Optimisation of the quantitative determination of chlormequat by matrix‐assisted laser desorption/ionisation mass spectrometry

Abstract

The plant growth regulator chlormequat, an involatile quaternary ammonium salt, has been quantified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). Restrictions for quantitative MALDI-TOFMS analysis, such as irreproducible crystallisation and unsatisfactory laser stability, have been overcome by the application of two synthesised isotopically labelled standards and the optimisation of the measurement protocol. Data acquisition at constant laser power was compared to data acquisition at approximately constant ion abundance of the relevant ions (analyte and internal standards). Data acquisition at constant ion abundance performed better and enabled a high number of consecutive firings to the same sample deposition area. Furthermore an increased sample-to-sample repeatability and a high reproducibility over several weeks without re-calibration have been attained by this method. Linearity over three orders of magnitude (0.05 to 30 ng/microL chlormequat), with a correlation coefficient of 0.9997, was achieved using [13C3]-chlormequat as internal standard. Limit of detection and limit of determination were determined to be in the low pg/microL range for pure standard solutions. Thin-layer chromatography was applied for the removal of high amounts of choline, which is often present in plant tissue extracts and can adversely affect the ionisation and detection of chlormequat by MALDI-TOFMS. The use of two internal standards ([13C3]- and [2H9]-chlormequat) enabled direct quantification and simultaneous control of the recovery.

Small molecule analysis by MALDI mass spectrometry

“…Data acquisition at constant laser power was compared to data acquisition with constant ion abundance [131]. The latter work showed improved reproducibility as well as allowing more consecutive laser shots at the same position.…”

“…An instrumental protocol for MALDI data collection can also be a powerful tool to minimize signal deviations [21,107,130,131]. Data acquisition at constant laser power was compared to data acquisition with constant ion abundance [131].…”

Biomedical application of MALDI mass spectrometry for small‐molecule analysis

“…Horak, Werther, and Schmid (2001) compared data acquisition at constant laser power with data acquisition at constant ion abundance for quantitative analysis of chlormequat. Data acquisition at constant ion abundance resulted in a better sample-to-sample reproducibility compared to data acquisition at a constant laser power.…”

Novel Potentiometric Sensors of Molecular Imprinted Polymers for Specific Binding of Chlormequat

“…However, it has also been widely used to improve fruit setting, prevent premature fruit drop, increase fruit size and reduce the need for tree pruning in top fruit, mainly pears. CMQ residues may be monitored by mass spectrometry/liquid chromatography [7 -10] or liquid chromatography/tandem mass spectrometry [11], thin layer chromatography [12], conductometric detection coupled to ion chromatography [13,14], indirect UV detection coupled to electrophoresis [15,16], voltammetry [17] and potentiometry [18,19] methods.…”