Ml Of Toluene Research Articles

Gas chromatographic determination of ultramicro amounts of nitrite ion in inorganic salts.

A new reagent, 1-methylamino-2-amino-4, 6-dibromobenzene (MADB) for the gas chromatographic determination of ultramicro amounts of nitrite ion was synthesized. It reacts with nitrite ion to form 1-methyl5, 7-dibromobenzotriazole(MDBT) which can be extracted into toluene. The extract is very sensitive to electron capture detection in gas chromatography. Therefore, the conditions for the gas chromatographic determination of ultramicro amounts of nitrite ion were investigated by using MADB. A typical procedure is as follows; Take the sample solution containing less than 60ng of nitrite ion into a 25ml of stoppered test tube and dilute to 15ml with distilled water. Add 2ml of concentrated hydrochloric acid and 0.5ml of MADB solution(2×10-4mol dm-3), and allow the mixture to stand for 30min. Extract the MDBT formed into 2ml of toluene by shaking for 5min, and wash the toluene extract with 4ml of 3mol dm-3hydrochloric acid. Inject 2μl of the toluene extract into gas chromatograph(ECD) and measure the peak height. The calibration curve(peak height) is linear in the range of 2.5 to 10ng of nitrite ion in 15ml of solution. The reproducibility at 3.5ng ml-1 was 3%. Trace nitrite ion in commercially available inorganic salts was determined by the proposed procedure.

Thin-layer chromatographic method for the quantitative analysis of nalidixic acid in human plasma

A sensitive and highly selective thin-layer chromatographic method for determining plasma levels of nalidixic acid is presented. Plasma (50 μl) was acidified with 50 μl 1 M orthophosphoric acid and extracted with 100 μl toluene. A 40-μl aliquot of the extract was spotted onto the thin-layer plate with the aid of a Desaga Autospotter and, after irrigation, the nalidixic acid on the plate was converted into a fluorescent compound by exposing the plates to hydrogen chloride gas for 10 min and then to strong ultraviolet radiation from a mercury lamp for 10 min. The fluorescence was measured quantitatively using a spectrofluorimeter equipped with a thin-layer chromatogram scanning attachment.

The gas chromatographic determination of selenium(IV) and total selenium in natural waters with 1,2-diamino-3,5-dibromobenzene

The total selenium and selenium(IV) contents in sea water and river water can be determined directly by a gas chromatographic method with l,2-diamino-3,5-dibromobenzene without preconcentration. The reagent reacts only with selenium(IV) to form a 4,6-dibromopiazselenol; other oxidation states of selenium must therefore be converted to the tetravalent state for total selenium determinations. The piazselenol formed can be extracted quantitatively into 1 ml of toluene from 500 ml of sample water. A method is proposed for the determination of selenium(IV) and total selenium in natural waters at levels as low as 2 ng l -1. Coastal sea water and river water in Japan contain 8–30 ng of Se(IV) and 20–50 ng of total Se per liter.

Extraction—photometric determination of trace amounts of nitrite in waters

Traces of nitrite in river water can be determined by extraction spectrophotometry. Nitrite in 100 ml of sample water at pH 1.5–3.0 diazotizes p-aminoacetophenone, which is then coupled with m-phenylenediamine at the same pH. The 2,4-diamino-4'-acetyl-azobenzene formed is extracted into 5 or 10 ml of toluene at pH 9 and the absorbance is measured at 450 nm. The molar absorptivity is about 2.3·lO 4 l mol −1 cm −1. The ions normally present in river water do not interfere. The nitrite contents in river waters in Okayama Prefecture, Japan, are 1–30 P.P.b.

Micrograms of TDI by chromatography.

