Abdel-Aziz M. Wahbi

Spectrophotometric determination of tranexamic acid with chloranil

Tranexamic acid is reacted with aqueous alcoholic chloranil, buffered at pH 9, to give a complex with maximum absorption at 346 nm and with an apparent molar absorptivity of 15.7 x 10(3) l.mole(-1).cm(-1). A(max) is linearly related to concentration over the range 2-10 mug ml . When applied to tablets labelled as containing 500 mg each, the mean found was 496 +/- 4 mg. The results were comparable with those of the traditional formol titration method for amino-acids.

Ratios of first-derivative maxima and compensated derivative absorption curves

General procedures are outlined for the detection of the presence of interferences during spectrophotometric analysis using first-derivative absorption spectra. These involve (i) ratios of first-derivative maxima, which are independent of concentration, and (ii) the compensated derivative curves. Thus, selecting two suitable maxima at λ1 and λ2, D11/D12, |D11–D12|/D11 and D1(corr.)1/|D11–D12| are used to reveal the shape of the interference curve and the possibility of eliminating its effect. These ratios are highly reproducible with coefficients of variation of less than 1%. The methods are illustrated by the determination of phenol in a pharmaceutical preparation. The results obtained were in good agreement with those of the official bromimetric method.

Colorimetric determination of piperazine with p-benzoquinone.

Piperazine and its salts are reacted with aqueous alcoholic p-benzoquinone, buffered at pH 5.4, to give a coloured product with maximum absorption at 516nm. The piperazine base has a molar absorptivity of 0.96 x 10(4)l.mole(-1).cm(-1) and Beers law is obeyed over the range 2-10 mug ml . When applied to three commercial preparations, the proposed method gave mean recoveries within 1% of those obtained by the official gravimetric method. The relative standard deviation was less than 1%.

Spectrophotometric and spectrofluorimetric determination of cycloserine with p-benzoquinone

Spectrophotometric and spectrofluorimetric methods are described for the determination of cycloserine. Both methods are based on the reaction of cycloserine in aqueous solution of pH 8.2 with p-benzoquinone. A fluorescent compound with an absorption maximum (and also an excitation maximum) at 381 nm is obtained. The complex has an apparent molar absorptivity of 4.76 × 103 l mol–1 cm–1 and Beers law is obeyed over the range 4–20 µg ml–1. The emission maximum of the complex is at 502 nm. The fluorescence intensity is linearly related to concentration over the range 0.04–0.2 µg ml–1. When applied to capsules labelled to contain 250 mg, the proposed methods gave mean recoveries of 100.97 ± 1.14 and 99.8 ± 1.13%, respectively.

Spectrophotometric Method of Determination for Cycloserine Using Chlornil

Abstract Cycloserine has been determined by a spectrophotometric method based on n → charge-transfer complex formation with chloranil. The method involves addition of cycloserine solution to chloranil reagent in borate buffer of pH 9; and heating at 65°C for 45 min. The complex formed exhibits absorption maximum of 348 nm; and Amax is linearly related to concentration over the range 2–8 μg/ml. The mean percentage found for the authentic sample is 100.32 ± 0.70. When applied to commercial capsules claimed to contain 250 mg each, the mean percentage found is 102.45 ± 1.05. These results have shown good agreement when compared with those obtained by the pharmacopoeial (B.P.) methods.

Spectrophotometric determination of vitamin A in oily capsules using first derivative curves

The first derivative curve (D1) of the absorption spectrum of vitamin A acetate in cyclohexane possesses a trough (D11) at 348 nm and a maximum (D12) at 306 nm. D11, D12, and delta D1 (= D11 - D12) are linearly related to concentration over a range of 5-25 i.u. ml-1. When a tangent is drawn between D1 at 400 nm and D1, at 306 nm, the amplitude at 348 nm (D1 corr.) is linearly related to concentration. Ratios of magnitude of D11/magnitude of D12 and D1(corr.)/magnitude of D1 are independent of concentration, and have been used to reveal the presence of interferences in the D1 curves of vitamin A in oily capsules. Vitamin A in two oily preparations has been assayed using delta D1 and D1(corr.). The potency found was within +/- 2% from that obtained by using the B.P. method. The method is rapid, precise and accurate.

Spectrophotometric and fluorimetric determination of nomifensine maleate

Three methods have been developed for the determination of nomifensine maleate alone and in capsules: a spectrophotometric, an iodine charge-transfer, and a spectrofluorimetric method. All three give linear calibration graphs, over the ranges 20-100, 1-5 and 0.1-0.5 microg/ml, respectively, with coefficients of variation of 0.8, 1.3 and 1.3%, respectively.

Colorimetric and Polarographic Methods of Analysis for Prenalterol Hydrochloride

Abstract Two proposed methods have been described for the determination of prenalterol hydrochloride in acetate buffer (pH=4.1) as authentic material and in tablets form using a (i) colorimetric method based on reduction of ferric iron by prenalterol hydrochloride and subsequent measurement at 511 nm of the red color obtained by the treatment of the resultant ferrous iron with 1, 10-orthophenanthroline, (ii) a differential pulse polarographic method based on nitrosation with 0.1 M NaNO2/dil. HC1 and consequent recording of the differential pulse polarogram. The differential polarogram was obtained under constant amplitude pulses of 50 mV (DP 50) superimposed on a linearly increasing DC-voltage ramp. The peak height (h), of the polarogram was measured at the peak potential of -0.2V on the dropping mercury electrode (DME) versus Ag/AgCl reference electrode. The linearity ranges observed are 0.6μgfml to 6.0μg/ml and 2μg/ml to 12μg/ml, respectively. The mean percentage recoveries for an authentic sample are 9...

Ratios of Fourier to orthogonal function coefficients: spectrophotometric determination of tetraenes in amphotericin B

Ratios of Fourier function coefficients to their analogous orthogonal function coefficients are proposed as purity indices during spectrophotometric analysis. Hence, a1/p2(where a1= coefficient of cosx and p2 is the coefficient of P2) calculated for a set of absorbances is independent of concentration and is sensitive to the presence of interferents. The concentration of tetraenes in amphotericin B has been determined by this ratio, calculated from absorbances measured at 6-nm intervals from 264 to 294 nm.

First Derivative Spectrophotometric Determination of Phenytoin

Abstract The first derivative curve (D1) of absorption spectrum of Phenytoin in buffer pH 10 develos negative peaks at 244, 263 and 270 nm. D1 at 244 nm was found linearly related to concentration over a range 0.4 − 1.4 mg per 100 ml and highly reproducible (C.V. %=0.62). Tablets and capsules have been analyzed using D1 at 244 nm and the mean percentage found were 99.7 ± 0.81 and 103.3 ± 0.44, respectively. The B.P. method gave 100.9 and 103.8 %, respectively.