Development of an Optode Detector for Determination of Anionic Surfactants by Flow Injection Analysis

Microfluidic paper-based analytical device with a preconcentration system for the measurement of anionic surfactants using an optode detector

The paper discusses the development of a low-cost, simple, and sensitive on-site measurement system for anionic surfactants (AS), specifically sodium alkylbenzene sulfonate (LAS), using a microfluidic paper-based analytical device (μPAD) with an optode as a detector. The need arises due to the discharge of AS-containing wastewater into natural environments, posing risks to aquatic organisms. Traditional methods for AS measurement have drawbacks like the use of harmful solvents, time-consuming procedures, and the need for expensive equipment, prompting the exploration of alternative approaches. The μPAD incorporates a sample solution preconcentration system using filter paper modified with chitosan. The optode, a chemical sensor detecting analytes optically, is employed for AS detection. When a large volume of AS is added to a positively charged modified filter paper with chitosan, the AS is adsorbed and concentrated on the filter paper. The concentrated AS is eluted with a small volume of alkaline solution, and the eluted AS is detected by the optode in the μPAD. The μPAD with preconcentration provides improved sensitivity and a broader range of detection compared to the method without preconcentration. In the present μPAD method, linear alkylbenzenesulfonate (LAS) in the concentration range of 0.1 to 10 μmol dm-3 was measured. The developed μPAD offers advantages such as portability, cost-effectiveness, and negligible interference from coexisting substances in environmental water samples. The μPAD method was applied for the determination of LAS in tap water and river water.

Simultaneous determination of volatile phenol, cyanide, anionic surfactant, and ammonia nitrogen in drinking water by a continuous flow analyzer

This study developed a method for the simultaneous determination of volatile phenol, cyanide, anionic surfactant, and ammonia nitrogen in drinking water, using a continuous flow analyzer. The samples were first distilled at 145 °C. The phenol in the distillate then subsequently reacted with alkaline ferricyanide and 4-aminoantipyrine to form a red complex that was measured colorimetrically at 505 nm. Cyanide in the distillate subsequently reacted with chloramine T to form cyanogen chloride, which then formed a blue complex with pyridinecarboxylic acid that was measured colorimetrically at 630 nm. The anionic surfactant reacted with basic methylene blue to form a compound that was extracted into chloroform and washed with acidic methylene blue to remove interfering substances. The blue compound in chloroform was determined colorimetrically at 660 nm. Ammonia reacted with salicylate and chlorine from dichloroisocyanuric acid to produce indophenol blue at 37 °C in an alkaline environment that was measured at 660 nm. The relative standard deviations were 0.75-6.10% and 0.36-5.41%, respectively, and the recoveries were 96.2-103.6% and 96.0-102.4% when the mass concentration of volatile phenol and cyanide was in the range of 2-100 μg/L. The linear correlation coefficients were ≥ 0.9999, and the detection limits were1.2 μg/L and 0.9 μg/L, respectively. The relative standard deviations were 0.27-4.86% and 0.33-5.39%, and the recoveries were 93.7-107.0% and 94.4-101.7%. When the mass concentration of anionic surfactant and ammonia nitrogen was 10-1000 μg/L. The linear correlation coefficients were 0.9995 and 0.9999, and the detection limits were 10.7 μg/L and 7.3 μg/L, respectively. When compared to the national standard method, no statistically significant difference was found. This approach saves time and labor, has a lower detection limit, higher precision and accuracy, less contamination, and is more appropriate for the analysis and determination of large-volume samples.

Determination of Polyhexamethylene Biguanide Hydrochloride Using a Lactone-Rhodamine B-Based Fluorescence Optode

A new determination method for polyhexamethylene biguanide hydrochloride (PHMB) using a lactone-rhodamine B (L-RB) based fluorescence optode has been developed. The optode membrane consists of 2-nitrophenyl octyl ether as a plasticizer, L-RB, and poly (vinyl chloride). The optode responds to tetrakis (4-fluorophenyl) borate, sodium salt (NaTPBF) in the μM range. The fluorescence intensity of the L-RB film for PHMB solution containing 20 μM NaTPBF decreased linearly as the concentration of the PHMB solution increased in the concentration range from 0 to 8.0 μM, which shows that PHMB with a concentration range of 0 to 8.0 μM is determined by the L-RB film optode. The concentration of PHMB in the contact lens detergents by the proposed method was in accord with its nominal concentration.