Implementation of an incubation step. (a) In the positive mode, the signal detected without an incubation step was 1.23E5. (b) This signal was remarkably increased to 6.18E5 with an additional 4 peaks detected amid the incorporation of an incubation step. (c) In the negative mode, the signal detected without the incubation step was 1.17E4. (d) This signal was enhanced to 2.29E4 with an additional 88 peaks detected amid the implementation of an incubation step.