Simultaneous determination of cyproterone acetate and ethinylestradiol in tablets by derivative spectrophotometry

Derivative spectrophotometry offers a useful approach for the analysis of drugs in multi-component mixtures. In this study a third-derivative spectrophotometric method was used for simultaneous determination of cyproterone acetate and ethinylestradiol using the zero-crossing technique. The measurements were carried out at wavelengths of 316 and 226 nm for cyproterone acetate and ethinylestradiol respectively. The method was found to be linear (r2>0.999) in the range of 0.5-6 mg/100 ml for cyproterone acetate in the presence of 35 microg/100 ml ethinylestsradiol at 316 nm. The same linear correlation (r2>0.999) was obtained in the range of 10-80 microg/100 ml of ethinylestradiol in the presence of 2 mg/100 ml of cyproterone acetate at 226 nm. The limit of determination was 0.5 mg/100 ml and 10 microg/100 ml for cyproterone acetate and ethinylestradiol respectively. The method was successfully applied for simultaneous determination of cyproterone acetate and ethinylestradiol in pharmaceutical preparations without any interferences from excipients.     

Spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in bulk and pharmaceutical preparation

Two new, sensitive and selective spectrofluorimetric and spectrophotometric methods have been developed for the determination of the gamma-amino-n-butyric acid derivative pregabalin (PGB) in bulk drug and capsule. Pregabalin, as a primary amine compound, reacts with 7-chloro-4-nitrobenzofurazon (NBD-Cl) which is a highly sensitive fluorogenic and chromogenic reagent used in many investigations. According to this fact, spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in capsules were developed for the first time. The relation between the absorbance at 460 nm and the concentration is rectilinear over the range 0.5-7.0 microg mL(-1). The reaction product was also measured spectrofluorimetrically at 558 nm after excitation at 460 nm. The fluorescence intensity was directly proportional to the concentration over the range 40-400 ng mL(-1). The method was applied successfully to the determination of this drug in pharmaceutical dosage form. The mean recovery for the commercial capsules was 99.93% and 99.96% for spectrophotometric and spectrofluorimetric study, respectively. The suggested procedures could be used for the determination of PGB in pure and capsules being sensitive, simple and selective.     

Simultaneous determination of manganese and zinc in mixtures using first- and second-derivative spectrophotometry

A new direct spectrophotometric determination of manganese with 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin,NAZA) is reported. Absorption maximum, molar absorptivity and Sandell's sensitivity of 1:2 (M:L) complex are 695 nm, 1.88x10(4) l mol(-1) cm(-1) and 2.92 ng cm(-2), respectively. A linear calibration graph is obtained up to a concentration of 7.2 mug ml(-1) of manganese. The optimum range for determination (Ringbom) is between 0.20 and 6.8 mug ml(-1). A rapid method for simultaneous determination of manganese and zinc in their mixture using derivative spectra is described. The range 0.28-5.6 mug ml(-1) manganese could be determined in the presence of 0.33-6.8 mug ml(-1) zinc and vice versa. The developed method was applied to the simultaneous spectrophotometric determination of manganese and zinc in some synthetic mixtures and was found to give satisfactory results.     

The analysis of the zero-order and the second derivative spectra of retinol acetate, tocopherol acetate and coenzyme Q10 and estimation of their analytical usefulness for their simultaneous determination in synthetic mixtures and pharmaceuticals

The aim of the present work was to develop a simple and rapid method of retinol acetate, tocopherol acetate and coenzyme Q(10) determination in pharmaceuticals without involving any preparation operations like separation or masking. The values of second derivative amplitude at 212 nm for tocopherol, 351 nm for retinol and 222 nm for coenzyme were used for construction of calibration graphs. Beer's law is obeyed in the concentration range 0.5-20, 0.5-7.5 and 0.5-30 microg ml(-1) for retinol acetate, tocopherol acetate and coenzyme, respectively. The elaborated procedures were successfully applied to the simultaneous determination of studied compounds in their binary synthetic mixtures and in commercial preparations with high reliability and repeatability. Spectral properties of retinol acetate allows to determine its contents in ternary mixture which includes Vitamin E and coenzyme Q(10).     

