Notes on analytical procedures : Determination of carbon dioxide

For the determination of carbon dioxide, methods suitable for general applications are described. a. Macro-titration method. The CO2 is absorbed in sodium hydroxide in a bubble column filled with glass beads. The excess of NaOH is titrated after the addition of BaCI2. b. Scmi-micro-titration method. The CO2 is absorbed in barium hydroxide, the excess of which is determined by titration with 0.1 n hydrochloric acid on cresolphthalein as the indicator. The absorption and titration are performed in a special vessel in which the liquid is kept in circulation by the injected stream of air. c. Gravimetrical method.Method b. is specially recommended.     

The submicro determination of carbon,hydrogen and nitrogen by a gas-chromatographic method

A method for the determination of carbon, hydrogen and nitrogen in organic samples weighing 40–80 μg is described. The sample is decomposed conventionally in a helium stream and the water formed is converted to acetylene. Nitrogen, carbon dioxide and acetylene are then separated on a silica-gel column, and the acetylene is burned to carbon dioxide by passage through copper oxide at 900° because the acetylene peak itself is not easily measured. Water from the second combustion is removed on silica gel and the three peaks emerging are measured by means of a micro thermistor cell. The standard deviations obtained for acetanilide are 0.31% for carbon, 0.28% for hydrogen and 0.11% for nitrogen. Results for other compounds are given and the parameters relevant to precision are discussed.     

Some developments in the chemical direct oxygen determination

This paper discusses modifications of the direct determination of oxygen in organic compounds by reduction with carbon. Two versions are considered, (a) a microscale method for compounds containing metals, phosphorus or boron, and including automatic non-aqueous carbon dioxide titration, and (b) a manometric method capable of analysing samples containing traces of oxygen down to 5ppm.     

Some investigations for a titrimetric determination of nanomoles of carbon

The ultramicrocoulometric acidimetric titration of carbon dioxide in an aqueous solution was compared with a simple volumetric titration in nonaqueous solution. The lower limit of determination was about 200 and 20 ng carbon, respectively. A determination of organic carbon (as benzoic acid or sucrose) in an aqueous solution takes less than 1 min.     

Coulometric titration of carbon dioxide on the micro scale

A method is described for the coulometric titration of milligram and submilligram amounts of carbon dioxide. Carbon dioxide is absorbed and titrated in dry acetone containing about 0.5% of methanol and saturated with potassium iodide, in a two-compartment cell. Thymol Blue is used as visual indicator. Current integration is carried out by means of a low inertia motor or a solid-state integrator. The generation efficiency is 99-100%. The method has been applied to the determination of small amounts of carbon (0-1 mg) in organic and inorganic materials and in aqueous solution.     

Die analytische anwendung der kohlendioxyddestillationUntersuchung von dekarboxylierungsreaktionen in wässriger lösung

Carboxylic acids which decompose spontaneously on boiling or by oxidation in aqueous solutions can be determined by titration of the carbon dioxide formed after distillation as described previously. Acetonedicarboxylic acid and p-aminosalicylic acid are determined by spontaneous decarboxylation. Hydrolysis must precede the determination for acetoacetic ester, phenylethylcyanoacetic ethyl ester and for carbonic acid esters. Oxidative decarboxylation allows determinations of glyoxylic acid, aldonic acids, sugar dicarboxylic acids, formic acid, oxalic acid and α-amino acids. The titration of the carbon dioxide formed can be done with 0.1 or 0.01 N solutions. The interference of atmospheric carbon dioxide is avoided by the use of pentane as a sealing liquid.     

Determination of carbon dioxide in coal and minerals

A simple and rapid semi-micro gravimetric procedure for the determination of carbon dioxide (0.005-60%) in coal, rocks and minerals is described. Particular advantages include small sample weights (0.25-1.0 g), high precision (relative standard deviation 0.01%) and improved speed of analyses (20 min). The apparatus is designed as a simple vertical layout to minimize bench space requirements and utilizes commercially available components to reduce the number of joints and rubber tubing connections. The low swept volume (165ml) gives good sensitivity and reduced analysis time, and the scavenging train ensures removal of water, halogens and gaseous sulphur compounds.     

A critical study of the determination of platinum with dimethylphenylbenzyl-ammonium chloride

A study of the recorded method for the determination of platinum with dimethylphenyl-benzylammonium chloride revealed defects which become serious for larger amounts. A revised procedure which yields accurate results for micro and semi-micro amounts is described. Samples which have been fumed in sulphuric acid solution may be handled with a slight modification of the recommended procedure.     

The determination of organic substances by the oxidation with permanganate: XVIII. The oxidation of malonic acid

The oxidation of malonic acid with permanganate was studied under various acidity conditions. Analytical procedures, based on oxidation with excess reagent in a sodium carbonate medium and titration of the oxalate or manganese dioxide formed or of unconsumed permanganate, are proposed. On the basis of successive oxidation in sodium carbonate and sulfuric acid media, a titration determination, involving complete oxidation of malonic acid to carbon dioxide and water, was developed.     

Miniaturisation of solid phase extraction method for determination of retinol,alpha- and gamma-tocopherol in human serum using new technologies

The aim of this study was to develop rapid and simple solid phase extraction (SPE) and HPLC methods for simultaneous determination of retinol, gamma- and alpha-tocopherol in human serum using a special auto sampler with micro titration plates.

