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In many cases of use of commonly-available ODS silica gel fillers, there occur problems of tailing and broadening of basic compounds. Although these problems have been considered to be caused by improper end capping rate, they have not been solved only by improvement of the rate. Therefore, efforts have been made to examine the methods of further octadecyl silylation and secondary silylation and increase the coverage. However, also the metallic content in silica gel is relevant to these problems, and the causes are being identified experimentally. Although direct and indirect influences of residual silanols(neutral, acidic and free silanols) and metal on samples have not been clarified, the low-metallic content fillers, Wakosil®-II Series, show the following results.

Column Size ：4.6 mm×150 mm Eluent ： CH3OH/CH3CN/5 mM Citric buffer（pH 4） =10/20/70（v/v） Flow Rate ：1.0 mL/min. at 40℃ Detection ：UV 230 nm Sample ：1）Benzoic acid 　　　　　 2）Sorbic acid 　　　　　 3）Dehydroacetic acid Na salt		Column Size ：4.6 mm×150 mm Eluent ：CH3OH/20 mM 　　　　　 KH2PO4-K2HPO4（pH 7.6） 　　　　　=70/30（v/v） Flow Rate ：1.0 mL/min. at 30℃ Detection ：UV 254 nm Sample ：1）8-Quinolinol		Column Size ：4.6 mm×150 mm Eluent ：CH3CN/H2O=60/40（v/v） 　　　　　+0.05% EDTA・2Na Flow Rate ：1.0 mL/min. at R.T. Detection ：UV 254 nm Sample ：1）Hinokitiol

■Examples of application of compounds to be analyzed and fillers Examples of structures which are affected by metal in silica gel Examples of structures which are affected by residual silanol groups

Substance to be analyzed		Coordinate bonding capability
		High	Low
Basicity	High	Navi Series, Wakosil®-II C18 series	Navi Series, Wakosil®-II C18 Series, Wakosil® C18 Series
	Low	Navi Series, Wakosil®-II C18 Series	Navi Series, Wakosil®-II C18 Series, Wakosil® C18 Series, Wakosil® C18T, N Series

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