Michael T. Combs

Supercritical fluid extraction of metal ions and metal chelates from different environments

Abstract Metal ions and metal chelates have been extracted from both solid and aqueous matrices using both pure and modified supercritical fluid CO 2 . It has been demonstrated that fluorinated chelates have higher solubility in the supercritical fluid which can cause enhanced extraction efficiency. Stability of the neutral metal chelate under supercritical conditions plays an important role in the extraction of metal ions from water. Also, it has been demonstrated that the matrix can have a major effect on extraction of both metal ions and metal chelates. Addition of modifier to both matrix and supercritical fluid can increase extraction efficiency of analytes.

Packed column supercritical fluid chromatography-mass spectroscopy : A review

Abstract The literature is reviewed with regard to packed column supercritical fluid chromatography (SFC) coupled directly with mass spectrometry (MS) using either analytical scale or microbore columns that have typically been used for liquid chromatography analysis. Efforts with direct fluid introduction, moving belt interface, thermospray, particle beam, and atmospheric pressure chemical ionization have been discussed. No longer should SFC be a last resort technique but it should be exercised to its full advantage, especially when coupled to MS. With continual advances in commercially available instrumentation, sample assay by SFC-MS should become routine and rugged.

Solubility of metal chelates and their extraction from an aqueous environment via supercritical CO2

Solubility of nickel(II), copper(II), and chromium(III) hexafluoroacetylacetone and chromium(III) acetylacetone chelates was measured in supercritical CO(2) at two different pressures (200 and 400 atm) and 60 degrees C. Solubility of fluorinated acetylacetone chelates was at least an order of magnitude higher than the non-fluorinated complexes. These pre-formed metal chelates as well metal diethyldithiocarbamate (DDC) and metal bis(trifluoroethyl)dithiocarbamate (FDDC) have also been extracted from aqueous environment using pure supercritical CO(2). It was demonstrated that metal HFA chelates while exhibiting higher solubility in supercritical CO(2) compared with metal FDDC chelates, exhibited lower extraction efficiency using the same extraction conditions. This behavior of metal HFA chelates is related to their stability in an aqueous environment. Direct extraction of Ni(+2) and Cu(+2) from an aqueous matrix was also achieved via in-situ chelation using diethyldithiocarbamate and bis(trifluoroethyl)dithiocarbamate as the ligands. Bis(trifluoroethyl)dithiocarbamate proved to be a more effective ligand for direct extraction of metal ions from aqueous environment using supercritical CO(2).

HPLC/atmospheric pressure chemical ionization-mass spectroscopy of eight regulated sulfonamides.

Reversed phase high performance liquid chromatography coupled with on-line atmospheric pressure chemical ionization mass spectrometry, HPLC,APCI-MS, has been applied to a mixture of eight sulfonamides. In full scan mode, extracted ion chromatograms produced minimum detectable quantities (MDQ) of 0.8 ng on column, for six of the eight regulated sulfonamides investigated. Selected ion monitoring yielded a 50 pg MDQ for sulfamerazine, sulfadiazine and sulfamethazine, while, the other compounds presented higher values. Analysis of supercritical fluid extracts of chicken liver containing sulfadimethoxine were found to be easily detected by HPLC/APCI-MS. In extracts of chicken liver spiked with 25 microg/kg(-1) (25 ppb) of sulfadimethoxine this compound could be detected in selected ion mode, while 100 pg/microl(-1) was detectable in either full scan or single ion modes. The analysis method for extracted sulfadimethoxine also demonstrated good linearity and reproducibility in both single ion and scan mode.

pH effects on the direct supercritical fluid extraction of phenols from aqueous matrices

Abstract pH has been shown to have an effect on the direct supercritical-fluid extraction of phenol and 2,4,6trichlorophenol from aqueous samples. pH affects both extraction efficiencies and extraction kinetics, but the extraction pressure also plays an important role. By altering the pH the amount of neutral analyte as well as the speed at which the analyte is extracted from aqueous samples can be greatly affected. A change in pH appeared to exhibit the largest effect when the extraction pressure was 150 atm for either phenol. By increasing the extraction pressure to 300 atm, the importance of pH on extraction efficiency decreased. The production of carbonic acid when employing carbon dioxide as the extraction fluid for aqueous extraction makes this an advantageous circumstance for the extraction of phenols and other acidic compounds, whereas it may become problematic for basic compounds by increasing the extent of ionization of the basic compounds.

Temperature and pressure effects on the supercritical fluid extraction profiles of sulfonamides from a spiked matrix using CHF3 and CO2

Abstract The effect of temperature and pressure upon the extraction profiles of polar sulfonamides from sand using supercritical CO 2 , methanol-modified CO 2 , CHF 3 , and methanol-modified CHF 3 was investigated. Increasing temperature showed less effect upon extraction rates at 450 atm than at 300 atm using pure CO 2 . No change in extraction rates was observed with increasing temperature using methanol-modified CO 2 , but recovery improved by increasing the pressure at constant temperature. Extraction rates were altered using pure CHF 3 by increasing the temperature at 300 atm causing a distinct change in the extraction profile for sulfamethazine (SMZ) and sulfadimethoxine (SDM). However, at 450 atm increasing temperature served only to decrease recovery and did not greatly affect the extraction profile. Sulfaquinoxaline (SQX) achieved similar total recovery regardless of temperature at constant pressure, although extraction rates varied with temperature. Methanol-modified CHF 3 exhibited no temperature dependence at 300 atm. However, decreased recovery was obtained at 450 atm and 40 °C compared to the higher temperatures.

Separation and Identification of Sulfonamide Drugs via SFC/FT-IR Mobile-Phase Elimination Interface

Packed-column supercritical fluid chromatography with a mobile-phase gradient of carbon dioxide and methanol has been performed on a mixture of eight sulfonamides. The analytes were detected and identified with Fourier transform infrared spectrometry. A commercial mobile-phase elimination interface (LC-Transform®) was employed. A fixed-integral restrictor afforded the decompression zone between the column and germanium disk where the analytes were deposited. Excellent-quality infrared spectra were obtained for all eight separated analytes.