Dipping probe electrospray ionization/mass spectrometry for direct on-site and low-invasive food analysis

• Published in: Food chemistry 2018-09, Vol.260, p.53-60
• Main Authors: Usmanov, Dilshadbek T., Mandal, Mridul K., Hiraoka, Kenzo, Ninomiya, Satoshi, Wada, Hiroshi, Matsumura, Masaya, Sanada-Morimura, Sachiyo, Nonami, Hiroshi, Yamabe, Shinichi
• Format: Article
• Language: English
• Subjects: Dairy food; DFT calculations; Dipping PESI; Lactose intolerance; Point-of-care analysis; Probe electrospray ionization; Remote sampling
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2018.04.003

•Food analysis by dipping probe electrospray ionization.•Low-invasive food analysis with high detection sensitivity.•Remote-sampling mass spectrometry. Rapid, direct, on-site and noninvasive food analysis is strongly needed for quality control of food. To satisfy this demand, the technique of dipping probe electrospray ionization/mass spectrometry (dPESI/MS) was developed. The sample surface was pricked with a fine acupuncture needle and a sample of ∼200 pL was captured at the needle tip. After drying the sample, the needle tip was dipped into the solvent for ∼50 ms and was moved upward. A high-voltage was applied to the needle to generate electrospray when the needle reached the highest position, and mass spectra were measured with a time-of-flight mass spectrometer. For evaluation of the method, the technique was used to analyze foods such as vegetables, salmon flesh, cow’s milk, yogurt, and soy-bean milk. The detected major ions for cow’s milk and yogurt were [(Lac)n + Ca]2+ with n = 1–6 (where (Lac) is lactose), indicating that Ca2+ is tightly bound by Lac molecules.