Immunochemical methods for the determination of mycotoxins

The state-of-the-art immunochemical methods for the determination of mycotoxins are considered. Both instrumental (enzyme-linked immunosorbent assay, polarization fluoroimmunoassay, and sensor devices) and noninstrumental methods are presented. The principles of particular methods are considered, and the examples of the use of these methods for the determination of mycotoxins from various groups in food products and animal feeds are given; the main lines of development are discussed.     

Phosphorimetric determination of pyrene in gasoline and gasoline-contaminated soil samples

The determination of pyrene in gasoline and gasoline-contaminated soils using room-temperature phosphorimetry (RTP) in micellar solutions of sodium dodecyl sulfate was studied. It was found that pyrene can be selectively determined by RTP in the above materials. The accuracy of the procedure was verified by gas chromatography with mass-selective detection.     

Modeling of the stress state of the thumb carpometacarpal joint

The stress state of the carpometacarpal joint (CMJ)was studied in sound and pathologic states by methods of continuum mechanics. The CMJ geometric model was constructed according to the results of computer processing of the data of tomographic investigations in the extension position, which were obtained at Cheng Kung Medical University (Taiwan). The study of contact interactions in the CML region for a given geometry were performed numerically in the ABAQUS program code. The obtained numerical solutions of contact problems permit comparatively analyzing the stress distribution in the bone tissue for various thumb positions and study the stress state dependence on the bone tissue porosity (osteoporosis), which varies with human age.     

An immunochemical test for rapid screening of zearalenone and T-2 toxin

An immunochemically based test for non-instrumental simultaneous detection of zearalenone (ZEA) and T-2 toxin (T2) in feed was developed. The method combines clean-up of sample extract, pre-concentration of analytes by immunoextraction and immunodetection through the enzymatic reaction of horseradish peroxidase (HRP). The test is housed inside a standard 1-mL solid-phase extraction column and consists of three layers: two test layers (one for ZEA and another for T2) with immobilised specific antibodies and one control layer with bound anti-HRP antibodies. Feed extract was passed through an additional column with clean-up layer, which was disconnected after extract application. Total assay time was about 15 min for six samples and detection time was 4 min after chromogenic substrate application. Under optimised conditions a cut-off level for ZEA and T2 of 100 µg/kg was established. Different feed types were analysed for ZEA and T2 contamination by the proposed method and results were confirmed by LC-MS/MS.

Silanized quantum dots as labels in lateral flow test strips for C-reactive protein

The paper describes the first use of silanized semiconductor core-shell quantum dots as fluorescent labels for macromolecule, C-reactive protein determination in blood plasma. The controlled synthesis of CdSe cores, with successive shells of CdS, CdZnS, ZnS and coating with transparent, stable, and inert silica shell, provides quantum dots with a narrow emission band, high quantum yield, and prolonged signal stability. Finally, the quantum dots were conjugated with specific antibodies via carboxylic groups on the silica surface. The method was further used for the immunochromatographic assay of C-reactive protein, a diagnostically important inflammatory biomarker. Assays with both the fluorescent QDs and a widely used colloidal gold label were developed in parallel and compared. The silanized quantum dots provide a more sensitive assay with a detection limit of 1?ng/mL for C-reactive protein in standard solutions, whereas the common assay has a detection limit of 10?ng/mL. The possibility of quantitative evaluation of analyte content by a portable device was demonstrated; the accuracy of the measurements was in the range of 5%–10%. The tests were used to determine C-reactive proteins in human plasma samples. The selected optimized protocol for these samples is based on a 4-fold dilution. The final working range of the assay, 4–1,200?ng/mL, covers practically all important interval of C-reactive protein values for the characterization of acute, chronic, and local inflammatory processes. Due to their high physical stability and inertness as well as intense, stable, and reproducible fluorescence, silanized quantum dots may be applied for high-sensitive assays for different analytes.     

Rapid all-in-one three-step immunoassay for non-instrumental detection of ochratoxin A in high-coloured herbs and spices

A feasible three-step method for ochratoxin A (OTA) rapid detection was developed and applied for OTA screening in high-coloured matrices such as liquorice, ginger, nutmeg, black pepper, white pepper and Capsicum spp. spices at a control level of 10 μg kg⁻¹. The method was based on the clean-up tandem immunoassay column and involved three steps: extract application, washing step and application of chromogenic substrate. A significant simplification of the assay was reached by using an additional frit with conjugate inside the clean-up tandem immunoassay column. The time for analysis was less than 10 min, including 5 min for colour development. Results were visually evaluated as colour development for negative result or no colour development for positive result. The method was coupled with a simple methanol-based extraction. A total of 27 samples were screened for OTA with the proposed method. It was shown that two samples of red pepper and one sample of liquorice, pili-pili, chilli and cayenne were contaminated with OTA above the control level at 10 μg kg⁻¹, but none of tested ginger, nutmeg, black pepper and white pepper.     

Extraction preconcentration with anionic surfactants in acidic solutions

Extraction preconcentration with anionic surfactants in acidic solutions on the basis of the cloud point was studied. Advantages and disadvantages of this method were considered. Conditions of the phase separation of some anionic surfactants (sodium decyl sulfate, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate) in acidic solutions were studied. With the example of pyrene and its derivatives, it was demonstrated that these surfactants can be used for extraction preconcentration. Analytical characteristics of the determination of pyrene and its derivatives in model aqueous solutions by the fluorimetric method in combination with extraction preconcentration with sodium dodecyl sulfate were obtained     

Phosphorescence of molecules of polycyclic aromatic hydrocarbons in aqueous micellar solutions of sodium dodecylsulfate at room temperature

Deactivation of the excited states of pyrene, benzanthracene, and fluorene molecules in aqueous micellar solutions of sodium dodecylsufate is studied using steady and pulsed fluorimetry. Quenching of the singlet states of polyatomic hydrocarbons by thallium ions is considered. Effective, micellar, and biomolecular constants for the quenching rate are obtained. Phosphorescence constants for the aforementioned compounds are determined. Reasons behind the possibility of observing phosphorescence of polyaromatic compounds in micellar solutions at room temperature are ascertained. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 201–204, March–April, 1999.