Ochratoxin extraction

Method A 50 /jl (ca 250 ng) of the stock solution or of the purified extract is transferred into a reaction tube. One ml of boron trifluoride is added to the methanol, the cap is closed, and the tube is kept on a block heater (80°C) for 10 min. Two ml of water and 2 ml of -hexane are added. After thorough mixing, the layers are left to separate. Using disposable glass Pasteur pipettes, the upper layer is transferred to a clean, small vial. The extraction is repeated another two times with 2-ml portions of n-hexane. The hexane extracts are taken to dryness with a nitrogen stream, and the residue is dissolved in 1 -2 ml of injection solvent. Ochratoxin A is confirmed by the presence of an OA-methyl ester peak at delayed retention time and the disappearance of the OA peak (62). 

S Uchiyama, Y Saito, M Uchiyama. Protein-binding of ochratoxin A and its extractability from pro-teinous food. J Food Hygene Soc Japan 26 651-657, 1985. 

D Abramson. Measurement of ochratoxin A in barley extracts by liquid chromatography-mass spectrometry. J Chrom 391 315-320, 1987. 

Medina, A., Valle-Algarra, F.M., Gimeno-Adelantado, J.V., Mateo, R. Mateo, F. and Jimenez, M. (2006) New method for determination of ochratoxin A in beer using zinc acetate and solid-phase extraction silica cartridges,/. Chromatogr. A, 1121, 178-183. 

Serra, R., Mendonqa, C., Abrunhosa, L., Pietri, A. and Venancio, A. (2004) Determination of ochratoxin A in wine grapes comparison of extraction procedures and method validation, Anal. Chim. Acta, 513 (1), 41 -47. 

The difference in wine making is also the reason for the differences in ochratoxin A concentration between white, rose, and red wine. White grapes are immediately pressed after harvest, whereas red wine grapes are mashed and macerated to extract anthocyanins from the berry skins. Maceration lasts either for several days at elevated temperature or for several hours using pectolytic enzymes after heating of the must to 80°C. 

Moller, T.E. and Nyberg, M. 2003. Ochratoxin A in raisins and currants Basic extraction procedure used in two small marketing surveys of the occurrence and control of the heterogeneity of the toxins in samples. Food Addit. Contam. 20, 1072-1076. 

Ochratoxin A, citrinin. Apply extracts of cereals or fungal cultures apply... 

For many solid samples, a solvent extraction step is still necessary. Extraction with acidic chloroform, acidic ethyl acetate containing 2 mol sodium chloride/l or methanol-sodium carbonate (1%), followed by back-extraction to sodium bicarbonate, has been recommended (Monaci Palmisano, 2004). After washing the column, ochratoxin A can be eluted with methanol and, if necessary, further purified through an immunoaffinity column. 

TLC is still regarded as a cheap and effective technique for ochratoxin A estimation, particularly because of its low cost and adaptability. New methods include extraction with a mixture of phosphoric acid and dichloromethane and purification by liquid-liquid partitioning into sodium hydrogen carbonate, before separation by normal-phase TLC and detection by fluorescence as usual (Pittet Royer, 2002) and extraction with a mixture of methanol and aqueous sodium bicarbonate solution, followed by partitioning into toluene before TLC (Ventura et al.,2005). 

Other simulation experiments performed in our laboratory include design of MIP adsorbents for solid-phase extraction of atrazine [77], DDT, lindane, aflatoxin Bl, ochratoxin A, and tylosin (unpublished data) and the development of assay/ sensor recognition elements for biotin (unpublished data) and creatinine [78]. In all these cases, molecular modeling proved to be a useful tool for MIP design. It would... 

Those mycotoxins, such as ochratoxin A, which contain a carboxyl group, can be readily extracted into an organic solvent such as chloroform after acidifying the commodity to ensure that it exists entirely in the undissociated form. Aqueous phosphoric acid (0.1 mol 1 ) is frequently used. Ochratoxin A can then be back-extracted from the chloroform using sodium hydrogencarbonate solution or trapped on a column of diatomaceous earth... 

The usual methods for the assessment of ochratoxin A are immunochemical detection or RPLC coupled with fluorescence detection (ilex=247 nm, 2eni = 480nm). For ochratoxin sample preparation, the sample is mixed with HCl and MgCli, followed by extraction into toluene. The toluene supernatant is passed through a silica gel column and the column is washed with hexane, toluene-acetone, and toluene. Ochrotoxin A is eluted with toluene-acetic acid and dried down to 40°C. The residue is dissolved in a mobile phase, filtered, and analyzed by HPLC. The limit of ochratoxin A in grape juice is proposed to be fixed at 3 pg per kg. 

As made evident in Table 2, immunoassays are also in routine use for analysis of mycotoxins, a group including the most dangerous and analytically elusive food-related toxins. In spite of the small structural differences within specific groups of mycotoxins (aflatoxins, ochratoxins, trichothecenes), assay specificity toward the other mycotoxin groups is always total. Determination of AEBi, toxin T-2, and ochratoxin A in a single extract from barley grains has been reported. Mycotoxins may be determined in crude extracts of various foodstuffs at concentration over 20 ng per kg. This detection limit can... 

Jomet, D., Busto, D. O., and Guasch, J. 2000. Solid-phase extraction applied to the determination of ochratoxin A in wines by reversed-phase high-performance liquid chromatography. J. Chromatogr. A. 882 29-35. 

Giraudi, G., Anfossi, L., Baggiani, C., Giovannoli, C., and Tozzi, C. 2007. Solid-phase extraction of ochratoxin A from wine based on a binding hexapeptide prepared by combinatorial synthesis. J. Chromatogr. A 1175 174-178. 

Aqay et al. (2011) have described a method based on nano-LC-quadrupole time-of-flight-MS (nano-LC-QTOF-MS) for the screening of ochratoxins in wheat and cereal samples. The mycotoxin ochratoxin A (OTA) and cross-reacting mycotoxin analogues were analyzed in these samples after extraction using a novel direct inhibition flow cytometric immunoassay with superparamagnetic microbeads coated with monoclonal antibodies. The limit of detection (LOD) for OTA was 0.15 ng g", below the lowest... 

---