Trace element determination in environmental pollution: A kinetic method for mercury estimation

A method is developed for the estimation of mercury in trace concentrations by measuring spectrophotometrically its catalytic effect on the rate of substitution of p-nitrosodiphenylamine into hexacyanoferrate(II). Under the specified conditions the detection limit is found to be 2.0 x 10(-8)M relative standard deviation 1.4%. The effect of other ions is discussed.     

New spectrophotometric method for the determination of phenolic hormones

A new simple, selective and accurate spectrophotometric method is described for the determination of mono- and dihydric phenolic hormones (oestrogens and catecholamines) by nitration at 50 degrees and 100 degrees , respectively, for 10 min, followed by treatment with alkali. Coloured products with absorption maxima at 430, 385, 430, 380 and 380 nm, linearly proportional to the concentration of oestrone, oestradiol, ethinyloestradiol, adrenaline and noradrenaline, respectively, are obtained. Information is presented on the effect of nitration time, temperature, solvents, and alkali concentration. The method is satisfactorily applied to the determination of these hormones in the range 10-50mug ml in the final solution, of volume 10ml. The relative standard deviation is +/- 0.5% and no interferences are caused by non-phenolic hormones.     

Application of an intensified diode array system to diagnosis of matrix effects and the rapid sequential determination of thiamine and riboflavin with fluorescence detection

The unique capabilities of a multiple wavelength spectrofluorometer based on an intensified diode array detector are used for diagnosis of matrix effects and for rapid sequential determination of two analytes. This system is used to investigate problems due to background fluorescence, blank reactions, and scattering for the determination of thiamine in cereal and urine samples by a fluorometric kinetic procedure. A novel determination of thiamine and riboflavin in vitamin pills is based on monitoring the native fluorescence of riboflavin over one wavelength region, and the rate of formation of fluorescent thiochrome from thiamine over another wavelength region, after a computer-controlled change in the pH of the reaction mixture.     

Spectrophotometric determination of beryllium with calcichrome

A method is established for the spectrophotometric determination of small amounts of beryllium as a 1:1 complex with Calcichrome in slightly acidic solution. Beer's law is obeyed over the range 0.05-0.6 ppm Be in the final solution and the apparent molar absorptivity is 9.7 x 10(3) l.mole(-1). cm(-1) at 625 nm. Up to about 15 mug of beryllium in the final solution can be sensitively and selectively determined with a relative error of less than 2% in the presence of EDTA as masking agent.     

Spectrophotometric determination of iron with 1-hydroxy-4-sulpho-2-naphthoic acid

1-Hydroxy-4-sulpho-2-naphthoic acid (H(3)L) is proposed as a spectrophotometric reagent for determination of iron. It gives a red-brown chelate, FeL(6-)(3), with lambda(max) 500-520 nm at pH 8 ( = 3.3 x 10(3) l. mole(-1). cm(-1)). In this wavelength region the reagent has no absorption. Most common cations and oxo-anions do not interfere. In the determination of iron in polymetallic iron ores and aluminium alloys the relative error and relative standard deviation of the method were found to be better than 1 and 0.5%, respectively. 1-Hydroxy-4-sulpho-2-naphthoic acid seems to be a more sensitive and accurate reagent for iron than 5-sulphosalicylic acid, and the number of interfering ions is smaller than in the 1,10-phenanthroline or thiocyanate methods.     

Influence of volatile hydride-forming elements on antimony determination by atomic-absorption spectrometry with hydride-generation

A study was undertaken to determine the interfering effects of arsenic, bismuth, germanium, lead, selenium, tin and tellurium on trace determination of antimony by atomic-absorption spectrometry with hydride-generation. A 1% NaBH(4) solution was used as reductant and a small amount of oxygen was added to the hydrogen produced, to support the combustion and atomization of SbH(3). The interference from selenium in the determination of antimony is removed if potassium iodide-ascorbic acid solution or copper sulphate is added to the sample solution. The interference of tin and tellurium can also be avoided by adding potassium iodide-ascorbic acid solution. A possible interference mechanism is discussed.     

Rapid determination of dissolved silica in natural waters

A method is described for the simple and rapid determination of soluble silica in natural waters, based on the well-known molybdenum blue complex. Soluble silica reacts with an excess of ammonium molybdate at pH 1.5–2 to form silicomolybdate. Citrate/tartrate addition reduces phosphate and arsenate interference, if present. An acid solution if iron(II) and fluoride ions is used as reductant. Absorbance is read at 828 nm. The solution is stable at least 2 hr. Traces of silica are determinable down to 10 μg SiO₂ liter^?1 with an error of ± 3%. The analysis time is about 10 min. The effect caused by several other ions has been determined.     

