Sorption integrated with detection

Figure 5.13 — Irreversible-reusable flow-through sensor for the kinetic multidetermination of phosphate and silicate based on integrated sorption of a reaction product, reaction (/ situ reduction) and photometric detection. (A) Microsensor block (1) and components (2). (B) Continuous-flow configuration coupled on-line to the sensor. P peristaltic pumps SV switching valve W waste. For details, see text. (Reproduced from [39] with permission of the American Chemical Society).

The applicability of the Pt deposition precipitation technique (DP) on mesoporous silica has been evaluated and discussed. A detailed synthesis procedure is given, and a suitable support from the SBA-15 family has been identified. The material synthesized at the conditions described here was clearly able to withstand the severe conditions of the DP treatment, indicating improved hydrothermal stability. The incorporation of the active species was accomplished without compromising the structural integrity of the parent material, as monitored by XRD and N2-sorption measurements. Using UV-Vis diffuse reflectance spectroscopy we were able to detect the platinum surface complex that coexists with platinum nanoparticles on the impregnated solid. 

Integrated sorption-detection units are based on the placement of an inert or active support in the flow cell of a nondestructive spectroscopic detector where the analytes or their reaction products are retained temporarily for sensing immediately after their elution. The equipment required to develop this type of sorption methodology is very simple and closely resembles that used in ordinary flow injection analysis (FIA) manifolds. The only difference lies in the replacement of the packed reactor located in the transport-reaction zone with a packed flow cell (usually photometric or fluorimetric) situated in the detector. 

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