Two approaches of down scaling of complexometric titration for magnesium contents determination in rubber latex: field test kit and microfluidic thread-based analytical device (uTAD)

First approach, a simple, low-cost and portable field test kit based on colorimetry with detection by naked eye was develop for determination of magnesium content in rubber latex (RL). The miniaturized complexometric titration between Mg2+ and EDTA without any masking agent was a key reaction in this developments, which was designed according to the concept of green chemistry by reduction of waste generation and chemical and time consumption. The system enabled quantification of magnesium content in RL at low concentration with the detection limit being <50 mg L-1, small sample volume uptake (0.18 g, sampling by a small spoon) and use of <1.5 mL reagent volume which was >70 times less than that applied in the conventional method. Moreover, with the presence of potential interference ions, greater selectivity towards magnesium was observed. Furthermore, the reagents used in out developed test kit were stable for >6 months at room temperature. The results obtained on real samples were in agreement with those obtained from the conventional complexometric titration (ISO 17403:2014(E)) method. The proposed techniques a low-cost, rapid, simple, selective and on-site analysis of magnesium content in RL.
Second approach describes a simple complexometric titrations for analytical detection by measuring the length of color change on indicator treated thread. A novel thread-based analytical device (TAD), fabricated from 15 cm of untreated cotton thread, provide an easy-to-use platform for the rapid measurement of analyze concentrations in aqueous solutions. Threads was fixed to a box platform to allow capillary wicking of liquid samples, free from contact with outside surfaces. In this method, interaction between deposited reagents and analyze within sample produces colored zones of differing lengths on the threads within only a few minutes. The length of the colored zones analyzed by unaided human eyes using the printed scales correlates with the concentrations of the analytes in the samples. Complexometric titration using TAD also proposed for Mg2+ monitoring in rubber latex samples. Threads were firstly pretreated with Eriochrome Black T (EBT). Two threads were then treated with two different concentrations of ethylenediaminetetraacetic acid (EDTA) in N-cyclohexyl-3-aminopropane sulfonic acid (CAPS) buffer at pH 10. They were then tied together to make a central knot before being affixed to a supporting of box platform for ready to analysis. 6 L of sample solution was then applied to as prepared TAD. The length of purple color product generating on thread was proportional to the concentration of Mg2+ in samples provided working concentration range of 25-1000 mg. L-1. Greater selectivity toward Mg2+ compared with potential interference ions was examined. Furthermore, our developed TAD was applied for analysis of real samples which showed results being in agreement with those obtained by classical titrations.