Simultaneous Determination of Acetylsalicylic Acid, Hydrochlorothiazide, Enalapril, and Atorvastatin in a Polypill-Based Quaternary Mixture by TLC.

A new chromatographic-densitometric method has been developed for the qualitative and quantitative determination of the active ingredients in a simulated mixture corresponding to the PolyIran polypill, composed of acetylsalicylic acid, hydrochlorothiazide (HCT), enalapril (ENA), and atorvastatin (ATR), whose efficacy in the treatment and prevention of cardiovascular disease has been documented in clinical trials. Chromatographic separation was performed using TLC silica gel 60 plates with fluorescent indicator F254 as the stationary phase and a mixture of n-hexane-ethyl acetate-methanol-water-acetic acid (8.4 + 8 + 3 + 0.4 + 0.2, v/v/v/v/v) as the mobile phase. Densitometric measurements were carried out at λ = 210 nm when determining ENA and at λ = 265 nm in the case of the other drugs. Peaks of examined substances were well separated in the recorded chromatograms, enabling the evaluation of the results in terms of both qualitative and quantitative analysis. The method was specific for the analyzed components and was characterized by high sensitivity. The LOD was between 0.043 and 0.331 µg/spot, and LOQ was between 0.100 and 0.942 µg/spot. Recovery was in the range of 97.02-101.34%. The linearity range was broad and ranged from 0.600 to 6.000 µg/spot for acetylsalicylic acid, from 0.058 to 1.102 µg/spot for HCT, from 0.505 to 6.560 µg/spot for ENA, and from 0.100 to 1.000 µg/spot for ATR. The method was characterized by good precision, with RSD values that ranged from 0.10 to 2.26%.

Spectrophotometric method for simultaneous determination of valsartan and substances from the group of statins in binary mixtures.

Applicability of derivative spectrophotometry for the determination of valsartan in the presence of a substance from the group of statins was checked. The obtained results indicate that the proposed method may be effective by using appropriate derivatives: for valsartan and fluvastatin - D1, D2 and D3, for valsartan and pravastatin - D1 and D3, for valsartan and atorvastatin - D2 and D3. The method was characterized by high sensitivity and accuracy. Linearity was maintained in the following ranges: 9.28-32.48 mg mL-1 for valsartan, 8.16-28.56 mg mL-1 f or fluvastatin, 14.40-39.90 mg mL-1 for atorvastatin and 9.60-48.00 mg mL-1 for pravastatin. Determination coefficients were in the range of 0.989-0.999 depending on the analyte and the order of derivative. The precision of the method was high with RSD from 0.1 to 2.5 % and recovery of individual components was within the range of 100 ± 5 %. The developed method was successfully applied to the determination of valsartan combined with fluvastatin, atorvastatin and pravastatin in laboratory prepared mixtures and in pharmaceutical preparations.

DETERMINATION OF SOTALOL, OXPRENOLOL AND LABETALOL IN BINARY MIXTURES AND IN SPIKED HUMAN SERUM BY DERIVATIVE SPECTROPHOTOMETRIC METHOD.

The usefulness of derivative spectrophotometry for the determination of labetalol, sotalol and oxprenolol in binary mixtures and in human spiked serum was checked. To this aim a spectrophotometric analysis of samples in the UV range was carried out and the obtained results revealed that derivative spectropho- tometry allows for the fast, accurate and precise determination of the tested substances in spite of their clear interference in the zero-order spectra. For quantitative determinations "zero-crossing" technique was used to establish wavelengths for zeros of specified component. In a mixture of labetalol and oxprenolol the following wavelengths were established: D1 λ = 245.32 nm and 266.03 nm, D2 λ = 243.30 nm and 301.09 nm. respectively. D3 derivative did not show zeros suitable for quantitative analysis. For the analysis of labetalol and sotalol mixture, D3 derivative spectrophotometry was used at the following wavelengths: = 246.03 nm and λ = 249.91 rum, respectively. In this case, the curves of Dl and D2 derivatives showed no zeros that can be used in quantitative analysis. To determine the concentration of the components in a mixture containing oxprenolol and sotalol the following wavelengths were selected: for oxprenolol DI λ = 245.32 nm, D2 λ = 240.18 run, D3 λ = 232.05 nm and for sotalol Dl λ = 230.56 nm, D2 Xλ= 232.65 nm and D3 X = 238.84 tm, respectively. The developed spectrophotometric method was characterized by high sensitivity and accuracy, LOD determined for sotalol was in the range of 0.21-1.88 µg/mL, for labetalol 1.00-3.43 µg/mL and for oxprenolol 0.16-2.06 µg/mL; LOQ determined for sotalol was in the range of 0.65-5.70 µg/mL, for labetalol 3.11-10.39 µg/mL and for oxprenolol 0.47-6.23 µg/mL, depending on the composition of the tested mixture and the order of the deriv- ative. The recovery of the individual components was within the range of 100 ± 5%. The linearity range was wide and estimated for sotalol in the range of 11.00-38.50 µg/mL, for labetalol 12.80-44.80 µg/mL and for oxprenolol 12.60-44.10 µg/mL with correlation coefficients in the range of 0.9977-0.9999.

