Nanomodified Screen-Printed Electrode for direct determination of Aflatoxin B1 in malted barley samples

Journal Pre-proof Nanomodified Screen-Printed Electrode for direct determination of Aflatoxin B1 in malted barley samples ´ Ava Gevaerd, Craig E. Banks, Marcio F. Bergamini, Luiz H. Marcolino-Junior

PII:

S0925-4005(19)31746-0

DOI:

https://doi.org/10.1016/j.snb.2019.127547

Reference:

SNB 127547

To appear in:

Sensors and Actuators: B. Chemical

Received Date:

7 August 2019

Revised Date:

4 December 2019

Accepted Date:

5 December 2019

Please cite this article as: Gevaerd A, Banks CE, Bergamini MF, Marcolino-Junior LH, Nanomodified Screen-Printed Electrode for direct determination of Aflatoxin B1 in malted barley samples, Sensors and Actuators: B. Chemical (2019), doi: https://doi.org/10.1016/j.snb.2019.127547

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Nanomodified Screen-Printed Electrode for direct determination of Aflatoxin B1 in malted barley samples

Ava Gevaerd ¹, Craig E. Banks ², Márcio F. Bergamini ¹, Luiz H. Marcolino-Junior¹,*

Federal do Paraná (UFPR), CEP 81.531-980, Curitiba, PR, Brazil

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¹Laboratório de Sensores Eletroquímicos (LabSensE), Departamento de Química, Universidade

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²Faculty of Science and Engineering, Manchester Metropolitan University, Chester Street,

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author: [email protected] (L. H. Marcolino-Junior)

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*Corresponding

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Manchester M1 5GD, United Kingdom

RESEARCH HIGHLIGHTS

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 Facile synthesis of gold nanoparticles and graphene quantum dots nanocomposite;  Non-biological alternative for Aflatoxin B1 (AFB1) voltammetric determination;  High electrocatalytic effect on AFB1 oxidation and good analytical performance;  Low matrix effect for malted barley samples at nanomolar concentration levels. 1

ABSTRACT The present work describes a facile synthesis of a nanocomposite based on gold nanoparticles (NPAu) and graphene quantum dots (GQD) and its use as an electrode modifier for a nonbiological alternative of Aflatoxin B1 (AFB1) voltammetric determination. TEM and SEM

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techniques showed a uniform and well-distributed dispersion of gold nanoparticles (19 ± 6 nm of average size) and GQD, which was used as a reducing and stabilizing particle

formation. Modified screen-printed electrode (NPAuGQD-SPE) was characterized by

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electrochemical experiments, as linear voltammetry and electrochemical impedance

spectroscopy. A significative electrocatalytic effect was observed towards AFB1 oxidation

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using the proposed device, shifting the peak potential to less positive values and improving the voltammetric response. EIS experiments showed lower RCT values for the modified

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electrodes, calculated as 117 Ω, 14.9 kΩ, and 40.3 kΩ for NPAuGQD-SPE, GQD-SPE, and SPE, respectively. Under optimized conditions, an analytical curve with linear region

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of 1.0 to 50.0 nmol L-1 was obtained, reaching detection and quantification limits of 0.47 and 1.5 nmol L-1, respectively. Samples of malted barley were fortified based on the

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maximum residue limit (MRL) allowed by Brazilian legislation, and recoveries in the

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range of 76 to 103% were obtained, indicating that there is no significant matrix effect, considering the low concentration values used and simple sample treatment.

KEYWORDS

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Mycotoxin; Screen-Printed Electrode; Gold Nanoparticles; Graphene Quantum Dots;

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Analytical Device

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1. INTRODUCTION Mycotoxins are a toxic group of secondary metabolites produced by a few fungal species and are a potentially infesting at all stages of production, processing, and storage, being considered difficult-to-control natural contaminants in food. The principal genera of mycotoxin-producing fungi are Penicillium, Aspergillus and Fusarium, and mycotoxins may remain even after fungal destruction. [1–4] Aflatoxins are more widely studied mycotoxins. Chemically, they are substituted coumarins, among which the most

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important are aflatoxin B1 (AFB1). AFB1 is considered the most carcinogenic natural agent known [5], and the most crucial mycotoxin in Brazil, being able to infect and

reproduce on cereal-derived production both in the field and during harvest and storage.

