Planar solid phase extraction for chlorinated paraffin analysis – irradiation chamber for standardized derivatization on planar thin-layers

As an established analytical method, high-performance thin-layer chromatography (HPTLC) offers powerful capabilities. This study focused on its application to analyze chlorinated paraffins (CP) by planar solid phase extraction (pSPE). Based on previous work, an irradiation chamber was developed to investigate the derivatization process on planar thin-layers and ensure a robust and reproducible analysis. A simple-to-handle irradiation chamber was designed to initialize the reaction between CP and the derivatization reagents o-tolidine and tetramethylbenzidine (TMB). It was shown that the complete derivatization reaction is not significantly influenced by the chain length and only depends significantly on the chlorine content of the used standards. Regarding the reaction process, a relation between the chain length and chlorine content was obtained; however, quantitative correlations cannot be found. Furthermore, the derivatization solutions were investigated in terms of stability, different concentrations, and the optimal irradiation time. The method showed robustness regarding signal intensity at irradiation times of 1 to 36 min and amounts of 10-400 ng of the technical reference CP mixture C₁₄-C₁₇ 52 % Cl. Its application to CP with chain lengths between C₁₀ and C₂₃ and chlorine content between 40 % and 70 % emphasized the method's versatility.