This paper describes the use of flow injection (FI) techniques for the determination of iodine in urine, based on the catalytic effect of iodide in the redox reaction between Ce(IV) and As(III). The proposed procedures minimize errors in the conventional batch method arising from the reading of absorbance at a fixed time after addition of Ce(IV) reagent. Two FI systems, for the continuous and stopped modes of operation were assembled. In the continuous-FI system, a thermostated bath was used to increase the sensitivity. However this is not necessary for the stopped-FI system. The two systems are comparable in terms of sensitivity, sample throughput and detection limit. The continuous-FI and the stopped-FI exhibited detection limits (3 sigma) of 2.3 and 3 micrograms I l-1 respectively. Both systems have equal sample throughputs of 35 samples h-1. Calibration plots for both techniques are linear. The FI procedures provide very short analysis times compared to the batch procedure. Using the linear regression test, there is no significant difference between the results from the four methods, i.e., continuous-FI, stopped-FI, conventional method and ICP-MS. The proposed methods are readily applicable for automation and can be an alternative to the conventional procedure for the survey of the iodine deficiency disorder. A condition for sample digestion is also proposed to reduce the amount of chloric acid required for complete digestion. Kinetic information of the reaction can also be obtained from the stopped flow mode.
This work presents new chemical sensing devices called "membraneless gas-separation microfluidic paper-based analytical devices" (MBL-GS μPADs). MBL-GS μPADs were designed to make fabrication of the devices simple and user-friendly. MBL-GS μPADs offer direct quantitative analysis of volatile and nonvolatile compounds. Porous hydrophobic membrane is not needed for gas-separation, which makes fabrication of the device simple, rapid and low-cost. A MBL-GS μPAD consists of three layers: "donor layer", "spacer layer", and "acceptor layer". The donor and acceptor layers are made of filter paper with a printed pattern. The donor and acceptor layers are mounted together with a spacer layer in between. This spacer is a two-sided mounting tape, 0.8 mm thick, with a small disc cut out for the gas from the donor zone to diffuse to the acceptor zone. Photographic image of the color that is formed by the reagent in the acceptor layer is analyzed using the ImageJ program for quantitation. Proof of concept of the MBL-GS μPADs was demonstrated by analyzing standard solutions of ethanol, sulfide, and ammonium. Optimization of the MBL-GS μPADs was carried out for direct determination of ammonium in wastewaters and fertilizers to demonstrate the applicability of the system to real samples.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.