Figure 34 : Compare analysis: Sample A is an authentic product. Samples Q1, Q2, Q3 have to be checked for authenticity. µ-PLC compare analysis is done. We only look for qualitative results. It is absolutely sure that Q1, Q2, Q3 are NOT authentic products. Q3 is over a wide length of the substance bows overlapped with Q2 and A. Absolutely sure: Q3 is chemically not A and Q2. But between Q2 and Q1 there is no visible overlapped area which surely tells, that Q2 differs from Q1. Let us name the substance bow at about 60 % of the range [center to chromatogram front] position Pr = 60 and the bow of the main substance at about 70% of the range [center to chromatogram front] position Pr = 70, then it may be correct: Substance A has no Pr = 60 substance. But Q1 contains some more substance at Pr = 60 than Q2. The Pr = 70 substance in Q1 and Q2 may be equal to Pr = 70 in the authentic substance A. We need multi integration data from sectors next to clock position 6:00, 9:00 and 12:00. We may need either multiple µ-PLC runs with differing mobile phases on differing stationary phases and should try multi phase development. Possibly an MS analysis of the substance at Pr = 70 in A, Q1 and Q2 is the fastest way to clear some questions. But the answer for Q3 is doubtlessly clear: Q3 is NOT product A. But at Pr = 60 there may be an impurity which is not visible in A. And if we know nothing about the chemical(s) behind at Pr = 60 and if Q1, Q2 and Q3 are medical products, we should tell the patient: take A only if this is the correct and safe product to cure your problems. NOTE Pr - data are position data given in percent of the full final circle radius of the mobile phase. P = position, r = radius.