Nm In Methanol Research Articles

Stereoselective non-equivalent bis-diimine coordination to Co(II) ion: Structure, luminescence and density functional theory calculations

Stereoselective coordination affording a luminescent tcc-isomer of dihalobis(diimine)Co(II) family in which two photoactive diimine ligands (L NO2 ϕ) are unsymmetrical and non-equivalent is reported (L NO2 ϕ = ( E)-3-nitro- N-(pyridine-2-ylmethylene)aniline; ϕ = dihedral angle between the diimine unit including pyridine ring and the phenyl ring planes; tcc refers trans–cis–cis positions with respect to pyridine nitrogen-imine nitrogen-chloride donors). The single step reaction of 2-pyridinecarboxaldehyde, 3-nitro aniline and anhydrous cobalt dichloride affords only the tcc-(L NO2 ϕ1)(L NO2 ϕ2)Co IICl 2 as the product which is characterized by IR, Mass, UV–Vis spectra and magnetic susceptibility measurements. Single crystal X-ray structure determination has established the orientation of the two ligands in the crystal as (L NO2 33.7)(L NO2 79.7)Co IICl 2·0.25CH 3OH ( 1). The isomer is luminescent in frozen methanol glass at 77 K with the excitation and emission maxima respectively at 370 and 525 nm. The average luminescence life time is 1.86 ns measured on exciting at 356 nm. Density functional theory (DFT) calculation shows that the non-equivalence of the two diimine ligands prevails in the gas phase also and the geometry is (L NO2 41.0)(L NO2 60.5)Co IICl 2. The calculation has identified four types of closely spaced localized π ∗ orbitals as unoccupied photoactive molecular orbitals (UPMOs). TD-DFT calculations have assigned the Co(II) to π ∗ charge transfer (MLCT) and π to π ∗ of charge transfer (LLCT) as the primary origin of absorption above 340 nm in methanol. Pendant nitro groups of the ligands and their intermolecular interactions have been the driving force of the stereoselectivity of the product. The binuclear L 4Co 2Cl 4 unit of 1 has constructed the helical 2D assembly and cis-CoCl 2 mediated strong inter-helices H-bonding interactions result the channeled 3D framework. Geometry optimization of other possible ttt, ctc, ccc and cct isomers has established that in the gas phase, the tcc-isomer is more stable at least by 20–42 kJ mol −1 compared to other isomers where the two diimine ligands are equivalent.

Miniemulsion polymers as solid support for transition metal catalysts

A pentadentate salen-type ligand was immobilized in a poly[(styrene)]- co-(butyl acrylate)] matrix by miniemulsion polymerization. The obtained polymer beads revealed a particle size of 50 nm in the dry state by transmission electron microscopy. Dynamic light scattering experiments in methanol and water showed a solvent-dependent average particle size with a mean particle diameter of up to 233 nm in methanol. These results provide valuable insights for the optimization of macromolecular oxidation catalysts and their future use as enzyme-like entities in aqueous media. The particle stability was demonstrated over a wide pH range (3–11) by gel permeation chromatography, and initial results for the metal ion binding ability were obtained.

Immobilization and Incorporation of Antigenic Peptide P17-1 from HIV-1 P17 Protein in Nanostructured Films

The immobilization of antigenic peptides in nanostructured films is promising for the development of highly specific immunosensors. In this work, we analyze the peptide p17-1 (LSGGELDRWEKIRLRPGG), derived from the HIV-1 p17 protein, immobilized into Layer-by-Layer (LbL) films and incorporated into Langmuir monolayers of phospholipids. The LbL film was assembled using different polyelectrolytes but only poly(allylamine) hydrochloride (PAH) was efficient for the peptide immobilization. The intensity in the UV-Vis. spectra of PAH/p17-1 films increased exponentially with the number of layers, which may indicate that the peptide can be reorganized in each bilayer adsorbed. Fluorescence and circular dichroism (CD) spectra indicated that the interaction with the film did not induce an alpha helix conformation in p17-1, analogously to what occurs in an aqueous solution and in contrast to the organized peptide in a methanol solution. The maximum emission for p17-1 fluorescence occurred at 340 nm in methanol, compatible with tryptophan residue buried in the solvent, while for p17-1 in an LbL film the maximum appeared at 355 nm. This red shift is consistent with the tryptophan being exposed to the environment. The CD spectra confirmed these results showing the random structure for p17-1 in the LbL films and an α-helix structure in methanol solution. The lack of structure is the probable reason for the low sensitivity toward anti-p17 observed in amperometric sensors made with PAH/p17-1 LbL films. With regard to the Langmuir monolayers, p17-1 was found to affect the surface pressure isotherms of dipalmitoyl phosphatidyl glycerol (DPPG), even at a concentration as low as 0.5 mol%. This cooperative interaction of p17-1 and DPPG may perhaps be exploited in designing new architectures for producing immunosensors based on antigenic peptides.