New methods for determination of cinnarizine in mixture with piracetam by spectrodensitometry, spectrophotometry, and liquid chromatography

Four new methods were developed and validated for the determination of cinnarizine HCl in its binary mixture with piracetam in pure and pharmaceutical preparations. The first one was a densitometric analysis that provides a simple and rapid method for the separation and quantification of cinnarizine HCI. The method depends on the quantitative densitometric evaluation of thin-layer chromatograms of cinnarizine HCI at 252 nm over concentration range of 1-6 microg/spot, with a mean accuracy of 100.05 +/- 0.91%. The second method was determination of the drug using a colorimetric method that utilizes the reaction of 3-methyl-benzothiazolin-2-one in the presence of FeCl3 as an oxidant. The green color of the resulting product was measured at 630 nm over concentration range 10-40 microg/mL, with a mean accuracy of 100.10 +/- 1.13%. The third method was a direct spectrophotometric determination of cinnarizine HCI at 252 nm over the concentration range 7-20 microg/mL, while piracetam was determined by derivative ratio spectrophotometry at 221.6 nm over concentration range 5-30 microg/mL, with a mean accuracy of 100.14 +/- 0.79 and 100.26 +/- 1.24% for cinnarizine HCI and piracetam, respectively. The last method was a liquid chromatography analysis of both cinnarizine HCI and piracetam, depending on quantitative evaluation of chromatograms of cinnarizine HCI and piracetam at 252 and 212 nm, respectively, over the concentration range 10-200 microg/mL for cinnarizine HCI and 20-500 microg/mL for piracetam, with a mean accuracy of 100.03 +/- 0.89 and 100.40 +/- 0.94% for cinnarizine HCI and piracetam, respectively. The proposed procedures were checked using laboratory-prepared mixtures and successfully applied for the analysis of their pharmaceutical preparations. The validity of the proposed procedures was further assessed by applying the standard addition technique. Recoveries were quantitative, and the results obtained agreed with those obtained by other reported methods.     

Spectrophotometric and spectrodensitometric determination of paracetamol and drotaverine HCl in combination

Thin-layer chromatography, first derivative, ratio spectra derivative spectrophotometry and Vierordt's method have been developed for the simultaneous determination of paracetamol and drotaverine HCl. TLC densitometric method depends on the difference in Rf values using ethyl acetate:methanol:ammonia (100:1:5 v/v/v) as a mobile phase. The spots of the two drugs were scanned at 249 and 308 nm over concentration ranges of 60-1200 microg/ml and 20-400 microg/ml with mean percentage recovery 100.11%+/-1.91 and 100.15%+/-1.87, respectively. The first derivative spectrophotometric method deals with the measurements at zero-crossing points 259 and 325 nm with mean percentage recovery 99.25%+/-1.08 and 99.45%+/-1.14, respectively. The ratio spectra first derivative technique was used at 246 and 305 nm with mean percentage recovery 99.75%+/-1.93 and 99.08%+/-1.22, respectively. Beer's law for first derivative and ratio spectra derivative methods was obeyed in the concentration range 0.8-12.8 and 0.4-6.4 microg/ml of paracetamol and drotaverine HCl, respectively. Vierordt's method was applied to over come the overlapping of paracetamol and drotaverine HCl in zero-order spectra in concentration range 2-26 and 2-40 microg/ml respectively. The suggested methods were successfully applied for the analysis of the two drugs in laboratory prepared mixtures and their pharmaceutical formulation. The validity of the methods was assessed by applying the standard addition technique. The obtained results were statistically agreed with those obtained by the reported method.     

Highly sensitive and selective spectrophotometric and spectrofluorimetric methods for the determination of ropinirole hydrochloride in tablets

Three sensitive, selective, accurate spectrophotometric and spectrofluorimetric methods have been developed for the determination of ropinirole hydrochloride in tablets. The first method was based on measuring the absorbance of drug solution in methanol at 250 nm. The Beer's law was obeyed in the concentration range 2.5-24 microg ml(-1). The second method was based on the charge transfer reaction of drug, as n-electron donor with 7,7,8,8-tetracyanoquinodimethane (TCNQ), as pi-acceptor in acetonitrile to give radical anions that are measured at 842 nm. The Beer's law was obeyed in the concentration range 0.6-8 microg ml(-1). The third method was based on derivatization reaction with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in borate buffer of pH 8.5 followed by measuring the fluorescence intensity at 525 nm with excitation at 464 nm in chloroform. Beer's law was obeyed in the concentration range 0.01-1.3 microg ml(-1). The derivatization reaction product of drug with NBD-Cl was characterized by IR, 1H NMR and mass spectroscopy. The developed methods were validated. The following analytical parameters were investigated: the molar absorptivity (epsilon), limit of detection (LOD, microg ml(-1)) and limit of quantitation (LOQ, microg ml(-1)), precision, accuracy, recovery, and Sandell's sensitivity. Selectivity was validated by subjecting stock solution of ropinirole to acidic, basic, oxidative, and thermal degradation. No interference was observed from common excipients present in formulations. The proposed methods were successfully applied for determination of drug in tablets. The results of these proposed methods were compared with each other statistically.     

