Determination of manganese(II) by a chemiluminescence reaction

Manganese(II) ( 1.5 ng/ml) is determined by measuring either of the two emission peaks given by alkaline oxidation of luminol. Several other metal ions, which enhance both emission peaks, are masked by cyanide ions.     

Determination of 2-mercaptobenzothiazole, tolyltriazole and benzotriazole in coolant formulations by liquid chromatography

An analytical method based on high-performance liquid chromatography is suitable for the determination of corrosion inhibitors in coolant solutions based on ethylene glycol. An isocratic system of methanol/aqueous sodium acetate buffer is used with a Microbondapak C18 column. Recovery is 99+%, with a sensitivity of 0.05% w/w. No sample pretreatment is necessary. Analysis time is 15 min.     

Thermochemistry of the reaction catalyzed by lactate dehydrogenase

The thermochemistry of the reduction of pyruvate to lactate, in the presence of nicotinamide adenine dinucleotide (reduced form); catalyzed by the enzyme lactate dehydrogenase, has been studied. After approximately 120 experiments, a best value for the enthalpy of reaction has been determined to be ?14.80±0.30 kcal mol^?1. This reveals that the driving force for the reaction is almost completely enthalpic in nature. In addition, using the current methodology, it is possible to determine lactate dehydrogenase activity as low as 0.15 international units (325 Wroblewski units) per sample.     

Preconcentration of cobalt(II) in natural waters with 1-nitroso-2-naphthol supported on silica gel

A solid chelating material, 1-nitroso-2-naphthol supported on silica gel, provides a rapid and highly selective mean of preconcentrating cobalt(II) fro.     

Silmization of stainless-steel frits for use in trace metal analysis by high performance liquid chromatography

A simple method has been developed to minimize the interferences related to the metal parts of an analytical system used for trace metal analysis by HPLC. This is accomplished by blocking the exposed metal surfaces with an organosilane. The effect of the silanized stainless steel frits has been demonstrated by injecting diethyldithiocarbamate into columns with and without high metal surface area components. The coating of the silane is quite stable for routine use.     

The synthesis of cypridina etioluciferamine and the proof of structure of cypridina luciferin

An unambiguous synthesis of Cypridina etioluciferamine was accomplished in order to prove the structure of this important bioluminescent natural product. Several 2-aminopyrazine 1-oxides were synthesized in order to establish a spectroscopic method for determining the placement of substituents on the pyrazine nucleus of Cypridina etioluciferamine. Titanium tetrachloride was used to improve the yields of these compounds; for example, the yield of 2-amino-3-methyl-5-phenylpyrazine 1-oxide (19) from reaction of phenylglyoxal 1-oxime and α-aminopropionitrile was raised from 3% to 51% by the use of titanium tetrachloride. The pyrazine ring proton is found at τ 1·37 (DMSO-d₆). The isomeric 2-amino-3-methyl-6-phenylpyrazine 1-oxide (22) was similarly prepared and its pyrazine ring proton is found at τ 2·18. This large difference (0·81 ppm) in chemical shift was used to determine whether a 2-aminopyrazine 1-oxide was 5- or 6- substituted. Prepared in an analogous fashion were 2-amino-5-(indol-3-yl)-3-methylpyrazine 1-oxide (23) and 2-amino-5-(indol-3-yl)-3-(3-phthalimidopropyl)pyrazine 1-oxide (16). The structures of these compounds were verified by NMR spectroscopy. By treatment with Raney nickel and hydrogen gas, then 100% hydrazine hydrate, 16 was converted to 2-amino-3-(3-aminopropyl)-5-indol-3-ylpyrazine (5), isolated as the dihydrochloride. This compound, with the indole moiety definitely placed at C-5, is identical with Cypridina etioluciferamine dihydrochloride (IR, UV, TLC). These results show that the structures of Cypridina etioluciferamine and luciferin are correct as published.     

Iron(III) as activator for catalytic fluorimetric microdetermination of V(V)

The activation of the vanadium(V)-catalysed aerial oxidation of sodium 4,8-diamino-1,5 -dihydroxyanthraquinone-2,6-disulphonate by iron(III) is discussed. The oxidation product is intensely fluorescent and allows fluorescence-monitoring of the slow reaction, which is preceded by an induction period. On the basis of this investigation, an accurate method for determination of vanadium(V) at the 1-10 ng/ml level has been developed.     