A validated method for development of atovaquone as API and tablet dosage forms by UV spectroscopy.

A simple new spectrophotometric method has been developed for estimation of Atovaquone in bulk and tablet dosage form. Atovaquone is estimated to be 251 nm in methanol. The Beer's law is obeyed in the concentration range of 1–10 μg/mL of the drug. The slope and intercept values are 0.111 and 0.012, respectively. Results of analysis of this method have been validated statically and by recovery studies. The method is applied to the marketed tablet formulation. A result of the analysis of tablet formulation, given as a percentage of label claim ± standard deviation, is 99.14 ± 0.66. The precision and accuracy has been examined by performing recovery studies and found to be 100.09 ± 1.14. The developed method is simple, sensitive, and reproducible, and can be used for the routine analysis of Atovaquone in bulk and tablet dosage form.

Laser Ablated Silver Nanoparticles with Nearly the Same Size in Different Carrier Media

Poly(vinyl‐pyrrolidone) (PVP) stabilized silver nanoparticles with an average particle size ranging from 4.3 to 4.9 nm were synthesized by laser ablation in preformed colloids in methanol, acetone, ethylene glycol, and glycerin. Aqueous colloids obtained using PVP, poly(vinyl‐alcohol) (PVA), and sodium citrate as stabilizing agents also lead to a good control over particle size distribution. Silver ions were reduced with sodium borohydride. The smaller average particle size and narrower dispersivity in comparison to previously reported data were ascribed to the relatively small size of the particles formed in the chemical reduction step, laser fluence, and the use of PVP, which was not previously used as the stabilizing agent in “top‐down” routes. The surface plasmon resonance band maximum wavelength shifted from 398 nm in methanol to 425 nm in glycerin. This shift must be due to solvent effects since all other variables were the same.

Synthesis and light-emitting properties of 2-(N-phenyl-α-naphthylamino) and 2-dimesitylboron-7-(N-phenyl-α-naphthylamino)-9,9-diethylfluorene

A fluorescent organic triarylamine with a symmetric structure, 2,7-bis(N-α-naphthyl-phenylamino)-9,9-diethylfluorene (NPAEF) was synthesized using two methods, modified Ullmann coupling and modified palladium-catalyzed amination. An activated copper and a combination of Pd(OAc)2/P(t-Bu)3 and Pd(dba)2/P(t-Bu)3 were selected as catalysts to improve yields of reactions. These synthetic procedures were also successfully applied to an asymmetric 2-dimesitylboron-7-(N-phenyl-α-naphthylamino)-9,9-diethylfluorene (BNPEF). Photoluminescent emission peaks in solid film and in diluted solution of NPAEF were both observed at 461 nm, while the main emission peaks of BNPEF appeared at 422 nm in hexane, and at 480 nm in methanol. The double emission peaks of BNPEF in hexane reflected fine structure in the vibrational state. With an increasing polarity of solvent, the main PL emission peaks were red-shifted and vibrational fine structure disappeared. Additionally, energy levels of NPAEF were investigated and an electroluminescence (EL) device of ITO/PVK:NPAEF/Al was fabricated, which showed a turn-on voltage of 9 V and peaked at 462 nm. The EL spectrum was in good agreement with PL spectrum, which indicated that they were from the same emitting center in the device.

Second Derivative Synchronous Fluorescence Spectroscopy for the Simultaneous Determination of Chlorzoxazone and Ibuprofen in Pharmaceutical Preparations and Biological Fluids

A rapid, simple and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of chlorzoxazone (CLZ) and ibuprofen (IP). The method is based upon measurement of the synchronous fluorescence intensity of these drugs at Dλ=60 nm in methanol. The different experimental parameters affecting the fluorescence of the two drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.2-4 mg/mL and 0.1-1.6 mg/mL for CLZ and IP, respectively with lower detection limits (LOD) of 0.028 and 8.3 × 10-3 mg/mL and quantification limits (LOQ) of 0.086 and 0.03 mg/mL for CLZ and IP, respectively. The proposed method was successfully applied for the determination of the two compounds in synthetic mixtures and in commercial capsules. The high sensitivity attained by the proposed method allowed the determination of both drugs and real human plasma samples. The mean % recoveries in real human plasma (n=3) were 87.69 ± 6.15 and 92.57 ± 4.39 for each of CLZ and IP respectively.

