Gas chromatography internal standards

S, amount of sulfur/ketone (mol/mol) N, amount of amine/ketone (mol/mol) T, reaction temperature (°C).b Determined by gas chromatography (internal standard technique). The reaction was carried out under reflux. 

The experimental yield was determined by gas chromatography (internal standard technique) directly on the reaction mixture. 

Diazotization with p-nitroaniline, paper chromatography, UV absorption spectrophotometry Methylation, paper chromatography, UV absorption spectrophotometry Formation of 2,4-dinitrobenzoates Formation of phenylazobenzene sulfonic acid derivatives Methylation, gas chromatography Gas chromatography, internal standard addition... 

Figure 3.13 Headspace analysis of volatiles of whole milk powder stored in air at 40 C (peroxide value 1.01). 1 = pentanone 2 = pentanal 3 = methyl butyrate (internal standard) 4 = hexanal 5 = heptanone 6 = heptanal 7 = octanal 8 = octanoic 9 = nonanal. Chromatographic conditions were as in Fig. 3.12. Reproduced from Ulberth, F. and Roubicek, D., Monitoring of oxidative deterioration of milk powder by headspace gas chromatography. International Dairy Journal, 5, 523-31, 1995.

ASTM International, Standard test method for analysis of 2,6-diter-tiary-butyl para-cresol and 2,6-ditertiary-butyl phenol in insulating liquids by gas chromatography, ASTM Standard ASTM D4768, ASTM International, West Conshohocken, PA, 2011. 

Finally, other methods are used to obtain simulated distillation by gas phase chromatography for atmospheric or vacuum residues. For these cases, some of the sample components can not elute and an internal standard is added to the sample in order to obtain this quantity with precision. 

Blood and urine are most often analyzed for alcohol by headspace gas chromatography (qv) using an internal standard, eg, 1-propanol. Assays are straightforward and lend themselves to automation (see Automated instrumentation). Urine samples are collected as a voided specimen, ie, subjects must void their bladders, wait about 20 minutes, and then provide the urine sample. Voided urine samples provide the most accurate deterrnination of blood alcohol concentrations. Voided urine alcohol concentrations are divided by a factor of 1.3 to determine the equivalent blood alcohol concentration. The 1.3 value is used because urine has approximately one-third more water in it than blood and, at equiUbrium, there is about one-third more alcohol in the urine as in the blood. 

High performance liquid chromatography is used for the separation and quantitative analysis of a wide variety of mixtures, especially those in which the components are insufficiently volatile and/or thermally stable to be separated by gas chromatography. This is illustrated by the following method which may be used for the quantitative determination of aspirin and caffeine in the common analgesic tablets, using phenacetin as internal standard where APC tablets are available the phenacetin can also be determined by this procedure. 

It should be noted here that the difficulty of accurately injecting small quantities of liquids imposes a significant limitation on quantitative gas chromatography. For this reason, it is essential in quantitative GLC to use a procedure, such as the use of an internal standard, which allows for any variation in size of the sample and the effectiveness with which it is applied to the column (see Sections 9.4(5) and 9.7). 

Ethanol production in the fermentation process was detected with gas chromatography, HP 5890 series II (Hewlett-Packard, Avondale, PA, USA) equipped with a flame ionisation detector (FID) and GC column Porapak QS (Alltech Associates Inc., Deerfield, IL, USA) 100/120 mesh. The oven and detector temperature were 175 and 185 °C, respectively. Nitrogen gas was used as a carrier. Isopropanol was used as an internal standard. 

Ethanol concentration in the fermentation broth is determined by using gas chromatography (HP 5890 series II with HP Chemstation data processing software, Hewlett-Packard, Avondale, PA) with a Poropak Q Column, and a Hewlett-Packard model 3380A integrator. A flame ionisation detector (FID) is used to determine ethanol. The oven temperature is maintained at 180 °C, and the injector and detector temperature are maintained at 240 °C. The sample taken from the fermentation media has to be filtered and any internal standard must be added for analysis based on internal standard methods otherwise, the area under the peak must be compared with known standard samples for calculation based on external standard methods. 

