Selective Spectrophotometric Method Research Articles

Spectrophotometric determination of nifedipine in pharmaceutical formulations, serum and urine samples via oxidative coupling reaction

Two rapid, simple, sensitive and selective spectrophotometric methods have been developed for the quantitative estimation of nifedipine in pharmaceutical formulations and different human body fluids (serum and urine). The proposed methods are based on the reduction of the nitro group to amino group of the drug. The resulting amine was then subjected to proposed methods. Method A is based on the oxidation followed by coupling of nifedipine with 3- methyl-2-benzothiazolinone hydrazone (MBTH) in presence of ferric chloride (FeCl3) to form green colored chromogen at 685nm. Method B is based on the formation of oxidative coupling reaction between the corresponding drug and brucine – NaIO4 to form violet colored chromogen at 546nm. The procedures described were applied successfully to the determination of the compound in their dosage forms and body fluids. The results showed that the proposed procedures compared favorably with reference method are satisfactory sensitive, accurate and precise. The optical characteristics such as Beer’s law limits, molar absorptivity, Sandell’s sensitivity and various statistical data are reported. The results of the analysis for the two methods have been validated statistically and by recovery studies.

First Order Derivative Spectrophotometric Determination of Thorium in Geological Samples Using Diacetylmonoxime p-hydroxybenzoylhydrazone

A simple, selective and sensitive spectrophotometric method has been developed for the determination of trace amounts of thorium using a newly synthesised reagent diacetylmonoximep-hydroxybenzoylhydrazone (DMPHBH) in the presence of Triton X-100. The molar absorptivity and Sandell’s sensitivity of the coloured species at pH 4.4 were found to be 4.20 x 104 L mol-1 cm-1 and 5.5 ng cm-2, respectively. Beer’s law is obeyed in the range 0.35 -3.8 mg mL-1 of thorium(IV) at 410 nm. The stoichiometry of the complex was found to be 1:2 (Th(IV): DMPHBH). A highly selective first order derivative spectrophotometric method for the determination of thorium in the presence of uranium is also reported. The detection limit and quantitation limit of first order derivative spectrophotometry were found to be 0.03 and 0.11 mg mL-1, respectively. The developed procedure has been successfully applied for the trace level determination of thorium in rock samples and synthetic mixtures.

A new kinetic spectrophotometric method for the determination of major metabolite of heroin in biological samples

Abstract This study describes a simple, rapid and selective catalytic kinetic spectrophotometric method for the determination of 6-monoacetylmorphine (6-MAM) as major metabolite of heroin in biological samples. The method is based upon the catalytic effect of 6-MAM on the oxidation of Janus Green by bromate in acid media. The reaction was followed spectrophotometrically by measuring the decrease in absorbance of Janus Green at 618 nm. The dependence of sensitivity on the reaction variables was studied. Under optimum conditions, two linear calibration curves over the range 0.1–1.0 μg mL −1 and 1.0–34.0 μg mL −1 of 6-MAM were obtained. The detection limit was 1.2 × 10 −2 μg mL −1 of 6-MAM. The relative standard deviations for six replicate determinations of 0.8 and 5.0 μg mL −1 of 6-MAM were 1.4 and 1.1% respectively. The effect of various species commonly associated with heroin in real samples was also investigated. The proposed method was successfully applied in human urine and serum samples with satisfactory results.

TWO SELECTIVE SPECTROPHOTOMETRY METHODS FOR THE DETERMINATION OF THIORIDAZINE HYDROCHLORIDE IN TABLETS AND IN BIOLOGICAL FLUIDS

ABSTRACT Two simple, rapid and selective spectrophotometric methods have been developed for the analysis of the psychoactive drug thioridazine HCl (TRH) in tablets and in biological fluids. The first method is based on the oxidation of TRH by a known excess of N- bromosuccinimide (NBS), followed by the determination of unreacted oxidants by measuring the decrease in absorbance of two different dyes; amaranth (AM) and methylene blue (MB) at a suitable l max 520 and 660 nm, respectively. Beer-Lambert plots showed good correlation in the concentration ranges of 0.8-4.8 and 0.8-5.6 µg/ml for AM and MB methods, respectively. The second method is based upon the formation of an ion-pair complexes (1: 1) with the acidic sulphonphthalein dyes bromophenol blue (BPB) and bromothymol blue (BTB). The formed complexes were extracted into methylene chloride and their absorbance was measured at 405 and 408 nm for BPB and BTB, respectively. Beer’s law was obeyed with a good correlation coefficient (r = 0.9995–0.9989) in the concentration ranges of 4 – 24 µg/ml for both BPB and BTB methods, respectively. All measurements of the two procedures are carried out in an acidic medium at room temperature. Optimizations of the different experimental conditions are described for both methods. The two methods have been successfully applied to the determination of thioridazine HCl in pharmaceutical, serum and urine samples and average recoveries are in the range of 98.12 – 102.55%. Analytical results obtained with this novel method are satisfactory.

