A label-free, direct solid-phase fluorimetric analysis of ochratoxin A in agricultural products with monoclonal antibody-immobilized monolith.

We established a method for directly measuring mycotoxin ochratoxin A (OTA) in foods by solid-phase fluorescence of monolith-immobilized antibodies. The antibody was introduced onto only one side of an 8 mm-diameter, 3 mm-thick monolith via covalently immobilized protein G. 4 µg (2.7 × 10-11 mol) of antibody was immobilized per one monolith. A maximum of 10 µg (2.4 × 10-11 mol) OTA adsorbed to the activated side of each monolith. The amount of OTA adsorbed and the fluorescence intensity showed good linearity in the range of 0.5-3 ng OTA. Loading the sample solution onto the non-antibody side on the monolith blocked the hydrophobic fluorescent matrices from reaching the immobilized surface of the antibody. The proposed method was able to detect 1 ng OTA/g in solid samples with complex matrices. Mean recoveries obtained at spiked concentration of 3 ng g-1 OTA/g were 78-90% with relative standard deviations of <7.9%.

[Surveillance of Chromium (VI) Concentrations in Mineral Water Products in 2018].

We used ion chromatography with post column derivatization to measure chromium (VI) concentrations in 155 mineral water (MW) products purchased from markets in Japan in 2018. Chromium (VI) recovery in spiked samples of the 155 MW products ranged from 95 to 106%, suggesting that this method is well suited for ensuring that MW products meet the requisite health and food safety standards. Chromium (VI) levels were above detection limits in 54 of the MW products, giving a total detection rate of 35%. The minimum and maximum chromium (VI) concentrations in all of the MW products were 0.0001 mg/L and 0.045 mg/L, respectively. The median chromium (VI) concentration was 0.0003 mg/L, with most MW products having chromium (VI) concentrations in the range of 0.0001 to 0.0002 mg/L. None of the MW products had chromium (VI) concentrations that exceeded the current standard value (0.05 mg/L) for MW in Japan.

Direct quantitation of the preservatives benzoic and sorbic acid in processed foods using derivative spectrophotometry combined with micro dialysis.

The preservatives benzoic acid and sorbic acid are generally quantified with separation techniques, such as HPLC or GC. Here we describe a new method for determining these compounds in processed food samples based on a narrowness of the UV-visible spectral band width with derivative processing. It permits more selective identification and determination of target analytes in matrices. After a sample is purified by micro dialysis, UV spectra of sample solutions were measured and fourth order derivatives of the spectrum were calculated. The amplitude between the maximum and minimum values in a high-order derivative spectrum was used for the determination of benzoic acid and sorbic acid. Benzoic acid and sorbic acid levels in several commercially available processed foods were measured by HPLC and the proposed spectrometry method. The levels obtained by the two methods were highly correlated (r2>0.97) for both preservatives.

Evaluation of the matrix effect on gas chromatography--mass spectrometry with carrier gas containing ethylene glycol as an analyte protectant.

The consequences of matrix effects in GC are a major issue of concern in pesticide residue analysis. The aim of this study was to evaluate the applicability of an analyte protectant generator in pesticide residue analysis using a GC-MS system. The technique is based on continuous introduction of ethylene glycol into the carrier gas. Ethylene glycol as an analyte protectant effectively compensated the matrix effects in agricultural product extracts. All peak intensities were increased by this technique without affecting the GC-MS performance. Calibration curves for ethylene glycol in the GC-MS system with various degrees of pollution were compared and similar response enhancements were observed. This result suggests a convenient multi-residue GC-MS method using an analyte protectant generator instead of the conventional compensation method for matrix-induced response enhancement adding the mixture of analyte protectants into both neat and sample solutions.