Formulation
| October 22, 2026
Stability and Decomposition Study of Ethoprophos in Emulsifiable Concentrates during Storage.
Stability and Decomposition Study of Ethoprophos in Emulsifiable Concentrates during Storage.
AUTHORS | Parra, J.; Quirós, J.; Barrantes, D. Formulaciones Químicas S.A.: Puntarenas, Costa Rica.
ABSTRACT
The present study evaluated the chemical stability of ethoprophos, formulated as a 72% w/v
emulsifiable concentrate, under different preparation and storage conditions, with the aim of
determining the conditions most favorable for maintaining the concentration of the active ingredient.
Four experimental solutions with different compositions and pH values were prepared, incorporating
an organosilicone adjuvant, citric acid, or a KOH solution, in addition to an additive-free control, and
were stored under ambient and accelerated conditions of 40 °C and 75% relative humidity, following
the CIPAC MT 46.4 procedure. Ethoprophos concentration was determined by gas chromatography
with a flame ionization detector (FID) on days 0, 1, 4, 8, and 15. The results showed a progressive
decrease in the active ingredient in all solutions, although at different rates depending on the pH and
composition of the mixture. The highest relative stability was observed under conditions close to
neutral pH, whereas alkaline media exhibited more rapid degradation, mainly due to base-catalyzed
hydrolysis; likewise, acidic conditions favored acid-catalyzed hydrolysis. Consequently, maintaining
ethoprophos under conditions close to pH 6–7 and avoiding additives or extreme chemical conditions
was found to favor its stability and reduce active ingredient degradation during emulsion preparation
and storage.
INTRODUCTION
Ethoprophos (CAS: 13194-48-4) is
an organodithiophosphorus insecticide
belonging to the organophosphate group
and is commonly formulated as an
emulsifiable concentrate (EC). It is used
primarily for the control of soil insects,
including symphylans. The chemical
stability of this type of molecule is highly
dependent on the pH of the medium and
the presence of adjuvants, fertilizers, and
other components that may modify the
chemical environment of the emulsion
during preparation and the period prior to
application.
Organophosphates are known to be
susceptible to acid- and base-catalyzed
hydrolysis processes, arising from the
electrophilic nature of the phosphorus
atom and the oxygen atoms of the
phosphate group. Therefore, variations in
pH, as well as the presence of complexing
agents, organic salts, or strong bases, can
accelerate the degradation of the active
ingredient and affect its agronomic
efficacy.