Image Charge Detection Mass Spectrometry: Pushing the Envelope with Sensitivity and Accuracy

摘要

ABSTRACT: A novel image charge detection mass spectrometer (CDMS) with improvednsensitivity andmass accuracy is described. The improved detector design andmethod of datananalysis allow us tomeasure a reliablemass for a singlemacroion that is an order ofmagnitudensmaller than previously achieved with CDMS. The apparatus employs an image chargendetector array consisting of 22 detectors. The detectors are divided into two groups that cannbe floated at different potentials. The signals from the detector array are analyzed using a correlation approach to yield the velocitiesnin the two groups of detectors and the charge. These quantities, together with the voltage difference between the two groups ofndetectors, provide a value for the mass. The mass, m/z, and charge distributions recorded for 300 kDa poly(ethylene oxide) (PEG)nare presented. The mass distribution shows a peak at around 300 kDa with a width close to that expected from the polymer sizendistribution. In addition, there are broad peaks in the mass distribution at around 100 and 500 MDa. The 300 kDa ions have m/znratios of∼2 kDa/e, and the 100 and 500MDa ions have m/z ratios of∼40 kDa/e. The 100 and 500MDa ions probably result fromnPEG aggregates that are either present in solution or the residue of large electrospray droplets.