Tandem mass spectrometric analysis of quaternary ammonium pesticides

Abstract

A detailed MS(n) study on an ion trap instrument of the quaternary ammonium pesticides paraquat, diquat, difenzoquat, mepiquat and chlormequat reveals a number of ions not reported previously, and has allowed examination of the fragmentation pathways. A number of transitions that are highly specific to each quat have been identified. Optimal ion trap operating conditions determined using Simplex optimisation can promote either detection of a particular fragmentation transition or a range of MS/MS product ions with a high overall signal response. Thus, fragmentation conditions were optimised to enhance the specificity or sensitivity of MS/MS methods.

Cluster ions of diquat and paraquat in electrospray ionization mass spectra and their collision‐induced dissociation spectra

“…), [1][2][3]5,7,[9][10][11][12][13][14][15] deprotonation products ([Cat-1] þ ), [1][2][3][4][5][6][7][8][10][11][12][14][15][16] cation fragments 1,3,[5][6][7][9][10][11][13][14][15] and clusters containing salt anions (cationized ion pairs). 4,9,11,16 This diversity in ion species reflects both the general complexity of processes during ESI and a specificity of processes for organic salts combining features of organic (fragmentation) and inorganic (ionic composition) compounds.…”

Ion-trap versus quadrupole for analysis of quaternary ammonium herbicides by LC-MS

“…When Navigator 1.0 software was used, fragmentation was controlled by a single parameter known as the relative collision energy, which includes the parameters mentioned above. The collision energy was optimized for each quat but although product ions were detected, a non-stable signal was obtained for both precursor and product ions with m/z < 200, as reported by Evans et al for CQ [24]. Although MS-MS experiments could not be carried out, the possibility of obtaining structural data with high sensitivity could be regarded as a useful tool for comparing ion trap and quadrupole systems in single stage experiments.…”

Liquid Chromatography-Ion Trap-Mass Spectrometry and its Application to Determine Organic Contaminants in the Environment and Food

“…Two product ions, at m/z 528 [35,36,39,[41][42][43]48,49]. Phenylureas yield an ion at m/z 72 by MS 2 , corresponding to [O=C=N(CH 3 ) 2 ] + .…”

“…Tetracycline ++ ++ +++ ++ [29,30] Macrocyclic lactones -- liquid-phase chemistry plays a key role in the ion formation on ESI, which works well with any compound that is ionized in solution, such as ammonium quaternary compounds, alkylbenzene sulfonates, and acidic herbicides [36,42,47,49,50,75]. However, the literature also shows that there is not a unique modus operandi because most organic contaminants are complex molecules that contain basic sites that can easily be protonated and electronegative atoms that have tendency to attract electrons, which makes difficult to predict their course according to the theory of ionization.…”

“…The same behavior is observed for monuron, which differences from diuron only by a chlorine atom on the benzene ring. Several authors applied the ion trap LC-MS n to study the CAD fragmentation of pesticides with typical examples of positive-and negative-ion fragmentation [35,42,49,50,113]. The CAD of [M+H] + ions (MS 2 ) often provides fragment ions by the cleavage of the lateral chain in the molecular structure.…”