Spectrophotometric Determination of Quintomycin Sulphate with Phloroglucinol

Abstract

A new absorptiometric procedure for the determination of quintomycin sulphate in complex galenical mixtures is proposed, based on the reaction of the sample compound with a mineral acid-containing phloroglucinol solution. Absorbance readings at 448 nm obey Lambert-Beer's law within the concentration range from 4. 0 to 32. 0 μg ml^?1. The method is operationally simple and has a good precision and an adequate selectivity.     

Titrimetric and spectrophotometric assay of pantoprazole in pharmaceuticals using cerium(IV) sulphate as oxidimetric agent

Titrimetric and spectrophotometric assay of pantoprazole sodium sesquihydrate (PSS) using cerium(IV) sulphate as the oxidimetric reagent is described. The methods are based on the oxidation of PSS with a measured excess of Ce(IV) sulphate followed by the determination of unreacted oxidant using different reaction schemes. In titrimetry, the unreacted oxidant was determined by back titration with ferrous ammonium sulphate (FAS) in sulphuric acid medium. Spectrophotometry involves the reduction of unreacted Ce(IV) sulphate with a fixed quantity of Fe(II). The resulting Fe(III) is complexed with thiocyanate and the absorbance is measured at 470 nm. In both the methods, the amount of Ce(lV) sulphate reacted corresponds to PSS concentration. Titrimetry is applicable over 1–10 mg range whereas in spectrophotometry, the calibration graph is linear in the range of 0.5–7.0 μg/mL and the calculated molar absorptivity value is 1.58 × 10⁵ L/mol cm. The validity of the proposed methods was tested by analyzing pure and dosage forms containing PSS. Statistical treatment of the results reflects that the proposed procedures are precise, accurate and easily applicable to the determination of PSS in pure form and in pharmaceutical formulations.     

Spectrophotometric Determination of Etilefrine,Ritodrine, Isoxsuprine and Salbutamol by Nitration and Subsequent Meisenheimer Complex Formation

Abstract

A simple and sensitive colorimetric method has been developed for the determination of four phenolic drugs, namely, etilefrine hydrochloride, ritodrine hydrochloride, isoxsuprine hydrochloride and salbutamol sulphate. The method is, mainly, based on the nitration of the drug molecule followed by the subsequent formation of meisenheimer complex with a nucleophilic reagent (acetone) in alkaline medium. The experimental conditions leading to optimum chromogen intensity and stability were carefully studied and incorporated in the general procedure. Under the proposed conditions, the method was applicable over the concentration range of 4.8–16 μg ml^?1 for the four drugs. The suggested method was further applied for the determination of the studied drugs in bulk and pharmaceutical dosage forms. The results of the analysis were found to agree statistically with those obtained with either the official or the referee methods. The procedure is characterized by its simplicity with accuracy and precision.     

Determination of Sulphate by Titrimetric and Colorimetric Measurement of Equivalent Displaced Zinc Ion

Abstract

Two methods are described for the determination of sulphate in the range of 200 μg to 100 mg by dissolving precipitated barium sulphate in excess of EDTA at pH 12.5. A titrimetric procedure involves back titration of excess EDTA with a standard zinc solution, while a complementary spectrophotometric method makes use of the stability of the barium EDTA complex in the presence of an excess of zinc ions; the latter are reacted with zincon and are equivalent to the amount of sulphate present.     

A Model to Establish the Limit of Decision and the Limit of Detection for Straight-Line Curves in a Case of Heteroscedasticity

Abstract

A problem arises when determining the decision and detection limits in a series of results where the variance of the error distribution of the analytical signals around their expectation is not a constant when applying a method proposed by Hubaux and Vos⁶. In this paper an approach is proposed to overcome this difficulty, that involves the use of a transform method to convert heteroscedastic data to homoscedastic data so that the limit of detection can be obtained by projection of the confidence band about the linear regression. This approach is applied to the case of a gravimetric determination of sulphate ion in the 1 – 5 mgL^?1 SO₄ ^2- range. The results obtained from this approach are compared from others obtained previously.     

Simultaneous Determination of Selenocyanate and Thiocyanate Ions in the Presence of Cyanide by Oxidation with bis (Trifluoroacetoxy) iodobenzene

Abstract

An investigation of the use of potentiometric titrations of selenocyanate and thiocyanate aqueous solutions, in the presence of cyanide ions, with bis (trifluoroacetoxy) iodobenzene in acetonitrile and then the gravimetric determination of the products of the reactions, elemental selenium and sulphate ions, has been carried out.

Selenocyanates are first oxidized to selenium and then thiocyanates are oxidized to sulphate ions. Break point curves are identified. The rose-pink precipitate is filtered and the clear filtrate is warmed on a hot plate for evaporation of acetonitrile. A solution of barium chloride is added to the hot solution in order to precipitate the sulphate ions.     

