Experimental Reagents and materials L-Tyrosine and L-Alanine were purchased from Wako (Osaka, Japan), DCC was purchased from Wako chemicals. HOBt was purchased from Dojindo chemicals, Japan. YMC silica (SIL-120-S5) having diameter 5µm, pore size 12 nm and surface area 300m 2 g -1 (YMC-gel, Kyoto, Japan) was used for modification. HPLC-grade methanol, acetonitrile was obtained from Wako (Osaka, Japan) and Nacalei Inc. Co. (Tokyo, Japan) respectively. Ammonium acetate was purchased from Wako

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... cals, Japan. All nucleosides and nucleobases were commercially available and used without further purification. Sulfamethoxazole and Sulfamethoxypyridazine were obtained from TCI (Tokyo, Japan). Sulfadiazine was obtained from Sigma (St Louis, MO, USA). Sulfamonomethoxine and Sulfaquinoxaline were obtained from Wako (Osaka, Japan). Immobilization of APS on silica surface 3-aminopropyltrimethoxysilane (APS) grafted silica was prepared by refluxing porous silica gel (3.0 g) and (1.5 ml) APS in toluene for 24 hr. After successive washing with toluene, ethanol and diethyl ether the particles were dried in vacuum. The dried particles were characterized by elemental analysis. Synthesis of Tripeptide Boc-YAY-OH The tripeptide molecule was newly designed and synthesized by solution phase methodology (Scheme S1) for grafting with silica. Boc-Tyr(1)-OH (1) A solution of tyrosine 9.05 g (50 mmol) in a mixture of dioxan (100 mL), water (50 mL) and 1M NaOH (50 mL) was stirred and cooled in an ice-water bath. Di-tert-butylpyrocarbonate 10.4 g (52 mmol) was added and stirring was continued at room temperature for 6 hrs. Then the solution was concentrated in vacuo to about 15 to 20 mL, cooled in an ice-water bath, covered with a layer of ethyl-acetate (about 100 mL) and acidified with a dilute solution of KHSO 4 to pH 2-3 (Congo red). The aqueous phase was extracted with ethyl acetate and this operation was done repeatedly. The ethyl acetate extracts were pooled, washed with water and dried over anhydrous Na 2 SO 4 and evaporated in vacuo. The pure material was obtained. Yield = 11.2 g (40 mmol, 80%). 2 Boc-Tyr(1)-Ala(2)-OMe (2) 9.85 g (35 mmol) of Boc-Tyr(1)-OH was dissolved in a mixture of 20 mL dichloromethane (DCM) in an ice-water bath. H-Ala-OMe was isolated from 7.21 g (70 mmol) of the corresponding methyl ester hydrochloride by neutralization, subsequent extraction with ethyl acetate and concentration to 10 mL and this was added to the reaction mixture, followed immediately by 7.21 g (35 mmol) of di-cyclohexaylcarbodiimide (DCC). The reaction mixture was allowed to come to room temperature and stirred for 24 hrs. DCM was evaporated, residue Electronic Supplementary Material (ESI) for Analyst This journal is