Hexane gas chromatography

MEASUREMENT METHODS Impinger hexane gas chromatography with electron capture detection. 

Fig. 3. (a) Flame ionization detector (fid) response to an extract of commercially processed Valencia orange juice, (b) Gas chromatography—olfactometry (geo) chromatogram of the same extract. The abscissa in both chromatograms is a normal paraffin retention index scale ranging between hexane and octadecane (Kovats index). Dilution value in the geo is the -fold that the extract had to be diluted until odor was no longer detectable at each index. 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

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. 

The products of the oxidation reaction were analysed by gas chromatography (Hewlett Packard, 5880 A), employing a FID detector and equipped with a capillary column (50 m x 0.25 mm crosslinked methyl silicone gum). The reactants and products of n-hexane oxidation were analysed by gas chromatography (Hewlett Packard, 5890) equipped with a FFAP column (30 m X 0.25 mm). The identity of the products was further confined by GC-MS (Shimadzu QCMC-QP 2000A). 

Residues of flumioxazin are extracted from plant matrices with aqueous acetone. The extracted residues are partitioned into dichloromethane. The dichloromethane is removed through rotary evaporation. Partitioning between hexane-acetonitrile followed by Florisil column chromatography purifles the plant extract. Residues of flumioxazin are quantitated by gas chromatography GC. 

Diazomethane In a distillation flask equipped with an distillation funnel and a cooler, place a solution of 5 g of potassium hydroxide in 8mL of water and 25 mL of ethanol. Warm the distillation flask to 65 °C in a water-bath. Add a solution of 21.5g (0.1 mol) of A-methyl-lV-nitroso-p-toluenesulfamide in 130 mL of diethyl ether through the instillation funnel in 5 min. If the distillation funnel becomes empty, pour 20 mL of diethyl ether into the funnel, and distill it gradually. Continue distillation until the distilled ether solution becomes colorless. About 3 g of diazomethane is contained in the whole resultant ether distillate. Caution these procedures should be conducted in a laboratory hood Orbencarb, methyl 2-chlorobenzylsulfone (I), 2-chlorobenzoic acid (II), methyl 2-chlorobenzoate analytical standard materials (Ihara Chemical Industries Co., Ltd) Orbencarb and I standard solution for gas chromatography 1.0 qgmL in acetone Methyl 2-chlorobenzoate standard solution for gas chromatography 0.1 qgmL" in n-hexane... 

The eluate from the Cig cartridge is concentrated by rotary evaporation and the residue is dissolved in n-hexane and then subjected to a cleanup procedure using a Florisil cartridge. The eluate is dried and analyzed by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). 

Transfer the concentrate into a 200-mL separatory funnel using two portions of 20 mL of n-hexane. Add 100 mL of saturated sodium chloride aqueous solution and extract twice with 100 mL of n-hexane by shaking for 5 min and allow the phases to separate. After dehydration of the n-hexane extract with 10 g of anhydrous sodium sulfate, concentrate the extract to dryness below 40 °C with a rotary evaporator. Transfer the residue with three portions of 5 mL of n-hexane into a glass column containing 10 g of Florisil (deactivated by water at a rate of 1%). Elute with 100 mL of n-hexane-ethyl acetate (9 1, v/v) and then with 100 mL of n-hexane-ethyl acetate (7 3, v/v). Concentrate the second eluate to dryness and dissolve the residue in 10 mL of n-hexane and analysis by gas chromatography/flame thermionic detection (GC/FTD). 

Residues are extracted with acetone. The extract is rotary evaporated to remove acetone, the concentrated residue is diluted with 5% aqueous sodium chloride, and residues are partitioned into dichloromethane. The extract is then concentrated and purified on a silica gel column. Residues of pyriproxyfen are quantitated by gas chromatography with nitrogen-phosphorus detection (GC/NPD). For citrus, a hexane-acetonitrile solvent partition step is required for oil removal prior to the dichloromethane partition step. 

Catalytic tests were performed in a gas-phase continuous-flow reactor. The outlet flow of the reactor was either sampled for the analysis of the gaseous components, or condensed in a dry frozen trap, for the analysis of the solid and liquid products. Two liquid layers formed an organic layer containing the unconverted n-hexane, and an aqueous layer, some products dissolved preferentially in the organic layer, others in the aqueous one. Both layers were analyzed by gas chromatography. 

Meyer and others (1997) and Frankel and Meyer (2000) used an induction method in which Cu(II) is applied to initiate oxidation of LDL. The oxidation progress is subsequently monitored through determination by gas chromatography of the amounts of hexanal in the headspace of the reaction vessels. 

Isotope dilution gas chromatography-mass spectrometry has also been used for the determination of ppb of total chromium in seawater [181-183]. The samples were reduced to ensure Cr111 and then extracted and concentrated as tris (l,l,l-trifluoro-2,4-pentanediono) chromium (III) [(Cr(tfa)3>] into hexane. The Cr(tfa)2 mass fragments were monitored into a selected ion monitoring (SIM) mode. 

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