Qualitative analysis mass spectrometry

Application of mass spectrometry to analysis of additives in polymers is mainly used as a qualitative tool and relates to three main areas ... 

Spark Source Mass Spectrometry (SSMS) is a method of trace level analysis—less than 1 part per million atomic (ppma)—in which a solid material, in the form of two conducting electrodes, is vaporized and ionized by a high-voltage radio frequency spark in vacuum. The ions produced from the sample electrodes are accelerated into a mass spectrometer, separated according to their mass-to-charge ratio, and collected for qualitative identification and quantitative analysis. 

Multidimensional gas chromatography has also been used in the qualitative analysis of contaminated environmental extracts by using spectral detection techniques Such as infrared (IR) spectroscopy and mass spectrometry (MS) (20). These techniques produce the most reliable identification only when they are dealing with pure substances this means that the chromatographic process should avoid overlapping of the peaks. 

In this chapter, the main aspects of mass spectrometry that are necessary for the application of LC-MS have been described. In particular, the use of selected-ion monitoring (SIM) for the development of sensitive and specific assays, and the use of MS-MS for generating structural information from species generated by soft ionization techniques, have been highlighted. Some important aspects of both qualitative and quantitative data analysis have been described and the power of using mass profiles to enhance selectivity and sensitivity has been demonstrated. 

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. 

All previous discussion has focused on sample preparation, i.e., removal of the targeted analyte(s) from the sample matrix, isolation of the analyte(s) from other co-extracted, undesirable sample components, and transfer of the analytes into a solvent suitable for final analysis. Over the years, numerous types of analytical instruments have been employed for this final analysis step as noted in the preceding text and Tables 3 and 4. Overall, GC and LC are the most often used analytical techniques, and modern GC and LC instrumentation coupled with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) detection systems are currently the analytical techniques of choice. Methods relying on spectrophotometric detection and thin-layer chromatography (TLC) are now rarely employed, except perhaps for qualitative purposes. 

Dear, G.J., Fraser, I.J., Patel, D.K., Long, J., and Pleasance, S., Use of liquid chromatography-tandem mass spectrometry for the quantitative and qualitative analysis of an antipsychotic agent and its metabolites in human plasma and urine, /. Chromatogr. A, 794, 27, 1998. 

Mass spectrometry involves the study of ions in the vapour phase. Mass spectrometers are analytical instruments that convert neutral molecules into gaseous ions and separate those ions according to the ratio of their mass-to-charge (m/z) The location of the mass lines provides a qualitative analysis, and their intensity, mostly measured relative to that of the matrix element or a suitable internal standard, gives a quantitative analysis. 

When fresh or frozen tissue is used for proteomic analyses, the results cannot be related directly to the clinical course of diseases in a timely manner. Instead, researchers frequently reduce the number of interesting proteins to a manageable number and then attempt to use immunohistochemistry to understand the implications of proteomic changes in archival formalin-fixed, paraffin-embedded (FFPE) tissue for which the clinical course has been established.3 Unfortunately, immunohistochemistry is a semiquantitative pro-teomic method, and the choice of interesting proteins must occur without advance knowledge of the clinical course of the disease or the response to therapy. If routinely fixed and embedded archival tissues could be used for standard proteomic methods such as 2-D gel electrophoresis and mass spectrometry (MS), these powerful techniques could be used to both qualitatively and quantitatively analyze large numbers of tissues for which the clinical course has been established. However, analysis of archival FFPE tissues by... 

Only arc/spark, plasma emission, plasma mass spectrometry and X-ray emission spectrometry are suitable techniques for qualitative analysis as in each case the relevant spectral ranges can be scanned and studied simply and quickly. Quantitative methods based on the emission of electromagnetic radiation rely on the direct proportionality between emitted intensity and the concentration of the analyte. The exact nature of the relation is complex and varies with the technique it will be discussed more fully in the appropriate sections. Quantitative measurements by atomic absorption spectrometry depend upon a relation which closely resembles the Beer-Lambert law relating to molecular absorption in solution (p. 357 etal.). 

In order to perform qualitative and quantitative analysis of the column effluent, a detector is required. Since the column effluent is often very low mass (ng) and is moving at high velocity (50-100 cm/s for capillary columns), the detector must be highly sensitive and have a fast response time. In the development of GC, these requirements meant that detectors were custom-built they are not generally used in other analytical instruments, except for spectroscopic detectors such as mass and infrared spectrometry. The most common detectors are flame ionization, which is sensitive to carbon-containing compounds and thermal conductivity which is universal. Among spectroscopic detectors, mass spectrometry is by far the most common. 

J.H. Beynon, Qualitative analysis of organic compounds by mass spectrometry, Nature, 174 (1954) 735-737. 

Mass spectrometry offers a special advantage over other detection schemes for instrumental chromatography because the mass spectra of the mixture components are acquired, providing a very powerful qualitative analysis tool for these components. 

We discussed the fundamentals of mass spectrometry in Chapter 10 and infrared spectrometry in Chapter 8. The quadrupole mass spectrometer and the Fourier transform infrared spectrometer have been adapted to and used with GC equipment as detectors with great success. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectrometry (GC-IR) are very powerful tools for qualitative analysis in GC because not only do they give retention time information, but, due to their inherent speed, they are also able to measure and record the mass spectrum or infrared (IR) spectrum of the individual sample components as they elute from the GC column. It is like taking a photograph of each component as it elutes. See Figure 12.14. Coupled with the computer banks of mass and IR spectra, a component s identity is an easy chore for such a detector. It seems the only real... 

NMR) [24], and Fourier transform-infrared (FT-IR) spectroscopy [25] are commonly applied methods. Analysis using mass spectrometric (MS) techniques has been achieved with gas chromatography-mass spectrometry (GC-MS), with chemical ionisation (Cl) often more informative than conventional electron impact (El) ionisation [26]. For the qualitative and quantitative characterisation of silicone polyether copolymers in particular, SEC, NMR, and FT-IR have also been demonstrated as useful and informative methods [22] and the application of high-temperature GC and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is also described [5]. 

---