Simultaneous Determination of Eight Hypotensive Drugs of Various Chemical Groups in Pharmaceutical Preparations by HPLC-DAD.

A new sensitive, simple, rapid, and precise HPLC method with diode array detection has been developed for separation and simultaneous determination of hydrochlorothiazide, furosemide, torasemide, losartane, quinapril, valsartan, spironolactone, and canrenone in combined pharmaceutical dosage forms. The chromatographic analysis of the tested drugs was performed on an ACE C18, 100 Å, 250×4.6 mm, 5 µm particle size column with 0.0.05 M phosphate buffer (pH=3.00)-acetonitrile-methanol (30+20+50 v/v/v) mobile phase at a flow rate of 1.0 mL/min. The column was thermostatted at 25°C. UV detection was performed at 230 nm. Analysis time was 10 min. The elaborated method meets the acceptance criteria for specificity, linearity, sensitivity, accuracy, and precision. The proposed method was successfully applied for the determination of the studied drugs in the selected combined dosage forms.

Derivative spectrophotometric method for simultaneous determination of zofenopril and fluvastatin in mixtures and pharmaceutical dosage forms.

Fast, accurate and precise method for the determination of zofenopril and fluvastatin was developed using spectrophotometry of the first (D1), second (D2), and third (D3) order derivatives in two-component mixtures and in pharmaceutical preparations. It was shown, that the developed method allows for the determination of the tested components in a direct manner, despite the apparent interference of the absorption spectra in the UV range. For quantitative determinations, "zero-crossing" method was chosen, appropriate wavelengths for zofenopril were: D1 λ=270.85 nm, D2 λ=286.38 nm, D3 λ=253.90 nm. Fluvastatin was determined at wavelengths: D1 λ=339.03 nm, D2 λ=252.57 nm, D3 λ=258.50 nm, respectively. The method was characterized by high sensitivity and accuracy, for zofenopril LOD was in the range of 0.19-0.87 µg mL(-1), for fluvastatin 0.51-1.18 µg mL(-1), depending on the class of derivative, and for zofenopril and fluvastatin LOQ was 0.57-2.64 µg mL(-1) and 1.56-3.57 µg mL(-1), respectively. The recovery of individual components was within the range of 100±5%. For zofenopril, the linearity range was estimated between 7.65 µg mL(-1) and 22.94 µg mL(-1), and for fluvastatin between 5.60 µg mL(-1) and 28.00 µg mL(-1).

Determination of losartan potassium, quinapril hydrochloride and hydrochlorothiazide in pharmaceutical preparations using derivative spectrophotometry and chromatographic-densitometric method.

Two methods, spectrophotometric and chromatographic-densitometric ones, were developed for determination of losartan potassium, quinapril hydrochloride and hydrochlorothiazide in pharmaceutical preparations. Spectrophotometric method involved derivative spectrophotometry and zero order spectrophotometry. The measurements were carried out at lambda = 224.0 nm for quinapril, lambda = 261.0 nm for hydrochlorothiazide and lambda = 270.0 nm for losartan when the derivative spectrophotometry was applied and lambda = 317.0 nm when zero order spectrophotometry was applied for the determination of hydrochlorothiazide. In chromatographic-densitometric studies high performance thin layer chromatography (HPTLC) plates were used as stationary phase and a mixture of solvents n-butanol : acetic acid : water (15 : 5 : 1, v/v/v) as mobile phase. Under the established conditions good resolution of examined constituents was obtained. Retardation factor for quinapril hydrochloride was R(f) - 0.70, for losartan potassium R(f) - 0.85 and for hydrochlorothiazide R(f) - 0.78. The developed methods are characterized by high sensitivity and accuracy. For quantitative analysis, densitometric measurements were carried out at lambda = 218.0 nm for quinapril, lambda = 275.0 nm for hydrochlorothiazide and = 232.0 nm for losartan.