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[6] Exposure to low concentrations in the long term has been associated with liver

diseases such as cancer, cirrhosis, hepatitis, and jaundice, both in humans and in animals,

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being considered as carcinogenic, genotoxic and immunosuppressive substances. [5]

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Contamination by mycotoxins poses a serious health problem for humans and animals as well as an economic obstacle. Thus, legislation has been adopted to protect consumers against the harmful effects of mycotoxins on raw and processed foods and

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even on feeds for slaughter and pet animals. The Brazilian legislation establishes the maximum residues limits (MRL) for the presence of diverse groups of mycotoxins in

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different crops and foods [7]. Therefore, rapid and low-cost testing, based on highly

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sensitive techniques, together with technologies, can be innovative solutions to meet the needs involved in such monitoring, thus ensuring safety, quality, and analytical requirements. There are different analytical approaches for the determination of aflatoxins in food samples based mainly on separation methods (e.g., chromatographic techniques) and immunoassay tests like ELISA [8,9]. In general, electrochemical approaches described in the literature are biosensors based [10–12], specially

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immunosensors, which are simple and easy-to-use, but they have some drawbacks related to the instability and degradation of recognition biomolecule providing false positives or false negatives results. The use of new analytical systems inspired by nanotechnology is a strategy that offers several advantages to electrochemical sensors, particularly in AFB1 detection demand, replacing commonly used biological recognition systems described above. In addition to high stability, reproducibility, and simplicity, the high surface area plays an

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essential role in the improvement in the mass transport process. Also, surface atoms can be more reactive and efficient to electron transfer between the interest group and the electrode surface, providing an electrocatalytic effect on redox reactions, as well as

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increasing device selectivity. [13,14] Given the large family of carbon nanomaterials,

graphene quantum dots (GQDs) have received focus, even with their recent discovery,

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considering their easy acquisition from simple synthesis methods and widely available

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carbon sources, with high surface area, enhanced electrocatalytic activity, and other characteristics due to quantum confinement phenomena and edge effects, which can be exploited in the construction of electrochemical sensors, as well discussed in a recent

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review by Asadin et al. [15]. With a diameter below 20 nm and the presence of conjugated π-π bonds mixed with oxygenated surface groups, usually remaining at the

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edges, they have high water solubility and the possibility of chemical functionalization,

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reaching the full application potential of GQDs. [16,17] Thus, GQDs-based nanocomposites have been fabricated, which could integrate properties of GQDs and functional components, as metallic nanoparticles, for example, for many applications. [18–21] Indeed, gold nanoparticles (NPAu) receive a significant prominence in this context. Some of the attributes that make its use as a model system in the development of

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sensors are as they can confer the direct electron transfer between the analyte and the electrode base, facilitating the electrode reaction. [22,23] They are also advantageous for electrochemical sensors because of the known characteristics of NPAu, such as high ratio area/volume and high interfacial energy, increase the electroactive surface area. [24] In this work, we describe the use of Screen-Printed Electrodes, widely platform used to fabricate disposable and economical electrochemical sensors, modified by a composite between graphene quantum dots and gold nanoparticles as a direct sensor used

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as an alternative to immunosensors commonly used for determination of AFB1 in malted barley samples.

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2. MATERIAL AND METHODS 2.1. Chemical Reagent

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All reagents used in this study were of analytical grade and obtained from Sigma

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Aldrich. The solutions were prepared with water purified using a Milli-Q system manufactured by Millipore (Bedford, MA, USA). An AFB1 stock solution of 1.0 mM dissolved in methanol was prepared, and less concentrated solutions were prepared by dilution. Britton-

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Robinson buffer (B-R), studied in the pH range from 2.0 to 9.0, was used as electrolyte

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support.

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2.2. NPAuGQD Synthesis and Characterization For NPAuGQD synthesis, a procedure based on Huang et al. [18] was used. In

short, 200 µL of a GQD suspension (8.0 mg mL-1), previously synthesized by citric acid pyrolysis [25], was added to 200 µL of HAuCl4 (1.0 mg mL-1). The mixture was kept at 100° C for 80 min to yield a stable purple suspension of NPAuGQD composite.

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Distribution of the GQDs was determined through transmission electron microscopy (TEM) using a JEOL JEM 1200 operated at 120 kV, and size was estimated by employing ImageJ software. SEM images were obtained from a Quanta 450 ESEM FEG scanning electron microscope, and Energy Dispersive X-ray Spectroscopy (EDS) analysis was performed from an EDAX microanalysis. X-ray diffractograms were obtained in Shimadzu XRD 6000 equipment, using Cu-Kα radiation.

