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Punjaisee C.,Chiang Mai University | Chaiyasut C.,Chiang Mai University | Chansakaow S.,Chiang Mai University | Tharata S.,Central Laboratory Thailand Co. | And 2 more authors.
African Journal of Agricultural Research

The isoflavone content of soybean was studied by incubated Thai native soybean (Glycine max (L) Merr, SJ.2) with Aspergillus oryzae BCC 3088. The changes of the isoflavone analogue content were analysed by HPLC. Mass spectrometry was used to confirm the presence of substances in fermented soybean with the authentic standards. After fermentation, total glycosides content of soybean fermented with A. oryzae BCC 3088 decreased but the proportion of aglycone markedly increased. As for the increases of isoflavone aglycone during the fermentation, the proportion of aglycones in total isoflavones was markedly higher in soybeans fermented with A. oryzae BCC 3088 than was those from uninoculated soybean. Furthermore, 8-hydroxygenistein (8-OHG) was found at the fourth day of fermentation. Therefore, fermentation of soybean with A. oryzae BCC 3088 results in higher levels of isoflavone aglycones and their corresponding, 8-OHG, which may enhance more health benefits than unprocessed soybean. © 2011 Academic Journals. Source

Yudthavorasit S.,Chulalongkorn University | Meecharoen W.,Central Laboratory Thailand Co. | Leepipatpiboon N.,Chulalongkorn University
Food Control

A new practical approach of using an analyte protectant (AP) for priming a gas chromatography (GC) system has been investigated for routine pesticide residue analysis. Matrix co-extractives are known to cause signal improvement, called the "matrix-induced chromatographic response enhancement effect". APs are known to provide advantages of signal enhancement independent of the matrix, but it takes time in routine applications to follow the common approach of adding APs to every extract. It is faster and easier to compensate for matrix effects by injecting an AP solution to coat active sites in the GC system at the beginning of the analytical sequence. In this study, 100 pesticides in highly pigmented QuEChERS extracts of chili were evaluated in the AP priming approach using GC-tandem mass spectrometry (MS/MS) over the course of many injections. The AP priming approach presented significantly more consistent results (87% of pesticides met RSD criteria) compared with injection sequences without the use of APs (42% of pesticides met RSD criteria). Also, AP priming with 300ng d-sorbitol was found to display a similar trend to mixed AP in priming effect. We demonstrated that this approach is fit-for-purpose in routine analysis. © 2014 Elsevier Ltd. Source

Meecharoen W.,Chulalongkorn University | Meecharoen W.,Central Laboratory Thailand Co. | Tayaputch N.,Central Laboratory Thailand Co. | Pitiyont V.,Central Laboratory Thailand Co. | Leepipatpiboon N.,Chulalongkorn University
Thai Journal of Agricultural Science

Thailand is the world's major producer and exporter of mangosteens, known as the "queen of fruits," earning 1,879 million baht from trade in 2009. Chemical residue analysis of whole mangosteen, to ensure compliance with export standards, is challenging due to interference from the dark-colored phenolic components in the fruit peel. QuEChERS (quick, easy, cheap, effective, rugged and safe) technique has been developed for sample preparation to test pesticide residues in mangosteens by liquid chromatography tandem quadrupole mass spectrometry (LC-MS/MS) analysis. Extraction parameters, such as types of organic solvents and buffer agents, were optimized. Sorbent types and composition of dispersive solid-phase extraction (d-SPE) were evaluated for optimum interference removal. The final QuEChERS parameters for the extraction of 10 g homogenized whole mangosteen employed 10 mL acetonitrile/acetate buffer mixture followed by a d-SPE (1:1 PSA:alumina N) cleanup step. The final analysis was performed by LC-MS/MS. Mass spectral acquisition was done by multiple reaction monitoring (MRM) with two mass transitions per compound to provide quantification and confirmation. In-house validation parameters included: matrix-matched linearity, method accuracy, method precision, limits of detection (LODs) and limits of quantitation (LOQs). LODs and LOQs for organophosphates were 0.005 mg kg-1 and 0.01 mg kg-1, for carbamates were 0.005 mg kg-1 and 0.01 mg kg-1, respectively. Extraction recoveries were: 71-116%, relative standard deviation (RSD) 8-19%, for carbamate; and 75-97%, RSD 6-20%, for organophosphate. The validation data met the requirements of regulation EC 396/2005, proving that the developed method is fit for routine analysis of organophosphates and carbamates in mangosteens. Source

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