Fluorous receptor-facilitated solid phase microextraction.

Solid phase microextraction (SPME) is a widely accepted solvent-free extraction technique that usually uses a polymer sorbent as the extraction phase. In this work, we have developed receptor-doped fluorous films for solid phase microextraction. The hydrophobic and lipophobic properties of the fluorous films in principle reduce the polymer-water distribution coefficients of solutes other than those that can form noncovalent interactions with the fluorous receptor. This strategy should improve extraction selectivity. We found that the addition of a fluorous carboxylic acid (Krytox 157 FSH) to a fluorous film (Teflon AF 2400) increased the polymer-water distribution coefficients of quinoline, a nitrogen heterocycle. We studied the effects of receptor concentration and solute concentration on the distribution coefficients based on 96-well vessel SPME. We then coated this receptor doped fluorous polymer on a stainless steel fiber for SPME. Compared to a commonly used SPME fiber made of polydimethylsiloxane (PDMS), it showed a preference for the nitrogen heterocyclic compound over a non-heterocyclic control, phenol. To our knowledge, this is the first reported receptor-doped fluorous SPME.

Lipophilicity screening of novel drug-like compounds and comparison to clog P.

We determined the distribution coefficients of solutes between a polymer film phase (polyvinyl chloride (PVC) with 67% (w/w) dioctyl sebacate (DOS)) and an aqueous phase in a 96-well format. The parallel measurement approach is efficient and uses very little material. Polymer-water distribution coefficients (D(pw)) at different pH values yield the pKa and polymer-water partition coefficient values (P(pw)) of the solutes. log P(pw) of a prominent drug-like compound, 2H-1,2,6-thiadiazine, 3-methyl-5-phenyl-,1,1-dioxide, is in good agreement with clog P, while the pK(a) value is substantially different from calculated values. This method has been also successfully applied to a library of novel drug-like compounds. log D(pw) values (at pH 4.0, 7.0, 10.0) of 24 novel drug-like compounds have been determined with good reproducibility with the 96-well plate approach. Differences between experimental values and a variety of available calculated values are significant. This emphasizes the need for laboratory separations-based measurements of log D.

Fluorous media for extraction and transport.

Selective partitioning can be useful for sample cleanup or the isolation and purification of desired compounds. Fluorocarbon solvents and polymers, and solvents or polymers with similar properties that are not composed solely of carbon and fluorine (so-called 'fluorous' solvents or polymers) have a low ability to dissolve or sorb solutes or penetrants. This lack of solvating ability can lead to selective extractions. Fluorous phases will solvate, and therefore extract or transport, fluorous solutes, or non-fluorous solutes that are stabilized in the fluorous phase by non-covalent interactions with a 'host' or 'receptor' molecule that is in the fluorous phase. In this review, there is a brief discussion of molecular recognition as applied to selective extraction. Fluorous solvents are introduced, and there is a description of some recent applications, chiefly in synthetic organic chemistry. In particular, it is important to understand solute partitioning behavior and methods to predict it when one of the solvents is fluorous. Fluorous polymers Teflon AF1600 and AF2400 have been used in separations. Their rather complex and still not completely understood properties in separations and transport are described. There is a discussion of molecular recognition in fluorous phases as well as a brief discussion of efficient methods of carrying out extractions for analytical or physicochemical purposes.

High-throughput phase-distribution method to determine drug-cyclodextrin binding constants.

A high-throughput method has been developed to measure drug-cyclodextrin binding constants. It measures the distribution ratio of a drug between a polymer film [polyvinyl chloride (PVC) with 67% (w/w) dioctyl sebacate (DOS)] and a cyclodextrin-containing buffer in a 96-well format. Measurements of distribution ratios at several cyclodextrin concentrations lead to binding constants. Binding constants for econazole with six CDs have been determined in one 96-well microplate with four replications of each condition in 10 h. The K(1:1)/10(3) M(-1) values are 3.98 +/- 0.13, 3.90 +/- 0.22, 29.3 +/- 2.2, 0.66 +/- 0.04, 1.78 +/- 0.30, 4.08 +/- 0.50, with (2-hydroxyethyl)-beta-cyclodextrin, (2-hydroxypropyl)-beta-cyclodextrin, 2,6-di-O-methyl-beta-cyclodextrin, heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin, alpha-cyclodextrin, beta-cyclodextrin, respectively. It is likely that 1:2 complexes are also formed in some cases. This method has also been applied to study the binding behavior as a function of the drug concentration and pH. Binding weakens at higher drug concentration which may be due to the self-association of the drug. An acidic environment decreases the binding constant of CD with the basic econazole. The formation of the 1:2 complexes is completely suppressed in acid as well. This protocol is faster than the phase-solubility method. Moreover, the material requirement is up to four orders of magnitude lower.

Hollow PbWO4 nanospindles via a facile sonochemical route.

Novel nanosized lead tungstate (PbWO4) hollow spindles were successfully synthesized, for the first time, via a Pluronic P123- (EO20PO70EO20-) assisted sonochemical process. The triblock copolymer acted as a structure-directing agent and played a key role in the formation of the hollow spindles. An in situ micelle templating mechanism has been proposed for the possible formation mechanism of the hollow nanostructure. The optical properties of the final products were investigated. It is exciting that the as-prepared PbWO4 hollow structure shows extraordinarily high room-temperature photoluminescence intensity compared to the solid structures.

Antimony(III)-doped PbWO4 crystals with enhanced photoluminescence via a shape-controlled sonochemical route.

Sb(III)-doped lead tungstate single crystals with controlled shapes and enhanced green emission have been synthesized via a facile, Pluronic P123 (EO(20)PO(70)EO(20))-assisted, sonochemical method. The surfactant Pluronic P123 was found to play a crucial role in the morphology control of the final products. The growth process was investigated by carefully following time-dependent experiments, and the oriented attachment process accompanying Ostwald ripening was proposed for the possible formation mechanism. The optical properties, such as the Raman spectra and PL spectra, of doped PbWO(4) were studied. Room-temperature photoluminescence of doped PbWO(4) samples with different morphologies at desired Sb doping concentrations showed greatly enhanced luminescence intensity compared to the undoped PbWO(4).

Sonochemical synthesis of PbWO(4) crystals with dendritic, flowery and star-like structures.

Lead tungstate single crystals with dendritic, flowery and star-like structures have been prepared via a facile, ethylene glycol (EG)-assisted sonochemical method. The concentrations of EG and ultrasound irradiation were found to play crucial roles in the morphology control of the final products. The growth process was investigated by carefully following time-dependent experiments, and the oriented attachment process accompanying Ostwald ripening was proposed for the possible formation mechanism. The optical properties, such as the Raman spectra and photoluminescence (PL) spectra, of the obtained PbWO(4) crystals were studied.