M. M. Amer

Stability-indicating methods for the spectrophotometric determination of norfloxacin

Two spectrophotometric procedures for the selective determination of norfloxacin (NF) in the presence of its decarboxylated degradant are described. The first depends upon measurement of the pH-induced absorbance difference (delta A) of the drug solution between 0.1 N HCl and 0.1 N NaOH at 280 nm. The second involves chelation of the intact drug with iron (II) in acetate buffer solution (pH 5.7 +/- 0.1) to form a yellow-coloured chelate which absorbs at 358 nm. The two procedures are applied successfully for the determination of the intact drug both in pure form and in tablet form. The two methods retain their accuracy in the presence of up to 62% and 76% degradants, respectively.

Microcoated wire sensors for the determination of anticancer drugs cyclophosphamide and ifosphamide in the presence of their degradates.

The construction and electrochemical response characteristics of poly (vinyl chloride) and poly (vinyl chloride) carboxylate membrane sensors for the determination of cyclophosphamide and ifosphamide are described. Based on the formation of an ion-pair complex between the drug cation and sodium tetraphenylborate, two poly (vinyl chloride) sensors, namely a cyclophosphamide membrane sensor and ifosphamide membrane sensor were fabricated. They show a linear response for both drugs over the concentration range 10(-2)-10(-4) M with cationic slopes of 56 and 54.6 mV per concentration decade, for sensor 1 and sensor 2, respectively. Based on the interaction between the drug solution and the dissociated COOH groups in the poly (vinyl chloride) carboxylate, sensor 3 was fabricated. It shows a linear response for both drugs over the concentration range 10(-3)-10(-5) M with a cationic slope of 49.7 mV per concentration decade. The direct potentiometric determination of cyclophosphamide and ifosphamide in their pharmaceutical preparations using the proposed sensors gave average recoveries of 101.3+/-0.6, 100.8+/-10.7 and 102.0+/-11.0% for the sensors 1, 2 and 3, respectively, which compares reasonably well with the data obtained using the British Pharmacopoeial method (1993). Sensors 1 and 2 were also used to follow up the stability of the drugs studied in the presence of their degradates. These degradation products have no diverse effect on the responses of sensors 1 and 2.

Composition and stability constants of iron- and copper-oxytetracycline chelates

SummaryThe composition and stability constants of iron and copper oxytetracycline chelates are determined by spectrophotometric and pH-metric methods. The stepwise stability constants are logβ1 9.79, logβ2 7.08, logβ3 5.92 and logβ1 7.28 and logβ2 5.29 for iron and copper chelates, respectively. The thermodynamic parameters of these reactions and the site of chelation in oxytetracycline are also investigated. The reaction of iron(III) has been used for the spectrophotometric determination of oxytetracycline in some pharmaceutical preparations. Results with a coefficient of variation in the range of 1.6% and a mean recovery of 98.6% are obtained.ZusammenfassungSpektrophotometrische Methoden und pH-Messung ermöglichten die Bestimmung der im Titel angeführten Größen. Die Stabilitätskonstanten für die Eisen- bzw. Kupfer-Chelate sind: log/gb1 9,79; logβ2 7,08; logβ3 5,92; bzw. logβ1 7,28; logβ2 5,59. Die thermodynamischen Parameter dieser Reaktionen und die Art der Chelatbildung des Oxytetracyklin-Moleküls wurden ebenfalls untersucht. Die Reaktion mit Eisen(III) wurde für die Bestimmung von Oxytetracyklin verwendet. Ergebnisse mit einem Variationskoeffizienten 1,6% und einer mittleren Wiederfindungsrate von 98,6% wurden erzielt.

Stability-Indicating Method For The Determination Of N-Desmethyldiazepam And Simultaneous Determination Of Its Degradation Products

Abstract A simple, direct and sensitive spectrophotometric method for the determination of the intact N-desmethyldiazepam in the presence of its degradation products, 2-amino-5-chlorobenzophenone and glycine, is developed. The proposed procedure is based on direct measurement of the absorbance of its acidified methanolic solution at 361 nm. The procedure determines 8–56 mcg ml−1 of N-desmethyldiazepam with an accuracy of 100.2 ± 0.51%. The proposed procedure retains its accuracy in presence of up to 80% of the different degradation products. The procedure is applied successfully for the determination of N-desmethyldiazepam in bulk powder, tablets and drops. Simultaneous determination of the different degradation products in the presence of the parent drug is also described. Thus, 2-amino-5-chlorobenzophenone is determined by direct measurement of its methanolic solution at about 380 nm, with an accuracy of 100.4 ± 0.42%. Glycine is determined colorimetrically using ninhydrin reagent in presence of pyridin...

Analytical Study of Methorexate

Abstract Spectrophotometric, coloriaetric and differential pulse polarographic “DPP” techniques were adopted for microdetermination of methotrexate in pure form and in pharmaceutical preparations. The spectrophotometric method was based on measuring the light absorbance at 303 nm in 0.1 N NaCH. The colorimetric method was based on coupling the diazotised methotrexate with 8-hydroxy quinoline in alkaline medium and measuring the colour developed at 430 nm. The three proposed techniques were compared with the E.P. 1980. method. The DPP method was further used for methotrexste determination in presence of some biological fluids.