Potentials of 3, 31, 41, 5, 7-pentahydroxyflavylium of Hibiscus rosa-sinensis L. (Malvaceae) flowers as ligand in the quantitative determination of Pb, Cd and Cr.

3, 31,41,5,7-Pentahydroxyflavylium chloride (cyanidin chloride) was extracted from the flowers of Hibiscus rosa-sinensis L. and blackberry fruits and the purity confirmed by co-chromatography with authentic marker on thin layer chromatography (TLC) and paper chromatography (PC). UV-Visible spectrophotometric determinations of the sample and its Pb (II), Cr (III) and Cd (II) complexes at various pH were carried out. The cyanidin sample absorbs at 530 and 540 nm in methanol and ethanol respectively. A Cyanidin-Pb (II) complex was formed at pH 4.2 (λmax = 555 nm, in methanol). A Cyanidin-Cr (III) complex was formed at pH 1.0 (λmax = 682 nm, methanol and ethanol) while a Cyanidin-Cd (II) complex was formed at pH 3.0 [λmax = 706 nm (methanol) and 679 nm (ethanol)]. All the metal-ligand complexes occur in the ratio of 1:2 and the molar absorptivities are 9.66 x 102, 8.77 x 102 and 9.77 x 102 L.mol-1.cm-1 for Pb, Cr and Cd respectively. Under optimum conditions, the absorbance of the complexes was found to increase linearly with increase in metal-ion concentrations, which corroborated with the correlation coefficient values. The linear range of the calibration graph was 0.1 – 0.5 mM for all the complexes. The results show that cyanidin could be used as a reagent for the spectrophotometric determination of Cr (III), Pb (II) and Cd (II) and by varying the pH, these metals could be determined simultaneously in solution. Key words: Cyanidin chloride, Hibiscus rosa-sinensis, metal - ligand complex, Lead (II), chromium (III), Cadmium (II), spectrophotometric assay.

UV Spectrophotometric Method for Determination of Cinitapride in Pure and its Solid Dosage Form

A new, rapid, precise, accurate and sensitive analytical method was developed for the UV spectrophotometric assay of cinitapride (CTP). The drug obeyed the Beer′s law and showed good correlation. It showed absorption maxima at 260 nm in methanol. The linearity was observed between 5‐40 µg mL-1. The results of analysis were validated by recovery studies. The recovery was more than 99%. The proposed method is the only method available for spectrophotometric determination of the drug. It is simple, precise, sensitive and reproducible and can be used for the routine quality control testing of the marketed formulations.

UV spectrophotometric method for simultaneous estimation of tizanidine and valdecoxib in tablet dosage forms

The simple, selective, rapid and precise UV spectrophotometric method has been developed for the simultaneous estimation of valdecoxib and tizanidine in pharmaceutical dosage form. The proposed method is based on the Vierodt's simultaneous equations. Tizanidine has absorption maxima at 318.1 nm and valdecoxib absorption maxima at 239.0 nm in methanol. The linearity was observed in the concentration range of 2-18 μg/ml for tizanidine and valdecoxib. Both the drugs obey Beer's law. The method is validated statistically. The recovery studies confirmed the accuracy of the proposed method.

Spectrophotometric Determination of Doxazosin Mesylate in Tablets by Ion-Pair and Charge-Transfer Complexation Reactions

