Environmental Solutions

Shimadzu Liquid Chromatography Mass Spectrometry (LCMS)

Recent advances in LC detection have added mass spectrometers and, even more recent, tandem mass spectrometers. These new detectors enable very fast, selective LC runs for polar pesticides and herbicides, cyanotoxins by EPA method 544, perfluorinated compounds by EPA method 537, ASTM D7979 or D7968, and pharmaceutical and personal care products by SM 6810. You can expect that the newer environmental methods will be LC-MS/MS.

Unlike gas chromatography, which is limited to volatile compounds, or those that can be extracted into an organic solvent and vaporized in a GC, an LC-MS/MS can analyze just about anything that happens to be dissolved in your sample. It is especially useful for those compounds that are difficult to analyze by GC methods, such as halo acetic acids, 2, 4-D and 2, 4, 5 -TP. It can take away the necessity of post-column derivatization and analyze carbamates. Better yet, it can do all of this in a single sample run with little or no sample preparation and in very short times.

As we described in the GC-MS/MS portion, a compound is ionized and passes through one quadrupole that selects one mass. Then that mass enters a collision cell where it is fragmented into other highly reproducible compounds of different mass. Another quadrupole selectively allows single mass ions to pass through and measures them on a detector.

MRM process in an LCMS

The liquid chromatograph (LC) separates the components of a sample based on differences in their affinity for the stationary phase or mobile phase. Mass spectrometry (MS) offers a highly sensitive detection technique that ionizes the sample components, then separates the resulting ions based on their mass-to-charge ratios and measures the intensity of each ion. Therefore, LC-MS systems combine the separation resolution of liquid chromatography with the qualitative capabilities of mass spectrometry. The mass spectra obtained from these scan measurements provides molecular mass and structural information for eluted components, which supplements the qualitative information based on retention times obtained using other LC detectors.

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