Coulson Electrolytic Conductivity Detector Research Articles

Chlorine-Selective Detection in Supercritical Fluid Chromatography using a Coulson Electrolytic Conductivity Detector

Abstract A Coulson electrolytic conductivity detector has been coupled successfully to a supercritical fluid chromatograph, providing chlorine-selective detection. This involves minimal modification of the detector and no modification of the SFC or its operation. The general operating parameters of the SFC/CECD system were established by direct injection of three probe compounds: chlordane, γ-lindane, and hexachlorobenzene. Next, the SFC separation of a test mixture containing phenol, γ-lindane, and several chlorinated phenols and related compounds was optimized using UV-Vis and FID detection. The mixture was then separated using the same chromatographic method but with the CECD in line with the UV-Vis detector. The response of the CECD was linear and selective for chlorinated compounds. Limits of detection for the test mixture by CECD ranged from 80 – 250 ng/μL, corresponding to approximately 14 – 44 ng of chlorine on column, and were dependent on chromatographic conditions, but independent of analyte st...

Ethyl carbamate analysis in fermented products - A comparison of measurements of mass-spectrometry, thermal-energy analyzer, and hall electrolytic conductivity detector

4. References > 1000 jAg/L. Typically, the concentration is low in wine and high in some spirits; the concentration is particularly high in some plum brandies but is low in gin and vodka. Literature methods [1,2,31 rely on sample clean-up followed by packedcolumn GC and detection by FID, alkali flame ionisation, electron capture, or Coulson electrolytic conductivity detector and allow measurements down to 10 Itg/L. The clean-up procedure required for levels below 100 jg/L is extensive and MS confirmation is still required. I.5 I~a 21 In the course of a study of ethyl carbamate levels in alcoholic beverages on sale in U.K., different methods of separation and measurement were as-

Headspace Gas Chromatographic Determination of Methylene Chloride in Decaffeinated Tea and Coffee, with Electrolytic Conductivity Detection

A headspace gas chromatographic procedure is described for the determination of methylene chloride (MC) in decaffeinated tea and coffee. The tea or coffee sample, with added methylene bromide (MB) internal standard, is equilibrated for 1.5 h at 100 degrees C in aqueous sodium sulfate before manual headspace sampling. MC and MB are separated on a Porasil A column at 160 degrees C and detected by using a Coulson electrolytic conductivity detector. For coffee and tea samples spiked at 1.3 ppm MC, as well as commercially decaffeinated teas and coffees containing up to 8 ppm MC, coefficients of variation were 10% or less. For decaffeinated teas, problems involving sample homogeneity and loss of MC before sealing the headspace vial had to be overcome. Similar problems with decaffeinated instant and ground coffees were minimal. The headspace procedure was superior to a previously reported distillation technique. MC was readily detected at 0.05 ppm. Fourteen decaffeinated teas and 15 decaffeinated coffees were analyzed; MC was detected at levels that ranged up to 15.9 and 4.0 ppm, respectively.

Evaluation of Electrolytic Conductivity Detection for the Gas Chromatographic Analysis of Six Polar Organonitrogen Herbicides

Abstract The Coulson electrolytic conductivity detector (nitrogen mode) was evaluated for the detection in foods of six polar organonitrogen herbicides containing phenolic or carboxyllic moieties. The herbicides were extracted from the crop materials with acetone and partitioned between water and dichloromethane/hexane (1:1). The organic extract was reduced in volume and treated with ethereal diazomethane. The methylated products were then cleaned up on a 2% deactivated Florisil column and analysed by gas chromatography. Detection limits ranged from 0.01-0.1 ppm depending upon type of crop and herbicide. Recovery studies indicated that the extraction procedure removed 40-90% of added herbicide, from the foods at 0.1 and 1.0ppm.