Two accurate, easy spectrophotometric methods for the determination of doxazosin mesylate were described. The first method was based on the formation of ion-pair complexes with the acidic sulfophthalein dyes bromocresol purple (BCP) and bromophenol blue (BPB) in pH 3.3 and 4.5 citrate-phosphate buffer, respectively. The formed complexes were extracted into dichloromethane, and their absorbance was measured at 403 and 410 nm for BCP and BPB, respectively. The second method was based on the charge transfer reaction of the drug as an n-electron donor with either 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give colored radical anions. The absorbances of products were measured at 457 nm in acetonitrile and 838 nm in methanol for DDQ and TCNQ, respectively. Under the optimum reaction conditions, Beer's law was obeyed with a good correlation coefficient (r = 0.9997-0.9999) in the concentration ranges 3.0-18.0, 3.0-20.0, 15.0-95.0, and 10.0-100.0 microg/mL for the BCP, BPB, DDQ, and TCNQ methods, respectively. Limits of detection of the BCP, BPB, DDQ, and TCNQ methods were 0.314, 0.408, 1.935, and 1.610 microg/mL, respectively. The limits of quantification were 1.045, 1.360, 6.449, and 5.367 microg/mL, respectively. The parameters molar absorptivity, precision, accuracy, recovery, robustness, and stability constant were studied. The proposed methods were successfully applied for determination of the drug in tablets with good accuracy and precision. Statistical comparison of the results with those obtained by a reported method showed good agreement and indicated no significant difference in accuracy and precision.

Simultaneous spectrophotometric estimation of imipramine hydrochloride and chlordiazepoxide in tablets

A binary mixture of imipramine HCl and chlordiazepoxide was determined by three different spectrophotometric methods. The first method involved determination of imipramine HCl and chlordiazepoxide using the simultaneous equations and the second method involved absorbance ratio method. Imipramine has absorbance maxima at 251 nm, chlordiazepoxide has absorbance maxima at 264.5 nm and isoabsorptive point is at 220 nm in methanol. Linearity was obtained in the concentration ranges of 1-25 and 1-10 μg/ml for Imipramine HCL and Chlordiazepoxide, respectively. The third method involved determination of these two drugs using the first-derivative spectrophotometric technique at 219 and 231.5 nm over the concentration ranges of 1-20 and 2-24 μg/ml with mean accuracies 99.46±0.78 and 101.43±1.20%, respectively. These methods were successively applied to pharmaceutical formulations because no interferences from the tablet excipients were found. The suitability of these methods for the quantitative determination of the compounds was proved by validation.

Second Derivative Synchronous Fluorescence Spectroscopy for the Simultaneous Determination of Metoclopramide and Pyridoxine in Syrup and Human Plasma

A rapid, simple, and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous determination of metoclopramide (MT) and pyridoxine (PY) in a binary mixture. The method is based on measurement of the native fluorescence of these drugs at delta lambda = 80 nm in methanol. The different experimental parameters affecting the native fluorescence of the drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the ranges of 0.02-0.4 and 0.1-2 microg/mL for MT and PY, respectively. The limits of detection were 0.003 and 0.007 microg/mL and the limits of quantification were 0.008 and 0.02 microg/mL for MT and PY, respectively. The proposed method was successfully applied to the determination of MT and PY in synthetic mixtures and in commercial syrup. The results were in good agreement with those obtained with a reported method. The high sensitivity attained by the proposed method allowed the determination of MT in spiked and real human plasma samples. The mean percent recoveries of MT from spiked and real human plasma (n = 3) were 93.72 +/- 3.15 and 89.72 +/- 2.19 respectively.

New laser dye based on the 3-styryl analog of the BODIPY dye PM567

We report the synthesis, photophysical properties and evaluation of laser dye of a new BODIPY dye with a 3-styryl substituent, PMS, and with the rest of the substituents as in the commercial dye PM567. PMS shows an emission band at 584 nm in methanol, i.e. displaced ca. 50 nm to longer wavelengths with regard to the green-emission band of PM567, as well as a high-fluorescence quantum yield (0.82) and also a high-molar absorption coefficient (10 5 M −1 cm −1) in the same solvent. The laser action of the new dye has been analyzed under transversal pumping at 532 nm, 5.5 mJ pulse −1 and up to 10 Hz repetition rate, in both liquid phase and incorporated into solid polymeric matrices of methyl methacrylate copolymerized with crosslinking or fluorinated monomers. Lasing emission at 602–610 nm, with maximum efficiencies of 18%, were reached in these media. In solid-fluorinated matrices, good lasing photostabilities were established, with 30% of the initial laser output remaining after 100,000 pump pulses at 10 Hz.

