Determination of molybdenum by extraction of its thiocyanate into ethyl methyl ketone

A simple, sensitive and selective spectrophotometric method for determination of molybdenum is described. A solution containing 100 mug of Mo in 2.5M hydrochloric acid is treated with ascorbic acid and ammonium thiocyanate and after standing for 8 min is shaken with an equal volume of ethyl methyl ketone for 30 sec. The absorbance of the complex is measured at 465 nm against a reagent blank. The complex is stable for 1 hour. There is no interference from Re(VII), SO(2-)(4), Cl(-), CH(3)COO(-), PO(3-)(4), NO(-)(3), C(2)O(2-)(4), citrate or tartrate, and at least 5 mg of U(VI), 10 mg of Cr(III, VI), Th, or Ni, and 20 mg of W(VI) Can be tolerated. Vanadium(V) interferes at the 500 mug level, and fluoride slightly decreases the absorbance.     

Derivative spectrophotometric determination of praseodymium in rare earth mixtures with lomefloxacin

Praseodymium forms a Pr(LMFX)(3) complex with lomefloxacin. In this paper, the absorption spectra of the complex has been investigated by applying conventional and derivative spectrophotometric methods. It was found that lomefloxacin could form a stable complex with praseodymium in the pH 6.5-8.5 media. The absorption intensity of the complex is 4.5-fold more than PrCl(3). Using the second derivative spectra, the sensitivity is 7.4 times higher for Pr than in the normal method (zero derivative spectra). The second derivative spectrophotometry for determination of praseodymium in the presence of other rare earths has been developed. The calibration curves were linear in the range of 3.5-65 mug ml(-1) for Pr. The detection limit is 0.85 mug ml(-1). The method is satisfactory for the determination of praseodymium in mixed rare earths.     

The use of phenylfluorone in the presence of cetylpyridinium chloride and Triton X-100 for the spectrophotometric determination of copper(II) in blood serum

A simple and sensitive spectrophotometric method for determination of copper(II) is based on the formation of a blue coloured complex of Cu(II) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF) in the presence of cetylpyridinium chloride (CP) and Triton X-100, has been developed. Optimum concentrations of PF, CP, Triton X-100 and pH ensuring maximum absorbance were defined. The complex Cu(II)-PF-CP-Triton X-100 shows maximum absorbance at 595 nm with a molar absorptivity value of 9.67x10(4) l mol(-1) cm(-1). The detection limit of the method is 0.028 mug ml(-1). Beer's law is obeyed for copper concentrations in the range 0.04-0.4 mug ml(-1). The studies of the effect of foreign ions on determination of copper, show that the selectivity of the method is poor. The cations of alkali metals and anions Br(-), Cl(-), I(-), F(-), NO(2)(-), NO(3)(-), CH(3)COO(-), SO(4)(2-), S(2)O(3)(2-), PO(4)(3-), citrates (examined in 1000-fold molar excess over copper) do not affect the determination. All cations forming complexes with PF have an interfering effect. The statistical evaluation of the method was carried out for six determinations using 10 mug of Cu and the following results were obtained: the standard deviation, SD=0.042, the confidence interval mu(95)=10.1+/-0.1 mug Cu. The method has been applied for determination of copper in blood serum.     

The separation of W(V) from HCl-KSCN medium on polyurethane foam sorbents for its spectrophotometric determination in steels and silicates

A simple procedure for selective sorption of tungsten is described. The method involves reduction of W(VI) to W(V) with tin(II) chloride (2%, w/v) at 8-9M hydrochloric acid, formation of the W(V)-SCN complex with 0.2M KSCN and its sorption on polyurethane foam within 20 min. The sorbed complex is then eluted with acidified acetone (1 ml of 1M hydrochloric acid and 8 ml of acetone) followed by addition of 1 ml of 0.1M KSCN to the eluent. The method has been applied to the spectrophotometric determination of tungsten in steels and silicates by measuring the absorbance of the eluted solution at 400 nm. Beer's law is obeyed for the range 0.1-12 mug W/ml. Other elements, e.g., Co(III) (50 mug/ml), Cu(II) (10 mug/ml), Ti(IV) (20 mug/ml), V(V) (10 mug/ml) and Mo(VI) (0.5 mug/ml) have no effect on the method. Interference of copper, up to 100 mug/ml has been eliminated by masking with thiourea and that due to molybdenum by prior separation with thioglycollic acid on PUF. The method has been verified with standard samples.     

