A validated method to quantify folic acid in wheat flour samples using liquid chromatography: tandem mass spectrometry

In order to monitor the fortification level of folic acid (vitamin B9) in wheat flour samples, we developed and validated a simple and fast analytical method using the liquid chromatography with tandem triple quadrupole mass spectrometry (LC-MS/MS) technique. The compound was ionized by an electrospray source in positive mode. The tandem MS/MS instrument was set in MRM (Multiple Reaction Monitoring) mode to detect two m/z transitions used for quantitation and confirmation purposes. A total of 83 samples were prepared to validate the method according to the regulatory guidelines from the Commission Decision 2002/657/EC for food residues analysis. The method performance was evaluated in regards to linearity, accuracy, precision, sensitivity, and uncertainty. The statistical analysis of the results showed a correlation coefficient (r²) of 1.000 within the concentration range of 1.0 to 50 µg L-1. The method reproducibility of 5.6% was obtained by calculating the standard deviation sum of the intra-day and inter-day analysis at a fortification level limit of 1.50 µg g-1 of folic acid. In addition, ten blank spiked samples at the fortification level limit were extracted and analyzed with an accuracy of 85% and a precision of 3% (coefficient of variation). The method sensitivity was expressed in decision limit (CCα) of 0.06 µg g-1 and detection capability (CCβ) of 0.11 µg g-1. The total measurement uncertainty method calculated was + 0.11 µg g-1. Different brands of Brazilian wheat flour were evaluated and reported.