Isolation and inhibitory effect of anti-Vibrio substances from Pseudoalteromonas sp. A1-J11 isolated from the coastal sea water of Kagoshima Bay

Among several marine antagonistic bacteria isolated from the sea water of Kagoshima Bay, Pseudoalteromonas sp. A1-J11 was found to produce anti-Vibrio substances. The anti-Vibrio substances were extracted from the culture supernatant of the strain with chloroform and isolated using reverse-phase (Cosmosil 75C18-OPN) column chromatography followed by high-pressure liquid chromatography (Mightysil RP-18 GP Aqua). Purified substances, designated as AVS-03a, c and d showed similar ultraviolet absorption spectra with λmax at 215, 235, 315 and 327 nm in methanol. AVS-03d, the major anti-Vibrio substance, was thermostable up to 100°C and pH stable over a pH range higher than 4.0, and also showed strong inhibitory activities, specifically against Vibrio harveyi strains.

Spectrophotometric estimation of pioglitazone hydrochloride in tablet dosage form

Two simple, rapid, and precise methods - linear regression equation (LRE) and standard absorptivity - were developed and validated for the estimation of pioglitazone hydrochloride in tablet dosage form. The maximum absorbance (λmax) of pioglitazone hydrochloride was found to be 269.8 nm in methanol:water:hydrochloric acid (250:250:1). Beer-Lambert law was obeyed in the concentration range of 10-50 μg/ml, and the standard absorptivity was found to be 253.97 dl/g/cm. Both the methods were validated for linearity, accuracy, precision (days, analysts, and instrument variation), and robustness (solvent composition). The numerical values for all parameters lie within the acceptable limits. Pioglitazone hydrochloride was estimated in the range of 99.58-99.97% by LRE method and 100.25-100.75% by standard absorptivity method. At 99% confidence limit, the F-test value for the methods was found to be 1.8767

The Immunosuppressive Drug Mycophenolic Acid Does Not Bind Iron(II) Under Conditions Mimicking the Upper Gastrointestinal Environment

Anemia is common in renal transplant patients, especially pediatric recipients, which makes iron supplementation usual in therapeutic regimens (1). The potential of iron to impede absorption of the immunosuppressive drug mycophenolic acid (MPA) has been noted. A trial by Morii et al. (2) showed a remarkable 89.7% reduction in bioavailable MPA when the prodrug mycophenolate mofetil (MMF) was co-administered with oral iron supplements in healthy adult volunteers. As a result of the Morii trial (2), a number of studies in both healthy subjects and renal transplant patients were undertaken, yet all have failed to show iron influencing MPA availability (3–5). The rapid hydrolysis of MMF converts the ester to the carboxylic acid, MPA, which is capable of metal binding. Indeed, we have shown that MPA can form a stable complex with copper (6). Morii et al. (2) hypothesized that reduction in MPA availability was due to iron binding to MMF, however as our results with copper binding indicated, it is more likely that MPA itself is the potential iron ligand. The later trials tend to suggest MPA is either not coordinating iron or, if it does bind iron, then a stable complex is not formed. In this letter we have investigated if MPA-iron complexes are likely to occur in the gastrointestinal tract after concomitant administration of MMF and iron supplements. We used ultraviolet/visible spectroscopy to investigate the binding of both iron(II) and iron(III) to MPA when in a simple solvent (methanol) and compared that to the situation when in simulated gastric acid (sGA) at pH 6.1 (7). Figure 1A shows the spectrum obtained after the addition of Fe2+ to MPA (both 1 mM) dissolved in sGA. In pure methanol, a small peak was observed near 500 nm (Fig. 1A), however in sGA no such peak was observed and the solution remained colorless. The peak at 500 nm in methanol is suggestive of some Fe2+ binding to MPA (the peak is due to ligand-to-metal charge-transfer or d-d transitions). Analysis by mass spectrometry provided evidence for the formation of a small amount of [Fe(MPA)2]+, where two MPA molecules act as ligands for the Fe2+ ion (data not shown). The low intensity of the peak associated with this complex suggested that the complex is not formed to any great extent or is not stable. Figure 1B shows that the addition of Fe3+ to MPA (both 1 mM) in methanol results in an intense 590-nm peak, suggesting that MPA is able to coordinate Fe3+. This intense peak is not observed when Fe3+ and MPA are in sGA, only a very weak absorbance is apparent (the addition of Fe3+ to sGA alone had no effect). Thus there is only very limited coordination of Fe3+ by MPA in sGA.FIGURE 1.: Binding of iron to MPA in simulated gastric acid (sGA). (A) MPA (1 mM) and Fe2+ (1 mM) were mixed in sGA and the UV/Vis spectrum obtained. For comparison the spectrum obtained from MPA (1 mM) and Fe2+ (1 mM) in methanol (MeOH) is shown. (B) MPA (1 mM) and Fe3+ (1 mM) were mixed in sGA and the UV/Vis spectrum obtained. The spectrum obtained for MPA (1 mM) and Fe3+ (1 mM) in methanol is shown (black line). The dashed line shows the addition of Fe3+ to sGA in the absence of MPA.In conclusion, although we observed evidence for iron/MPA complexes when prepared in methanol, we were unable to see similar effects when we combined MPA and iron in sGA. The lack of MPA-iron(II) complexes in sGA supports the trials that show no effect on MPA availability when MMF and iron supplements are coadministered (3–5). Alison C. Badrick Christopher E. Jones Centre for Metals in Biology School of Molecular and Microbial Sciences The University of Queensland St. Lucia, Queensland