Separation of antimony(III) with iodide and dithizone by sorption on polyurethane foam from sulphuric acid medium for its spectrophotometric determination in glasses

A method for quantitative separation of antimony(III) by sorption on polyether based polyurethane foam and its spectrophotometric determination has been described. The method involves formation of a pink-red complex of antimony(III) with iodide (0.045M) and dithizone (2.3 x 10(-5)M) in 0.25-0.75M H(2)SO(4) medium, sorption of the complex on polyurethane foam (within 45 min) at room temperature followed by its elution with acidified acetone (acetone containing 0.008% H(2)SO(4)) and spectrophotometric measurement at 507.2 nm ( = 2.56 x 10(4) l mol cm). The method obeys Beer's law from 0.1 to 6.0 mug antimony(III). Tolerance limits of other ions are Co (100 mug), Ni (100 mug), Fe (10 mug), Cu (0.5 mug), Sn (20 mug), Zn (100 mug), As (100 mug), Mn (200 mug), Pb (50 mug), Ti (100 mug), V (50 mug), etc. Interference by iron and copper have been eliminated by treating with KOH prior to the extraction of antimony. The method has been standardized with glass samples spiked with known amounts of antimony and applied to the determination of antimony in various glasses.     

Flow injection spectrophotometric determination of lactic acid in skimmed milk based on a photochemical reaction

A spectrophotometric method for the determination of lactic acid in milk samples based on the use of a photochemical reaction carried out in a Flow Injection System is proposed. Determination is based on the reaction between lactic acid and Fe(III), which is reduced to Fe(II) in the presence of UV light, being the latter made to react with o-phenanthroline. The complex formed between Fe(II) and o-phenanthroline, Fe(o-phen)(3)(2+) (ferroin) is a coloured compound and it can be spectrophotometrically monitored at 512 nm. The method shows a linear range between 0.5 and 50 mug ml(-1) with a limit of detection of 0.16 mug ml(-1). The precision was +/-2.15 expressed as relative standard deviation (n=11) and the sample throughput of 30 samples h(-1). Also non-linear adjustments have been made and validated by ANOVA. The proposed method has been applied to the determination of lactic acid in both synthetic and milk samples.     

Fluorometric determination of reserpine in dosage forms

A rapid and highly sensitive fluorometric procedure has been developed for the routine determination of reserpine, in bulk and in dosage forms. The method is based on the fluorescence induced by oxidation of reserpine with hexa-amminecobalt(III) tricarbonatocobaltate in aqueous acetic acid. The oxidation product exhibits a greenish yellow fluorescence with its emission maximum at around 420 nm. The fluorescence intensity is a linear function of reserpine concentration over the range 0.01-0.24 mug/ml in the solution finally measured. The advantages and disadvantages of the proposed method are discussed, and its applicability to different formulations is demonstrated.     

Flotation-spectrophotometric method for determining palladium by means of the ion-association complex of pentabromopalladate(II) with Rhodamine 6G

The conditions for the formation of a suitable coloured palladium ion-association complex with a basic dye have been examined, and a spectrophotometric method developed for the determination of palladium with bromide and Rhodamine 6G (R6G). Benzene is used for flotation and dimethylformamide for dissolution of the ion-association complex. The molar absorptivity is 3.0 x 10(5) l. mole(-1).cm(-1) at 53Onm. Beer's law is obeyed up to a palladium concentration of 0.3 mug/ml. The composition of the complex is [R6G(+)](3)[PdBr(3-)(5)]. Platinum interferes severely but other platinum metals interfere to a lesser degree. The method has been applied to the determination of traces of palladium in metallic platinum after a preliminary separation with nickel dimethylglyoximate as collector.     

Spectrophotometric and volumetric molybdenum determination with 2,2'-biquinoxalyl

Volumetric and spectrophotometric methods for molybdenum determination based on reaction with 2,2'-biquinoxalyl (2,2'-BQx) in concentrated hydrochloric acid media have been developed. Absorption spectra of the 1,1'-dihydro 2,2'-biquinoxalylene complex shows the most intensive absorption band at 685 nm with molar absorptivity = 3.3 x 10(4) 1. mole(-1). cm(-1). The compound is characterized by good durability to high temperatures and concentrated acid media. The mentioned indicator gives distinct colour changes at the titration end-point. The spectrophotometric method for molybdenum determination is based on the use of the difference in absorbance between the oxidized and reduced forms of 2,2'-BQx. The indicator is reduced with Sn(II) and then part of it is reoxided as a result of addition of Mo(VI). The difference in absorbance between the blank determination and molybdenum sample increases linearily in the concentration range 0.2-2.0 mug Mo/cm(3). 2,2'-Biquinoxalyl was used as an indicator in the volumetric method for the determination of molybdenum concentrations in steel alloy. The interfering ions FE(III) and Cr(III) are easily eliminated as the precipitate of hydroxides. The mineral acids, hydrochloric sulphuric and perchloric acids, have been tested as reaction media.     

