Spectrophotometric determination of pentaerythritol tetranitrate (PETN) in waste water from lead styphnate primer plants

An accurate spectrophotometric method is proposed for the determination of pentaerythritol tetranitrate (PETN) in waste water from lead styphnate primer plants by use of phenoldisulphonic acid. The waste water is filtered through a sintered glass crucible and the PETN is determined in the filtrate and the residue. In the determination of PETN in the filtrate, sodium hydroxide is added and the PETN is extracted with methylene chloride (in alkaline solution, styphnate and TNT are not extracted). The methylene chloride solution is then evaporated to dryness, the residue is treated with a solution of phenoldisulphonic acid in sulphuric acid, water and ammonia are added, and the yellow colour is measured. In the determination of PETN in the residue, the PETN is dissolved in acetone, an aliquot of the acetone solution is treated with water and sodium hydroxide, the PETN is extracted with methylene chloride and the colour is developed as above. Various factors affecting the determination were investigated. The solubility of PETN in water was studied.     

Spectrophotometric determination of tetrazene in primers and primer mixes by use of resorcinol

A spectrophotometric method is proposed for the determination of tetrazene (tetracene) in primers and primer mixes that involves treatment of the tetrazene with resorcinol solution and measurement of the intensity of the yellow colour of the diazo-dye produced. In the application of the method, lead styphnate and barium nitrate are first removed by extraction with ammonium acetate solution and then nitrocellulose and PETN are removed by extraction with acetone. The insoluble matter containing the tetrazene is boiled with resorcinol reagent, the solution filtered, and the absorbance measured at 400 nm. Conditions for optimum colour development are studied and the nature of the reaction is considered.     

Selective photometric determination of selenium in aqueous media

A procedure is developed for the photometric determination of selenium in aqueous media using 2-(p-nitrophenyl)-3,5-diphenyltetrazolium chloride. To selectively determine selenium, a two-stage scheme of sample preparation is chosen. It includes the gas extraction of selenium liberated as hydrogen selenide, its extraction from the gas phase to a solution of lead nitrate by liquid absorption and repeated extraction of hydrogen selenide, followed by its absorption with an aqueous reagent solution to form water-insoluble formazan. The formazan is extracted with chloroform. The concentration of selenium is determined from the absorbance of the chloroform extract of formazan. The procedure involves no special preconcentration operations and allows from 10 to 100 μg/L selenium to be determined.     

Extraction with long-chain amines--VI. Separation of manganese as Mn(CNS)4-(6) complex and its complexometric determination in calcareous material

Manganese is quantitatively extracted into a benzene solution of trioctylmethyl-ammonium chloride from a solution at least 0.25M in potassium thiocyanate and at pH 2.5-7. After stripping into dilute ammonia containing triethanolamine (TEA) and hydroxylamine hydrochloride, manganese is determined by EDTA titration. Calcium and magnesium are not extracted even in traces. Iron is co-extracted with manganese and is masked with TEA during the stripping. Aluminium also does not interfere. In the aqueous phase, after the extraction of manganese, calcium or magnesium can be determined by the usual EDTA titration. The method described permits highly selective individual determination of manganese and calcium and/or magnesium in all materials rich in manganese.     

Photometric determination of trace selenium in aqueous media

A new procedure is developed for the photometric determination of trace selenium in aqueous solutions. The selection of 2-(p-nitrophenyl)-3,5-diphenyltetrazolium chloride as a reagent for selenium is justified. The proposed sample preparation procedure involves gas extraction of selenium as hydrogen selenide followed by its liquid-adsorption extraction from the gas phase to an aqueous reagent solution with the formation of a water-insoluble formazan. Formazan formed upon the absorption of hydrogen selenide is extracted with isoamyl alcohol. The concentration of selenium is determined from the absorbance of the formazan extract in the isoamyl alcohol. The procedure allows the determination of 10–120 μg/L selenium.     

