Abstract
An analytical procedure was developed to determine the content of metallic impurities in metal-free phthalocyanine (H2Pc) pigments. The technique involves dissolving the pigment in concentrated sulfuric acid, followed by oxidative degradation using hydrogen peroxide. Phthalimide was the only organic oxidation product. The remaining trace metals in the solution were determined using plasma atomic emission. The trace metals content in a commercial α polymorph of phthalocyanine pigment (ICI-Monolite Fast Blue GS) was monitored as a function of purification processes. Experiment showed that Monolite Fast Blue contains 2500 ppm Na; 350 ppm Ca, and 370 ppm Fe. Purification of this material by extraction with hot dimethyl-formamide gave β-H2Pc, which contained 300 ppm Na, 110 ppm Ca, and 310 ppm Fe. Sulfuric acid purification (acid pasting) reduced the content of non-transition elements, but in-increased the content of transition metals.These results were compared to the trace metal content in H2Pc pigment which were synthesized.
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