Salah M. Sultan

Use of cerium(IV) sulphate in the spectrophotometric determination of paracetamol in pharmaceutical preparations

An accurate spectrophotometric method is proposed for the determination of paracetamol. Cerium(IV) sulphate is used to oxidise paracetamol in 5 M H2SO4 to p-benzoquinone, which is then determined at 410 nm. The method has been successfully applied to the analysis of commercial pharmaceutical preparations and the results have been statistically compared with those obtained by the official (BP) method.

Complexometric-spectrophotometric assay of tetracyclines in drug formulations.

An accurate, rapid and very simple spectrophotometric method for the assay of tetracyclines (tetracycline.HCl, chlorotetracycline.HCl, demeclocycline, oxytetracycline.HCl and doxycycline) has been developed. The method is based on the complexation of iron(III) with tetracyclines in 0.001M sulphuric acid. It has been successfully applied to the assay of tetracyclines in drug formulations, and the interferences of excipients have been examined. The results have been statistically compared with those obtained by two standard methods and found to be very satisfactory.

Sequential injection technique for automated titration: Spectrophotometric assay of vitamin C in pharmaceutical products using cerium(IV) in sulfuric acid

For the first time sequential injection analysis (SIA) technique has been employed for titrimetry. A new SI titrimetric spectrophotometric method for the assay of vitamin C in drug formulations was explored. The method is based on the oxidation reaction of vitamin C with cerium(IV) in sulfuric acid media using a spectrophotometer as a detector with the wavelength monitored at 410 nm. A 2(3) factorial design chemometric approach was employed to study the interaction effect of the chemical and system variables, mainly cerium(IV), sulfuric acid concentrations and the flow rate. The results of the chemometric optimization revealed that the optimum operating conditions for the SI titrimetric analysis of vitamin C were 7.0 x 10(-3) M cerium(IV), 0.455 M sulfuric acid and 28.9 microL s-1 flow rate. A linear calibration plot for the determination of vitamin C was obtained in the concentration range between 30 to 200 ppm. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference, thus rendering the method suitable for the determination of the drug in pharmaceutical preparations. The SIA method is found to be accurate when the results were statistically compared with the results obtained by the BP standard method. The SIA method is superior when compared to the conventional titration method, the BP standard method and previous methods with respect to precision and automation in solution handling.

Spectrophotometric determination of paracetamol in drug formulations by oxidation with potassium dichromate

A rapid spectrophotometric method for determination of paracetamol is described, based on oxidation with dichromate for 15 min in 6M sulphuric acid at 80 degrees , and measurement (at 580 nm) of the chromium(III) formed. The method is applied to the determination of paracetamol in drugs prescribed for colds, coughs and flu. Of the common pharmaceuticals associated with paracetamol, only ascorbic acid and acetylsalicylic acid interfere. The results have been statistically compared with those obtained by the official (BP) and cerium(IV) methods.

Spectrophotometric determination of tetracycline with sodium molybdate.

A spectrophotometric method is described for the determination of tetracycline hydrochloride. The drug is reacted with sodium molybdate at the boiling-point for 15 min in hydrochloric acid medium. The absorbance of the colour developed is measured at 430 nm. The method is simple, reproducible and accurate and is easily applied to the determination of the drug in the pure form and in pharmaceutical preparations.

Kinetic determination of propranolol in drug formulations

A kinetic method for the accurate determination of propranolol has been developed. A solution of propranolol is heated with 2.72 × 10–2M potassium dichromate in 5 M sulphuric acid at 90 °C for a fixed time of 20 min, after which the reaction is quenched by cooling and the absorbance of the coloured chromium(III) species produced is measured at 590 nm. The concentration of propranolol is calculated by using the corresponding calibration equation for the fixed-time method. The method has been applied to proprietary drugs and the results were compared statistically with those given by the BP method. The determination of propranolol by the fixed-concentration and rate-constant methods is feasible with the calibration equations obtained but the fixed-time method has been found to be more applicable.

Use of the sequential injection technique to determine the concentrations and stoichiometries of trimeprazine and perphenazine complexed with palladium(II) in hydrochloric acid

An automated method for the determination of trimeprazine and perphenazine by complexation with palladium(II) in hydrochloric acid was developed. A sequential injection technique with a flow reversal of 29.4 µl s–1 and a measuring cycle of 73 s was used. Trimeprazine in the range 50–400 ppm was determined at pH 4.7 using 5.0 × 10–3 mol l–1 palladium(II) solution and monitoring the product spectrophotometrically at 515 nm. Perphenazine in the range 50–500 ppm was determined at pH 4.85 using 2.5 × 10–3 mol l–1 palladium(II) solution and monitoring the product at 560 nm. The technique was successfully applied to the determination of reaction stoichiometry. Interferences were studied and the method was found to be suitable for the determination of the two compounds in pharmaceutical preparations.

Flow injection stopped-flow kinetic determination of the anxiolytic sedative bromazepam in dosage forms

A highly selective and accurate flow injection (FI) method for the determination of bromazepam has been developed. The method is based on the chelation of bromazepam with iron(II) to form a complex that absorbs at a maximum wavelength of 585 nm. Optimization of FI and chemical parameters is achieved by the univariate and the computerized modified simplex methods. The drug (157 µl) is injected into 0.072 mol dm–3 iron(II) solution, both previously prepared in 0.02 mol dm–3HCI, at a flow rate of 3.81 ml min–1 and allowed to mix and react in a coil (100 cm × 0.5 mm i.d.) for a fixed time of 300 s. A relative standard deviation of 0.66% with a recovery of 99.9% is achieved and the method is suitable for the determination of bromazepam in tablet formulations.

Simultaneous Kinetic Method for the Determination of Vitamin C, Citrate and Oxalate Employing the Kalman Filter

A kinetic method for the determination of vitamin C, citrate and oxalate in their mixture is described. The method involves the use of cerium(IV) as an oxidant and measurement of reaction rates spectrophotometrically by following the decrease in absorbance of cerium(IV) at 410 nm. The adaptive Kalman filter was used for data manipulation and analysis. It is shown that the use of the Kalman filter is superior to the classical differential kinetic methods owing to its suitability for the determination of analytes that react with a single reagent and exhibit a reaction rate constant ratio of less than 1.5. The results obtained were found to be highly precise and accurate even in the presence of some expected interferents.

Sequential Injection Analysis Technique for the Concentration,Stoichiometry and Formation Constant Studies of Promethazine HydrochlorideComplexed With Palladium(II) in Hydrochloric Acid

The sequential injection analysis (SIA) technique was successfully napplied to the determination of promethazine hydrochloride in drug nformulations. The chemical system is based on the complexation reaction of npromethazine hydrochloride with Pd n II n in 8.0 × n10 n - n n 4 n mol dm n - n n 3 n HCl nand measurement of the absorbance at 504 nm. Promethazine was determined nin the range 50–400 ppm using 1.0 × n10 n - n n 3 n mol dm n - n n 3 n nPd n II n with an aspiration volume of 147.5 µl. The SIA ntechnique was utilized for the determination of the concentration, nstoichiometry and formation constant of the complexation reaction. The ntechnique was found to be superior to flow injection analysis. The SIA nmethod was statistically compared with the official British Pharmacopoeia nmethod and showed comparable accuracy, but with the advantages of nselectivity, simplicity, speed and amounts of reagents consumed.