Hans-Joachim Hübschmann: Handbook of GC-MS: fundamentals and applications, 3rd ed. | SpringerLinkThis makes it ideal for the analysis of the hundreds of relatively low molecular weight compounds found in environmental materials. In addition, functionalised compounds may require chemical modification derivatization , prior to analysis, to eliminate undesirable adsorption effects that would otherwise affect the quality of the data obtained. Samples are usually analyzed as organic solutions consequently materials of interest e. The sample solution is injected into the GC inlet where it is vaporized and swept onto a chromatographic column by the carrier gas usually helium. The sample flows through the column and the compounds comprising the mixture of interest are separated by virtue of their relative interaction with the coating of the column stationary phase and the carrier gas mobile phase. The latter part of the column passes through a heated transfer line and ends at the entrance to ion source Fig.
Comprehensive GCxGC System
Gas chromatography—mass spectrometry GC-MS is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. GC-MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, it can identify trace elements in materials that were previously thought to have disintegrated beyond identification. Like liquid chromatography—mass spectrometry , it allows analysis and detection even of tiny amounts of a substance. A nonspecific test merely indicates that any of several in a category of substances is present.
It is one of the most accurate tools for analyzing environmental samples. The GC works on the principle that a mixture will separate into individual substances when heated. The heated gases are carried through a column with an inert gas such as helium. As the separated substances emerge from the column opening, they flow into the MS. Mass spectrometry identifies compounds by the mass of the analyte molecule. Mass spectrometry is considered the only definitive analytical detector. Limitations and Concerns.
The ability to measure steroid hormone concentrations in blood and urine specimens is central to the diagnosis and proper treatment of adrenal diseases. The traditional approach has been to assay each steroid hormone, precursor, or metabolite using individual aliquots of serum, each with a separate immunoassay. For complex diseases, such as congenital adrenal hyperplasia and adrenocortical cancer, in which the assay of several steroids is essential for management, this approach is time consuming and costly, in addition to using large amounts of serum. The advent of commercial high-performance liquid chromatography instruments coupled to tandem mass spectrometers offers the potential for medium- to high-throughput profiling of serum steroids using small quantities of sample. Here, we review the physical principles of mass spectrometry, the instrumentation used for these techniques, the terminology used in this field and applications to steroid analysis.
In gas chromatography, septum bleed is often attributed to the inlet septum, but the vial cap septum can also be a source. Read on to learn how to identify vial cap septum bleed and also how to choose a GC septum that will reduce the problem. Restek Corporation, U.
fluid and electrolytes for dummies pdf