Sheot Harn Chan

Multi-Mycotoxin Screening Reveals Separate Occurrence of Aflatoxins and Ochratoxin A in Asian Rice

The determination of important regulated mycotoxins in rice has been reported previously but not in the individual matrix of white, brown, red, and basmati rice with respect to the matrix effect, recovery, and stability. A total of 190 Asian rices were examined for regulated mycotoxin contamination by the LC-ESI-MS/MS method. Significant variation (p < 0.05) in the matrix effect was observed for fumonisins. Methanol improved the limits of detection (LOD) for HT-2 from 50 μg/kg to 2.3 μg/kg by promoting ionization efficiency of the ammonium-adduct. LOD and limits of quantitation ranged from 0.1 to 18 μg/kg and 0.2-31 μg/kg, respectively. All analytes degraded by more than 50% on storage, except fumonisins. Acetic acid (1%) provided significant improvement (p < 0.05) in recovery for all analytes in selected white rice from Thailand and China. Mean recovery ranged from 70 to 120%. RSD values were lower than 15% for all analytes. Five AFB1 and single OTA positive samples were detected. No correlation between mycotoxin contamination and rice species (r = 0) exists.

A flow-injection mass spectrometry fingerprinting scaffold for feature selection and quantitation of Cordyceps and Ganoderma extracts in beverage: a predictive artificial neural network modelling strategy

Flow-injection mass spectrometry (FI/MS) represents a powerful analytical tool for the quality assessment of herbal formula in dietary supplements. In this study, we described a scaffold (proof-of-concept) adapted from spectroscopy to quantify Cordyceps sinensis and Ganoderma lucidum in a popular Cordyceps sinensis /Ganoderma lucidum -enriched health beverage by utilizing flow-injection/mass spectrometry/artificial neural network (FI/MS/ANN) model fingerprinting method with feature selection capability. Equal proportion of 0.1% formic acid and methanol (v/v) were used to convert extracts of Cordyceps sinensis and Ganoderma lucidum into their respective ions under positive MS polarity condition. No chromatographic separation was performed. The principal m/z values of Cordyceps sinensis and Ganoderma lucidum were identified as: 104.2, 116.2, 120.2, 175.2, 236.3, 248.3, 266.3, 366.6 and 498.6; 439.7, 469.7, 511.7, 551.6, 623.6, 637.7 and 653.6, respectively. ANN models representing Cordyceps sinensis and Ganoderma lucidum were individually trained and validated using three independent sets of matrix-free and matrix-matched calibration curves at concentration levels of 2, 20, 50, 100, 200 and 400 μg mL-1. Five repeat analyses provided a total of 180 spectra for herbal extracts of Cordyceps sinensis and Ganoderma lucidum. Root-mean-square-deviation (RMSE) were highly satisfactory at <4% for both training and validation models. Correlation coefficient (r2) values of between 0.9994 and 0.9997 were reported. Matrix blanks comprised of complex mixture of Lingzhi fermentation solution and collagen. Recovery assessment was performed over two days using six sets of matrix blank (n = 6) spiked at three concentration levels of approximately 83, 166 and 333 mg kg-1. Extraction using acetonitrile provided good overall recovery range of 92-118%. A quantitation limit of 0.2 mg L-1 was reported for both Cordyceps sinensis and Ganoderma lucidum. Intra-day and inter-day RMSE values of 7% or better were achieved. Application of the scaffold in a high-throughput routine environment would imply a significant reduction in effort and time, since the option of having a model driven analytical solution is now available.

Feed-forward neural network assisted by discriminant analysis for the spectroscopic discriminantion of cracked spores Ganoderma lucidum: A prospective biotechnology production tool

