Patent ID: 7728288

Claim:
A method of mass spectrometry using a mass spectrometer having a longitudinal axis, comprising the sequential steps of: (a) generating ions in an ion source; (b) extracting ions such that they travel along the longitudinal axis of the mass spectrometer in a forwards direction relative to the ion source; (c) causing the ions to enter and then to exit an intermediate ion store as the ions travel along the longitudinal axis in the forwards direction; (d) causing the ions to enter a reaction cell as they travel along the longitudinal axis in the forwards direction; (e) processing the ions within the reaction cell; (f) causing the processed ions to exit the reaction cell to travel back along the longitudinal axis in a backwards direction relative to the ion source; (g) causing the processed ions to enter the intermediate ion store once more as they travel along the longitudinal axis in the backwards direction; (h) causing one or more pulses of the processed ions to exit the intermediate ion store in an off-axis direction; (i) causing the one or more pulses of processed ions to enter a mass analyser; and (j) obtaining a mass spectrum of the one or more pulses of processed ions using the mass analyser.