Fully automated photocolorimetric method for dissolved silica in oil well water rich in sulfide and bicarbonate.
A fully automated photocolorimetric method for dissolved silica in oil well water rich in sulfide and bicarbonate is proposed; the method is based on yellow silicomolybdic heteropolyacid. To eliminate the interference of sulfide a treatment with bromate is utilized. The analytical range is 1-30 mg L(-1); with the automatically performed dilution it extends up to 300 mg L(-1), RSD 5.5%.
Studies on the elimination of sulfide interference in the potentiometric determination of chloride using ion selective electrodes in a flow injection system
Detailed investigations have been reported on the application of a common procedure using bromate in nitric acid for the removal of the interference of sulfide in the direct potentiometric determination of chloride using silver-based ion selective electrodes in a flow injection system. It is shown that this procedure is not very efficient and carries a high risk of chloride underestimation. With increasing levels of sulfide the oxidation of chloride to elemental chlorine becomes progressively significant and under certain circumstances virtually no chloride is left irrespective of its initial concentration. Hydrogen peroxide in alkaline medium is proposed as a suitable alternative for the efficient removal of sulfide without any adverse effects on the potentiometric method.
Improving Hollow Fiber Dialyzer Efficiency with a Recirculating Dialysate System I: Theory and Applicability
The mathematical theory that underlies a novel non-regenerated recirculating dialysate system (RDS) for improving diffusive clearance in hemodialyzers is presented. The theory states the conditions that hemodialyzers must meet to be suitable in RDS optimization. We have verified the applicability of the RDS for several Cuprophan and polysulfone (PS) commercial dialyzers, showing that PS (synthetic) membranes achieve the highest increments of diffusive clearance. A numerical simulation analysis over more general conditions defined by the dimensionless groups of the system demonstrated that the highest diffusive clearance improvements are achieved in dialyzers operating with a low value of the diffusive mass-transfer area/blood flow rate ratio. This study has provided the base for the assessment of the performance of the RDS as compared to several high-efficiency systems, presented in Part II of this work [M. Prado, L. M. Roa, A. Palma, and J. A. Milán, Ann. Biomed. Eng. (2004) submitted].