An easy-to-use analytical method for determining toluene diisocyanate (TDI) vapor in air has been developed utilizing electron capture gas chromotography. Samples of 2, 4 TDI were collected by bubbling air through a series of impingers, each containing 10 ml of toluene. Concentrations down to 0.05 naograms of TDI per 5 µ1 portion of impinger liquid have been accurately measured. Using newer more sensitive electrometers, the possibility exists for measuring 1.0 picograms of TDI per 5 µ1 of toluene absorber. Valid TDI in air determinations as low as 0.005 ppm (one-fourth the current ceiling Threshold Limit Value) may be obtained in only 3 minutes of sampling time. Potentially, the time required for sampling may be reduced to 3 seconds, the.nominal time of one human respiratory cycle. This latter time period provides proper definition to ceiling values of importance in measuring pulmonary effects.

Gas-chromatographic determination of ultramicro amounts of selenium in pure sulphuric acid

Ultramicro amounts of selenium in pure sulphuric acid are converted into selenous acid with a bromine-bromide redox buffer solution. The selenous acid reacts quantitatively with 4-nitro- o-phenyl-enediamine to form 5-nitropiaselenol which can be extracted into toluene. The extract is very sensitive to electron-capture detection in gas chromatography, and the sensitivity is higher than that of 5-chloro-or 4, 5-dichloro-piaselenol. The calibration curve (peak heights) is linear up to 0.15 μg of selenium in 1 ml of toluene. Pure sulphuric acid, commercially available, contains 10 −6 $ ̃ 10 −5 % selenium.

Colorimetric determination of organic iodine using flask combustion

A simple colorimetric method for determining organic iodine involving the flask combustion and the successive dilution of liberated iodine in a definite volume of hydrocarbon solvent has been investigated.An organic sample containing about 2mg of iodine was burnt in a dry oxygen flask and 3ml of toluene or xylene was pipetted to the flaring lip at the top of flask. The solvent was drawn into the flask by loosening the stopper because of a reduced pressure produced in the flask after combustion, and the flask was stood for 5 minutes for complete absorption of iodine in the solvent. Twenty milliliters of the same solvent was further pipetted to the flask and the absorbance of the solution was measured at 505mμ for toluene or at 500mμ for xylene.A statistic comparison showed that the substitution of above solvents by benzene gave higher standard deviation of analytical results (Table VI) probably due to its higher volatility.A presence of chlorine above 4% in the sample gave lower analytical results due to formation of ICI. Sulfur in the sample gave sulfuric mist in the flask which made the solution turbid. This interference was avoided by standing the flask for 1 hour after the combustion until the sulfuric mist sank to the bottom of the flask.

Studies on the Autolysis ofAspergillus oryzae

An intracellular nuclease, which is known to be activated about three times in the course of autolysis of Asp. oryzae,1,2) was partially purified in the present work. A portion of mycelia (20.6 kg) obtained by submerged culture was autolyzed in 35 liters of water with 500 ml of toluene at 30°C for 40 hr. The nuclease was 18,300 times purified from the filtrate of the autolyzate by chromatographies using CM-cellulose and Sephadex G-100. The DNase activity and the RNase activity were eluted at the same position in each chromatography, and the ratio of two activities was constant throughout the last steps of purification.

Studies on the Autolysis of Aspergillus oryzae

An intracellular nuclease, which is known to be activated about three times in the course of autolysis of Asp. oryzae, 1, 2) was partially purified in the present work. A portion of mycelia (20.6kg) obtained by submerged culture was autolyzed in 35 liters of water with 500ml of toluene at 30°C for 40hr. The nuclease was 18, 300 times purified from the filtrate of the autolyzate by chromatographies using CM-cellulose and Sephadex G-100. The DNase activity and the RNase activity were eluted at the same position in each chromatography, and the ratio of two activities was constant throughout the last steps of purification.

Determination of ultramicro amounts of selenium by gas chromatography

4-Chloro- o-phenylenediamine reacts with selenous acid at pH 0-1 to form 5-chloropiaselenol, which is then extracted into 1 ml of toluene. The toluene layer is injected into an electron-capture detector gas Chromatograph. From the peak height selenium is determined, the minimum amount detectable being about 0.04 μg.