ESI triazines

ESI, triazines) [537]. Recoveries observed were > 80% except for carbendazim, bu-tocarboxim, aldicarb and molinate, all better than 67% [500]. An aoTOF-MS interfaced by ESI was used to screen and identify unknown compounds and pesticides in water samples by MS and MS/MS. Structures for compounds observed besides pesticides were proposed [538]. Traces of the phenylurea pesticides Hnuron and monolinuron in water were determined quantitatively. Calibration graphs obtained after Supelclean ENVI-18 SEE were Hnear with detection limits < 25 pg [511]. Large numbers of phenylurea herbicide analyses led to the elaboration of on-line preconcentration techniques coupled to ESI-LC-MS. The procedure was demonstrated and validated with several pesticides using 10 ml of sample, resulting in detection Hmits of about 10 ng [539]. ESI-LC-MS and MS/MS were applied to quantify and to confirm 16 different herbicides of sulfonylurea [527] type in surface water samples. Surface water samples were extracted by SPE (Spe-ed RP-102). As confirmation criteria RT, molecular ion and two fragment ions besides ion abundance ratios were defined. Quantitation at 0.1 and 1.0 ppb level was demonstrated [540]. 

ESI performs well for the more polar compounds such as imidazolinone herbicides, sulfonylurea herbicides, triazine herbicides, phenoxy acid herbicides, and carbamate pesticides (to name a few). ESI also performs well with proteins and peptides. 

LC/MS/MS with selected reaction monitoring and ESI in the negative-ion mode was used to detect RDX and its degradation products in contaminated groundwater [18]. The detected degradation products were MNX (hexahydro-l-nitroso-3,5-dinitro-l,3,5-triazine), DNX (hexahydro-l,3-dinitroso-5-nitro-l,3,5-triazine) and TNX (hexahydro-l,3,5-trinitroso-l,3,5-triazine). The [M + 75] and [M + 45] were the most intense ions in the mass spectra of RDX and its degradation products. In the CID mass spectra, the base peak for RDX, MNX and DNX... 

Calibrants are required to calibrate the mass scale of any mass spectrometer, and it is important to find reference compounds that are compatible with a particular ion source. Calibrants commonly used in electron ionization (El) and chemical ionization (Cl), such as perfluorocarbons, are not applicable in the ESI mode. The right calibrants for LC-ESI-MS should (1) not give memory effects (2) not cause source contamination through the introduction of nonvolatile material (3) be applicable in both positive- and negative-ion mode. The main calibrants used or still in use to calibrate ESI-MS can be divided into the following categories polymers, perfluoroalkyl triazines, proteins, alkali metal salt clusters, polyethers, water clusters, and acetate salts. 

Triazines are analysed in positive-ion mode only. In ESI, protonated molecules are observed. Under in-source CID conditions, limited fragmentation due to the loss of an alkyl side chain is observed [9, 12, 14, 22, 34]. In APCI, triazines show an abundant protonated molecule and some fragmentation due to the loss of the alkyl side chain, e.g., for terbutylazine and teibutryn [9, 14, 22, 32, 35-36]. 

As regards identification purposes, the use of exhaustive libraries in GC/MS became a routine operation in most laboratories. In contrast, these libraries are still scarce in LC-MS applications, mainly because ESI-MS and APCI-MS spectra are strongly influenced by the instrument settings, the EC conditions, and the sample type. Therefore, much more effort should be paid to define identification and confirmation criteria for herbicide analysis by these ionization techniques. In this way, a confirmation criterion was successfully evaluated on triazines by Flow Injection Analysis... 

ESI with simazine as an internal standard was applied. Metabolisation but no mineralization could be observed [389]. APCI and ESI-MS were applied to determine humic substances and dissolved organic matter (DOM) together with the fungicide anilazine (2,4-dichlor-6-(2-chloranilino)-l,3,5-triazine) which was... 

