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

Abstract

In this work, an ultra-performance liquid chromatography electrospray ionization (UPLC-ESI)-MS/MS methodology based on multiple 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.

Evaluation of HER2-specific peptide ligand for its employment as radiolabeled imaging probe

“…The collected samples were then characterized by using the simple, sensitive and efficient analytical technique LC-MS/MS, in multiple-reaction monitoring (MRM) mode. The MRM strategy provides a unique fragment ion that can be selectively monitored, also in a complex mixture 48 . In order to investigate the fragmentation pattern for biotinylated-A9, pilot LC-MS/MS-MRM experiments were also performed on the synthetic peptide.…”

“…The ESI source operating parameters were set as follows: positive ionization mode; capillary voltage 3.5 kV; source temperature 150 °C; desolvation temperature 600 °C; desolvation nitrogen gas flow rate 1000 L/h; cone gas 50 L/h; sampling cone voltage 40 V. The acquisitions were made in MRM/SRM (multiple reaction monitoring/selected reaction monitoring) 48 mode with a dwell time of 63 ms and a collision energy of 25 V. For the SRM mode the following transitions was monitored: biotinylated-A9 at m/z 615.0–477.2.…”

Rapid detection of water buffalo ricotta adulteration or contamination by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry

“…We previously reported, for wines and wheat matrices, the use of molecular mass codes resembling bar codes to made MALDI‐TOF spectra visualization simpler and more intuitive . Thus, a graphical representation of the peak lists was performed also for ricotta samples by converting the MALDI‐TOF spectral traces into simulated images (Fig.…”

“…Samples were suspended in 200 μL of 50 mM ammonium bicarbonate buffer in deionized water (pH 8.2). Aliquots of supernatants (20 μL containing 1 mg of total proteins) were then diluted 1:5 (v/v) in the same buffer and treated with 10 mM DTT (5 min at 95 °C) for cysteine reduction . Enzymatic hydrolyses were performed by adding TPCK‐treated trypsin (1 μg/μL) at an enzyme/substrate (E/S) ratio of 1:50 (w/w) and by incubating the mixtures at 37 °C for 5 min, 15 min, 30 min, 1 h and 16 h …”

“…Following trypsin digestion, samples were centrifuged (15800 g , 15 min) and diluted (1:50 in water containing 0.1% TFA). For matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) analysis, 1 μL of diluted samples was mixed with 1 μL of saturated α‐cyano‐4‐hydroxycinnamic acid matrix solution [10 mg/mL in acetonitrile/water (1:1, v/v), containing 0.1% TFA]. Thus, a droplet of the resulting mixture (1 μL) was placed on the MALDI‐TOF micro MX (Waters, Manchester, UK) target plate and dried at room temperature.…”