The quantitative determination of hydrated calcium sulphates in cement by use of self-generating atmosphere thermogravimetry

A method is described for the quantitative determination of hydrated calcium sulphates in cement by use of self-generating atmosphere thermogravimetry. The method is rapid and precise and can be applied (with a suitably modified sample container) with most thermogravimetric equipment.     

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.     

A fluorimetric kinetic method for the determination of tonin activity in rat submaxillary glands

A method for the kinetic determination of tonin activity in rat submaxillary gland extracts is described. The method is based on the fluorogenic reaction of o-phthalaldehyde with the dipeptide histidyl-leucine generated in the enzymatic hydrolysis of angiotensin I. The reaction is monitored by fluorescence at 440 nm. At pH 7.5, the method allows the determination of 2–15 nmol/ml histidyl-leucine with relative standard deviation of 6%.     

Spectrophotometric determination of nickel with biacetyl bis(4-phenyl-3-thiosemicarbazone)

A simple method is described for the rapid spectrophotometric determination of nickel with biacetyl bis(4-phenyl-3-thiosemicarbazone). The yellow color is measured at 460 nm (? = 22,800 liters mol^?1 cm^?1) against a reagent blank at pH 2.5 in a solution containing 60% ($\text{v}\text{v}$) dimethylformamide. Beer's law is obeyed over the range 0.2–2 ppm of nickel.     

Fluorimetric determination of iron(III) by a kinetic method

A sensitive and relatively interference-free method for the kinetic determination of iron(III) is described. The method is based on the catalytic action of this ion on the autoxidation process of 4,8-diamino-1,5-dihydroxyanthraquinone-2,6-disulfonate (disodium salt), to produce a strong pink fluorescence that increases with time. The reaction is monitored at 585 nm, when excited at 525 nm, and the initial rate method is applied to perform the analytical procedure. The influence of reaction variables and the effect of foreign ions are discussed. Iron(III) contents between 0.1 and 1 μg ml^?1 can be determined with R.S.D. of ± 3.7%.     

Electrochemical behavior of 1-nitroso-2-naphthol in aqueous solutions: Evaluation of the rate constant for the intervening chemical step in an ece mechanism from stirred-mercury-pool chronoamperometric data

In aqueous solution 1-nitroso-2-naphthol is reduced to 1-amino-2-naphthol by an ECE mechanism. The homogeneous first-order rate constant for the chemical reaction of the intermediate can be evaluated with the aid of current-time data obtained during controlled-potential electrolysis with a stirred mercury-pool working electrode, using the Karp-Meites equation for the dependence of quantity of electricity on time, and is found to be equal to 1.1 ± 0.1₅ s^?1.     

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.     

On the importance of bulk activity measurements for organic electrosorption studies

The importance of considering the bulk activities of both the organic compound and of the electrolyte is discussed for the case of organic electrosorption studies. The possible errors in the determination of the relative surface excess of the organic compound due to both of these factors separately and together are discussed. It is shown that the most serious errors due to either of these causes will occur in the region of organic concentrations in which the organic compound deviates negatively from Henry's law. Equations are derived which express these errors.     

Study of hydrolysis of amido-substituted gamma-butyrolactones by pH-stat titration and ultraviolet spectroscopic analyses

pH-Stat titration and ultraviolet absorption spectroscopy have been used to study the rates of ring-opening in a series of gamma-butyrolactones and their analogues. The half-lives for the lactones can be related to Hammett inductive and steric parameters.     

Electrothermal atomization of calcium and strontium in a molybdenum micro-tube

The excitation and ionization of calcium and strontium in a molybdenum micro-tube atomizer and their use in atomic-absorption spectrometry are described. Increasing hydrogen flow led to complex calcium atomization profiles for absorption measurements, but decreasing hydrogen flow resulted in higher atomic emission. Ionization of calcium and its suppression by potassium were also observed. Strontium was measured effectively by atomic absorption because of the higher sensitivity. Increasing hydrogen flow resulted in a lower atomization temperature and higher absorption for strontium, while decreasing hydrogen flow resulted in higher atomic emission. No interference from 100-fold amounts of magnesium, calcium and sodium was found for atomization of strontium, but 100-fold amounts of aluminium shifted the peak temperature for strontium though with no variation of appearance temperature and peak absorption. A small shift in peak temperature was observed for strontium in the presence of 100-fold amounts of phosphate.