The silica nanoparticles prepared by stober's mechanism by reaction of tetraethylorthosilicate (TEOS) with ammonia was tested for their adsorption capacity in the pre-concentration of residues of pesticides in water. The synthesized nanoparticles were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD). The size of the silica nanoparticles were 50 to 250 nm. The solid phase extraction (SPE) cartridges were prepared by filling the empty cartridges of 5.5 cm length and 0.3 cm i.d. with 200 mg of nanoparticles and protected between two polytetrafluroethylene (PTFE) frits. To avoid the passage of nanoparticles, 2% solution of polystyrene in chloroform was passed through PTFE frits and dried in air for two hours at room temperature before fitted into the cartridges. This process is to reduce the pore size of the PTFE frits. These cartridges are used in pre-concentration of different types of residues of pesticides in water. The pyrethroids tested for the pre-concentration are tetramethrin, lambda-cyhalothrin, cyphenothrin. The water samples were spiked with aliquots of pesticides and were passed through the cartridges. The amounts of the pesticides adsorbed on the cartridges were tested. The influence of temperature, sample volume, flow rate, pH and ionic strength on the performance of the cartridges was checked. The results of fortified sample analysis were compared with the data obtained from the commercially available C18 cartridges for the sample volume. The separation parameters were established for the simultaneous determination of residues using GC-EI-MS. The method was validated by means of linearity, precision, and assay accuracy. The limit of detection (LOD) and the limit of quantification (LOQ) were established based on the signal to noise ratio 3:1 and 10:1 respectively. An analytical method for the enrichment of residues using nanoparticles based SPE cartridges were developed and factors influencing the pre-concentration of residues of pyrethroids were studied and reported.

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Tolterodine is used to treat overactive bladder symptoms such as loss of bladder control (incontinence) or a frequent need to urinate. A simple and inexpensive method was developed with high performance liquid chromatography with PDA detection for determination of tolterodine and related impurities.  The chromatographic separations were achieved on (250 × 4.6 mm), 5.0 µm make: symmetry, C8 column employing methanol and 0.1% orthophosphoric acid in water, in the ratio of 90:10 as mobile phase with gradient programmed at flow rate 1.0 mL/min was chosen. Three impurities were eluted within 35 minutes. The column temperature was maintained at 35oC and a detector wavelength of 220 nm was employed. The method was successfully validated by establishing system suitability, specificity, linearity, accuracy, LOD and LOQ. The validated method is useful for tolterodine assay in pharmaceutical products.