produced during this process. Electron ionization also produces negatively charged ions although these are not usually of interest as they have almost no structural significance. Other ionization techniques, such as Cl, FAB, thermospray, electrospray and APCI, however, can be made to yield negative ions which are of analytical utility. 

GC/MS has been employed by Demeter et al. (1978) to quantitatively detect low-ppb levels of a- and P-endosulfan in human serum, urine, and liver. This technique could not separate a- and P-isomers, and limited sensitivity confined its use to toxicological analysis following exposures to high levels of endosulfan. More recently, Le Bel and Williams (1986) and Williams et al. (1988) employed GC/MS to confirm qualitatively the presence of a-endosulfan in adipose tissue previously analyzed quantitatively by GC/ECD. These studies indicate that GC/MS is not as sensitive as GC/ECD. Mariani et al. (1995) have used GC in conjunction with negative ion chemical ionization mass spectrometry to determine alpha- and beta-endosulfan in plasma and brain samples with limits of detection reported to be 5 ppb in each matrix. Details of commonly used analytical methods for several types of biological media are presented in Table 6-1. 

In addition to high sensitivity, a requirement for any acceptable analytical method is high specificity because at very low levels few confirmatory procedures can be used to establish the identity of a particular compound. A method which uniquely combines high sensitivity with high specificity is high resolution mass spectrometry. We have used this method as the basis for an approach which we believe will make possible a meaningful assessment of TCDD levels in the environment. 

Several methods are available for the analysis of trichloroethylene in biological media. The method of choice depends on the nature of the sample matrix cost of analysis required precision, accuracy, and detection limit and turnaround time of the method. The main analytical method used to analyze for the presence of trichloroethylene and its metabolites, trichloroethanol and TCA, in biological samples is separation by gas chromatography (GC) combined with detection by mass spectrometry (MS) or electron capture detection (ECD). Trichloroethylene and/or its metabolites have been detected in exhaled air, blood, urine, breast milk, and tissues. Details on sample preparation, analytical method, and sensitivity and accuracy of selected methods are provided in Table 6-1. 

Reliable analytical methods are available for determination of many volatile nitrosamines at concentrations of 0.1 to 10 ppb in a variety of environmental and biological samples. Most methods employ distillation, extraction, an optional cleanup step, concentration, and final separation by gas chromatography (GC). Use of the highly specific Thermal Energy Analyzer (TEA) as a GC detector affords simplification of sample handling and cleanup without sacrifice of selectivity or sensitivity. Mass spectrometry (MS) is usually employed to confirm the identity of nitrosamines. Utilization of the mass spectrometer s capability to provide quantitative data affords additional confirmatory evidence and quantitative confirmation should be a required criterion of environmental sample analysis. Artifactual formation of nitrosamines continues to be a problem, especially at low levels (0.1 to 1 ppb), and precautions must be taken, such as addition of sulfamic acid or other nitrosation inhibitors. The efficacy of measures for prevention of artifactual nitrosamine formation should be evaluated in each type of sample examined. 

PLC is used for separations of 2 to 5 mg of sample on thin-layer chromatography (TLC) plates (0.25-nun layer thickness) or high-performance TLC (HPTLC) plates (0.1-mm thickness). In these instances, the method is termed micropreparative TLC. The isolation of one to five compounds in amounts ranging from 5 to 1000 mg is carried out on thicker layers. PLC is performed for isolation of compounds to be used in other tasks, i.e., further identification by various analytical methods, such as ultraviolet (UV) solution spectrometry [1] or gas chromatography/mass spectrometry (GC/MS) [2], obtaining analytical standards, or investigations of chemical or biological properties [3]. 

The most significant differences (i.e. independence) in the analytical methods are provided in the final chromatographic separation and detection step using GC/ MS and LC-FL. GC and reversed-phase LG provide significantly different separation mechanisms for PAHs and thus provide the independence required in the separation. The use of mass spectrometry (MS) for the GC detection and fluorescence spectroscopy for the LG detection provide further independence in the methods, e.g. MS can not differentiate among PAH isomers whereas fluorescence spectroscopy often can. For the GC/MS analyses the 5% phenyl methylpolysiloxane phase has been a commonly used phase for the separation of PAHs however, several important PAH isomers are not completely resolved on this phase, i.e. chrysene and triphenylene, benzo[b]fluoranthene and benzofjjfluoranthene, and diben-z[o,h]anthracene and dibenz[a,c]anthracene. To achieve separation of these isomers, GC/MS analyses were also performed using two other phases with different selectivity, a 50% phenyl methylpolysiloxane phase and a smectic liquid crystalline phase. 

A further extension of the DFG S19 method was achieved when polar analytes and those unsuitable for GC were determined by LC/MS or more preferably by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Triple-quadrupole MS/MS and ion trap MS" have become more affordable and acceptable in the recent past. These techniques provide multiple analyte methods by employing modes such as time segments, scan events or multiple injections. By improving the selectivity and sensitivity of detection after HPLC separation, the DFG S19 extraction and cleanup scheme can be applied to polar or high molecular weight analytes, and cleanup steps such as Si02 fractionation or even GPC become unnecessary. 

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

---