Mecanização e automação de metodologias de analise quimica : instrumentação para destilação seguida de detecção por (ICP OES) e para extração liquido-solido e detecção por espectrometria no visivel

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

In this work we present two equipment that were built from a common basis (an electronic interface): the first is a mechanized equipment capable of volatilizing compounds with boiling point up to 160°C and injecting them dírectly in to the torch of an inductively coupled plasma optical emission spectrometer. The equipment consists of a rotative tray that works as a crucible support containing the solutions of the analytic curve and samples, and a system for the introduction the crucible in an electrically heated decomposition/distillation furnace. The movements of the tray and of the system of introduction of samples are controlled by a microcomputer through an interface built in our laboratory. The interface also controls the heating of the decomposition furnace and the data acquisition by the spectrometer. A program written in Visual Basic controls the whole equipment. A module of data treatment was developed to work with the transient signals generated by the equipment. The described instrument was coupled to a ICP emission spectrometer Perkin Elmer (model OPTIMA) and it was tested for the distillation of boron fluoride. An analytic curve between 20 and 75 ng of boron with good linearity (R = 0.9997, n = 5) was obtained. The second equipment uses the same interface to mechanize liquid solid extractions, in which the extractant mixture (1-(2-pyridylazo)-2-2naphtol (PAN) and Naphthalene) is fixed in a glass or aluminum tube and can be automatically renewed. The system consists of a peristaltic pump to pump the reagents and the sample; six three-way TeflonTM solenoid valves for the flow control; a glass or aluminum tube (2 mm of internal diameter by 35 cm of length) working as a support of the solid phase; a spectrophometric detector and the interface adapted to switch the valves on and off and to read the answer of the detector. A microcomputer controls the whole system and makes the data acquisition and treatment through a program also developed in Visual Basic. With this system it was obtained an analytic curve in the range of 1 to 12 mg L of Zn (R = 0.9989, n=5). The estimated detection limit is 1.34 mg L of Zn, with a signal gain of about 40 times when 44.4 mL of an 8 mg L sample solution is eluted. Comparing to the conventional system, it is obtained a great economy of the reagents consuption (from 400 mg to 1.6 mg of naphthalene and from 12 mg to 0.05 mg of PAN for each extraction).

ASSUNTO(S)

quimica analitica espectrofotometria extração (quimica)

ACESSO AO ARTIGO

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