Quantitative gas chromatographic analysis of perhalogenated compounds using a flame lonization detector

Summary In the determination of several perhalogenated compounds after gas chromatographic separation on an Apiezon L column, using a flame ionization detector, all the compounds tested gave linear area-mass plots although the coefficients observed do not lead to extrapolations which would permit quantitation of perhalogenated compounds for which no standard is available. Of the compounds tested, dibromodichloromethane, tetrachloroethene and tetrabromoethene gave good linear correlations of area ratio-mass ratio (using n-decane as the internal standard). Bromotrichloromethane and tetrabromomethane gave continuously curving area ratio-mass ratio plots which were very reproducible and could be used for graphical interpolation.     

A gas chromatographic method for the microdetermination of iodine

Summary Iodine was quantitatively converted by reaction with acetone to a form which was easily separated by gas chromatography and which was easily detected with an electron capture detector. Linear response of the detector was obtained for solutions which contained up to 1g/ml with an uncertainty of 8%. Milligram amounts of chloride or bromide andg amounts of iodide do not interfere. Amplification of the amount of reaction product and the determination of both iodine and iodide was accomplished by the addition of KIO₃.

---

Zusammenfassung Jod wird quantitativ mit Aceton umgesetzt und läßt sich dann gaschromatographisch abtrennen und mit einem Elektroneneinfangdetektor nachweisen. Dessen Anzeige ist bis zu 1g/ml linear mit einer Unsicherheit von 8%. Milligrammengen Chlorid oder Bromid bzw. Mikrogrammengen Jodid stören nicht. Die Menge Reaktionsprodukt läßt sich vervielfachen. Die Bestimmung von Jod und Jodid wird durch Zusatz von Kaliumjodat zu Ende geführt.

     

Investigating the performance characteristics of the barrier discharge ionization detector and comparison to the flame ionization detector for the gas chromatographic analysis of volatile and semivolatile organic compounds

Abstract

The response behavior and performance characteristics of the recently introduced barrier discharge ionization detector (BID) for gas chromatography (GC-BID) were investigated by analyzing different classes of organic compounds such as alcohols, alkanes, cycloaliphatic compounds, polycyclic aromatic hydrocarbons (PAHs), and others. The results obtained by GC-BID were compared with those of gas chromatography with flame ionization detection (GC-FID), aiming to demonstrate the particular merits of the new BID detector over the well-established FID. The response of the BID not only was found to be strongly dependent on the detector settings, but also shows a high dependence on the analyte class and the individual analyte. The sensitivity of the BID detector compared to the FID was higher by a factor of ca. 4 on average when considering all compounds analyzed. The relative standard deviation (RSD) was better than 5% for the majority of the cases. The BID detector showed better precision (lower RSD) in comparison with the FID for the investigated compounds. Linear calibrations were obtained for the analytes over more than four orders of magnitude with coefficients of determination typically higher than 0.999 and the limits of detection varied from 0.04 to 1.48?ng/s for the GC-BID.     

Characterization of a microelectromechanical systems-based counter-current flame ionization detector

This work is concerned with the influence of different operating parameters on the response of a counter-current micro flame ionization detector (cc-μFID) with low gas consumption for mobile applications. At cc-μFID flow rates (<10ml/min hydrogen), the response depends mainly on the oxygen flow. At 7.5ml/min hydrogen flow, highest sensitivity (13.7mC/gC) is obtained with the smallest flame chamber and nozzle size, moderate sample gas flow (2.0ml/min), and an oxygen flow above stoichiometry (9.4ml/min, λ=2.5). The largest absolute signal is obtained at increased sample gas flow (8.0ml/min). However, to prevent parting of the micro-flame by the sample gas stream, largest nozzles (smallest outflow velocity) give the best result (4.37nA). Whereas cc-μFID sensitivity is comparable with conventional FID sensitivity, peak-to-peak noise of 1pA is relatively large. Therefore, the minimum detectable carbon mass flow of 1.46×10(-10)gC/s and the minimum detectable methane concentration of 3.43ppm are larger than typical FID detection limits. μGC-μFID experiments show the difference between premixing the sample with the hydrogen or with the oxygen with respect to sensitivity and response factors. Sensitivity is decreased considerably when the column effluent is added to the oxygen instead of to the hydrogen. For hydrogen premixed samples the response factor to butane can be increased up to 0.81 (methane=1), whereas for oxygen premixed samples it is maximally 0.31. This smaller sensitivity to oxygen premixed samples and the larger variation of response factors shows the importance of the hydrogen atom during breakdown of organic molecules to single-carbon fragments before ionization.     

