This paper presents the grid search procedure as a simple and efficient
optimization method for the selection of thin-layer
chromatography solvent system. The relationship between R_f and the proportions, X_1,X_2,X_3, ...,X_(n-1),of more polar solvents in developer can be expressed as ln(1 /R_f - 1 ) =b_0+b_1 lnX_1+b_2,lnX_2 +b_3lnX_3 +. +b_(n_1),lnX_(n-1),with X-1 + X_2 + X_3 + ... + X_(n-1) + X_n= 1, where X_n is the proportion of the least polar solvent. Two chromatographic
optimization functions (COF) are used to judge the separation quality. (1)If the separation of all peaks is equally desirable, the COF is defined as When |△Rfi|>0.1,|△Rfi|is set equal to 0.1 ;(2)If one or more separations of peak pair is more important than the others,the COF is defined as. Where ωi is the weighting factor for the ith pair of peaks.The algorithm is programmed on a micro-computer.With the data of uniform design experiment,computer simulation is carried out and finally the optimum solvent systems are located. The above procedure was successfully applied to the separation of 6 sorts of penicillin drugs on silica layers. The optimum solvent compositions were chloroform-acetone-ethanol-formic acid of 0.64:0.09:0.16:0.11 and of 0.58:0.23:0.09:0.10. Plates were exposed to iodine vapor and scanned immediately after being enclosed. Measurements were made in the reflectance mode at the wavelength of 380nm.