Mass Spectrometry Tests

Mass spectrometry tests were conducted as described before, with an ion trap mass spectrometer using the second setup whereby HV is directly applied onto the supporting silicon wafer. The same standard peptide as before was used, Glu-Fibrinopeptide B, at a concentration of 1 pM. For the first series of tests, we decided to investigate the range of FIV which would give an electrospray working with solutions of 50 50 MeOH-H20 acidified with 0.1% HCOOH. 

Following this, another series of tests was aimed at varying the composition of the solvent used for preparing the peptide samples. We particularly decided to investigate the water content of the solvent and its influence on the spraying ability. Therefore, we prepared MeOH-H20, 0.1% HCOOH solvent mixtures varying from 50 to 95% H20 so as to prepare peptide samples 

Microfabricated NanoESI Tips Based on a Capillary Slot 

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Mass spectrometry tests were carried out using a LCQ deca XP + ion trap mass spectrometer (Thermo Finnigan, San Jose, CA, USA). The electrospray emitter tip nib structure was placed on a dedicated holder that is introduced in the inlet of the mass spectrometer. A platinum wire was subsequently inserted in the reservoir feature of the nib, and was connected at its other end on a metallic part on the holder where HV is normally applied for ionization purposes. Solutions to be analyzed were dropped in the reservoir feature using a gel-loader tip typically 5-10 pL of sample were deposited in the reservoir. Liquid was subsequently seen to fuse at the tip of the nib due to capillary action in the slot. HV was then applied, and a spray could be observed with HV values in a... 

Screenshot showing the results of a mass spectrometry test on a suspect s blood sample. The molecular weights of various chemicals are shown at right, while the names of the drugs found in the sample are at left. (Patrick Landmann/ Photo Researchers, Inc.)... 

Under these guidelines, the first test is a preliminary screen, usually an immunoassay technique such as EMIT (enzyme multiplied immrmoassay technique). These tests rmdergo strict quality control procedures, and a positive screening test is confirmed with a second more sensitive test — the gas chromatography/mass spectrometry test. 

This accurate measurement of the ratio of abundances of isotopes is used for geological dating, estimation of the ages of antiquities, testing athletes for the use of banned steroids, examining fine details of chemical reaction pathways, and so on. These uses are discussed in this book under various headings concerned with isotope ratio mass spectrometry (see Chapters 7, 14, 15, 16, 17, 47, and 48). 

Specification tests are performed on plant streams once or twice per worker shift, or even more often if necessary, to assure the continuing quahty of the product. The tests are also performed on a sample from an outgoing shipment, and a sample of the shipment is usually retained for checking on possible subsequent contamination. Tests on specialty types of acetone may require sophisticated instmments, eg, mass spectrometry for isotopicaHy labeled acetone. 

In gas chromatography/mass spectrometry (GC/MS), the effluent from a gas chromatograph is passed into a mass spectrometer and a mass spectrum is taken every few milliseconds. Thus gas chromatography is used to separate a mixture, and mass spectrometry used to analyze it. GC/MS is a very powerful analytical technique. One of its more visible applications involves the testing of athletes for steroids, stimulants, and other performance-enhancing drugs. These drugs are converted in the body to derivatives called metabolites, which are then excreted in the... 

Sophisticated analytical techniques, such as mass spectrometry, are not practical for determining complete composition of FCC feedstocks on a routine basis. Simpler empirical correlations are more often used. They require only routine tests commonly performed by the refinery laboratory. They are excellent alternatives, but they have their limitations ... 

Characterizing an FCC feedstock involves determining both its chemical and physical properties. Because sophisticated analytical techniques, such as mass spectrometry, are not practical on a daily basis, physical properties are used. They provide qualitative measurement of the feed s composition. The refinery laboratory is usually equipped to carry out these physical property tests on a routine basis. The most widely used properties are ... 

Thymine, electrostatic potential map of, 1104 structure of, 1101 Thyroxine, biosynthesis of, 551 structure of. 1020 TIme-of-flight (TOP) mass spectrometry, 417-418 Titration curve, alanine, 1023 TMS, see Tetramethylsilane see Trimethylsilyl ether Tollens reagent, 701 Tollens test, 992... 

