The extraction method of preparation of analytical samples
(57) Abstract:The invention relates to the preparation of solid samples environment for the quantitative determination of cadmium by physico-chemical methods. How is that for the extraction of cadmium from the surface and of the volume of natural objects use the dissecting system consisting of thiopurine in the number of 0,002-0,003 mol, trichloroacetic acid number of 1.2 to 1.6 mol, phosphoric acid number of 0.03 to 0.05 mol, and distilled water to 1 liter, which at room temperature of 25 ° C for 30 minutes, treated with natural material. The proposed method ensures maximum extraction of cadmium for a short time at room temperature. table 1. The invention relates to the preparation of solid samples of environmental objects (solids snow cover, suspended solids rivers and lakes, soil, sediment, and other solid samples) for the quantitative determination of cadmium optical, polarographic or other method of analysis.Known methods of dry [GOST 26929-94. Raw materials and food products. Preparation of samples. Mineralization for the determination of toxic elements] and wet ed methods of trace metal analysis: Biological and Evironmental Samples/Jon C. Van Loon. 1985/NY/Toronto/Vol.80. - 351 pp] particulate samples of natural objects to retrieve (desorption) of toxic elements such as cadmium, surface and volume of particles in the mixture of mineral acids. As a rule, as extractants of cadmium and heavy metals using a mixture of sulfuric, nitric and concentrated hydrochloric acid in various volume ratios depending on the object of analysis. Sulfuric and nitric acid act on the solid component of the sample as restrukturisasi and oxidizing agents, acid mixture, destroying and oxidizing natural compounds organic and inorganic composition. Hydrochloric acid acts in the acid mixture as complexes cadmium and heavy metals agent that binds heavy metal ions in the chloride complexes. Akin to a "Royal" vodka (a mixture of nitric and hydrochloric acid in a volume ratio of 3:1) on the metal gold when it is dissolved. However, the dry ashing requires careful control over the temperature ashing. So, if you increase the temperature more IS irreversibly lost cadmium and other volatile metals (bismuth, arsenic, mercury, lead, tin). You additionally need expensive refractory quartz ware. MDE wet ashing the mixture of acids requires special care (fume cupboard, individual protective equipment), additional time and labor costs.The proposed method sample preparation completely eliminates the above mentioned disadvantages, by providing the desired degree of extraction of cadmium, close to 100%.Known technical solutions closest to destination and technical nature of the claimed object is a method of preparation according to GOST 26929-94. Raw materials and food products. Preparation of samples. Mineralization for the determination of toxic elements. Total for the prototype and the claimed invention are the use of acids for desorption of cadmium in the solution from the surface and bulk solids samples. You should list the main disadvantages of the prototype:- the use of aggressive mineral acids (sulfuric, nitric, hydrochloric);- long-term (90 min) heat of analytical samples.The proposed method differs from the prototype in that aggressive (sulphuric, nitric, hydrochloric) acid is replaced in the application of phosphate (visivel) and trichloroacetic (particulate organic matter) acid. Acid provide a safe extraction of cadmium in the form of a complex with an organic reagent - tipitina (not in PR is anantnag system (water, trichloroacetic and phosphoric acid, thiopyran). In the present method does not require prolonged heating, which can cause irreversible loss of cadmium. Unlike the prototype in the claimed method provides the necessary extraction of cadmium in less time for 30 min at room temperature. While removing cadmium from the solid sample is provided serosoderjaschei organic nitrogenous reagent - tipitina.The invention consists in that for the extraction of cadmium from the surface and bulk solids natural object (total weight of 0.5-1 gram) with a degree of recovery 98-100% used four stratifying system volume of 10 ml, consisting of reagent - thiopurine (0,00002-0,00003 mol), trichloroacetic acid (0,012-to 0.016 mol), orthophosphoric acid (0,0003-of 0.0005 mol) and distilled water up to 10 ml In contrast to the prototype to achieve a technical result and obtain reliable expert estimates, close to 100%, the process of desorption of cadmium is implemented at room temperature of 25 ° C for 30 minutes the desired degree of extraction of cadmium is achieved by extraction of the metal in the organic phase in a volume of 1 ml, generated in the process rassle the practical definition (atomic absorption, polarography, emission spectrometry, spectrophotometry, and so on).The implementation of the invention is achieved as follows. The sample weighing 0.5 to 1 gram of natural material, such as solid particles of snow water obtained after filtration through a membrane filter IFA-MA NO. 6 (TU 6-05-1903-81), weighed on an analytical balance with an accuracy of 0.0002 g and placed in a clean extraction tube with a volume of 15 ml, equipped with a glass stopper. The extract is prepared as follows. Mix 4 ml of a 4M solution of trichloroacetic acid (reagent-grade) plus 4 ml of 0.1 M phosphoric acid (reagent-grade) plus 0,4546 g thiopurine plus distilled water to 10 ml of the Prepared sample natural material processed cooked extract