Simple and Rapid Spectrophotometric Determination of Propranolol Hydrochloride as Base Form in Pharmaceutical Formulation through Charge Transfer Complexation

Two simple and selective spectrophotometric methods are described for the determination of propranolol hydrochloride (PPH) as base form (PPL) in bulk drug, and in tablets and capsules. The methods are based on the molecular charge-transfer complexation of propranolol base (PPL) with either 2,4,6-trinitrophenol (picric acid; PA) or 2,4-dinitrophenol (DNP). The yellow colored radical anions formed on dissociation, are quantitated at 425 nm (PA method) or 415 nm (DNP method). The assay conditions were optimized. Beer\\\'s law is obeyed in the concentration ranges 2.4-42.0 μg ml-1 in PA method and 9.0-126.0 μg ml- 1in DNP method, with respective molar absorptivity values of 4.97 × 103 and 1.66 × 103 l mol-1 cm-1. The reaction stoichiometry in both methods was evaluated by Job’s method of continuous variations and was found to be 1:1 (PPL:PA, PPL:DNP). The developed methods were successfully applied to the determination of PPL in pure form and commercial tablets/capsules with good accuracy and precision. Statistical comparison of the results was performed using Student\\\'s t-test and F-ratio at 95% confidence level and the results showed no significant difference between the reference and proposed methods with regard to accuracy and precision. Further, the accuracy and reliability of the methods were confirmed by recovery studies via standard addition technique

Spectrophotometric Determination of Thioridazine Hydrochloride in Tablets and Biological Fluids by Ion-Pair and Oxidation Reactions

Two simple, sensitive and selective spectrophotometric methods have been described for the determination of the psychoactive drug, thioridazine HCl in tablets and in biological fluids. The first method is based on the oxidation of thioridazine HCl with measured excess of KMnO4under acidic conditions followed by the determination of unreacted oxidant using indigo carmine and methyl orange. The second method is based on the formation of ion-pair complexes with the acidic sulphophthalein dyes such as bromocresol green and bromocresol purple at pH 1.8 of KCl-HCl buffer. The formed complexes were extracted into methylene chloride and their absorbance was measured at 412 nm. Optimizations of the different experimental conditions are described for both methods. The proposed methods were successfully applied for determination of the drug in tablets and biological fluids with good accuracy and precision. Statistical comparison of the results with those obtained by an official method showed good agreement and indicated no significant difference in accuracy and precision.

Direct determination of nitrate in small volumes of natural surface waters using a simple spectrophotometric method

A simple, sensitive and selective spectrophotometric method is proposed for rapid and direct determination of nitrate in small volumes of natural surface waters (maximum 2.0 ml), and optimal experimental conditions, along with other analytical parameters, have been evaluated. The method is based on the reaction between nitrate and chromotropic acid, in concentrated sulfuric acid media (95%), when a yellow colored product is obtained. The visible spectra of this reaction product, recorded against a blank solution, show a maximum at 412 nm, and the absorbance remains stable for at least 24 h. The method allows the nitrate determination over the range 0.50–11.00 mg l-1, with a molar absorptivity of 3.837×104 l mol-1 cm-1 and a detection limit of 0.12 ppm. The interferences caused by several common ions (K+, NH4+, Na+, Ca2+, Mg2+, Al3+, Cl-, NO2-, HCO3-, CO32-, H2PO4-, HPO42-) which are present in most natural surface waters were determined. The validation of the spectrophotometric method was done by comparing the nitrate content obtained by the proposed method with those obtained by using the standard method with sulphosalicylic acid, for all studied types of waters (drinking water, tap water, river water and sea water). The results show that the proposed method can be successfully used for direct determination of nitrate in small volumes of natural surface waters (maximum 2.0 ml). The main advantage of this method is that the colored reaction product appears immediately after mixing the reagents; other intermediary steps are not necessary.

Spectrophotometric Determination of Mycophenolate Mofetil as Its Charge-Transfer Complexes with Two π-Acceptors.

