Testing the suitability of different high-performance liquid chromatographic methods to determine aflatoxin M1 in a soft fresh Italian cheese

Enzyme-assisted extraction for the HPLC determination of aflatoxin M1 in cheese

The extraction of aflatoxin M1 (AFM1) from cheese is generally carried out using chlorinated organic solvents. In this study, two innovative methods were developed, based on an enzyme-assisted (EA) extraction using proteolytic enzymes (pepsin or pepsin-pancreatin). After purification through an immunoaffinity column, AFM1 is determined by HPLC-FLD. A comparison between the new EA methods and an established chloroform (CH) method was carried out on 24 cheese samples. The results showed that the extraction efficiency of the EA methods was independent of ripening time of cheese, whereas the CH method was not able to fully recover AFM1 from ripened cheeses. The simpler (pepsin) of the two methods has been adopted by our laboratory for routine analysis of AFM1 in cheese. In comparison with the CH method, the pepsin-HCl (P-HCl) method is simpler, avoiding solvent evaporation, dissolution and partition in a separating funnel; moreover, it gives higher recoveries, comparable LOD and LOQ and more accurate results.

Efficient Conjugation of Aflatoxin M1 With Bovine Serum Albumin through Aflatoxin M1-(O-carboxymethyl) Oxime and Production of Anti-aflatoxin M1 Antibodies

BACKGROUND

Aflatoxins are the most extensively studied group of mycotoxins produced by molds, especially the Aspergillus group, which are highly toxic to animals and humans.

OBJECTIVES

Since immunoassay is a simple and rapid method for the analysis of many toxic substances in comparison to the chromatographic methods, it is necessary to produce specific and sensitive antibodies for detection of Aflatoxin M1 (AFM1). The current study was conducted to produce bioconjugate of Aflatoxin M1 (AFM1) with Bovine Serum Albumin (BSA) as well as to generate specific antibodies against AFM1 for immunoassay of the mycotoxin.

MATERIALS AND METHODS

First, AFM1 was converted to AFM1-(O-carboxymethyl) oxime derivative. Then, AFM1-oxime was coupled with BSA and the product was assessed by UV-VIS spectrophotometry. In order to generate polyclonal antibodies against AFM1, rabbits were immunized with BSA-AFM1 conjugate. Produced antibodies were purified using ion exchange chromatography and BSA-Sepharose 4B affinity chromatography. The titers and specificity of the produced antibodies were determined by Enzyme-Linked Immunosorbent Assay (ELISA).

RESULTS

The results indicated that coupling of AFM1 with O-(Carboxymethyl) hydroxylamine hemihydrochloride was suitable and 12 moles of AFM1-oxime were successfully coupled to each mole of BSA. In addition, the titers and specificity of the prepared antibody were considerable compared to standard anti-AFM1 antibodies. The relative cross-reactivity of each toxin (relative to AFM1) with purified anti-AFM1 antibodies, as determined by the amount of aflatoxin necessary to cause 50% inhibition of enzyme activity, was 70, 105, 240, and 2500 ng/mL for AFB1, AFB2, AFG1, and AFG2, respectively.

CONCLUSIONS

The prepared antibody can be used for the development of an ELISA kit to assay AFM1 in milk and other biological fluids.

Rapid analysis of aflatoxin M1 in milk using dispersive liquid-liquid microextraction coupled with ultrahigh pressure liquid chromatography tandem mass spectrometry

A simple, rapid, and sensitive method based on simultaneous protein precipitation and extraction of aflatoxin M1 (AFM1) followed by dispersive liquid-liquid microextraction (DLLME) and ultrahigh pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis was developed for the determination of AFM1 in milk samples. In order to precipitate the proteins and extract AFM1 from milk, a sample pretreatment using acetonitrile and NaCl as the extraction/denaturant solvent and salting-out agent, respectively, was optimised. Subsequently, the acetonitrile (upper) phase, containing AFM1, was used as the disperser solvent in DLLME, and extractant (chloroform) and water were added in turn to the extract to perform the DLLME process. The main parameters affecting the extraction efficiency of the whole analytical procedure, such as acetonitrile volume, amount of salt, type and volume of extractant and water volume, were carefully optimised by experimental design. Under optimum conditions, the developed method provides an enrichment factor of 33 and detection and quantification limits (0.6 and 2.0 ng kg(-1), respectively) below the maximum levels imposed by current regulations for AFM1 in milk and infant milk formulae. Recoveries (61.3-75.3%) and repeatability (RSD < 10, n = 3), tested in different types of milk at four AFM1 levels, met the performance criteria required by EC Regulation No. 401/2006. Moreover, the matrix effect on the signal intensity of the analyte was negligible. The proposed method provides a rapid extraction and an accurate determination of AFM1 in milk and formula milk using a simple and inexpensive sample preparation procedure.

Microfluidic chip-based nano-liquid chromatography tandem mass spectrometry for quantification of aflatoxins in peanut products

Aflatoxins (AFs), a group of mycotoxins, are generally produced by fungi Aspergillus species. The naturally occurring AFs including AFB1, AFB2, AFG1, and AFG2 have been clarified as group 1 human carcinogen by International Agency for Research on Cancer. Developing a sensitive analytical method has become an important issue to accurately quantify trace amount of AFs in foodstuffs. In this study, we employed a microfluidic chip-based nano LC (chip-nanoLC) coupled to triple quadrupole mass spectrometer (QqQ-MS) system for the quantitative determination of AFs in peanuts and related products. Gradient elution and multiple reaction monitoring were utilized for chromatographic separation and MS measurements. Solvent extraction followed by immunoaffinity solid-phase extraction was employed to isolate analytes and reduce matrix effect from sample prior to chip-nanoLC/QqQ-MS analysis. Good recoveries were found to be in the range of 90.8%-100.4%. The linear range was 0.048-16 ng g(-1) for AFB1, AFB2, AFG1, AFG2 and AFM1. Limits of detection were estimated as 0.004-0.008 ng g(-1). Good intra-day/inter-day precision (2.3%-9.5%/2.3%-6.6%) and accuracy (96.1%-105.7%/95.5%-104.9%) were obtained. The applicability of this newly developed chip-nanoLC/QqQ-MS method was demonstrated by determining the AFs in various peanut products purchased from local markets.

Developments in mycotoxin analysis: an update for 2011-2012

This review highlights developments in mycotoxin analysis and sampling over a period between mid-2011 and mid- 2012. It covers the major mycotoxins aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxin, patulin, trichothecenes, and zearalenone. A section on mycotoxins in botanicals and spices is also included. Methods for mycotoxin determination continue to be developed using a wide range of analytical systems ranging from rapid immunochemical-based methods to the latest advances in mass spectrometry. This review follows the format of previous reviews in this series (i.e. sections on individual mycotoxins), but due to the rapid spread and developments in the field of multimycotoxin methods by liquid chromatography-tandem mass spectrometry, a separate section has been devoted to advances in this area of research.