Three simple spectrophotometric methods for the determination of sulphinpyrazone

Three simple and sensitive spectrophotometric methods for the determination of sulphinpyrazone (SP) in bulk samples and pharmaceutical formulations are described. They are based on the oxidation of sulphinpyrazone with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with metol-isonicotinic acid hydrazide (method A, lambda(max): 620 nm); by the reduction of Folin-Ciocalteu reagent (method B, lambda(max) 770 nm); or by the formation of a chloroform-soluble, coloured ion-association complex between the drug and Methylene Violet (MV) at pH 7.0 (method C, lambda(max) 545 nm).     

Spectrophotometric methods for the determination of prazosin hydrochloride in tablets

Four simple and sensitive methods for the assay of prazosin hydrochloride (PRH) are developed. These methods are based on the formation of coloured species by treating it either with excess N-bromosuccinimide (NBS) and determining the unconsumed NBS with p-N-methyl aminophenol sulphate (metol)-sulphanilamide (SA) reagent (method A, lambda(max) 520 nm): with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of eerie ammonium sulphate (CAS) (method B, lambda(max) 620 nm) or with acidic dyes such as orange-II (O-II) (method C, lambda(max) 490 nm) and alizarin violet 3B (AV-3B) (method D, lambda(max) 570 nm) under the specified experimental conditions. Regression analysis of Beer's law plot showed good correlation in the concentration range of 1.0-10.0, 2.5-25.0, 1.0-17.5 and 2.5-30.0 mug ml for methods A, B, C and D respectively.     

Utility of oxidation-reduction reaction for the determination of ranitidine hydrochloride in pure form,in dosage forms and in the presence of its oxidative degradates

Three simple, accurate and sensitive colorimetric methods (A, B and C) for the determination of ranitidine HCl (RHCl) in bulk sample, in dosage forms and in the presence of its oxidative degradates are described. The first method A is based on the oxidation of the drug by N-bromosuccinimide (NBS) and determination of the unreacted NBS by measurement of the decrease in absorbance of amaranth dye (AM) at a suitable lambda(max)=520 nm. The methods B and C involve the addition of excess Ce(4+) and determination of the unreacted oxidant by decrease the red color of chromotrope 2R (C2R) at a suitable lambda(max)=528 nm for method B or decrease the orange pink color of rhodamine 6G (Rh6G) at a suitable lambda(max)=526 nm for method C. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.2-3.6, 0.1-2.8 and 0.1-2.6 microg ml(-1) for methods A, B and C, respectively. The apparent molar absorptivity. Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.3-3.4, 0.2-2.6 and 0.2-2.4 microg ml(-1) for methods A, B and C, respectively. Analyzing pure and dosage forms containing RHCl tested the validity of the proposed methods. The relative standard deviations were 相似文献   

A rapid spectrophotometric assay of some organophosphorus pesticide residues in vegetable samples

A rapid and sensitive spectrophotometric method for the determination of some organophosphorus insecticides, i.e. malathion, dimethoate and phorate is described. It is based on the oxidation of organophosphorus pesticide with slight excess of N-bromosuccinimide (NBS) and the unconsumed NBS is determined with rhodamine B (lambda max: 550 nm). Beer's law is obeyed in the concentration range 0.108-1.08, 0.056-0.56 and 0.028-0.28 microg mL(-1) for malathion, phorate and dimethoate, respectively. The method has been successfully applied for the determination of organophosphorus pesticide residues in various vegetable samples.     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Bioluminescence color determinants of Phrixothrix railroad-worm luciferases: chimeric luciferases, site-directed mutagenesis of Arg 215 and guanidine effect

