Electron impact mode

A simple cleanup procedure based on acidic protein precipitation and LLE with ethyl acetate was used for the determination of OXA, CLO, and DICL in bovine muscle. The detection was accomplished with particle-beam MS with negative-ion chemical ionization, which was found more sensitive than electron-impact mode. Deviation from the linearity of response was observed, which could be caused by the phenomenon of coeluting carrying analyte particles through the particle beam (60). 

The mass spectrum of silver sulfadiazine (Figure 4) was obtained with a Kratos MS 9/50 mass spectrometer in the electron impact mode with an ionizing energy of 70 eV and equipped with a direct inlet probe, probe temperature 250°C (15). 

GC mass spectrometry analysis in electron impact mode (GC/EIMS) ... 

Mass spectral data shall be obtained using a low resolution instrument that utilizes 70 volts (nominal) electron energy in the electron impact mode. The system shall he capable of selected ion monitoring (SIM) for at least 18 ions per cycle, with a cycle time of 1 second or less. Minimum integration time for SIM is 25 milliseconds per m/z. The integration time used to analyze... 

Detection SIM in electronic impact mode with an energy of 70 eV. 

Gas Chromatooraphy-Mass Spectrometry. A Finnigan MAT 4500 GC/MS/INCOS system (Finnigan MAT, San Jose, CA) was used for analysis. A 60 m X 0.32 mm i.d. DB-WAX coiumn was empioyed for the headspace samples. The oven temperature wa programmed from 50 C to 180°C at 2 C/min. A 60 m X 0.32 mm i.d. DB-1 column was used for the sample prepared by vacuum SDE. The oven temperature was programmed from 30 °C (4 min isothermal) to 210 C at 2 C/mln. HeHum was used as the carrier gas at a flow rate of 3.2 mL/min. The column outlet was Inserted directly into the ion source block. The instnjment was operated in the electron impact mode at an ionization voltage of 70 eV. The mass spectrometer was repetitively scanned from 33 to 350 m/z in a one-second cycle. 

HRGC-ECD has been used in some studies for PCDE analysis [115,117,126, 129],but GC-MS has been the most often used method in analysis of PCDEs [33, 43, 57, 58, 113, 114, 116, 118-126, 128, 130-133, 139]. Analysis of PCDEs has mostly been performed in selected ion monitoring mode (SIM) [33,57,58,113, 114,119,120,122-125,130,132,139], but full scan mode has also been used in some studies [121,126,131]. MS instruments are usually operated in electron impact mode (El). El mass spectra of most PCDEs have an abundant molecular ion M + and one abundant fragmention (M +-2Cl). The fragmention (M +-70), which is the same as the molecular ion of PCDFs, is more abundant than the molecular ion, but the latter has mostly been used in SIM analyses of PCDEs. Table 8 presents masses of molecular ions of PCDEs. 

The low resolution mass spectrum of diltiazem HCI shown in Figure 7 was obtained using a Finnigan 4500 mass spectrometer operated at 70 eV in the direct probe electron impact mode (15). The molecular ion of the free base is seen at m/z = 414 and the protonated free base ion is observed at m/z = 415. The fragmentation pattern (Figure 8) is consistent with the chemical struture. 

Figure 8. Mass spectrum of indapamide in the electron impact mode.

LPS samples (0.5 mg) were hydrolyzed with 2 mol l-1 TFA at 100 °C for 18 h followed by reduction in dH20 with NaBH4 and subsequent acetylation with acetic acid/pyridine (1 1, v/v) at 100 °C for 1 h. The resultant alditol acetates were extracted thrice with dichloromethane, the combined organic layer concentrated to dryness and analyzed by GLC using a Hewlett-Packard chromatograph equipped with a 30 m DB-17 capillary column (190 °C (32 min), 16 °C min-1 to 270 °C (32 min)) and by GLC-MS in the electron impact mode (El) recorded using a Varian Saturn 2000 mass spectrometer. For compositional analysis of acid-labile deoxy... 

Gas chromatography-mass spectrometry (GC-MS) was carried out on selected samples either to confirm compounds Identified by retention times or to Investigate the Identities of other peaks of Interest. Samples were run on a Finnigan Model 9610 GC coupled to a Finnigan Model 4021 quadrupole MS. Mass spectrometrlc data were acquired and processed with a Flnnlgan-INCOS 2300 Data System. The MS was operated In electron Impact mode with 70 eV electron energy. Gas chromatographic conditions were comparable to those used for GC-FID. 

The extracts are analysed using a Finnigm 9610 gas chromatograph interfaced to a Finnigan 4023 quadropole mass spectrometer and a Super Incos, NOVA 4xdata system with a 70 MB disc drive. Mass spectra is recorded with 1 scan per 0,6 sec in full scan mode (35-400 amu). The mass spectrometer is operated in the electron impact mode at 70e V. The analysis is performed using a 30m DB-5 fused silica capillary colunm with 0,25 pm film thickness (J W Scientific, Inc.). The iigector temperature is kept at 270°C, the interface oven at 250°C and the ion source at 270°C. The oven is initially held at 30°C for 5 mm and increased 4°C per minute to 300°C and kept there for 10 minutes. 

Gas Chromatography-Mass Spectrometry. A VG Trio-2 mass spectrometer was directly coupled with the Hewlett-Packard 589 R gas chromatograph, equipped with a 30 m x 0.32 mm DB-WAX capillary column (J and W. Scientific bonded polyethylene glycol phase). The carrier gas was He at 2.3 ml/min. The injector and transfer temperature was programmed as follows 30 C (2 min isothermal), to 38°C at l°C/min, then to 180°C at 2°C/min. The instrument was operated in the electron-impact mode at an ionization voltage of 70eV. Quantitative analysis by peak area, plots of chromatograms, and library search results were obtained. 

The GC-MS analyses were performed on similar glass capillary columns in a Shimazdu Model GC-4CM GC connected to a Finnegan 1015 mass spectrometer equipped with a Systems Industries data system with Riber 400 D-8 software. The mass spectrometer was operated in the El (electron impact) mode at 70 eV. 

Detector MS, Finnigan 4023, particle beam interface (Vestec universal interface model 700), electron impact mode 77 eV, scan m/z 200-350 (positive ion), multiplier voltage 1200 V, source 300° UV 365... 

Both electron impact mode (El) and positive ion chemical ionization mode (PlCl) has been used for the detection of organophosphorus i5,36,io4,ios of PlCl, methane has been utilized as... 

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