Spectrophotometric determination of gallium(III) with carminic acid and hexadecylpyridinium chloride

A Spectrophotometric method is proposed for determining dipyridamole in pure form and in pharmaceutical preparations. Chromotrope 2B was used as a charge-transfer complex forming agent with absorption maximum 40 nm red shifted relative to the chromotrope 2B itself. The variables affecting the formation of the C.T. complex were studied and optimized. Linear calibration graphs were obtained up to 60 g ml^–1 at room temperature. The method was found to be accurate, precise and can be successfully used for authentic and pharmaceutical preparations in the working range up to 600 g.A conductimetric method using phosphotungstic acid as ion-associate forming agent is proposed. The relative average error is 1–2%. Water-ethanol (12) mixture was used as solvent. Excellent recoveries and low standard deviations were obtained. Working ranges are 40–260 mg and 35–110 mg for pure dipyridamole and tablets, respectively.On leave from Department of Chemistry, Faculty of Science, Allepo University, Allepo, Syria     

Dissociation quotients of malonic acid in aqueous sodium chloride media to 100°C

The first and second molal dissociation quotients of malonic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. The hydrogen ion molality of malonic acid/bimalonate solutions was measured relative to a standard aqueous HCl solution from 0 to 100°C over 25° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and available literature data were treated in the all anionic form by a seven-term equation. This treatment yielded the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: logK _1a =-2.852±0.003, H _1a ^/o =0.1±0.3 kJ-mol^–1, S _1a ^o =–54.4±1.0 J-mol^–1-K^–1, and C _p,1a ^o =–185±20 J-mol^–1-K^–1. Measurements of the bimalonate/malonate system were made over the same intervals of temperature and ionic strength. A similar regression of the present and previously published equilibrium quotients using a seven-term equation yielded the following values for the second acid dissociation equilibrium at 25°C: logK_2a=–5.697±0.001, H _2a ^o =–5.13±0.11 kJ-mol^–1, S _2a ^o =–126.3±0.4 J-mol^–1-K^–1, and C _p,2a ^o =–250+10 J-mol^–1-K^–1.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.     

Assay of cisapride in pharmaceutical formulations by visible spectrophotometry

Three spectrophotometric methods (A-C) for the assay of cisapride (CPD) in pure and dosage forms are described. Method A is based on the oxidative coupling reaction of CPD with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ferric chloride to form a coloured species (_max; 565 nm.) Method B is based on the oxidation of CPD with Fe (III) and subsequent chelation of Fe(II) to form a coloured complex with 1,10-phenanthroline (_max: 520 nm). Method C is based on the formation of a coloured charge-transfer complex between CPD and chloranilic acid (_max; 555 nm). Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2.0–32.0, 0.4–6.4 and 25.0–450.0 g/ml for methods A,B and C, respectively. The validity of the proposed methods was tested by analysing pharmaceutical dosage forms containing CPD and the relative standard deviations were within 1.0%     

Spectrophotometric determination of 6-aminopenicillanic acid using bromophenol blue and bromothymol blue

Two simple, selective and sensitive spectrophotometric methods are described for the determination of 6-aminopenicillanic acid (6-APA). The methods are based on the reaction of 6-APA with either bromophenol blue (BPB) or bromothymol blue (BTB), to give orange-red and green species, respectively. The coloured products are quantified spectrophotometrically at 625 and 616 nm for BPB and BTB, respectively. The optimization of the different experimental conditions is described. No interferences from different -lactams and common degradation products were observed in the determination of 6-APA using BTB, while flucloxacillin, dicloxacillin, adrenaline, vitamin C, urea and common degradation products in any percentage interfere on using BPB only. The BTB method was better than the BPB method, because of its wider range of determination (0.4–20 g ml^–1 vs. 0.4–7.2 g ml^–1 on using BPB), higher molar absorptivity and Sandell sensitivity (3.27 × 10³l mol^–1 cm^–1 and 0.099 g cm^–2 vs. 2.82 × 10³lmol^–1 cm^–1 and 0.115 g cm^–2), greater stability (3 and 10 days on using BTB and BPB, respectively) and better selectivity. The results were compared with those given by the Official United States Pharmacopeial XXI method.     

