Zaruba S. Microextraction in combination with optical detection methods for determination of anionic compounds of Phosphorus, Sulfur and Iodine

The Thesis is devoted to improving stages of the phase separation, mixing, extract selection and measurement of an analytical signal during the microextraction separation and concentration. Effectiveness of the proposed solutions is illustrated by development of new methods for determination of inorganic anions: iodide (total iodine), iodate, phosphate, sulfite and thiocyanate, which are based on various techniques of microextraction with the spectrophotometric detection. It has been found that higher alcohols (1-undecanol and 1-decanol) have the good extraction ability in relation to phosphorus heteropolyblues. Expediency of using a hybrid droplet-dispersed microextraction (МЕ) technique for determination of inorganic anions by an example of definition of orthophosphate-anion has been substantiated. It is shown that the rate of establishment of extraction equilibrium in the dispersive liquid-liquid microextraction (DLLME) based on solidification of a floating organic drop (DLLME-SFO) is much higher than that in the classical droplet liquid microextraction based on solidification of a floating organic drop (DLME- SFO) (10 and 120 minutes accordingly) while maintaining the ease of selection of an extract from the water phase surface. Freezing the extract in a dynamic mode allows to achieve the easy phase separation without the use of a centrifuge, which is usually used in microextraction. A new microextraction-photometric technique has been developed in the form of DLLME-SFO for definition of orthophosphate-anions in aqueous samples (river and tap water), which is based on the formation of a stibium-molybdophosphate complex followed by its subsequent reduction with ascorbic acid and extraction using 55 microliters of 1-undecanol. A microextraction-photometric technique in the form of a vortex liquid microextraction (VLLME) has been developed for determination of orthophosphate-ions in aqueous samples. The limit for detection of phosphate (expressed as Р) is 0.18 ϻg/l, and the duration of extraction is only 90 s. Interfering effect of up to 0.3 mg/l of As (V) can be eliminated by masking with sodium thiosulphate. For the first time, the possibility of using a co-solvent (tetrachloride carbon) is shown, and the advantages of its application are substantiated to change density of the organic phase in the vortex extraction determination of inorganic anions by means of an example of iodide-anion. This approach allowed to minimize the volume of the extraction solvent – amyl acetate, which is lighter than water, due to the possibility of separation and collection of the extract at the bottom of the extraction ware. It has been found that the microextraction determination of iodide in excess of iodate- anions in the form of ІА with astrafloksin in the hydrochloric medium goes through the stages of formation of a complex aggregate ICl2-, formation of ІА out of AF and extractive removal of ІА. A microextraction-photometric technique for determination of iodide in mineral waters has been developed. The advantages of using colorless counter-ions in the microextraction-photometric determination of anions are shown by an example of defining some inorganic forms of iodine in the form of ionic associate with anion I3– and colorless counter-ion – tetrabutylammonium cation (TBA+). Expediency of using N-bromosuccinimide (NBS) as an oxygen carrier, and oxalic acid as a reducing agent of excess of oxidizer has been proposed and substantiated. Microextraction-photometric techniques for determination of the main forms of iodine in mineral and sea waters and table salt – iodide- and iodate-anions, with a detection limit of 8.8 and 8.3 nmol/l accordingly, have been developed. The possibility of the simultaneous determination of I–, IO3– and total iodine in a standardized test solution using VLME is shown. The simultaneous determination of these ions is possible at a ratio of I– to IO3– from 10:1 to 1:10. Definition of I2 is not hindered by the 5000-fold excess of I– and IO3–. For the first time, the possibility of using an optical probe and the advantages of its application to conduct ME into a droplet is shown by an example of determination of sulfite- and thiocyanate-anion. The use of the optical probe allowed to combine selection of the extract and its transfer to the microchemical apparatus in one stage, which simplified and speeded up the analysis. Fixing a droplet of the extraction solvent on the probe increases its stability with the intensive mixing of the donor phase, which allows to significantly decrease the time for establishment of extraction equilibrium. Microextraction-photometric techniques for determination of sulfite-anions in food products (in the form of HS-DLME) and thiocyanate-anions in human saliva (in the form of DLME-DI) have been developed.