Ultra-high performance liquid chromatography tandem mass spectrometry for the detection of durum wheat contamination or adulteration

In this work, an ultra-performance liquid chromatography electrospray ionization (UPLC-ESI)-MS/MS methodology based onmultiple reaction monitoring (MRM) for the selective and sensitive detection and quantification of durum wheat adulteration has been developed and fully validated. The targeted analysis was performed by monitoring specific transitions at m/z 543.7>657.4 and m/z 543.7>299.2 of a species-specific marker derived from a tryptic peptide of puroindoline a (Pin-a), a cysteine-rich protein selectively present only in common wheat. In addition, two transitions at m/z 500.4>725.4 and m/z 500.4>561.9 of a reference peptide belonging to purothionin A-1, present in both species, were also monitored. The calibration curves obtained on binary mixtures with known percentages of common/durum wheat flours showed linearity (coefficient of regression, r ≥ 0.99) over concentrations that ranged between 80 and 1%. The limit of detection (LOD) and limit of quantification (LOQ) for the Pin-a marker in wheat flours were 0.01 and 0.03%, respectively. The identified Pin-a marker was also found to be highly diagnostic for the quantification of common wheat in raw materials (kernels) and processed products (pasta), thus offering new opportunities to assess food authenticity.