2-(2-Thiazolylazo)-pcresol (TAC) as a reagent for the spectrophotometric determination of titanium (IV)

The reaction between titanium(IV) and 2-(2-thiazolylazo)-p-cresol-(TAC) in aqueous methanol media at apparent pH 4.0–5.6 results in a intensely coloured complex that is stable for at least 2 h. The combining ratio is 1 1 cation TAC. Beer's law is obeyed up to 5.0 g/ml titanium(IV) at 580 nm. The apparent molar absorptivity at 580 nm is 9.82.10³ l.mole^–1.cm^–1 and the detection limit obtained was 5 ng/ml titanium (IV). A spectrophotometric method for the simultaneous determination of titanium and iron with TAC is proposed.     

Heterogeneous catalytic oxidation of chromotrope 2B with H2O2 and metal complexes supported on aluminum oxide hydroxide as catalyst

The heterogeneous catalytic oxidation of Chromotrope 2B (C2B) dye with H₂O₂ and the aluminum oxide hydroxide (AlOOH) modified with ammonia complexes of Cu^II, Co^II, Ni^II, and Cr^III (AlOOH/[Mⁿ⁺(amm)_m]) as catalysts were studied. The AlOOH/[Cu^II(amm)₄] is the most efficient catalyst and therefore it was chosen as the potential catalyst for the oxidative degradation of C2B in an aqueous solution. The AlOOH/[Cu^II(amm)₄] was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM), techniques. The rate of reaction was dependent on the type of the metal complex supported on the AlOOH, initial concentration of the dye and H₂O₂, catalyst dose, pH, the concentration of NaCl, and temperature. The catalytic activity of the AlOOH/[Mⁿ⁺(amm)_m] according to the kind of metal ion decreased in the order: Cu^II > Co^II > Cr^III > Ni^II. Other catalysts consisting of the AlOOH supported with Cu^II complexed with ethylenediamine, ethanolamine, 1,3 propanediamine, and 1,4 butanediamine, (AlOOH/[Cu^II(amine)_m]), were also investigated. The activity of the (AlOOH/[Cu^II(amine)_m]) as catalyst according to the type of ligand followed the order: 1,4 butanediamine > 1,3 propanediamine > ethanolamine > ethylenediamine > ammonia. The reaction rate increased with increasing the catalyst dose, concentration of H₂O_2, C2B, and NaCl, pH, and temperature. Since the reusability results for the AlOOH/[Cu^II(amm)₄] revealed good stability over seven cycles, it can thus be considered a promising and cost-effective catalyst for the removal of harmful dyes from wastewater.     

Spectrophotometric determination of clozapine in pharmaceuticals

New Spectrophotometric methods for the assay of clozapine (CZP) in pure and dosage forms are described. Method A is based on the oxidative coupling reaction of CZP with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ceric ammonium sulphate to form a coloured species (_max 570 nm). Method B is also based on the oxidative coupling reaction of CZP withP-,N,N-dimethylpheny-lenediamine dihydrochloride (DMPD) in the presence of sodium hypochlorite to form a coloured species (_max 690 nm). Method C is based on the formation of coloured charge-transfer complex between CZP and chloranilic acid (_max 540 nm). Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2–25, 10–120 and 15–300 g/ml for methods A, B and C, respectively. The validity of the proposed methods was tested by analysing pharmaceutical dosage forms containing CZP and the relative standard deviation values were within 1.0%.     

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%.     

C nucleosides II. Preparation of 2-β-d-ribofuranosylbenzothiazole, 5-β-D-ribofuranosyltetrazole,and 5-β-glycosyl-1,3,4-oxadiazole derivatives

The conversion of 5--D-ribofuranosyl cyanides to the corresponding 2--ribofuranosylbenzothiazoles (under the influence of 2-aminothiophenol) and to 5--glycosyltetrazoles (by reaction with sodium azide and ammonium chloride) is described. It is shown that acylation of the latter structures with acetic anhydride or benzoyl chloride is a convenient method for the synthesis of 5--glycosyl-1,3,4-oxadiazoles.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 893–896, July, 1978.     