Two simple, selective, and rapid spectrophotometric methods are described for the determination of mycophenolate mofetil (MPM) in pure form and in tablets. Both methods are based on charge-transfer complexation reaction of MPM with p-chloranilic acid (p-CA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in dioxane-acetonitrile medium resulting in coloured product measurable at 520 nm (p-CA) or 580 nm (DDQ). Beer's law is obeyed over the concentration ranges of 40–400 and 12–120 μg mL−1 MPM for p-CA and DDQ, respectively, with correlation coefficients (r) of 0.9995 and 0.9947. The apparent molar absorptivity values are calculated to be 1.06 × 103 and 3.87 × 103 L mol−1 cm−1, respectively, and the corresponding Sandell's sensitivities are 0.4106 and 0.1119 μg cm−1. The limits of detection (LOD) and quantification (LOQ) are also reported for both methods. The described methods were successfully applied to the determination of MPM in tablets. Statistical comparison of the results with those of the reference method showed excellent agreement. No interference was observed from the common excipients present in tablets. Both methods were validated statistically for accuracy and precision. The accuracy and reliability of the methods were further ascertained by recovery studies via standard addition procedure.

Spectrophotometric Determination of Micro Amounts of Albumin Using Zirconium(IV) and Xylenol Orange

Abstract A highly sensitive and selective spectrophotometric method is developed to measure micro amounts of albumin. The proposed method is based on the fact that zirconium(IV)–Xylenol Orange complex fades in the presence of albumin. In the concentration range of 0.1–0.9 µg cm−3, human serum albumin obeys Beer’s law and shows an effective molar absorptivity of 8.4 × 107 dm3 mol−1 cm−1 at 605 nm.

New Method of Synthesis of Calix-4-arenes as Analytical Reagent for Spectrophotometric Determination of Iron (III)

A compound of Calix-4-arenes was prepared, as a sensitive and selective spectrophotometric method was proposed for the rapid determination of Iron (III)in analytical sample, the proposed method was based on the formation blue complex with Calix-4-arenes as a chromogenic reagent that has a highly absorption at λmax 592 nm. The reaction was instantaneous at pH=7.0, the absorbance of complex was stable for about 24hr. Linearity was observed from1.18 -8.0 μg.ml-1 with detection limit of 0.75μg.ml-1. Recovery and relative error values of precision and accuracy of method were found to be R.S.D.% = 0.92%,Re% = 99.45% and Erel = 0.55 % . The nature of complex showed that (Metal : Ligand) ratio was 1:1 at pH=7and the stability constant of ( 0.422x1010 L1.mole-1).The influence of chemical iand physical parameter and are evaluated . The proposed method was applied successfully to determine Fe (III) in analytical sample

Development of an reliable analytical method for synergistic extractive spectrophotometric determination of cobalt(II) from alloys and nano composite samples by using chromogenic chelating ligand

A synergistic simple and selective spectrophotometric method was developed for the determination of cobalt(II) with 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2′,4′-dinitro APTPT] as a chromogenic reagent. The proposed method has been described on the basis of synergistic effective extraction of cobalt(II) in presence of pyridine at pH range 9.5–10.2, showed orange-red coloured ternary complex having molar ratio 1:2:2 (M:L:Py). The equilibrium time is 10 min for extraction of cobalt(III) from organic phase. The absorbance of coloured organic layer in chloroform is measured spectrophotometrically at 490 nm against reagent blank. The Beer's law was obeyed in the concentration range 2.5–15 μg mL −1 of cobalt(II) and optimum concentration range was 5–12.5 μg mL −1 of cobalt(II) and it was evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of cobalt(II)-2′,4′-dinitro APTPT-pyridine complex in chloroform are 1.109 × 10 3 L mol −1 cm −1 and 0.053 μg cm −2, respectively while molar absorptivity and Sandell's sensitivity of cobalt(II)-2′,4′-dinitro APTPT complex in chloroform are 6.22 × 10 2 L mol −1 cm −1 and 0.096 μg cm −2, respectively. The composition of cobalt(II)-2′,4′-dinitro APTPT-pyridine complex (1:2:2) was established by slope ratio method, mole ratio method and Job's method of continuous variation. The ternary complex was stable for more than 48 h. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The method is successfully applied for the determination of cobalt(II) in binary, synthetic mixtures and real samples. A repetition of the method was checked by finding relative standard deviation (R.S.D.) for n = 5 which was 0.15%. The reliability of the method is confirmed by comparison of experimental results with atomic absorption spectrophotometer.

