Ratio subtraction and isosbestic point methods are two innovative spectrophotometric methods for determining the concentrations of metronidazole (I) and diloxanide furoate (II) in a mixture. Metronidazole was determined by direct spectrophotometric method at k max 314.0 nm in the presence of diloxanide furoate in the range of 4-24 lg ml À1 with a mean recovery percentage of 99.83 ± 1.41. Two spectrophotometric methods were developed for the spectral resolution of diloxanide furoate when present in mixture with metronidazole without preliminary separation. The first method depends on measuring the absorbance at the isosbestic point at 277.2 nm in the range of 5-30 lg ml À1 with a mean recovery percentage of 99.96 ± 1.47 for diloxanide furoate. The second method is the ratio subtraction spectroscopic method for spectral isolation of diloxanide furoate present in the mixture which can be measured at 251.2 nm in the range of 5-30 lg ml À1 with a mean recovery percentage of 99.73 ± 1.33 for diloxanide furoate determination. The suggested procedures were validated using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical preparations. The methods retained their accuracy and precision when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the reported method.

No abstract

Sofosbuvir and ledipasvir are the first drugs in a combination pill to treat chronic hepatitis C virus. Simple, sensitive, and rapid spectrophotometric methods are presented for the determination of sofosbuvir and ledipasvir in their combined dosage form. These methods were based on direct measurement of ledipasvir at 333 nm (due to the lack of interference of sofosbuvir) over a concentration range of 4.0-14.0 µg/mL, with a mean recovery of 100.78 ± 0.64%. Sofosbuvir was determined, without prior separation, by third-derivative values at 281 nm; derivative ratio values at 265.8 nm utilizing 5.0 µg/mL ledipasvir as a divisor; the ratio difference method using values at 270 and 250 nm using 5.0 µg/mL ledipasvir as a divisor; and the ratio subtraction method using values at 261 nm. These methods were found to be linear for sofosbuvir over a concentration range of 5.0-35.0 µg/mL. The suggested methods were validated according to International Conference on Harmonization guidelines. Statistical analysis of the results showed no significant difference between the proposed methods and the manufacturer's LC method of determination with respect to accuracy and precision. These methods were used to compare the equivalence of an innovator drug dosage form and two generic drug dosage forms of the same strength.

No abstract

Development of novel sensors for the determination of ivabradine hydrochloride using sulphonated calix-8-arene and cyclodextrin derivatives as neutral ionophores.