Gas chromatographic method

Gas chromatographic methods are currently the preferred laboratory methods for measurement of total petroleum hydrocarbon measurement because they detect a broad range of hydrocarbons and provide both sensitivity and selectivity. In addition, identification and quantification of individual constituents of the total petroleum hydrocarbon mix is possible. 

Methods based on gravimetric analysis (Table 7.2) are also simple and rapid, but they suffer from the same limitations as those of infrared spectrometric methods (Table 7.2). Gravimetric-based methods may be useful for oily sludge and wastewaters, which will present analytical difficulties for other, more sensitive methods. Immunoassay methods for the measurement of total petroleum hydrocarbon are also popular for field testing because they offer a simple, quick technique for in situ quantification of the total petroleum hydrocarbons. 

Chromatographic columns are commonly used to determine total petroleum hydrocarbon compounds approximately in the order of their boiling points. Compounds are detected by means of a flame ionization detector, which responds to virtually all compounds that can bum. The sum of all responses within a specified range is equated to a hydrocarbon concentration by reference to standards of known concentration. 

SW-846 Method Water/ Wastewater Method Analytes Primary Equipment Sample Preparation  

8015 n/a Aliphatic and aromatic hydrocarbons nonhalogenated VOCs GC/HD Extraction (SVOCs) purge-and-trap and headspace (VOCs) azeotropic distillation (nonhalogenated VOCs) -  

As with phosgene (see Section 3.2.5.1), gas chromatography is a particularly useful technique for the determination of a broad range of concentrations of carbonyl difluoride. The thermal conductivity detector is the only detection system reported to be used for this compound. The detector response for the thermal conductivity detector is shown to be linear over a wide range of COF concentrations [559]. 

By using a column (maintained at room temperature) packed partly with 25 % 13F (a chlorofluoiinated liquid phase) on Floroplast 4 and partly with 10 % 13F on Tolysorb 1, COF, was determined in the presence of CO and air with a sensitivity of 0.05 %, using a thermal conductivity detector and helium carrier gas [10]. 

Group 1 metal fluorides have been employed as column packings for the determination of COF2 (and other fluorocarbonyl compounds) in mixtures with tetrafluoroethene [967]. By using a column composed of CsF supported upon CaFj, the tetrafluoroethene is not chemisorbed and is eluted rapidly. The fluorocarbonyl compounds (CF3)jC=0 (b.pt. -28 C), CF3C(0)F (b.pt. -59 C), and COF (b.pt. -84.6 C), however, are eluted in reverse order of boiling temperatures, so that carbonyl difluoride is eluted last [967]. The chemisorption arises from the reversible chemical process [1692]  

Columns consisting of a high surface area ( 130 m g ) graphite fluoride, (CFj ) , in which 0.5 x 1.14, and in which n is an integer, have been used to separate CO, COj and COFj in the presence of HF [1988]. 

Suitable gas chromatographic conditions for the analysis of carbonyl difluotide in mixtures with phosgene, carbonyl chloride fluoride, COj and air are as follows [84a]  

Conder, Adv. Analyt. Chem. Instrumen., Progress in Gas Chromatography (ed. J. H. 

When a volatile solute is injected on to an involatile solvent spread along a column it is necessary to pass a volume of inert gas Pr (the retention volume) along the column to move this zone of solute from the inlet to the outlet of the column. The retention volume includes a volume Vg due to that part of the column occupied by the gas phase. The net retention volume defined by 

Everett and Stoddart, by taking account of solute + carrier gas interactions, derived an equation relating the retention volume to the excess chemical potential of the volatile component at infinite dilution (/if)  

Here ns is the amount of substance of stationary liquid, pi is the saturated vapour pressure of the solute at temperature r. Bag is the mixture virial coefficient for solute 4- carrier gas interaction, Bcc is the virial coefficient of the carrier gas, Fjj is the partial molar volume of the solute at infinite dilution in the solvent, is the molar volume of pure liquid A, and pi and po are the column inlet and outlet pressures. The chemical potential at infinite dilution can be calculated by measuring the retention volume of an infinitely small sample for various inlet and outlet pressures and extrapolation to zero pressure drop across the column. Everett and Stoddart proposed using equation (33) to determine the mixture second virial coefficients. The precision in Bag from this method is nearly equivalent to the best static methods. The assumptions required to derive the above equation have been examined by a number of authors. -  

Everett considered the effect of the variation of the partition coefficient (the ratio of solute concentration in the liquid phase and the solute concentration in the gas phase) with the pressure drop across the column. Cruickshank, Gainey, and Young have calculated the effects of carrier-gas solubility in the stationary liquid. Conder and Purnell have extended gas chromatography theory to measurements of finite concentrations. Their measurements on w-hexane in squalane and M-heptane in dinonylphthalate, both at 303 K, agree with static measurements in the volatile solute mole fraction range of 0.0 to 0.7 and 0.0 to 0.5 respectively. They conclude that the chemical potential can be measured with an accuracy of approximately 25 J mol over the accessible concentration range. 

