Basilio Morelli

Derivative spectrophotometry in the analysis of mixtures of cefotaxime sodium and cefadroxil monohydrate.

Derivative spectrophotometry (ratio-spectra 1st- and 2nd-derivative and zero-crossing 2nd-derivative techniques) was applied for the determination of some cephalosporins in two component mixtures. Cefotaxime sodium salt (C(16)H(16)O(7)N(5)S(2)Na) and cefadroxil monohydrate (C(16)H(17)N(3)O(5)S.H(2)O) were examined. In all procedures, the calibration plots are linear up to 43 microg/ml of each antibiotic, with r ranging from 0.9997 to 0.9999. In the ratio-spectra method, the measurements were taken at 239.5 and 291.5 nm (cefotaxime, 1st-derivative), 238 and 283 nm (cefadroxil, 1st-derivative), 284 and 303 nm (cefotaxime, 2nd-derivative), and 229.5 and 245.5 nm (cefadroxil, 2nd-derivative). Detection limits at P=0.05 level of significance, calculated by a statistical treatment of calibration data, ranged from 0.15 to 0.58 microg/ml. LOD and LOQ ranged, respectively, from 0.19 to 0.51 and from 0.63 to 1.70 microg/ml. By the zero-crossing 2nd-derivative method, lines of regression are linear at 257 and 279 nm (cefotaxime) and 242 and 296 nm (cefadroxil). Detection limits from 0.28 to 0.51 microg/ml. LOD and LOQ from 0.27 to 0.41 and from 0.90 to 1.37 microg/ml, respectively. All the samples were tested for stability in solution and in the course of actual analysis, up to 80 h from their preparation. The developed derivative spectrophotometric methods were applied to synthetic mixtures and the RSD values ranged between 0.05 and 1.35% (ratio-spectra technique) and 0.01 and 1.07% (zero-crossing technique). The methods were also applied to vials and tablets for these drugs. The recoveries obtained were between 100.9 and 102.4% (ratio-spectra) and between 99.8 and 102.0% (zero-crossing). The procedures are simple, rapid, and did not require any preliminary separation or treatment of the samples. Instrumentation commonly available was utilised. The cephalosporins analysed are frequently used antibiotics of relevant clinical and pharmacological importance; hence this work would be of interest for the readers of journals devoted to pharmaceutical and biomedical analysis.

Spectrophotometric Determination of Cephalosporins in Pure Form and in Pharmaceutical Preparations

Abstract A spectrophotometric determination is described for cephalosporins, offering adequate sensitivity and good precision. The procedure applies successfully to a wide variety of cephalosporins, also in pharmaceutical preparations: cephalothin, cefacetrile, cephapirin, cefotaxime, ceftizoxime, cephaloridine, cefazolin, cefamandole nafate, cephalexin, cefadroxil, cefoxitin and cefuroxime. The method employs a reaction with ammonium molybdate in sulphuric acid medium. The antibiotic is heated at 91.5°C for 15 min and the absorbance of the coloured product is measured at 670 nm against a reagent blank treated similarly. Beers law is obeyed up to 125 to 150 μg of cephalosporin in the 5-ml final solution. The effect of reagent concentration and reaction conditions are discussed.

Determination of Mixtures of Cephacetrile and Ceftezole in a Pure form and Injections, by ‘Zero ‐ Crossing’ Derivative Spectrophotometry

Abstract A simple and sensitive procedure for the simultaneous determination of cephacetrile and ceftezole in a mixture is presented. First and second derivative spectrophotometry, with a ‘zero - crossing’ technique of measurement, has been used. The methods give linear calibration graphs, with zero intercept on y-axis, for up to 36 μg/ml of cephalosporins. Detection limits of cephacetrile and ceftezole, at p=0.05 level of significance, were calculated to be 0.39 and 0.46 μg/ml in the first derivative mode, and 0.26 and 0.19 μg/ml in the second derivative mode, respectively. The method can be profitably applied to the quantitation of these drugs in injectable dosage forms.

Spectrophotometric assay for chloramphenicol and some derivatives in the pure form and in formulations

A new analytical method for chloramphenicol and its derivatives, chloramphenicol succinate sodium and D-(-)-threo-2-amino-L-[p-nitrophenyl]-1,3-propanediol (chloramphenicol base) in the pure state or in pharmaceutical preparations, is described. The method is based on measuring the blue colour produced by the interaction of ammonium molybdate with the products of the alkaline hydrolysis of the drugs. There are certain advantages of simplicity and sensitivity over current methods. The Beers law limits, effects of temperature, acidity and reagent concentration, and statistical analysis of experimental results are reported.

