Automated fast reaction-rate system for phosphate determinations in the millisecond range

Abstract

A new approach has been developed for precise and accurate quantitative determinations of phosphate with analysis times in the millisecond range. The method utilizes a completely automated stopped-flow system with direct digital readout of initial reaction rates to measure the initial rate of formation of 12molybdophosphoric acid from phosphate and Mo(VI) in acid medium. This rapid reaction yields digital rate data proportional to the phosphate concentration about 100 milliseconds after the reagents are automatically mixed. The phosphate concentration from 0.1 ppm and up can be read out directly on the digital meter or a printer. With the automatic sampling

An Indirect Spectrophotometric Method for the Determination of Silicon in Serum, Whole Blood and Erythrocytes

“…As can be seen from the curve, the peak of the phosphomolybdate complex did not appear in the first 10 ml fraction. It can be understood that the complex dissociates into phosphate and molybdate through a rapid equilibrium 42 during the column treatment. This seems to indicate that the indirect method is free not only from the salt error, but also from the interference of phosphate.…”

Kinetics and Equilibrium of Binding of Fe3+ by a Fulvic Acid: A Study by Stopped Flow Methods

“…successfully exploited recently by groups in the 'Supported by the National Research Council of United States (2,3) and the Soviet Union (4). Canada and the Research Incentives Office, Inland The most promising experimental approach is Waters Directorate.…”

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“…A rather long development program was thus required to develop the new automated equipment that would provide very rapid mixing and readout of rate information. After the automated system was developed it was then possible to determine phosphate directly 26 utilizing the primary reaction shown in Equation 4. It is feasible to make as many as 3,000 determinations of phosphate concentration per hour with this type of system.…”

“…The series combination of the integrator (OAl) and inverter (OA2) serves as the feedback element of the control amplifier (OA3) which maintains point S at vertical ground. Recalling Equation 19, the rate of change of the potential established in the feedback loop is given by: de s (26) Any voltage change at point S is amplified and applied to the input of OAl. The integrated voltage at the output of OAl is inverted at OA2 and applied to the summing point (S) of OA3.…”