Patent ID: 7518103

Claim:
A pulsed flow modulation gas chromatography mass spectrometry with supersonic molecular beams method for improved sample analysis, comprising the steps of: injecting a sample into a gas chromatograph; separating said sample compounds in the gas chromatograph by a first analytical column; eluting the sample from said first analytical column into a storage transfer column; passing a first gas pulse, of a relatively high flow rate carrier gas, through a gas line into a gas line connector also connecting the first analytical column and said storage transfer column; forming an increased pressure at the gas line connector by said high flow rate carrier gas pulse, to temporarily stop sample elution from said first analytical column; transferring the sample compounds in the storage transfer column with said high flow rate carrier gas pulse, into a second analytical column of a different polarity than the polarity of said first analytical column; providing a second gas pulse of intermediate carrier gas flow rate, of a duration longer than the duration of said first gas pulse for the separation in time of the sample compounds in said second analytical column; adjusting the time of said first gas pulse, second gas pulse and the ratio of second analytical column flow rate to first analytical column flow rate, to provide second analytical column chromatographic peak widths that are sufficiently broad to enable compatibility with a scanning speed of a mass spectrometer; adding makeup gas to the output gas flow of the second analytical column; reducing the flow rate of said added makeup gas to compensate for the increased second column flow rate; transferring said sample compounds via a heated transfer line into a supersonic nozzle; expanding said sample and combined second column and added make up gases from said supersonic nozzle for the formation of vibrationally cold sample compounds in a supersonic molecular beam; ionizing said sample compounds by electrons in a fly through ion source while they are contained in said supersonic molecular beam; analyzing the ions formed from said sample compounds in said supersonic molecular beam in a mass analyzer of a mass spectrometer; detecting said ions of said sample compounds after their mass analysis with an ion detector; processing the data obtained from the mass spectrometer after ion detection for identifying and/or quantifying the chemical content of said sample, and repeating the cycle of said first pulse of relatively high flow rate followed by said longer, second pulse of intermediate flow rate, in a repetitive fashion.