Determination of ternary mixtures of antibiotics, by ratio-spectra zero-crossing first- and third-derivative spectrophotometry☆

The ratio-spectra zero-crossing first- and third-derivative spectrophotometry have been used for determining ternary mixtures of penicillin-G sodium, penicillin-G procain and dihydrostreptomycin sulphate salts. The procedures are accurate, nondestructive and do not require resolutions of equations. In both methods, calibration graphs are linear, with zero-intercept, up to 30 micrograms ml-1 of penicillin-G sodium and penicillin-G procain, and up to 42 micrograms ml-1 of dihydrostreptomycin sulphate. r = 0.9999 in each instance. Working wavelengths, 218.5, 211 and 236 nm, respectively, in the first-derivative mode, and 222.5, 311.5 and 242 nm in the third-derivative mode. Detection limits for each drug at p = 0.01 level of significance were calculated to be 0.058, 0.010 and 0.014 micrograms ml-1 and 0.14, 0.012 and 0.34 micrograms ml-1, in the first- and third-derivative methods, respectively. Both methods apply favorably to either laboratory mixtures or commercial injections.

Determination of binary mixtures of analgesic and spasmolytic drugs in pure and dosage forms by derivative spectrophotometry.

Binary mixtures of dipyrone and pitophenone hydrochloride are assayed by zero-crossing second- and third-derivative spectrophotometry and by ratio-spectra first- and second-derivative spectrophotometry. In the first method, calibration plots are linear at 266.5 and 302.5 nm (dipyrone, second derivative), and 257 and 286 nm (pitophenone second derivative) and 242 and 278.3 nm (dipyrone third derivative), and 228.5 and 300 nm (pitophenone, third-derivative). By the second method, lines of regression are linear at 235 and 262 nm (dipyrone, first derivative), and 229.5 and 288.5 nm (pitophenone, first-derivative), and 249.7 and 268 nm (dipyrone, second derivative), and 280.5 and 300 nm (pitophenone, second-derivative). In all methods calibration curves follow the Beers law up to 40 microg/ml of each drug. LOD and LOQ values were calculated. The developed derivative spectrophotometric methods were applied to laboratory mixtures and to vials for these drugs. The procedures are simple, rapid, and did not require any preliminary separation or treatment of the samples.

Spectrophotometric determination of paracetamol in pure form and in tablets

A spectrophotometric method is proposed for the determination of paracetamol in pure form and in tablets. The method depends on reaction of the drug with ammonium molybdate in strongly acidic medium to produce molybdenum blue. Effects of variables such as temperature, heating time, acidity and reagent concentration have been evaluated to permit selection of the most advantageous technique. Beers law was followed for concentrations of up to 6 micrograms ml-1 of paracetamol and the detection limit (p = 0.05) was 0.10 microgram ml-1. The molar absorptivity at 670 nm was 2.6 x 10(4) l mol-1 cm-1 and the relevant Sandells sensitivity of the reaction was 0.0059 microgram cm-2 per 0.001 absorbance unit. Statistical analysis of the results and comparison with results by the BP method of analysis are also reported.

Determination of Penicillins in pure form and in Pharmaceuticals

Abstract A rapid and convenient method is described for the determination of thirteen commercially available penicillins: methicillin Na, oxacillin Na, cloxacillin Na, dicloxacillin Na, nafcillin Na, ampicillin Na, amoxicillin, carbenicillin Na, penicillin-G Na, penicillin-G procain salt, penicillin-G benzathine salt, phenoxymethylpenicillinic acid K and phenoxymethylpenicillinic acid benzyl ester sulphoxide. Penicillins are esthted spectrophotowtrically, by oxidizing them under strongly acidic conditions, by means of an excessive quantity of amnonium vanadate. The mixture is heated at 180°C for 15 min and the absorbance of the colour developed is measured at 760 nm against a blank. Beers law is followed for up to 120 μg/ml of antibiotic. The method is applied to the mlysis of various pharmaeutical preparations for these drugs.

Application of the zero-crossing derivative spectrophotometry to the analysis of mixtures of cefoperazone and cefamandole nafate in pure and pharmaceutical dosage forms

Abstract ‘Zero - crossing’ first and second derivative spectrophotometry has been employed for the quantitation of mixtures of cefoperazone Na and cefamandole nafate. Beers law holds for up to 44 ug/ml of each cephalosporin, in both derivative modes. The method has been applied to the recovery of these antibiotics in mixtures of injectable dosage forms.

Determination of Ternary Mixtures of Vitamins by Ratio-Spectra Zero-Crossing Derivative Spectrophotometry

Abstract The ratio-spectra zero-crossing first and third derivative spectrophotometry have been used for determining ternary mixtures of Vitamin 86, Vitamin B1 and Vitamin B12. The procedures are accurate, nondestructive and do not require solving of equations. In both methods, calibration graphs are linear, with zero-intercept, up to 48 μg/ml of Vitamin B6, 64 μg/ml of Vitamin B1 and 60 μg/ml of Vitamin B12. Correlation coefficients range from 0.9999 to 1.0000. Working wavelengths, 311, 272.5 and 215.5 nm, respectively, in the 1st-derivative mode and 300.5, 271.5 and 365 nm in the 3rd-derivative mode. Detection limits for each drug at p=0.01 level of significance were calculated to be 0.002, 0.009 and 0.004 μg/ml and 0.002, 0.004 and 0.001 μg/ml, in the first and third-derivative methods, respectively. Both methods apply favourably to either synthetic mixtures or commercial injections for these drugs. An exhaustive statistical treatment of the experimental findings was performed to confirm the validity o...