Commercially Available Blue Diode Laser Engraver Operating at 455 nm as an Affordable LD-REIMS Ionization Source

Lasers are commonly used for mass spectrometric applications to perform laser ablation-desorption and ionization; however, the use of visible light is not very common. Here, we report a commercially available visible light laser engraver operating at 455 nm as an ionization source, generating rich spectral profiles featuring predominantly lipid species, such as fatty acids and glycerophospholipids. Laser settings such as the speed of movement over the sample and laser power were tested, resulting in an optimum laser speed of 300 mm/min and a laser power of 30-50% for the analysis of fresh salmon tissue samples. Spectra generated were found to be similar to those produced by a conventional REIMS mechanism using Joule heating of the tissues, which was consolidated by comparative studies of the ion formation mechanism. The generated spectra show a slightly higher signal in the lower mass range, suggesting a higher degree of in-source fragmentation; however, no spectral feature was unique to either method. To test the suitability of the visible laser system to act as an REIMS-like profiling technique for food authenticity testing, we assessed the discrimination of Norwegian farmed salmon samples (n = 26) produced using conventional and organic farming methods.