Chimeric proteins were produced using the green light-emitting luciferase of Phrixothrix vivianii (PxGr: lambda max = 548 nm) and the red light-emitting luciferase of Phrixothrix hirtus (PxRe: lambda max = 623 nm). Constructs containing residues 1-344 of the red light-emitting luciferase with residues 345-545 of the green light emitting one emitted red light (PxReGr; lambda max = 613 nm), while the reverse emitted green light (PxGrRe; lambda max = 552 nm). From these results we conclude that the region 1-344 determines the color of bioluminescence (BL) in railroad-worm luciferases, and that residues above 344 are not involved. The substitution R215S in the green light-emitting luciferase (PxGr) resulted in a approximately 40 nm redshift on the BL spectrum (lambda max = 585 nm) and an associated decrease of activity, whereas the same mutation in PxRe luciferase had little effect. Guanidine was shown to cause blueshifts in the BL spectra and stimulate the activity of the red-emitting luciferases (from lambda max = 623 to lambda max = 600 nm) and in PxGr R215S (from lambda max = 585 to lambda max = 560 nm) mutant luciferase, but not in the green-emitting luciferases, suggesting that guanidine can simulate positively charged residues involved in BL color determination.     

Spectrophotometric methods for the determination of tolnaftate

Two simple and sensitive visible spectrophotometric methods (methods A and B) for the determination of tolnaftate in bulk samples and formulations are described. Method A (lambda(max) 490 nm) involves the reaction of tolnaftate with 2,6-dichloroquinone-4-chlorimide (DCQC: Gibb's reagent), while method B (lambda(max) 530 nm) is based on a similar reaction of the drug with p-N,N-dimethylphenylene diamine in the presence of chloramine-T. Both these methods are applicable to pure samples as well as formulations of the drug.     

Determination of doxorubicin hydrochloride by visible spectrophotometry

Four simple and sensitive visible spectrophotometric methods (A-D) have been described for the assay of doxorubicin hydrochloride either in pure form or in pharmaceutical formulations. Method A was developed based on oxidation of the drug with Fe(III) to produce Fe(II), which subsequently reacts with 1.10-ortho-phenanthroline to form a red colored complex (lambda(max): 510 nm) at pH 4.6. Method B involves the reduction of Folin-Ciocalteu (F-C) reagent by the drug and the reduced species formed possesses a characteristic intense blue color (lambda(max): 770 nm). In methods C and D. oxidation of the drug with periodate at specified experimental conditions yields formaldehyde and dialdehyde, which in turn react either with 3-methyl-2-benzothiazolinone hydrazone hydrochloride to form an intensely brilliant blue cationic dye (lambda(max): 620-670 nm. method C) or by condensation with phenylhydrazine hydrochloride (PHH) to form orange-red colored product (lambda(max): 510 nm, method D) in the presence of potassium ferricyanide. All of the variables have been optimized and the reaction mechanisms presented. The concentration measurements are reproducible within a relative standard deviation of 1.0%.     

Multivariate spectrofluorimetry of ultra trace zirconium(IV) and hafnium(IV) assisted by several chemometrics methods

In the presence of sodium lauryl sulfate (SLS), an anionic surfactant, highly sensitive molecular fluorescence reactions occur between Zr(IV), Hf(IV) ions and quercetin (3, 3', 4', 5, 7-pentahydroxyflavone) in acidic medium to form stable ternary micellar ion-association complexes. Their lambda(ex(max))/lambda(em(max)) values are 435.0/497.9 and 435.0/492.0 nm, respectively, indicating their heavily overlapping fluorescence excitation and emission spectra. The linear ranges of their regression calibration curves are 0 to 0.20 and 0 to 0.12 mg l(-1), respectively, with 0.5 ng ml(-1) for all of sensitivities. The multivariate spectrofluorimetry of ultra trace or trace Zr(IV) and Hf(IV) without separation was performed using a partial least squares (PLS) algorithm and other algorithms. The optimum PLS computation conditions are wavelength point number of 21 and corresponding wavelength range from 450 to 540 nm oriented from lambda(em) 495 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed lambda(ex)of 435.0 nm with an optimum calibration sample number of 12, and respective optimum abstracted factor numbers of 4 and 5. It was concluded that accuracy and precision of the determination results obtained for simulation and real soil samples were poor for LP-M, LP-P, OLS-P, KF-P, and TFA-P algorithms, moderate for OLS-M, KF-M, and TFA-M algorithms, and good for PLS algorithm.     

