GAS CHROM

Pyrazolines Imidazoles Thiazoles Oxadiazoles 1 -Phenylpyrazoles Purines Dioxolanes Ox azolines 10% Cyanethylated mannite on Celite 545. 5% OV-17 on Chromosorb W, AW-DMCS (H.P.). Carbowax 4000, dioleate on firebrick, 190 °C. Silicone grease on Chromosorb P. Apiezon L on firebrick C-22, 220 °C. 15% Hallcomid M-18 on firebrick. Carbowax 20M on Gas-Chrom P. Ethyleneglycol succinate on Diatoport-S. 

Hewlett-Packard, Model 5710A with Ni electron-capture detector Glass, Pyrex, 2 m x 2-mm-i.d. with 3% QF-1 on 80-100-mesh Gas Chrom Q... 

Ethylenethiourea (ETU) is a toxic decomposition product/metabolite of alky-lenebis(dithiocarbamates). This compound could be generated during processing of treated crops at elevated temperature. Different chromatographic methods to determine the residue levels of ETU have been published. After extraction with methanol, clean-up on a Gas-Chrom S/alumina column and derivatization (alkylation) with bro-mobutane, ETU residues can be determined by GC with a flame photometric detector in the sulfur mode. Alternatively, ETU residues can also be determined by an HPLC method with UV detection at 240 nm or by liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/tandem mass spectrometry (LC/MS/MS) (molecular ion m/z 103). ... 

Shimadzu GC-7A gas chromatograph with flame thermionic detector Pyrex spiral column packed with 3% OV-1 on Gas Chrom Q (80-100 mesh), 1 m X 3-mm i.d. 

GC has seen wide use in food analysis but has not seen a large following in the determination of the nonvolatile alkaloids in foods when compared to HPLC. The 13th edition of the AO AC Methods of Analysis22 lists a GC method for the determination of caffeine in coffee or tea using a thermionic KCI detector with a glass column 6 ft x 4 mm i.d. packed with 10% DC-200 on 80 to 100-mesh Gas Chrom Q. 

The biological samples are analyzed with an LKB 900 GC mass spectrometer containing a 4-foot coiled glass column packed with 1% UC-W98 on Gas Chrom Q. The column is maintained at 240°C and the... 

Tsuj i and Robertson achieved the separation of neomycin B, neomycin C and neamine as the trimethylsilyl ethers on a 6ft. column of 0.75% OV-1 on Gas Chrom Q at a temperature of 290°C. The same conditions have also been shown to separate neobiosamine B, neosamine and deoxystreptamine from neomycin and neamine. Hence the method could be used to study the stability of neomycin or to monitor the biosynthetic production process. Use of the procedure to assess the stability of neomycin in pharmaceutical formulations has been demonstrated by Van Giessen and Tsuji237 with trilaurin as internal standard. However,these authors recommended a 2ft. column packed with 3%... 

OV-1 on Gas Chrom Q as longer columns required a higher temperature to chromatograph neomycin and consequently had a reduced column life. A concentration of 3% OV-1 was preferred, as 2% or less resulted in increased column adsorption of neomycin. After a further study of the procedure Margosis and Tsuji238 recommended a number of improvements to optimise the analysis of neomycin by G.L.C. The improvements to the assay included the modification of the injection port to prevent sample decomposition by contact of injected material with... 

Neomycin has been separated from mixtures of other aminoglycoside antibiotics containing the 2-deoxystreptamine moiety as both the pertrimethylsilyl derivative and the N-trifluoro-acetyl pertrimethylsilyl derivative using a column of 0.75% 0V-1 on Gas Chrom q240. The procedure may be used to estimate the number of sugar moieties bound in the antibiotic as a close relationship exists between the number of rings and the retention time. 

Gas chromatographic analysis of the product from three consecutive preparations showed less than 0.1% impurity. Similar results were obtained on 0.005-ml. samples in an F. and M. 202 Temperature Programed Gas Chromatograph using two columns a 12-foot column of 10% HiVac grease and 5% Marlex-50 on 100-140 mesh Gas Chrom A, at a constant temperature of 275°, with a helium flow rate of 120 ml. per minute and a 20-foot column of 20% GE-SE 30 on 100-140 mesh Gas Chrom A, programed at 3.3° per minute from 250° to 300°, with a helium flow rate of 120 ml. per minute. 

Abbott et al. [163] described a pyrolysis unit for the determination of Picloram and other herbicides in soil. The determination is effected by electron capture-gas chromatography following thermal decarboxylation of the herbicide. Hall et al. [164] reported further on this method. The decarboxylation products are analysed on a column (5mm i.d.) the first 15cm of which is packed with Vycor chips (2-4mm), the next 1.05m with 3% of SE-30 on Chromosorb W (60-80 mesh) and then 0.6m with 10% of DC-200 on Gas Chrom Q (60-80 mesh). The pyrolysis tube, which is packed with Vycor chips, is maintained at 385°C. The column is operated at 165°C with nitrogen as carrier gas (110ml min-1). The method when applied to ethyl ether extracts of soil gives recoveries of 90 5%. Dennis et al. [165] have reported on the accumulation and persistence of Picloram in bottom deposits. 

Figure 7. MS of the metabolite 3-hydroxy molinate (GC Conditions OV 17,10% on Gas Chrom Q (4 ) helium flow rate, 30 mL/min temperature, 150°C retention time, 10.0 min)...

Gas Chromatography Analysis of Water for Pesticides. All analyses for pesticides in water were done by gas chromatography. Solvents used for extraction were checked by gas chromatography for purity and interferences and all glassware used in the extraction was cleaned in a chromic acid/sulfuric acid mixture. Standards consisted of mixtures of various pesticides (actual commercial formulations) suspended or dissolved in water. These aqueous standards were extracted in the same manner as unknown solutions. The standard concentrations encompassed the concentration of unknowns to be determined. A standard curve normally consisted of a set of four pesticide concentrations. Blanks were run and an internal standard (eicosane) was used. The internal standard concentration was kept constant for all analyses. The conditions for GC analysis were guided by the pesticides expected in the water. For the more complex mixtures, such as those employed in the synthetic waste and those encountered in the field, a 6 ft., 3 percent SE-30 on GAS CHROM Q column sufficed. A typical chromatogram of a complex pesticide mixture is shown in Figure 2. ( )... 

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