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2.3. Electrochemical Measurements and Screen-Printed Electrode Modification The SPEs consist of a graphite counter and working electrodes (ϕ = 3.0 mm) and an Ag/AgCl pseudo-reference electrode, and were obtained from the laboratory of

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Professor Craig E. Banks at Manchester Metropolitan University. Screen-printing was

done using stencil design and a 1670RS microDEK screen printing machine, constructed

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following a few steps on a polyester substrate: first the deposition of the carbon-graphite

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ink (product code: C2000802P2; Gwent Electronic Materials Ltd, UK), followed by silver-silver chloride paste layer (product code: C2030812P3; Gwent Electronic Materials Ltd, UK) after the curing time of the printed graphite, and finally the dielectric ink

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(product code: D2070423D5; Gwent Electronic Materials Ltd, UK) was printed in order to define the electrodes area, and to cover the connections. After curing, the screen-

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printed electrodes were ready to be used, and have overall dimensions no larger than 4

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cm high and 0.7 cm wide. [26] For chemically modification of SPE, 4.0 µL of NPAuGQD previously obtained was dropped on the work electrode surface, and total solvent evaporation is expected before use. Electrochemical measurements were carried out using Potentiostat/Galvanostat PGSTAT204. Aliquots of 100 µL of B-R buffer solutions for blank and AFB1 solutions with different concentrations were added directly to the SPE surface using a micropipette.

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EIS measurements were performed using a FRA32M module, in the presence of 1.0 µM of AFB1, in a range of 0.1 MHz to 10 mHz, amplitude of 10 mV (rms) at continuous peak potential (vs. Ag/AgCl) suitable for each electrode.

2.4. Analytical Application Analytical validation of the proposed method was performed by using NPAuGQD-SPE for AFB1 determination in spiked malted barley (Pilsen, Amber, and

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Red) methanolic extract. The extraction procedures were performed based on described in the literature [27]. All samples were previously spiked according Brazilian Legislation [7] using 5.0 µg kg-1 of AFB1. Typically, 5.0 g of each malted barley samples were

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immersed in 20.0 mL of methanol, followed by 60 min on ultrasonic bath, centrifugation at 3000 rpm for 5 min, and filtration using a simple filter. After, appropriate dilutions of

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methanolic solutions in BR-Buffer were made to obtain three different final

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concentrations (1.5, 5.0, and 10.0 nM). Aliquots of 100 μL of each sample solution were analyzed directly using the developed method, and recovery values (triplicate) were

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found using an external calibration curve.

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3. RESULTS AND DISCUSSION

3.1. NPAu-GQD Characterization

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In order to confirm the nanocomposite structure, TEM analysis was carried out to evaluate the dispersion degree of NPAu formed. The preparation of NPAu was achieved with the assistance of GQD, which acted as a reducing and stabilizing agent for the formation of nanoparticles. As can be seen in Fig. 1A-B, a uniform and welldistributed dispersion of gold nanoparticles composed by a mixture of spherical and spherical condensed-like nanoparticles, was yielded. SEM images of comparative 8

electrodes are presented in Fig. 1C-D, where it is possible to observe that the SPE offers a surface modification after chemical incorporation of NPAuGQD, in which the presence of the gold was confirmed by EDX measurements, as well as by the characteristic voltammetric profile (Fig. S1). From the particle count (Fig. 1E) was obtained the value of 19 ± 6 nm as mean size, in agreement with what is described in the literature for the employed synthesis route [28]. X-ray diffraction analysis (Fig. S2) presents the welldefined peaks at 2 θ = 38°, 44.2°, and 64.4° characteristics of gold with FCC structure

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(JCPDS 04–0784; [29]).

3.2. Voltammetric Behavior of Aflatoxin B1 using NPAuGQD-SPE

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To investigate the behavior of AFB1 and evaluate the response of the proposed

electrode in toxin detection, the performance of NPAuGQD-SPE was compared to that of

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unmodified and GQD modified SPE. Fig. 2A shows baseline-corrected linear

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voltammograms obtained for each electrode and Fig. 2B shows a comparative graph based on current relative intensity (%) obtained for each voltammogram in Fig. 2A, in the presence of 1.0 µM of AFB1, in BR Buffer pH = 5.