Four spectrophotometric methods for determination of nitrofurazone in pharmaceutical formulations

Four simple and sensitive visible spectrophotometric methods (A-D) for the determination of nitrofurazone in bulk samples and pharmaceutical formulations are described. They are based on the formation of colored species by treating either its reduction product with 3-methylbenzothiazolin-2-one hydrazone in the presence of ferric chloride (method A: _max 600 nm) or its hydrolysis product with thiobarbituric acid (method B: _max 520 nm, 440 nm) or barbituric acid (method C: _max 400 nm) or by oxidizing it with excess N-bromosuccinimide and determining the consumed NBS using metol-isonicotinic acid hydrazide (method D: _max 620 nm).     

Spectrofluorimetric determination of acetaminophen with N-bromosuccinimide

A simple, sensitive, and selective method for determination of acetaminophen based on its oxidation using N-bromosuccinimide (NBS) to produce a highly fluorescent product. Optimization of reaction variables was carried out concerning NBS concentration, pH, temperature, reaction time, and stability time. Under optimal analytical conditions, the fluorescent intensity was measured at lambda emission. 442 nm (excitation at lambda 330 nm). The linearity range is 120-800 ng/mL with lower detection limit of 33.6 ng/mL acetaminophen. The method was applied successfully to the determination of the compound in pharmaceutical preparations, with average recovery of 100.3 +/- 2%. The method was also applied successfully to the determination of the drug in spiked plasma samples, with an average recovery of 101.2 +/- 1%. Interference effects of some compounds, present in combination with acetaminophen, were studied and the tolerance limits of these compounds were determined.     

PHOTOBLEACHING OF MEROCYANINE 540: INVOLVEMENT OF SINGLET MOLECULAR OXYGEN

The purpose of this study was to assess the mechanism of merocyanine 540 (MC540) photobleaching in a liposomal system. Broad based visible irradiation of MC540 in unilamellar dilauroylphosphatidylcholine (DLPC) vesicles resulted in dye bleaching that was strictly O2 dependent. The rate of self-sensitized photobleaching was enhanced in D2O and inhibited by both azide and histidine, consistent with 1O2 intermediacy (Type II chemistry). Supportive evidence for this mechanism was obtained by using a Type II sensitizer, aluminum phthalocyanine tetrasulfonate (AlPcS lambda max = 678 nm). Irradiation of AlPcS and MC540 in DLPC with lambda greater than 630 nm (absorbed only by AlPcS) light resulted in rapid bleaching of MC540, which was stimulated by D2O and inhibited by azide. A rate constant of 10(7) M-1 s-1 was determined for the chemical quenching of 1O2 by MC540. The rate constant for physical quenching of 1O2 by MC540 was estimated to be ca 10(9) M-1 s-1.     

Kinetic spectrophotometric determination of traces of sulfide

A method for the determination of sulfide based on the addition reaction of sulfide with magenta at pH 7 and 25 degrees C is described. The decrease in absorbance of magenta at 540 nm, its lambda(max), over a fixed time is proportional to the concentration of sulfide over the range of 25-2500 ng ml(-1). The limit of detection was found to be 15 ng ml(-1). Ten replicate analysis of a sample solution containing 1.5 mug ml(-1) sulfide gave a relative standard deviation of 0.8%. The effects of various cations and anions on sulfide determination have been reported and procedures for removal of interferences have been described.     

