Online nonaqueous capillary electrophoresis–mass spectrometry method for the simultaneous screening of synthetic organic dyes

Abstract The increasing sophistication of handwriting forgery techniques highlights the need for reliable document authentication methods. This study reports an online nonaqueous capillary electrophoresis–mass spectrometry method for the simultaneous screening of several synthetic organic dyes, namely methylene blue, malachite green, crystal violet, methyl violet, Victoria blue basic oxide, and rhodamine B. All dyes were analyzed within 18 min under an electric field of 389 V/cm using a nonaqueous running buffer system (pH 4.5; 50 mM ammonium acetate and 850 mM acetic acid in 100% ethanol) and the single‐ion monitoring scan mode for signal enhancement. Ink organic dyes in documents handwritten using commercial red and blue ballpoint pens were extracted with ethanol from pieces of paper created by punching and successfully identified using the developed method to validate its applicability to real forensic samples and demonstrate its suitability for the rapid and effective forensic ink analysis coupled with document authentication.