吸附树脂层析法是表征环境水样有机物亲疏水组分分布的常用方法。 作为柱层析的基本参数, 临界保留因子对亲疏水物质的吸附及分离效果具有潜在影响。 以河北某水库的水样为例, 将有机物分为亲水物(HIS)、 疏水酸(HOB)、 疏水碱(HOA)和疏水中性物(HON), 考察了在不同临界保留因子分离条件下(k′cr=5, 10, 25, 50, 100)亲疏水组分有机物含量分布, 并着重考察了其光谱学特性。 研究发现, 亲疏水组分的浓度分布取决于k′cr值的设置, 疏水组分的比例和疏水程度随k′cr的增大而增大。 在250~280 nm波长范围内, 亲水组分HIS的紫外吸光度随k′cr的增高而增高, 而疏水组分HOA和HOB则呈现相反趋势, 亲水与疏水组分之间的紫外光谱差异性随k′cr增大而增大。 此外, 疏水组分单位质量浓度的吸光度对k′cr的取值敏感, 推测k′cr可能影响所得组分的芳香族官能团性质。 进一步考察了各组分的三维荧光光谱, 并采用荧光区域积分和荧光指数对图谱进行解析。 结果表明, 亲疏水组分的荧光峰形态、 荧光区域分布和荧光团密度与k′cr值有关, 荧光指数BIX, HIXem和Peak T/C对k′cr的取值敏感, 说明k′cr可能对所得组分的具体化学组成乃至迁移转化行为产生影响。 因此在分离并表征环境水样的亲疏水组分分布时, 应特别注意临界保留因子的设置并明确标明其取值。

Adsorption resin chromatography obtains wide application in characterizing the distribution of hydrophilic/hydrophobic fractions in natural organic matters. As a basic parameter of chromatography, the critical retention factor has a potential impact on results of adsorption and separation. In this study, water samples from a reservoir were fractionated into hydrophilic substances (HIS), hydrophobic acids (HOA), hydrophobic bases (HOB) and hydrophobic neutrals (HON) under the conditions of various critical retention factors (k′cr=5, 10, 25, 50, 100). The distribution of the hydrophilic/hydrophobic fractions were systematically characterized, with special attention placed to their spectroscopic properties. The results showed that the relative proportions of hydrophilic/hydrophobic fractions depended on the value of k′cr, and the proportion of hydrophobic components and the degree of hydrophobicity increased with the increase of k′cr value. In wavelength range of 250~280 nm, the UV absorbance of HIS increased with increasing k′cr, while the absorbance of hydrophobic fractions performed in the reserved trend. The difference in UV spectra between the hydrophilic and hydrophobic fractions was enlarged with increasing k′cr value. The specific UV absorbance (i. e. UV absorbance per unit concentration) of the hydrophobic fractions was found to be sensitive to the value of k′cr, indicating that the critical retention factor may affect the properties of aromatic functional groups in the obtained fractions. Three dimensional excitation-emission matrix fluorescence spectroscopy was further conducted to characterize the hydrophilic/hydrophobic fractions, with the spectral data analyzed using fluorescence regional integration and fluorescence index techniques. The results revealed that the fluorescence peak appearance (peak location and intensity), fluorescence regional distribution and fluorophore density were related to the value of k′cr, meanwhile the fluorescence indices of BIX, HIXem and Peak T/C were sensitive to the value of k′cr. It is speculated that the critical retention factor may have profound impact on the chemical compositions and transformation behaviors of the resultant hydrophilic/hydrophobic fractions. Therefore, it is suggested that particular attention should be paid to the setting of the critical retention factor and indicating its value clearly when conducting separating and characterizing of the distribution of hydrophilic/hydrophobic fractions.