MacKay Allison A, Canterbury Brian
Environmental Engineering Program, University of Connecticut, Storrs, 06269-2037, USA.
J Environ Qual. 2005 Oct 12;34(6):1964-71. doi: 10.2134/jeq2005.0014. Print 2005 Nov-Dec.
The sorption of oxytetracycline to metal-loaded ion exchange resin and to natural organic matter by the formation of ternary complexes between polyvalent metal cations and sorbent- and sorbate ligand groups was investigated. Oxytetracycline (OTC) sorption to Ca- and Cu-loaded Chelex-100 resin increased with increasing metal/sorbate ratio at pH 7.6 (OTC speciation: 55% zwitterion, 45% anion). Greater sorption to Cu- than Ca-loaded resin was observed, consistent with the greater stability constants of Cu with both the resin sites and with OTC. Oxytetracycline sorption to organic matter was measured at pH 5.5 (OTC speciation: 1% cation, 98% zwitterion, 1% anion). No detectable sorption was measured for cellulose or lignin sorbents that contain few metal-complexing ligand groups. Sorption to Aldrich humic acid increased from "clean" < "dirty" (no cation exchange pretreatment) < Al-amended < Fe(III)-amended clean humic acid with K(d) values of 5500, 32000, 48000, and 250000 L kg(-1) C, respectively. Calcium amendments of clean humic acid suggested that a portion of the sorbed OTC was interacting by cation exchange. Oxytetracycline sorption coefficients for all humic acid sorbents were well-correlated with the total sorbed Al-plus-Fe(III) concentrations (r(2) = 0.87, log-log plot), suggesting that sorption by ternary complex formation with humic acid is important. Results of this research indicate that organic matter may be an important sorbent phase in soils and sediments for pharmaceutical compounds that can complex metals by the formation of ternary complexes between organic matter ligand groups and pharmaceutical ligand groups.
通过多价金属阳离子与吸附剂和吸附质配体基团形成三元络合物，研究了土霉素在负载金属的离子交换树脂和天然有机物上的吸附情况。在pH 7.6时（土霉素形态：55%两性离子，45%阴离子），土霉素（OTC）在负载钙和铜的Chelex-100树脂上的吸附量随金属/吸附质比例的增加而增加。观察到土霉素在负载铜的树脂上的吸附量大于负载钙的树脂，这与铜与树脂位点和土霉素的稳定性常数更大一致。在pH 5.5时（土霉素形态：1%阳离子，98%两性离子，1%阴离子）测量了土霉素在有机物上的吸附。对于几乎不含金属络合配体基团的纤维素或木质素吸附剂，未检测到吸附。在Aldrich腐殖酸上的吸附量从“纯净”<“脏污”（无阳离子交换预处理）<铝改性<铁（III）改性的纯净腐殖酸依次增加，其分配系数K(d)值分别为5500、32000、48000和250000 L kg(-1) C。纯净腐殖酸的钙改性表明，一部分吸附的土霉素是通过阳离子交换相互作用的。所有腐殖酸吸附剂的土霉素吸附系数与总吸附的铝加铁（III）浓度具有良好的相关性（r(2) = 0.87，对数-对数图），表明通过与腐殖酸形成三元络合物进行吸附很重要。本研究结果表明，对于能够通过有机物配体基团和药物配体基团形成三元络合物来络合金属的药物化合物，有机物可能是土壤和沉积物中的重要吸附相。