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Although each gas chromatographic method has its own unique considerations, the following description of the determination of trihalomethanes in drinking water provides an instructive example of a typical procedure. 

Accuracy The accuracy of a gas chromatographic method varies substantially from sample to sample. For routine samples, accuracies of 1-5% are common. For analytes present at very low concentration levels, for samples with complex matrices, or for samples requiring significant processing before analysis, accuracy may be substantially poorer. In the analysis for trihalomethanes described in Method 12.1, for example, determinate errors as large as +25% are possible. ... 

In current industrial practice gas chromatographic analysis (glc) is used for quahty control. The impurities, mainly a small amount of water (by Kad-Fischer) and some organic trace constituents (by glc), are deterrnined quantitatively, and the balance to 100% is taken as the acetone content. Compliance to specified ranges of individual impurities can also be assured by this analysis. The gas chromatographic method is accurately correlated to any other tests specified for the assay of acetone in the product. Contract specification tests are performed on product to be shipped. Typical wet methods for the deterrnination of acetone are acidimetry (49), titration of the Hberated hydrochloric acid after treating the acetone with hydroxylamine hydrochloride and iodimetry (50), titrating the excess of iodine after treating the acetone with iodine and base (iodoform reaction). 

Acrolein is produced according to the specifications in Table 3. Acetaldehyde and acetone are the principal carbonyl impurities in freshly distilled acrolein. Acrolein dimer accumulates at 0.50% in 30 days at 25°C. Analysis by two gas chromatographic methods with thermal conductivity detectors can determine all significant impurities in acrolein. The analysis with Porapak Q, 175—300 p.m (50—80 mesh), programmed from 60 to 250°C at 10°C/min, does not separate acetone, propionaldehyde, and propylene oxide from acrolein. These separations are made with 20% Tergitol E-35 on 250—350 p.m (45—60 mesh) Chromosorb W, kept at 40°C until acrolein elutes and then programmed rapidly to 190°C to elute the remaining components. 

Chromatographic methods, notably hplc, are available for the simultaneous deterrnination of ascorbic acid as weU as dehydroascorbic acid. Some of these methods result in the separation of ascorbic acid from its isomers, eg, erythorbic acid and oxidation products such as diketogulonic acid. Detection has been by fluorescence, uv absorption, or electrochemical methods (83—85). Polarographic methods have been used because of their accuracy and their ease of operation. Ion exclusion (86) and ion suppression (87) chromatography methods have recently been reported. Other methods for ascorbic acid deterrnination include enzymatic, spectroscopic, paper, thin layer, and gas chromatographic methods. ExceUent reviews of these methods have been pubHshed (73,88,89). 

The levels of trace impurities in the product benzaldehyde are often more important than the product assay. Gas chromatographic methods for the deterrnination of those trace impurities are widely used. 

The columns labeled PI reflect the total of pyrethrin I and cinerin I just as in the AO AC procedure. The gas chromatographic results are in terms of the total amount of the mixture but were analyzed as the methyl ester of chrysanthemic acid. The present state of the determination of PII (pyrethrin II plus cinerin II) is not complete because of the erratic extractability of the dicarboxylic acids from the hydrolysis mixture. The gas chromatographic pattern is distinct and straightforward. As the extraction procedure for PII is improved, the gas chromatographic method will be more applicable. The present recovery of PII is in the range of 80 to 90%. The average of the values shown in Table II for PI is 98.0%. 

Trace Solvent Removal. Several papers were written by Nadeau (4) and by Gilbert (5) and co-workers on gas chromatographic methods for determining solvent traces remaining in flexible packaging films after printing or adhesive lamination. With proper equipment and techniques,... 

One of the most frequent techniques for analyzing 1,4-dioxane is gas chromatography. Birkel et al. [319] proposed in 1979 a gas chromatographic method based on partial vacuum distillation of the sample, analyzing polysorbate 60 and 80 with sensitivity to the 0.5 ppm. Stafford et al. [320] proposed a direct injection GC method which meant an improvement to the Birkel s technique. Robinson and Ciurczak [321] described a direct GC method for the analysis of... 

A gas chromatographic method is described in this work for the analysis of tetradecane-l,4-sultone (C14 5-sultone) and the combination of 2-chloro-tetradecane-l,3-sultone (C14 2-chloro-y-sultone) and l-tetradecene-l,3-sultone (C14 unsaturated y-sultone) in neutral oils isolated from alkenesulfonate. Samples of the neutral oil are diluted in hexane and injected directly into the gas chromatograph. Quantitative data are obtained by comparison to known amounts of the respective sultones. Through the use of silica gel column chromatography followed by GC of collected fractions, separation and individual quantitation of the 2-chlorotetradecane-l,3-sultone and l-tetradecene-l,3-sultone can be obtained. 

