Tandem capillary columns

The combination of chromatography and mass spectrometry (MS) is a subject that has attracted much interest over the last forty years or so. The combination of gas chromatography (GC) with mass spectrometry (GC-MS) was first reported in 1958 and made available commercially in 1967. Since then, it has become increasingly utilized and is probably the most widely used hyphenated or tandem technique, as such combinations are often known. The acceptance of GC-MS as a routine technique has in no small part been due to the fact that interfaces have been available for both packed and capillary columns which allow the vast majority of compounds amenable to separation by gas chromatography to be transferred efficiently to the mass spectrometer. Compounds amenable to analysis by GC need to be both volatile, at the temperatures used to achieve separation, and thermally stable, i.e. the same requirements needed to produce mass spectra from an analyte using either electron (El) or chemical ionization (Cl) (see Chapter 3). In simple terms, therefore, virtually all compounds that pass through a GC column can be ionized and the full analytical capabilities of the mass spectrometer utilized. 

The use of SPE with porous materials such as alumina, diatomaceous earth, Horisil and silica for the cleanup of fat-soluble organochlorine pesticides in fatty foods such as meat, flsh, shellfish, milk and vegetable oils has been well documented. The choice of elution solvents is critical because relatively small amounts of lipid in the final extract can cause rapid deterioration of GC capillary columns and also contaminate the gas chromatograph. A number of workers have used a porous material in tandem with Cig to effect an improved cleanup.Di Mucchio employed a multicartridge system comprising Extrelut, silica and Cig to extract organophosphorus pesticides from oils and fatty extracts. Relatively few literature applications include the pyrethroids, but Ramesh and Balasubramanian reported a simple carbon-based SPE method for the analysis of pyrethroids in vegetable oil. 

Figure 2.7 Activity test of an uncoated fused silica capillary after deactivation with poly(phenyliaethylhydrosiloxane), (A), and before deactivation, (B). Precolunn 15 x 0.20 m I.D. coated with SE-54. Test columns 10 a x 0.20 I.D. The column tandem was programmed from 40 to I80 c at a C/min after a 1 min isothermal hold with a hydrogen carrier gas velocity of 50 cm/s. The test mixture contained 10 n-decane, Cg-NH = l-aminooctane, PY 3,5-dimethylpyrimidine, C 2 n-dodecane, - 1-amlnodecane, DMA ...

Spikmans, V., Lane, S. J., Tjaden, U. R., and van der Greef, J., Automated capillary electrochromatography tandem mass spectrometry using mixed mode reversed phase ion-exchange chromatography columns, Rapid. Com-mun. Mass Spectrom., 13, 141, 1999. 

The analysis of estrogens and progestogens by GC-MS has been carried out with a variety of capillary columns using helium as carrier gas [7,26,36,43, 59, 66]. LODs in the range of 0.1—1.8 ng L 1 have been achieved. In terms of sensitivity, GC- and HPLC-tandem mass spectrometry are comparable techniques. However, the derivatization carried out prior to GC separation is time consuming and can be a source of inaccuracy [7]. 

Munch JW, Bassett MV (2004) EPA Method 521. Determination of nitrosamines in drinking water by sohd-phase extraction and capillary column gas chromatography with large volume injection and chemical ionization tandem mass spectrometry (MS/MS), U.S. EPA, Cincinnati, OH. Available at www.epa.gov/nerlcwww/m 521.pdf... 

SFC chromatographs represent hybrids between GC and HPLC instruments (Fig. 6.4). In order to deliver the supercritical fluid, syringe pumps or reciprocal pumps are used and maintained above the critical temperature using a cryostat regulated at around 0 "C. In instances where an organic modifier is used, a tandem pump is employed which has two chambers, one for the critical fluid and one for the modifier. The liquid then passes through a coil maintained above the critical temperature so that it is converted into a supercritical fluid. Stainless steel packed columns like those used in HPLC (1 to 4 mm in diameter) or fused silica capillary columns like those used in capillary GC (2 to 20 m in length, internal diameters as low as 50 pm and stationary phase film thickness of at least 1 pm) are used in SFC. 

Kalinoski et al. [32] has applied this method to the determination of tri-chothecene mycotoxins in wheat. The methods were based on chemical ionisation MS and collision-induced dissociation tandem MS and enabled the rapid identification of ppm levels of several trichothecene mycotoxins. Supercritical carbon dioxide is shown to allow identification of mycotoxins with minimum sample handling in complex natural matrices such as wheat. Tandem MS techniques are employed for unambiguous identification of compounds of varying polarity, and false positives from isobaric compounds are avoided. Capillary column SCFC-MS of a SCF extract of the same sample was also performed, and detection limits in the ppb range appear feasible. 

