Determination of Formaldehyde in Waste Water by Lucigenin Chemilummescence

Abstract

A chemiluminescence analysis has been developed for the determination of formaldehyde based on its inhibition of the chemiluminescence reaction of lucigenin-C10^?-H₂o₂. The method is sensitive, convenient and selective with a detection limit of 0.05ng/ml. The linear dynamic range is 1.0ng/ml to 0.1 μg/ml. The variation coefficient of ten determinations for 2.Ong/ml formaldehyde is 1.2%. Applications to the trace determination of formaldehyde in industrial waste waters are discussed.     

Determination of Nitrite by Single-Sweep Polarography

Abstract

A new method for determining nitrite is proposed. the mechanism for the polarographic waves and the condition for determining nitrite are discussed in this paper. In cathodic sweeps, the peak height is directly proportional to the concentration of nitrite over the range 5×10^?9?6×10^?7 g/ml, the detection limit is 4×10^?9g/ml. the experiments showed that this polarographic wave is an adsorption wave, and useful in determination of nitrite in water sample.     

A Fluorimetric Method for the Determination of Cyanide with Fluorescein and Iodine∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of cyanide with fluorescein as fluorogenic reagent (λ_ex = 494 nm, λ_em = 514 nm) at pH 6.0–7.0. A linear calibration curve was obtained in the range 0.004–2.0 μg CN^?/25 ml. The detection limit is 0.004 μg CN^-/25 ml. The method was successfully applied to the determination of cyanide in waste water.

     

Selective Kinetic Spectrophotometric Determination of Nitrite in Food and Water

Abstract

A highly selective and sensitive method for the kinetic spectrophothometric determination of sub-microgram amounts of nitrite has been development based on its reaction with Nile blue 2B in acidic medium. The reaction is monitored spectrophotometrically at 595 nm at a fixed time of 4.5 min. The change in absorbance at 595 nm is related to the concentration of nitrite in the range 0.005 - 1.100 μg.ml^?1 The detection limit is 0.001 μg.ml^?1. The relation standard deviation is 1% for 0.020 μg.ml^?1 of nitrite for ten replicate measurements. Most common anions and cations do not interfere. The procedure was applied to the determination of trace amounts of nitrite in sausage and water.     

Spectrofluorimetric Determination of Nitrite with Pyridoxal-5-Phosphate-2-Pyridylhydrazone

Abstract

The nitrite ion oxidizes pyridoxal-5-phosphate-2-pyridyl-hydrazone in acid medium giving a fluorescent product (λ_ex 325 nm, λ_em 420 nm). This redox reaction is used to developed a spectrofluorimetric method for the determination of nitrite. The calibration graph is liner in the 0.1 ? 1.0 μg mL^?1 range. The interference levels, stoichiometry and nature of the reaction have been studied. The method is applied to determine nitrite in water and soil samples     

Simultaneous Determination of Micro Bromide and Iodide by Kinetic Spectrophotometric Method

ABSTRACT

ABSTRACTA new kinetic spectrophotometric method for the simultaneous determination of concentrations of micro bromide and iodide has been proposed. It is based on their catalytic effects on the reaction of m-cresol purple oxidized by potassium periodate in hydrochloride acid medium. The reaction rate was monitored by measuring the decrease in absorbance at 528nm and the increase in absorbance at 455nm. The total difference in absorbance of the sum of bromide and iodide is identical with determination of bromide was carried out after Cr(VI) oxidized I? to I₂, and I₂ was removed by extraction with CCI₄, and the amount of iodide was measured by subtracting the absorbance change of bromide from the total absorbance change in the presence of bromine and iodide. The optimum conditions influencing the reaction rate were studied. The linear range of determination is 0～4.0μg/ml for Br? and 0～3.0 μg/ml for I?. The detection limits are 0.032μg/ml for Br? and 0.059 μ/ml for I?. The method was successfully applied to the determination of micro amounts of bromide and iodide in food and life samples.     