Development of reliable analytical method for extraction and separation of thorium(IV) by Cyanex 272 in kerosene

A simple and selective spectrophotometric method has been developed for the extraction and separation of thorium(IV) from sodium salicylate media using Cyanex 272 in kerosene. Thorium(IV) was quantitatively extracted by 5 × 10−4 M Cyanex 272 in kerosene from 1 × 10−5M sodium salicylate medium. The extracted thorium(IV) was stripped out quantitatively from the organic phase with 4.0 M hydrochloric acid and determined spectrophotometrically with arsenazo(III) at 620 nm. The effect of concentrations of sodium salicylate, extractant, diluents, metal ion and strippants has been studied. Separation of thorium(IV) from other elements was achieved from binary as well as multicomponent mixtures such as uranium(VI), strontium(II), rubidium(I), cesium(I), potassium(I), Sodium(I), lithium(I), lead(II), barium(II), beryllium(II) etc. Using this method separation and determination of thorium(IV) in geological and real samples has been carried out. The method is simple, rapid and selective with good reproducibility (approximately ±2%).

A Practical and Selective Method for the Analysis of Molybdenum in Grade T91 Tube and P91 Pipe Intended for Power Plants

ASME SA-213 T91 tubes and SA-335 P91 pipes were widely used in combined-cycle steam systems due to their greater increased temperature strength and creep behavior. In this paper, a practical and selective spectrophotometric method for the determination of molybdenum in ASME SA-213 T91 tube and SA-335 P91 pipe samples has been presented. This method was based on the chromogenic reaction between molybdenum(V) and sodium thiocyanate. Employing stannous chloride as a reductant, molybdenum(VI) was reduced to molybdenum(V) at the room temperature. The obtained molybdenum(V) formed an orange-red-colored (1:5) ligand complex with thiocyanate. The absorbance of the complex was measured at 470nm, and the molar extinction coefficient is 1.75´104L·mol-1·cm-1. Under the optimum reaction conditions the absorption value was proportional to the concentration of molybdenum in the range of 0.40~1.21%, and the relative standard deviation was less than 3.0%. The proposed method was free from the interference from a large number of analytical important elements and has been applied satisfactorily to the determination of molybdenum in grade T91 tube and P91 pipe samples with the improved accuracy and precision.

A Selective and Sensitive Method for the Determination of Molybdenum in High Grade Pipeline Steels

Pipeline system is the main form of transportation for oil and natural gas. High grade pipeline steel can effectively improve the security of long-distance transportation and to reduce costs, will become the main steel for gas pipeline project. A highly selective and sensitive spectrophotometric method for the determination of molybdenum in high grade pipeline steel has been presented. This method was based on the chromogenic reaction between molybdenum(V) and sodium thiocyanate. Employing stannous chloride as a reductant, molybdenum(VI) was reduced to molybdenum(V) at the room temperature. The obtained molybdenum(V) formed an orange-red-colored (1:5) ligand complex with thiocyanate. The absorbance of the complex was measured at 470nm, and the molar extinction coefficient (e) is 1.75´104L·mol-1·cm-1. Under the optimum reaction conditions the absorption value was proportional to the concentration of molybdenum in the range of 0.11%~0.89% (mass fraction), and the relative standard deviation was less than 3.0%. The proposed method was free from the interference from a large number of analytical important elements and has been applied satisfactorily to the determination of molybdenum in X80 pipeline steel and X70 pipeline steel samples with the improved accuracy and precision.

Direct and selective spectrophotometric method for the determination of vanadium in steel, environmental and biological samples

A simple, direct and selective spectrophotometric method for determination of vanadium is described. The present methodology is based on the strong oxidizing power of vanadium (V). Vanadium (V) selectively oxidizes leucocrystal violet (LCV) to crystal violet in the presence of phosphoric acid. The violet colored dye obtained shows maximum absorbance at 590 nm. Beer's law is obeyed in the concentration range 0.06–0.6 μg ml −1. The molar absorptivity and Sandell's sensitivity are found to be 6.78 × 10 4 l mol −1 cm −1 and 0.0044 μg cm −2, respectively. The proposed method is simple, direct, and sensitive. It has been successfully applied for the determination of vanadium in various environmental, biological and steel samples.

Application of difference spectroscopy to the determination of some pharmaceutically important nitro compounds.

A simple and selective spectrophotometric method for the determination of some pharmaceutically important nitro compounds has been developed. The suggested method depends upon the spectral changes induced by reduction using either Zn/HCl or Zn/NH4Cl. The different experimental parameters were studied and incorporated into the procedure. The mean percentage recovery ranged from 99 to 101. The proposed method was applied to the determination of the studied compounds in dosage forms, and the results obtained were compared favourably with those given with the compendial ones.

