Gas chromatography, use

Interest in this method has decreased since advances made in gas chromatography using high-resolution capillary columns (see article 3.3.3.) now enable complete identification by individual chemical component with equipment less expensive than mass spectrometry. 

Cyclobutanone [1191-95-3] M 70.1, b 96-97 , d 0.931, n 1.4189. Treated with dilute aqueous KMn04, dried with molecular sieves and fractionally distd. Purified via the semicarbazone, then regenerated, dried with CaS04, and distd in a spinning-band column. Alternatively, purified by preparative gas chromatography using a Carbowax 20-M column at 80°. (This treatment removes acetone). 

Hept-l-ene [592-76-7] M 98.2, b 93 /771mm, d 0.698, n 1.400. Distd from sodium, then carefully fractionally distd using an 18-in gauze-packed column. Can be purified by azeotropic distn with EtOH. Contained the 2- and 3-isomers as impurities. These can be removed by gas chromatography using a Carbowax column at 70°. 

Lab method using charcoal diffusive samplers, solvent desorption and gas chromatography (using Drager ORSA monitor) 64... 

The quantitative determination of a component in gas chromatography using differential-type detectors of the type previously described is based upon meas urement of the recorded peak area or peak height the latter is more suitable in the case of small peaks, or peaks with narrow band width. In order that these quantities may be related to the amount of solute in the sample two conditions must prevail ... 

A portion of the product was heated to reflux with methanolic sodium methoxide to convert it into the thermodynamic mixture of trans- (ca. 65%) and cis- (ca. 35%) isomers. Small amounts of the isomers were collected by preparative gas chromatography using an 8 mm. by 1.7 m. column containing 15% Carbowax 20M on Chromosorb W, and each isomer exhibited the expected spectral and analytical properties. The same thermodynamic mixture of isomers was prepared independently by lithium-ammonia reduction5 of 2-allyl-3-methyl-cyclohex-2-enone [2-Cyclohexen-l-one, 3-methyl-2-(2-propcnyl)-],6 followed by equilibration with methanolic sodium methoxide. 

Acetone and Ethanol (Grade AA only). Determine the acetone and ethanol content by the elution method of gas chromatography using internal standards... 

Stan H-J, Mrowetz D. 1983. Residue analysis of organophosphorus pesticides in food with 2-dimensional gas chromatography using capillary columns and flame photometric detection. J High Resol Chromatog Chromatog Comm 6 255-263. 

Decomposition products were captured in two traps immersed in dry ice followed by a third trap containing 5 ml of benzene. After 1 hour, the boat, tube, and traps were rinsed with benzene. The benzene solution was analyzed by gas chromatography using an electron capture detector to determine the concentration of unreacted 2,3,7,8-tetrachloro-dibenzo-p-dioxin. 

The cracking of diphenylmethane (DPM) was carried out in a continuous-flow tubular reactor. The liquid feed contained 29.5 wt.% of DPM (Fluka, >99%), 70% of n-dodecane (Aldrich, >99% solvent) and 0.5% of benzothiophene (Aldrich, 95% source of H2S, to keep the catalyst sulfided during the reaction). The temperature was 673 K and the total pressure 50 bar. The liquid feed flow rate was 16.5 ml.h and the H2 flow rate 24 l.h (STP). The catalytic bed consisted of 1.0 g of catalyst diluted with enough carborundum (Prolabo, 0.34 mm) to reach a final volume of 4 cm. The effluent of the reactor was condensed at high pressure. Liquid samples were taken at regular intervals and analyzed by gas chromatography, using an Intersmat IGC 120 FL, equipped with a flame ionization detector and a capillary column (Alltech CP-Sil-SCB). 

After the desired reaction time, the stirring was stopped and the reactor cooled to ambient temperature. The reactor was slowly vented into the hood. The organic phase was typically clear and colorless and the aqueous phase yellow to red. The products were analyzed by gas chromatography using an SRI Instmments gas chromatograph with a flame ionization detector. 