An Extractive Spectrophotometric Method for the Determination of Nitrite Using Fluorescein Amine Isomer I

ABSTRACT

A sensitive spectrophotometric method for the determination of nitrite using fluorescein amine isomer I is described. The method is based on the formation of azido derivative of fluorescein amine isomer I, which is selectively extracted into 20% iso amyl alcohol in toluene and is stripped to aqueous phase using NaOH. Formation of the azido derivative depends on nitrite concentration and the system obeys Beer's law in the range 0-0.4 ppm of nitrite at 495 nm. The molar absorptivity of the colour system is 6.67 × 10⁴ L mol^-1 cm^-1 with a relative standard deviation of 3% for 10 determinations at 1 μg of nitrite. The proposed method is successfully applied for the determination of nitrite and nitrate in soil, water and radiator coolant sample, NO₂ gas in a laboratory fume cupboard is determined after fixing it as nitrite in sodium arsenite absorber solution.     

Simultaneous Analysis of Pyridoxine and Melatonin in Tablet Formulation by Derivative Ultraviolet Spectroscopy

Abstract

A method for simultaneous analysis of pyridoxine and melatonin by second and third derivative UV - spectroscopy, the “zero - crossing” technique, is described. The determination has been carried out in 0.1 mol dm^?3 hydrochloric acid solution and the concentration range of 2 – 10 μg/ml pyridoxine and 0.5 – 3.5 μg/ml melatonin. Lower limits of detection at the 95% confidence level were 0.26 μg/ml for pyridoxine and 0.05μg/ml for melatonin The advantages of the proposed method include its application for the assay and in-vitro dissolution studies of pyridoxine and melatonin from two different tablet formulations.     

Determination of Naloxone Hydrochloride in Dosage form by High-Performance Liquid Chromatography

Abstract

A new, sensitive and rapid method for the determination of naloxone hydrochloride as drug in dosage entity and form using HPLC has been developed. Authentic naloxone hydrochloride was used to establish a calibration curve. A linear relationship was obtained for concentrations ranging from 10 μg/ml to 50 μg/ml. The column used was C₁₈, Micropak MCH-10 (monomeric) and the mobile phase was acetonitrile : 0.01 M KH₂PO₄ (70 : 30) at a flow rate of 2 ml/min. Retention time for naloxone hydrochloride was 3.3 minutes. The proposed method has been proved accurate and precise compared to other pharmacopoeia methods of assay for naloxone hydrochloride.     

Spectrophotometric determination of traces of nitrite with rhodamine 6 G

A simple and highly selective spectrophotometric method is described for the determination of nitrite. The method is based on the measurement of decrease in absorbance at 525 nm of rhodamine 6 G in sulphuric acid medium. The decrease in absorbance is instantaneous on addition of nitrite and remains stable for 2 h. Linear calibration graph passing through the origin was obtained in the range 0.01–0.6 g/ml nitrite. The method is free from interference of Cu²⁺, Fe³⁺ and SO ₃ ^2– which normally interfere in other procedures. The method was applied successfully to the determination of nitrite in well and sea water samples and in KNO₃, NaNO₃, table salt, sugar and milk powder samples.     

New Rapid Assay for Nafcillin by Spectrofluorimetry in Pharmaceutical Dosage

Abstract

A method for the spectrofluorimetric determination of nafcillin is proposed (λ_ex = 226 nm, λ_em = 366 nm), for concentrations between 0.10 and 1.0 μg mL^?1. The method was performed in ethanol/water medium (30% V/V), at apparent pH 6.0 provided by adding of phosphate buffer solution with pH = 6.20.

The obtained values of detection and determination limits are 0.016 and 0.054 μg mL^?1, respectively.

The method was successfully applied to assay a commercial injection containing nafcillin sodium monohydrate.     

