Electron-capture capillary gas chromatography and mass spectrometry of trifluoroacetylated cytokinins

Quo vadis plant hormone analysis?

Plant hormones act as chemical messengers in the regulation of myriads of physiological processes that occur in plants. To date, nine groups of plant hormones have been identified and more will probably be discovered. Furthermore, members of each group may participate in the regulation of physiological responses in planta both alone and in concert with members of either the same group or other groups. The ideal way to study biochemical processes involving these signalling molecules is 'hormone profiling', i.e. quantification of not only the hormones themselves, but also their biosynthetic precursors and metabolites in plant tissues. However, this is highly challenging since trace amounts of all of these substances are present in highly complex plant matrices. Here, we review advances, current trends and future perspectives in the analysis of all currently known plant hormones and the associated problems of extracting them from plant tissues and separating them from the numerous potentially interfering compounds.

CE for cytokinin analyses: a review

Analyses of cytokinins are very important in both plant physiological and biomedical research as they are implicated in many biological processes. Reliable, sensitive, selective and inexpensive methods that are flexible and designed for automation are required for these analyses. This review addresses the advances made in the separation and determination of cytokinins by CE as well as the other applications of CE (i.e., determination of dissociation constants and complexation constants of cytokinins). The various CE modes used to separate the compounds and the quantification strategies are examined. Special attention is also focused on those aspects that improve on the sensitivity and/or selectivity, such as sample extraction and preconcentration, on-line preconcentration techniques (stacking), and/or specific detectors (e.g., MS). With the coupling to the preconcentration techniques and certain detection systems, numerous CE methods can potentially be adapted for the analysis of cytokinins in complex biological samples. Therefore, we would anticipate wider applications of CE methods in the near future for cytokinin analyses, which should facilitate a decrease in analysis cost and should help to improve analysis efficiency.

Comprehensive chemical derivatization for gas chromatography-mass spectrometry-based multi-targeted profiling of the major phytohormones

In the present investigation we report selection of the N-methyl-N-(tert.-butydimethylsilyl)trifluoroacetamide (MTBSTFA) reagent as the most comprehensive derivatization protocol among 17 tested reactions covering trifluoroacetylation, pentafluorobenzylation, methylations, and trimethylsilylations. MTBSTFA allowed easy and robust tert.-butyldimethylsilyl derivatization of 1-aminocyclopropane-1-carboxylic acid, indole-3-acetic acid, (+/-)-jasmonic acid, salicylic acid, (+/-)-abscisic acid, meta-topolin, and trans-zeatin. Detection limits as analysed by selected ion monitoring quadrupole GC-MS were 0.2, 0.01, 1.0, 0.02, 0.3, 0.3, and 0.9 pmol of injected substance, respectively. Analysis of gibberellic acid A3, trans-zeatin riboside and (+/-)-abscisic acid-beta-D-glucopyranosyl ester was best when coupled by splitting extracts and trimethysilylation. The MTBSTFA derivatization protocol was optimised, and validated. The preparation was insensitive to 2% residual water and to < or = 1 day storage at room temperature. The final scheme was highly reproducible and successfully applied to extracts from approximately 300 mg (fresh mass) of tobacco (Nicotiana tabacum) root and Arabidopsis thaliana seedling.

Electrophore-labeling and alkylation of standards of nucleic acid pyrimidine bases for analysis by gas chromatography with electron-capture detection

The pyrimidine bases cytosine, uracil and thymine, along with some analogues, are electrophore-labeled either with pentafluorobenzoyl chloride (PFBC), pentafluorophenylsulfonyl chloride (PPSC), or heptafluorobutyric anhydride. Subsequent alkylation is most successful for PFB-cytosine, PPS-uracil, and PPS-thymine. These same alkylated compounds also have the highest aqueous stability and respond most strongly by gas chromatography-electron-capture detection. One of these derivatives, determined to be N4-PFB-1,3-dimethylcytosine by authentic synthesis, and its 5-methyl analogue, can be detected with good precision down to the 100-fg level. Poor reproducibility is encountered at the 10-fg level.

Isolation and quantitation of isopentenyladenosine in an anise cell culture by single-ion monitoring, radioimmunoassay and bioassay

Using three different techniques, isopentenyladenosine was identified and quantitated in an anise cell line (Pimpinella anisum L.), growing on a medium without cytokinin. A method to quantitate cytokinins was developed which utilizes extraction of cytokinins in the presence of a deuterated reference compound and subsequent quantitation of the cytokinins by single-ion monitoring on a gas chromatography-mass spectrometry system. The results were compared with those obtained by radioimmunoassay as well as a bioassay. Quantitations by gas chromatography-mass spectrometry and radioimmunoassay correlated well, whereas the estimates by the bioassay gave considerably lower values.