Studies on extraction of Cu(II), Ga(III), In(III) and Tl(III) with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one Separation and spectrophotometric determination of copper and gallium

The extraction of Cu(II), Ga(III), In(III) and Tl(III) with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPMBzP) from aqueous solutions has been investigated. The mechanism of extraction and the composition of the species extracted has been determined. The effect of equilibration time, various organic solvents and salting-out agents on the extraction of copper and gallium has also been investigated. The green Cu(PMBzP)₂ chelate has absorption maxima at 298 and 670 nm, and PMBzP has maximum absorbance at 290 nm. A new and sensitive spectrophotometric method for copper has been devised, based on the absorbance at 670 nm. The presence of excess of reagent does not interfere and no special treatment is necessary to destroy it. The proposed method has some advantages and has been applied for the determination of copper in various soil samples. Gallium has been separated from indium, thallium, copper, iron and many other elements. The recovery of gallium and copper was 100 ± 0.2%.     

2-[2-(5-Bromopyridyl)azo]-5-dimethylaminophenol; a new sensitive reagent for cadmium

Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beer's law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·10⁵ 1 mol^?1 cm^?1 at 555 nm.     

Solvent extraction of antimony(III) with 18-crown-6 from iodide media

Antimony can be quantitatively extracted from 1M sulphuric acid containing 0.25M potassium iodide with 0.02M 18-crown-6 in methylene chloride, and determined spectrophotometrically at 430 nm. Bismuth, tin, antimony and arsenic can be separated by sequential extraction with 18-crown-6 from aqueous phases with appropriately adjusted sulphuric acid and potassium iodide concentrations.     

Stability-indicating method for the determination of clorazepate dipotassium-II. Via N-desmethyldiazepam and determination of its degradation products

A spectrophotometric method for the determination of the intact clorazepate dipotassium in the presence of its degradation products is developed. It depends upon preliminary hydrolysis of clorazepate dipotassium-thus liberating its equivalent of N-desmethyldiazepam which is extracted, with benzene-methylene chloride (9:1). The extract is evaporated, the residue dissolved in methanol and its absorbance measured at about 315 nm. The procedure determines 0.4-1.6 mg of clorazepate dipotassium with an accuracy of 100.2+/-0.7%. The procedure is applied successfully for the determination of clorazepate dipotassium in bulk powder and in capsules; retaining its accuracy in the presence of up to 80% degradation. Determination of the different degradation products is also possible. Thus, N-desmethyl diazepam is determined after preliminary extraction with benzene-methylene chloride mixture, followed by TLC separation, 2-amino-5-chlorobenzophenone by directly applying the first derivative spectrophotometric technique, and glycine in the aqueous layer determined colorimetrically with ninhydrin reagent in the presence of pyridine.     

Extraction with long-chain amines-II Extraction and colorimetric determination of chromate

Highly selective extraction of chromate from slightly acidic solutions (0.1-0.2M sulphuric acid) with a chloroform solution of trioctylamine (Alamine 336-S) or trioctylmethylammonium chloride Aliquat 336-S) is described. Many metals such as iron, nickel, cobalt, copper, alluminium, zinc, are not extracted, even if present in large concentrations. Coextraction of vanadium(V) and uranium(VI) is prevented by addition of sodium chloride. Traces of extracted molybdenum are scrubbed with ammonium oxalate. Final determination of chromium is based on measurement of the absorbance of the extract at 445-450 nm.     

