The recent evolution of the quadrupole ion trap mass spectrometer—an overview

Ion scanning or ion trapping: Why not both?

The present contribution describes analogies and differences between the quadrupolar ion trap (QIT) and the quadrupole mass analyzers, shows the potentialities of their combination in a single instrument and presents a review of applications of such a technology in different fields. The first section describes the quadrupole mass filter (QMF), outlining its principles of operation and the ion sorting procedure according to the use of oscillating electric fields inducing stable trajectories to the ions allowing them to reach the detector. Multiple quadrupole systems (normally triple quadrupoles) are then explained, showing their use in tandem mass spectrometry in space experiments (MS/MS-in-space). QIT principles of operation are then examined, pointing out that in this case the use of the same combination of oscillating electric fields takes advantage of unstable ion trajectories for their sorting. Substantially, analogies and differences between QMF and QIT come out, which consist in the fact that QMF is a scanning mass analyzer, whereas QIT is a sequential mass analyzer. In addition, the section underlines that QIT is capable to perform tandem mass spectrometry in time experiments (MS/MS-in-time). Later, the possibility to use a quadrupole as a trapping system with a prevailing dimension (linear ion trap [LIT]) is taken into consideration, and the possibility to combine both QMF and LIT in a single instrument, a QTrap mass spectrometer, is illustrated. In this frame, a lot more experiment types are possible with respect to both standalone triple quadrupoles and LIT, and they are described as well. Several combinations of these QTrap features can be used in information dependent acquisition (IDA) mode, allowing the high versatility of this instrumental configuration. The second section deals with a review of applications in different fields. These are organized by kind of QTrap and IDA features and cover different topics in biological, medical, agrochemical, nutritional and environmental fields.

Quadrupole ion trap studies of fundamental organic reactions

Over the past several decades, quadrupole ion traps have become important instruments in the study of gas phase ion/molecule reactions. As a part of this work, they have been employed in a number of studies focused on fundamental organic reaction mechanisms. In this review, the general features and limitations of quadrupole ion traps are discussed followed by a description of representative ion trap studies of organic reaction mechanisms such as substitution, elimination, and acyl transfer reactions.

Low pressure chemical ionization in ion trap mass spectrometry

This article presents the specificities of low pressure chemical ionization in ion trap mass spectrometry. One main feature is the ability to perform chemical ionization with liquid reagents as readily as with "conventional" gases (methane, isobutane and ammonia). The reactivities and analytical applications of gas and liquid reagents are summarized from literature data and are compared when possible.

Application of chromatography and mass spectrometry to the characterization of food proteins and derived peptides

The following review describes the development of mass spectrometry off-line and on-line coupled with liquid chromatography to the analysis of food proteins. It includes the significant results recently obtained in the field of milk, egg and cereal proteins. This paper also outlines the research carried out in the area of food protein hydrolysates, which are important components in foodstuffs due to their functional properties. Liquid chromatography and mass spectrometry have been particularly used for the characterization of food peptides and especially in dairy products.

Quantitative liquid chromatographic-tandem mass spectrometric determination of orlistat in plasma with a quadrupole ion trap

This report evaluates the use of a quadrupolar ion trap for quantitation in a bioanalytical laboratory. The evaluation was accomplished with the cross-validation of an LC-MS-MS quantitative method previously validated on a triple quadrupole mass spectrometer. The method was a multi-level determination of the anti-obesity drug, orlistat, in human plasma. The method has been refined previously on a triple quadrupole instrument to provide rapid sample throughput with robust reproducibility at sub-nanogram detection limits. Optimization of the method on the ion trap required improved chromatographic separation of orlistat from interfering plasma matrix components coextracted during the initial liquid-liquid extraction of plasma samples. The ion trap produces full-scan collision-induced dissociation mass spectra containing characteristic orlistat fragment ions that are useful for quantitation. Data collection on the ion trap required a precursor ion isolation width of 3.0 Da and optimal quantitative results were obtained when three fragment ions were monitored with a 1.8 Da window for each ion. Although a direct cross-validation between the ion trap and the tandem triple quadrupole mass spectrometer was not possible, quantitative results for orlistat comparable to those obtained from the triple quadrupole instrument were achieved by the ion trap with the modified method. The limit of quantitation for orlistat in plasma on the ion trap was 0.3 ng ml(-1) with a linear dynamic range of 0.3 to 10 ng ml(-1). Precision and accuracy varied from 4 to 15% over the quantitation range. The overall results provide an example of the utility of an ion trap in bioanalytical work.