| UV laser desorption mass spectrometry (LDMS) has proven to be a viable technique for the detection and characterization of ink dyes directly from a paper substrate. Advantages to using LDMS include high sensitivity and selectivity for detecting dyes, minimal sample preparation, short analysis time, and minimal sample destruction. The most important aspect of the technique in terms of questioned document examination is that written lines of a single pen stroke can be analyzed directly from paper; hence no extraction step is necessary.; Thin-layer chromatography (TLC) is a technique that compliments UV LDMS in identifying ink dyes. TLC is a simple analytical technique that provides information on the color and the number of dyes present in the ink. TLC was indirectly coupled with LDMS. Direct coupling of TLC eliminates the extraction step and preliminary experiments showed the method has potential when coupled with LDMS.; The use of photochemistry with subsequent LDMS analysis has been successfully utilized to characterize ink dyes. Generally, structural information for characterizing the dyes used in this research is limited in LDMS. When dyes are photochernically induced to react they can form photodegradation products and can be detected by LDMS and are structure dependent, hence, they can be used to characterize the dye. |