A rapid derivative spectrophotometric method for simultaneous determination of naphazoline and antazoline in eye drops

A zero-crossing first-derivative spectrophotometric method is applied for the simultaneous determination of naphazoline hydrochloride and antazoline phosphate in eye drops. The measurements were carried out at wavelengths of 225 and 252 nm for naphazoline hydrochloride and antazoline phosphate, respectively. The method was found to be linear (r2>0.999) in the range of 0.2-1 microg/ml for naphazoline hydrochloride in the presence of 5 microg/ml antazoline phosphate at 225 nm. The same linear correlation (r2>0.999) was obtained in the range of 1-10 microg/ml of antazoline phosphate in the presence of 0.5 microg/ml of naphazoline hydrochloride at 252 nm. The limit of determination was 0.2 microg/ml and 1 microg/ml for naphazoline hydrochloride and antazoline phosphate, respectively. The method was successfully used for simultaneous analysis of naphazoline hydrochloride and antazoline phosphate in eye drops without any interference from excipients and prior separation before analysis.     

Simultaneous determination of gallium and indium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in cationic micellar medium using derivative spectrophotometry.

A new derivative spectrophotometric method for rapid and selective trace analysis of Ga3+ and In3+ and for their simultaneous determination using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a cationic micellar medium is reported. Molar absorptivity and Sandell's sensitivity of 1:1 Ga+ and In3+ complexes at their lambda(max) 553 nm and 558 nm are: 7.22 x 10(4) l mol(-1) cm(-1) and 5.85 x 10(4) l mol(-1) cm(-1), and 0.96 ng cm(-2) and 1.96 ng cm(-2), respectively. Linearity is observed in the concentration range 0.023-0.700 microg ml(-1) for gallium and 0.076-1.52 microg ml(-1) for indium; IUPAC detection limit is 0.012 and 0.035 ng ml(-1), respectively. These metal ions interfere with the determination of each other. However, 0.07-0.70 microg ml(-1) Ga3+ and 0.115-1.150 microg ml(-1) In3+ could be determined simultaneously when present together by the derivative method without any prior separation. The proposed procedures have been successfully applied for the individual and simultaneous determination of gallium and indium in synthetic binary mixtures, standard reference materials and environmental samples.     

Simultaneous determination of zirconium and molybdenum by first-derivative spectrophotometry.

A first-derivative spectrophotometric method for the simultaneous determination of Zr and Mo with Alizarin Red S is described. Measurements were made at the zero-crossing wavelengths at 490.5 nm for Zr and 446.0 nm for Mo. The calibration graphs were linear at 0.5-20 and 0.5-13.0 microg ml(-1) for Zr and Mo, respectively. The possible interfering effects of various ions were studied. Only iron was interfered in this system. The validity of the method was examined by using some mixtures of Mo and Zr. The method was applied in different matrix in both presence and absence of some foreign metal ions.     

Simultaneous quantitative resolution of atorvastatin calcium and fenofibrate in pharmaceutical preparation by using derivative ratio spectrophotometry and chemometric calibrations.

In the present work, five different spectrophotometric techniques for simultaneous determination of formulations containing atorvastatin calcium (ATOR) and fenofibrate (FENO) in various combinations are described. In ratio spectra derivative spectrophotometry, analytical signals were measured at wavelengths corresponding to either maximums or minimums for both drugs in first derivative spectra of ratio spectra obtained by using either spectrum as divisor. For the remaining four methods using chemometric techniques, namely, classical least squares (CLS), inverse least squares (ILS), principal component regression (PCR) and partial least squares (PLS), the calibrations were constructed by using the absorption data matrix corresponding to the concentration data matrix, with measurements in the range of 231 - 310 nm (Deltalambda = 1 nm) in their zero-order spectra. The linearity range was found to be 4 - 22 and 2 - 20 microg/ml for ATOR and FENO, respectively. The validity of the proposed methods was successfully assessed for analyses of both drugs in laboratory-prepared mixtures and in commercial tablet formulations.     

