Use of Isotope-Labeled Aflatoxins for LC-MS/MS Stable Isotope Dilution Analysis of Foods

Abstract

Aflatoxins are a group of very carcinogenic mycotoxins that can be found on a wide range of food commodities including nuts, cereals, and spices. In this study, the first LC-MS/MS stable isotope dilution assay (SIDA) for the determination of aflatoxins in foods was developed. The development of this method was enabled by easily accessible isotope-labeled (deuterated) aflatoxins B2 and G2, which were synthesized by catalytic deuteration of aflatoxin B1 and G1, purified, and well-characterized by NMR and MS. All four aflatoxins of interest (B1, B2, G1, and G2) were quantified in food samples by using these two labeled internal standards. The response factors (RF) of the linear calibrations were revealed to be matrix independent for labeled aflatoxin B2/aflatoxin B2 and labeled aflatoxin G2/aflatoxin G2. For labeled aflatoxin B 2/aflatoxin B 1 and labeled aflatoxin B2/aflatoxin G1 matrix-matched calibration was performed for the model matrices almonds and wheat flour, showing significant differences of the RFs. Limits of detection (LOD) were determined by applying a statistical approach in the presence of the two model matrices, yielding 0.31 microg/kg (aflatoxin B1), 0.09 microg/kg (aflatoxin B2), 0.38 microg/kg (aflatoxin G1), and 0.32 microg/kg (aflatoxin G2) for almonds (similar LODs were obtained for wheat flour). Recovery rates were between 90 and 105% for all analytes. Coefficients of variation (CV) of 12% (aflatoxin B1), 3.6% (aflatoxin B2), 14% (aflatoxin G1), and 4.8% (aflatoxin G2) were obtained from interassay studies. For further validation, a NIST standard reference food sample was analyzed for aflatoxins B1 and B2. The method was successfully applied to determine trace levels of aflatoxins in diverse food matrices such as peanuts, nuts, grains, and spices. Aflatoxin contents in these samples ranged from about 0.5 to 6 microg/kg.

Aflatoxins of type B and G affect porcine dendritic cell maturationin vitro

“…Indeed, when animals are fed feedstuffs contaminated at the upper limit of 10 mg/kg feed on a dry matter basis which is tolerated by the EU Feed legislation (2002), and considering the daily feed intake of piglets, total AF levels in the blood stream could reach $10 ng/ml. Although there are differing proportions of AFB 1 , AFB 2 , AFG 1 , and AFG 2 in Aspergillus-contaminated feed, aflatoxinogenic molds predominantly produce AFB 1 and to a lesser extent the other three AF in feed (Cervino et al, 2008;Joubrane et al, 2011;Li et al, 2009). Worldwide, occupational exposure to AF is alarming; a level of even $8 ng AFB 1 /ml in blood of swine 'workers' whose exposure was by the inhalation, oral, and/or dermal routes, has been reported (Viegas et al, 2013).…”

“…AF are classified into four types based on structure: AFB 1 , AFB 2 , AFG 1 , and AFG 2 (Figure 1), all of which are concomitantly present on Aspergillus-infested crops. Although the exact proportion of AFB 1 , -B 2 , -G 1 , and -G 2 in Aspergilluscontaminated feed and foods is unclear, these molds predominantly produce AFB 1 and to a lesser extent the other three AF in feed (Cervino et al, 2008;Joubrane et al, 2011;Li et al, 2009). AFB 1 is the most immune-disruptive aflatoxin, as a lower bioavailability and less toxic nature for AFB 2 , -G 1 , and -G 2 have been reported (Cusumano et al, 1990;Hoogenboom et al, 2001;Mehrzad et al, 2011).…”

Sampling Techniques for the Determination of Mycotoxins in Food Matrices

“…IAC cleanup is also used with isotope-labeled aflatoxins as internal standard for LC-MS/MS stable isotope dilution analysis of food (SIDA): 167 this approach has been proved to be very effective in overcoming the problem of matrix-dependent ionization suppression frequently encountered in LC-MS determination of mycotoxins in several food matrices. As the isotope-labeled standards have virtually the same chemical and physical properties as the respective analytes, no effects were found applying the IAC cleanup with, at the same time, obtaining better performances in the LC-MS determination.…”

Deoxynivalenol-mimic nanobody isolated from a naïve phage display nanobody library and its application in immunoassay

“…Therefore, it is necessary to develop rapid analytical and detection techniques for continued surveillance of foods and feedstuffs [1,2]. To date, a number of analytical techniques have been developed for chemical contaminant analysis, including chromatography [3], mass spectrometry [4], surface enhanced Raman scattering [5], NMR spectroscopy [6] and immunoassays [7]. Among these, immunoassays have been found widespread application as rapid screening techniques because of specificity, sensitivity, low cost, and suitability for high throughput screening.…”