The red squares in Figure 7 indicate the results of experiments where the two different probe sequences of the same length were mixed, i.e. although their TNT labels were different isotopes of each other, the complete TNT-PNA probes were not isotopes of each other. The red line represents a linear regression through these data points. Although the predicted and expected ratios do not match exactly, there is a good correlation between the results indicating that the measurements are quantitative. Since the TNT-PNA probes were actually different in these experiments, it is pleasing to see that there is correlation between the measured and expected quantities and the result suggests that, in future use, the measurements of the quantity of different targets in a sample could be calibrated against an internal control such as a housekeeping gene or, preferably, a known quantity of a spiked target sequence.