Desenvolvimento de sistemas automáticos empregando flow-batch e multicomutação para análise fotométrica de amostras de interesse farmacêutico e agronômico

Abstract

In this work is proposed the development of automated procedures with sufficient sensitivity for photometric determination of aluminium in water used for hemodialysis treatment and nickel in digested plants. ANVISA established that the maximum allowable concentration is 10 μg L-1 Al (III) in solution for hemodialysis. The matrix has a high concentration of salts such as Ca, Mg, K and about 30% (w/v) NaCl, thus causing difficult to determine the metal. This drawback was overcome in this work by employing a multicommuted flow-batch system and a LED photometer equipped with a flow cell with optical path length of 200 mm. There was no prior preparation of the sample and the method was based on the reaction of Al (III) with chromeazurol S, producing a compound of pink color, which absorbed electromagnetic radiation with maximum at 530 nm. After optimization of the parameters, the proposed procedure showed a linear response range between 5.0 and 125 μg L-1; a detection limit of 0.6 μg L-1; consumption of 12 mg and 85 mg S chromeazurol and hexamine per determination, respectively; a sampling frequency of 70 determination per hour and a waste generation of 1.6 mL per determination. To evaluate the accuracy of the methodology was employed standard addition and the results showed a recovery in the range 90-113 %. The analytical module for the determination of nickel was developed to implement the multicommutation process with the use of solenoid minipump as fluid propelling device. The procedure was developed based on the reaction with Ni (II) with dimethylglyoxime in alkaline medium, producing a compound which showed maximum absorption at 490 nm. After optimization of the control parameters, the proposed procedure showed a linear response in the range from 0.13 to 2.0 mg L-1; detection limit of 0.04 mg L-1; 2.40 mg consumption of trietanolamine; 2.00 mg of potassium persulfate; and 0.40 mg of dimethylglyoxime, all for determination.