Figure 5.65 LC-UV and LC-MS-MS (multiple-reaction monitoring (MRM)) traces from the analysis of a enzymatically digested solution of 100 p,g salmon testes DNA (for nomenclature, see text). Reprinted by permission of Elsevier Science from Comparison of negative- and positive-ion electrospray tandem mass spectrometry for the liquid chromatography-tandem mass spectrometry analysis of oxidized deoxynucleosides , by Hua, Y., Wainhaus, S. B., Yang, Y., Shen, L., Xiong, Y., Xu, X., Zhang, F., Bolton, J. L. and van Breemen, R. B., Journal of the American Society for Mass Spectrometry, Vol. 12, pp. 80-87, Copyright 2000 by the American Society for Mass Spectrometry.

The application of a selective pyrolysis process to the recovery of chemicals from waste PU foam is described. The reaction conditions are controlled so that target products can be collected directly from the waste stream in high yields. Molecular beam mass spectrometry is used in small-scale experiments to analyse the reaction products in real time, enabling the effects of process parameters such as temperature, catalysts and co-reagents to be quickly screened. Fixed bed and fluidised bed reactors are used to provide products for conventional chemical analysis to determine material balances and to test the concept under larger scale conditions. Results are presented for the recycling of PU foams from vehicle seats and refrigerators. 12 refs. 

The biodegradation of branched-chain alkanol ethoxyethylates was carried out by the standard OECD confirmatory tests and the metabolites fractionated after solid-phase extraction. The structures of the metabolites were determined by electrospray mass spectrometry and this made it possible to derive a scheme for the partial degradation of the compounds (Di Corcia et al. 1998). 

In the first set of comparison test runs, a 0. lOg of each sulfated sample was examined by TPR in a soak (300°C)-ramp (up to 850°C at 20°C/min.) mode, using propane at 14.2 ml/min as the reactant. In the second set of propane-TPR comparison test mns, another 0. lOg of each sulfated sample was examined by a soak (300°C)-ramp (30°C/min.)-soak (up to 530°C) mode. The reaction products such as SO and HjS released during the course of a TPR run were determined by means of mass spectrometry (Hiden Analytical, HAL-2) in MID mode, monitoring mass numbers 48 for SO fragment from SOj, and 34 for H S. 

Radovic, B. S., Goodacre, R., and Anklam, E. (2001b). Contribution of p)uolysis-mass spectrometry (Py-MS) to authenticity testing of honey. /. Anal. Pyrolysis. 60, 79-87. 

On the other hand, if only specific GC detectors, e.g. the electron capture, nitrogen-phosphorus or flame photometric detectors, are tested, the argument of lack of GC method sensitivity is not acceptable. In most cases mass spectrometric detectors provide the sensitivity and selectivity needed. Unfortunately, tandem mass spectrometry (MS/MS) or MS" detectors for GC are still not widely used in official laboratories, and therefore these techniques are not always accepted for enforcement methods. 

Richter S, Goldberg SA, Mason PB, Traina AJ, Schwieters JB (2001) Linearity tests for secondary electron multipliers used in isotope ratio mass spectrometry. Inti J Mass Spectrom 206 105-127 Rihs S, Condomines M, Sigmarsson O (2000) U, Ra, and Ba incorporation dining precipitation of hydrothermal carbonates imphcations for Ra-Ba dating of impure travertines. Geochim Cosmochim Acta 64 661-671... 

Figure 5. Histogram Th/U for clinopyroxenes in peridotites and pyroxenites from the Ronda peridotite massif Concentrations were measured by isotope dilution mass spectrometry in acid-leached clinopyroxenes. This histogram shows that pyroxenites do not have larger Th/U ratios than peridotites. Thus, the correlation found between ( °Th/ U) and Th/U cannot be explained by mixing of peridotite and pyroxenite melts as advocated in Sigmarsson et al. (1998). Data from Hauri et al. (1994) and Bourdon and Zindler (unpublished). It can be shown with a simple Student t-test that the two populations are indistinguishable.

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