Separation of vitamins was performed at ambient temperature using monolithic column on a HPLC containing rack changer for micro titration plates. As the mobile phase methanol with flow rate 2.5 mL min^?1 was used. The injection volume was 20 µL. Retinol was detected at 325 nm, gamma- and alpha-tocopherol were carried out at 295 nm, respectively. The total time of analysis was 1.8 minutes. Extraction method was developed using Spe-ed 96 C18, 100 mg/2 mL micro titration plates and SPE vacuum manifold. The consumption of the sample was 50 µL. Time of the analysis for 96 samples on one micro titration plate was 1.5 hour. In order to validate the developed method, precision, accuracy, linearity, detection and quantitation limits were evaluated. This method is suitable for rapid automated large-batch analysis of retinol, alpha- and gamma-tocopherol in small sample volumes of human serum.     

A sensitive and accurate automatic coulometric detector system for enzymatically produced carbon dioxide

A system for the determination of carbon dioxide liberated in an enzyme reactor is described. The properties of the system are illustrated by the determination of urea. Enzymatically generated carbon dioxide is expelled by boiling, dried and determined coulometrically. The lowest concentration of urea which can be determined with a relative standard deviation of 5% is 1 μM. Compared with other methods based on immobilized enzymes for the determination of compounds as carbon dioxide, this sensitivity constitutes an improvement of about two orders of magnitude. Possible application to sea water is discussed.     

In Process Citation

The method for the determination of sulphur in organic compounds (E. Debal and R. Levy, Bull. Soc. Chim. France, 1968, 426; 1971, 3374) by combustion in oxygen at 1310-1320 degrees C and coulometric titration of the sulphur dioxide formed is improved. Silver and 8-hydroxy-quinoline are successfully used to remove halogens (fluorine included) from combustion products. A new glass cell for the acidimetric titration of sulphur dioxide with an automatic coulometer is devised, with a water-jacket for its cathodic and reference compartments. The constant-temperature water-flow makes this determination easy to carry out with no drawbacks, even in varying ambient temperature.     

S-benzylthiouronium salts of some carboxylic acids,sulfonic acids,and phenols

116 S-Benzylthiouronium suits have been prepared and were, if possible, checked by titration with perchloric acid in glacial acetic acid on a semi-micro scale. Out of these, 110 are salts of carboxylic acids, 2 of snlfonic acids, and 4 of nitrophenols. The melting points determined according to a standard procedure are given.     

Determination of oxygen in certain gases : Improved winkler method

An improved method is described for the determination of micro-amounts of oxygen gas in argon, carbon dioxide, helium, hydrogen and nitrogen by the Winkler. procedure. The technique is such that a mean standard deviation of ± 0.33 ppm oxygen with a reproducibility of ± 0.67 is obtained for gases varying in oxygen content from 1 to 30 ppm. The results are reproducible on a day-to-day basis. The reagent blank is equivalent to about 2.5 ppm with a deviation of 0.2 ppm. The method can be used for oxygen gas determination from 1 to 1.50 ppm. The accuracy of the method is ± 0.1 ppm for the lower range of oxygen concentrations.The method may also be extended to higher oxygen-containing gases, except that the oxygen determination is made by titration and smaller gas samples are used.     

Volumetric titration of iron (III)-salts with disodium EDTA, using FeII-cacotheline as indicator

Summary A volumetric method has been developed for the determination of iron (III) with disodium EDTA, using a mixture of cacotheline and iron(II) as indicator. The titration of the iron (III) salt is carried out in a buffered solution ofph 4–5 in carbon dioxide atmosphere with magnetic stirring, until a pink color appears. The pink color is due to the reduction of cacotheline by ferrous-EDTA. The reduction occurs only when all the iron (III) is complexed by EDTA. The end point is sharp and the method has been found to give results accurate to±0.3 to±0.5 percent.     

Direct titrimetric microdetermination of tropeolin OO: I. Oxidation of tropeolin OO with ceric sulfate

Two quantitative methods for the determination of tropeoline OO in micro amounts are described. One of the methods is by direct titration with ceric sulfate resulting in the formation of a salt in the ratio of 1:2; in another method oxidation is effected at 51 equivalents. The reason for salt formation in the first method and the identification of formic acid is discussed. Maximum error for the first and second methods is 0.8 and 1.3%, respectively. The two methods are simple, accurate, and reproducible.     

Micro and submicro iodometric determination of arsenite and sulphite ions by amplification reactions

Two methods are described for the micro and submicro iodometric determination of arsenite and sulphite ions involving 3- and 6-fold amplification reactions, respectively. The arsenite method is based on oxidation with an excess of periodate, masking of the unreacted periodate with molybdate, and final iodometric titration of the iodate released. The sulphite method depends upon oxidation with iodine and removal of its excess by extraction with chloroform, and oxidation of the iodide formed to iodate, which is determined iodometrically as usual. The two methods are simple, rapid, and accurate. The average recoveries obtained are 99.9 and 99.3% for arsenite and sulphite, respectively.     

Determination of carbon dioxide evolution rates using a novel noninstrumental microrespirometer

A novel noninstrumental microrespirometer was developed to determine carbon dioxide evolution rates of solid or liquid samples at microL/h levels accurately and rapidly. The respirometer is based on the simple principle of acid-base titration at a steady-state of carbon dioxide absorption/evolution. The structure and operation of the microrespirometer are simple and the cost is modest in comparison to instrumental methods. The microrespirometer is suitable for laboratory studies and field routine examinations of food, agricultural, and environmental samples.