for 30 minutes at a temperature of 25 ° C and then defended before the formation of the organic phase (1 ml). Next was collected by pipette 1 ml of the organic phase was diluted with bidistilled water in a volumetric flask of 25 ml and analyzed for total cadmium content by two methods: inversion voltammetry at the mercury film electrode and atomic absorption spectrometry. As a comparative prototype parallel hinge solid components of the snow cover was subjected to wet Aravali.The table presents comparative data for both methods of preparation of the same samples of snow. The table shows that regardless of the degree of particulate aerosols cadmium concentration of metal desorbed and claimed in a known manner, coincide within the statistical random error analysis. Moreover, the technology of sample preparation more attractive and technologically (pH 2-3, temperature 25 ° C, time: 30 minutes, security, aqueous-organic system with low cost of chemicals, water after extraction of cadmium can be easily cleaned up).The prototype, which is a mixture of concentrated sulphuric, nitric and hydrochloric acids, requires extra caution and required personal protective equipment for the analyst, and a good exhaust ventilation to remove toxic gaseous emissions: sulfur dioxide and nitrogen oxides generated during the processing of solid particles of natural objects. Preparation of samples in the prototype requires additional heating to 250-300C, heat resistant tubes, provided with check-in refrigerators, time decomposition of the samples more than 5-6 times (2.5-3 hours) compared with extraction, which provides a share of the/P>The extraction method of preparation of analytical samples of natural objects, namely, that for desorption of cadmium from the particulate nature of the material it is treated with a mixture of acids, characterized in that for metal recovery using aqueous-organic exfoliating system containing reagent thiopyran - 0,002-0,003 mol and organic - trichloroacetic - 1,2-1,6 mol and inorganic phosphoric - 0,03-0,05 mol of acid and distilled water to liters, which at room temperature of 25 ° C for 30 min, treated with natural material.
FIELD: semiconductor devices, detectors of ionizing radiation.
SUBSTANCE: cadmium telluride nanopowder with average particle size of 7-10 nm is placed into press-form and introduced into press chamber. Sample is pressed under 600-650 MPa at 20-25°C and held under pressure for 10-30 min. Obtained product (CdTe) has hardness of 1200 MPa that is more than by 2.5 times higher in contrast to known CdTe crystals.
EFFECT: bulk material of increased mechanical hardness.
SUBSTANCE: invention may be used for production of photo elements of solar batteries, for making solar batteries photo elements, for making optical devices, ionising-radiation detectors and catalysts. Method of obtaining nanoparticles of cadmium telluride with wurtzite structure includes decomposition of cadmium telluride crystals in melt of potassium hydroxide or natrium in nitrogen atmosphere till complete homogenisation of obtained product. Melt is cooled to (-15)-(-20) °C and water-spirit-ammoniac mixture is added gradually during mixing and cooling with temperature (-15)-(-20) °C till obtaining of final solution with temperature not exceeding -5°C. Precipitated cadmium telluride is filtered.
EFFECT: invention allows to obtain nanoparticles of cadmium telluride with wurtzite structure and size about 1 nm and to simplify procedure of its obtainment.
SUBSTANCE: invention is related to technology of nanomaterials production, in particular to cadmium telluride nanoparticles, and may be used for development of optical instruments, detectors of ionising radiations, catalysts. Initial single crystals of cadmium telluride are decomposed in alkaline melt: sodium or potassium hydroxide in atmosphere of nitrogen till homogenisation of melt, which is then cooled down to 0°C, processing it by water with gradual addition of hydrochloric acid to obtain value pH of final solution equal to 2-3 at the temperature of not higher than 1-5°C and residue of cadmium telluride with nanoparticle size of around 2 nm with sphalerite structure, which is then filtered.
EFFECT: simplified technology, reduction of dimensions of produced nanoparticles down to 2 nm and their production in stable cubic phase (sphalerite).
SUBSTANCE: invention can be used in chemical industry. Further polymerisation of the obtained dispersions enables to obtain block optically transparent fluorescent composite materials. The invention can be used in making diode lasers, light sources, light filters, displays, nonlinear absorption media, photodetectors and in other fields where conversion of energy is necessary. The method involves preparation of a solution containing cadmium salts dissolved in acrylic monomers, and adding a solution of hydrogen sulphide in methyl methacrylate, with simultaneous stirring and irradiation of the reaction medium with UV radiation. The precursor which is added to the methyl methacrylate medium is cadmium carbonate which is pre-dissolved in methacrylic acid and the reaction medium is additionally blown at the moment of illumination and adding hydrogen sulphide to methyl methacrylate with argon gas for 1 min at a rate of 0.2 l/min. The methyl methacrylate (MMA) comonomer used can be a second monomer of 2-hydroxyethyl methacylate (HEMA), with the weight ratio of components MMA(1-X):HEMAX, where 0<x≤1.
EFFECT: obtaining block optically transparent fluorescent composite materials.