More advanced courses, such as instrumental analysis, may consider analysis of inkjet ink, where explicit assignment of all ink components is not feasible, but the spectral features can nonetheless be used to achieve the forensic objectives. This work would be ideally suited for introducing students to advanced concepts in analytical chemistry, such as spectral database/library searches and chemometrics. Analysis of pen ink can also be carried out at the advanced level, but the questions to be addressed by students would be more complex than simple correlations of the mass and the chemical structure of dyes. For example, one may explore the reasons for the slight deviation of the measured isotopic distribution of peak 4 from the calculated isotopic distribution of copper (II) phthalocyanine (inset in Figure ). The following three possibilities should be considered: (i) inadequate ion statistics, (ii) partial in situ Cu 2+ reduction, giving rise to a mixture of singly charged ions with different number of protons, and (iii) deviation of the 65 Cu/ 63 Cu ratio in the dye product from the commonly accepted one (former NIST SRM 976). It is the latter possibility that is the most exciting as far as forensic applications are concerned (e.g., for the purposes of establishing sample provenance, etc.); however, the first two possibilities must be carefully evaluated prior to reaching any conclusions. Students may be asked if it is possible to distinguish variation of the 65 Cu/ 63 Cu ratio from that of C/ 12 C and 15 N/ 14 N with MS, a perfect exercise for exploring the concepts of mass defect, mass resolution, etc.