Spectrophotometric methods for the determination of certain catecholamine derivatives in pharmaceutical preparations

Two simple, rapid and sensitive spectrophotometric methods for the determination of catecholamine derivatives (pyrocatechol, dopamine, levodopa and methyldopa) are developed. The first method involves the oxidation of o-dihydroxybenzene derivatives by N-bromosuccinimide followed by oxidative coupling with isoniazid leading to the formation of a red-coloured products of maximum absorbance (lambda(max)=480-490 nm). The second method is based on the formation of green to blue complex (lambda(max)=635-660 nm) between o- dihydroxybenzene derivatives and sodium nitroprusside in the presence of hydroxylamine hydrochloride. All measurements of the two procedures are carried out in an alkaline medium at room temperature. The two methods are successfully applied for the determination of dopamine hydrochloride, levodopa and methyldopa in injections and tablets of pharmaceutical preparation. The common excipients used as additives in pharmaceuticals do not interfere in the proposed methods. The reliability of these methods are established by parallel determination with the reported and official methods.     

Colorimetric determination of isoniazid and its pharmaceutical formulations

Two colorimetric methods for the estimation of isoniazid are developed. The first method depends on coupling of isoniazid with diazotized 1-amino anthraquinone zinc chloride salt (fast red AL salt) to form a red colour (lambda(max) 510 nm). The second one is based on the formation of a green complex (lambda(max) 655 nm) between the acid hydrazide and 2,6-dimethoxy-1,4-benzoquinone (DMBQ). All measurements of the two procedures were carried out in the presence of sodium hydroxide at room temperature (20 +/- 3 degrees C). The two methods are applied for the determination of isoniazid in presence of congenial drugs, vitamins and additives normally encountered with it in pharmaceutical dosage forms. The reliability of these methods was established by parallel determination with the reported and official methods.     

Spectrophotometric determination of drugs in pharmaceutical formulations withN-bromosuccinimide and celestine blue

Simple, sensitive and selective methods are proposed for the spectrophotometric determination of drugs, viz., tetracycline HCl, nifurtimox, ethionamide, propranolol HCl and isonicotinic acid hydrazide, based on their reactivity withN-bromosuccinimide (NBS). The method involves the addition of excess NBS of known concentration in the presence of 0.25M HCl and the unreacted NBS is determined by the measurement of the decrease in the absorbance of the dye celestine blue (_max 540 nm), which was found to be the most suitable of several dyes tested. This method was applied for the determination of drug contents in pharamaceutical formulations and enabled the determination of the drugs in microgram quantities (0.2 to 5 g/ml). Standard deviations were typically 0.5mg per dose (RSD 0.1–1.0%). No interferences were observed from excipients and the validity of the method was tested against reference method. Recoveries were 99.8–101.1%.     

Flow-injection spectrophotometric determination of azithromycin in pharmaceutical formulations using p-chloranil in the presence of hydrogen peroxide.

A flow-injection (FI) spectrophotometric procedure exploiting merging zones is proposed for the determination of azithromycin in pharmaceutical formulations. The method is based on the reaction of azithromycin with tetrachloro-p-benzoquinone (p-chloranil) accelerated by hydrogen peroxide and conducted in a methanol medium, producing a purple-red color compound (lambda(max) = 540 nm). The FI system and the experimental conditions were optimized using a multivariate method. Beer's law is obeyed in a concentration range of 50 - 1600 microg mL(-1) with an excellent correlation coefficient (r = 0.9998). The detection limit and the quantification limit were 6.6 and 22.1 microg mL(-1), respectively. No interference was observed from the common excipients, and the recoveries were within 98.6 to 100.4%. The procedure was applied to the determination of azithromycin in pharmaceuticals with a high sampling rate (65 samples h(-1)). The results obtained by the proposed method were in good agreement with those obtained by the comparative method at 95% confidence level.     