A coaxial CF-FAB interface was applied to the coupling of CE with tandem MS. A pair of coaxial fused silica capillary columns were used to deliver, independently, the microcolumn effluent and the FAB matrix directly to the FAB probe tip face. The advantages of the system are that the composition and flow rates of the two liquid streams can be independently optimized, the FAB matrix does not affect the microcolumn separation process, and peak broadening is minimized because the two streams do not mix until they reach the tip of the FAB probe, where ion desorption occurs. 

The First Tandem Capillary Column Mass Spectrometer System... 

The study of protein structure, function, quantity, and interactions during maturation and progression of disease is referred to as proteomics. Analytical approaches that use a combination of two-dimensional (2-D) gel electrophoresis for protein separation and MS analysis for protein identification followed by database searches is a widely practiced proteomics strategy.The tryptic peptides extracted from gels are analyzed by MALDI-TOF MS and microcolunm or capillary LC tandem mass spectrometry (MS/MS) techniques. Typically, the MALDI-TOF MS techniques are used to quickly identify peptide fragments and confirm the presence of known proteins. Nano-scale capillary LC/MS/MS techniques (using 50-100 pm diameter columns, operating at flow rates of 20-500 nL/min) are... 

Both packed and capillary columns are used with the SFE-GC tandem. The detector is usually of the mass spectrometry, flame ionization or electron capture type. The most suitable interface for each application will be that allowing the extractant to be removed prior to the column — and hence to the detector. 

The thiophosphamide ester derivatives 79 (Section III.B.l) obtained from samples spiked with standard aromatic amines and 3-phenyl-1-propylamine as internal standard were separated and determined by GC-FPD, using two capillary columns in tandem and a 526 nm filter in the optical path. The LOD (SNR 3) for aniline (la), 2-toluidine (lb), 3-toluidine (lc), 3-ethylaniline (If), 4-ethylaniline (lg), 2,3-xylidine (2a), 2,4-xylidine (2b) and 2,6-xylidine (2d) were 50, 100, 40, 30, 30, 50, 50 and 100 pg, respectively. This method was applied for analysis of smoke collected in the laboratory by burning materials as varied as chicken meat, sausage, sardine, dried squid, bread, black pepper, soy sauce, wood chips, rubber and cigarettes (main-stream and side-stream smoke). All smokes showed the presence of ppm concentrations of the eight standard aromatic amines mentioned above, but none contained detectable concentrations of all of them169. 

D Agostino PA and Provost LR (1995). Analysis of irritants by capillary column gas chromatography tandem mass spectrometry. J Chromatogr Anal, 695, 65-73. 

Dual columns — The introduction of capillary columns brought about a revolution in the level of resolution, and these columns are now almost universally used. Nonetheless, no single column is able, for example, to resolve all of the 209 PCB congeners so that the application of two columns in tandem with separate ovens and detector systems has been advocated. Fraction cuts from one column are quantitiatively transferred to the other (Duinker et al. 1988). A few examples are given as illustration. 

Although a large variety of stationary phases has been used in the literature, only multidimensional GC, a powerful two-column technique, allows complete separation of all 209 PCB congeners.In this technique two capillary columns are arranged in series, and congeners, coeluted from the first column, are transferred to a second column with a different selectivity. Pressure or valve control at the midpoint of a tandem-column system can be switched to cause effluent from the precolumn to travel to a monitor detector or to the analytical column and its detector. 

EDCs in the environment are often analyzed using GC or LC based instrumental techniques. GC coupled with an electron capture detector (BCD), a nitrogen-phosphorus detector (NPD), or mass spectrometry (MS) has been the preferred method due to its excellent sensitivity and separation capability on a capillary column. High performance liquid chromatography (HPLC) with various detectors such as ultraviolet detection (UV), fluorescence detection (FLD), MS, and more recently tandem MS (MS/MS) has also been used for analysis of some EDCs, especially for the polar compounds. Analytical techniques for each class of EDCs will be discussed in the following section. 

Munch, J.W. Revision 1.0, Sept. 2004, NERL Method 521 Determination of Nitrosamines in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography with Large Volume Injection and Chemical Ionization Tandem Mass Spectrometry (MS/MS). 

Capillary column GC-MS/MS offers the analyst the potential for highly specific, sensitive detection of chemical warfare agents as this technique significantly reduces the chemical noise associated with complex biological or environmental sample extracts. The specificity of product scanning with moderate sector resolution, as well as the specificity of ammonia Cl, was demonstrated with a hybrid tandem mass spectrometer during analysis of painted panel samples circulated during an international round robin verification exercise. 

D Agostino, P.A., et al. (1990) Capillary column gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry detection of chemical warfare agents in a complex airborne matrix. Journal of Chromatography A, 504, 259-268. 

Capillary column GC/MS and GC/MS/MS analyses were performed with GCQ-Tandem mass detector (Finnigan MAT). A 15 m x 0,25 mm... 

Capillary column GC/MS and GC/MS/MS under El conditions with GCQ Tandem system was used to detea and identify some organophosphorus CW agents, CR, sulphur containing CW and related compound. 

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