Sensitive and selective spectrophotometric assay of gabapentin in capsules using sodium 1, 2‐naphthoquinone‐4‐sulfonate

A simple, sensitive, and selective spectrophotometric method has been developed for the determination of gabapentin (GBP) in capsules. The method is based on the reaction of GBP and sodium 1,2-naphthoquinone-4-sulfonate (NQS) in the presence of Clark and Lubs buffer of pH 11 to form an orange-coloured product which was measured at 495 nm. The parameters that affect the reaction were carefully optimized and under the optimized conditions, linear relationship was obtained in the concentration range of 7.5-75 µg ml(-1) GBP. The molar absorptivity, limits of detection (LOD) and quantification (LOQ) and Sandell sensitivity are also reported. The proposed method was successfully applied to the determination of GBP in capsules with good accuracy and precision and without detectable interference from common excipients. The reliability of the proposed method was further established by parallel determination by the reference method and also by recovery studies. The reaction mechanism is proposed and discussed.

Synergistic extraction and spectrophotometric determination of copper(II) using 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol: Analysis of alloys, pharmaceuticals and biological samples

A simple and selective spectrophotometric method was developed for the determination of copper(II) with 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2′,4′-dinitro APTPT] as a chromogenic reagent. The procedure was based on the synergistic extraction of copper(II) with 2′,4′-dinitro APTPT in the presence of 0.5 mol L −1 pyridine to give green colored ternary complex of a molar ratio 1:2:2 (M:L:Py) in the pH range 8.7–10.5. It exhibits a maximum absorption of colored complex at 445 nm and 645 nm in chloroform against the reagent blank. Beer's law was followed in the concentration range 10–80 μg mL −1 of copper(II) and optimum range of 20–70 μg mL −1 the metal as evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of copper(II)–2′,4′-dinitro APTPT–pyridine complex in chloroform are 0.87 × 10 3 L mol −1 cm −1 and 0.072 μg cm −2, respectively. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The proposed method is rapid, reproducible and successfully applied for the determination of copper(II) in binary and synthetic mixtures, alloys, pharmaceutical formulations, environmental and fertilizer samples. Comparison of the results with those obtained using an atomic absorption spectrophotometer also tested the validity of the method.

Sensitive and Selective Spectrophotometric Determination of Gabapentin in Capsules Using Two Nitrophenols as Chromogenic Agents

Two simple and selective spectrophotometric methods have been proposed for the determination of gabapentin (GBP) in pure form and in capsules. Both methods are based on the proton transfer from the Lewis acid such as 2,4,6-trinitrophenol (picric acid; PA) or 2,4-dinitrophenol (2,4-DNP) to the primary amino group of GBP which works as Lewis base and formation of yellow ion-pair complexes. The ion-pair complexes formed show absorption maximum at 415 and 420 nm for PA and 2,4-DNP, respectively. Under the optimized experimental conditions, Beer's law is obeyed over the concentration ranges of 1.25–15.0 and 2.0–18.0 μg mL−1 GBP for PA and 2,4-DNP methods, respectively. The molar absorptivity, Sandell's sensitivity, detection and, quantification limits for both methods are also reported. The proposed methods were applied successfully to the determination of GBP in pure form and commercial capsules. Statistical comparison of the results was performed using Student's t-test and F-ratio at 95% confidence level, and there was no significant difference between the reference and proposed methods with regard to accuracy and precision. Further, the validity of the proposed methods was confirmed by recovery studies via standard addition technique.

Spectrophotometric and spectrofluorimetric determination of some drugs containing secondary amino group in bulk drug and dosage forms via derivatization with 7-Chloro-4-Nitrobenzofurazon

Sensitive and selective spectrophotometric and spectrofluorimetric methods have been developed for determination of some drugs such as Pramipexole, Nebivolol, Carvedilol, and Eletriptan, which commonly contain secondary amino group. The subject methods were developed via derivatization of the secondary amino groups with 7-Chloro-4-Nitrobenzofurazon in borate buffer where a yellow colored reaction product was obtained and measured spectrophotometrically or spectrofluorimetrically. Concentration ranges were found as 2.0 to 250 μg mL-1 and 0.1 to 3.0 μg mL-1, for spectrophotometric and spectrofluorimetric study, respectively. The described methods can be easily applied by the quality control laboratories in routine analyses of these drugs in pharmaceutical preparations.