Cassil CC, Stanovick RP, Cook RF. 1969. A specific gas chromatographic method for residues of organic nitrogen pesticides. Residue Rev 26 63-87. 

Christensen JM, Rasmussen K, Koppen B. 1988. Automatic headspace gas chromatographic method for the simultaneous determination of trichloroethylene and metabolites in blood and urine. J Chromatogr 442 317-323. 

The near-UV illuminated titanium dioxide (anatase) powder flow reactor, as well as the gas chromatographic methods for analysis of effluents, has been described in detail earlier [2]. The procedvu-es followed were substantially those of Luo and OUis [1], and Sauer et al. [2]. 

Ulberth F (1998) A rapid headspace gas chromatographic method for the determination of the butyric acid content in edible fats. Z Lebensm Unters Forsch 2o6A 305-3oy. 

Extraction or dissolution almost invariably will cause low-MW material in a polymer to be present to some extent in the solution to be chromatographed. Solvent peaks interfere especially in trace analysis solvent impurities also may interfere. For identification or determination of residual solvents in polymers it is mandatory to use solventless methods of analysis so as not to confuse solvents in which the sample is dissolved for analysis with residual solvents in the sample. Gas chromatographic methods for the analysis of some low-boiling substances in the manufacture of polyester polymers have been reviewed [129]. The contents of residual solvents (CH2C12, CgHsCI) and monomers (bisphenol A, dichlorodiphenyl sulfone) in commercial polycarbonates and polysulfones were determined. Also residual monomers in PVAc latices were analysed by GC methods [130]. GC was also... 

Sass S, Fisher TL, Steger RJ, et al. 1982. Gas-chromatographic methods for the analysis of trace quantities of isopropyl methylphosphonoflouridate and associated compounds, in situ and in decontamination effluent. J Chromatogr 238(2) 445-456. 

Gas chromatographic methods are used for the analysis of organic additives extracted from polymers with solvents and other liquid media or evolved by heating. 

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. 

Kublin and Kaniewska [52] used a gas chromatographic method for the determination of miconazole and other imidazole antimycotic substances. The conditions have been established for the quantitative determination of miconazole and the other drugs, which are present in pharmaceuticals such as ointments and creams. The column, packed with UCW-98 on Chromosorb WAW, and flame-ionization detector were used. The statistical data indicate satisfactory precision of the method, both in the determination of imidazole derivatives in substances and in preparation. 

Guo et al. [53] developed a gas chromatographic method for the analysis of miconazole nitrate in creams and injections. The conditions were flame ionization detector, stationary phase of 5% SE 30 support of Chromosorb W (AS-DMCS, 80—100 mesh) packed column 3 m x 3 mm column temperature 275 °C injection temperature 290 °C and diisooctyl sebacate and internal standard. The average recoveries for creams and injections were 97.7 and 101.4%, respectively. The relative standard deviations were 2.2 and 1.3%, respectively. 

Table 7. Reported gas chromatographic methods for valproic acid... 

Kim, Y.-H., Woodrow, J. E., Seiber, J. N. (1984) Evaluation of a gas chromatographic method for calculating vapor pressures with organophosphorus pesticides. J. Chromatogr. 314, 37-53. 

Tse, G., Orbey, H., Sandler, S. I. (1992) Infinite dilution activity coefficients and Henry s law coefficients for some priority water pollutants determined by a relative gas chromatographic method. Environ. Sci. Technol. 26, 2017-2022. 

Chen, H., Wagner, J. (1994b) An efficient and reliable gas chromatographic method for measuring liquid-liquid mutual solubihties in alkylbenzene + water mixtures Toluene + water from 303 to 373 K. J. Chem. Eng. Data 39, 474-479. 

Neill et al. [22] have described a headspace gas chromatographic method for the determination of carbon dioxide (fugacity) in seawater. This method requires a small water sample (60 ml), and provides for rapid analysis (2 min). 

Chian et al. [69] point out that the Bellar and Iichtenberg [65] procedure of gas stripping followed by adsorption onto a suitable medium and subsequent thermal desorption onto a gas chromatograph-mass spectrometer is not very successful for trace determinations of volatile polar organic compounds such as the low molecular weight alcohols, ketones, and aldehydes. To achieve their required sensitivity of parts per billion, Chian et al. [69] carried out a simple distillation of several hundred ml of sample to produce a few ml of distillate. This achieved a concentration factor of between 10 and 100. The headspace gas injection-gas chromatographic method was then applied to the concentrate obtained by distillation. 

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