Detection of digoxin in urine samples by surface-assisted laser desorption/ionization mass spectrometry with dispersive liquid-liquid microextraction.

A novel method for the detection of digoxin using dispersive liquid-liquid microextraction (DLLME) coupled to the surface-assisted laser desorption/ionization mass spectrometric detection (SALDI/MS) was developed. Acetone and chloroform were used as the disperser solvent and extraction solvents, respectively. After the extraction, digoxin was detected using SALDI/MS with colloidal palladium as the matrix. Under optimal extraction and detection conditions, the calibration curve, which ranged from 0.01 to 0.50 µM, was observed to be linear. The limit of detection (LOD) at a signal-to-noise ratio of 3 was 2 nM for digoxin. With a sample-to-extract volume ratio of 400, the enrichment factor for digoxin was calculated to be 252. This novel method was successfully applied for the determination of digoxin in human urine samples.

Excitation-dependent visible fluorescence in decameric nanoparticles with monoacylglycerol cluster chromophores.

Organic fluorescent nanoparticles, excitation-dependent photoluminescence, hydrogen-bonded clusters and lysobisphosphatidic acid are four interesting individual topics in materials and biological sciences. They have attracted much attention not only because of their unique properties and important applications, but also because the nature of their intriguing phenomena remained unclear. Here we report a new type of organic fluorescent nanoparticles with intense blue and excitation-dependent visible fluorescence in the range of 410-620 nm. The nanoparticles are composed of ten bis(monoacylglycerol)bisphenol-A molecules and the self-assembly occurs only in elevated concentrations of 2-monoacylglycerol via radical-catalysed 3,2-acyl migration from 3-monoacylglycerol in neat conditions. The excitation-dependent fluorescence behaviour is caused by chromophores composed of hydrogen-bonded monoacylglycerol clusters, which are linked by an extensive hydrogen-bonding network between the ester carbonyl groups and the protons of the alcohols with collective proton motion and HO···C=O (n→π) interactions.