Usefulness of the Stopped-Flow Mixing Technique for Micelle-Stabilized Room-Temperature Liquid Phosphorimetry

Abstract

The stopped-flow mixing technique was applied for the first time to micelle-stabilized room-temperature phosphorimetry by measuring the fast appearance of the phosphorescent signal yielded by carbaryl in the presence of sodium dodecyl sulfate and thalious ion. The slope and amplitude of the kinetic curves obtained are directly proportional to the analyte concentration, which allows one to develop very simple, fast, automatic methods for the phosphorimetric determination of dissolved carbaryl without the need for solid substrates. Kinetic and equilibrium data can be obtained within only 2-3 s with a greater precision than that provided by solid-surface room-temperature phosphorimetry. The calibration graphs obtained for the proposed kinetic and equilibrium stopped-flow method were linear over the range 0.030-2.0 and 0.050-3.0 Mg mL"1 carbaryl, respectively, and the detection limits achieved were 0.010 and 0.014 Mg mL*1, respectively, i.e., lower than those provided by solid substrates.Kinetic methodology is widely used in phosphorimetry to determine the lifetime of the excited triplet state, a characteristic property of molecules and their environment. The phosphorescence lifetime is a major parameter since compounds having very similar spectral features may have greatly different triplet lifetimes. However, kinetic methodology has not been used for analytical purposes by measuring the rate of formation of a phosphorescent system. Similar to other analytical techniques, this can be accomplished by obtaining a kinetic curve reflecting the variation of phosphorescence with time and using its slope as an analytical parameter. Such

Fast Kinetic Determination of 1-Naphthylacetic Acid in Commercial Formulations, Soils, and Fruit Samples Using Stopped-Flow Phosphorimetry

“…Factors Affecting Phosphorescence. The development of a phosphorescence signal of a dissolved substance requires the following: protective screening effect of micelles for avoiding collisional quenching; the removal of dissolved oxygen from the solution, which is an extremely highly effective phosphorescence quencher and thus has severely restricted the utilization of phosphorescence in analytical chemistry; and the presence of heavy atoms to increase the phosphorescence yield by effectively promoting the S 1 f T 1 intersystem crossing via spin-orbit coupling (22). In this work, we used sodium sulfite to remove oxygen from solutions, SDS as micellar agent, and thallium(I) nitrate as heavy atom.…”

“…Although the use of solid supports in RTP has the limitation of the presence of background signals (which limits its application to trace analysis) and the critical sample preparation and measurement requirements (which strongly affects the result obtained), application of the stopped-flow mixing technique for fast acquisition of analytical data in micelle-stabilized (MS) RTP is as a powerful tool for avoiding those drawbacks (22). This methodology, applied to the determination of 1-naphthylacetic acid in this paper, provides great results when fast reactions are involved in the measurement process as it mixes together the sample and reagent solutions.…”

“…This can be used to develop both a kinetic determination method by measuring the slope of the kinetic curve and equilibrium methods by measuring the amplitude of the kinetic curve, which is directly proportional to the analyte concentration. Panadero et al (22) reported on the determination of carbaryl for the first time. Later on, the same authors applied the technique to the analytical determination of naproxen (23), and it has since been further developed by several authors (24)(25)(26)(27).…”

Application of partial least squares multivariate calibration for the determination of mixtures of carbaryl and thiabendazole in waters by transmitted solid phase spectrophosphorimetry

“…The methodology employed in room temperature phosphorescence (RTP) is based on the measurement of the phosphorescence intensity in a solid phase, [1][2][3][4][5] or in solution if the analyte forms an inclusion complex (cyclodextrins), 6,7 or micellar-stabilised media with non-polar molecules containing a polar group. [8][9][10] Obviously, the use of paper as a solid support diminishes the cost of the analysis, but it has the disadvantage of showing a background signal produced by the substrate, which can limit its application in the detection of trace analytes. There are several ways to diminish the background signal of the paper used as a solid support, the best known being chemical pre-treatment, irradiation with ultraviolet light or extraction with water in a Soxhlet apparatus.…”

Determination of nafronyl in pharmaceutical preparations by means of stopped-flow micellar-stabilized room temperature phosphorescence

“…To date, only two analytical applications of the stopped-flow mixing technique in combination with RTP have been reported. Panadero et al 23 reported for the first time on the determination of carbaryl. Later on, the same authors applied the technique to the analytical determination of naproxen.…”