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As expected, no redox signal was observed in the absence of AFB1, indicating that the evaluated electrodes do not contain electroactive species in this potential range.

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In analyte presence, it is possible to observe the presence of a faradaic process regarding

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the mycotoxin oxidation, later discussed (Scheme 1). At the bare SPE (green corrected curve), a peak was observed at +1.12 V with a current increment of 1.02 μA, corresponding to the oxidation of AFB1. Using the SPE modified with GQD (GQD-SPE, blue corrected curve), it is possible to observe a current increase of about 1.22 μA, but not yet achieving the performance presented for the proposed device (NPAuGQD-SPE, purple corrected curve), with current value of 3.06 μA. In addition, it is possible to

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observe (Fig. 2C) a shift of peak potential to less positive values (~ 350 mV, ΔEP values between the tested electrodes and proposed device are indicated by blue and green bars in Fig 2C), in crescent order 0.75 V, 1.04 V and 1.12 V to NPAuGQD-SPE, GQD-SPE, and SPE respectively. These improvements can be attributed to the electroactive area increased presented by the nanocomposite and mainly to combination between the excellent conductivity provided by GQD and NPAu and the ability of gold nanoparticles to decrease the overpotentials of many electroanalytical reactions improving the rate of

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charge transfer on the electrode surface. [30,31]. The effect of modifier on the voltammetric behavior of AFB1 was also

investigated from EIS experiments, shown in Fig. 2D. The oscillation amplitude was

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adjusted to 10 mV (RMS) in a frequency range of 0.1 MHz to 10 mHz. The work

Ag/AgCl employing AFB1 1.0 µM.

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potential (DC potential) was optimized for the peak potential for each electrode versus

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The equivalent circuit used for fit is depicted and was compatible with the Nyquist diagram. In this RS, CPE and RCT represent solution resistance, a constant phase element that is corresponding to double-layer capacitance and the charge transfer

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resistance, respectively. Electrical elements added, CPEADS and RADS, are associated with the adsorption of reaction intermediates and modifiers [32–34]. The fitted values of Rct

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for the SPE, GQD-SPE, and NPAuGQD-SPE were 40.3 kΩ (χ² = 0.1235), 14.9 kΩ (χ² =

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0.08862) and 117 Ω (χ² = 0.01167), respectively (Fig. 2D). The low Rct value obtained for NPAuGQD-SPE suggests that the charge-transfer process is faster when compared with the unmodified electrode, in agreement with the voltammetric studies. It was demonstrated that nanocomposite of NPAuGQD provides a significant improvement in the voltammetric response of the mycotoxin studied allowing development of an

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electroanalytical method for direct AFB1 determination without use of any additional biomolecule as electrode modifier.

3.3. Effect of experimental conditions The influence of pH variation on the electrode response was assessed using different Britton-Robinson buffer solutions prepared and adjusted to a pH range 2.0 to 9.0, in the presence of 25.0 nM of AFB1. As can be seen in Fig. 3A, there is an increase

and after that, there is a decrease in the peak current.

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in the peak current for the oxidation of AFB1, which reaches the maximum at pH = 5.0,

This behavior can be explained, considering the structural pattern of mycotoxin.

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Structurally, AFB1 molecules consist of two major functional groups: furan rings and a

coumarin highly substituted, which can take two distinct forms, which are pH-dependent

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[35]. When at more alkaline conditions, pH higher than 11.6, the coumarin takes the form

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of lactone and has its ring kept original, closed. At pH values lower than 6.8, the most stable form is that of acid from the ring-opening. Between 6.8 and 11.6, the two forms

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coexist, and it is not possible to distinguish them. From this, it can be suggested that at pH = 5.0 is the best condition since the predominant form is acid, which can be oxidized

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to form the carbonyl, according to the proposed mechanism, demonstrated in Scheme 1. As pH increases, the two forms coexist, and the current decrease may be related to the

