A highly selective and sensitive monohydrogen phosphate (MHP) sensor has been fabricated by constructing a poly vinyl chloride (PVC) matrix membrane containing a new oxo-molybdenum methyl-salen (MS) as a neutral carrier, hexadecyltrimethyl ammonium bromide (HTAB) as a cationic additive, benzylacetate (BA) as a plasticizing solvent mediator. The membrane sensor exhibits linear potential response in the concentration range of 1.0 ×10-1 - 4.0 × 10-7 mol L-1 of MHP. The electrode displays a Nernstian slope of -28.6 ± 0.3 mV decade-1 in the pH of 8.5. The proposed sensor also exhibits a fast response time of <l5 s. The detection limit of the proposed sensor is 2.0 × 10-7 mol L-1 (~20 ng mL-1), and it can be used over a period of eight weeks without significant changes in its response. The selectivity of the sensor with respect to other common organic and inorganic anions (e.g. Chloride, bromide, iodide, nitrate, sulfite, sulfate, carbonate, perclorate, cyanide, thiocyanate, dihydrogen phosphate, tetrasodium pyrophosphate, and sodium tripoly phosphate ions) is excellent. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of MHP with Ba2+ ions and for the direct determination of MHP in granular and liquid fertilizer samples as well waste water samples.
monohydrogen phosphate; PVC membrane; sensor; oxo-molybdenum methyl-salen; potentiometry
