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Updated: Jan 25, 2026

DNA Methylation: Bisulphite Modification and Analysis
Published on: October 21, 2011
In situ electrochemical analysis of freely dissolved methyl parathion enabled by negligible depletion
Long Pang1, Jiahui Hou1, Xingru Hu1
1Department of Material and Chemical Engineering, Zhengzhou University of Light Industry, Zhengzhou, People's Republic of China.
Abstract:
Negligible depletion micro-extraction (nd-ME) is widely used for determining the freely dissolved concentration of pollutants. However, it typically requires a long equilibrium time. In this study, an in situ electrochemical approach based on nd-ME was developed to assess the sorption coefficient of methyl parathion (MP) onto humic acid, as well as the freely dissolved MP concentration in the real water samples, using a beta-cyclodextrin modified reduced graphene oxide composite electrode (β-CD/RGO/GCE). The sorption behavior of MP toward two representative humic acids-Acros humic acid (AcHA) and Suwannee River humic acid (SRHA)-across a dissolved organic carbon (DOC) range of 0 to 25 mg L-1 was investigated with the proposed method and validated using the conventional negligible depletion-solid phase micro-extraction (nd-SPME) technique. Equilibrium between freely dissolved MP and the β-CD/RGO composite was achieved within 16 min, representing a reduction to less than 1/22 of the time required by nd-SPME. Under equilibrium conditions, the obtained sorption coefficients (log KDOC) were 4.56 for AcHA and 4.58 for SRHA, which align closely with the values derived from nd-SPME (log KDOC = 4.23 for AcHA and 4.27 for SRHA). Moreover, the measured freely dissolved MP concentrations in water samples ranged from 3.96 to 4.44 μg L-1, basically consistent with the nd-SPME results (freely dissolved concentration, Cfree = 4.17-4.76 μg L-1), demonstrating the reliability of the proposed method. Meanwhile, if combined with a portable electrochemical workstation, this study holds promise for providing a method applicable to on-site detection of the freely dissolved concentration of various compounds.
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