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fact that a part of the acid is converted to lactone and is not liable to undergo any redox reaction under these conditions. The study of influence in the NPAuGQD-SPE conditioning potential for AFB1

determination, showed an increase of the peak current for oxidation when the applied potential varies from -0.3 to -0.2 V vs. Ag/AgCl, reaching the maximum in -0.2 V (Fig. S3A). When the accumulation potential was changed from -0.2 to 0.2 V vs. Ag/AgCl, the 11

peak current decreases gradually. The application of more negative potentials favors the interactions with AFB1, accumulating more species on the electrode surface, which will be later oxidized, resulting in a more significant current increase obtained, also improving the sensitivity of the methodology. The influence of the accumulation time ranging from 0 to 150 s on the oxidation of AFB1 was also investigated (Fig. S3B). The peak current increased gradually as the accumulation time increase from 0 to 90 s, this being the value chosen, and from this value there was a decrease in the current, which may be associated

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to the blocking of the electrode surface by the AFB1 species adsorbed, caused by the longer exposure time of the electrode prior to voltammetric measurement. [36]

The influence of the modifier amount used in the preparation of NPAuGQD-SPE

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on the AFB1 oxidation response was evaluated using the current response obtained from the construction of different devices (different modified SPE) employing different

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volumes of the composite suspension, in the range of 0.5 to 5.0 µL (Fig. S4). It was

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possible to observe the amplification of the oxidation current signal of AFB1 with the increase of the modifier volume used in the construction of NPAuGQD-SPE. There is an increase up to 4.0 μL, and after this value, the current remains stable, without significant

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variations. It can be suggested that high amounts of nanomaterial on the electrode surface can form aggregates on the electrode surface, making difficult the processes in the

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interface electrode/solution, leading to a decrease in the radial contribution of mass

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transport, which is more evident for lower volumes.

3.4. Analytical performance and application With all optimized parameters, it was possible to obtain the analytical

parameters for mycotoxin determination. For this purpose, AFB1 in a concentration range of 0.10 to 100 nmol L-1 was studied, and from this, the linear work region and its

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analytical curve could be obtained as demonstrated in Fig. 4A-B. Table 1 summarizes the analytical parameters obtained using the proposed device. The repeatability of the electrode in the determination of AFB1 was evaluated by performing five determinations with the same standard solutions of the toxin using the same NPAuGQD-SPE. The relative standard deviation (RSD) for the electrode response in the presence of 25.0 nM of AFB1 solution was 3.1%. The reproducibility of the electrode response was also studied. Five electrodes were prepared from the same

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NPAuGQD dispersion and the same SPE batch, also employing the 25.0 nM solution of AFB1 solution. The RSD for the responses between the different electrodes was 7.5%. The results show that the repeatability and reproducibility of the sensor for the

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determination of AFB1 are acceptable and indicate good reliability and agreement obtained for the electrodes constructed.

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The proposed method was evaluated in the determination of malted barley

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fortified samples, using the maximum permitted value established by Brazilian legislation (RDC 07/2011 [7]). Recovery values obtained from sample voltammograms (Fig. 4C) were found using external calibration, and they are presented in Table 2. In all cases,

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good recoveries were obtained, varying from 76 to 103%, quite satisfactory values considering the level of concentration being analyzed [37]. These results indicate that

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there is no significant matrix effect suggesting the usefulness of the proposed method for

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routine analytical control.

4. CONCLUSIONS A uniform, well-distributed nanocomposite dispersion of graphene quantum dots (GQD) and gold nanoparticles (NPAu) have been successfully yielded using a very favorable experimental route (fast, easy, and low-cost). Nanomaterial prepared was used as a modifier of a screen-printed electrode (NPAuGQD-SPE), and it has shown an 13

excellent catalytic effect on the faradaic process related to AFB1 oxidation. Considering other electroanalytical methodologies reported to AFB1 detection (Table S1), the proposed device was able to promote the direct determination of the mycotoxin evaluated without the use of any biomolecule as an electrode modifier. From the parameter optimization of the analytical methodology, it was possible to obtain the analytical merit parameters, being LDR in the range 1.0 to 50.0 nM, and calculated LOQ and LOD as 0.47 and 1.5 nM, respectively. The electrode performance was considered quite

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satisfactory, since the easily, quickly, and without biological materials involved methodology developed. It was also possible to analyze mycotoxin in fortified malted barley samples according to the limits allowed by the legislation, with good recovery

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rates, indicating that there is no significant matrix effect.

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Declaration of interests

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

5. ACKNOWLEDGMENTS

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The authors acknowledge financial support from Brazilian foundations: CAPES,

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CNPq (process number: 408309/2018-0), Fundação Araucária, and Brazilian Institute of Science and Technology (INCT) in Carbon Nanomaterials. Ava Gevaerd acknowledges CAPES and CNPq (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Brasil) for the fellowships.

