MALDI for Small Molecule Analysis: Triazine Pesticides
Matrix-Assisted Laser Desorption Ionization (MALDI) has been applied to a wide range of analyses and is particularly suitable for the qualitative analysis of high molecular weight samples. On the other hand, MALDI is generally considered unsuitable for low molecular weight compounds because the matrix ions interfere with sample ion detection in the low mass region. However, if these low m/z ions can be separated from each other and distinguished with sufficiently high mass resolving power, then MALDI can be expanded to the analysis of low-molecular-weight compounds. We have demonstrated this by using the JEOL MALDI SpiralTOF mass spectrometer The innovative Spiral orbital technology consisting of 4 sets of toroidal electrical sector and Matsuda plates provides ultra-high mass resolving power combined with high ion transmission.
Here we report the use of Spiral technology to collect high mass-resolving power and high mass-accuracy data for eight triazine compounds. Additionally, we report TOF-TOF data obtained with monoisotopic precursor ion selection to provide clear product-ion mass spectra for each compound.
Stock solutions of each of the triazine compounds listed in Table 1 were prepared at concentrations of 1 mg/ml in 2:1 methanol/water. Alpha-Cyano-4-hydroxyxinnamic acid (CHCA, formula = C10H7NO3) was used as the MALDI matrix. CHCA was dissolved in 1:1 water/ acetonitrile containing 0.1% trifluoroacetic acid at a concentration of 10 mg/mL. A 0.5 μL mixture of sample and CHCA (1/1, v/v) was deposited and dried on the MALDI target plate.
The SpiralTOF was operated in positive-ion mode using the full 17-meter flight path. Matrix peaks were used as internal mass reference standards for calibration with the native MS Tornado software.