Liquid chromatographic and spectrophotometric determination of diflucortolone valerate and isoconazole nitrate in creams

A new RP-LC method and two new spectrophotometric methods, principal component regression (PCR) and first derivative spectrophotometry, are proposed for simultaneous determination of diflucortolone valerate (DIF) and isoconazole nitrate (ISO) in cream formulations. An isocratic system consisting of an ACE C18 column and a mobile phase composed of methanol-water (95 + 5, v/v) was used for the optimal chromatographic separation. In PCR, the concentration data matrix was prepared by using synthetic mixtures containing these drugs in methanol-water (3 + 1, v/v). The absorbance data matrix corresponding to the concentration data matrix was obtained by measuring the absorbances at 29 wavelengths in the range of 242-298 nm for DIF and ISO in the zero-order spectra of their combinations. In first derivative spectrophotometry, dA/dlambda values were measured at 247.8 nm for DIF and at 240.2 nm for ISO in first derivative spectra of the solution of DIF and ISO in methanol-water (3 + 1, v/v). The linear ranges were 4.00-48.0 microg/mL for DIF and 50.0-400 microg/mL for ISO in the LC method, and 2.40-40.0 microg/mL for DIF and 60.0-260 microg/mL for ISO in the PCR and first derivative spectrophotometric methods. These methods were validated by analyzing synthetic mixtures. These three methods were successfully applied to two pharmaceutical cream preparations.     

Sensitive determination of propoxur by spectrophotometry using 3-aminopyridine.

A simple spectrophotometric method for the determination of propoxur, a widely used insecticide, in various environmental samples and pesticide formulations is described. The method is based on the coupling of the hydrolysis product of propoxur with diazotized 3-aminopyridine in an alkaline medium, to form an azo-dye which has a maximum absorbance at 463 nm. Beer's law is obeyed over the concentration range of 0.05 to 1.2 microg ml(-1) of propoxur. The molar absorptivity and Sandell's sensitivity are found to be 3.10 x 10(4) l mol(-1) cm(-1) and 0.007 microg cm(-2), respectively. The important analytical parameters and optimum reaction conditions were evaluated. The method is free from the interference of other commonly used pesticides and inorganic metal ions.     

Determination of amodiaquine in pharmaceuticals by reaction with periodate and spectrophotometry or by high-performance liquid chromatography

Two methods are described for the determination of amodiaquine in pharmaceuticals. In the first method, amodiaquine was treated with periodate at pH 7.5-8.5 to yield a chromogen, which is believed to be a 1,4-benzoquinone imine derivative, and extracted into chloroform for spectrophotometric assay. The maximum molar absorptivity was found to be 2.17 x 10(3) l mol-1 cm-1 at 442 nm. Primaquine and chloroquine, if present also, do not interfere. The second method, which was used for the simultaneous determination of amodiaquine, primaquine and chloroquine, is based on high-performance liquid chromatography on an octadecylsilane column using a mobile phase of methanol-water (80 + 20) containing 0.5% anhydrous acetic acid and an over-all concentration of sodium dodecyl sulphate of 0.5 mM, with detection at 340 nm.     

Determination of formaldehyde in foodstuffs by flow injection spectrophotometry using phloroglucinol as chromogenic agent

A spectrophotometric method for the determination of formaldehyde in foodstuffs was described by using phloroglucinol as the chromogenic agent. The reaction between formaldehyde and phloroglucinol could occur rapidly at room temperature under mild conditions. The spectrophotometric measurements were conducted at 474nm of an unstable intermediate orange product of the reaction, which greatly increased the sample throughput. Flow injection technique was used to control the merging and reaction timing of the reagents and sample. A detection limit (3sigma) of 0.023microg ml(-1) was achieved. The relative standard deviation was 0.29% for the determination of 7microg ml(-1) formaldehyde (n=11). The proposed method was applied to the analyses of formaldehyde in several preserved foodstuffs and the results were in good agreement with those obtained by a standard method.     

