Herbicide

HRAC  C1 WSSA  5; 1,3,5-triazine

NOMENCLATURE

Common name atrazine (BSI, E-ISO, (f) F-ISO, ANSI, WSSA, JMAF)

IUPAC name 6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine 

Chemical Abstracts name 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine 

CAS RN [1912-24-9]  EEC no. 217-617-8  Development codes G 30 027 (Geigy) 

PHYSICAL CHEMISTRY

Composition Tech. is ³96% pure.  Mol. wt. 215.7  M.f. C8H14ClN5  Form Colourless powder.  M.p. 175.8 ºC  B.p. 205.0 °C/101 kPa  V.p. 3.85 ´ 10-2 mPa (25 ºC) (OECD 104)  KOW logP = 2.5 (25 ºC)  Henry 1.5 ´ 10-4 Pa m3 mol-1 (calc.)  S.g./density 1.23 (22 °C)  Solubility In water 33 mg/l (pH 7, 22 ºC). In ethyl acetate 24, acetone 31, dichloromethane 28, ethanol 15, toluene 4.0, n-hexane 0.11, n-octanol 8.7 (all in g/l, 25 ºC).  Stability Relatively stable in neutral, weakly acidic and weakly alkaline media. Rapidly hydrolysed to the hydroxy derivative in strong acids and alkalis, and at 70 ºC in neutral media; DT50 (pH 1) 9.5, (pH 5) 86, (pH 13) 5.0 d.  pKa 1.7, v. weak base 

COMMERCIALISATION

History Herbicide reported by H. Gysin & E. Knüsli (Proc. Int. Congr. Crop Prot., 4th, Hamburg, 1957). Introduced by J. R. Geigy S.A. (now Syngenta AG).  Patents BE 540590; GB 814947  Manufacturers Crystal; Du Pont; Hegang Heyou; Makhteshim-Agan; Meghmani; Nagarjuna Agrichem; Oxon; Rallis; Sanachem; Syngenta

APPLICATIONS

Biochemistry Photosynthetic electron transport inhibitor at the photosystem II receptor site. Maize tolerance is attributed to rapid detoxification by glutathione transferases.  Mode of action Selective systemic herbicide, absorbed principally through the roots, but also through the foliage, with translocation acropetally in the xylem and accumulation in the apical meristems and leaves.  Uses Pre- and post-emergence control of annual broad-leaved weeds and annual grasses in maize, sorghum, sugar cane, pineapples, chemical fallow, grassland, macadamia nuts, conifers, industrial weed control. In Europe, use is concentrated in maize and sorghum. Used also in combinations with many other herbicides.  Phytotoxicity Phytotoxic to many crops, including most vegetables, potatoes, soya beans, and peanuts.  Formulation types FW; GR; SC; WG; WP.  Selected tradenames: 'AAtrex' (USA) (Syngenta); 'Aktikon' (Nitrokémia); 'Atranex' (Makhteshim-Agan); 'Atrataf' (Rallis); 'Atratylone' (Agriphar); 'Atrazina' (Cequisa); 'Atrazol' (Sipcam); 'Coyote' (Defensa); 'Dhanuzine' (Dhanuka); 'Fogard' (Caffaro); 'Mebazine' (Aventis); 'Sanazine' (Sanachem); 'Surya' (Nagarjuna Agrichem); 'Triaflow' (Inquiport); 'Vectal' (Aventis); 'Zeazin S 40' (Istrochem); mixtures: 'Bicep II Magnum' (+ benoxacor+ S-metolachlor) (Syngenta); 'Bicep II' (+ benoxacor+ metolachlor) (Syngenta); 'Bicep Magnum' (+ S-metolachlor) (Syngenta); 'Gesaprim' (+ terbutryn) (Europe) (Syngenta); 'Marksman' (+ dicamba) (dicamba as potassium salt) (Syngenta, BASF); 'Trinovin' (+ amitrole+ simazine) (Efthymiadis)

OTHER TRADENAMES

'Atradex' (Crop Care); 'Atred' (Chemiplant); 'Azoprim' (Azot); 'Cornazine' (Papaeconomou); 'Crisazina' (Crystal); 'DG90' (Sipcam UK); 'Herpazine' (Agrochem); 'Trac' (Atanor); 'Zeacas' (CAS) mixtures: 'Bicep' (+ metolachlor) (USA) (Syngenta); 'Clark' (+ bromoxynil) (CFPI Nufarm, Syngenta); 'Primextra Safeneur' (+ benoxacor+ metolachlor) (Syngenta); 'Sutazine' (+ butylate) (Syngenta); 'Alazine' (+ alachlor) (Makhteshim-Agan); 'Aspect' (+ flufenacet) (Bayer); 'Aterbutex' (+ terbutryn) (Makhteshim-Agan); 'Athado Invierno' (+ terbumeton+ terbuthylazine) (Probelte); 'Atoll' (+ isoxaflutole) (Aventis); 'Atramet Combi' (+ ametryn) (Makhteshim-Agan); 'Axiom AT' (+ flufenacet+ metribuzin) (Bayer); 'Basis Gold' (+ nicosulfuron+ rimsulfuron) (Du Pont); 'Bellater' (+ cyanazine) (BASF); 'Bullet' (+ alachlor) (Monsanto); 'Century' (+ dimethenamid) (BASF); 'Degree Xtra' (+ acetochlor) (with safener) (Monsanto); 'Erunit' (+ acetochlor) (Nitrokémia); 'Extrazine II' (+ cyanazine) (Du Pont); 'Field Master' (+ acetochlor+ glyphosate) (glyphosate as isopropylammonium salt) (Monsanto); 'Fultime' (+ acetochlor+ dichlormid) (Dow AgroSciences); 'Guardsman' (+ dimethenamid) (BASF); 'Harness Extra' (+ acetochlor) (Monsanto); 'Karal' (+ bromoxynil) (CFPI Nufarm); 'Laddok' (+ bentazone-sodium) (BASF); 'Lariat' (+ alachlor) (Monsanto); 'Leadoff' (+ dimethenamid) (Du Pont); 'Propachlor Doble' (+ alachlor) (Probelte); 'Ready Master ATZ' (+ glyphosate) (glyphosate as isopropylammonium salt) (Monsanto); 'Shotgun' (+ 2,4-D-2-ethylhexyl) (UAP); 'Simapron Doble' (+ simazine) (Probelte); 'Simazat' (+ simazine) (Drexel); 'Triamex' (+ simazine) (Aventis); 'Zeazin Mix DKV' (+ prometryn) (Istrochem); 'Zeazin Mix Extra' (+ metolachlor+ prometryn) (Istrochem) Discontinued names: 'Atratol' * (Ciba); 'Primatop' * (Ciba-Geigy); 'Cekuzina T' * (Cequisa); 'Griffex' * (Griffin); 'Hungazin' * (Budapest Chemical); 'Maizina' * (Sipcam); 'Zeapos' * (Sagrochem) mixtures: 'Primagram' * (+ metolachlor) (Novartis); 'Primatol' * (+ prometon) (Ciba-Geigy); 'Primextra' * (+ benoxacor+ metolachlor) (Europe) (Novartis); 'Contour' * (+ imazethapyr-ammonium) (Cyanamid); 'Vorox(i)Granulat 371' * (+ amitrole+ sebuthylazine) (Spiess)