Synthesis and spectral characteristics of di-substituted 1,8-naphthalimides: Bi-radical formation

Novel probes representing connection of 1,8-naphthalimides as chromophore and two structural units of sterically hindered amine stabilizer (HAS) were synthesized. One HAS unit was situated on naphthalene ring in position 4 and second HAS created imide composition. HASes were in the form of parent amine – DINH, stable nitroxyl radical – DINO and substituted hydroxylamine DINOR. Absorption and fluorescence spectra of probes were taken in solution as well as in polymer films. In absorption spectrum the longest wavelength band was shifted from 410 nm in non-polar cyclohexane to 440 nm in polar methanol. In fluorescence spectrum the maximum of the broad band is red shifted from 460 nm in cyclohexane to 530 nm in methanol. All derivatives exhibit similar solvatochromism in absorption as well as in fluorescence spectrum. The fluorescence is observed for all probes but there is distinctly much higher fluorescence intensity for parent amine DINH and alkoxyamine DINOR than for adequate bi-radical DINO. The extent of fluorescence enhancement comparing amine and alkoxyamine derivatives with bi-radical is in the range 10–70 depending on the medium. Using laser flash photolysis the probe DINH exhibited transient absorption after 266 nm excitation in the nanosecond time scale region which is ascribed to triplet state. This transient absorption is red shifted in going from non-polar cyclohexane (460 nm) to polar methanol (520 nm). No (or extremely weak transient) absorption spectra was observed for stable nitroxyl bi-radical DINO.

Simultaneous spectrophotometric determination of paracetamol, ibuprofen and caffeine in pharmaceuticals by chemometric methods

In this study, the simultaneous determination of paracetamol, ibuprofen and caffeine in pharmaceuticals by chemometric approaches using UV spectrophotometry has been reported as a simple alternative to using separate models for each component. Spectra of paracetamol, ibuprofen and caffeine were recorded at several concentrations within their linear ranges and were used to compute the calibration mixture between wavelengths 200 and 400 nm at an interval of 1 nm in methanol:0.1 HCl (3:1). Partial least squares regression (PLS), genetic algorithm coupled with PLS (GA-PLS), and principal component-artificial neural network (PC-ANN) were used for chemometric analysis of data and the parameters of the chemometric procedures were optimized. The analytical performances of these chemometric methods were characterized by relative prediction errors and recoveries (%) and were compared with each other. The GA-PLS shows superiority over other applied multivariate methods due to the wavelength selection in PLS calibration using a genetic algorithm without loss of prediction capacity. Although the components show an important degree of spectral overlap, they have been determined simultaneously and rapidly requiring no separation step. These three methods were successfully applied to pharmaceutical formulation, capsule, with no interference from excipients as indicated by the recovery study results. The proposed methods are simple and rapid and can be easily used in the quality control of drugs as alternative analysis tools.

Simultaneous spectrophotometric estimation of valdecoxib and tizanidine HCl in mixture

Two simple, rapid, accurate and economical methods have been developed for the estimation of valdecoxib and tizanidine HCl in the mixture. Valdecoxib has an absorbance maximum at 243 nm and tizanidine HCl has two absorbance maxima at 228 nm and 320 nm in methanol:0.1 M HCl (1:1) mixture. The linearity was observed in the concentration range 5-30 µg/ml for valdecoxib and 2-20 µg/ml for tizanidine. First method is based on the simultaneous equations and second method is based on Q absorbance ratio. Absorbances at 243 nm and 228 nm were selected for simultaneous equations method. Absorbance at isoabsorptive point 280.4 nm and at 243 nm, the λmax of valdecoxib were selected for absorbance ratio method. These methods were validated statistically. The recovery studies confirmed the accuracy of the proposed methods.