Volatilization is the process whereby a dissolved sample is vaporised. In atomic spectroscopy this is usually a two-step process. The analyte is turned into small droplets in a nebuliser which are entrained in a gas flow which is in turn volatilised in a high temperature flame in the case of AAS or volatilised in a gas plasma torch in the case of ICP spectroscopy.
Herbicides, also commonly known as weed killers, are substances used to control undesired plants, also known as weeds. Selective herbicides control specific weed species while leaving the desired crop relatively unharmed, while non-selective herbicides (sometimes called total weed killers kill plants indiscriminately. Due to herbicide resistance – a major concern in agriculture – a number of products combine herbicides with different means of action. Integrated pest management may use herbicides alongside other pest control methods.
Agricultural biotechnology, also known as agritech, is an area of agricultural science involving the use of scientific tools and techniques, including genetic engineering, molecular markers, molecular diagnostics, vaccines, and tissue culture, to modify living organisms: plants, animals, and microorganisms. Crop biotechnology is one aspect of agricultural biotechnology which has been greatly developed upon in recent times. Desired trait are exported from a particular species of Crop to an entirely different species. These transgene crops possess desirable characteristics in terms of flavor, color of flowers, growth rate, size of harvested products and resistance to diseases and pests.
Weed control is a type of pest control, which attempts to stop or reduce growth of weeds, especially noxious weeds, with the aim of reducing their competition with desired flora and fauna including domesticated plants and livestock, and in natural settings preventing non native species competing with native species.
Glyphosate is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSP). It is used to kill weeds, especially annual broadleaf weeds and grasses that compete with crops. Its herbicidal effectiveness was discovered by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market for agricultural use in 1974 under the trade name Roundup. Monsanto's last commercially relevant United States patent expired in 2000.
MCPA is a widely used phenoxy herbicide introduced in 1945. It selectively controls broad-leaf weeds in pasture and cereal crops. The mode of action of MCPA is as an auxin, which are growth hormones that naturally exist in plants.
Diquat is the ISO common name for an organic dication that, as a salt with counterions such as bromide or chloride is used as a contact herbicide that produces desiccation and defoliation. Diquat is no longer approved for use in the European Union, although its registration in many other countries including the USA is still valid.
Glufosinate is a naturally occurring broad-spectrum herbicide produced by several species of Streptomyces soil bacteria. Glufosinate is a non-selective, contact herbicide, with some systemic action. Plants may also metabolize bialaphos and phosalacine, other naturally occurring herbicides, directly into glufosinate. The compound irreversibly inhibits glutamine synthetase, an enzyme necessary for the production of glutamine and for ammonia detoxification, giving it antibacterial, antifungal and herbicidal properties. Application of glufosinate to plants leads to reduced glutamine and elevated ammonia levels in tissues, halting photosynthesis and resulting in plant death.
Pendimethalin is an herbicide of the dinitroaniline class used in premergence and postemergence applications to control annual grasses and certain broadleaf weeds. It inhibits cell division and cell elongation. Pendimethalin is listed in the K1-group according to the Herbicide Resistance Action Committee (HRAC) classification and is approved in Europe, North America, South America, Africa, Asia and Oceania for different crops including cereals, corn, soybeans, rice, potato, legumes, fruits, vegetables, nuts as well as lawns and ornamental plants.
Sulfentrazone is the ISO common name for an organic compound used as a broad-spectrum herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase. It was first marketed in the US in 1997 by FMC Corporation with the brand name Authority.
2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula Cl2C6H3OCH2CO2H. It is usually referred to by its ISO common name 2,4-D. It is a systemic herbicide that kills most broadleaf weeds by causing uncontrolled growth, but most grasses such as cereals, lawn turf, and grassland are relatively unaffected.
4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors are a class of herbicides that prevent growth in plants by blocking 4-Hydroxyphenylpyruvate dioxygenase, an enzyme in plants that breaks down the amino acid tyrosine into molecules that are then used by plants to create other molecules that plants need. This process of breakdown, or catabolism, and making new molecules from the results, or biosynthesis, is something all living things do. HPPD inhibitors were first brought to market in 1980, although their mechanism of action was not understood until the late 1990s. They were originally used primarily in Japan in rice production, but since the late 1990s have been used in Europe and North America for corn, soybeans, and cereals, and since the 2000s have become more important as weeds have become resistant to glyphosate and other herbicides. Genetically modified crops are under development that include resistance to HPPD inhibitors. There is a pharmaceutical drug on the market, nitisinone, that was originally under development as an herbicide as a member of this class, and is used to treat an orphan disease, type I tyrosinemia.
Aminocyclopyrachlor is a selective, low-toxicity herbicide that provides pre- and post-emergent control of broadleaf weeds, woody species, vines and grasses on several non-food use sites, such as rights of way, wildlife management areas, recreational areas, turf/lawns, golf courses and sod farms. It was conditionally registered as Imprelis by DuPont in August 2010, and first used in Fall 2010. The chemical is a systemic herbicide and acts by disrupting gene expression. This causes undifferentiated cell division and elongation.
Bifenox is the ISO common name for an organic compound used as an herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase which is necessary for chlorophyll synthesis.
The Enlist Weed Control System is an agricultural system that includes seeds for genetically modified crops that are resistant to Enlist and the Enlist herbicide; spraying the herbicide will kill weeds but not the resulting crop. The system was developed by Dow AgroSciences, part of Dow Chemical Company. In October 2014 the system was registered for restricted use in Illinois, Indiana, Iowa, Ohio, South Dakota and Wisconsin by the US Environmental Protection Agency. In 2013, the system was approved by Canada for the same uses.
Indaziflam is a preemergent herbicide especially for grass control in tree and bush crops.
Butafenacil is the ISO common name for an organic compound of the pyrimidinedione chemical class used as an herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase to control broadleaf and some grass weeds in crops including cereals and canola.
Aclonifen is a diphenyl ether herbicide which has been used in agriculture since the 1980s. Its mode of action has been uncertain, with evidence suggesting it might interfere with carotenoid biosynthesis or inhibit the enzyme protoporphyrinogen oxidase (PPO). Both mechanisms could result in the observed whole-plant effect of bleaching and the compound includes chemical features that are known to result in PPO effects, as seen with acifluorfen, for example. In 2020, further research revealed that aclonifen has a different and novel mode of action, targeting solanesyl diphosphate synthase which would also cause bleaching.
Tribenuron in the form of tribenuron-methyl is a sulfonylurea herbicide. Its mode of action is the inhibition of acetolactate synthase, group 2 of the Herbicide Resistance Action Committee's classification scheme.
Chlorsulfuron is an ALS inhibitor herbicide, and is a sulfonylurea compound. It was discovered by George Levitt in February 1976 while working at DuPont, which was the patent assignee.