Spectrophotometric determination of bio-active compounds with chloramine-T and gallocyanine

A simple, sensitive and selective method for the spectrophotometric determination of drugs, viz., sulphamethoxazole, tetracycline HCl, amidopyrine, nifurtimox and isoniazid and biologically important amino acids, cysteine, aspartic acid and arginine based on their reactivity with chloramine-T (CAT) is proposed. The method involves the addition of excess CAT of a known concentration in the presence of 0.25 M HCl and the determination of the unreacted CAT by measurement of the decrease in the absorbance of the dye, gallocyanine (lambda(max): 540 nm), the most suitable of several dyes that were tested. This method was applied to the determination of drug contents in pharmaceutical formulations and to the measurement of the aspartic acid content of some protein hydrolysates. The method is useful for the determination of the target compounds in microgram quantities from 0.4-5.6 microg mL(-1) with the exceptions of arginine (1.0-8.0 microg mL(-1)) and nifurtimox (0.8-5.6 microg mL(-1)). Standard deviations were typically 0.5 mg per dose (RSD 0.5-1.2%). No interferences were observed from common excipients in formulations, and detailed interference studies of other amino acids in the determination of cysteine, aspartic acid and arginine are reported. The validity of the method was tested against spectrophotometric and titrimetric reference methods. Recoveries were 99.8-102.1%.     

Determination of ruthenium and osmium in each other's presence in chloride solutions by direct and third-order derivative spectrophotometry

Ruthenium and osmium (up to 20 mug Ru(Os) ml(-1)) can be determined in chloride solutions directly after absorption of RuO(4) and OsO(4) in hydrochloric acid. In 9 M HCl, RuO(4) and OsO(4) are quantitatively converted into RuCl(6)(2-) (lambda(max) = 480.0 nm, epsilon = 4.8 x 10(3) l mol(-1) cm(-1)) and OsCl(6)(2-) (lambda(max) = 334.8 nm, epsilon = 8.4 x 10(3) l mol(-1) cm(-1)) respectively. Osmium does not interfere with the determination of ruthenium in the form of the RuCl(6)(2-) complex by direct spectrophotometry. The absorbance of the obtained solution at lambda(max) = 480.0 nm corresponds only to the concentration of ruthenium. A derivative spectrophotometric method using numerical calculation of absorption spectra of the RuCl(6)(2-) and OsCl(6)(2-) complexes has been developed for the determination of osmium in a mixture with ruthenium. The interfering effect of ruthenium on the determination of osmium can be eliminated by measuring the value of a third-order derivative spectrum of the OsCl(6)(2-) complex at 350.0 nm ("zero-crossing point" of ruthenium). Simple and rapid determination of ruthenium and osmium in a calibration standard solution of the noble metals (Ru, Rh, Pd, Os, Ir, Pt and Au) for plasma spectroscopy using the proposed methods has been achieved.     

Effects of three characteristic amino acid residues of pharaonis phoborhodopsin on the absorption maximum

Phoborhodopsin (pR or sensory rhodopsin II, sRII) or pharaonis phoborhodopsin (ppR or pharaonis sensory rhodopsin II, psRII) has a unique absorption maximum (lambda max) compared with three other archaeal rhodopsins: lambda max of pR or ppR at ca 500 nm and others at 560-590 nm. Alignment of amino acid sequences revealed three sites characteristic of the shorter wavelength-absorbing pigments. The amino acids of these three sites are conserved completely among archaeal rhodopsins having longer lambda max, and are different from those of pR or ppR. We replaced these amino acids of ppR with amino acids corresponding to those of bacteriorhodopsin, Val-108 to Met, Gly-130 to Ser and Thr-204 to Ala. The lambda max of V108M mutant was 502 nm with a slight redshift. G130S and T204A mutants had lambda max of 503 and 508 nm, respectively. Thus, each site contributes only a small effect to the color tuning. We then constructed three double mutants and one triple mutant. The opsin-shifts of these mutants suggest that Val-108 and Thr-204 or Gly-130 are synergistic, and that Gly-130 and Thr-204 work additively. Even in the triple mutant, the lambda max was 515 nm, an opsin-shift only ca 30% of the shift value from 500 to 560 nm. This means that there is another yet unidentified factor responsible for the color tuning.