Mass spectrometry

From LipidomicsWiki

Mass Spectrometry
Mass spectrometric analyses are performed with a triple quadrupole instrument [Finnigan– MAT (San Jose, CA) model TSQ 7000] equipped with a nanoelectrospray source operating at a typical flow rate of 20–50 nl/min. The electrospray capillary is positioned at a distance of 0.5–1 mm before the orifice of the heated transfer capillary which is maintained at 150°C. As indicated, the instrument is used either in the single-stage MS mode or in the tandem MS mode (product ion, precursor ion, or neutral loss scan). Before analysis by MS, the lipid extracts are centrifuged in a benchtop centrifuge for 5 min and then a 1–5 μl aliquot is transferred into the electrospray capillary. The spray is started by applying ± 400–700 V to the capillary for the detection of positive or negative ions, respectively. For each spectrum between 20 and 100 repetitive scans of 4-sec duration are averaged. All tandem MS experiments are performed with argon as collision gas at a nominal pressure of 2 mTorr. The instrument can be programmed to sequentially perform different scan modes with different parameter sets under computer control using ICL (instrument control language) procedures.