The Core MS Facility offers the following expertise:
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High Throughput Quantitative Mass Spectrometry
Rapid methods for quantitative analysis by mass spectrometry rely primarily on robust chromatographic procedures followed by mass selective detection. The Core MS facility can perform simple liquid chromatography coupled to mass spectrometry (LC-MS) experiments wherein the analyte of interest and its internal or external standard are monitored and measured using diagnostic ion(s) to each compound. This technology is often referred to as selected ion monitoring (SIM) or selected ion recording (SIR). In many cases this simple approach may be compromised by interference from other compounds that either co-elute or have mass to charge ratios monoisotopically similar to the compound of interest. In such cases greater specificity can be achieved by performing fragmentation on selected ions and monitoring the transition of the selected ion fragmenting to a diagnostic product ion. When this is coupled to LC it is often referred to as LC-MS-MS. In both cases analytical runtimes are typically in the order of less than 10 minutes per sample and can accommodate large batches of samples to achieve quantitative analysis using daily calibration curves, quality control samples and unknowns. Experts in quantitative mass spectrometry are available to help you design, develop and validate such studies.
Triple Quadrupole Mass Spectrometry
Mass spectrometers are often identified by the type of mass analyzer employed in the selective transmission of ions within the instrument. In the case of the triple quadrupole mass spectrometer the mass analyzer is composed of three quadrupole mass filters that focus ions based on their mass to charge ratio. By varying the radio frequency to DC voltage applied to two pairs of parallel metal rods the ions either travel in harmony with the Rf/DC ratio and arrive at the detector or they collide with the rods. By scanning the Rf/DC ratio we eventually transmit all ions. In the triple quadrupole instrument we can simply use just the first quadrupole mass filter and detect ions or we can allow the ions to enter the second mass filter and cause the transmitted ions to fragment as they collide with a solid surface or with an inert motionless gas. In the latter case the collision induced fragmentation can be used to generate product ions which can then be further analyzed in the third quadrupole mass filter. If we operate the third filter in a full scanning manner we will obtain the product ion spectra from any given precursor ion that was transmitted through the first quadrupole and fragmented by CID in the second quadrupole mass filter and often referred to as the collision cell. Such experiments are very important in the elucidation of fragmentation pathways and identifying the precursor ion from which a fragment arises. The advent of triple quadrupole mass spectrometers has been such that they are often viewed as the instruments most amenable to high throughput, high sensitivity quantitative mass spectrometry. They have limited ability in protein analysis and further limitation in use as accurate mass measurement devices limited really to unit mass resolution. The Core MS facility has three LC-MS-MS instruments.
Information to be added soon.