A method for the determination of methylmercury has been improved by adding several steps to the ordinary process, such as the proteinase digestion of the samples and continuous extraction of the digest with benzene, and by utilizing p-nitrobenzyl chloride as an internal standard in gas chromatographic analysis. The method thus modified eliminated the emulsion formation, one of the most serious troubles in ordinary method, throughout the whole procedure. The new method revealed 93% of average recovery and less than 1.7% of deviation. The improved procedure was used to estimate the ratio of methylated mercury to total mercury in tuna fish and the results are presented.
Fundamental analytical conditions of the combustion method for the determination of mercury was examined. This method consists of the combustion of the material, collection of mercury as gold amalgam, and regeneration of mercury. In the determination of total mercury in fish tissues, sea and river bottom sediments, it has been clarified that the recovery of added mercury was not quantitative when the material was not pretreatment, but quantitative if treated beforehand with alkali. The method was markedly interfered by various acids such as sulfuric, nitric and hydrochloric acids. Therefore, in the determination of total mercury in fish tissues and bottom sediments, in which acid components are usually contained, the recovery became quantitative by addition of an alkaline solution to the material. Analysis on one material is completed within about 15 minutes, so that this method becomes more effective in the simultaneous treatment of a number of materials.
Chromium in water or soil was oxidized to a sexivalent state with potassium permanganate and extracted from the acidic aqueous solution with methyl isobutyl ketone containing trioctylamine, and then determined by atomic absorption spectrophotometry with air-acetylene flame. Extraction fficiency was about 100% by single extraction. This method was not interfered even in the presence of a large quantity of many other metals such as iron, nickel, copper, aluminium, zinc, lead, and manganese.
The method for the determination of micro (0.5-5 ppm of NH3) and macro (500-5000 ppm of NH3) amounts of ammonia in air were studied. For the purpose of micro analysis of ammonia in air, the indophenol method, in which sodium nitroprusside was added as a catalyzer of indophenol formation, was more excellent in the sensitivity, reproducibility and stability of color than the other methods for micro analysis. For the purpose of macro analysis of ammonia in air, the cupric carbonate method was relatively simple and reliable. Furthermore, 0.5% boric acid solution was adopted as an absorption medium of ammonia in air.
Examination on methylation of inorganic mercury in activated sludge, sewage, urine, and aqueous extract of feces gave the following results. (1) In the case of activated sludge, inorganic mercury was methylated irrespective of whether it was sterilized or not. This fact suggests that methylation by the sludge proceeded not noly biologically but also chemically. (2) In the case of the sediment of activated sludge, inorganic mercury was methylated, whether it was irradiated by xenon lamp not. (3) In the case of the supernatant of activated sludge, inorganic mercury was methylated only under light irradiation. (4) In the case of sewage, urine, and aqueous extract of feces, inorganic mercury was methylated only under light irradiation. These results suggest that inorganic mercury might be converted to methylmercury compounds in natural environment.