Chlorine-selective detection for liquid chromatography with a Coulson electrolytic conductivity detector

Chlorine-selective detection for liquid chromatography with a Coulson electrolytic conductivity detector

A survey of fish products for volatile N‐nitrosamines

AbstractA study was undertaken to determine the levels of nitrate, nitrite and volatile N‐nitrosamines of various fish products (halibut, salmon, cod, sole, ocean perch, scallops). The samples were analysed for five volatile nitrosamines, namely dimethyl‐nitrosamine (DMN), diethylnitrosamine (DEN), dibutylnitrosamine (DBN), nitrosopyrrolidine (NPyr) and nitrosopiperidine (NPip), all of which are potent carcinogens. Both gas–liquid chromatographic (Coulson electrolytic conductivity detector, pyrolytic mode) and thin‐layer chromatographic methods were used for estimating the levels of nitrosamines. The average level of nitrate was 8 part/106 (range 0–94 parts/106), and nitrite was present in traces only. Traces of DMN (3–12 parts/109) were found in some uncooked (raw) fish. Increased levels of DMN (3–18 parts/109) and traces of DEN (4–14 parts/109) were observed after baking and frying, indicating formation of these compounds during cooking. None of the samples contained DBN, NPyr or NPip. In 10 out of 15 samples the identities and levels of DMN and DEN were confirmed by gas liquid chromatography–high resolution mass spectrometry.

Evaluation and comparison of selective gas chromatographic detectors for the analysis of pesticide residues

A series of studies is described on the evaluation and comparison of some selective gas chromatographic detectors used in pesticide residue analysis. A detailed study of the optimization and response characteristics of the CsBr and RbCl three-electrode alkali flame ionization detector for N and P compounds, the Coulson electrolytic conductivity detector in the nitrogen, sulphur and pyrolytic modes of operation and the sulphur phosphorus emission detector, a type of flame photometric detector, was carried out to obtain maximum sensitivity and reliability for the analysis of pesticide residues in various biological substrates. It was observed that the alkali flame and electrolytic conductivity detector responses to nitrogen compounds were of the same order, while the electrolytic conductivity detector was more sensitive than the flame photometric detector to sulphur compounds. Also, attempts were made to correlate the responses from these different detector systems using the insecticide chlorpyrifos which contains P, S, Cl and N atoms. The use of chlorpyrifos as an evaluation standard in verifying the acceptable performance of these types of detectors is recommended.

Simple water flow control for the Coulson electrolytic conductivity detector

Simple water flow control for the Coulson electrolytic conductivity detector

The reliability of a procedure for the determination of nitrosamines in food

A procedure is described for the clean-up process used in this Laboratory prior to the analysis of foodstuffs for the presence of traces of nitrosamines. Recoveries from this procedure were estimated by the gas chromatographic separation of the individual nitrosamines and subsequent detection by a Coulson electrolytic conductivity detector. The ability of the detector to give a reproducible response has been assessed, as was the retention stability of the GLC system. A similar study on a combined gas chromatographic-mass spectrometric system used for the confirmation of the presence of nitrosamines is also described. The value of the Coulson detector for screening purposes prior to mass spectrometric confirmation was assessed using samples of cheese, fish, meat and some other commodities.

Further Survey of Cured Meat Products for Volatile N-Nitrosamines

Abstract Eighty samples of various kinds of cured meat products were analyzed for volatile nitrosamines. Nitrosopyrrolidine (NPy) was determined by using thin layer chromatography and simple dialkylnitrosamines were measured by using a gas-liquid chromatographic (GLC) method with a Coulson electrolytic conductivity detector (pyrolytic mode). Seventeen samples contained 13–105 ppb NPy; 29 samples contained 2–35 ppb dimethylnitrosamine (DMN) ; 9 samples contained 2-25 ppb diethylnitrosamine (DEN). In a few cases the identities of NPy, DMN, and DEN were confirmed by GLC-mass spectrometry.

Gas Chromatographic Determination of Nitric Oxide (NO) In Cigarette Smoke

Abstract A method has been developed for the determination of nitric oxide in the gas phase of cigarette smoke using a Coulson electrolytic conductivity detector. A sample-averaging smoking device was used to sample the gas phase and transfer it to the detector via a gas chromatograph containing a Porapak P column. This method was applied successfully to a series of experimental filter cigarettes.

Enhancement of the sensitivity and selectivity of the Coulson electrolytic conductivity detector to chlorinated hydrocarbon pesticides

Enhancement of the sensitivity and selectivity of the Coulson electrolytic conductivity detector to chlorinated hydrocarbon pesticides

Nitrate, Nitrite, and Dimethylnitrosamine in Cured Meat Products

Abstract Nitrate, nitrite, and dimethylnitrosamine (DMN) were determined in 197 samples of various kinds of meat products. Nitrate and nitrite were determined by the method of Kamm et al. (1965), and DMN was estimated semiquantitatively by a GLC method using a Coulson electrolytic conductivity detector (pyrolytic mode). The average levels of nitrate and nitrite were 181 ppm (range, 0–3467 ppm) and 28 ppm (range, 0–252 ppm), respectively. Trace amounts (2–12 ppb) of DMN were present in 57 samples; others were negative. As no mass spectrometric confirmation of the identity of DMN was carried out, the results should be considered as only tentative and not as an absolute proof of the presence of DMN. Except in a few types of meat products, the concentrations of nitrate or nitrite did not correlate with that of DMN detected in the samples.

