Spectrophotometric Determination of Risedronate in Pharmaceutical Formulations via Complex Formation with Cu (II) Ions: Application to Content Uniformity Testing.

A simple, sensitive, rapid and accurate spectrophotometric method was developed for the determination of risedronate, a bisphosphonate drug important for the treatment of a variety of bone diseases, in raw material and pharmaceutical formulations. The proposed method is based on complex formation between risedronate and Cu (II) ions in acetate buffer of pH5.5. The optimum conditions for this reaction were ascertained and a spectrophotometric method was developed for the determination of risedronate in concentration range of 2-40 µg/mL with detection limit of 0.03 µg/mL (9.51 × 10(-8) mol/L). The molar absorbtivity was 8.00 × 10(3) l/mol/cm. The method was successfully applied for the determination of risedronate in tablet dosage form with mean percentage recovery of 101.04 ± 0.32. The results obtained were favorably compared with those obtained by the comparison method. Furthermore, the proposed method was applied for content uniformity testing of risedronate tablets.

Spectrophotometric determination of penicillamine and carbocisteine based on formation of metal complexes.

A simple spectrophotometric method was developed for the determination of penicillamine and carbocisteine. The method depends on complexation of penicillamine with Ni, Co and Pb ions in acetate buffer pH of 6.3, 6.5 and 5.3, respectively, and carbocisteine with Cu and Ni ions in borate buffer pH of 6.7; 1-70 microg/ml of these drugs could be determined by measuring the absorbance of each complex at its specific lambdamax. The results obtained are in good agreement with those obtained using the official methods. The proposed method was successfully applied for the determination of these compounds in their dosage forms. Also, the molar ratio and stability constant of the metal complexes were calculated and a proposal of the reaction pathway was postulated.

Kinetic spectrophotometric determination of some sulfur containing compounds in pharmaceutical preparations and human serum.

A kinetic spectrophotometric method was developed for the determination of carbocisteine, ethionamide, thioctic acid and penicillamine based on the catalytic effect on the reaction between sodium azide and iodine in aqueous solution. Ten to 100 microg ml(-1) of carbocisteine and ethionamide, 0.1-1 microg ml(-1) of thioctic acid and 0.01-0.1 microg ml(-1) of penicillamine could be determined, respectively, by measuring the decrease in the absorbance of iodine at 348 nm by a fixed time method. The decrease in the absorbance in the first 5 min from the initiation of the reaction is related to the concentration of the drugs. The detection limits were 0.47, 0.71, 0.018 and 9.38 x 10(-4) microg ml(-1) for the four drugs, respectively. The proposed procedure was successfully applied in the determination of these drugs in pharmaceutical preparations and human serum.

A selective fluorimetric method for the determination of some 1,4-benzodiazepine drugs containing a hydroxyl group at C-3.

A highly selective and sensitive fluorimetric method was developed for the determination of four 1,4-benzodiazepine drugs containing a hydroxyl group at carbon 3, namely oxazepam, lorazepam, cinolazepam and temazepam. The method is highly specific because other benzodiazepinee lacking the hydroxyl group at C-3 do not react similarly and hence do not interfere. The proposed method involves reduction of the target compound using Zno/HCl at room temperature with the formation of a highly fluorescent derivative within 15 min. The different experimental parameters were carefully studied and incorporated into the procedure. Under the described conditions, the proposed method is applicable over the concentration range of 0.1-1.2 micrograms ml-1 for both temazepam and cinolazepam, and 0.2-2.5 and 1-8 micrograms ml-1 for oxazepam and lorazepam respectively. The recoveries of the title compounds from spiked urine ranged from 90.0 to 92.0% and for serum from 94.1 to 95.4% with a limit of detection (S/N = 2) of 4 ng ml-1 for all drugs. The mechanism of the fluorimetric reaction is discussed.

Polarographic determination of N-acetyl-L-cysteine in pharmaceutical preparations.

The polarographic behaviour of N-acetyl-L-cysteine in Britton Robinson Buffer (BRB) over the whole pH range was studied. At pH 10, a well-defined anodic wave was developed. The wave was irreversible, one-electron, diffusion-controlled and partially affected by adsorption phenomenon. Adopting both direct current (DCT) and differential pulse polarographic (DPP) modes, the current concentration plot is rectilinear over the range 0.05 to 1.0 mM and 0.01 to 0.75 mM, respectively, with a minimum detection limit of 0.0005 mM using the DPP mode. The proposed method was successfully applied to the determination of N-acetyl-L-cysteine in pharmaceutical preparations. The obtained results were in a good agreement with those obtained by the official method.

Percentages of the deuterium retained after para-hydroxylation of (R)(+)4-2H-phenytoin and (S)(-) 4-2H-phenytoin in rat.

(R)(+) and (S)(-) 4-2H-phenytoin have been used as substrates for the determination of the percentage of deuterium retention (NIH shift) after para-hydroxylation of the substrates in rat. By using GC-MS analyses, the percentages of deuterium retention were found to be 69% and 70% for the (R) and (S) phenyl rings, respectively. The results add additional evidence for the involvement of arene oxide in the oxidation of the pro (R) and pro (S) phenyls of phenytoin. The oxidation process of each ring could be mediated by independent enzyme systems, a rapid oxidative enzyme for the pro (S) phenyl and a slow oxidative enzyme for the pro (R) phenyl.

Chromatographic separation and photoelectrochemical detection of sodium nitroprusside and its degradative and metabolic products.

Ion-pair chromatography has been used for the separation of nitroprusside ion and its photochemical hydrolytic and metabolic products. Organic modifier and pH were adjusted for maximum separation of the ions. Methanol was selected as the organic modifier in a pH range 5-8 and tetrabutylammonium perchlorate was used as the ion-pairing reagent. Ions were detected with a photoelectrochemical detector as described by Krull. A modification of this procedure was used to detect nitroprusside ion in spiked serum samples.

Simultaneous spectrophotometric determination of amodiaquine-primaquine mixtures in dosage forms.

Using 0.1N hydrochloric acid as solvent, mixtures of amodiaquine and primaquine have been measured at 282 and 342 nm. The concentration of each can then be calculated by solving 2 simultaneous equations. Excellent recoveries from authentic samples were obtained and the method proved suitable for routine analysis.