sodium-dodecyl-sulfate and morin

A simple and sensitive electroanalytical method is developed for the determination of lead by adsorptive stripping voltammetry (AdSV) in the presence of morin-5'-sulfonic acid (MSA) and sodium dodecyl sulfate (SDS). The Pb-MSA complex accumulates on the surface of a hanging mercury drop electrode (HMDE) and peak current is measured by square wave voltammetry (SWV). The complex is reduced at -0.48 V and peak current increases when low concentrations of SDS are added to the sample solution. The experimental variables pH, MSA concentration (C(MSA)); accumulation time (t(acc)); accumulation potential (E(acc)), and SDS concentration (C(SDS)), as well as potential interferences, are investigated. Under the optimized conditions (pH 3.2; C(MSA): 0.5 micromol L(-1); t(acc): 60s; E(acc): -0.35 V, and C(SDS): 20 micromol L(-1)), peak current is proportional to the concentration of Pb(II) over the 0.1-32.0 microg L(-1) range, with a detection limit of 0.04 microg L(-1). The relative standard deviation for a solution containing 5.0 microg L(-1) of Pb(II) solution was 1.5% for seven successive assays. The method was validated by determining Pb(II) in synthetic sea water (ASTM D665) spiked with ICP multi-element standard solution and in certified reference water (GBW08607). Finally, the method was successfully applied to the determination of Pb(II) in tap water and sea water after UV digestion.

Topics: Adsorption; Electrochemistry; Flavonoids; Hydrogen-Ion Concentration; Lead; Reproducibility of Results; Seawater; Sodium Dodecyl Sulfate; Sulfonic Acids; Water Supply

Electronic absorption spectra, fluorescence emission spectra, ATR-FTIR spectra, cyclic voltammetric measurements, and ab initio quantum calculation are used to study the properties of morin in SDS micelles of different microstructures and microenvironments and to gain the information about the binding of morin with the SDS micelles. Morin can be located in the SDS micelles with its phenyl group (deviating by 38.98 degrees from the planarity), which leads to the increase of the planarity and the extension of pi conjugation of the whole molecule. The embedment of two hydroxyl groups on the phenyl into a more hydrophobic microenvironment makes the oxidation peak of morin move to a higher potential with a decreased peak current. The binding constant (K) and the distribution coefficient (P) of morin in the spherical SDS micelle are larger than those in the rodlike SDS micelle. The binding of morin with SDS micelle is a spontaneous (DeltaG < 0) and exothermic process (DeltaH < 0), and the hydrophobic force is the main driving force for its solubilization.

Topics: Antioxidants; Flavonoids; Micelles; Models, Molecular; Molecular Structure; Sodium Dodecyl Sulfate; Spectrometry, Fluorescence; Spectrophotometry; Spectroscopy, Fourier Transform Infrared; Thermodynamics