Artificial Receptor-Facilitated Solid-Phase Microextraction of Barbiturates

Abstract

A receptor for barbiturates, N,N'-Bis-[6-(2-ethylhexanoylamino)-pyridin-2-yl]-isophthalamide, was designed to dissolve in plasticizers of poly(vinyl chloride) (PVC). Microextractions using receptor-doped films of PVC were carried out as a function of receptor concentration. The effect of the concentration of the receptor on extraction yield is considerable for barbiturates that have significant binding to the receptor but negligible for very similar molecules that do not bind to the receptor strongly. Thus, it is the receptor's ability in molecular recognition, not its generic ability as an H-bonding cosolvent, that is important. On the other hand, NMR data show that the receptor self-associates. A simple, approximate analysis is given to extract the amount of active receptor from the data. Receptor-enhanced extractions of barbiturates from urine are compared to extractions using a phosphate ester as solvent.

Molecular and Ionic Hydrogen Bond Formation in Fluorous Solvents

“…These interactions become less important in competitive solvents; 10 thus, a matrix that is a poor solvent will provide a more selective environment for molecular recognition interactions. 11,12 Poorly solvating, highly nonpolar fluorous liquids are practically immiscible with both aqueous and organic phases 13 and, with the exception of some small gases, nonfluorous solutes are, in general, virtually insoluble in them. Thus, fluorous liquids have become useful for purification and reaction cleanup [13][14][15] by reducing the unintentional extraction of interfering species.…”

Barbituric Acid Sensor Based on Molecularly Imprinted Polymer‐ Modified Hanging Mercury Drop Electrode

“…Therefore, the determination of barbiturates in body fluids, with a narrow therapeutic concentration index and variable rates of elimination, requires a sensitive method development. Several methods have been reported in this direction which include capillary electrophoresis [19], electrochemical techniques [21 -22], fluorescence [23], microextraction [24] and immunoassay [25] techniques. However, some of these are really time consuming and need complicated experimental design.…”

Supramolecular Architectures Incorporating Hydrogen‐Bonding Barbiturate Receptors

“…In the same article, it was observed that Hamilton‐like receptors have a tendency to self‐associate by hydrogen bonding, especially in alkane solvents, often leading to poor solubility. This problem was also encountered by a different team working on dissolving Hamilton’s receptors in poly(vinyl chloride) for building extraction devices for barbiturates 21. Other gelating systems have been reported,22 including magnetic gels incorporating iron oxide nanoparticles (radius=3.5 nm), which show a strong temperature‐dependent release profile 22d.…”