The molecular weight distribution (MWD) of dissolved organic matter (DOM) in lake waters from Lake Hongfeng was examined using high performance size exclusion chromatography (HPSEC) with UV-vis absorbance and fluoresc...The molecular weight distribution (MWD) of dissolved organic matter (DOM) in lake waters from Lake Hongfeng was examined using high performance size exclusion chromatography (HPSEC) with UV-vis absorbance and fluorescence detection. The elution curves obtained by absorbance and fluorescence techniques expressed similar patterns, with the exception of diminishing of large fraction and the peaks behind several seconds in fluorescence chromatograms. According to its molecular weight (MW), DOM in water samples is divided into several fractions: large ({>3.5} kDa); medium-large ({3.5}-{2.0} kDa); medium ({2.0}-{1.0} kDa) and small ({<1.0} kDa). The average molecular weight was calculated using the elution curve detected by UV-vis absorbance and fluorescence detection techniques. The results showed that the weight-average molecular weight (Mw) and number-average molecular weight (Mn) calculated by UV-vis absorbance techniques range from 1750 to 2050 Dalton and from 1450 to 1850 Dalton, respectively. And the Mw and Mn obtained by fluorescence detection are lower by 50 to 400 Dalton. As a reference, the molecular weight of Fluka humic acid (FHA) is larger than that of water samples by about 200 Dalton. The average molecular weight of DOM for water samples collected in March and July was compared. The results revealed that the molecular weight is lower for water samples obtained in July than that obtained in March, indicating the ambient environment has an influence on the molecular weight, including photo-degradation and biological activity.展开更多
文章建立了高效分子排阻色谱(HPSEC)法测定美罗培南中聚合物杂质的含量。采用TSK gel G2000SWXL凝胶色谱柱;检测波长为220 nm;柱温25℃;流动相为0.1%三乙胺溶液(用磷酸调至中性)-乙腈(95∶5);流速0.8 m L/min;进样体积20μL。结果表明:...文章建立了高效分子排阻色谱(HPSEC)法测定美罗培南中聚合物杂质的含量。采用TSK gel G2000SWXL凝胶色谱柱;检测波长为220 nm;柱温25℃;流动相为0.1%三乙胺溶液(用磷酸调至中性)-乙腈(95∶5);流速0.8 m L/min;进样体积20μL。结果表明:美罗培南峰与聚合物杂质峰分离良好;主峰的线性范围为0.0005~2 mg/m L(R=0.9999),聚合物杂质峰的线性范围为0.05~2 mg/m L(R=0.998);定量限为1.47μg/m L,检测限为0.49μg/m L,进样精密度RSD为0.4%(n=10)。聚合物杂质峰面积随美罗培南溶液放置时间延长而显著增长,表明美罗培南溶液不稳定,易产生聚合物杂质,溶液必须现配现用。所建方法专属性强、耐用性好、灵敏度高,适用于美罗培南中聚合物杂质的测定。展开更多
文摘The molecular weight distribution (MWD) of dissolved organic matter (DOM) in lake waters from Lake Hongfeng was examined using high performance size exclusion chromatography (HPSEC) with UV-vis absorbance and fluorescence detection. The elution curves obtained by absorbance and fluorescence techniques expressed similar patterns, with the exception of diminishing of large fraction and the peaks behind several seconds in fluorescence chromatograms. According to its molecular weight (MW), DOM in water samples is divided into several fractions: large ({>3.5} kDa); medium-large ({3.5}-{2.0} kDa); medium ({2.0}-{1.0} kDa) and small ({<1.0} kDa). The average molecular weight was calculated using the elution curve detected by UV-vis absorbance and fluorescence detection techniques. The results showed that the weight-average molecular weight (Mw) and number-average molecular weight (Mn) calculated by UV-vis absorbance techniques range from 1750 to 2050 Dalton and from 1450 to 1850 Dalton, respectively. And the Mw and Mn obtained by fluorescence detection are lower by 50 to 400 Dalton. As a reference, the molecular weight of Fluka humic acid (FHA) is larger than that of water samples by about 200 Dalton. The average molecular weight of DOM for water samples collected in March and July was compared. The results revealed that the molecular weight is lower for water samples obtained in July than that obtained in March, indicating the ambient environment has an influence on the molecular weight, including photo-degradation and biological activity.