Quantitative Analysis of Nicorandil in Commercial Tablets by Spectrophotometry

The main aim of this work is to develop and validate a spectrophotometric method for the determination of nicorandil in commercial tablets. The method is based on the reduction of the nitroxy ethyl group of nicorandil into carbonyl compound and nitrite ion by NH₄Cl and Zn dust. The nitrite ion thus formed reacts with potassium iodide and starch in dilute HCl medium to form a blue product, which absorbs maximally at 550 nm. Beer's law is obeyed in the concentration range 0.4‐4.0 μg mL^?1 with molar absorptivity of 7.92 × 10⁴L mol^?1 cm^?1. The detection limit is 0.017 μg mL^?1. The reaction conditions are optimized and validated as per the International Conference on Harmonisation guidelines (USA). The proposed method has been applied successfully for the determination of nicorandil in commercial tablets. The results of analyses are compared statistically with those of the author's spectrophotometric method, which confirmed that there is no significant difference between the methods compared.     

Spectrophotometric Determination of Tetracyclines in Pure Form and in Pharmaceutical Preparations,by a Molybdenum Blue Method

Abstract

A new and sensitive spectrophotometric method has been developed for the determination of tetracyclines either in a pure form or in Pharmaceuticals, by a molybdenum blue method. The procedure is based on the observation that, in sulphuric acid medium, tetracyclines reduce ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of antibiotic present. The variables affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 20 μg/ml of tetracycline HCl and oxytetracycline HCl, 28 μg/ml of demeclocycline HCl, 18 μg/ml of chlortetracycline HCl, 32 μg/ml of doxycycline HCl and 40 μ/ml of rolitetracycline. Molar absorptivities (1 mol^?1 cm^?1) and Sandell's sensitivities (μ cm^?2 per 0.001 absorbance unit) are, respectively: tetracycline HCl 4.9×10⁴ and 0.0098, oxytetracycline HCl 5.4×10⁴ and 0.0092, demeclocycline HCl 1.6×10⁴ and 0.0313, chlortetracycline HCl 5.5×10⁴ and 0.0094, doxycycline HCl 3.4×10⁴ and 0.0141, rolitetracycline 2.7×10⁴ and 0.0195.     

Simultaneous Determination of Tinidazole and Furazolidone in Suspension by HPTLC and HPLC

Abstract

High performance thin layer chromatographic (HPTLC) and high performance liquid chromatographic (HPLC) methods were developed for the simultaneous determination of Tinidazole and Furazolidone in suspension.

In the HPTLC method the separation of Tinidazole and Furazolidone was carried out on silica gel 60F₂₅₄ HPTLC glass plate using chloroform:methanol:ammonia (9:1:0.1 v/v) as a mobile phase. Rf values obtained were 0.63 and 0.79 for Furazolidone and Tinidazole respectively. Densitometric evaluation was done at 335 nm. Linearity was obtained within the concentration range 10–50 μg/ml and 3.5–17.5 μg/ml for Tinidazole and Furazolidone respectively.

The second method is based on high performance liquid chromatography on a reversed phase column (μ Bondapak C₁₈) using a mobile phase comprised of water: acetonitrile: triethylamine (80:20:0.1 v/v) adjusted to pH = 3.0 with dil. phosphoric acid. Retention times were 5.24 and 7.82 min for Tinidazole and Furazolidone respectively at a flow rate of 1.5 ml/min. Detection was done at 335 nm. Linearity was obtained within the concentration range 30–180 μg/ml and 10.5–63 μg/ml for Tinidazole and Furazolidone resp.     

A Fluorimetric Method for the Determination of Atmospheric Sulphur Dioxide With 2′, 7′—Dichlorofluorescein∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of atmospheric sulphur dioxide with dichlorofluorescein as fluorogenic reagent (λ_ex = 505 nm, λ_em = 520 nm) at pH 4.0–6.0. A linear calibration curve was obtained in the range 0.01–0.40 μg SO₂/25 ml. The detection limit is 0.01 μg SO₂/25 ml. Nitrogen dioxide does not interfere with the method. The method was successfully applied to the determination of atmospheric sulphur dioxide.

