Mass Spectral Confirmation of Aflatoxins

Abstract

Two methods for mass spectral (MS) confirmation of aflatoxins in agricultural products and in physiological fluids are described. In the first method, electron ionization (EI) mass spectra are obtained following isolation by thin layer chromatography (TLC) and compared with available reference mass spectra to provide structural confirmation. Extensive sample cleanup is required for confirmation at the 10—1000 ppb level and minimum sample size is 10—50 ng aflatoxin isolated by TLC. The second method restricts the MS scanning to particular ions which are characteristic of the suspected aflatoxins and requires spectrometer resolution above 5000. The latter method, called high resolution selected ion monitoring (HRSIM), has a sensitivity below 0.0001 μg for aflatoxin B1 and makes possible direct analysis of complex mixtures. Employing HRSIM analysis on complex mixtures lowers the detection limit for aflatoxins M1 and B1 by 100-fold or more below the limit for highly purified samples. We attribute this dramatic sensitivity enhancement to a reduction in surface bonding between the aflatoxins and the glass sample containers used to introduce the samples. The HRSIM is generally applicable to compounds that cannot be separated by gas chromatography prior to MS analysis.

Distribution of Aflatoxin in Pistachios. 3. Distribution in Pistachio Process Streams

“…Thus, substantially all of the analytic error is assigned to the use of the affinity column. In testing the HPLC column it was noted that aflatoxin would adsorb on newly purchased glassware (Haddon et al, 1977). This problem was solved by silination (surface deactivation) of the volumetric flasks using Sigmacote (Sigma Chemical Co., St. Louis, MO; instructions available from Sigma).…”

A Review: Sample Preparation and Chromatographic Technologies for Detection of Aflatoxins in Foods

“…The procedure required a large on plate mass of aflatoxin B 1 , yet it did not work for other aflatoxins. Attempts to couple TLC with mass spectrometry for more specific identification were reported by Haddon et al [181,182], Brumley et al [183], Park et al [184] and Tripathi et al [185]. However, aflatoxins were unable to be directly analyzed by MS requiring extensive clean-up steps to remove aflatoxins from the plate and purified prior to MS analysis.…”

“…Initially, aflatoxin confirmation was performed by bioassays [ 248 ], which was an indirect and time-consuming approach and soon replaced by techniques based on physicochemical properties of aflatoxins (e.g., 2D-TLC, chemical derivatization and FLD) [ 211 , 249 , 250 ]. When MS became available, negative chemical ionization MS- [ 182 ], gas chromatography (GC)–MS- [ 251 ] and eventually, LC-MS-based confirmation was adopted [ 136 , 252 ] by private and government laboratories.…”

Confirmation of aflatoxins B1 and B2 in peanuts by gas chromatography/mass spectrometry/selected ion monitoring

“…This method employs a two-dimensional TLC cleanup step. Previously, Haddon et al (1977) reported electron ionization analysis of aflatoxins Bx and Mx at resolution above 5000 in samples introduced through the direct insertion probe.…”