HPLC-fluorescence determination of equilin and equilenin in postmenopausal women's urine

Affinity-Recognition-Based Gravimetric Nanosensor for Equilin Detection

The estrogenic hormones that are widely used in postmenopausal hormone supplements for women contaminate natural water resources. Equilin (Equ) is one of the estrogenic hormones that have a maximum contaminant level of 0.35 µg/L in the chemical pollutants list. In this study, estrogenic hormones were precisely detected in a short time by affinity-recognition-based interactions in Quartz Crystal Microbalance (QCM) sensors. The QCM sensors were modified with 11-mercaptoundecanoic acid forming a self-assembled monolayer and with amino acids, namely tyrosine, tryptophan and phenylalanine. The affinity interactions between Equ and amino acids were studied using docking tools and confirmed by QCM experiments. The LODs of Equ were obtained as 4.59, 5.05 and 6.30 ng/L for tyrosine-, tryptophan- and phenylalanine-modified QCM nanosensors, respectively, with linear dynamic detection in the range of 25–500 nM. In terms of the LOD, selectivity and sensitivity calculations, the tyrosine-modified QCM nanosensor was found to have the highest performance for Equ detection compared to the tryptophan- and phenylalanine-modified ones.

Determination of isoliquiritigenin and its distribution in mice by synchronous fluorescence spectrometry

The aim of the present work was to develop a new method using synchronous fluorescence spectrometry (SFS) to determine the concentration of isoliquiritigenin (ISL) in mouse blood and tissues, and to investigate ISL's distribution among organs after an intraperitoneal (IP) dose of ISL. The synchronous fluorescence method was optimized with the sample pH, stability, metal ions, concentration of Al(3+), and surfactants. The proposed method was used to determine the ISL concentration in mouse blood, brain, heart, kidney, liver, spleen and lung after an IP injection of ISL. The optimal conditions for the determination of ISL using SFS were found to be: excitation and emission wavelengths of 469 and 557 nm, respectively; the use of 3% AlCl(3) as a fluorescence intensity enhancer; measuring samples within 1 h of collection, sample pH 7-8, isolation of samples from surfactants; and wavelength interval (Δλ) = 70 nm. After IP injection, the distribution of ISL in mouse organs was: liver > kidney > spleen > blood > lung > brain > heart. The blood concentration of ISL peaked at 60 min; concentrations of ISL in liver, kidney and spleen achieved maxima at 120 min. SFS provides a simple, but effective analytical method that will benefit the study of in vivo biological effects of ISL, including absorption, distribution, metabolism, and excretion.

Gas chromatography and high-performance liquid chromatography of natural steroids

This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.