     

Precise and sensitive determination of nitrite by coulometric backtitration under flow conditions

A novel method performing for coulometric backtitrations in flow channels was developed, which ¶was applied for the precise and sensitive determination of low concentrations of nitrite. Under acid conditions nitrite is reacting stoichiometrically with hydrazine, the remained excess of which is backtitrated with electrogenerated bromine. The titration course is recorded either amperometrically or chemiluminometrically. Hydrazine can be determined precisely and accurately in the range between 0.1 μM and 1 mM without calibration. Nitrite is reduced by hydrazine according to the reaction 2 NO₂ ^– + 2 H⁺ + NH₂-NH₂→N₂O + N₂ + 3 H₂O. Applying the amperometric and the chemiluminometric end-point location nitrite was determined accurately and precisely in the ranges 0.25–65 μM and 0.10–50 μM, respectively. The method was applied to the determination of nitrite in tap and river water.     

Simultaneous Quantitation of Minoxidil and Tretinoin in Magistral and Pharmaceutical Preparations by First Derivative Spectrophotometry

Abstract

A first derivative spectrophotometry method has been developed for the simultaneous quantitation of minoxidil and tretinoin. The method is based on measuring the first derivative signals (D₁) of minoxidil and tretinoin at 290 and 351 nm, respectively, without any interference from each other, or any other coexisting materials. Beer's law was valid over the concentration range 2–10 μg/ml of minoxidil and 0.25–1.25 μg/ml of tretinoin. The proposed method has been applied successfully to the determination of some magistral and pharmaceutical preparations. Relative standard deviations for the assay of both drugs were less than 0.95%.     

Spectrophotometric Determination of Nitrite in Aqueous Solution by the Diazotization-Coupling Method with Orthanilic Acid-Resorcinol

Abstract

A spectrophotometric method for the determination of nitrite is described. It relies upon the reaction of this ion with an acidified orthanilic acid solution to form a diazonium ion, which is subsequently coupled with resorcinol, in alkaline medium, to form immediately a yellow-colored stable water-soluble and intense azo dye having maximum absorption at 426 nm. The linear absorbance plot with concentration indicates that Beer's law is obeyed over the range of 1-12 μg of nitrite in a final volume of 10ml, with a molar absorptivity of 38.7 × 10³1 mol^?1cm^?1, sensitivity index of 0.0012μgcm^?3, relative error of –0.5 to +0.2% and relative standard deviation of 0.43-3.5%, depending on the concentration level. The optimum conditions affecting and related to the color reaction and interference due to foreign ions have been studied.     

Determination of Molybdenum in Human Urine by Spectrophotometric Method using Thiazolylazo Compounds as Chromogenic Reagents

ABSTRACT

Four azo compounds based on diazotization of 2-aminobenzothiazole have been synthesized and characterized by elemental analysis as well as different spectroscopic techniques. The potentiality of the prepared compounds as new chromogenic reagents for the spectrophotometric determination of Mo⁶⁺ was studied by extensive investigation of optimum conditions favouring the formation of the coloured complexes. Beers law is obeyed in the concentration range 0.2-8.5 μg ml^?1 whereas Ringbom optimum concentration range was 0.8-7.5 μg ml^?1. The detection limit was 0.05 μg ml^?1. The molar absorptivity and Sandell sensitivity of the formed complexes are calculated. The effect of interfering ions on the determination of Mo⁶⁺ was investigated. The relative standard deviations for six replicate determinations of 5.0 μg ml^?1 of Mo⁶⁺ are 1.23, 1.47, 1.05 and 1.38 % using reagents I, II, III and IV, respectively. The proposed method has been applied to investigate the amount of Mo⁶⁺ in human urine samples. The molybdenum levels found between 0.5-2.1 μg/100 ml.     

Development and Optimization of Twenty-Four Hour Manual Methods for the Collection and Colorimetric Analysis of Atmospheric NO2

Abstract

Manual twenty-four hour colorimetric procedures for the determination of atmospheric NO₂ are described. The methods are based on collecting NO₂ by bubbling ambient air for twenty-four hours through reagents that form stable nitrite solutions. The reagents described have a 93 % collection efficiency over the range of 20 to 750 μg/m³ NO₂ with no apparent interferences. The inadequacies' of the former reference or alkaline method¹ are also described.