Methyl quadrupole spectrometer

We use a GC Top 8000 gas chromatograph coupled with a PolarisQ ion-trap mass spectrometer and equipped with an AI3000S autosampler (Thermofinnigan www. thermo.com). The steroids are separated on a DB-1 crosslinked methyl-silicone column, 15 mx 0.25 mm i.d., film thickness 0.25 pm (J W Scientific marketed by Agilent). Helium is used as a carrier gas at a constant pressure of about 35 kPa. A 1-pl aliquot of the final derivatized extract is injected into the system operated in splitless mode (valve opened at 2 min). The GC temperature program is the same described before for the quadrupole GC-MS system. The injector and transfer lines are kept at 260°C and 280°C, respectively. The ion source temperature is 225°C. A damping gas flow of helium is applied to the ion trap. 

Figure F2.4.1 Liquid chromatography/mass spectrometry (LC/MS) analysis of isomeric carotenes in a hexane extract from 0.5 ml human serum. Positive ion electrospray ionization MS was used on a quadrupole mass spectrometer with selected ion monitoring to record the molecular ions of lycopene, p-carotene, and a-carotene at m/z (mass-to-charge ratio) 536. A C30 HPLC column was used for separation with a gradient from methanol to methyl-ferf-butyl ether. The a -trans isomer of lycopene was detected at a retention time of 38.1 min and various c/ s isomers of lycopene eluted between 27 and 39 min. The all-frans isomers of a-carotene and P-carotene were detected at 17.3 and 19.3 min, respectively.

Conventional high pressure NICI spectra were obtained using a Hewlett-Packard 5985B quadrupole GC/MS, as described previously (1). Methane was used as the Cl reagent gas and was maintained in the source at 0.2-0.4 torr as measured through the direct inlet with a thermocouple gauge. A 200 eV electron beam was used to ionize the Cl gas, and the entire source was maintained at a temperature of 200° C. Samples were introduced into the spectrometer via the gas chromatograph which was equipped with a 25 meter fused silica capillary column directly interfaced with the ion source. For all experiments, a column coated with bonded 5% methyl phenyl silicon stationary phase, (Quadrex, Inc.) was used and helium was employed as the carrier gas at a head pressure of 20 lbs. Molecular sieve/silica gel traps were used to remove water and impurities from the carrier gas. 

The mass spectrum of etodolac methyl ester was obtained using a Hewlett-Packard quadrupole mass spectrometer, operating in the GC-MS positive electron impact (EI+) mode [15,16]. The monitored ions were at m/z 154, 168,198, 213, 228, 272, and 301, and assignments for these are summarized in Table 6. 

Tandem MS was applied to characterization and differentiation of the connectivity of the 0283 radical cation (mlz = 120) generated by dissociative electron ionization (El) of the l,3,4,6-tetrapentalene-2,5-dione 39. The structural assignment of the radical cation C2S as the C-sulfide ethenedithione, SCCS2 40, was based on the results of ion-molecule reactions of 0283 with nitric oxide, acetonitrile, and methyl isocyanide. The collisional activation spectra of these ion-molecule reaction products recorded on a new type of hybrid tandem mass spectrometer of sectors-quadrupole-sectors configuration allowed the confirmation of the ascribed structure 40 (Scheme 1) <1999PCA3666>. 

In Situ Methylation and Py-MS The sample (standards of known concentration or the cells to be analyzed) and 5 uL of 0.1 M tetramethylammonium hydroxide (TMAH) is added to the Curie-point wire and dried in hot air. The resulting dimethyl-DPA-coated wire is introduced in a quadrupole ion trap equipped with microtube furnace pyrolyzer capabilities, using a 200-460 C temperature ramping program. Alternatively, a triple quadrupole mass spectrometer may be employed using a Curie-point pyrolysis inlet with a 70 eV El source. Figure 19.6 shows the pyrolysis mass spectra of B. anthracis with and without in situ methylation obtained after a brief 10 min sample preparation and analysis from a 2.2 x 10 CFU sample. 

Hendricker AD, Abbas-Hawks C, Basile F, Voorhees KJ, Hadfield TL. Rapid chemotaxonomy of pathogenic bacteria using in situ thermal hydrolysis and methylation as a sample preparation step coupled with a field-portable membrane-inlet quadrupole ion trap mass spectrometer. Int... 

In environmental analysis, there has been increasing use of TOF, quadrupole. ion-trap, and Fourier transform mass spectrometers in addition to desorption ionization methods such as MALDI. Detection and quantitative determination of such widely diverse contaminants as perfluoroorganics, polybromi-nated diphenyl ethers, pharmaceuticals, byproducts of water disinfection, pesticides, algal toxins, surfactants, methyl-t-butyl ether, arsenic, and various microorgan-i.sms are now carried out using mass spectrometric methods. Mass spectrometry is also used to determine compounds of interest in homeland security. ... 

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