Zero-crossing derivative spectrophotometry for the determination of mixtures of cephaloridine and cephalothin in pure and dosage forms

Multicomponent spectrophotometric determination of a ternary mixture of widely-prescribed cardiovascular drugs by four different methods

Four accurate, green, uncomplicated, and fast spectrophotometric procedures were established for the purpose of resolving as well as quantifying a ternary combination prescribed for cardiovascular patients, such as aspirin, atorvastatin, and ramipril. Method (A) is based on the first derivative zero-crossing spectrophotometry for the determination of aspirin and atorvastatin at 247.4 nm and 302.6 nm, respectively. Ramipril was determined using the second derivative at 211 nm. Method (B) depends on the ratio spectra first derivative (RDS) where the absorption spectrum of the ternary combination was divided by the spectrum of one of the analytes. When treated similarly, the concentrations of the other two analytes were measured using their corresponding calibration graphs. For the determination of ASP and RAM, ATR was used as a divisor with a concentration of 26 µg/mL, and the RDS values at 272.0 and 225.8 nm, respectively, were plotted against the ASP and RAM concentrations. Using 40 µg/mL ASP as a divisor, ATR was analyzed, and the RDS values at 295 nm were plotted versus the ATR concentration. Method (C) is based on the double divisor-ratio spectra derivative technique. In this technique, the derivative of the ratio spectrum is computed by dividing the absorption spectra of the studied combination by the standard spectrum of abinary combination of two of the three analytes being studied. The concentrations of the three analytes in the mixture were assayed by determining the absorbance either at the positive or the negative amplitude. For the determination of ASP, ATR, and RAM, the wavelengths used were 244, 295, and 220 nm, respectively. Method (D) was a hybrid double divisor-ratio spectra technique based on convolving the double divisor-ratio spectra with trigonometric Fourier functions. The magnitudes of the Fourier function coefficients at either maximum or minimum points were correlated to the concentration of each drug in the mixture. The specificity of the suggested methods was tested by analyzing synthetic laboratory-prepared combinations and laboratory-made tablets. Furthermore, the accuracy and precision were ensured by statistically comparing the obtained results with those obtained from comparison method using Bartlett's Test for Equality of Variances and ANOVA test.

Derivative spectrophotometric analysis of benzophenone (as an impurity) in phenytoin

Three simple and rapid spectrophotometric methods were developed for detection and trace determination of benzophenone (the main impurity) in phenytoin bulk powder and pharmaceutical formulations. The first method, zero-crossing first derivative spectrophotometry, depends on measuring the first derivative trough values at 257.6 nm for benzophenone. The second method, zero-crossing third derivative spectrophotometry, depends on measuring the third derivative peak values at 263.2 nm. The third method, ratio first derivative spectrophotometry, depends on measuring the peak amplitudes of the first derivative of the ratio spectra (the spectra of benzophenone divided by the spectrum of 5.0 μg/mL phenytoin solution) at 272 nm. The calibration graphs were linear over the range of 1-10 μg/mL. The detection limits of the first and the third derivative methods were found to be 0.04 μg/mL and 0.11 μg/mL and the quantitation limits were 0.13 μg/mL and 0.34 μg/mL, respectively, while for the ratio derivative method, the detection limit was 0.06 μg/mL and the quantitation limit was 0.18 μg/mL. The proposed methods were applied successfully to the assay of the studied drug in phenytoin bulk powder and certain pharmaceutical preparations. The results were statistically compared to those obtained using a polarographic method and were found to be in good agreement.

Validated stability-indicating derivative and derivative ratio methods for the determination of some drugs used to alleviate respiratory tract disorders and their degradation products

Derivative and derivative ratio methods are presented for the determination of butamirate citrate, formoterol fumarate, montelukast sodium, and sodium cromoglycate. Using the second derivative ultraviolet (UV) spectrophotometry, butamirate citrate and formoterol fumarate were determined by measuring the peak amplitude at 260.4 and 261.8 nm, respectively, without any interference of their degradation products. Butamirate citrate degradation product, 2-phenyl butyric acid, was determined by the measurement of its second derivative amplitude at 246.7 nm where butamirate citrate displays zero crossing. Formoterol fumarate degradation product, desformyl derivative, could be evaluated through the use of the first derivative at peak amplitude of 264.8 nm where interference of formoterol fumarate is negligible. In the first mode, the zero-crossing technique was applied at 305 nm for the determination of montelukast sodium in the presence of its photodegradation product, cis-isomer. The derivative of ratio spectra of montelukast sodium and its cis- isomer were used to determine both isomers using the first derivative of the ratio spectra by measuring the amplitudes of the trough at 305 nm and the peak at 308 nm, respectively. The later technique was also used for the determination of a ternary mixture of sodium cromoglycate and its two degradation products using zero-crossing method. In the derivative ratio spectra of the ternary mixture, trough depths were measured at 271.6, 302.8 and 302.2 nm, using the second, the first, and the second mode to evaluate sodium cromoglycate, degradation product (1) and degradation product (2), respectively. All the methods were applied successfully to the pharmaceutical preparation and were validated according to ICH guidelines.