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

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

Spectrophotometric determination of molybdenum based on charge transfer complex in PVA medium

A very simple, selective and sensitive method was developed for the spectrophotometric determination of Mo in the presence of W. The method was based on the formation of color charge transfer complex, molybdotungstophosphate-3,3',5,5'-tetramethylbezidine anion, which was solubilized and stabilized in PVA medium. Following the recommended procedure, molybdenum could be determined in the linear range of 0.04-2.5 mug ml(-1) and the molar absorptivity was 1.47x10(4) l mol(-1) cm(-1) at 660 nm. The proposed method had been applied to the determination of trace molybdenum in tungsten ore with satisfactory results.     

Spectrophotometric study of the reaction of zinc with O-hydroxybenzenediazoaminoazobenzene and its application

A highly sensitive and selective procedure for spectrophotometric determination of zinc has been developed. At pH 10.6, in the presence of emulsifier p-octylpolyethyleneglycol phenylether (OP), zinc forms an orange-red complex with o-hydroxybenzenediazoaminoazobenzene (HDAA) which has an absorption maximum at 525 nm. The molar absorptivity is 1.50 x 10(5) 1.mole(-1).cm(-1). Beer's law is obeyed for zinc in the range 0-13 mug/25 ml. The method has been applied to the spectrophotometric determination of trace amounts of zinc in aluminium alloy and in human hair. The proposed method is simple, rapid and accurate. No heating or separation is required.     

A simple simultaneous flow injection method based on phosphomolybdenum chemistry for nitrate and nitrite determinations in water and fish samples

A direct spectrophotometric flow injection method for the simultaneous determination of nitrite and nitrate has been developed. The method is based on the oxidation of a phosphomolybdenum blue complex by the addition of nitrite and the decrease in absorbance of the blue complex is monitored at 820 nm. The injected sample is split into two segments. One of the streams was directly reacted with the above reagent and detected as nitrite. The other stream was passed through a copperised cadmium reductor column where reduction of nitrate to nitrite occurs, and the sample was then mixed with the reagent and passed through the cell of the spectrophotometer to be detected as nitrite plus nitrate. The conditions for the flow injection manifold parameters were optimised by experimental design and the concentration of nitrite and nitrate was determined in the linear range from 0.05 to 1.15 mug ml(-1) nitrite and 0.06 to 1.6 mug ml(-1) nitrate with a detection limit of 0.01 mug ml(-1) for nitrite and 0.025 mug ml(-1) for nitrate. The method is suitable for the simultaneous determination of nitrite and nitrate in fish and water samples with a sampling rate of 25+/-2 sample per hour.     

Spectrophotometric determination of copper(II) at low mug l(-1) levels using cation-exchange microcolumn in flow-injection

A simple spectrophotometric flow-injection method is reported for the highly sensitive and fast determination of copper(II). The method is based on the formation of coloured Cu(II)-(4-methylpiperidinedithiocarbamate)(2) complex when the copper solutions are introduced into a tertiary reagent stream containing 4-methylpiperidinedithiocarbamate. The coloured complex is then selectively monitored at 435 nm. To increase interactions between copper(II) and colour forming reagent and preconcentrate of copper(II), a microcolumn containing strong cation exchange resins was placed between injection manifold and spectrophotometer. The system required no mixing chamber and allowed a sample throughput >60 sample h(-1). The calibration graph was linear in the range 5-100 mug l(-1). The detection limit was <0.5 mug l(-1) for 20 mul injection volume of copper(II) ion solution. The developed method was applied to environmental, copper processing water, and ore samples.     

Photometric determination of aluminium with alizarin fluorine blue

In order to decide whether Alizarin Fluorine Blue (alizarin complexan, 3-amino-methylalizarin-N,N-diacetic acid) is a suitable reagent for the spectrophotometric determination of aluminium, values of the stability constants for some reactions of this reagent with aluminium(III) and iron(III) have been determined spectrophotometrically in a medium containing 20 % dioxan and 80 % water at ionic strength 0.1. The values of the constants that were determined are log K(Al)(AlHL) = 14.3, log K(2Al)(Al2L) = 25.3 and log K(Fe)(FeHL) = 19.6. These results were employed in the design of a method for the spectrophotometric determination of aluminium in the presence of iron and titanium. The Sandell sensitivity is 0.01 mug/cm(2) and the coefficient of variation for 34 determinations was 0.9 %.     

