Carbamazepine photodegradation

The described enhancement of carbamazepine photodegradation by Fe(III) oxide colloids could take place in deltas and estuaries, and our laboratory data suggest that the photochemical consequences of the chloride build-up could more than compensate the decrease of iron, due to colloid coagulation and sedimentation, which is usually observed in these environments. Interestingly, carbamazepine photodegradation on interaction between Fe(III) oxide colloids and chloride was more important than DOM-sensitized photolysis or direct photolysis, which are usually major photodegradation pathways for organic pollutants in surface waters [93]. 

As far as chloride is concerned, we have found that it enhances the photodegradation of carbamazepine (an antiepileptic drug that is found at elevated concentration in surface waters) by Fe(III) oxide colloids at pH >5 [93], Under more acidic conditions the elevated efficiency of "OH photoproduction by Fe(III) monomeric species, stable at acidic pH, and the scavenging of "OH by chloride would cause CT to inhibit photodegradation. In contrast, at neutral to basic pH the Fe(III) oxide colloids would photooxidize chloride to Cl2" faster than they directly degrade carbamazepine, and further reaction between Cl2" and carbamazepine would account for the enhancement of the degradation rate by chloride. Additionally, chloride is not able to scavenge OH in neutral to basic solution. 

Photodegradation in the solid state takes place only at the sample surface. The degradation rate is therefore dependent on factors that will influence the depth of light penetration, i.e., change the absorption and reflection at the surface (e.g., particle size, crystal modification, color, thickness of powder bed, and coating of the individual particles or the dosage form). Mefloquine, chloroquine, carbamazepine, and furosemide are examples of drug substances that show different decomposition rates dependent on their polymorphous modiflcation.P ... 

Chiron S, Minero C, Vione D (2006) Photodegradation processes of the antiepUeptic drug carbamazepine, relevant to estuarine waters. Environ Sci Technol 40 5977-5983... 

The identification of the products formed during the photodegradation with oxidation process of carbamazepine was performed based on molecular ions [M+H]+. The molecular ion at mJz = 267 amu can be attributed to the compounds 1-hydroxyac-ridine or 2-hydroxyacridine. The following structures were assigned to the other products 2-hydroxyphenol, 2-hydroxybenzoic acid, and 2-aminobenzoic acid. 

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