This article describes a straightforward method for the quantification of thiol groups on the surface of chromatographic particles such as
3-mercaptopropyl silica gel. The method is based on a thiol-disulfide exchange reaction with 2,2-dipyridyl disulfide (DPDS) reagent and
spectrophotometric or HPLC-UV determination of the liberated 2-pyridyl thione. Linearity was obtained over the sulfhydryl concentration
range of 0.02–0.5 mol ml−1 for the spectrophotometric determination and 0.2–5 mol ml−1 for the HPLC-UV measurement, with r2 values of
0.9975 and 0.9981, respectively. The results were validated using elemental analysis as independent control method. The agreement between
the results of both methods indicates that the sulfur of the thiol-modified silica particles is available as reactive sulfhydryls. The repeatability
study indicated a higher precision for the DPDS method compared to the elemental analysis.
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