A major problem for manufacturers of cracked spores Ganodermalucidum, a traditional functional food/Chinese medicine (TCM), is to ensure that raw materials are consistent as received from the producer. To address this, a feed-forward artificial neural network (ANN) method assisted by linear discriminant analysis (LDA) and principal component analysis (PCA) was developed for the spectroscopic discrimination of cracked spores of Ganodermalucidum from uncracked spores. 120 samples comprising cracked spores, uncracked spores and concentrate of Ganodermalucidum were analyzed. Differences in the absorption spectra located at ν1 (1143 - 1037 cm-1), ν2 (1660 - 1560 cm-1), ν3 (1745 - 1716 cm-1) and ν4 (2845 - 2798 cm-1) were identified by applying fourier transform infra-red (FTIR) spectroscopy and used as variables for discriminant analysis. The utilization of spectra frequencies offered maximum chemical information provided by the absorption spectra. Uncracked spores gave rise to characteristic spectrum that permitted discrimination from its cracked physical state. Parallel application of variables derived from unsupervised LDA/PCA provided useful (feed-forward) information to achieve 100% classification integrity objective in ANN. 100% model validation was obtained by utilizing 30 independent samples. ν1 was used to construct the matrix-matched calibration curve (n = 10) based on 4 levels of concentration (20%, 40%, 60% and 80% uncracked spores in cracked spores). A coefficient of correlation (r) of 0.97 was obtained. Relative standard deviation (RSD) of 11% was achieved using 100% uncracked spores (n = 30). These results demonstrate the feasibility of utilizing a combination of spectroscopy and prospective statistical tools to perform non destructive food quality assessment in a high throughput environment.

Isotope ratio analysis of carbon and nitrogen by elemental analyser continuous flow isotope ratio mass spectrometry (EA-CF-IRMS) without the use of a reference gas

A new approach to normalize measured isotope ratios (carbon and nitrogen) by elemental analyser continuous flow isotope ratio mass spectrometry (EA-CF-IRMS) was evaluated. Isotope ratios of samples are altered during the IRMS measurement and must be corrected for both instrumental drifts as well as instrumental isotope fractionation for comparing data within and between laboratories. Traditionally, the isotope ratio of a reference gas is measured intermittently to correct for time dependent changes in isotope fractionation over the course of the measurement. However, this step appears to be redundant as bracketing standards are usually included in a measurement run for comparisons between measurements and laboratories and they can serve, in principle, the same purpose. Here we show that measurements without normalization to the reference gas are on a par in terms of accuracy and precision with those where the reference gas was used when employing an optimized strategy for bracketing samples with reference standards. Abolishment of intermittent reference gas measurements in EA-CF-IRMS analysis has the potential to cut short the analysis time significantly, can help to save costs in commercial IRMS laboratories and may open a new door for instrument developers to design high through-put IRMS instruments.

Discriminating authentic Nostoc flagelliforme from its counterfeits by applying alternative ED-XRF and FTIR techniques

Nostoc flagelliforme is an edible blue-green algae belonging to the Nostocaceae family. It is recognised as a Chinese delicacy in south-eastern Asia and is widely consumed. Due to its high economic value and diminishing supply, as a result of overharvesting, counterfeits have often been found in the retail markets. Methods involving microscopy and histochemistry were conventionally applied to differentiate the authentic N. flagelliforme from its counterfeits. In this paper, we report an alternative analytical approach, using a combination of non-destructive energy dispersive X-ray fluorescence (ED-XRF) and Fourier-transform infrared (FTIR) spectroscopy, to achieve the objective of authentic N. flagelliforme verification. In view of the scarcity of this Chinese delicacy, such a non-destructive methodology would be ideal to preserve the integrity of the sample and yet provide a means to discriminate between authentic and counterfeit samples.

Evaluation of triple stage mass spectrometry as a robust and accurate diagnostic tool for determination of free cordycepin in designer egg.

Direct determination of free cordycepin in designer egg using a highly selective mass spectrometric (MS) technique aided by a rapid and efficient dilute-and-shoot workflow would enhance their application as diagnostic tools in food fraud control. Here, triple stage mass spectrometry (MS(3)) demonstrated excellent analyte selectivity capability even when incomplete chromatographic separation was performed. Method validation was performed at six concentration levels of 100, 200, 400, 800, 1200 and 1600ngg(-1). Spiking experiments were examined at three concentration levels of 200, 400, and 1200ngg(-1) in individual egg white and egg yolk, measured over 2days. MS(3) enabled ion chromatograms with zero-background interference to be made in egg extracts. MS(3) eliminated severe over recovery (p<0.05) observed in all fortified samples, a challenge that MRM-transition could not address in a single step. Matrix-matched calibrants were needed to compensate for over recovery observed under MRM-transition mode.