Argentimetric assay of captopril in bulk drug and in tablets

Three simple, selective and cost-effective procedures for the determination of captopril in bulk drug and in tablets are described. All the procedures make use of silver nitrate as a reagent and involve titrimetry and spectrophotometry as measurement techniques. In titrimetry (Method A), the aqueous solution of the drug is titrated directly with the standard silver nitrate solution to a potassium chromate end-point. In one spectrophotometric method (Method B), the sample solution is treated with excess of silver nitrate and a known amount of methyl orange and the increase in absorbance at 520 nm, caused by a decrease in pH due to release of nitric acid, is measured and related to drug concentration. The other spectrophotometric method (Method C) involves the addition of a measured excess of silver nitrate to the sample solution followed by the determination of residual silver ion by an ion-associate complex formation reaction involving eosin and 1,10-phenanthroline. The decrease in absorbance at 550 nm, which corresponds to Ag⁺ reacted with the drug, is measured and is found to be linearly related to drug concentration. All experimental variables involved in the methods were investigated and optimized. Stoichiometry of the reaction that forms the basis for titrimetry is found. Method A is applicable in the range of 1.0–20.0 mg of drug while methods B and C can be conveniently used in the concentration ranges of 2.5–50.0 and 0.25–4.0 μg ml^?1, respectively. Several optical characteristics such as molar absorptivity, Sandell sensitivity, limits of detection and quantification, and correlation coefficient were calculated. The methods were applied to the analysis of tablets containing captopril. Statistical treatment of the results indicates that the procedures are precise and accurate. The excipients used as additives in tablets did not interfere in the proposed procedures as revealed by the recovery studies.     

Atomic-absorption spectrophotometric determination of traces of manganese with thenoyltrifluoroacetone

An atomic-absorption spectrophotometric method for the determination of traces of manganese in solution with thenoyltrifluoroacetone (TTA) is described. Manganese(II) is extracted with 0.01M TTA in methyl isobutyl ketone (MIBK) at pH 9.5. The atomic-absorption of the organic phase at 279.5 nm is measured. Except for chromium, iron, hafnium, niobium, nickel, rhodium, tin, titanium and zirconium, microquantities of many other cations and anions do not interfere. Iron can be removed by MIBK extraction before the TTA extraction. The sensitivity of the method was 1.6 ng/ml for 1% absorption in aqueous solution. The method was successfully applied to the analysis of environmental waters. Manganese in the filtered fractions of water samples was reliably determined with relative standard deviations of 7% at the 5 mug/l. level and 1% at 50 mug/l.     

The polarography of lead styphnate

A study of the polarographic behaviour of lead styphnate has been made. It has been shown that by use of a combination of normal polarography and derivative polarography using an alternating current method it is possible to determine both lead and styphnate ions in the samesolution.     

Spectrophotometric determination of copper, nickel, cobalt, iron and manganese as their pyridine thiocyanates Simultaneous determination in mixtures

Spectrophotometric determinations of copper, nickel, cobalt, iron, and manganese, based on the chloroform extraction of the metal pyridine thiocyanates, have been investigated. Optimum conditions require the pH of the aqueous solution to be in the range about 5–8; tartaric acid is used to prevent precipitation of hydrous oxides. An excess of pyridine must be used because chloroform readily extracts pyridine from the aqueous solution. Results are improved by making the extraction from a solution of high ionic strength (2 or above), which is provided by magnesium nitrate. Perchlorate decreases the absorbance, but the effect is essentially constant over a perchlorate concentration range of 0.8 to 2M. Although the metal pyridine thiocyanates are extracted by benzene, substituted benzenes, and halogenated hydrocarbons, chloroform is superior to other solvents in extraction efficiency and in colour stability of the extracted species. An example is given of the simultaneous determination of copper, nickel, cobalt, and iron in the same solution. Anions that also form metal pyridine compounds must be absent.     

Infrared macro and semimicro determination of nitrogen in raw nitrocellulose and nitrocellulose contained in propellants

The infrared procedure for the determination of nitrogen in raw nitrocellulose has been improved. In the original method 0.31-0.32 g of sample was dissolved in 45 ml of tetrahydrofuran, the solution was weighed, and the infrared peak at 6.0 microm was measured. The calibration curve was prepared by plotting absorbance against mg of nitrogen per g of solution. The method has the disadvantage that the height of the peak is affected by the sample weight. In the improved method the error due to the sample weight is eliminated by using 0.3000 g of sample and diluting to 50 ml in a volumetric flask. The calibration curve is prepared by plotting absorbance against % nitrogen. The method was extended to the semimicro scale by using a 30.0-mg sample and diluting to 5 ml in a volumetric flask. The method has been applied on the macro and semimicro scales to the direct determination of nitrogen in nitrocellulose after a methylene chloride extraction. The amounts of graphite and inorganic salts found in nitrocellulose-base propellants do not interfere, but a correction must be made to refer the results to 0.3000 g of nitrocellulose for the macro method or 30.0 mg of nitrocellulose for the semimicro method. The same calibration curve is used for all procedures.     