Gas chromatographic determination of benzene, toluene, ethylbenzene and xylenes using flame ionization detector in water samples with direct aqueous injection up to 250 microl

A simple method of solventless extraction of volatile organic compounds (benzene, toluene, ethylbenzene and xylenes) from aqueous samples was developed. This method allows direct injection of large volume of water sample into a gas chromatograph using the sorption capacity of the sorbent Chromosorb P NAW applied directly in the injection port of gas chromatograph. The system prevent water penetration into a column, keep it adsorbed on its surface until the analytes are stripped into a column, and the residual water is purging using split flow. The limit of detection ranging from 0.6 for benzene to 1.1 microg l(-1) for o-xylene and limit of quantification ranging 2.0-3.6 microg l(-1) are lower that those reached by gas chromatography with flame ionization detection and direct aqueous injection before.     

Selectivity enhancement of a metal-sensitive flame ionization detector for capillary gas chromatography

A novel modification of a hydrogen-atmosphere flamo ionization detector (HAFID) is presented which attenuates response to hydrocarbon compounds, significantly enhancing selectivity towards organometallic compounds by more than an order of magnitude. Chromatograms of an organometallic compound test mixture and regular leaded gasoline are presented to depict the specificity of the response.     

Microtechniques for the gas chromatographic determination of barbiturates in small blood samples

A method for the determination of therapeutic levels of barbituric acids in 25 microliter of whole blood is described. After extraction and controlled concentration of the extract to a volume of 5 microliter, the barbituric acids are N,N'-dimethylated using a microrefluxer. Of the total extract 20-100% is injected into the gas chromatograph. Low blanks, recoveries of 70--80% and peak ratios that are comparable to those in calibration experiments are obtained provided the detailed working instructions are followed strictly. In addition, barbiturates were determined (1 ng in 25 microliter blood) using column-switching devices and nitrogen-sensitive detection.     

Peculiarities of gas chromatographic analysis of 6N4 volatile hydrides using a helium ionization detector operated in the ionization amplification mode

A pneumovacuum circuit of a Tsvet-800-2 gas chromatograph with a helium ionization detector (HID) in the ionization amplification mode is proposed for controlling limiting trace impurities in ammonia, arsine, monosilane, and phosphine of grade 6N4. The conditions for the preparation and reliable operation of the chromatograph with the HID are systematized. The effect of an additive of (0.0–17.6) × 10^–4 mol % of hydrogen in the carrier gas of the detector on the polarity of its signal on the impurities of oxygen and nitrogen at a level of (0.5–20.0) × 10^–5 mol % is studied. Methods are proposed for eliminating systematic errors in the determination of the concentration of oxygen and nitrogen in the range from 0.5 × 10^–5 to 1 × 10^–3 mol % in 6N4 volatile hydrides, caused by “counter” impurities in the carrier gas, the mechanism of the heteropolar sensitivity of the HID, and irreversible chemical reactions of oxygen traces with phosphine and products of its decomposition on a CaA–ShM zeolite in a separating column of a chromatograph. Gas chromatography analysis of ammonia, arsine, monosilane, and phosphine of grade 6N4 was carried out.     

Thin-layer chromatographic determination of barbiturates and phenytoin in serum and blood.

A method is described for the measurement of blood, serum and/or plasma levels of hexobarbital, phenobarbital, cyclobarbital and phenytoin by ultraviolet reflectance photometry on thin-layer chromatograms. The lowest concentrations measured were 0.3-0.7 mug/ml. The accuracy was similar to that of gas chromatographic procudures. For phenytoin determinations 5-(p-methylphenyl)-5-phenylhydantoin may be used as internal standard. The method has been applied to clinico-pharmacological assays, to the measurement of cyclobarbital elimination in man following a therapeutic dose, and to the study of phenobarbital kinetics in rats using serial blood samples.     

A method for the microdetermination of carbon and hydrogen with chromatographic completion

Summary A method for the microdetermination of carbon and hydrogen with the chromatographic determination of the products of the oxidation of the substance has been developed.The accuracy of the method is within 0.2%.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 194–196, March, 1971.     

Characterization of formaldehyde by gas chromatography using multiple pulsed-discharge photoionization detectors and a flame ionization detector

Formaldehyde, water, methanol, butanal, and butanone are characterized by gas chromatography using three pulsed-discharge photoionization detectors (PDPIDs) and a flame ionization detector (FID). One of the PDPIDs is operated in helium mode, and the other two are operated in argon and krypton modes. The FID is included for comparison. The PDPIDs are used to efficiently differentiate between and quantitatively identify formaldehyde and the other three compounds in a sample mixture. This is accomplished by using butanone as the internal standard and correlating the relative responses of the four organic compounds in the helium-, argon-, and krypton-mode PDPIDs with their relative retention times.     

