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Valdecoxib (VALD) selective electrodes based on VALD-5,6-diamino-2-thiouracil hydrochloride (DTUH) (VALD-DTUH) ion pair in PVC matrix membrane were constructed. The plasticizers used were dibutylphthalate (DBP) (Electrode B) tri-n-butylphosphate (TBP) (electrode C), or dioctylphthalate (DOP) (electrode) A. The electrodes gave the linear range between 6.0×10 −6 -17.9×10 −3 , 2.5×10 −5 -8.3×10 −3 M, M and 2.5×10 −6 -2.0×10 −2 M respectively. The slopes for linear range ranged from 39.29 to 58.76mV/decade with correlation coefficients lying between 0.997, 0.989 and 0.999 respectively. The best detection limit was 1.50×10−6 M for the electrode based on DOP. Selectivity coefficients of VALD related to a number of interfering cation and some organic compounds and excipients were studied using matched potential method (MPM(, and there were negligible interference caused by most of the investigated species. The pH and life time of the electrodes were also studied. The direct determination of VALD shows an average recovery of (100.08-100.61 and 99.75-101.00)% and a mean relative standard deviation of (2.70-0.61 and 2.39-0.56)% for sensor A and B respectively. The results obtained by determination of VALD in tablets using the proposed sensors which comparable favorably with those obtained by spectrophotometric method. Validation of the method shows the suitability of the electrodes for the determination of VALD in pharmaceutical formulation.

A simple, rapid and sensitive spectrophotometric method was developed for the determination of Se (IV) using 5,6-diaminouracil hydrochloride (DAUH) as an analytical reagent. The reagent has been synthesized and characterized using IR, 1H NMR. The metal ion in aqueous medium forms yellow colored complex with DAUH showing maximum absorbance at 343 nm. Hence, analytical studies were further carried out at 343 nm. The reagent reacts with selenium in acidic medium to form yellow colored 1:1 (M:L) complex . The color reactions are instantaneous and absorbance values remain constant for one week. The composition of the Se (IV) complex with DAUH was studied by the method of job's continuous variation and molar ratio method. Beer's law was obeyed in the range 0.2-15.0 μg mL −1 of Se (IV). The molar absorptivity and Sandell's sensitivity of the method were found to be 0.5×10 +4 L.mol -1 .cm -1 and 0.031μg.cm -2 respectively. Since DAUH method is more sensitive, it was applied for the determination of selenium in samples.

Valdecoxib (VALD) selective electrodes based on VALD-5,6-diamino-2-thiouracil hydrochloride (DTUH) (VALD-DTUH) ion pair in PVC matrix membrane were constructed. The plasticizers used were dibutylphthalate (DBP) (Electrode B) tri-n-butylphosphate (TBP) (electrode C), or dioctylphthalate (DOP) (electrode) A. The electrodes gave the linear range between 6.0×10−6-17.9×10−3, 2.5×10−5–8.3×10−3M, M and 2.5×10−6–2.0×10−2M respectively. The slopes for linear range ranged from 39.29 to 58.76mV/decade with correlation coefficients lying between 0.997, 0.989 and 0.999 respectively. The best detection limit was 1.50×10−6M for the electrode based on DOP. Selectivity coefficients of VALD related to a number of interfering cation and some organic compounds and excipients were studied using matched potential method (MPM(, and there were negligible interference caused by most of the investigated species. The pH and life time of the electrodes were also studied. The direct determination of VALD shows an average recovery of (100.08-100.61 and 99.75-101.00)% and a mean relative standard deviation of (2.70-0.61 and 2.39-0.56)% for sensor A and B respectively. The results obtained by determination of VALD in tablets using the proposed sensors which comparable favorably with those obtained by spectrophotometric method. Validation of the method shows the suitability of the electrodes for the determination of VALD in pharmaceutical formulation.

A simple, rapid and sensitive spectrophotometric method was developed for the determination of Se (IV) using 5,6-diaminouracil hydrochloride (DAUH) as an analytical reagent. The reagent has been synthesized and characterized using IR, 1H NMR. The metal ion in aqueous medium forms yellow colored complex with DAUH showing maximum absorbance at 343 nm. Hence, analytical studies were further carried out at 343 nm. The reagent reacts with selenium in acidic medium to form yellow colored 1:1 (M:L) complex . The color reactions are instantaneous and absorbance values remain constant for one week. The composition of the Se (IV) complex with DAUH was studied by the method of job’s continuous variation and molar ratio method. Beer’s law was obeyed in the range 0.2-15.0 μg mL−1of Se (IV). The molar absorptivity and Sandell’s sensitivity of the method were found to be 0.5×10+4 L.mol-1.cm-1and 0.031μg.cm-2 respectively. Since DAUH method is more sensitive, it was applied for the determination of selenium in samples.