13c15 don

All solvents were provided in analytical grade. Deionized water was supplied by a Purelab flex 2 (ELGA LabWater, Celle, Germany). Pure analytical standards (in acetonitrile) of DON, 15-Ac-DON, 3-Ac-DON, NIV, ZEN, TeA, AOH, AME and Tentoxin (TEN) (100 g mL ${}^{-1}$ ), DON-3G (50 g mL ${}^{-1}$ ) and ${}^{13}{C}_{15}$ -DON, ${}^{13}{C}_{15}$ -NIV, ${}^{13}{C}_{17}$ -3-Ac-DON and ${}^{13}{C}_{18}$ -ZEN (25 g mL ${}^{-1}$ ) were obtained from Romer Labs (Tulln, Austria). Solid standards of ALT, D3-ALT, D3-AOH, and D3-AME were purchased from HPC Standard GmbH (Cunnersdorf, Germany). From these solid standards, single analyte solutions were prepared for each native and isotopic labeled standard by dilution with methanol/water (60/40 v/v). Multicomponent solutions for constructing calibration curves of Fusarium toxins and Alternaria toxins were prepared by mixing of the single analyte standards and dilution with methanol/water (60/40 v/v); six calibration levels were prepared in the range of 10 to 1000 ng mL ${}^{-1}$ for each analyte. All solutions were stored at −20 ${}^{\circ }$ C in the dark.

LC grade acetonitrile, methanol, and water were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Mycotoxin stock solutions I, II, and III were obtained from Romer Labs (Union, MO, USA). Solution I contained 10 μg/mL each of aflatoxin B₁ (AFB1), aflatoxin B₂ (AFB2), aflatoxin G₁ (AFG1), aflatoxin G₂ (AFG2), and ochratoxin A (OTA) in methanol; Solution II contained 100 μg/mL each of fumonisin B₁ (FB1), fumonisin B₂ (FB2), and fumonisin B₃ (FB3) in acetonitrile–water (1 + 1, v/v); Solution III contained 100 μg/mL each of deoxynivalenol (DON), HT-2 toxin (HT-2), T-2 toxin (T-2), and zearalenone (ZON) in acetonitrile. The following carbon-13 (¹³C)-IS stock solutions were purchased from Romer Labs: ¹³C₁₇-AFB1 + B2 + G1 + G2 (0.5 μg/mL), ¹³C₂₀-OTA (10 μg/mL), ¹³C₃₄-FB1 (25 μg/mL), ¹³C₃₄-FB2 (10 μg/mL), ¹³C₃₄-FB3 (10 μg/mL), ¹³C₁₅-DON (25 μg/mL), ¹³C₂₂-HT-2 (25 μg/mL), ¹³C₂₄-T-2 (25 μg/mL), and ¹³C₁₈-ZON (25 μg/mL).Spiking solutions of ¹³C-IS and calibration standards were prepared according to a previously described protocol [22 (link)].