Raman spectroscopy in forensic analysis of blue gel inks on paper

Abstract

Raman spectra of different brands of blue gel inks on A4 sheet were measured at uniform condition for all the samples. Spectral results were subjected to background correction and smoothening. The pre-processed spectral data were used for carrying out PCA (Principal Compound Analysis). Through the combination of Raman Spectroscopy (RS), Pearson's correlation calculation and statistical method (PCA) we were able to differentiate among very similar ink types in documents. The correlation value of (E,U)=0.995 and (D,U)=0.994 for pair wise combination of RS and similarities in loading plots in terms of PCA helped in identifying correctly the unknown brand of blue gel pen. Thus we demonstrate the effectiveness of Raman spectroscopy is identifying the usage of different inks in a document which could possibly be taken forward for forensic applications in the Indian context also.