A sensitive and highly selective extractive spectrophotometric method for the determination of palladium

Summary A Sensitive and Highly Selective Extractive Spectrophotometric Method for the Determination of Palladium Palladium forms an anionic chelate with 4-(2-pyridylazo)resorcinol (PAR, H₂R) which is extractable with xylometazolonium cation (XMH) into chloroform in the pH range 7.2–7.8 giving an intensely pinkish red coloured solution. The coloured species exhibits maximum absorbance at 520 nm with molar absorptivity 3.34×10⁴1·mole^–1·cm^–1 and obeys Beer's law in the range 0.8–5.30g/ml of palladium. The composition of the extracting species is found to be 111 for Pd(II)PARXMH. Large concentrations of EDTA and oxalate have no interference in the spectrophotometric determination of palladium by this procedure. Based on this a highly selective and sensitive method for the determination of palladium in the presence of Zn(II), Cd(II), Hg(II), Fe(III), Mn(II), Co(III), Mo(VI), Ru(IV), Sb(III), Al(III) is described. The application of this method for the determination of palladium in synthetic mixtures corresponding to the composition of jewel alloy and stibiopalladinite mineral is also demonstrated.     

Extraction and spectrophotometric determination of titanium(IV) withN 1-hydroxy-N 1,N 2-diphenylbenzamidine and thiocyanate

A precise, reliable, sensitive, and selective method for the determination of titanium(IV) is described. Titanium(IV) reacts withN ¹-hydroxy-N ¹,N ²-diphenylbenzamidine (HDPBA) and thiocyanate to form an orange-coloured mixed-ligand complex of stoichiometry 112 (Ti SCN^– HDPBA). The complex is quantitatively extractable into toluene from 0.05–0.15M hydrochloric acid. The spectrum of the complex exhibits an absorption maximum at 400 nm with a molar absorptivity of 20000M ^–1 cm^–1 and the coloured system obeys Beer's law in the concentration range 0.20–3.0 gml^–1 titanium. The effects of foreign ions and of various experimental parameters have been studied to establish the optimum conditions for the extraction and determination of titanium. The precision of the method has been evaluated and the relative standard deviation has been found to be 0.53%. The method has been successfully applied to the determination of titanium in synthetic matrices corresponding to titanium-containing ores, minerals, and alloys.     

Synthesis,characterization and monitoring of trans-[Ru{P(OMe)3}4Cl2] by reversed-phase high-performance liquid chromatography and 31P-n.m.r.

P(OMe₃)₃ reacts with RuCl₃ · 3H₂O to produce the complex trans-[Ru{P(OMe)₃}₄Cl₂] from which the complexes trans-[Ru{P(OMe)₃}₄S₂]²⁺ and cis-[Ru{P(OMe)₃}₂S₄]²⁺ (S = Solvent) can be prepared by solvation in neutral and acidic solution, respectively. The aquation takes place with a specific rate of 1.0 × 10^–2 min^–1 (pH = 3.0) and 5.4 × 10^–3 min^–1 (pH 7.0) The trans-[Ru{P(OMe)₃}₄Cl₂] complex has been characterized by elemental analysis; electronic spectra [_max = 408 nm] ( = 1.7 × 10² M^–1 cm^–1), _max = 250 nm ( = 3.5 × 10³ M^–1 cm^–1) and a shoulder at = 280 nm ( 8.3 × 10² M^–1 cm^–1)]; cyclic voltametry ( = 0.75 V versus s.c.e.); HPLC (t _R = 5.7 min); and ³¹P-n.m.r. ( = 131 p.p.m.). In acidic solutions the ³¹P-n.m.r. variations point to a reaction intermediate, characterized as the complex ion trans-[Ru{P(OMe)₃}₄S₂]²⁺ ( = 136 p.p.m.) followed by the formation of the proposed product, cis-[Ru{P(OMe)₃}₂S₄]²⁺ ( = 145 p.p.m.). For this same complex, at pH = 7.0, the results show the formation of the trans-[Ru{P(OMe)₃}₄S₂]²⁺ ( = 136 p.p.m.). The HPLC results for the trans-[Ru{P(OMe)₃}₄Cl₂] complex show that the different species are present at different pH values. In acidic media a less polar species (t _R = 4.3 min) compared with the starting material (t _R = 5.7 min) was formed. At neutral pH (t _R = 4.6 min) the species generated were not modified, however they exhibited different properties from the species obtained at a lower pH.     

