Comparison of the Limit of Detection of Paracetamol, Propyphenazone, and Caffeine Analyzed by TLC and HPTLC

Abstract

TLC and HPTLC in normal (NP) and reversed (RP) phase systems combined with densitometry were used to analyze caffeine, propyphenazone and paracetamol. Normal phase analyses were performed on five different stationary phases (chromatographic plates), testing three mobile phases. Reversed-phase analyses were performed on four different chromatographic plates using three mobile phases. Thus, it was checked whether analyses using TLC chromatographic plates could be as sensitive as those performed on HPTLC plates. For all analyzed biologically active substances, the limit of detection (LOD) was calculated, i.e. a parameter that describes the method sensitivity. It has been shown that using both TLC and HPTLC plates, it is possible to develop chromatographic conditions that enable the detection of caffeine, propyphenazone and paracetamol in amounts ranging from a dozen to several dozen µg/spot. In the reversed-phase (RP) system, lower LOD values for all tested compounds were obtained using TLC than HPTLC. However, using analyses in the normal phase system (NP), similar (of the same order) LOD values are obtained for caffeine, propyphenazone and paracetamol, both when using TLC and HPTLC plates. Therefore, for economic reasons, TLC plates should be recommended for analyses of caffeine, propyphenazone and paracetamol, which are several times cheaper than HPTLC plates.