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Department of Chemistry, College of science, University of Salahaddin,Arbil, Iraq; and Department of Microbiology, College of Education, University of Salahaddin, Arbil, Iraq.

ABSTRACT

The use of molecular emission cavity analysis in determining total nitrogen in tobacco leaves using catalytic acid digestion was studied. The investigation involved 11 commercial kinds of tobacco. Two different catalysts (selenium, and titanium dioxide with copper sulphate) in concentrated sulphuric acid at a programmed temperature were used. A small portion (0-5 ml) of the acid digest solution was diluted to a total volume of 1.5 ml with distilled water followed by the addition of solid KOH. The white emission of ammonia gas released from the acid digest was recorded at 500 nm as d function of time in 20 sec There was no significant difference (at lo% or 5% confidence limit) between the two catalytic) methods of digestion when the titration method was used. On the other hand when MECA technique was employed,  there was a significant difference which was attributed to its high sensitivity and to the different catalysts used. This shows that MECA can be applied successfully an a1ternaitive method to the existing methods which are commonly used in quality control work.