It was found that the sodium salicylic acid method is more excellent in point of reproducibility and simplicity than the other methods for the determination of nitrate nitrogen in water. Furthermore, the authors improved the precise conditions of procedures of the method, for example, the prevention of the interference of chloride ion and nitrite ion. The interference by chloride ion was prevented by the addition of the excess quantity of sodium chloride and that by nitrite nitrogen was also prevented by the addition of ammonium sulfamate. It was also ascertained that the method is not interfered by 50 ppm of ferrous or ferric ion, 2000 ppm of calcium and magnesium salts, 250 ppm of ammonia nitrogen and 500 ppm of free chlorine. The details of the procedure are as follows. Take V ml of the test solution containing 2∼20 μg of nitrate nitrogen and 2 ml of the standard solution, in which 20 μg of nitrate nitrogen are contained, in the 100 ml beaker respectively. To each solution add 1 ml of sodium salicylic acid-sodium hydroxide solution, which is prepared by dissolving 1 g of sodium salicylic acid in 100 ml of 0.01 N sodium hydroxide solution, 1 ml of ammonium sulfamate aqueous solution (0.1→100) and 1 ml of sodium chloride aqueous solution (0.2→100), then evaporate the solution to dryness on the water bath. After cooling to room temperature, and 2 ml of concentrated sulfuric acid, agitate gently sometimes and allow to stand for ten∼twenty minutes. When the large quantity of the residue remains by evaporation, it might be better that the sulfuric acid solution is heated on the water bath for ten∼twenty minutes. The absorbance is not influenced by heating. After adding carefully 10 ml of distilled water, transfer the solution to the 50 ml Nessler tube and add dropwise 10 ml of the sodium hydroxide solution (40→100) under cooling, then dilute to 25 ml with water. Measure the absorbance A obtained from the test solution and As obtained from the standard solution at the wave length of 410 mμ against the blank solution procedured in the same way. Concentration of nitrate nitrogen (C ppm) in the test solution was given by the following formula. [numerical formula]
In the atomic absorption spectroscopic determination of cadmium, ammonium pyrrolidyldithiocarbamate (APDC) was used as the chelating reagent but it was found that sodium diethyldithiocarbamate (DDTC) was better than APDC. Cadmium pyrrolidyldithiocarbamate was slightly soluble in most organic solvents and fairly soluble only in methyl isobutyl ketone, but cadmium diethyldithiocarbamate was easily soluble in most organic solvents. Therefore, extraction efficiency of cadmium complex from the aqueous solution with methyl isobutyl ketone was very good in the case of cadmium diethyldithiocarbamate. This experimental fact resulted in the simplified procedure and high recovery ratio.
Atomic absorption spectrophotometry of different kinds of organic lead compounds is said to give different values of lead even in the equivalent concentration of lead but this was found to be true only in the use of a premix burner and the use of total consumption burner was found to give equal absorptions for the equivalent concentration solutions of lead diethyldithiocarbamate, tetraethyllead, and tetramethyllead. Based on this fact, a simplified method for the determination of lead content in gasoline was established. In this method, the sample of gasoline is diluted with methyl isobutyl ketone and absorbance of this solution is measured at 2170 Å, using the total consumption burner. The standard solution is prepared from the standard aqueous lead nitrate solution by the addition of sodium diethyldithiocarbamate solution and extracting it with methyl isobutyl ketone. This method is not only convenient and accurate but is also safe because dangerous tetraalkyllead is not used as the standard substance. Lead content of 24 kinds of commercial gasoline was analyzed by this method.
Inorganic mercury (HgCl2) in activated sludge, sewage, urine, and aqueous extract of feces was alkylated under irradiation. A considerable amount of alkylmercury was formed by irradiation of inorganic mercury solution containing acetic acid or propionic acid in the presence of ammonia but only a small amount of alkylmercury formed in the absence of ammonia. This fact suggests that aminomercuric chloride (HgNH2Cl), formed by the reaction of mercuric chloride with ammonia, accelerated the photochemical alkylation of inorganic mercury. It was also found that creatinine, which was contained in sewage and urine, showed a photochemical alkylating ability but creatine, the open form of lactam ring of creatinine, did not show such ability.
A simple and sensitive method for the quantitative determination of organic mercury in waste water, fish tissues, and sea or river bottom sediments is described. This method consists of extraction of organic mercury from the material with benzene, reverse-extraction of the organic mercury with cysteine acetate solution, and combustion of the solution in the system described earlier. This method has the following features : (1) It is not necessary to use organic mercury such as methylmercuric chloride, ethylmercuric chloride, butylmercuric chloride, or phenylmercuric acetate, as the standard substance in the determination of organic mercury compounds, and inorganic mercuric chloride can be used as the standard in this method. (2) Organic mercury compounds can be completely separated from inorganic compounds by using benzene and cysteine acetate solution. (3) Analytical values of organic mercury compounds obtained by the proposed method agree completely with that obtained by the gas chromatographic analysis with electron captuer detector (ECD-GC method). (4) In carrying out this proposed method, it is not necessary to obtain any licence for handling radioactive rays which is required in the case of the ECD-GC method. Satisfactory results have been obtained by applying this proposed method to the analysis of organic mercury in various materials.
