Abstract:
Administering adsorbates such as activated charcoal can treat acute poisoning from
chemicals and pesticides. It has been suggested that activated charcoal is an effective
antidote for virtually all organic and inorganic compounds.
The aim of this study was to characterise the adsorbate-adsorbent interactions.
Adsorbents used were chitosan, activated charcoal, silica and humic acids.
Adsorbates used were paracetamol, prazosin hydrochloride, cimetidine, fluoxetine
hydrochloride, conjugated estrogens and amitraz. Amitraz is widely used in South
Africa and amitraz adsorption studies were performed to gain an insight into effective
pesticide waste and dip vat management.
This study used different solution properties to determine their influence on the
hydrolysis of amitraz. Amitraz hydrolysis could be described as a pseudo-first order
rate process and a type ABCD pH rate profile. Hydrolysis increased with temperature
and was fastest at low pH, slowest at neutral to slightly alkaline pH, and slightly
increased above pH 10. Hydrolysis was fastest in water, slower in propylene glycol
and ethanol solutions and slowest in DMSO mixtures. In surfactant solutions, anionic
micelles enhanced and cationic micelles retarded the hydrolysis rate. The half-live of
amitraz was reduced from 27 days for the aqueous suspension in buffer pH 5.8
containing 0.5 % sodium lauryl sulphate to 8 hours and 12 hours when 1 % potassium
oxihumate was added.
Adsorbents were mixed with amitraz solution for 24 hours at 31°C. Study results
proved that coarse activated charcoal powder adsorbed more than the other adsorbents
used and can be used to treat amitraz poisoning or to manage spills. A study was also
done to investigate amitraz adsorption on pears and oranges. Fruit soaked in amitraz
solution for 5 minutes and left to dry for 24 hours, were washed in solutions of
distilled water, sodium lauryl sulphate, cetrimide and Tween 80.
Four crystal forms of amitraz were identified by their crystal morphology, XRPD
patterns, aqueous solubility and thermal properties. Form C was the most stable with
t½ of 136 days. Forms B and D were least stable with t½ of 28 days. Stability
correlated with solubility differences. The addition of sodium lauryl sulphate
increased hydrolysis (t½ = 17 hours) and no difference in stability of crystal forms in
anionic surfactant solutions occurred.
Adsorption activity of activated charcoal and chitosan were done on OTC drugs. The
official dissolution media, simulated gastric and intestinal fluids were used.
Cimetidine did not adsorb onto activated charcoal or chitosan tablets. Adsorption of
paracetamol was minimal. Prazosin hydrochloride and fluoxetine hydrochloride were
strongly adsorbed by activated charcoal with no adsorption onto chitosan. Conjugated
estrogens were adsorbed by chitosan and not by activated charcoal.
Anionic surfactants such as sodium lauryl sulphate can potentially be used for
cleaning up amitraz, as it demonstrated increased solubilisation and hydrolysis of
amitraz. Activated charcoal can be used to treat many drug poisonings and overdoses.