Spectrophotometric methods for the determination of tamoxifen citrate

Three simple and sensitive spectrophotometric methods for the determination of tamoxifen citrate have been developed. They are based on the formation of an ion-association complex between the drug and a dye, Erioglaucine A, which is extractable into chloroform and has an absorption maximum at 625 nm (method A), oxidation with excess potassium permanganate and the determination of unconsumed permanganate using Fast Green FCF (method B), or by the formation of a coloured cobalt thiocyante coordination complex which is extracted into benzene and measured at 635 nm (method C). Beer's law limits for methods A, B, and C are 0.5-3.0 mug ml(-1), 1.0-6.0 mug ml(-1) and 100-500 mug ml(-1), respectively. No interference was observed from tableting additives and the applicability of the methods was examined by analysing tablets containing tamoxifen. The quantities determined were 99.0-100.03% of the exptected values.     

Spectrophotometric determination of Mo(VI) in steel using a homogeneous ternary solvent system after single-phase extraction

An alternative procedure for the determination of Mo(VI) with thiocyanate is proposed. According to this procedure, Mo(VI) is extracted with alpha-benzoinoxime by single-phase extraction in a water/ethanol/chloroform homogeneous ternary solvent system at a nominal pH of 2 and then is spectrophotometrically determined, after separation from the matrix in a similar solvent mixture. The determination is performed by forming a homogeneous phase using the solvent containing the extracted metal as one of the components of the reactional solvent system, eliminating the time-consuming metal complex destruction step. Under these experimental conditions, the calibration graph is linear up to 8.00 mug ml(-1), according to the equation A=0.005+0.143C(Mo(VI)) (r(2)=0.9999). Using the experimental conditions described, the absorbance readings are stable for periods up to 18 h. The interference of the most common interfering species for this method can be prevented by adding Fe(2+) and H(2)PO(4)(-) to the solvent system prior to the extraction step. The accuracy of the proposed method was evaluated by comparing with standard samples determined by atomic absorption measurements with background correction.     

Spectrophotometric study of the determination of copper with ammonium 1-pyrrolidinecarbodithioate

A new spectrophotometric method for the determination of traces of copper has been developed. The method is based on the formation of a stable 1:2 complex of copper(II) and 1-pyrrolidinecarbodithioate and the isolation of this complex by extraction into chloroform. The absorbance is measured at either 269 nm or 435 nm. The detection limit is 0.03 mug, of copper per ml for absorbance measurements at 435 nm.     

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.     

A comparative study on various spectrometries with thin layer chromatography for simultaneous analysis of drotaverine and nifuroxazide in capsules

Three spectrophotometric methods including Vierordt's method, derivative, ratio spectra derivative, and thin layer chromatography (TLC)-UV densitometric method were developed for simultaneous determination of drotaverine HCl (DRT) and nifuroxazide (NIF) in presence of its impurity, 4-hydroxybenzohydrazide (4-HBH). In Vierordt's method, (E(1 cm)(1%)) values were calculated at 227 and 368 nm in the zero-order spectra of DRT and NIF. By derivative spectrophotometry, the zero-crossing method, drotaverine HCl was determined using the second derivative at 245 nm and the third derivative at 238 nm, while nifuroxazide was determined using the first derivative at 399 nm and the second derivative at 411 nm. The ratio spectra derivative spectrophotometry is basedon the measure of the amplitude at 459 nm for DRT and at 416 nm for NIF in the first derivative of the ratio spectra. Calibration graphs of the three spectrophotometric methods were plotted in the range 1-10 mug/ml of DRT and 2-20 mug/ml of NIF. TLC-UV densitometric method was achieved on silica gel plates using ethyl acetate : methanol : ammonia 33% (10 : 1 : 0.1 v/v/v) as the mobile phase. The Rf values were 0.74, 0.50, 0.30+/-0.01 for DRT, NIF and 4-HBH, respectively. On the fluorescent plates, the spots were located by fluorescence quenching and the densitometrical area were measured at 308 and 287 nm with linear range 0.2-4 mug/spot and 0.6-12 mug/spot for DRT and NIF, respectively. The proposed methods have been successfully applied to the commercial pharmaceutical formulation without any interference of excipients. Mean recoveries, relative standard deviations and the results of the proposed methods were compared with those obtained by applying the alternate methods.