****************************************************************************** Date: Wed, 22 Nov 95 10:23:27 -0500 From: Chip Cody Orig-To: pocasip@ix.netcom.com (David Mintzer ) Subject: Re: Calibration >I wonder what kind of effort is necessary to really tune the MS for >calibration. >David Mintzer >dmintzer@ix.netcom.com ------------------ You probably will need to be more specific about what kind of calibration you have in mind. There are several things that can be calibrated: 1. Mass assignment. All mass spectrometers need to be calibrated to specify how masses are assigned to peaks. This is (almost) always done by constructing a calibration curve based upon the mass spectrum of a known reference standard. 2. Peak heights. Quadrupole mass spectrometers require calibration to achieve a standardized abundance-versus-mass response. This is done by tuning peak heights for a standard sample such as DFTPP. Peak heights can be influenced by other factors in other types of analyzers, but the quadrupole case is the best example. 3. Quantitation. Quantitative methods such as SIM require the creation of a calibration curve based on the response of varying quantities of a standard sample. SIM or SRM methods usually also require some calibration of the mass spectrometer so that the masses or reactions will be accurately monitored. 4. Peak shape and ion source tuning. The mass spectrometer parameters (ion source voltages, lens potentials, and also excitation and detection conditions in trapped-ion methods) all have to be adjusted to give good sensitivity and good peak shapes for a standard reference compound at some specified resolution value. All of these functions are, or can be, handled automatically by the mass spectrometer data systems. The specific algorithms depend on the type of analyzer and the manufacturer. I'm sure that everyone would be interested in any new techniques that could be brought up for discussion. Chip Cody JEOL USA, Inc.