Stability studies of clonazepam, diazepam, haloperidol, and doxepin with diverse polarities in an acidic environment.

Stability of clonazepam, diazepam, haloperidol, and doxepin was determined in acidic solutions. In addition, determination of the kinetic and thermodynamic properties of this stability was carried out. Reaction rate constants (k), half-life times (t(0.1) and t(0.5)), and activation energy (Ea) were estimated for the drugs, which differed in polarity expressed with log P values. It was observed that estimated Ea values increased from 42.13 to 125.03 kJ/mol with an increase of lipophilicity (log P) beginning from the most hydrophilic drug (clonazepam, 2.70 log P) to the most lipophilic drug (doxepin, 4.10 log P). All degradation products were studied using an HPLC/electrospray ionization-MS technique in the positive ionization mode.

Analysis of hypotensive compounds occurring in complex agents.

This is a review of analytical methods, such as spectrophotometry, derivative spectrophotometry and various chromatographic (gas chromatography-GC, high-performance liquid chromatography-HPLC, thin-layer chromatography-TLC, high-performance thin-layer chromatography-HPTLC, liquid chromatography-tandem mass spectrometry-LC-MS, microchip electrophoresis-MCE, capillary electrophoresis-CE) and electroanalytical methods (differential pulse polarography-DPP, cathodic stripping voltammetry-CSV, anodic stripping voltammetry-ASV, differential pulse voltammetry-DPV, cyclic voltammetry-CV, stripping voltammetry-SV, square wave voltammetry-SWV, square wave polarography-SWP) that are used in the analysis of hypotensive complex agents. This review is based on representative publications that were published between 1995 and 2009.

Validation of derivative spectrophotometry method for determination of active ingredients from neuroleptics in pharmaceutical preparations.

First (DI) and second (D2) order derivative spectrophotometric method with an application of base line to peak technique was used for determination of active pharmaceutical ingredients (API) at two wavelengths: fluphenazine (D1 at lambda = 251 nm and lambda = 265 nm, D2 at lambda = 246 nm and lambda = 269 nm), pernazine (D1 at lambda = 246 nm and lambda = 258 nm, D2 at lambda = 254 nm and lambda = 262 nm), haloperidol (DI at = 235 nm and lambda = 253 nm, D2 at lambda = 230 nm and lambda = 246 nm), and promazine (D1 at lambda = 246 nm and lambda = 251 nm, D2 at lambda = 255 nm and lambda = 262 nm). Linear dependence of derivative values on analyte concentration is maintained in a range 3.12 microg x mL(-1) - 44.80 microg x mL(-1). Detection and determination limits are in the range 0.51 - 3.23 microg x mL(-1) and 1.27 microg x mL(-1) - 9.80 microg x mL(-1), respectively. Determination results of drug constituents are very accurate. Recovery percentage is in a range 95.50% - 103.60%.

Simultaneous determination of triamterene and hydrochlorothiazide in tablets using derivative spectrophotometry.

A quick and accurate method for determining triamterene and hydrochlorothiazide in complex drugs of diuretic activity by using first-derivative (D1) and second-derivative (D2) spectrophotometry was developed. The zero-crossing technique was employed in measurements, using D1 at lambda = 240.9 nm and D2 at lambda= 278.2 nm for determining triamterene and D1 at lambda = 255.7 nm and D2 at lambda = 283.2 nm for hydrochlorothiazide. The linear relationship between the values of derivatives and analyte concentrations are maintained for concentrations from 2.40 microg x mL(-1) to 12.00 microg x mL(-1) for triamterene and from 1.25 microg x mL(-1) to 6.25 microg x mL(-1) for hydrochlorothiazide. LOD for triamterene was 0.90 microg x mL(-1) or 1.02 microg x mL(-1), while LOQ was 2.73 microg x mL(-1) or 3.08 microg x mL(-1). The corresponding values for hydrochlorothiazide were: LOD 0.25 microg x mL(-1) or 0.17 microg x mL(-1) and LOQ 0.77 microg x mL(-1) or 0.51 microg x mL(-1) depending on the derivative used. The determination results of drug constituents are of high accuracy, percentage recovery ranging from 97.17% to 99.74% for triamterene and from 102.44% to 102.64% for hydrochlorothiazide, and good precision. The computed values of RSD are smaller than 2.73% for triamterene and below 1.63% for hydrochlorothiazide. Selectivity and sensitivity of the developed method are satisfactory.

