Ani Mulyasuryani

Organophosphate Hydrolase in Conductometric Biosensor for the Detection of Organophosphate Pesticides.

The research has developed an enzyme biosensor for the detection organophosphate pesticide residues. The biosensor consists of a pair of screen-printed carbon electrode (SPCEs). One of electrodes contains immobilized organophosphate hydrolase (OPH) on a chitosan membrane by cross-linking it with glutaraldehyde. The area of the electrodes was optimized to 3, 5, and 7 mm2. The OPH was isolated from Pseudomonas putida, and was purified by the ammonium sulfate precipitation method, with 6444 ppm (A) and 7865 ppm (B). The organophosphate pesticide samples were 0–100 ppb in tris-acetate buffer 0.05 M, pH 8.5. The results showed that the best performance of the biosensor was achieved by the enzyme A with an electrode area of 5 mm2. The sensitivity of the biosensor was between 3 and 32 µS/ppb, and the detection limit for the organophosphate pesticides was 40 ppb (diazinon), 30 ppb (malathion), 20 ppb (chlorpyrifos), and 40 ppm (profenofos).

Kinerja Biosensor Konduktometri Berbasis (Screen Printed Carbon Electrode) SPCE––Kitosan untuk Deteksi Diazinon, Malation, Klorpirifos dan Profenofos

The performance of biosensor is based on the hydrolysis reaction of organophosphorus compounds catalyzed by organophosphate hydrolase (OPH), produce H + and the other ionic species that increase conductance on the surface of electrode. In this research, OPH was immobilized by crosslinking on chitosan–glutaraldehyde membrane on the ( Screen Printed Carbon Electrode ) SPCE surface. Measurements were carried out at the range concentration 0 to 3.0 ppm of organophosphate, the range of pH 7.0 to 9.0 and 5–25 mL of enzyme. The result showed that optimum performances were obtained at 25 mL of OPH, pH 8.5, with the sensitivity for dizinon, malathion, chlorpirifos and profenofos is 1.353 mS/ppm, 1.270 mS/ppm, 1.230 mS/ppm dan 1.77 mS/ppm respectively and 0.97; 1.03; 0.98; 0.97 of LOD. DOI :http://dx.doi.org/10.15408/jkv.v0i0.3156 .

Cu (II) Recovery with Solid Phase Extraction Technique Using Silica Adsorbent from Rice Husk ash - Chitosan

Copper compounds are widely used in modern industry. Many of these compounds are dumped into the surrounding environment. Copper is toxic and able to cause some diseases. The aim of this study is to create solid phase from natural material that applied to the solid phase extraction method as an alternative method to decrease the level of copper from water bodies and able to preconcentrate Cu 2+ ions, reaching the detectable level. Silica from rice husk ash modified with chitosan result in an adsorbent that can improve the adsorption of Cu 2+ . Interaction of Cu 2+ with solid phase silica–chitosan is based on data of Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The percentage recovery of Cu 2+ each the Cu 2+ concentration of 0.05, 0.1 and 0.2 ppm is 55.32%, 54.35% and 71.94%. The adsorbent has ability to adsorb Cu 2+ is 100%.