Complexometric determination of copper(II) in ores,alloys and complexes using 2-mercaptoethanol as indirect masking reagent

A complexo-titrimetric method for the determination of copper(II) in the presence of other metal ions is described, based on the selective masking ability of 2-mercaptoethanol towards copper(II). Copper and other ions in a given sample solution are initially complexed with an excess of EDTA and the surplus EDTA is titrated with zinc sulfate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. A known excess of 2-mercaptoethanol solution (10%) is then added, the mixture is shaken well and the released EDTA from the Cu-EDTA complex is titrated against standard zinc sulfate solution. The interferences of various ions are studied and the method is applied to the determination of copper in its ores, alloys and complexes. Reproducible and accurate results are obtained for 2.5–40 mg of Cu with relative errors 0.4% and standard deviations 0.04 mg.     

Tris(2-ethylhexyl)phosphate as an extractant for quadrivalent tin,with subsequent determination with pyrocatechol violet in alloy samples

The solvent extraction of tin(IV) from chloride media withtris(2-ethylhexyl)phosphate is presented. Tin(IV) is extracted quantitatively from 2.75–3.20 mol dm^–3 hydrochloric acid using 6.38–6.91 mol dm^–3 tris(2-ethyl-hexyl)phosphate dissolved in toluene as an extractant. After back-extraction of tin(IV) with water from thetris(2-ethylhexyl)phosphate phase, it is estimated spectrophotometrically following complexation with pyrocatechol violet. The recommended range for determination of tin(IV) is 10–100 g. The probable extracted species is SnCl₄·2TEHP. The method is applicable to the analysis of alloy samples with a detection limit of 0.4 g/ml (for 10 g of tin) and a relative standard deviation between 0.21–0.32%.     

Spectrophotometric determination of palladium with 4-(2-pyridylazo)resorcinol

Summary A simple photometric method for the determination of palladium has been worked out, employing pyridylazo-resorcinol (PAR) as a complexing ligand for the metal ion. The coloured species is extractable into chloroform in the presence of diethylamine, the absorbance of which is measured at 535 nm. The method is free from the interference of a large number of elements particularly the other platinum metals. It obeys Beer's law in the range of 0–3 g Pd/ml with Sandell's sensitivity of 0.0034 g Pd cm^–2. The ratio of metal to ligand in the complex is found to be 1:1. Analysis of various samples has been carried out with satisfactory and reproducible results (standard deviation ±0.002).     

Synthesis and properties of disulfonated (2-benzimidazolyl)(phenyl)methanone 5-nitro-2-pyridylhydrazone (S2BINPH) and spectrophotometric determination of trace amounts of nickel with S2BINPH

Disulfonated (2-benzimidazolyl)(phenyl)methanone 5-nitro-2-pyridylhydrazone (S₂BINPH) has been synthesized and its reactivity with metal ions investigated. A sensitive and selective spectrophotometric method for the determination of nickel with this reagent has been developed. S₂BINPH reacts with nickel(II) to form a stable 12 (metal ligand) complex with an absorption maximum at 501 nm. The complex formation is quantitative in the pH range 7.2–8.5. Beer's law is obeyed over the range 60–700 ng ml^–1 of nickel and the apparent molar absorptivity of the complex is 8.86 × 10⁴ mol^–1 1 cm^–1 at 501 nm. The proposed method was applied to the determination of nickel in a standard iron- and -steel sample with satisfactory results. Furthermore, proton dissociation constants of S₂BINPH and the overall formation constant of its nickel complex were also determined spectrophotometrically.     