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

Shatkay, A., Effect of Concentration on the Internal Standards Method in Gas-Liquid Chromatography, Ana/. Chem. 50, 1978, 1423-1429. 

Reaction products were analyzed by on-line gas chromatography with a Shimadzu GC-14A gas chromatograph equipped with a 50 m CP Sil-5 fused silica capfllary column and a flame ionization detector. Reaction intermediates were identified by GC-MS. Samples were taken after 50 h on stream when the activity of the catalyst was stable, with n-nonane and n-dodecane as internal standards. Space time was defined as t = e Voat/vgas, where e is the void fraction of the... 

Characterization of various types of damage to DNA by oxygen-derived species can be achieved by the technique of gas chromatography-mass spectrometry (GC-MS), which may be applied to DNA itself or to DNA-protein complexes such as chromatin (Dizdaroglu, 1991). For GC-MS, the DNA or chromatin is hydrolysed (usually by heating with formic acid) and the products are converted to volatile derivatives, which are separated by gas chromatography and conclusively identified by the structural evidence provided by a mass spectrometer. Stable isotope-labelled bases may be used as internal standards... 

Virtually all current research in SFC utilizes either small bore packed columns with particles of 5-10 micrometers in diameter optimized for use in liquid chromatography or narrow bore, fused silica open tubular columns with Immobilized phases similar to those used in gas chromatography. In the latter case columns of saaller internal diameter, 10-100 micrometers, shorter lengths (generally less than 20 m with 1-10 m being the most common length), and more firmly crosslinked stationary phases are used by coaparison with standard columns for gas chromatography. In all... 

The urine samples were analyzed using a modified version of a published method.8 The method involved fortification of the urine samples with an internal standard 3,4,5-trichloro-2-pyridinyl, which is a structural isomer of the 3,5,6-TCP metabolite of chlorpyrifos hydrolysis of labile acid conjugates to 3,5,6-TCP solvent extraction derivitization to the f-butyl-dimethylsilyl ester of 3,5,6-TCP and subsequent negative-ion chemical ionization gas chromatography/mass spectrometry (GC/MS) analysis. Creatinine was determined in urine using a modification of a method of Fabiny and Erting-shausen.9... 

Part 22 Determination of ethylene oxide and propylene oxide in plastics Headspace gas chromatography with diethyl ether as internal standard... 

The production of 13CC>2 from [13C]-deca-BDE degradation was analyzed using the technique of gas chromatography coupled to mass spectrometer for isotope ratio (GC-EMRI). This technique measures the isotopic ratio 13C/12C of CO2 in the gas phase with respect to an international standard V-PDB (Vienna Pee Dee Belem-nite). This isotopic ratio is reported in 8 notation relative to an international standard per mil (%o) ... 

Szathmary and Luhmann [50] described a sensitive and automated gas chromatographic method for the determination of miconazole in plasma samples. Plasma was mixed with internal standard l-[2,4-dichloro-2-(2,3,4-trichlorobenzyloxy) phenethyl]imidazole and 0.1 M sodium hydroxide and extracted with heptane-isoamyl alcohol (197 3) and the drug was back-extracted with 0.05 M sulfuric acid. The aqueous phase was adjusted to pH 10 and extracted with an identical organic phase, which was evaporated to dryness. The residue was dissolved in isopropanol and subjected to gas chromatography on a column (12 m x 0.2 mm) of OV-1 (0.1 pm) at 265 °C, with nitrogen phosphorous detection. Recovery of miconazole was 85% and the calibration graph was rectilinear for 0.25 250 ng/mL. 

Niclosamide, formulated as the ethanolamine salt, was determined in formulations and the impact of residues on the environment assessed [82], Efficient (>85%) phase-transfer, N, Odimethylation of niclosamide and the synthesized 5-deschloro analog internal standard, followed by gas-liquid chromatography separation and electron-capture detection, permitted the determination of as little as 10 ppb analyte in fortified, stagnant water. 

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