Spectrophotometer Determination of Nitrite Using Salbutamol sulphate as a Reagent

Abstract

A simple spectrophotometric method for the trace determination of nitrite (NO^? ₂) is described. Nitrite is reacted with Salbutamal sulphate in acidic medium which gives a yellow colour in alkaline medium (?pH 7) and can be determined in the presence of several cations and anions. Beer's law is obeyed in the range of 1.8 to 27.6 ppm of nitrite with the molar absorptivity 1.8 × 10³ 1 × mole^?1 × cm^?1 at 4l0 nm. The proposed method can also be utilized for the determination of nitrate (NO^? ₃) after its reduction to nitrite. The method has been applied for the determination of various samples containing traces of nitrite.     

18-Crown-6-potassium Ferricyanide Complex as a Potentiometric Titrant

Abstract

An oxidimetric titrant, 18-Crown-6-potassium ferricyanide complex, has been prepared in acetonitrile. This reagent is proposed for redox titrations in aqueous - acetonitrile media of some reductant compounds. The general analytical conditions for using this complex and the procedures for potentiometric determinations of oxalate, arsenic (III), thiocyanate, nitrite, sulfite, thiosulphate and iodide ions, as well as hydrazine sulphate and hydrogen peroxide are presented.     

Determination of Residues of Furadan (Carbafuran) in Water by Spectro-Photometric Method

Abstract

A spectrophotometric method for the determination of carbafuran residues in field water using eerie sulphate as a reagent has been worked out.     

Determination of Poisonous Trace Element Thallium(I) by Kinetic Catalytic Reaction

Abstract

A effective and simple determination of poisonous trace element thallium(I) by means of kinetic catalytic reaction is proposed. The method is based on a catalytic effect of thallium(I) on a luminol-hydrogen peroxide system. Three different kinds of surfactants, cetrimonium bromide (CTMAB), sodium dodecyl sulphate (SDS), and Tween-80, are also investigated to improve the detection sensitivity. In optimum conditions, a highly selective and sensitive method for detecting trace thallium(I) has been established. The detection limit is 0.0073 µg · mL^?1, the relative standard deviation for six determinations of 0.04 µg · mL^?1 thallium(I) is less than 4.0%, and the linear range of determination is 0.02–0.1 µg · mL^?1.     

Determination of Sulphur in Solid and Liquid Samples by Potentiometric Titration with Ion Selective Electrode.

Abstract

This paper describes a potentiometric method for the determination of sulphur in solid and liquid samples, using a sulphide ion selective electrode after the reduction distillation step. The determination of sulphide in solid and liquid samples without prior treatment was carried out by direct and titration potentiometric methods.

The reproducibility of the method and the recovery of sulphate in solid samples was investigated using analytical reagent grade 99% sodium sulphate. Portions of aproximately 100 mg of reagent were subjected to the reduction distillation process. After the ion selective electrode showed a stable value of the potential, indicating that all the sulphate had been reduced to sulphide, the potentiometric titration with lead nitrate solution was performed. A mean recovery of 98% of sulphate was found. The potentiometric titration method described in this work, can be applied to determine S⁼ in solid samples with the advantage that it does not require sample solubilization or extraction prior to the determination. The method yields an almost total reduction of sulphur and also a good precision.     

Non-aqueous and two-phase titrimetric assay of isoxsuprine hydrochloride in pharmaceuticals

Based on the nitrogenous base or quaternary ammonium moiety in isoxsuprine hydrochloride (ISX), two highly accurate and selective titrimetric methods are proposed f or the determination of ISX in spiked human urine, injection and tablets. Non-aqueous titration (Method A) involves removal of protonated amine using mercuric acetate for enhanced basic nitrogen prior to titration with perchloric acid in an acetic acid medium using crystal violet as indicator. Two-phase titration (Method B) is based on ion association complex formation between sodium lauryl sulphate (SLS) and protonated amine of ISX at pH 2.5 in aqueous phase, end point being detected by change in dimethyl yellow color in chloroform layer. The methods are applicable over the concentration range 2.0–20.0 mg and 1.0–10.0 mg for method A and method B, respectively. Calculations are based on 1: 1 molar ratio, i.e., JSX: HClO₄ for method A and ISX: SLS for method B, owing to the presence of one nitrogen atom. Method A is applicable to the determination of ISX in tablets whereas method B is applicable to spiked human urine, injection and tablets. The methods are validated statistically by comparing the results with those of the reference method by applying the Student’s t-test and F-test. The accuracy was further ascertained by recovery studies via standard addition technique.     

Solid Extraction of Steroid Conjugates from Plasma and Milk

Abstract

Extraction of steroids and steroid conjugates with Amberlite XAD-2 and Sep-Pak C₁₈ has been studied. Amberlite XAD-2 has ionic sites with high affinity for conjugated steroids, particularly steroid disulphates. Nearly quantitative recoveries of steroid conjugates are obtained when the resin is washed with an aqueous solution of a sulphate prior to elution with methanol. Such treatment is not required using Sep-Pak C₁₈ cartridges.