ANALYSIS

Product analysis by glc with FID (CIPAC Handbook, 1980, 1A, 1106; FAO Specification (CP/61); AOAC Methods, 1995, 971.08). Residues determined by glc with ECD or FID (K. Ramsteiner et al., J. Assoc. Off. Anal. Chem., 1974, 57, 92; E. Knüsli, Anal. Methods Pestic. Plant Growth Regul., 1972, 6, 600; B. G. Tweedy & R. A. Kahrs, ibid., 1978, 10, 493). In drinking water, by gc with FID (AOAC Methods, 1995, 991.07); dealkylated atrazine can be determined by lc with u.v. detection (AOAC Methods, 1995, 992.14, 10.7.01). 

MAMMALIAN TOXICOLOGY

IARC ref. 53, 73  class 3  Oral Acute oral LD50 for rats 1869-3090 mg tech./kg, mice >1332-3992 mg/kg.  Skin and eye Acute percutaneous LD50 for rats >3100 mg/kg. Mild skin irritant; non-irritating to eyes (rabbits). Skin sensitiser in guinea pigs, but not in humans.  Inhalation LC50 (4 h) for rats >5.8 mg/l air.  NOEL (2 y) for rats 10 mg/kg diet (0.5 mg/kg daily), for dogs 150 mg/kg diet (3.75 mg/kg daily), for mice 10 mg/kg diet (1.4 mg/kg daily).  ADI 0.005 mg/kg b.w.  Water GV 2 mg/l (TDI 0.5 mg/kg b.w.).  Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) III  EC hazard (Xn; R48/22| R43| N; R50 R53) 

ECOTOXICOLOGY

Birds Acute oral LD50 varies from 940 mg/kg for bobwhite quail to >2000 mg/kg for mallard ducks and 4237 mg/kg for adult Japanese quail. Dietary LC50 (8 d) for Japanese quail (chicks) >5000, (adults) >1000 mg/kg.  Fish LC50 (96 h) for rainbow trout 4.5-11.0, bluegill sunfish 16, carp 76, catfish 7.6, guppies 4.3 mg/l.  Daphnia LC50 (24 h) 87 mg/l.  Algae EC50 (72 h) for Scenedesmus subspicatus 0.043 mg/l, (96 h) for Selenastrum capricornutum 0.13 mg/l.  Bees LD50 (oral) >97 mg/bee; (contact) >100 mg/bee.  Worms LC50 (14 d) for Eisenia foetida 78 mg/kg soil. 

ENVIRONMENTAL FATE

Animals In mammals, following oral administration, atrazine is rapidly and completely metabolised, primarily by oxidative dealkylation of the amino groups (R. Ikonen et al., Toxicol. Lett., 1988, 44, 109; Bull. Environ. Contam. Toxicol., 1989, 43, 199; Y. Deng et al., J. Agric. Food Chem., 1990, 38, 1411), and by reaction of the chlorine atom with endogenous thiols. Diaminochlorotriazine is the main primary metabolite, which readily conjugates with glutathione. More than 50% of the dose is eliminated in the urine and around 33% in the faeces within 24 h.  Plants In tolerant plants, atrazine is readily metabolised to hydroxyatrazine and amino acid conjugates, with further decomposition of hydroxyatrazine by degradation of the side-chains and hydrolysis of the resulting amino acids on the ring, together with evolution of CO2. In sensitive plants, unaltered atrazine accumulates, leading to chlorosis and death.  Soil/Environment Major metabolites under all conditions are desethylatrazine and hydroxyatrazine. Field DT50 16-77 d (median 41 d), the longer values being from cold or dry conditions. In natural waters, DT50 10-105 d (mean 55 d). DT50 under groundwater conditions 105->200 d, depending on test system (M. J. Wood et al. in: A Walker (Ed.), Pesticides in soils and water: current perspectives (BCPC Monograph 1991, 47, 175-182)). Kd 0.2-18 ml/g, Koc 39-173 ml/g; desalkylated metabolites had values similar to those of atrazine, while hydroxyatrazine was much more strongly adsorbed.