Flame ions sources

The maximum column temperatures used in GC/MS are usually 25-50° lower than those used in capillary GC with a flame ionization detector. Higher temperatures can be used in GC/MS but there will be more column bleed, which will require more frequent cleaning of the ion source of the mass spectrometer. 

Morristown, NJ) for the ion source. No carrier gas separator was used. For determination of nitrosamines and TBDMS derivatives of hydroxy-nitrosamines, columns and operating conditions were identical to those for GC-TEA analyses For most work, the He flow rate was 15 cc/min and the column effluent was split 1 1 between a flame ionization detector and the mass spectrometer. The stainless steel splitter, solvent vent valve (Carle Instruments, Fullerton, CA), and associated plumbing were... 

Direct pyrolysis in the ion source of a mass spectrometer (QMS) was used to analyse PE/(dicumylperoxide, Santonox R) and PVC/DIOP [259]. In-source PyMS is an analytical tool for fast analysis of flame retardants in unknown mixtures of polymers [223, 265], Heeren and Boon [224] used in-source filament pyrolysis FTMS for high-speed, broadband screening of additives in polymeric household appliances. 

Mass Spectrometry. The use of a quadrupole mass spectrometer as a GC detector for nonmethane hydrocarbon analysis has come of age in recent years. Development of capillary columns with low carrier gas flows has greatly facilitated the interfacing of the GC and mass spectrometer (MS). The entire capillary column effluent can be dumped directly into the MS ion source to maximize system sensitivity. GC-MS detection limits are compound-specific but in most cases are similar to those of the flame ionization detector. Quantitation with a mass spectrometer as detector requires individual species calibration curves. However, the NMOC response pattern as represented by a GC-MS total ion chromatogram is usually very similar to the equivalent FID chromatogram. Consequently, the MS detector can... 

Mass spectrometry and flame ionisation can be placed under the category ionisation methods. In mass spectrometry a substance is made to form ions and then the ions are sorted by mass in electric or magnetic fields. Positive ions are produced in the ion source by electron bombardment or an electric discharge. 

Fig. 7. The variation of product cross sections with translational energy in the laboratory flame (upper scale) and the center-of-mass flame (lower scale) for the reaction of Ar with Sip4. Closed symbols represent data taken with Ar generated in the El ion source (statistical distribution of spin-orbit states) and open symbols show data for the FT ion source (largely Th dashed line shows...

A total ion monitor (TIM), though not part of the interface, is often useful for the GC MS operation. The TIM is an ion detector positioned in the analyzer tube between the ion source and the magnet and is adjustable to collect a certain percentage of the total ions formed. This detector response is registered on a dual pen strip chart recorder with that of the GG flame detector (Figure 6). There may be some difiFerences in peak ratios because of differences in detector responses to the various compounds the mass spectra are taken at the TIM peak maxima since the ions are then most concentrated. Pesticide residue analysis by GG MS... 

Quantitative response in IMS is today acceptable in applications where IMS has been successful yet unacceptable compared to other detector technologies, such as flame ionization detectors or MSs. This is limited by kinetics of ion formation at the low end of response and by ion source saturation at the top end of the response curve and by matrix effects. Other technologies, such as electron capture detectors and the ion trap MS, shared a similar history and were engineered free of the limitations. There is no such advancement under way today in IMS. 

Examination of flame-retarding additives was done by Heeren et al. using a direct temperature controlled pyrolysis external ion source and a 7 T FTICR. Samples were taken from common household appliances such as TV set housings, computer casings, and others and were pulverized to powder form. Direct heating of the filament probe with dried sample produced spectra with two distinct regions, corresponding to evaporation of nonbonded additives and pyrolysis of the polymer matrix. The xmknown polymer blends were foxmd to contain brominated biphenyls, brominated diphenyl ethers, tetrabromoBisphenol-A and its butylated isomers, polystyrene, and antimony oxides. 

The detectors used in HTGC are, apart from the highly versatile flame ionization detector (FID), the phosphorus/nitrogen-selective alkali-flame ionization detector (AFID), the atomic emission detector, the inductively coupled plasma (ICP)-mass spectrometer, and, last but not least, mass spectrometers with electron impact and chemical ionization ion sources (EI/CI-MS). 

Originally, studies of ionization in flames were motivated by the observation that in hydrocarbon flames, the ion concentration far exceeds the value expected if ionization were due to thermal processes alone (see Table I). The objectives of these studies were to explain the source of nonequilibrium ionization and to explore links between flame ionization and the mechanism of flame propagation. An explanation of the source of flame ions was found in the process of chemi-ionization. This led to further studies of the details of ionic reactions which occur in flames and of flame reactions which can be induced by the addition of foreign elements. 

A 333-fold improvement in the detection limit was achieved by the use of the SI ion source. Estimated from recovery study, the relative standard deviation (RSD) of peak area of TMA was 6.8% at a concentration of 225 pg/L. The method offers a few advantages over the flame ionization detector, which is commonly used. Because no preconcentration is needed, the analysis time can be less than 10 minutes, which is much shorter than a GC method including a preconcentration procedure. A second advantage is a high degree of specificity due to the characteristics of SI. Therefore, the method may be useful in routine analysis for a large number of air samples. 

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