Analyst Software Reference Guide - AB Sciex

Software Reference GuideIn looped experiments, MS settings are changed on a scan-by-scan basis. For example, if thesample contains two compounds, A and B, you may want to loop an MS/MS experiment ofcompound A with an MS/MS experiment of compound B to obtain information on bothcompounds in the same run. The mass spectrometer method will alternate between the twoscans. Other examples of looped experiments include alternating between positive and negativemode in a run and IDA methods.PeriodsA period can contain one or more looped experiments. In a multi-period acquisition method,experiments are performed for a specified amount of time and then switch to another set ofexperiments. Periods are useful when you know the elution time of the compounds in an LC run.You can have the mass spectrometer perform different experiments according to when thecompounds elute to get as much information as possible in the same run.In Figure 1-2, a three-period method is shown. The first period has a duration of 3.015 minutes;the second period is 4.986 minutes; and the third period is 7.000 minutes.Figure 1-2 Example of a multi-period experimentFlow Injection Analysis (FIA)FIA is the injection of a small quantity of a sample by an autosampler into the LC stream. Duringthe FIA optimization process, multiple sample injections are performed for various source- orcompound-dependent, or both, parameter types that are changed between injections. FIAoptimizes for declustering potential, collision energy, and collision cell exit potential by performinglooped experiments in succession, that is, one compound-dependent parameter followed by thennext compound-dependent parameter. It optimizes for source-dependant parameters by makingan injection for each parameter.Use FIA optimization to optimize both compound- and source-dependent parameters using LC athigher flow rates. See also Infusion on page 19.Release Date: August 2011 17