Atmospheric pressure coupling

Low-pressure ICPs and MIPS, often used as ion sources (see, e.g.. Creed et al. [779]), are also very similar to glow discharges in their performance, except for them being electrodeless discharges. They have shown particular merits for element-specific detection in chromatography, where detection limits down to the pg/s level can be obtained. These values, however, were found to be surpassed for halogens by microwave discharges at atmospheric pressure coupled with TOF-MS. 

There are other characteristics of quadrupoles that make them cheaper for attainment of certain objectives. For example, quadrupoles can easily scan a mass spectrum extremely quickly and are useful for following fast reactions. Moreover, the quadrupole does not operate at the high voltages used for magnetic sector instruments, so coupling to atmospheric-pressure inlet systems becomes that much easier because electrical arcing is much less of a problem. 

Samples containing mixtures of peptides can be analyzed directly by electrospray. Alternatively, the peptides can be separated and analyzed by LC/MS coupling techniques such as electrospray or atmospheric pressure chemical ionization (APCI). 

The part that marries the plasma to the mass spectrometer in ICPMS is the interfacial region. This is where the 6000° C argon plasma couples to the mass spectrometer. The interface must transport ions from the atmospheric pressure of the plasma to the 10 bar pressures within the mass spectrometer. This is accomplished using an expansion chamber with an intermediate pressure. The expansion chamber consists of two cones, a sample cone upon which the plasma flame impinges and a skimmer cone. The region between these is continuously pumped. 

I. Eeirer, M. C. Hennion and D. Barcelo, Immunosorbents coupled on-line with liquid chi omatography/atmospheric pressure chemical ionization/mass specti ometiy for the part per trillion level determination of pesticides in sediments and natural waters using low preconcenti ation volumes . Anal. Chem. 69 4508-4514 (1997). 

As with GC, the combination of MS and MS/MS detection with LC adds an important confirmatory dimension to the analysis. Thermospray (TSP) and particle beam (PB) were two of the earlier interfaces for coupling LC and MS, but insufficient fragmentation resulted in a lack of structural information when using TSP, and insufficient sensitivity and an inability to ionize nonvolatile sample components hampered applications using PB. Today, atmospheric pressure ionization (API) dominates the LC/MS field for many environmental applications. The three major variants of API... 

Specifically for triazines in water, multi-residue methods incorporating SPE and LC/MS/MS will soon be available that are capable of measuring numerous parent compounds and all their relevant degradates (including the hydroxytriazines) in one analysis. Continued increases in liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API-MS/MS) sensitivity will lead to methods requiring no aqueous sample preparation at all, and portions of water samples will be injected directly into the LC column. The use of SPE and GC or LC coupled with MS and MS/MS systems will also be applied routinely to the analysis of more complex sample matrices such as soil and crop and animal tissues. However, the analyte(s) must first be removed from the sample matrix, and additional research is needed to develop more efficient extraction procedures. Increased selectivity during extraction also simplifies the sample purification requirements prior to injection. Certainly, miniaturization of all aspects of the analysis (sample extraction, purification, and instrumentation) will continue, and some of this may involve SEE, subcritical and microwave extraction, sonication, others or even combinations of these techniques for the initial isolation of the analyte(s) from the bulk of the sample matrix. 

Reversed-phase high-performance liquid chromatography (HPLC) column 50 mm x 3.2-mm i.d. with Kromasil 5- um Gig packing High-performance liquid chromatograph coupled to a triple-quadrupole mass spectrometer with an atmospheric pressure chemical ionization (APCI) source Gel permeation chromatograph with a 60 mm x 25-mm i.d. column packed with Bio-Beads SX-3 (50-g)... 

Equations, determine sequences of simple and complex columns that minimize the overall vapor load. The recoveries will be assumed to be 100%. Assume the actual to minimum reflux ratio to be 1.1 and all the columns, with the exception of thermal coupling and prefractionator links, are fed with saturated liquid. Neglect pressure drop through columns. Relative volatilities can be calculated from the Peng-Robinson Equation of State with interaction parameters set to zero. Pressures are allowed to vary through the sequence with relative volatilities recalculated on the basis of the feed composition for each column. Pressures of each column are allowed to vary to a minimum such that the bubble point of the overhead product is 10°C above the cooling water return temperature of 35°C (i.e. 45°C) or a minimum of atmospheric pressure. 

W.E. Neff, W.C. Byrdwell, Characterization of model triacylglycerol (triolein, trilinolein and trilinolenin) autoxidation products via high performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry, Journal of Chromatography A, 818, 169 186 (1998). 

In the palladium-catalyzed coupling reactions of arenes with alkenes, the cr-arylpalladium complexes react with CO to give aromatic acids in AcOH, as shown in Scheme u 97>97a 97c This carboxylation reaction of arenes with CO proceeds catalytically with respect to Pd at room temperature under atmospheric pressure of CO, when K2S2O8 is added as an oxidant and TFA is employed as a solvent. 

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