Mass spectroscopy sensitivity

Anbar, Determination of Subprogram Amounts of Chemical Agents in the Atmosphere , Edge-woodArs Contract Rept EC-CR-74028, SRI Proj 3122 (1974) ( A method of mass spectroscopy, employing a silicone membrane and field ionization, which involves other new techniques, is presented which is sensitive to picogram amts of chemical agents in the atm)... 

Figure 7b also illustrates the high detection sensitivity of the FTMS instrument. We calculate that the CO peak corresponds to approximately 5000 ions in the analyzer cell. In Figure 7a, the number of ions with m/z 43 was calculated to be approximately 20 million. A point to note is that In FTMS the sensitivity increases with resolution whereas it decreases with other mass spectroscopies. 

Principles and Characteristics The most commonly used and widely known technique coupled to gas chromatography is mass spectroscopy. In early couplings, with packed GC columns being the major problem encountered, elimination of the carrier gas at relatively high flow-rates (25mLmin 1), resulted in a significant loss of sensitivity. With the advent of open tubular devices, the column flow could be passed directly into the mass spectrometer. GC-MS is typically... 

On line mass spectroscopy is a very sensitive method capable of giving on-line responses in less than 0.2 s [11,12],... 

Figure 5.10 is the dynamic TGA scan of neat PTFE in air and N2. Under each atmosphere studied, it is readily apparent that the onset of degradation occurs at about 500°C. TGA data are also in excellent agreement with a more sensitive and structurally informative pyrolysis/mass spectroscopy analysis. Figure 5.11 is a... 

For this method, the drug candidate is labeled with a radioisotope, such as carbon-14. The AD ME of the compound within the body can be monitored by analyzing samples using high sensitivity instrumentation, for example, accelerator mass spectroscopy. 

Frolich and colleagues (1998) analyzed ACh in human CSF by different methods, which included thermospray/mass spectroscopy, HPLC/mass spectroscopy, HPLC-EC Pt electrode and gas chromatogra-phy/mass spectroscopy (GC/MS). An SPE extraction was used for cleanup and concentration. Samples were run with and without the IMER to rule out any interference by physostigmine, a cholinesterase inhibitor, in the HPLC-EC assay. HPLC-EC and GC-MS gave data correlations with similar sensitivities, but the HPLC-EC values were 39% lower. Analysis using thermospray/mass spectroscopy and HPLC/ mass spectroscopy did not provide adequate sensitivity and the data obtained were inconsistent. 

This method suffered from sensitivity problems initially as the bile-acid molecules lack a chromophore, but did offer the distinct advantage that conjugated bile acids could be determined without hydrolysis. The sensitivity issue was addressed by use of fluorescent derivatives such as dimethoxycoumarin esters with a C18 reverse phase column and were able to resolve endogenous mixtures of bile acids. The combination of hplc and mass-spectroscopy detection has further improved the sensitivity along with providing specific identification, important as the resolution of bile acids by hplc is not as good as capillary column glc. ... 

A major consequence of using regulatory limits based on degradant formation, rather than absolute change of the API level in the drug product, is that it necessitates the application and routine use of very sensitive analytical techniques [ 10]. In addition, the need to resolve both structurally similar, as well as structurally diverse degradants of the API, mandates the use of analytical separation techniques, for example, HPLC, CE, often coupled with highly sensitive detection modes, for example, ultraviolet (UV) spectroscopy, fluorescence (F) spectroscopy, electrochemical detection (EC), mass spectroscopy (MS), tandem mass spectroscopy (MS-MS) and so forth. 

Analysis. Be can be quantitatively determined by colorimetry down to 40 ppb using eriochrome cyanine R or acetylacetone. The sensitivity may be improved by electrothermal absorption spectroscopy (ETAS) to 1 ppb and to 0.1 ppb by inductively-coupled plasma emission spectroscopy (ICPES) or inductively-coupled plasma mass spectroscopy (ICPMS). A simple spot test for qualitative detection of Be is one with quinalizarin in alcoholic NaOH which can detect 3 ppm. The color is produced by both Be and Mg. If the color persists after the addition of Br2 water. Be is present. If the color is bleached. Mg is indicated. 

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