Partition Coefficients of Environmentally Important Phenols in a Supercritical Carbon Dioxide−Water System from Cocurrent Extraction without Analysis of the Compressible Phase

Abstract

Partition coefficients of phenol, salicylic acid, and several environmentally important chloro- and nitrophenols in a supercritical CO2-water system were measured using direct cocurrent extraction of aqueous solutions of the individual solutes with CO2. Partitioning data on the nitrophenols and salicylic acid were obtained for the first time. To bypass the troublesome and error-prone analysis of the CO2-rich phase, the present method employed only the solute concentrations in the aqueous phase before and after extraction to determine the partition coefficient. Unlike most previous engineering studies of phenol partitioning in a CO2-water system, the concentrations of phenolic solutes approached infinite dilution in both phases. This makes the results relevant to analytical-scale SFE of environmental water samples with CO2. Because of effective infinite dilution of the solutes, the partition coefficients provide a direct measure of relative CO2-philicity/hydrophilicity of the individual phenols. Compared to the octanol-water partition coefficients of substituted phenols, the CO2-water partition coefficients are more sensitive to substitution in the position neighboring the hydroxyl group.

Supercritical Fluid Extraction - New progressive method in brewing analytics. Part I. - Theoretical principles of supercritical fluid extraction and examples of its use.

“…from water, they found a negative impact on the yield of the extracted compounds, caused by the dissolved CO 2 , and thus by the significant decrease of pH of the extracted solution (down to pH = 3,5) [18,19]. Karasek et al [20] addressed a similar issue.…”

“…z vody, přičemž zjistili negativní vliv na výtěžnost extrahovaných látek, způsobený rozpouštěním CO 2 , a tím významným poklesem pH extrahovaného roztoku (až na pH = 3,5) [18,19]. Obdobnému tématu se věnovali i Karásek et al [20].…”

Approaches for on-line coupling of extraction and chromatography

“…The solvating properties of the fluid are also decreased substantially during the depressurisation. Many SFE-GC applications have been published [128,129,130,131,132,133,134,135,136,137,138,139,140,141], and a few SFE-SFC [143,144,145,146] and numerous SFE-LC [147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173] applications have been reported. SFE-SFC applications are not covered in this review.…”

“…The most common interface in SFE-LC coupling is solidphase trapping, although a few other types of interfaces have been developed as well [143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173]. These include the impactor interface, open-tubular trapping, and the sample loop interface.…”

“…It is also possible to use SFE in combination with chromatography for the analysis of aqueous samples. An example of such an application is the determination of pyrethrins in aqueous solutions using SFC-LC [172,173] (Fig. 8).…”