Colorimetric determination of palladium with pyridine-2-aldehyde-2'-pyridylhydrazone

The colorimetric determination of palladium described involves the extraction of chloro(PAP)palladium(II) from an acidic aqueous solution into o-dichlorobenzene and measurement of the absorbance of the extract solution. The method is suitable for the determination of 10–100 μg of palladium. Tolerance amounts for many metals have been determined and compare very favourably with those of other methods.     

Extractive separation and spectrophotometric determination of tungsten as ferrocyanide

Tungsten, in amounts ranging from micrograms to milligrams, can be extracted into isoamyl alcohol, as the tungsten(V) ferrocyanide complex obtained by reduction of tungsten(VI) with tin(II) in 4M hydrochloric acid containing ferrocyanide. It can thus be separated from iron, cobalt, chromium, manganese, arsenic, antimony, bismuth, silicon, calcium and copper, their precipitation being prevented by addition of glycerol and, in the case of iron, sulphosalicyclic acid. Molybdenum, vanadium and nickel are not separated from tungsten, however. Tungsten can also be determined spectrophotometrically as tungsten(V) ferrocyanide. The absorbance of the brown complex is measured in aqueous solution or preferably after extraction into isoamyl alcohol. As many alloying elements interfere, they should be separated by the ferrocyanide extraction or other suitable method. Both the separation and the determination methods give satisfactory results with an overall error of not more than 0.5% in the analysis of practical samples containing low or high percentages of tungsten.     

Determination of ethylene dimethacrylate in nitrocellulose-base propellants

Ethylene dimethacrylate was determined in nitrocellulose-base propellants by saponification, bromination, and infrared. In the saponification method the ethylene dimethacrylate was saponified after extraction with methylene chloride; for greatest accuracy a slight correction was made for the nitration products of diphenylamine which react with alkali. In the bromination method the ethylene dimethacrylate was determined by titration with potassium bromate after extraction with methylene chloride; a correction was made for diphenylamine which is also brominated. The diphenylamine in propellants containing ethylene dimethacrylate was determined by bromination after a steam distillation, using either the gravimetric or titrimetric technique. In the infrared method the ethylene dimethacrylate was extracted with methylene chloride and the ester peak at 5.79 μ was measured in the methylene chloride solution. The saponification, bromination, and infrared methods checked each other reasonably well. This attests to the validity of the methods and also indicates that polymerization of ethylene dimethacrylate does not occur in the manufacture of the propellant.     

Photometric determination of quaternary ammonium compounds with hexanitrodiphenylamine. I.

Dissociation contants, partition coefficients and absorption spectra have been determined for hexanitrodiphenylamine and pentanitrodiphenylamine. The two compounds have quite different dissociation constants and can be easily separated. Both substances give compounds with quater- nary ammonium ions which can be extracted with chloroform or methylene chloride from an aqueous solution. to obtain a pure hexanitrodiphenylamine compound the reagent must be free from pentadinitrodiphenylamine and the extraction made at high pH.     

Spectrophotometric methods for the determination of osmium-III Reaction of osmium tetroxide with 1:5-diphenylcarbo- hydrazide in aqueous solutions followed by extraction of the complex

-A spectrophotometric method has been developed which is applicable to the determination of extremely small quantities of osmium. Osmium is oxidised to the octovalent state, then added to an acidic aqueous solution containing 1:5-diphenylcarbohydrazide (DPC). After heating the aqueous solution to 65°, the osmium-DPC complex is extracted with chloroform. A molar absorbancy index of about 150,000 is obtained. From 7 to 25 μg of osmium can be determined with a coefficient of variation of 6%. It was established that Fe^III, Cu^II, Ru^III and Au^III seriously interfere in the determination of osmium by this method, while Cr^VI, Ni^II, Mo^VI, Ir^III and chloride interfere only when present in relatively high concentrations.