Comparison of 624-type Capillary Columns

"Equivalent Columns" Deviation in the Quantitative Analysis

Abstract

In our research, seven 624-type capillary columns were investigated. All the columns were the same in length, internal diameter, and film thickness (30 m × 0.32 mm × 1.0 µm). However, they were produced by different manufacturers or the same manufacturer but in different batches. Even though the manufacturers recommend them as "equivalent columns" this equivalence did not prevail even in the case of columns produced by the same manufacturer. Our examination criteria centered on the quantitative determination ability of the columns. A homemade column test mixture was compiled to represent all the second-order interactions that can occur between the analyte and stationary phase. Although theoretically these columns have the same stationary phase quality, they did not result in the same chromatograms. In addition to the origin and batch of the column, the "history of the column" contributes likewise to the different peak symmetry, retention order, and even peak areas that affect the quantitative determination. We quantified this quantitative determination ability with the effective carbon number (ECN) and the Limit of Quantitation (LoQ) values. Based on our results the attainable LoQ and ECN values depend at least as much on the origin and actual state of the stationary phase as on the measurement conditions to be optimized. In our paper, we demonstrate the extent to which the same stationary phases offered by different companies and/or different backgrounds can influence our detection limit and detector response even if the relevant columns have theoretically the same chemical structure.