Fish farming is becoming a highly profitable economic activity and the rearing of fingerlings involves the practice of sex reversal for the production of species (male) using the hormone 17α-methyltestosterone (MT). This study analyzed the methodology for degradation of the hormone through solar and ultraviolet radiation using hydroxyapatite (HAP) as heterogeneous catalyst, synthesized by two different methods, with and without doping with nickel and copper. The results showed that MT hormone is degraded by ultraviolet or solar radiation, and accelerated in the presence of the HAP catalyst. In the presence of Fe (III) in the medium, the degradation rate of the hormone decreases. The method of HAP synthesis influences the degradation efficiency.Keywords: fish fry, hormone, fish-farming. Degradação de 17α-metiltestosterona com catalisador hidroxiapatita RESUMOA piscicultura tem se tornado uma atividade econômica altamente rentável e, para isto, a criação de alevinos adota a prática da reversão sexual para produção de espécies (macho) por meio do hormônio 17α-metiltestosterona (MT). Este trabalho desenvolveu metodologia para a degradação deste hormônio, por meio de radiação solar e ultravioleta utilizando catalisador heterogêneo hidroxiapatita (HAP) sintetizada por dois métodos diferentes, com e sem dopagem com níquel e cobre. Os resultados mostraram que o hormônio MT é degradado pela radiação ultravioleta ou solar, sendo acelerado na presença do catalisador HAP e a presença de Fe(III) no meio diminui a velocidade de degradação do hormônio. O método de síntese da HAP influencia na eficiência da degradação.Palavras-chave: alevinos, hormônio, piscicultura.

Contamination of waters by 17α-methyltestosterone (MT) has increased in recent years due to the increase in the fish farms production. This work describes the determination of the MT hormone by a new spectrophotometric method in the visible region, after the reaction with potassium nitroprusside with the generation of a compound having maximum absorbance at 400 nm. To understand the process of the compound formation, geometry optimizations were performed at MPW1PW91/6-311+G (2d,2p) level of theory and the calculations showing that the NO group of nitroprusside bonds to the carbon with double bond adjacent to the carbonyl of 17α-methyltestosterone. In this method, MT was determined at the concentration between 8.0 x 10 -8 and 2.7 x 10 -7 mol L -1 with a coefficient of determination of 0.9946. The relative standard deviation for the repeatability in nine replicates was 2.37% for [MT] = 1.50 x 10 -7 mol L -1 . Limit of detection (LOD) was calculated as 1.75 x 10 -8 mol L -1 and the limit of quantification (LOQ) was established as the lowest value of the linear concentration range (8.0 x 10 -8 mol L -1 ). This spectrophotometric method was suitable according to the analysis of analytical figures of merit, it has low cost and can be applied to samples of fish farm waters with portable spectrophotometers for in situ measurements, increasing the environmental control with rapid analysis.