CS261575B1 - Process for the mineralization of carbonaceous materials - Google Patents

Abstract

The solution relates to the mineralization process carbonaceous materials, for example, for the following dissolution and chemical analysis k determining the content of chemical elements in trace elements concentrations in foodstuffs, feed, plant and animal tissues and other materials. The method can also be used to use in the determination of mineral construction carbonaceous material skeleton or environmentally friendly obtaining ash from carbonaceous materials for technological processing. Sample is heated to 300-400 ° C for a period of time 6 to 20 hours at normal pressure v. an oxygen flow of 0.03 to 0.15 ml.s. g_A of the sample to which oxidizing gas is added higher than oxidative properties oxygen properties selected from the group including ozone, nitrogen oxides, chlorine, optionally mixtures thereof, e.g. ozone oxides of nitrogen, chlorine oxides of nitrogen, v 1 to 5% vol.

Description

The invention relates to a method for the mineralization of carbonaceous materials, for example for subsequent dissolution and chemical analysis to determine the content of chemical elements in trace concentrations in consumables, feed, plant and animal tissues and other materials.

Decomposition of carbonaceous materials for chemical analysis is a procedure for treating a solid or liquid sample in its natural state or in a pre-treated state, eg by grinding, drying, homogenizing, etc. · It consists of two basic phases - mineralization both processes can occur simultaneously · The resulting decomposition product is a homogeneous solution. This solution may be subjected to chemical analysis by one of the chemical or physico-chemical methods. When determining the content, in particular trace concentrations of chemical elements, the limiting factor is the analyte concentration, ie the concentration of the chemical element determined, in the blank test · The blank test includes the analyte contributions and losses that occurred during the sampling with the sample, the use of tools, aids and utensils, the effect of the purity of chemicals, their quantity and other objective and subjective effects of the sample preparation staff. The background detected by the blank tests is used to correct the analytical results. In analytical chemistry, sample decomposition methods that use a small number of digestion operations and a small amount of chemicals are promising. This positively influences the ratio of analyte concentration in the sample to the blank. This results in a more favorable determination and reproducibility limit. The whole analytical sampling system, that is, from the sampling of the given reality to the analytical result, has then

- 2 261 575 high robustness and informative ability, which is the main objective of analytical chemistry ·

So far used methods of mineralization of carbonaceous materials, eg all kinds of food, feed, animal and plant tissues, use the technique of decomposition on wet or dry way, eventually their combination ·

The wet decomposition of the sample is, for example, the Kjeldahl mineralization described in Zeitschrift fur analytische Chemie 22, p. 366 of 1883, in which the sample is burned in a large excess of concentrated sulfuric acid by this acid in the presence of a catalyst. Zeitschrift fur analytische Chemie 10T, p. 11 of 1937 uses mixtures of nitric acid, perchloric acid and sulfuric acid under similar conditions. The disadvantage of both methods is the high concentration of acids and eventually the catalyst in the resulting solution, the necessity to separate any insoluble residue and dissolve it method.

Wet mineralization processes are often confused with procedures recommended by the manufacturers of analytical instruments, eg in the company material of Varian Techtron Food Analysis by Atomic Absorption ”, 1973. These procedures consist in the defined action of different combinations of acids and other chemicals on the sample to be analyzed. The result is actually the sample leach and it is not a true solution. The analyte is only partially, undefined dissolved, and its residue is bound in various ways to the solid particles contained in the extract. This considerably reduces the accuracy of chemical analyzes.

The decomposition in Paar's bomb, described for example by Puchel in the VUHU Mošt Newsletter p. 3, 1972 and in Hans Kůrněr's Neuberg company material from 1984, consists in burning the sample in pressurized oxygen, rinsing the bomb, separating undissolved particles and dissolving them acids. The disadvantages of this method are the poor solubility of high temperature combustion residues, extensive sample handling and contamination from the metallic, although tefloned bomb surface. This all leads to high and varying analyte concentrations in blank tests, limiting the accuracy of the analysis.

500 to 850 ° C, optionally in the presence of sulfuric acid as described by Feinberg and Ducauze in Analytical chemistry 52, p. 207

- 3261 575 of 1980, causing losses of volatile elements such as Cd, Pb and As, combustion in the air stream with nitric acid vapors at 550 ° C, published by Sago in Analyst 80, p. 789 of 1955, has been verified only for lead, in addition residues of incomplete burned organic matrix were observed ·

Another method of mineralization of samples for chemical analysis is combustion in a low-pressure plasma discharge, published by Gleit C.E. and Holland W.D. v Analytical chemistry 34, 1454, 1962 · Combustion takes place at a pressure of several hundred Pa at temperatures up to 200 ° C. Low temperature reduces analyte losses by volatilization; on the other hand, the use of low pressure largely suppresses this effect.

