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Abstract
As a simple, rapid, low-cost method for densitometric evaluation of thin-layer chromatography (TLC), image analysis has increased in popularity in pattern recognition and fingerprint analysis in the context of TLC. Nonuniform image backgrounds and retention factor (Rf) variation are notable problems for the similarity measure of TLC by means of image analysis. In this work, their influences were studied. An image correction method and a chromatogram alignment method were designed. A Citrus herbal medicine was determined nine times on one plate and six times on independent plates separately. Mutual similarities of densitograms of replicate samples were measured using cosine measure and Pearson’s correlation measure. Paired-samples t-test was used to compare the means of the mutual similarities between two treatments. At last, a case study of classification of eight Citrus herbal medicines using hierarchical clustering was performed. The image correction and chromatogram alignment methods described in this work were proven effective. Image correction had a small influence on the similarity measure while chromatogram alignment had a great influence. Image correction and chromatogram alignment should be considered in the similarity measure of TLC by means of image analysis.