Application of derivative spectrophotometry for determination of enalapril, hydrochlorothiazide and walsartan in complex pharmaceutical preparations.

A derivative spectrophotometry method was developed to determine enalapril, hydrochlorothiazide, candesartan and walsartan in complex antihypertensive drugs. The pharmaceutical preparations containing hydrochlorothiazide and one of the angiotensin convertase inhibitors were investigated. It was found that the developed method enables the constituents of the investigated drugs to be determined directly despite evident interference of the zero order absorption spectra. For determination of enalapril and hydrochlorothiazide as well as candesartan and hydrochlorothiazide the first derivative was used, while for walsartan and hydrochlorothiazide the second derivative was employed. The method was of high sensitivity; the LOD accuracy for enalapril was 2.81 microg x mL(-1), 0.56 microg x mL(-1) for candesartan, 4.02 microg x mL(-1) for walsartan and ranged from 0.31 microg x mL(-1) to 1.78 microgxmL(-1) for hydrochlorothiazide, depending on preparation under investigation. The recovery of individual constituents was within the limit of 100% +/- 5%, RSD varied from 1.11% to 2.94%, and the linearity range was from 4.1 microg x mL(-1) to 20.5 microg x mL(-1) for enalapril, from 6.45 microg x mL(-1) to 32.25 microg x mL(-1) for walsartan, from 2.36 microg x mL(-1) to 11.80 microg x mL(-1) for candesartan, and from 0.96 microg x mL(-1) to 26.00 microg x mL(-1) for hydrochlorothiazide.

Spectrophotometric determination of Pb(II), Fe(III) and Bi(III) in complexes with 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (DACT).

A UV spectrophotometric method was developed for simultaneous determination of ions: Pb(II), Fe(III) and Bi(III) in complexes with DACT. Zero-order and derivative spectra were used for the determinations. Under the established experimental conditions the described method furnished reliable results with low limit of detection (from 0.09 microg x mL(-1) to 1.75 microg x mL(-1)), high recovery (from 96.08% to 97.81%) and broad range of linearity for the analyzed ions. Good precision of the method was confirmed in experiments on model solutions containing mixtures of ions studied at different concentrations and in statistical analysis of the data obtained.

Determination of metoprolol and hydrochlorothiazide by derivative spectrophotometric method in pharmaceutical preparations.

A procedure for simultaneous determination of metoprolol and hydrochlorothiazide in tablets by employing derivative spectrophotometry, "zero-crossing" method was developed. The third order derivative absorption spectra at lambda approximately 281 nm were used for metoprolol and the first order derivative spectra at lambda approximately 282 nm were used for hydrochlorothiazide. No interferences were found between both determined constituents and those of matrix. A good accuracy and precision of simultaneous determination of metoprolol and hydrochlorothiazide were confirmed by statistical analysis. The recovery of individual constituents under established conditions is very high and ranges from 98.79% to 99.39%. Linearity is maintained within a wide concentration range from 100.0 microg mL(-1) to 300.0 microg mL(-1) and from 12.5 microg mL(-1) to 37.5 microg mL(-1) for metoprolol and hydrochlorothiazide, respectively. The detection limit is 5.0 microg mL(-1) for metoprolol and 1.5 microg mL(-1) for hydrochlorothiazide. The corresponding quantitation limits are 15.0 microg mL(-1) for metoprolol and 4.5 microg mL(-1) for hydrochlorothiazide.

Application of derivative spectrophotometry to simultaneous determination of indomethacin and 5-methoxy-2-methyl-3-indoleacetic acid in metindol injections.

Derivative spectrophotometry was employed to develop a rapid and accurate method for simultaneous determination of indomethacin and 5-methoxy-2-methyl-3-indoleacetic acid as its possible impurity in Metindol injections. At the selected wavelengths, 233.04 and 284.65 nm, no interference between the components determined was observed. Under the established experimental conditions, recoveries of the particular components were from 96.14 to 98.17%. Linearity was maintained over a broad range of concentrations, from 11.88 x 10(-3) to 35.64 x 10(-3) mg/mL for indomethacin and 0.4 to 1.2 mg/mL for 5-methoxy-2-methyl-3-indoleacetic acid. The limit of detection was found to be 6.0 x 10(-3) mg/mL for indomethacin and 0.04 x 10(-3) mg/mL for 5-methoxy-2-methyl-3-indoleacetic acid. The limits of quantitation were found to be 10.0 x 10(-3) mg/mL and 0.20 x 10(-3) mg/mL, respectively.