The mass spectrum was then taken over a 0.10 minute time range at the highest intensity range of the resulting peak and the background from the front of this broad peak was subtracted to clean up the mass spectrum. The resulting mass spectrum was recorded. The total ion chromatogram for a 30 ng sample of cocaine is shown in Figure 3 - top. This chromatogram consists of several peaks or humps which are probably due to one or more impurity components in the drug sample. The resulting extracted ion chromatogram shows the area of the total chromatogram which would contain the highest concentration of cocaine.
Ballistic heating provides for the fastest sample analysis and the bet sensitivity of analysis.
However, it is often desirable to heat the probe up more slowly. This slower temperature programming technique can remove unwanted solvents or permit the thermal separation of mixtures of analytes in a sample. The slower heating of the probe will increase the time of analysis and cause the analytes to be eluted later in the total ion chromatograph, but it will also result in a decrease in sensitivity of the direct probe technique. This is demonstrated in Figure 4 in which 30 nanograms of cocaine was analyzed via the two methods. The programmed heating of the probe at 100 degrees per minute resulted in a three minute analysis with a peak half width of about 0.5 minutes for the cocaine.