Hydrolytic Kinetic Resolution (HKR) of epichlorohydrin. The HKR reaction was performed by the standard procedure as reported by us earlier (17, 22). After the completion of the HKR reaction, all of the reaction products were removed by evacuation (epoxide was removed at room temperature ( 300 K) and diol was removed at a temperature of 323-329 K). The recovered catalyst was then recycled up to three times in the HKR reaction. For flow experiments, a mixture of racemic epichlorohydrin (600 mmol), water (0.7 eq., 7.56 ml) and chlorobenzene (7.2 ml) in isopropyl alcohol (600 mmol) as the co-solvent was pumped across a 12 cm long stainless steel fixed bed reactor containing SBA-15 Co-OAc salen catalyst (B) bed ( 297 mg) via syringe pump at a flow rate of 35 p,l/min. Approximately 10 cm of the reactor inlet was filled with glass beads and a 2 pm stainless steel frit was installed at the outlet of the reactor. Reaction products were analyzed by gas chromatography using ChiralDex GTA capillary column and an FID detector. 

Analysis of reaction products - Liquid reaction products were analyzed by gas chromatography using a capillary column (type WCOT Fused Silica, stationary phase 5% phenyl-methyl-polysiloxane length - 50 m ID - 0.32 mm, OD - 0.45 mm film thickness - 0.25 pm). 

Carbon dioxide chemisorptions were carried out on a pulse-flow microreactor system with on-line gas chromatography using a thermal conductivity detector. The catalyst (0.4 g) was heated in flowing helium (40 cm3min ) to 723 K at 10 Kmin"1. The samples were held at this temperature for 2 hours before being cooled to room temperature and maintained in a helium flow. Pulses of gas (—1.53 x 10"5 moles) were introduced to the carrier gas from the sample loop. After passage through the catalyst bed the total contents of the pulse were analysed by GC and mass spectroscopy (ESS MS). 

Concentrations of educts and products were measured by gas chromatography using a Varian 2740 FID instrument (OV 101, Porapak columns). 

Leek and Bagander [221] determined reduced sulfide compounds (hydrogen sulfide, methyl mercaptan, carbon disulfide, dimethyl sulfide, and dimeth-yldisulfide) in water by gas chromatography using flame detection. Detection limits ranged from 0.2 ng/1 for carbon disulfide to 0.6 ng/1 for methyl mercaptan. Hydrogen sulfide was determined at the 1 ng/1 level. 

Mugo and Orlans [197] have discussed shipboard methods for the determination of chromium (III) and total chromium in seawater by derivatisation with trifluoroacetylacetone followed by gas chromatography using an electron capture detector. 

Leek and Baagander [311] determined reduced sulfide compounds in seawater by gas chromatography using a flame ionisation detector. Substances determined include methyl mercaptan, dimethyl sulfide, hydrogen sulfide and carbon disulfide. Detection limits range from 0.2ng/l (carbon disulfide) to 0.6 ng/1 (methyl mercapton). 

Work on the determination of chlorinated insecticides has been almost exclusively in the area of gas chromatography using different types of detection systems, although a limited amount of work has been carried out using liquid chromatography and thin-layer chromatography. 

The insecticide fenitrothion (0,0-dimethyl-0-4-nitro-3-methylphenyl thio-phosphate) can be measured in sea water and sediments by gas chromatography, using a flame photometric detector to determine P and S [387]. The degradation products of the organophosphorus insecticides can be concentrated from large water by collection on Amberlite XAD-4 resin for subsequent analysis [383]. 

The techniques used for the investigation of organotin compounds in seawater are atomic absorption spectrometry, gas chromatography, or gas chromatography using AAS as detector. 

Pseudoephedrine in urine was analyzed by gas chromatography using a 2% polyethylene glycol 600 + 5% KOH,... 

---