Triazine analysis

The science and technology of analytical chemistry have made steady and remarkable advances over the last 50 years. Nowhere has this been more evident than for progress on methods to analyze organic chemicals developed as pesticides and, in particular, the triazine herbicides. Methods of triazine analysis traditionally involve an extraction step in which the analyte is removed from the matrix - such as soil, water, or crop. This extract is then subjected to a clean up in various ways to isolate the analyte further from the other chemical components that are extracted. The next step is to concentrate the purified fraction to a smaller volume to allow the analyte to be detected. A small portion of this final fraction is then injected into an instrument capable of selectively detecting and quantifying the triazine in the sample. 

The use of LC also has increased in use in recent years, driven by greater sensitivities of the detectors. Traditional ultraviolet (UV) and photo diode-array detectors were frequently employed in triazine analysis, but advances in source designs have provided efficient coupling of MS with LC. The advantage of LC is the ability to analyze polar metabolites not amenable to analysis using GC. Recent progress in LC/MS/MS instrumentation has enabled the direct aqueous injection (DAI) of a water sample without prior cleanup. 

It is useful to compare the spectroscopic data of 1,2,4-triazine mono-A-oxides with the data for the corresponding 1,2,4-triazines. Introduction of an A-oxide group in the 1,2,4-triazine ring changes its physicochemical properties dramatically, and the analysis of these changes allows one to determine which of three nitrogens is oxidized. The most useful method in this case is NMR spectroscopy, including H, C, and N NMR. 

Another pathway for the aromatization of the cr -adducts was found in the reactions of 3-pyrrolidino-l,2,4-triazine 4-oxide 81 with amines. Thus the treatment of 1,2,4-triazine 4-oxide 81 with ammonia leads to 5-amino-1,2,4-triazine 4-oxides 54—products of the telesubstitution reaction. In this case the cr -adduct 82 formed by the addition of ammonia at position 5 of the heterocycle undergoes a [l,5]sigmatropic shift resulting in 3,4-dihydro-1,2,4-triazine 83, which loses a molecule of pyrrolidine to yield the product 54. This mechanism was supported by the isolation of the key intermediates for the first time in such reactions—the products of the sigmatropic shift in the open-chain tautomeric form of tiiazahexa-triene 84. The structure of the latter was established by NMR spectroscopy and X-ray analysis. In spite of its open-chain character, 84 can be easily aromatized by refluxing in ethanol to form the same product 54 (99TL6099). 

Dihydro-1,2,4-triazines 95 were obtained by base-indueed ring expansion of 1-alkyl-1,2,3-triazolium salts, and their strueture in the solid state was eonfirmed by X-ray analysis [92JCS(P1)147]. 

Imidazo[l,5-t/)[l, 2,4]triazin-l(2//)-ones 504 were prepared (78-USP4115572 79JHC277 88USP4743586) by the cyclization of hydrazide 503 with triethyl orthoesters. l,2,3,4-Tetrahydro-2,4,4-trimethyl-8-nitroimidazo[ 1,5-t/J[ 1,2,4]triazin-1 -one 506 was isolated as a byproduct during the course of purification of hydrazide 505, whose structure was determined (91MI4) by crystal structure analysis. They had antiasthmatic... 

Naphtho analogues, naphtho[2,l-e]tetrazolo[l,5-6][l,2,4]triazine, naph-tho[l,2-e]tetrazolo[l,5-b][l,2,4]triazine, and naphtho[2,3-e]tetrazolo[l,5-Zj][1, 2,4]triazine, were prepared (82JOC3168 84JOC3199) by cyclization of the respective hydrazine with sodium nitrite in acetic acid or by azide displacement of a leaving group. Elucidation of the site of annulation of the tetrazole ring was accomplished by X-ray analysis and l3C-NMR spectroscopy (Scheme 189). 

Cyclocondensation of 632 with dibromoethane in the presence of sodium ethoxide gave 2,3-dihydro-6-benzyl-7//-thiazolo[3,2-h][l, 2,4]triazin-7-one, whose structure was confirmed by X-ray analysis (91MI7). 

Hop linger AJ. A QSAR investigation of dihydrofolate reductase inhibition by Baker triazines based upon molecular shape analysis. J Am Chem Soc 1980 102 7196-206. 

J. W. McFarland, Comparative Molecular Field Analysis (CoMFA) of anticoccidial triazines. J. Med. Chem., 35 (1992) 2543-2550. 

Ultrasonication was reported for the extraction of triazines from soil, previously sieved to 2 mm and stored at -18 °C, prior to analysis using CC/NPD and CC/lTD. A 5-g soil sample was placed in a polypropylene column and extracted for 15 min with 4 mL of ethyl acetate in an ultrasonic bath at room temperature. Subsequently, the solvent was filtered and collected in a graduated tube, and the extraction was repeated for another 15-min period using a second 4-mL portion of ethyl acetate. The two extracts... 

Applicators, mixers, loaders, and others who mix, spray, or apply pesticides to crops face potential dermal and/or inhalation exposure when handling bulk quantities of the formulated active ingredients. Although the exposure periods are short and occur only a few times annually, an estimate of this exposure can be obtained by quantifying the excreted polar urinary metabolites. Atrazine is the most studied triazine for potential human exposure purposes, and, therefore, most of the reported methods address the determination of atrazine or atrazine and its metabolites in urine. To a lesser extent, methods are also reported for the analysis of atrazine in blood plasma and serum. 

---