Determination of phthalic acid by pyrolysis GC.

Abstract

Phthalic acid was determined with good precision by Curie point pyrolysis GC using a mixture of Ni powder and sodium carbonate (10 : 7). The recommended procedure is as follows: Phthalic acid is solved in ethanol(15×10^-7 M) and is added to 30 mg of the mixed powder(Ni : Na₂CO₃·10H₂0 =10 : 7) placed on pyro foil by use of a microlitre syringe and are dried on hot plate (100°C). Pyrolyser were carried out by using a gas chromatograph fitted with a Curie point pyrolysis unit (pyrolysis foil was maintained at 590°C for 4s). The decomposition products were separated on fused silica capillary column(50m×0.2 mm i.d. CBP-1). In this method, the peak of phthalic anhydride, which appears in conventional PGC-method, does not appear. As the result, phthalic acid could be rapidly determined in the proposed PGC-method with a low column temperature such as 70°C with good precision. No detectable interference was observed such as allyl alcohol, ethylene glycol and octyl alcohol for the determination of phthalic acid. The calibration curve for phthalic acid constructed by using the peak area method was linear over the concentration range of 1×10^-75×10^-7 M. The relative standard deviation(n=10) was 2.4%.