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.