Rapid Determination of Oxalic,Malic and Citric Acids in Tobacco by Near Infrared Spectroscopy

In order to fast analyze the oxalic,malic and citric acids in tobacco,the near infrared(NIR) spectra of 113 tobacco samples were measured with near infrared diffusive spectroscopy and the contents of oxalic,malic and citric acids in the samples were determined by GC.The models for predicting the acids' contents in tobacco were established by the spectral data in the range of 4246.7 to 7502.1cm^-1 through preprocessing by constant offset elimination,min-max normalization and first derivative and multiplicative scattering correction(MSC),respectively and regressed by partial least square(PLS).The models went through external validation as well.The results showed that the average relative deviations between the predicted and found values of the three acids were less than 5% with the RSDs of <4%.It suggested that the models were applicable to rapid determination of the three acids in batches of tobacco samples.