Stability studies of vitamins in three food reference materials

Summary Stability in storage and shipment of retinol, -tocopherol, vitamins B₁, B₂ and C in three foods was studied to assess the feasibility of certifying the vitamin content of three food RMs, whole milk powder (CRM 380), pork muscle (CRM 384) and freeze-dried haricot beans (CRM 383); these were recently certified for major dietary components and major elements. Interpretation of the long-term stability data was complicated by a dominant analytical variability over the measurement period. The long-term stability study (24 months) gave evidence of deterioration of vitamin B₂ in pork muscle. The other vitamins studied seemed to be acceptably stable at –18°C and +4°C. Additional studies showed stability of retinol in milk powder for 34 months and of vitamin C in haricot beans for 31 months at –18°C and +4°C. Long-term storage seems to be possible at a temperature not higher than +4°C except for vitamin B₂. A short-term stability study at +25°C and +30°C for 6 weeks showed acceptable stability of retinol and -tocopherol in milk powder (CRM 380) and of vitamin C in haricot beans (CRM 383). However, storage at +42°C induces degradation of retinol, -tocopherol and vitamin C.     

Crystal and Molecular Structure of Platinum(II) trans-Bis-(1,1,1-trifluoro-4-iminopentan-2-onate)

This paper describes a new method for the synthesis of the -iminoketonate complex Pt(ktf)₂ using 1,1,1-trifluoro-4-iminopentan-2-one as a bidentate ligand. An X-ray study has been performed on the polycrystals and single crystals of the compound. The single crystal X-ray diffraction analysis was carried out on a CAD-4 diffractometer (MoK radiation, /2 scan mode). Crystal data: a = 10.217(2), b = 10.231(2), c = 10.924(2) , = 83.12(3), = 63.38(3), = 70.77(3)°, V = 963.4(3) ³, space group P1, Z = 2, d _calc = 1.721 g/cm³. The Pt atom has a distorted planar square environment; the average lengths of Pt–N and Pt–O coordination bonds coincide (1.97 ). The mean value of the chelate angle is 94.2°. The environment of Pt is completed to bipyramid by the hydrogen atoms of the neighboring molecules. The structure of the compound is molecular. The differently oriented molecules of the complex are linked into chains down the x axis with Pt...Pt distances of 5.10 . A comparative crystal-chemical analysis of the structures of Pt(ktf)₂ and Pd(ktf)₂ and their O,O-chelate analogs — Pt(II) and Pd(II) trifluoroacetylacetonates — has been carried out. An X-ray study of Pt(tfa)₂ and Pd(tfa)₂ has been accomplished, and crystal data are given.     

Individual and simultaneous determination of ephedrine and phenylephrine by use of kinetic methodology

Kinetic methodology was for the first time used to develop a simple photometric method for the determination for ephedrine and phenylephrine using the stopped-flow mixing technique. The method involves oxidation of these compounds and kinetic monitoring of the reactions of the aldehydes formed with 2-methylbenzothiazoline-2-one hydrazone in the presence of iron (III) chloride to give the corresponding coloured formazans. Ephedrine and phenylephrine can be determined simultaneously by applying the proportional-equation method to the reaction rate and absorbance amplitude of the kinetic curves obtained for each analyte. The calibration graph was linear over the range 0.7–70.0 g mL^–1 ephedrine and 1.2–70.0 g mL^–1 phenylephrine. The proposed method was applied to the determination of ephedrine in pharmaceutical samples with a mean recovery of 103.2%. Synthetic mixtures of ephedrine and phenylephrine in ratios between 3:1 and 1:5 were satisfactorily resolved.