Optimization of the determination of deoxynivalenol in corn samples by liquid chromatography and a comparison of two clean-up principles

The determination of deoxynivalenol (DON) in corn by liquid chromatography with DAD detection was optimized. The separations were achieved on a Hypersil ODS column (100 × 4.6 mm; particle size 5 mm) by isocratic elution (0.6 cm3/min), a mobile phase consisting of acetonitrile–water in the ratio of 16:84. UV Detection was performed at 220 nm. Linear calibration curves were constructed in the concentration range of 0.72 – 12.00 ng/ml (equivalent to 0.29 – 4.8 mg/g corn). The detection limit measured as the signal-to-noise ratio (3:1) was 0.16 ng/ml for DON (equivalent to 0.06 mg/g corn). The efficiencies of two clean-up principles for crude corn extract were compared: solid-phase and immunochemical extraction. The efficiency of solid-phase extraction was found to be higher, with a value of 92.7 % when MycoSep 225 columns were used, while its value was 97.6 % when self-made activated charcoal–alumina–Celite–cationic columns were used. In contrast, the efficiency of the immunochemical columns (IMA) was only 73.8%. Itwas also found that the self-made columns could be used at least three times in a row, in that way differing from the MycoSep 225 columns, which could not be reused either with or without regeneration, as well as from the IMA columns, which had a regeneration efficiency of 53.6 %

Liquid chromatographic determination of fumonisins B1 and B2 in corn samples after reusable immunoaffinity column clean-up

The possibility of the liquid chromatographic determination of fumonisins B1 (FB1) andB2 (FB2) in corn samples with a reused immunoaffinity column (IMA) for the clean-up of the samples was investigated. After optimization of the chromatographic determination of FB1 and FB2 derivatized with o-phthaldialdehyde- 2-mercaptoethanol, the efficiency of the clean-up of spiked corn extracts with reuse of the IMA columns was studied, both with and without column regeneration. It was found that the IMAcolumn, designated for single-use only, can be used at least five times without regeneration and additional five times after regeneration. Regeneration consists of leaving the phosphate buffer saline solution on the column for one day at 4 ºC. The efficiency of the columns was tested by determining the recovery of FB1 and FB2, as well as the reproducibility of the determinations. The mean recoveries of FB1 and FB2 from corn spiked with FB1 at 1.0 mg/g and with FB2 at 0.5 mg/g (on the basis of 10 measurements) were 88.7%(RSD 10.2%) and 90.5%(RSD 6.1 %), respectively

Chemical composition of leaf extracts of Stevia rebaudiana Bertoni grown experimentally in Vojvodina

The chemical composition of leaf extracts of Stevia rebaudiana Bertoni, grown for the first time on an experimental field near Zrenjanin, was examined by GC–MS. The tested plant material was harvested in September of 2002. To analyze the chemical composition of the lipophilic components of the plant leaves, essential oils and ethyl acetate extract were isolated. Qualitative analysis of the essential oil obtained by hydrodistillation showed that among the identified 88 compounds, the majority were mono- and sesquiterpenes (50 types identified). By analysing the ethyl acetate extract, the presence of fatty acids (present as free and as esters), n-alkanes, n-alkenes, cyclic alkanes, alcohols, aldehydes, ketones, etc. was ascertained. Sesquiterpenes prevailed among the terpenes (50 types identified). Further constituents identified in ethyl acetate extract included sterols. Nerol, b-cyclocitral, safranal, aromadendrene, a-amorphene and T-muurolol were identified for the first time in this species, with match values over 90 %. Taking into consideration that these terpenes were identified for the first time in this species, it is obvious that Stevia rebaudiana grown in this area possesses certain specific characteristics that can be ascribed to cultivation on a domestic plantation

The content of deoxynivalenol and zearalenone in certain parts of Fusarium infected wheat heads

During the year 2006, climatic conditions were favourable for the appearance of head blight in the majority of localities in which wheat was grown in our country. In the locality of Apatin, in certain plots, the amount of detected infection was up to 25 infected heads per m2. During the harvest, heads with distinct disease symptoms and sporulation of Fusarium graminearum fungi were gathered. Grains from the parts of heads with manifested disease symptoms were separated into separate samples, together with the grains above and below the infested head part. Apart from ocular evaluation, the percentage of grain infestation by Fusarium genus fungi was determined in all three sample categories, using wet chamber method. Deoxynivalenol (DON) was determined in the samples after extraction, using acetonitrile-water (84:16 v/v) solution. Quantitative amount of DON was determined using liquid chromatography with DAD detector at 220 nm. The content of DON in the samples was as follows: grains with manifested disease symptoms 353,4 ppm (μg/g), grains above the infested head part 0,225 ppm (μg/g), grains below the infested part 0,125 ppm (μg/g). The content of zearalenone in the samples was determined using thin layer chromatography method. This toxic agent was determined only in the samples taken from the head part in which disease symptoms were clearly manifested in the amount of 2,1 ppm (μg/g)