Using Solid-Phase Microextraction Coupled with Reactive Carbon Fiber Ionization-Mass Spectrometry for the Detection of Aflatoxin B1 from Complex Samples

Abstract

Aflatoxin B1 (AFB1) is a common mycotoxin present in agricultural and food products. Therefore, rapid screening methods must be developed for AFB1 detection with high sensitivity and good selectivity. In this study, we developed an analytical method based on the combination of solid-phase microextraction (SPME) with carbon fiber ionization (CFI)-mass spectrometry (MS) to detect the presence of trace AFB1 from complex samples. A pencil lead (type 2B, length: ~2.5 cm) with a sharp end (diameter: ~150 μm) was used as the SPME fiber and the ionization emitter in CFI-MS analysis. Owing to the graphite structure of the pencil lead, AFB1 can be trapped on the pencil lead through π–π interactions. After adsorbing AFB1, the pencil lead was directly introduced in a pipette tip (length: ~0.7 cm; tip inner diameter: ~0.6 mm), placed close (~1 mm) to the inlet of the mass spectrometer, and applied with a high voltage (−4.5 kV) for in situ AFB1 elution and CFI-MS analysis. A direct electric contact on the SPME-CFI setup was not required. Followed by the introduction of an elution solvent (10 μL) (acetonitrile/ethanol/deionized water, 2:2:1 (v/v/v)) to the pipette tip, electrospray ionization was generated from the elution solvent containing AFB1 for CFI-MS analysis. A reactive SPME-CFI-MS strategy was employed to further identify AFB1 and improve elution capacity using our approach. Butylamine was added to the elution solvent, which was then introduced to the pipette tip inserted with the SPME fiber. Butylamine-derivatized AFB1 was readily generated and appeared in the resultant SPME-CFI mass spectrum. The lowest detectable concentration against AFB1 using our approach was ~1.25 nM. Our method can distinguish AFB1 from AFG1 in a mixture and can be used for the detection of trace AFB1 in complex peanut extract samples.

Recent Insights into Sample Pretreatment Methods for Mycotoxins in Different Food Matrices: A Critical Review on Novel Materials

“…With the emergence of new technologies and novel materials, sample pretreatment methods are also developing. Table S2 [ 11 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , …”

“…However, their sensitivity and selectivity are relatively poor. Recently, the research focus of SPME is new fiber materials, such as graphene- and ILs-based adsorbents [ 55 , 95 ], and novel extraction forms, like in-pipe SPME (IT-SPME) [ 25 ]. Amde et al [ 95 ] synthesized [HMIM][PF6]@ZnO-NRs as the adsorbents of SPME to simply, quickly, and cost-effectively pretreat AFB1, B2, G1 and G2 in food products.…”

Utilizing a Metal Inlet Coiled with Copper Wire as the Ion Source for Ambient Ionization Mass Spectrometry

“…23−27,29−31,35−42 It has been demonstrated that AIMS can be simplified without the need to make any direct electric contact to the ionization emitter when a high voltage is applied to the orifice of the mass spectrometer. [23][24][25][26][27][29][30][31][35][36][37][38][39][40]42 This is because the high electric field provided in the mass spectrometer system is capable of inducing ionization through either electrospray 21,23,25−27,29−31,36−40 or corona discharge. [23][24][25][26]35,42 These approaches are called as field-induced 21 or contactless ionization methods.…”

“…[23][24][25][26]35,42 These approaches are called as field-induced 21 or contactless ionization methods. [23][24][25][26][27][29][30][31][35][36][37][38][39][40]42 For example, when a small piece of insulating fiber 23 or one piece of electric conductive material 25,26,39 was placed close to the metal inlet of the mass spectrometer, which was applied with a high voltage, volatiles or semivolatiles derived from the solid sample deposit on the fiber could be readily ionized and detected by the mass spectrometer. Corona discharge-like processes occur to initiate the ionization of volatiles and semivolatiles derived from the sample, although no direct electric contact was applied on the ionization emitter.…”

“…[23][24][25][26]35 The solid substrate functions like a counter electrode against the metal inlet of the mass spectrometer applied with a high voltage. Moreover, electrospray derived from a microdroplet deposited on an electric conductive, 25,26,39 dielectric, 36,37 or insulating fiber/ material 23 can also be generated when the droplet was placed close to the inlet of the mass spectrometer applied with a high voltage. The electric field provided by the mass spectrometer can induce the polarization of the sample droplet on the solid substrate, resulting in charge separation and formation of the Taylor cone.…”