Application of composite polyvinyl alcohol – magnetite for increase of the accuracy of optical micrometry method
Abstract
The method of optical micrometry (MOM) is based on the dependence of the sensor volume, which is usually a polymer gel granule, on the composition of the solution in which this granule is located. It is assumed that the sensor has the shape of a ball, but in practice, usually its shape is somewhat different from spherical and has the shape of an ellipsoid of revolution. These are minor differences, but it is desirable to take them into account for calculations. For this purpose, in this study it was proposed to fix the position of the sensor in the cell. In this case, the change in the degree of swelling of the granule is not accompanied by a change in its position in the cell and the deviations of its shape from spherical are averaged. This result is achieved by introducing magnetite into the sensor (granule) and placing a magnet under the cell with the analysed solution. The study describes a method for the formation of granules (sensors) based on cross-linked polyvinyl alcohol (PVA) with magnetite deposited in them. Studies have shown that in this case the presence of magnetite in the granules does not affect their degree of swelling. This fact was also confirmed by studies of swelling kinetics. The swelling kinetics of both granules with magnetite and without it was studied in solutions of a nonsorbable electrolyte (KS1) and in electrolyte solutions (MgCl2), where the dissolved electrolyte forms a coordination bond with the polymer. Analysis of the results obtained in the study allowed to draw at least two conclusions. First, the use of gels with magnetite as sensors in the method of optical micrometry practically solves the problem associated with the search for spherical granules necessary to improve the accuracy of the method. The fixed position of the granule in the cell allows to perform measurements on granules in the form of ellipsoids of revolution. Secondly, it was shown that the method of optical micrometry, supplemented with the equipment and material specified in the study, allows to measure the concentrations of analysed solutions with an accuracy of 0.4%.
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References
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