Continuous spectrophotometric determination of copper, nickel and zinc in copper-base alloys by flow-injection analysis

Flow-injection methods have been developed for the determination of copper, nickel and zinc in copper-base alloys, including several types of brasses, deoxidized copper, beryllium copper and German silver. The system for copper and nickel involves the measurement of the absorbance of the copper(II) and nickel(II) aquo-complexes at 805 and 410 nm, respectively, after simple dissolution of the sample in a nitric acid-phosphoric acid mixture. The system needs no further reagents and the sample solutions can be analysed at rates of up to 280 /hr for copper (or nickel in German silver) without any carry-over. The system for zinc consists of automatic dilution of the injected sample with a thiosulphate-acetate buffer solution and the subsequent measurement of the absorbance of the zinc-Xylenol Orange complex at 568 nm. This system permits analysis rates of up to 90/hr for zinc solutions, with no carry-over. The procedures have been applied to standard copper-base alloys. The results agreed satisfactorily with the certified values. The precision ranges are 0.2-0.7% for copper and nickel and 0.5-0.8% for zinc.     

Spectrophotometric determination of palladium by solvent extraction as the Pd(II)-biacetylmonoxime 2-pyridylhydrazone complex

Determination of trace levels of palladium(II) is described. The method relies upon the extraction of palladium(II)-biacetylmonoxime 2-pyridylhydrazone (BMPH) from aqueous acidic solution into chloroform to form a purple-reddish complex. The molar absorptivity of the Pd-BMPH complex is about 7500 liters mol^?1 cm^?1 at 560 nm in the chloroform extract. The highly colored chloroform extract is suitable for spectrophotometric determination. The method devised has been applied to the determination of palladium in $\text{Pd}\text{CaCO}{}_3$ catalyst with good results.     

Spectrophotometric determination of tungsten(VI) with rutin

A new spectrophotometric method for the determination of microamounts of tungsten(VI) with rutin has been developed. The effect of a large number of foreign ions was investigated, and the separation and determination of tungsten in the presence of the interfering ions examined are presented.     

Solvent extraction studies on the mixed ligand complexes of lanthanides with antipyrine and perchlorate

Lanthanide ions are found to form colourless mixed-ligand complexes with antipyrine in presence of perchlorate at pH 4.0, and these are quantitatively extractable into nitrobenzene. The composition of the extracted species is shown to be metal:antipyrine:perchlorate = 1:6:3. The variation of the extraction constants with atomic number of the lanthanides is attributed to the "tetrad effect".     

Substoichiometric isotope dilution analysis for tin with salicylideneamino-2-thiophenol complexation in non-aqueous medium Application to the analysis of coal fly-ash

An accurate, precise and selective analytical method for traces of tin by substoichiometric isotope dilution has been developed. The method consists of.     

Determination of tellurium in copper, lead and selenium by atomic-absorption spectrometry after extraction of the trioctylmethylammonium-tellurium bromide complex

A simple, rapid and sensitive combined solvent extraction and atomic-absorption spectrometric method has been developed for the determination of tellurium in copper, lead, selenium and blister copper. Tellurium is extracted as the trioctylmethylammonium-tellurium(IV) bromide complex into butyl acetate and determined by flame atomic-absorption spectrometry of the extract. As little as 1 mug of tellurium in a sample can be determined. The extraction of tellurium from hydrobromic acid solution with trioctylamine has also been investigated.     

Observations on the formation of spark discharge and its influence by an external magnetic field

Described are a series of experiments executed to characterize the physical and chemical nature of spark discharge in argon at atmospheric pressure. Results are reported concerning the expansion properties of the spark and the distribution and longevity of cathode material in and around the spark channel following cessation of the discharge current. The nature of a previously reported symmetrical post-discharge torus is studied at high spark repetition rates. The interaction of residual vapor on following sparks is investigated. Basic features of the spark process are generalized with a set of Schlieren photographs that show bulk motion of the spark plasma. Time-resolved and space-resolved emission and absorption experiments on magnesium electrodes suggest a charged nature to the post-discharge environment. The bulk plasma character is probed further with external magnetic fields to determine the existence of charged species within the post-discharge torus, and the effects of magnetic forces on its formation.     

Basicity of transiton metal carbonyl complexes : XIII. Reactions of the π-cyclopentadienyl complexes of molybdenum and tungsten with aprotic acids

The aprotic acids HgCl₂ and SnX₄ (X  Cl, Br) react with the π-complexes C₅H₅M(CO)(NO)(L) (II, M  Mo W; L  PPh₃) by attack at the metal center. With HgCl₂ complexes II yield stable neutral 1:1 adducts CpM(CO)(NO)(L)HgCl₂(III). In the case of SnCl₄, complexes II initially produce the ionic 1:2 adducts [CpM(CO)(NO)(L)(SnCl₃)]⁺SnCl₅^-(IV) which, as a result of oxidative elimination of CO, turn into the neutral complexes CpM(NO)(L)(SnCl₃)(Cl)(V). In reactions of II with SnBr₄ the corresponding CpM(NO)(L)(SnB₃)(Br) complexes are formed directly. The formation of III–V is accompanied by a considerable increase of the frequencies ν(CO) and ν(NO). The structures of the complexes IV (M  Mo) and V (M  Mo) have been established by an X-ray structure analysis.