An evaluation of the alkali flame ionisation detector and the coulson electrolytic conductivity detector in the analysis of N-nitrosamines in foods

A comparison is made of the performance characteristics of two dissimilar nitrogen detectors. The various parameters influencing the specificity and sensitivity of these detectors are discussed and experience gained in their use for the analysis of foods for traces of nitrosamines is described. Only slight differences in the sensitivities of the two detectors were found but the Coulson electrolytic conductivity detector was more selective and less disturbed by small changes in operating parameters, and hence is considered the more suitable for routine use in this field of analysis. A flow diverting system is described which enables the thermionic detector to be used both with chlorinated solvents and injection volumes of hydrocarbon solvents greater than 2 μl.

Determination of sulphur- and chlorine-containing pesticides with an electrolytic conductivity detector

The response of a number of sulphur-containing compounds, some of which also contained chlorine and nitrogen, were investigated using both the pyrolytic and oxidative modes of operation of the Coulson electrolytic conductivity detector. The effects of variation in furnace temperature and oxygen flow were studied. Half-scale responses for thirty-six sulphur compounds obtained in the pyrolytic mode at 850°, were in the 6–100 ng range which compared favourably with flame photometric detection in the sulphur mode. Also in the pyrolytic mode, a similar range of responses was obtained from a study of thirteen organochlorine insecticides. Responses were found to be linear in the range 2 to 1000 ng of sulphur with as low as 0.5 ng of sulphur and/or chloine being detected. In the pyrolytic mode nitrogen-containing compounds produced interference. The use of silver scrubbers for chloride removal in the oxidative mode although imparting selectivity also resulted in decreased sulphur response and lack of reproducibility.

GAS CHROMATOGRAPHIC DETERMINATION OF VOLATILE NITROSAMINES IN FOODS

Methods are presented for determination of certain volatile nitrosamines which have been reported to occur in foods. Nitrosamines were removed from foods using a Likens‐Nickerson extractor; 60% of added dimethylnitrosamine and 70% of added diethyl‐nitrosamine were recovered from 10 rig/g aqueous solutions. Potential gas chromatographic (GC) interferences were removed from the extract by a simple acid extraction step and, when needed, by liquid column chromatography. Dilute solutions containing nitrosamines were analyzed directly with a GC solvent stripping technique. Nitrosamines were detected with a Coulson electrolytic conductivity detector operated in the pyrolytic mode and with a flame ionization detector. Sensitivities of these detectors are compared for selected volatile alkyl and heterocyclic nitrosamines of potential significance in foods. The specificity of the Coulson detector is demonstrated for analysis of extracts of smoked fish and a number of processed meats. Additional clean‐up of concentrates from foods is required to insure unambiguous identification of nitrosamines by combined GC‐mass spectrometry.

Selective Detection of Chlorinated Insecticides in the Presence of Polychlorinated Biphenyls

Abstract A gas chromatographic method for selectively detecting chlorinated insecticides in the presence of polychlorinated hiphenyls is reported. A Coulson electrolytic conductivity detector was modified to allow precise control of furnace temperature and hydrogen reaction gas flow. A furnace temperature of 600°C and a hydrogen flow of 1-2 ml/min were most advantageous for selective detection of chlorinated insecticides in the presence of polychlorinated hiphenyls.

Evaluation of the Electrolytic Conductivity Detector for Residue Analyses of Nitrogen-Containing Pesticides

The Coulson electrolytic conductivity detector for nitrogen compounds has been found to be sensitive, specific, reliable, and easy to use. The detection limit has been extended down to 0.1 nanogram of organic nitrogen with a selectivity of 10,000:1 or more against organic chlorine, sulfur, phosphorus, and carbon. The detector can be operated for extended trouble-free periods with only routine maintenance. The wide distribution of organic nitrogen compounds does not appear to present any serious obstacles to the general applicability of this detector to pesticide-residue analyses of crops in the range of 0.02 ppm.