The Study On Calibration Methods For Prediction Of Temperature Programmed Retention Times Under Different Film Thickness In Gas Chromatography

Retention time is an important parameter in optimizating separation conditions and identifying unkown compounds.There are many factors affecting the retention times,such as the property of solutes,the velocity of the gas carrier,the column temperature and the type of column.Under the same separation conditions,the variation of column length,diameter and film thickness will cause the change in retention times.If the column is replaced by another one of different film thickness to satisfy the separation requirments,it is tedius and time-consuming to remeasure the basic isothermal data.As a consequence of this prime consideration,we proposed three different calibration methods to predict the retention times in columns of different film thickness but the same stationary phase based on the nonlinear plate theory and retention equation.The first method neglects the difference between 1/? and 1,and directly calibrates the hold-up time by using the programmed temperature retention times of a target compound,which is easy and feasible.The second method uses the isothermal retention times of the target analyte to calibrate the parameters tM and ? by linear fitting,the average errors are mostly less than 5%.The third method calibrates the parameters tM and ? directly using the programmed temperature retention times.As the basic retention data in column 1 is adopted to predict the retention times in column 2,the precision of the prediction results has improved a lot.Most average errors are less than 3%.As the basic retention data in column 2 is adopted to predict the retention times in column 1,the average absolute relative errors exceed 3% only by using butyl acetate and tetrachlorethylene for calibration,and other mean errors are all within 3%.Meanwhile,the calculation of retention factors in the reference column is further simplified by using a single value of tM,the prediction results are almost completely unaffected by the simplification.