T.A. Gough

A method for the detection of traces of nitrosamines using combined gas chromatography and mass spectrometry

Abstract A gas chromatograph and high-resolution mass spectrometer, coupled via a membrane separator, are used for the analysis of samples for traces of nitrosamines. The nitrosamines are detected by parent ion monitoring with a detection limit of 1 mg/l on injected material. The gas chromatograph incorporates a pressure-programming and peak-cutting device which is described in detail. Overall analysis time is substantially shorter than for isothermal or temperature-programmed runs.

Dual column gas chromatographic system for use in mass spectral determination of nitrosamines.

A packed gas chromatographic column and a support coated open tubular (SCOT) column are connected in series. Between the columns are two micro-volume switching valves, one enabling solvent to be vented. Short retention nitrosamines are passed through both columns, whereas longer retention nitrosamines by-pass the SCOT column by means of the other switching valve.

A study of the stability of a nitrogen-selective thermionic detector

Abstract The stability of a thermionic detector fitted with a rubidium chloride tip has been studied by comparison with the performance of a conventional flame ionisation detector. The variations of response of the detectors to a given set of conditions over an extended period of time have been measured. Values for sensitivities and detection limits are quoted, based on the response to trace amounts of dialkylnitrosamines.

Simple chemiluminescent detector for the screening of foodstuffs for the presence of volatile nitrosamines

The construction and subsequent evaluation of an apparatus for the detection of trace amounts of nitrosamines is described. The apparatus consists of a gas chromatograph, a catalytic chamber to generate nitric oxide from eluted nitrosamines, and a chemiluminescent detector to measure the infra-red emission resulting from interaction of this gas with ozone. Examples of the use of the system for determining the nitrosamine concentration in food extracts and other materials are given.

Detection of inorganic gases using a flame ionisation detector

Abstract A flame ionisation detector has been used for the detection of some inorganic gases. The use of a hydrogen-rich flame with oxygen to support combustion resulted in a significant response towards a number of inorganic gases. Conditions for optimum response are given and a table of response data and detection limits is presented. The response of the detector is highest toward nitric oxide and is the same as that observed for methane.

The reliability of peak area measurements

Abstract The reliability of various methods of area measurement commonly employed is assessed, for peaks of varying symmetry. Some quantitative data on the use of the new technique of interval programmed integration are presented, and the value of the technique is compared with existing methods. A comparison is also made between the reliability of quantitative data based on peak areas using a differential detector and step heights using an integral detector.

The trace detection of some non-volatile nitrosamines by combined gas chromatography and mass spectrometry

Abstract A gas chromatographic-mass spectrometric procedure based on characteristic-ion monitoring is described for the separation and detection of trace amounts of some non-volatile nitrosamines. A silver-frit interface and a modified spectrometer-inlet system used to transfer material from the gas chromatograph to the mass spectrometer are described.

Water adsorption by porous polymer bead gas chromatography columns

Abstract Porous polymer gas chromatographic columns are used in the quantitative estimation of water in organic samples. The reliability of using porous polymer beads for wate—alcohol analyses has been studied and the quantitative results are presented. Variations in the results were attributed to preferntial losses by adsorption of water within the columns. This was demonstrated qualitatively by introducing pure deuterated water into the gas chromatograph, allowing the water to elute, and then detecting amy residual water by raising the temperature of the column and passing the effluent into a mass spectrometer. A measure of the amounts of water lost was made by injecting known amounts of pure water onto the column, allowing the water to elute, and then driving off any residual water for subsequent detection with a calibrated gas density detector.