Spectrophotometric and Spectrofluorimetric Determination of Cyclophosphamide and Its Isomer Ifosphamide

Abstract Based on the condensation reaction between amino groups of either cyclophosphamide or ifosphamide with the carbonyl group of ninhydrin, giving coloured and fluorescent products, a spectrophotometric procedure for both drugs is suggested in the range from 30 to 90μg ml−1 at 564 nm, with accuracies of 100.6 ± 1.06% and 100.8 ± 1.02% for cyclophosphamide and ifosphamide, respectively. Also, a spectrophotometric procedure for both drugs is proposed in the range from 1.2 to 3.6 μg ml−1 at 465 nm and 485 nm for cyclophosphamide and ifosphamide, respectively, using 380 nm as an excitation wavelength for both drugs with accuracies of 100.4 ± 1.83% and 99.5 ± 1.64%, respectively. This condensation reaction, however, does not differentiate between the two isomeric drugs. Another new method is, therefore, suggested. It depends on the fact that the secondary amino group of ifosphamide is hindered electronically and sterically, while the nucleophilic amino group of cyclophosphamide reacts with the nitrosyl gr...

Spectrofluorimetric Method for the Determination of Cyclophosphamide and Ifosphamide

Abstract Cyclophosphamide and ifosphamide are determined by fluorescence reaction based on oxidation of cyclophosphamide or ifosphamide with sodium peroxide to give the perphosphorus compound. The perphosphous compound is allowed to oxidise indole to the highly fluorescent indoxyl, equivalent to cyclophosphamide or ifosphamide, which is determined spectrofluorimetry. Beers law is obeyed within concentrations from 5×10−5 - 2.5×10−4 mg/mL The suggested procedure has an accuracy of 99.9 ± 2.17 %. Application to some pharmaceutical preparations has shown no significant difference when compared with the B.P. (1988) method.

Stability-indicating method for the determination of clorazepate dipotassium-II. Via N-desmethyldiazepam and determination of its degradation products.

A spectrophotometric method for the determination of the intact clorazepate dipotassium in the presence of its degradation products is developed. It depends upon preliminary hydrolysis of clorazepate dipotassium-thus liberating its equivalent of N-desmethyldiazepam which is extracted, with benzene-methylene chloride (9:1). The extract is evaporated, the residue dissolved in methanol and its absorbance measured at about 315 nm. The procedure determines 0.4-1.6 mg of clorazepate dipotassium with an accuracy of 100.2+/-0.7%. The procedure is applied successfully for the determination of clorazepate dipotassium in bulk powder and in capsules; retaining its accuracy in the presence of up to 80% degradation. Determination of the different degradation products is also possible. Thus, N-desmethyl diazepam is determined after preliminary extraction with benzene-methylene chloride mixture, followed by TLC separation, 2-amino-5-chlorobenzophenone by directly applying the first derivative spectrophotometric technique, and glycine in the aqueous layer determined colorimetrically with ninhydrin reagent in the presence of pyridine.

Stability-indicating method for the determination of clorazepate dipotassium—I. Via its final degradation products

A sensitive spectrophotometric procedure is described for the determination of 1,4-benzodiazepine (clorazepate dipotassium) in the presence of its degradation products. The procedure is based on acid hydrolysis of clorazepate dipotassium to yield its final degradation products viz., 2-amino-5-chlorobenzophenone and glycine. The amino-chlorobenzophrenone is extracted from the neutralized hydrolysate with diethyl ether, the extract is evaporated, the residue is dissolved in methanol and its absorbance measured at about 240 nm or 380 nm. Glycine, left in the aqueous layer after etherial extraction of aminochlorobenzophenone, is treated with ninhydrin reagent in the presence of pyridine and the bluish violet colour formed is measured at about 560 nm. The suggested procedures determine 20-100 mg of clorazepate dipotassium via its degradation products aminochlorobenzophenone and glycine with mean accuracies of 100.0 +/- 0.5% at 560 nm, 100.2 +/- 0.6% at 380 nm and 99.8 +/- 0.5%. The suggested procedures are suitable for stability-testing of clorazepate dipotassium in bulk powder and in pharmaceutical preparations.

Effect of Some Precipitating and Complexing Agents on the Potential of an Ion-Selective Pb(II) - Electrode

Abstract The influence of some precipitating and complexing agents on the function of Pb(II)-sensitive electrode was studied. On the basis of the experimental findings, procedures were worked out for determining oxalate, phosphate, chromate, nitrilotriacetic acid (NTA), sodium diethyldithiocarbamate (NaDDC), and diethylenetetraamine penta-acetic acid (DTPA) with a standard Pb(II) solution as a titrant and a Pb(II), -sensitive electrode as a detector. The reverse titration of Pb(II), with any of these agents could also be done.