Запропоновано методику непрямого спектрофотометричного визначення ортофосфату, що базується на знебарвленні у його присутності комплексу Zr(IV) з Aрсеназо І. За оптимальних умов визначення градуювальна залежність є лінійною у діапазоні концентрацій 0,24-1,0 мг РО43-/л, межа виявлення становить 0,07 мг РО43-/л за об"єму проби 10,0 мл. Методика була успішно апробована на стандартних та модельних зразках морської води.
Предложена методика непрямого спектрофотометрического определения ортофосфата, котораяосновывается на обесцвечивании в его присутствии комплекса Zr(IV) з Aрсеназо І. При оптимальных условиях определения градуировочная зависимость сохраняет линейность в диапазоне концентраций 0,24-1,0 мг РО43-/л, предел обнаружения составляет 0,07 мгРО4/лпри объеме пробы 10,0 мл. Методика была успешно апробирована на стандартных и модельных образцах морской воды.
An indirect spectrophotometric method for the determination of orthophosphate in brakish waters is proposed. The method is based on the discoloration of a Zr(IV) with arsenazo I complex in the presence of a detectable anion. The Zr(IV) and arsenazo I complex is chosen due to its satisfactory spectroscopic characteristics. Previously the system was used for the determination of fluoride in ca&re products for the oral cavity and bioactive supplements [30]. The present results proclaimed that the order of reagents" mixing had a decisive effect on the analytical response. However, in the case when Zr(IV) solution occured in excess, the mixin&g order was not of a great importance. Conversely, adding arsenazo I solution in excess demanded the adherence of the mixing order. Latter provided the largest difference between the analytical response obtained in the absence and in the presence of &phosphate for the preposed system. Accordingly, the most efficient interaction was observed after the binding of phosphate with Zr(IV) solution, followed by the reaction of residual Zr(IV) amounts with arsenazo I. It was shown that the analytical res&ponce could be detected either at the complex" absorption maximum (575 nm) or at the reagent"s absorption maximum (500 nm). However, wider linear ranges and lower detection limits were obtained for the signal detection at the complex" absorption maxi&mum. Among the electrolytes that form a marine water inorganic matrix the greatest impact had sulphates and fluorides on the developed system. Sulfates were removed by the precipitation with barium chloride in highly acidic medium. Fluorides were eli&minated by adding the equimolar quantity of Zr(IV) solution. Under optimal conditions the linearity range was 0.24-1.0 mg PO43-/L, the detection limit was 0.07 mg PO43-/L for the sample volume of 10.0 ml. The method was successfully applied to the or&thophosphate determination in standard solutions and artificial marine water solutions.
