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摘要
The quantification of transparent exopolymer particles (TEP) by colorimetric method is of large error and low repeatability, one major reason of which is related to the absence of clear definition and evaluation for part steps of the original method. It is obscure that the 80％ sulfuric acid solution, acted as the extraction solution in the determination of TEP, is prepared based on a volume ratio or mass ratio. Furthermore, the change of solubility of recently available Gum Xanthan (GX) from the market means that the original protocol is no longer applicable, and the grinding of GX stock solution with a tissue grinder is replaced by shaking with a rotating shaker in the study to prevent the excessive dissolution of GX. We found that different preparation techniques could result in the varied concentrations of 80％ H2SO4. The duration of shaking during the preparation of standard solution significantly affected the slope of the calibration curve, which caused different correction results of TEP. The impacts of different extraction solution concentrations and shaking time of GX solution on the quantification of TEP were investigated based on the field sampling and laboratory analysis. The extraction capacities of H2SO4 with different concentrations for Alcian Blue were distinct, but had limited effect on the final measuring result of TEP. The change of the standard curve slope came along with the variation of shaking time, which markedly altered the detection limit and calibration result, and the extended shaking time was in favor of the determination of low-concentration TEP. It was suggested that the extraction solution concentration, shaking time and filtration volume of standard solution are required to be well controlled and selected to obtain more accurate results for TEP with different concentrations.
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