Abstract: A method of improving signal intensity of precursor ions constrained in a carrier gas in the flow tube of a SIFT-MS instrument, and an apparatus to carry out the method. The method applies an electrical potential to the flow tube to lower the diffusive loss of ions within the flow tube. The lowered diffusive loss of ions increases the sensitivity of the technique.

Abstract: A method of detecting a substance present in a gas or a gas mixture using SIFT-MS technology comprising the steps of inducing a supply of alkoxymethyl cations into the inlet of the flow tube, reacting a sample of the as with the alkoxymethyl cations, analysing the reacted gas sample, and calculating the concentration of trace levels of molecules containing heteroatoms in the reacted gas sample.

Abstract: A method of identifying a micro-organism and determining the susceptibility of the micro-organism to an antimicrobial agent by inserting a sample of the micro-organism in a primary culture container and allowing the micro-organism to multiply. The primary culture is then divided into a plurality of secondary cultures and the metabolic volatile or semi-volatile compounds (VCs) in the headspace above the cultures are analysed by SIFT-MS to ascertain whether micro-organisms exist in the culture and determine the type of micro-organism. The secondary cultures are then divided into a number of tertiary cultures and an antimicrobial agent is introduced whereupon the VCs in the headspace above the tertiary cultures are analysed by SIFT-MS to determine the susceptibility of the micro-organism to the antimicrobial agent at various concentrations of the antimicrobial agent.

Abstract: A SIFT or SIFDT apparatus in which the upstream quadrupole and the downstream quadrupole are housed within a single evacuated chamber with the upstream quadrupole being connected to the downstream quadrupole by a curved flow tube. In a preferred form the interior of the chamber is divided into sections by an electrostatic shield which shields the upstream quadrupole and source connection from the downstream quadrupole and detector.

Abstract: A SIFT or SIFDT apparatus in which the upstream quadrupole and the downstream quadrupole are housed within a single evacuated chamber (20) with the upstream quadrupole (22) being (24). connected to the downstream quadrupole (29) by a curved flow tube sections by an electrostatic shield (27) which shields the upstream quadrupole and source connection from the downstream quadrupole and detector.

Abstract: A direct comparisons of the antioxidant activities of various pure compounds (eg., Trolox®(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), extracts and biological fluids (eg. human plasma) can be effected by means of standardisable, objective method of determining and measuring the antioxidative and oxidative radical scavenging activities of a natural or synthetic substance, including the measurement of an indicator reaction product gas, ethylene, in the reaction headspace using Selective Ion Flow Tube Mass Spectrometry (SIFT-MS). This method assays ethylene liberated from ?-keto-?-methiolbutyric acid (KMBA) on reaction with peroxy radicals, other radicals or other reactive oxygen species that can oxidise KMBA to ethylene. From the production rate and concentration of the ethylene, the total antioxidant activity of an added analyte in question and its rate of reaction with oxidative free radicals may be determined.