Metal sorption, solid phase extraction and preconcentration properties of two silica gel phases chemically modified with 2-hydroxy-1-naphthaldehyde

Active silica gel phase (I) was chemically modified to the corresponding amino- (equivalent toSiNH(2)) and chloro- (equivalent toSiCl) derivatives via silylation reactions. These were used to synthesize two newly modified silica gel phases (II, III) by direct chemical reaction with 2-hydroxynaphthaldehyde (2-HNA). The surface coverage values are 370, 432 mumol g(-1) and 320, 355 mumol g(-1) for (II) and (III), on the basis of thermal desorption and metal probe testing method, respectively. The metal sorption properties of silica gel phases (II, III) were studied and compared with active silica gel phase (I). The maximum determined metal capacity values were found to be 10-110, 20-290 and 20-370 mumol g(-1) for phases I, II and III, respectively. The distribution coefficient values (K-d) were also determined for a series of metal ions, and the results showed that the two new chemically modified phases (II and III) were highly selective for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+. The potential applications of silica gel phases (II, III) as solid phase extractors for the same five metal ions spiked in drinking tap water (similar to1.000 mug mL(-1)) were found to give percentage recovery values in the range of 90.2-96.3 +/- 4.1-6.3%, while pre-concentration of the same five metal ions spiked in drinking tap water (similar to50.0 ng mL(-1)) was successfully accomplished with a percentage recovery range of 92.6-95.8 +/- 4.8-5.7%.