then be used to identify a marker or other substances in the sample one advantage of ion mobility spectrometry is that it can operate at atmospheric pressure in yet another embodiment a total ion current measuring device can be used to detect and characterize markers this device can be used when the probe has a surface chemistry that allows only a single type of marker to be bound when a single type of marker is bound on the probe the total current generated from the ionized marker reflects the nature of the marker the total ion current produced by the marker can then be compared to stored total ion current of known compounds characteristics of the marker can then be determined data generated by desorption and detection of markers can be analyzed with the use of a programmable digital computer the computer program generally contains a readable medium that stores codes certain code can be devoted to memory that includes the location of each feature on a probe the identity of the adsorbent at that feature and the elution conditions used to wash the adsorbent using this information the program can then identify the set of features on the probe defining certain selectivity characteristics e g types of adsorbent and eluants used the computer also contains code that receives as input data on the strength of the signal at various molecular masses received from a particular addressable location on the probe this data can indicate the number of markers detected optionally including the strength of the signal and the determined molecular mass for each marker detected data analysis can include the steps of determining signal strength e g height of peaks of a marker detected and removing.