Rapid test methods for minor components analysis of hydraulic cement. Spectrophotometric determination of manganese oxide content of Portland cement and cement raw meal

A rapid, sensitive and highly selective spectrophotometric method for the determination of manganese oxide content of Portland cement and cement raw meal is developed. The method is based on the reaction of manganese(II) with 1,2,4 trihydroxyanthraquinone (purpurin, PURP) in 50% v/v ethanol-water solution at pH 8.5. The solution equilibria of manganese chelates are demonstrated and characterized for delineating optimal conditions of the complexation reaction and analytical aspect of the Mn-PURP system. The analysis of cement materials of variable manganese content is feasible over the concentration range 1.67-8.13 microg ml(-1) Mn, the limit of detection (at the 95% confidence level) of the method is 68 ng ml(-1) for manganese. Under optimum conditions, the use of first derivative spectrophotometry has the advantage of high sensitivity than normal spectrophotometric method and allows the determination of 0.5 microg ml(-1) of manganese.     

Spectrophotometric and spectrofluorimetric methods for the determination of ramipril in its pure and dosage form

This paper describes three sensitive spectrophotometric and spectrofluorimetric methods for determination of ramipril in its pure form and pharmaceutical tablets. The first method is based on the oxidation of the drug with 1-chlorobenzotriazole reagent (CBT) in strong alkaline medium followed by measuring the absorbance at 350 nm. The method obeys Beer's law over concentration range 15-50 microg ml(-1). For the second and third, both are non-extractive methods based on the formation of ternary complex between copper (II), eosin and ramipril in the presence of methylcellulose as surfactant. Spectrophotometrically, under the optimum condition, the ternary complex showed an absorption maximum at 543 nm. The method obeys Beer's law over concentration range of 20-80 microg ml(-1). A fluorescence quenching method for the determination of ramipril by forming this ternary complex was also investigated for the propose of enhance the sensitivity of the determination. The methods are simple, sensitive, and accurate. The results obtained are reproducible with a coefficient of variation less than 2%. The proposed have been successfully applied to the assay of ramipril in tablets. The results compare favorably with official method.     

Stability-indicating methods for the determination of disopyramide phosphate

Four methods were developed for the determination of intact disopyramide phosphate in the presence of its degradation product. In the first and second methods, third-derivative spectrophotometry and first derivative of the ratio spectra were used. For the third-derivative spectrophotometric method, the peak amplitude was measured at 272 nm, while for the derivative ratio spectrophotometric method, disopyramide phosphate was determined by measuring the peak amplitude at 248 and 273 nm. Both methods were used for the determination of disopyramide phosphate in the concentration range 12.5-87.5 microg/mL, with corresponding mean recovery 100.8 +/- 0.7% for the first method and 99.9 +/- 0.7% and 99.6 +/- 0.7% for the second method at 248 and 273 nm, respectively. In the third method, an ion selective electrode (ISE) was fabricated using phosphotungstic acid as an anionic exchanger, PVC as the polymer matrix, and dibutylsebacate as a plasticizer. The ISE was used for the determination of disopyramide phosphate in pure powder form in the concentration range 10(-2)-10(-5) M. The slope was found to be 58.5 (mV/decade), and the average recovery was 99.9 +/- 1.6%. The fourth method depended on the quantitative densitometric determination of the drug in concentration range of 0.25-2.5 microg/spot using silica gel 60 F245 plates and ethyl acetate-chloroform-ammonium hydroxide (85 + 10 + 5, v/v/v) as the mobile phase, with corresponding mean accuracy of 100.3 +/- 1.1%. The 4 proposed methods were found to be specific for disopyramide phosphate in presence of up to 80% of its degradation product for the spectrophotometric methods, 90% of its degradation for the densitometric method, and 40% for the ISE method. The 4 proposed procedures were successfully applied for the determination of disopyramide phosphate in Norpace capsules. Statistical comparison between the results obtained by these methods and the official method of the drug was done, and no significant differences were found.     

Spectrophotometric determination of DNA using a near infrared probe 1,1'-disulfobutyl-3,3,3',3'-tetramethylindotricarbocyanine

A direct spectrophotometric determination of DNA in solution has been developed using a near infrared probe, 1,1'-disulfobutyl-3,3,3',3'-tetramethylindotricarbocyanine (DSTCY). In pH = 7.5 Tris-HCl buffer, the reaction of DSTCY with DNA was complete within 10 min at room temperature in the presence of cetyltrimethylammonium bromide (CTAB), which leaded to a sharp increase of the absorbance at 474 nm. The concentration of DNA can be determined in such wavelength with the linear range of 0.5-8.0 microg ml(-1) and the detection limit of 45 ng ml(-1).