Some observations on the development of a gas chromatographic microwave plasma ionization detector

A novel gas chromatographic microwave plasma ionization detector (MPID) has been developed. The detector is based on the ionization of analyte caused by microwave plasma or the ionization quenching of microwave plasma by the analyte. The detector is simple in construction and can be operated without dangerous gas. It responds with high sensitivity to various kinds of chemical species that can be treated by GC. The sensitivities to 39 chemical species were shown to be in the range of 10⁻¹¹ − 10⁻⁷ g/sec.     

Gas chromatographic determination of nitrite in water by precolumn formation of 2-phenylphenol with flame ionization detection

Nitrite can be determined by its reaction with 2-aminobiphenyl in acidic medium to produce 2-phenylphenol which is quantified by gas chromatography with flame ionisation detection using biphenyl as an internal standard. The hydrolysis of the intermediate diazonium ion avoids many of the problems encountered in the conventional determination of nitrite by the diazotization of an aromatic amine (usually sulphanilamide) and coupling with N-(1-napthyl)ethylenediamine dihydrochloride to yield an azo dye followed by spectrophotometry. Unlike this method, the proposed reaction is rapid and does not suffer from interferences by copper(II), iron(III) and lead(II). The calibration graph was linear over the range 5–1000 μg/l NO₂-N and the limit of detection found to be 0.5 μg/l NO₂-N. A single analysis can be completed within 20 min. The method was not affected by coloured or turbid analyte solutions and has been used to determine nitrite in natural waters.     

Liquid chromatographic determination of barbiturates using a hollow-fibre membrane for postcolumn pH modification

A sensitive, high-performance liquid chromatographic method is described for the determination of barbiturates by postcolumn pH modification. The barbiturates (barbital, phenobarbital, hexobarbital and amobarbital) were separated on a C18 column using a mixture of methanol and water as an eluent. Then the pH of the eluent was raised to 10 by introducing ammonia or ammonium ion through a sulphonated hollow-fibre membrane inserted between the column and the detector. The detection was based on the primary ionized barbiturates at 240 nm. At barbiturate concentrations of 2.0 micrograms/ml, the within- and between-experiment precision (relative standard deviation) was 0.65-3.28 and 0.76-1.90%, respectively. The limits of detection were about 0.5-2.5 ng at a signal-to-noise ratio of 3. The method was applied to the determination of amobarbital in saliva.     

Novel on-column and inverted operating modes of a microcounter-current flame ionization detector

Improved operating modes of a microcounter-current flame ionization detector (microFID) are demonstrated. By operating the flame inside the end of a capillary gas chromatography (GC) column, the effective cell volume enclosing the flame is considerably reduced and results in significantly lower gas flows being required to produce optimal sensitivity from the stable flame. For instance, in this mode the tiny counter-current flame is situated "upside down" inside the column on the end of a stainless steel capillary delivering 4mL/min of oxygen and is stabilized by a counter flow of only 10mL/min of hydrogen carrier gas. Under these approximately fourfold reduced gas flow conditions, the microFID carbon response is linear over almost 5 orders of magnitude and yields a detection limit of 6x10(-10)gC/s. These figures agree well with those reported for the original microFID, which also similarly operated under hydrogen-rich conditions. To better simulate the oxygen-rich environment of a conventional FID flame, a novel "inverted" counter-current flow mode was also investigated. In this post-column microFID arrangement, a very lean flame is now situated on the end of a stainless steel capillary delivering 10mL/min of hydrogen, which is opposed by a counter-current flow of only 20mL/min of oxygen. The microFID detection limit obtained in this stable, oxygen-rich counter-current flame mode is 7x10(-11)gC/s with a response that is linear over almost 6 orders of magnitude. These findings are more comparable to those of a conventional FID. Overall, the low-flow sensitive microFID operating modes presented demonstrate that this detector may be potentially useful for adaptation to portable devices and related GC applications.     

Analysis of hydroxylated polycyclic aromatic hydrocarbons in urine using comprehensive two-dimensional gas chromatography with a flame ionization detector

The determination of polycyclic aromatic hydrocarbon (PAH) metabolites in human urine is the method of choice for assessing exposure to carcinogenic compounds. The objective of this study was the development of a comprehensive two-dimensional gas chromatography (GC × GC) method using a flame ionisation detector (FID) to simultaneously determine 10 hydroxylated PAH. The method was based on enzymatic deconjugation, liquid–liquid extraction, and trimethylsilyl (TMS) derivatization of the analytes by microwave heating. Satisfactory separation was achieved. The coefficient of variance was 3.8–12.8%. LOD was 0.03–0.18 μg/L, and LOQ was 0.1–0.5 μg/L. The mean recovery was 76%. The method was applied to the analysis of urine from smokers and non-smokers.