Adjuvants are defined as ingredients added to a mixture to aid or modify the action of an agrochemical, or to alter the physical characteristics of the mixture. Adjuvants have been used for as long as pesticides have been used. This made pesticides more effective and reduced handling challenges. For example, many pesticides wouldn’t disperse well in water. They plugged up nozzles, settled to the bottom of the spray tank, and were rain-washed.
Adjuvants are formulated to reduce these application problems by buffering, sticking, reducing foam, spreading, reducing evaporation, emulsifying, reducing drift, increasing compatibility, dispersing, and wetting.
Commercially available adjuvants in modern times are plenty with varying chemistries but often target a single effect. Selecting an adjuvant for the desired effect is also complicated as that will vary depending on the mode of action of the pesticide, nature of the target, method of application and climate conditions. Today, Nouryon launched a product called Adsee AMP40 that is an all-in-one adjuvant with several benefits.
Adsee AMP40 is an amphoteric surfactant that is zwitterionic in nature. What differentiates Adsee AMP40 from typical Betaines (also amphoteric) is the fact that when pH is low, Adsee AMP40 behaves as cationic and when pH is alkaline Adsee AMP40 has anionic character. There is also isoelectric point where the pH is neutral. This unique behavior makes Adsee AMP40 compatible/soluble over a wide range of pH and insensitive to water hardness. As with most amphoterics, Adsee AMP40 is mild (no skin/eye irritation) and readily biodegradable. As opposed to most amphoteric surfactants, Adsee AMP40 foams much less and the foam generated (15 mm immediately, 0 after 5 mins) is not persistent. A picture and list of typical physical/chemical properties of Adsee AMP40 is shown below.
Table 1: Typical properties of Adsee AMP40
Formulating a ‘high electrolyte’ pesticide, like Glyphosate or Dicamba often results in compatibility issues since typical surfactants-used as formulation aids and/or adjuvants-are not compatible in concentrated electrolytes. Due to the fact that Adsee AMP40 has a ‘true’ amphoteric behavior, it is highly compatible in these formulations. Furthermore, Adsee AMP40 can be also used as compatibilizer alone in formulations where compatibility is an issue (phase separation, low cloud point etc). Below, you can see a list of formulations in which Adsee AMP40 was tested and deemed compatible.
Amphoteric surfactants are also known to be good humectants. Adsee AMP40 is superior humectant when compared with other adjuvants typically used with Glyphosate. The graph below shows the result of an in-house method where the water uptake by the adjuvants are measured over time in a well-defined closed desiccator.
Graph 1: Water uptake vs time (Amphoteen 24: Betaine, APG: Alkylpolyglucoside)
Humectancy is an underrated functionality of adjuvants. There seems to be consensus that a humectant can possibly enhance the efficacy of AIs where dissolution of an active is achieved by providing moisture taken/retained by atmosphere. However, if dissolution is not necessary/needed, humectancy is often not considered by formulators. We have shown, by using a QCM-D technique, that an effective humectant can soften/hydrate the hydrophobic barrier of target surfaces thus enhancing the penetration of a pesticide. Quartz Crystal Microbalance with Dissipation (QCM-D) method is a surface sensitive technique to probe the interaction of adjuvants in order to a model surface consisting of a cuticula wax in order to further understand their mode of action.
We screened Adsee AMP40 using the QCM-D method and evaluated its adsorption profile towards a sensor coated with a model leaf wax cuticula was assessed. Parameters such as adsorbed adjuvant mass, adsorption kinetics and viscoelastic changes of the wax layer were extracted. Graph 2 shows the changes in elastic modules of the wax layer during adsorption of Adsee AMP40. An increase (approx 70%) in the elastic modulus of the wax layer was observed during the adsorption, suggesting soften/hydrating the wax layer and ease penetration of active ingredient which can increase the efficacy of pesticide applied.
Graph 2: Changes in elastic modules of the wax layer during adsorption of Adsee AMP40
Additionally, we have observed that Adsee AMP40 can indeed improve the efficacy in variety of cases, as suggested by QCM-D method. Below (Graph 3) is the result of one of the several fungicide trials we have performed over 3 years period.
Trials were performed at ICAR National Research Centre for Grapes, Pune, INDIA. Detailed results can be shared upon request. In this particular case, Azoxytrobin 250 g/L SC was used as the fungicide to control powdery mildew at 0.02% (w/v) and adjuvants were selected from typical benchmarks and applied as tank-mix at 0.03% (w/v). Results confirm that Adsee AMP40 is the best performing adjuvant among several benchmarks, such as NPE and a silicone based super spreader. Further tests by using Tebuconazole, Metrafenone, Dimethomorph and Thiophanate-methyl support the same conclusion; Adsee AMP40 shows superior control over early and late blight as well as powdery mildew. Observation parameters like chlorosis, necrosis, wilting, scorching, hyponasty and epinasty for phytotoxicity were also taken and noted no phytotoxicity when Adsee AMP40 was used.
Graph 3: Azoxytrobin results
Another interesting area of application for Adsee AMP40 is in herbicide use. We have performed Glyphosate as well as Glufosinate trials. Results of Glyphosate trials showed that Adsee AMP40 can be used as alternative and sustainable adjuvant since results were on par with commercial benchmarks. On the other hand, we have observed that Adsee AMP40 gave a faster knock-down effect at much lower concentration when used in Glufosinate trails. The trials were performed in Indonesia and the results can be seen in Graph 4. Adsee AMP40 was applied as In-can in these trials.
Graph 4: Glufosinate NH4 results at 2L/ha
As a result, we have tested the attributes of Adsee AMP40 as a penetrant, humectant and compatibilizer and shown it has superior performance compared to commercial benchmarks. As there are hundreds of adjuvants that enhance efficacy of a given pesticide, what differentiates Adsee AMP40 is its benign toxic profile which will help customers to reach their sustainability targets. Please contact us for further information and samples requests at https://surfacechemistry.nouryon.com/markets/agrochemicals/adsee-amp-40