Cibulka J. et al. in the book Movement of lead, cadmium and mercury in agricultural production and biosphere, published by SZN in Prague 1986. It uses a sequence of operations: charring of sample dry matter at 400 ° C, long-term combustion at 500 ° C, additional mineralization with concentrated nitric acid and burning temperature 500 to 550 ° C. The disadvantage is again the use of relatively high temperature and difficult sample handling, so that both contamination and leakage of the analyte can occur.

The disadvantages of the different methods of mineralization of carbonaceous materials are eliminated by the method of mineralization of carbonaceous materials according to the invention in that the sample is heated to a temperature of 300 to 400 ° C for 6 to 20 hours under normal -1-1 pressure in oxygen flow at 0, 03 - 0.15 ml.sg of sample to which is added a gas with oxidising properties higher than the oxidising properties of oxygen selected from the group consisting of ozone, nitrogen oxides, chlorine or mixtures thereof, for example a mixture of ozone-oxides of nitrogen, chlor-oxides of nitrogen in 1 to 5% by volume

The mineralization of the carbonaceous material according to the invention takes place at temperatures of 200 to 500 ° C lower than in the dry mineralization methods used hitherto, so that the possibility of volatilization of the analyte is limited. The reaction of the individual components of the gas mixture produces unstable compounds such as nitrosyl peroxide or nitrosyl chloride, whose oxidizing effect is greater than the sum of the effects.

- 4,261,575 constituents · Due to the oxidizing capacity of the gas mixture, the sample is completely burned and the rest does not require additional oxidation. At the low temperature used and controlled oxygen supply, the sample does not ignite, coupled with its local overheating, leading to analyte losses. sintering of ash and reducing its reactivity and solubility. The choice of oxidizing gas mixture is dictated by the purpose for which the sample is decomposed, for example when chlorine-forming elements such as Ge, As, Sn, Sb, Pb, etc. are to be determined, chlorine is not used. The structure of the ash obtained corresponds to the structure of the originally bound ash, the ash is in activated physico-chemical form and easily decomposes! using a small amount of mineral acids. The resulting solution therefore has a low and precisely defined acid concentration. The number of operations to obtain the solution is small, resulting in very low and constant blank values. There is minimal need for pure chemicals for decomposition. The method is universal, a large number of types of different materials can be processed with only minor modifications of conditions. A large number of samples can be processed using a multi-site mineralization plant.

Example 1

A 2 g dry animal muscle sample was heated to 400 ° C for 20 hours at an oxygen flow rate of 0.06 ml / sec. With the addition of 5% nitrogen oxides.

Example 2

A 2 g sample of rye flour was heated to 400 ° C for 18 hours at an oxygen flow rate of 0.2 mL with the addition of 5% nitrogen oxides and 1% ozone.

Example 3

Cotton sample weighing 0.6 grams was added over 6 hours heated to 300 ° C in an oxygen stream at a flow rate of 0.09 ml.s ^"1 supplemented with 5% ozone.

Example 4

A sample of rye straw, weighing 1 g, was heated at 380 ° C for 12 hours at an oxygen flow rate of 0.1 ml / sec. With the addition of 1% nitrogen oxides and 5% ozone.

Example 5

A 2 g sample of mineral oil was heated to 300 ° C in an oxygen flow of 0.1 ml / sec for 20 hours with the addition of 1% nitrogen oxides and 5% chlorine.

Example 6

261 575

A 1 g butter sample was heated to 350 ° C for 15 hours in an oxygen stream of 0.05 ml · s * * with the addition of 5% nitrogen oxides and 1% chlorine ·

In all examples, the mineralization product was loose ash, which was easily dissolved directly in 15% nitric acid. The ashes of rye straw and flour were fumed with hydrofluoric acid and perchloric acid before dissolution.

The method of mineralization of the carbonaceous materials according to the invention can also be used to detect the construction of a mineral skeleton of carbonaceous materials or to gently extract the ash of carbonaceous materials for processing.

Claims (1)

SUBJECT OF THE INVENTION Method of mineralization of carbonaceous materials; characterized in that the sample is heated to a temperature of 300 to 400 ° C for 6 to 20 hours under normal pressure in a stream of oxygen with a flow rate of 0.03 to 0.15 ml. are the oxidising properties of oxygen; selected from the group consisting of ozone, nitrogen oxides, chlorine or mixtures thereof, for example, a mixture of ozone oxides of nitrogen, chlorine oxides of nitrogen, in an amount of 1 to 5% by volume;