Electrochemical determination of Cephalothin antibiotic by adsorptive stripping voltammetric technique

A sensitive and reliable stripping voltammetric method was developed to determine Cephalothin antibiotic drug. This method is based on the adsorptive accumulation of the drug at a hanging mercury drop electrode and then a negative sweep was initiated, which yield a well defined cathodic peak at -625 mV versus Ag/AgCl reference electrode. To achieve high sensitivity, various experimental and instrumental variables were investigated such as supporting electrolyte, pH, accumulation time and potential, drug concentration, scan rate, convection rate and working electrode area. The monitored adsorptive current was directly proportional to the concentration of Cephalothin and it shows a linear response in the range from 4 x 10(-7) to 1.2 x 10(-6) mol l(-1) (correlation coefficient=0.9995) and the detection limit (S/N=3) is 3.3 x 10(-9) mol l(-1) at an accumulation time of 3 min. The developed AdSV procedure shows a good reproducibility, the relative standard deviation R.S.D.% (n=10) at a concentration level of 5 x 10(-7) mol l(-1) was 0.94%. Possible interferences by other pharmaceutical drugs and surfactants have been also evaluated. The applicability of this approach was illustrated by the determination of Cephalothin in pharmaceutical preparation and biological fluids such as serum and urine.

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 Beer's 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.

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.

Application of derivative-differential UV spectrophotometry and ratio derivative spectrophotometric determination of mephenoxalone and acetaminophen in combined tablet preparation

A method is presented for the direct determination of mephenoxalone and acetaminophen in combined pharmaceutical dosage forms without prior separation. The first method, derivative-differential spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first order (deltaD1) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 289.6 and 252.6 nm respectively. The second method is based on ratio derivative spectrophotometry. The amplitudes in the first derivative of the ratio spectra at 233.5 and 288.9 nm were selected to determine mephenoxalone and acetaminophen in the mixture. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow one to obtain precise and accurate results.

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.

Comparison of three new spectrophotometric methods for simultaneous determination of aspirin and salicylic acid in tablets without separation of pharmaceutical excipients

Simultaneous analysis of aspirin (ASA) and salicylic acid (SA) in pharmaceutical tablet preparations was performed by two multicomponent UV-spectrophotometric methods utilizing principal component regression and classical least square algorithm. Additionally, an assay procedure based on second-derivative spectroscopy was developed. The analysis was performed in turbid solutions without separation of interfering excipients. The range, as determined by the second-derivative methods, was 0.2 to 103.2 micrograms/mL for ASA and 0.07 to 44.5 micrograms/mL for SA. Sensitivity for determination of SA was 0.004% of ASA content for the second-derivative method and 0.2% of ASA content for both multicomponent methods. The methods were applied to laboratory mixtures and commercial tablet formulations containing ASA and SA. The advantage of the second-derivative method in determining small amounts of SA in commercial tablet preparations is shown in comparison with a conventional HPLC method. All UV-spectrophotometric methods are rapid, accurate, and reproducible.

Rapid simultaneous determination of tryptophan and tyrosine in synthetic peptides by derivative spectroscopy

A method for the simultaneous quantitative determination of tryptophan and tyrosine in synthetic peptides by second-order derivative diode-array spectroscopy is reported. The method does not require hydrolysis of the peptides or a derivatization reaction; the sample is dissolved in 0.1 N NaOH and directly scanned between 262 and 264 nm to detect tyrosine and between 304 and 306 nm to detect tryptophan. From these results the peptide content of the synthetic sample can be easily calculated in a very simple and fast way. The results obtained by the described method with several peptides are compared with those obtained by classical high-performance liquid chromatographic analysis of amino acids after peptide hydrolysis. A very good correlation was found both for the tryptophan/tyrosine molar ratio and the peptide content.

Simultaneous derivative spectrophotometric determination of aztreonam and L-arginine in injections

Mixtures of aztreonam, 2S-[2 alpha,3 beta(Z)]-2-[[[1-(2-amino-4-thiazolyl-2- [(2-methyl-4-oxo-1-sulfo-3-azetidinyl) amino]-2-oxo- ethylidine]amino]oxy]-2-methyl-propanoic acid, and L-arginine are assayed by peak-to-baseline, peak-to-peak, and zero-crossing second-derivative spectrophotometry. Aztreonam is the first of a new class of beta-lactam antibiotics (i.e., the mono-bactam antibiotics, highly effective against aerobic gram-negative bacteria). Beer's law is followed for up to 31 micrograms/mL of aztreonam and L-arginine in the presence of one another. Detection limits at the p = 0.05 level of significance range from 0.11 to 0.37 micrograms/mL. The method was successfully applied to laboratory mixtures and commercial injections containing these substances.

Second-derivative spectrophotometric assay of mixtures of dicloxacillin sodium and ampicillin sodium in pharmaceuticals

'Zero-crossing' derivative spectrophotometry has been used for determining binary mixtures of dicloxacillin Na and ampicillin Na, which are penicillins with closely overlapping absorption spectra. The procedure is rapid, simple, nondestructive, and does not require solutions of equations. Calibration graphs are linear (r = 0.9999), with a zero intercept for up to 60 micrograms/mL of each antibiotic. Detection limits at the p = 0.05 level of significance were calculated to be 0.29 and 0.31 microgram/mL of dicloxacillin Na and ampicillin Na, respectively. The method was successfully applied to the assay of commercial injections and capsules for these drugs.