The adsorbents were used for extraction of steroids and their conjugates from plasma and milk. Steroid-protein and steroid-lipid interactions were minimized by diluting the fluid twice with 0.5 M aqueous triethylamine sulphate and passing the solution through the adsorbent a t 64°C. Steroids were eluted with methanol and methanol/chloroform at room temperature. Essentially quantitative recoveries were obtained with both adsorbents.     

Determination of Total Sulphur in Vegetation by a Turbidimetric Method Following An Oxygen-Flask Combustion

Abstract

A rapid method of determining total sulphur in vegetation is described. The plant material is combusted in an oxygen-flask, and the sulphate content of an aliquot of the absorbing solution is determined turbidimetrically as barium sulphate. The method is convenient and accurate. Its results agree closely with those obtained by the AOAC magnesium nitrate procedure.     

The Use of μ-Oxo-ditrifluoroacetato-diphenyl-diiodine in Potentiometric Titrations

Abstract

The use of μ-oxo-ditrifluoroacetato-diphenyl-diiodine (μ-ODDD) in potentiometric titrations has been studied. This reagent is more powerful oxidizing agent and more stable than bis(trifluoroacetoxy) iodobenzene (BTIB). The general analytical conditions for using this oxidant and the procedures for potentiometric determinations of sulfite, thiosulphate, nitrite, selenocyanate, thiocyanate and iron(II)ions as well as hydrogen peroxide and hydrazine sulphate are described.

A simultaneous determination of hydrazine sulphate and nitrite ions and also of selôenocyanate and thiocyanate ions has been carried out.     

Studies in bivalent chromium salts

Summary It has been shown in these investigations that the titrations of methylene blue, indigo, crystal violet, eosin, malachite green, magenta and orange G can be carried out successfully with chromous sulphate solution. Comparative results with titanous chloride and chromous sulphate indicate a fair degree of agreement. However, the reduction is found to be more facile with chromous sulphate.Part I: See Z. analyt. Chem. 158, 20 (1957).The authors' thanks are due to Dr. R. N. Singh, Professor of Chemistry, B. R. College, Agra, for providing laboratory facility and encouragement.     

Cerate-chromate oxidimetry

Summary Oxalic acid is oxidised to carbon dioxide and water with sulphatocerate in dilute sulphuric acid medium. Formic acid is not affected by ceric sulphate under the above conditions. Both oxalic and formic acids are quantitatively oxidised to carbon dioxide and water by the cerate-chromate reagent. Based on this principle a method has been suggested for the estimation of a mixture of oxalic and formic acids.Part I: see Z. analyt. Chem. 154, 340 (1957).     

Determination of Cefmenoxime in Human Serum by Ion-Pair Reverse-Phase High Performance Liquid Chromatography

Abstract

A highly reproducible ion-pair reverse-phase high performance liquid chromatographic assay for cefmenoxime in human serum has been developed. A simple sample cleanup procedure is employed. Cefoxitin is the internal standard and separation is achieved using a C-18 μ-Bondapak column. The mobile phase consists of 20% acetonitrile and 80% 0.05 M ammonium acetate buffer containing 0.005 M tetrabutylammonium hydrogen sulphate as the ion-pair agent. Samples are quantitated by UV detector at 254 nm and 0.02 aufs with an assay sensitivity of 0.625 μg/ml. The method has been successfully applied in a clinical setting.     

Conductometric Determination of N-acetylcysteine in Pharmaceutical Formulations Using Copper(II) Sulphate as Titrant

Abstract

A simple, precise, rapid, and low-cost conductometric method for N-acetylcysteine determination in pharmaceutical formulations is proposed. N-acetylcysteine present in pharmaceuticals containing known quantities of the drug was conductometrically titrated in aqueous solution with copper(II) sulphate using a conductometric cell coupled to an autotitrator. No interferences were observed in the presence of common components of the tablets such as sodium monophosphate, saccharine, sodium benzoate, sucrose, and fructose. Recoveries of N-acetylcysteine from various tablet dosage formulations ranging from 98.3 to 102.0% were obtained.     

Effects of Counter Ions in Ion-Pair Liquid Chromatography of Hydrophobic Amines on Non-Polar Bonded Phases

Abstract

The retention behaviour of alprenolol and related hydrophobic amines in ion-pair adsorption systems has been examined with particular emphasis on the influence of different mono-and divalent counter ions (dihydrogenphosphate, bromide, perchlorate, dimethylcyclohexyl sulphate, sulphate and ethylenediaminetetraacetate). N,N-dimethyloctylamine (DMOA) and 1-pentanol were used as modifiers in the aqueous eluent and LiChrosorb RP-8 as stationary phase.

The retention is evaluated according to a two-site adsorption model and equilibrium constants are given for ion pair adsorption of DMOA. The retention of alprenolol has been evaluated in terms of ion exchange with DMOA and the ion-exchange constants are shown to be of the same magnitude and independent of the nature of the counter ion used. The ion-pair adsorption and the ion-exchange approaches are analogous expressions for the distribution process governing the retention.