APCI triazines

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]. 

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]. 

Most reported triazine LC applications are reversed-phase utilizing C-8 and C-18 analytical columns, but there are also a few normal-phase (NH2,CN) and ion-exchange (SCX) applications. The columns used range from 5 to 25-cm length and from 2 to 4.6-mm i.d., depending on the specific application. In general, the mobile phases employed for reversed-phase applications consist of various methanol and/or acetonitrile combinations in water. The ionization efficiency of methanol and acetonitrile for atmospheric pressure chemical ionization (APcI) applications were compared, and based on methanol s lower proton affinity, the authors speculated that more compounds could be ionized in the positive ion mode when using methanol than acetonitrile in the mobile phase. 

Liquid chromatography -APCI-MS is applicable to many different types of pesticide structures, such as triazines, phenylurea herbicides, acetanilides, and OPPs. A study of 12 pesticides and pesticide degradation products demonstrated the sensitivity of the technique for OPP determination, with detection limits for water samples of about 0.001-0.005 /zg/L (32). 

In order to determine ureas and metabolites of triazines and ureas in agricultural soils, reverse-phase liquid chromatography was used with atmospheric pressure chemical ionization/mass spectrometry (APCI/MS), in positive mode. Gas chromatography/ion trap mass spectrometry was used in MS/MS mode to analyze the parent compounds of the triazines and chloroacetanilides. Method performance was much better in GC-MS/MS than in LC-MS, and acetochlor LOQ was dramatically improved by using GC-MS/MS, this herbicide being very poorly ionized into the APCI interface. 

A comparison between APCI-LC/MS and PB-LC/MS was conducted for the determination of a priority group of herbicides in water, including phenylureas, triazines, and chlorophenoxy acids. The potential of both ionization techniques for the monitoring of environmental matrixes was demonstrated. However, APCI was approximately ten-fold more sensitive than PB, both in negative and positive ionization mode. ... 

In a SPE-LC-APCI-MS/MS study of 37 polar herbicides in water, (mainly triazines, phenylureas, and phenoxy acids), a 5- to 50-fold improved detectability was observed for the combined acetonitrile desorption-methanol gradient procedure, compared to the traditional acetonitrile only approach. 

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... 

Dagnac, T., Jeannot, R., Bristeau, S., Mouvet, C., and Baran, N., Determination of chloro-acetanilides, triazines and ureas and some of their metabolites in soils by pressurized fluid extraction, GC/MS/MS AND LC-APCI/MS. J. Chromatogr. A, 1067, 225-233, 2005. 

Since triazines are very mobile in the aquatic environment, the presence of these pesticide types in groundwater samples could be confirmed. Pollution was observed when neutral pesticides contained in shallow groundwater samples from two sandy and two clay catchment areas were analysed in APCI mode [351]. The most frequently (> 300 samples) determined compound was atrazine with its degradation products. 

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... 

Different antifouling pesticides of triazine type were determined in Portuguese rivers by APCI-LC-MS(-i-) after SPE for concentration, which was performed with Oasis cartridges [323]. 

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]. 

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... 

Triazines and other pesticides Atrazine, acetochlor, alachlor GC-MS, LC-MS (APCI)... 

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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