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AUTHOR BIOGRAPHIES

Ava Gevaerd received her Ph. D. degree at Federal University of Paraná (UFPR) Brazil, in 2019, where she is currently a Postdoctoral Researcher. Her research interests include the development and characterization of new nanostructured electrode materials and development of miniaturized devices with electrochemical response for application in the environmental, health, food and pharmaceutical areas. Craig E. Banks is a professor of Chemistry at Manchester Metropolitan

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University and has elected as a highly cited researcher by Thomson Reuters;

Listed in the World’s Most Influential Scientific Minds 2014. His current research is directed toward the pursuit of study in the fundamental understanding and applications of nano-electrochemical systems such as graphene, carbon

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nanotube and nanoparticle derived sensors and developing novel

electrochemical sensors via screen printing and related techniques.

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Marcio F. Bergamini received his Ph.D. in Analytical Chemistry in 2007 from Universidade Estadual Paulista (UNESP), Araraquara-SP, Brazil. He is currently

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Professor of Chemistry at the Federal University of Paraná (UFPR), Curitiba-PR, Brazil. His principal research interest comprises the development of new electrochemical sensor for determination of inorganic and organic compounds in

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pharmaceutical, biological or environmental samples. Luiz H. Marcolino-Junior received his Ph.D. in Chemistry from Universidade

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Federal de São Carlos (UFSCar), Brazil, in 2007. He is a professor in the Chemistry Department at Universidade Federal do Paraná (DQ-UFPR). His current research interests are development of electrochemical sensors using

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nanostructured materials and development of microfluidic devices with electrochemical response.

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CAPTIONS

Fig. 1. A-B) Representative TEM images (10.000× and 25.000×) from NPAuGQD composite. Representative SEM images of C) SPE and D) NPAuGQD-SPE. E)

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Histogram counts of nanoparticles average.

Fig. 2. A) Baseline corrected linear sweep voltammograms for AFB1 employing different electrodes. Correlation bar graphs between B) Anodic peak current and C) Anodic peak

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potential of AFB1 for each electrode. D) Nyquist diagrams obtained for each electrode evaluated under potential peak conditions, frequency of 0.1 MHz to 10 mHz, and

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mV s-1; electrolyte BR-Buffer pH 5.

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amplitude of 10 mV with 10 data points per frequency decade. CAFB1=1.0 µM; υ= 100

Fig. 3. A) Baseline corrected linear sweep voltammograms obtained using NPAuGQD-

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SPE for pH study. B) Correlation curve between peak current and peak potential versus

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pH value. CAFB1=25.0 nM; υ= 100 mV s-1; electrolyte BR-Buffer in 2 to 8 range.

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Fig 4. A) Baseline corrected linear sweep voltammograms obtained using NPAuGQDSPE for crescent AFB1 concentrations (1.0, 2.5, 5.0, 7.5, 10.0, 25.0, and 50.0 nM) and B) Correlation curve between peak current and AFB1 concentration obtained for linear dynamic range. C) Representative voltammograms obtained for red malted barley spiked sample analysis. υ= 100 mV s-1; electrolyte BR-Buffer pH 5; n=3.

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Scheme 1. The proposed reaction for the AFB1 oxidation process

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FIGURE 1

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FIGURE 2

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FIGURE 3

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FIGURE 4

SCHEME 1 27

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TABLES

Table 1. Analytical Performance obtained with NPAuGQD-SPE for the determination of AFB1 (n= 3). 1.0 to 50.0

Sensitivity / A mol-1 L

92.4

LOD / nmol L-1

0.47

LOQ / nmol L-1

1.5

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LDR / nmol L-1

LDR - Linear Dynamic Range. LOD - limit of detection: calculated as 3*SDblank /

slope of analytical curve. LOQ - limit of quantification: calculated as 10*SDblank / slope of

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analytical curve.

Table 2. Results obtained for the determination of AFB1 in malted barley spiked

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samples (n=3).

Recovery (%)

Concentration (AFB1) added PILSEN

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1.5 nM

90±3.7

76±1.3

90±6.3

5.0 nM

89±3.5

98±6.0

103±4.2

10.0 nM

76±5.4

79±2.3

83±5.1

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AMBER

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