Carbamates. A fast, sensitive and selective method for the concentration and analysis of 9 N-methylcarbamate pesticides was reported by Volmer et al. [507]. Three different SPME fibres combined with short-column ESI-LC-MS(-i-) and MS/MS were applied. The detection limits observed were 0.3-1.9 pg Signal intensities increasing by a factor of 2-7 were observed [508] using non-volatile buffers in the separation process prior to ESI-MS. After EC removal of the non-volatile buffers was essential. The results obtained by ESI and APCI-LC-MS and MS/MS for the analysis of the eight N-methylcarbamate pesticides and their degradation products were compared with results obtain with the application of TSP or PBI (cf. 15.3.3.1 TSP, carbamates) [108]. ESI-LC-MS and TSP-LC-MS were used for quantitative determination of 10 different carbamate pesticides which showed a broad variety in polarity. ESI-SIM detection limits were typically 10-60 pg which was 10-150 times better than using TSP-MS (cf. 15.3.3.1 TSP, carbamates) [509]. Interfacing a commercial ESI source to an ITMS allowed the determination of carbamates as well as triazines and azo dyes. Identification could be performed either by IT-MS/MS or by ESI-CID [424]. 

A study with environmental samples was performed analyzing 26 non-acidic (e.g. organophosphorus, carbamate, triazine, anilide, N-substituted amine and phenylurea type) and 13 acidic (urea and phenoxy acid type) target pesticides simultaneously by ESI-LC-MS with recoveries of about 80% [500]. Drinking, ground and... 

ESI-LC-MS was used to characterise and differentiate the triazine herbicides atrazine, terbuthylazine, propazine and prometryn. In source CID spectra were reported. Low-energy CID of [M-tH] ions confirmed the characteristic fragmentation patterns and permitted distinction of isomeric triazines [555]. Results obtained from ESI-LC-MS and APCI-LC-MS and MS/MS for the analysis of polar triazine pesticides in water confirmed a better performance of APCI compared to ESI (cf. 15.3.3.2 APCI, triazines) [325]. 

In a study covering a wide range of polar and acidic pesticides deethylatrazine and atrazine besides anilide, phenoxy acid, phenylurea, carbamates and other types of specific pesticides in river water were determined by ESI-LC-MS and MS/MS. Recoveries, depending on preconcentration steps, obtained with different SPE materials (PLRS-S, Hyshere-1, LiChrolut EN and Isolute ENV -i-) and at different pH values were reported [502]. Sixteen of the most widely used pesticides in Southern Italy were monitored in surface water samples taken in the Calabria region. Triazines were determined quantitatively by LC-UV and ESI-LC-MS(-i-) and were confirmed by MS [537]. In another study the simultaneous determination of 26 non-acidic (base and neutral e.g. triazine, carbamate, anilide, N-substituted amine, urea and organophosphorus type) and 13 acidic (sulfuron and phenoxy acid type) pesticides in natural waters was performed using ESI-LC-MS. Recoveries... 

SPME coupled to ESI-LC-MS was used to determine the triazine pesticides simazine, atrazine, propazine and prometryn in leachates obtained from soil samples. SPME compared with other extraction methods showed less interference from the matrix compound [513]. 

Triazines, amides, phenylureas, triazoles, triazinones, benzimidazoles, phenoxyalkanoic herbicides LC/MS and LC/MS/MS ESI (-) for acidic compounds APCI ( + ) 20-100 pgmr 2-6pgmr Environmental water... 

Most of the modern pesticides and their degradation products are characterized by medium to high polarity and thermal lability. Neutral and basic compounds (phenylureas, triazines) are more sensitive using APCI (especially in positive ion mode), while cationic and anionic herbicides (e.g., bipyridylium ions, sulfonic acids) are more sensitive using ESI (especially in negative ion mode). Based on comparative analysis of 75 pesticides, the so-called ionization-continuum diagram illustrates the relationship between compound acidity and appropriate ionization modes (Figure 2). 

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