Mass spectrometry detection limit

Carboxylic acids The smallest carboxylic acid, formic acid, can be measured using infrared spectroscopy (Table 11.2), since it has characteristic absorption bands. As discussed earlier and seen in Fig. 11.33b, mass spectrometry with chemical ionization using SiF5 also revealed HCOOH in an indoor environment (Huey et al., 1998). However, since the sensitivity in these initial studies was about two orders of magnitude less than that for HN03, the detection limit may be about the same as that for FTIR and TDLS. Formic and acetic acids have been monitored continuously from aircraft (Chapman et al., 1995) and their surface flux determined by eddy correlation (Shaw et al., 1998) using atmospheric pressure ionization mass spectrometry. Detection limits are about 30 ppt. 

Figure 20-9 Flame, furnace, and inductively coupled plasma emission, and inductively coupled plasma-mass spectrometry detection limits (ng/g = ppb). [From R. J. Gill, Am. Lab., November 1993, p. 24F T. T. Nham,...

Grunwald, E. J. (1998). Capillary electrophoresis inductively coupled plasma mass spectrometry Detection limits, sample matrix, and metal-ligand considerations. Unpublished Ms. Thesis, Ohio State University, Columbus. 

Liquid chromatography/mass spectrometry Lower limit of detection Limit of detection Limit of quantitation Florseshoe crab hemocyanin Liquid scintillation counting Matrix-assisted laser desorption/ ionization mass spectrometry m -Maleimidobenzoy 1-A -Hydroxysuccinimide 1 -Cyclohexyl-3-(2-Morptiolino-ethyl)carbodiimide rnetlio-/ -Toluenesulfonate (same as CDI)... 

Liquid Chromatography Mass Spectrometry Coupling Limit of Detection... 

In this regard several sophisticated chromatographic methods, with a quantification limit down to about 0.2 ng/g, have been developed and published for the determination of zearalenone. The methods were mainly based on high-performance liquid chromatography (HPLC) with fluorescence detection (Krska 1998 Visconti and Pascale 1998 Schuhmacher et al. 1998 Tanaka et al. 2000), but HPLC with mass spectrometry detection was also used (Shirai et al. 2000 Josephs et al. 2001). 

Negative chemical ionization (NCI) mass spectrometry detects ABA with a high sensitivity since the negative molecular ion M of methyl ester of ABA is more stable than the positive molecular ion [M] + due to the high electrophilicity of ABA. The NCI mass spectrum shows [M]- at m/z 278 as a base peak, and other fragment ions at m/z 310, 260, 245, 141, and 152.601 The combination of SIM with NCI gives highly selective and sensitive detection of ABA the lowest detection limit is 0.3 pg, which is 200 times lower than that... 

Szpunar, J., McSheehy, S., Polec, K., Vacchina, V., Mounicou, S., Rodriguez, I., Lobinski, R. Gas and liquid chromatography with inductively coupled plasma mass spectrometry detection for environmental speciation analysis - advances and limitations. Spectrochim. Acta Part B 55, 779-793 (2000)... 

We have developed an analogous, but more robust system which is not necessarily constraint by the aforementioned limitations. The obvious extension has been to couple an affinity-based separation with mass spectrometry. Hutchens et al. have shown that affinity probe surfaces can be ust to capture specific protein ligands allowing detection by laser desorption mass spectrometry (. The limitations to their technique have been that the surface area for ligand capture is quite small and salt (or detergent) contaminants are still problematic. Perfusive affinity resins, on the other hand, provide a tremendous surface area for binding. The nature and composition of the solvents required for affinity chromatography, however, are not directly compatible with mass spectrometric analysis. 

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... 

Samples to be examined by inductively coupled plasma and mass spectrometry (ICP/MS) are commonly in the form of a solution that is transported into the plasma flame. The thermal mass of the flame is small, and ingress of excessive quantities of extraneous matter, such as solvent, would cool the flame and might even extinguish it. Even cooling the flame reduces its ionization efficiency, with concomitant effects on the accuracy and detection limits of the ICP/MS method. Consequently, it is necessary to remove as much solvent as possible which can be done by evaporation off-line or done on-line by spraying the solution as an aerosol into the plasma flame. 

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