Comparative study of four different C 18 HPLC columns with different particle sizes and lengths for the optimization of UV absorbing engine coolant additives analysis

The performance of four different C 18 chromatography analytical columns with different lengths and particle sizes were compared for analysis of engine coolant additives such as benzotriazole (BTz), tolyltriazole (TTz), sodium benzoate and cinnamic acid using high performance liquid chromatography (HPLC) with UV-visible detector. Chromatographic parameters including retention time, resolution, limit of detection (LOD), limit of quantification (LOQ), number of theoretical plates and reduced plate height were evaluated and compared. In this work, the performance of 5µm particles of Kinetex and Acclaim C 18 chromatography columns has been compared with new positive surface (PS) and polar C 18 columns having 3µm particles for the analysis of above additives. The results show that in comparison with the traditional columns having dimensions 250 mm×4.6 mm; 5µm, shorter columns namely polar C 18 and positive surface (PS C 18 ) having dimensions 150 mm×4.6 mm; 3 µm allowed the reduction of the analysis time by 44.8% and 45.8% respectively without compromising on column performance. This leads to the reduction of analysis expenses by reducing the organic solvents and time, and increasing the total number of analyses per day. Among two smaller columns, the resolution of positive surface C 18 is found to be better as compared to polar C 18 column though the analysis times remains almost same. The mobile phase CH 3 OH (70%): 0.5%H 3 PO 4 in water (30%) was used at a flow rate of 0.8 mL/min and the injection volume in all the case was 20.0 µl. The capabilities of these columns for analyzing engine coolant samples in glycol based aqueous media were evaluated.