Jocud of zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Chromatography, 198 (1980) 235-239 Elkier Scientifk Publishing Company, Amsterdam- Printed in The Netherlands zyxwvutsrqponmlk CHROM. 12$93 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA INFLUENCES OF DETECTOR TIME CONSTANT VARIATIONS ON EFFI- CIENCY CALCULATIONS IN THE STANDARDISATION OF HIGH-PER- FORMANCE LIQUID CHROMATOGRAPHIC COLUMNS GARY K. C. LOW and PAUL R. HADDAD* Department of Anatyticaf Chemistm, University of N-S. W.. Kekngton, 2033 N.S. W. (Australia) (First received January 28th. 1980; revised manuscript received April 15th. 1980) SUMMARY This paper reports zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED the influences of detector time constant variations od plate count calculations and peak retention times in the standardisation of high-perfor- mance liquid chromatographic columns. A recommendation is made here that column efficiencies should be quoted at zero time constant in order to remove the variability in plate count introduced by varying time constant. For detectors which do not have variable time constant controls, it is recommended that the calculation of plate num- bers should be made on solutes having capacity factors in the region 5-6. Further recommendations made are that the peak symmetry correlation ratio should be used to evaluate system performance only when calculated at zero time constant and that the detector time constant should not exceed one hundredth of the peak width for peaks used in the calculation of plate numbers. INTRODUtX’ION Peak asymmetry is an important aspect in relation to resolution and column performance in high-performance liquid chromatography (HPLC). The major con- tributions to peak tailing arise from voids or channelling in the column itself and also from extra-column effects chiefly due to solute diffusion in tube connectors, precol- umns, cell volume of the detector and the injector system’“- A further contribution which has not often been recognised is that improper time constant settings on W detectors of the HPLC system can also cause peak asymmetry. Two important terms, the “time constant” (z) and the “response time” (t) are often referred to in the literature. The former term is the time required for the recorder to reach 632% of its final value and the manner in which the detector time constant affects peak shape and peak height has been briefly discussedby Stewart!. The latter term is the time required for the recorder to reach 99.7% of its tial value and is equal to five times the time constant. In a study of the use of a modified scanning spectrophotometer as a variable- wavelength detector for HPLC, Higgins* noted that HETP (height equivalent to a theoretical plate) values and peak symmetry were dependent on the time constant of 0021-9673/8O/oOOMMOO /SO225 @ 1980 Ekevier Scientific Publishing Company