Chromatography sweep

Gas separation performances (H2/n-butane, n-hexane/2-2 dimethylbutane) have been measured using a sweep gas (countercurrent mode) in order to increase the permeation driving force (no differential pressure was used) permeate and retentate compositions (see Figure 2) were analysed using on line gas chromatography. 

Isoo, K., Otsuka, K., and Terabe, S. (2001). Application of sweeping to micellar electrokinetic chromatography-atmospheric pressure chemical ionization-mass spectrometric analysis of environmental pollutants. Electrophoresis 22, 3426-3432. 

Tissue pulverization and extraction with acetone. Concentration and purification by sweep co-distillation and Florisil/anhydrous sodium sulfate column chromatography. Elution with 20% ether in hexane followed by hexane. Addition of internal standard. 

Kale, endive, carrots, lettuce, apples, potatoes, strawberries Extraction of crops with ethyl acetate and granular sodium sulfate, filtration, concentration with K-D. Sweep codistillation cleanup for GC. Florisil partition chromatography for polarographic confirmation. GC/KCI thermionic detector or GC/FPD polarographic confirmatory method No data for GC polarographic 0.2 ppm based on 1 g crop in 1 mL cell No data AOAC 1990... 

Kirkbride (1987) described the estimation of diazinon in human omental tissue (fatty tissue) after a fatal poisoning. In this method, the tissue was pulverized and extracted with acetone. After extract concentration and purification by sweep co-distillation and Florisil fractionation, diazinon was measured by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). After another fatal diazinon poisoning, diazinon was quantified by GC/electron capture detection (ECD) and GC/flame ionization detection (FID) by Poklis et al. (1980). The diazinon in human adipose, bile, blood, brain, stomach contents, kidney, and liver was recovered by macerating the sample with acetonitrile followed by the addition of aqueous sodium sulfate and extraction into hexane. Following an adsorption chromatography clean-up, the sample was analyzed. 

Animal fat was studied using sweep codistillation (Brown et al. 1987). Good recovery (90%) was measured at 0.4 mg/kg no LOD information was given. Diazinon in liver and rumen content was determined by GC/FPD after methanol/dichloromethane (1 9) extraction and clean-up using either gel permeation chromatography (GPC) or silica gel solid phase extraction (SPE). The LODs were reported to range from 10 to 50 pg/g using a 5 g sample with measured recoveries of diazinon from rumen content of 95% at 0.1 pg/g and from liver of 88% at 0.05 pg/g. 

Three standardized methods were found in the Official Methods ofAnalysis of the Association of Official Analytical Chemists (AOAC 1990). The first of these methods is based on the extraction of crops (kale, endive, carrots, lettuce, apples, potatoes, and strawberries) with ethyl acetate and isolation of the residue followed by a sweep codistillation cleanup prior to GC/thermionic detection (Method 968.24). The second of these methods utilizes Florisil column chromatography clean-up followed by GC/FPD (Method 970.53). In the third method (Method 970.52), the sample is extracted with acetonitrile, and the residue is partitioned into petroleum ether followed by Florisil clean-up and GC/KC1 thermionic detection. Identifications are based on combinations of gas, thin-layer, and paper chromatography. The recovery for diazinon in this method is stated to be greater than 80% no data on limits of detection were given. 

Sweeping was introduced by J. R Quirino and S. Terabe, Exceeding 5000-Fold Concentraton of Dilute Analytes in Micellar Electrokinetic Chromatography, Science 1998, 282, 465. 

P. Bocek, Sweeping of Neutral Analytes in Electrokinetic Chromatography with High-Salt-Containing Matrixes, Anal. Chem. 2000, 72, 1934. 

L. Zhu, C. Tu, and H. K. Lee, On-Line Concentration of Acidic Compounds by Anion-Selective Exhaustive Injection-Sweeping-Micellar Electrokinetic Chromatography, Anal. Chem. 2002, 74, 5820. 

ENTHALPY AND ENTROPY OF VAPORIZATION. The first accurate thermodynamic quantities obtained using GC were enthalpies of vaporization. In 1960 Mackle, Mayrick, and Rooney, (12) measured the heats of vaporization of 2-thiobutane, 3-thiobutane, and 4-thio-heptane by using gas-liquid chromatography coupled with a bypass sampling system. In this system the sample is placed in a sample tube, connected to the apparatus, and cooled with dry ice. Then the sample is warmed to the specified temperature and equilibrated in one arm of the apparatus. The liquid is then isolated from the system and carrier gas allowed to pass through the arm, sweeping the vapors onto the gas chromatographic column. 

Liu, Y. and L. Jia. 2008. Analysis of estrogens in water by magnetic octadecylsilane particles extraction and sweeping micellar electrokinetic chromatography. Microchem. J. 89 72-76. 

The only practical method for the measurement of specific hydrocarbons is by gas chromatography (GC), which can be automated, but is expensive and often used as a laboratory analyzer. Certain specially prepared columns can be used to adsorb specific hydrocarbon classes. For atmospheric hydrocarbons, a common method is to pass a sample of air through a small freeze-out trap, sweep out the air with helium, and then warm the trap and introduce the condensables into the GC column in one concentrated slug. 

In elution systems like chromatography, nc can be significantly larger than the value indicated in Eq. 5.61 because each successive volume sweeping the column can bring forth and resolve a new group of peaks. Analysis shows that the peak capacity (for adjacent peaks at Rs = 1) is approximately [19]... 

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