通过优化样品保存、前处理、仪器工作条件,提出题示方法测定环境水体中脱水红霉素、罗红霉素、螺旋霉素、吉他霉素、克拉霉素、竹桃霉素、阿奇霉素,泰乐霉素、替米考星、交沙霉素等10种大环内酯类抗生素的含量。取1.0 L水样,添加50 m L...通过优化样品保存、前处理、仪器工作条件,提出题示方法测定环境水体中脱水红霉素、罗红霉素、螺旋霉素、吉他霉素、克拉霉素、竹桃霉素、阿奇霉素,泰乐霉素、替米考星、交沙霉素等10种大环内酯类抗生素的含量。取1.0 L水样,添加50 m L甲醇,用0.45μm玻璃纤维滤膜抽滤,收集滤液,于4℃保存,2 d内完成测定。分取500 m L水样,用50%(体积分数)盐酸溶液调节水样酸度至p H 2.0~3.0,加入25μL 2 mg·L^(-1)阿奇霉素-d_(3)、罗红霉素-d_(7)的混合替代内标溶液和25 m L乙醇,混合均匀。取500 m L处理好的水样以流量5~10 m L·min^(-1)过活化好的HLB固相萃取柱。用5 m L水淋洗,并用氮气吹扫柱子30 min,再依次用5 m L甲醇、5 m L含0.1%(体积分数)甲酸的甲醇溶液在2 m L·min^(-1)流量下洗脱柱子。收集洗脱液,于35℃氮吹至近干,加入2 mg·L^(-1)克拉霉素-d_(3)内标溶液25.0μL,用体积比80∶20的0.05%(体积分数,下同)甲酸溶液和乙腈的混合溶液稀释至1.0 m L,经0.22μm有机滤膜过滤后采用超高效液相色谱-串联质谱法测定。在色谱分析中,以Eclipse Plus C_(18)色谱柱作为固定相,不同体积比的0.05%甲酸溶液和乙腈的混合溶液作为流动相进行梯度洗脱;在质谱分析中,以电喷雾离子源正离子模式电离,多反应监测模式检测,内标法定量。结果显示:10种目标物的线性范围均为1.0~100μg·L^(-1),检出限(3.143s)为0.4~1.0 ng·L^(-1);按照标准加入法进行回收试验,回收率为58.4%~100%,测定值的相对标准偏差(n=6)为3.2%~20%。方法用于不同来源环境水体的分析,均检出了大环内酯类抗生素,检出量不超过140 ng·L^(-1)。展开更多
In this work,we present a new mechanism for designing phase-gradient metasurfaces(PGMs)to control an electromagnetic wavefront with high efficiency.Specifically,we design a transmission-type PGM,formed by a periodic s...In this work,we present a new mechanism for designing phase-gradient metasurfaces(PGMs)to control an electromagnetic wavefront with high efficiency.Specifically,we design a transmission-type PGM,formed by a periodic subwavelength metallic slit array filled with identical dielectrics of different heights.It is found that when Fabry-Perot(FP)resonances occur locally inside the dielectric regions,in addition to the common phenomenon of complete transmission,the transmitted phase differences between two adjacent slits are exactly the same,being a nonzero constant.These local FP resonances ensure total phase shift across a supercell,fully covering a range of 0 to 2π,satisfying the design requirements of PGMs.Further research reveals that,due to local FP resonances,there is a one-to-one correspondence between the phase difference and the permittivity of the filled dielectric.A similar approach can be extended to the reflection-type case and other wavefront transformations,creating new opportunities for wave manipulation.展开更多
文摘通过优化样品保存、前处理、仪器工作条件,提出题示方法测定环境水体中脱水红霉素、罗红霉素、螺旋霉素、吉他霉素、克拉霉素、竹桃霉素、阿奇霉素,泰乐霉素、替米考星、交沙霉素等10种大环内酯类抗生素的含量。取1.0 L水样,添加50 m L甲醇,用0.45μm玻璃纤维滤膜抽滤,收集滤液,于4℃保存,2 d内完成测定。分取500 m L水样,用50%(体积分数)盐酸溶液调节水样酸度至p H 2.0~3.0,加入25μL 2 mg·L^(-1)阿奇霉素-d_(3)、罗红霉素-d_(7)的混合替代内标溶液和25 m L乙醇,混合均匀。取500 m L处理好的水样以流量5~10 m L·min^(-1)过活化好的HLB固相萃取柱。用5 m L水淋洗,并用氮气吹扫柱子30 min,再依次用5 m L甲醇、5 m L含0.1%(体积分数)甲酸的甲醇溶液在2 m L·min^(-1)流量下洗脱柱子。收集洗脱液,于35℃氮吹至近干,加入2 mg·L^(-1)克拉霉素-d_(3)内标溶液25.0μL,用体积比80∶20的0.05%(体积分数,下同)甲酸溶液和乙腈的混合溶液稀释至1.0 m L,经0.22μm有机滤膜过滤后采用超高效液相色谱-串联质谱法测定。在色谱分析中,以Eclipse Plus C_(18)色谱柱作为固定相,不同体积比的0.05%甲酸溶液和乙腈的混合溶液作为流动相进行梯度洗脱;在质谱分析中,以电喷雾离子源正离子模式电离,多反应监测模式检测,内标法定量。结果显示:10种目标物的线性范围均为1.0~100μg·L^(-1),检出限(3.143s)为0.4~1.0 ng·L^(-1);按照标准加入法进行回收试验,回收率为58.4%~100%,测定值的相对标准偏差(n=6)为3.2%~20%。方法用于不同来源环境水体的分析,均检出了大环内酯类抗生素,检出量不超过140 ng·L^(-1)。
基金Supported by the National Natural Science Foundation of China(Grant Nos.11974010,11604229 and 11774252)the Natural Science Foundation of Jiangsu Province(Grant Nos.BK20161210 and BK20171206)+2 种基金the China Postdoctoral Science Foundation(Grant No.2018T110540)the Qinglan Project of Jiangsu Province of China(Grant No.BRA2015353)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions。
文摘In this work,we present a new mechanism for designing phase-gradient metasurfaces(PGMs)to control an electromagnetic wavefront with high efficiency.Specifically,we design a transmission-type PGM,formed by a periodic subwavelength metallic slit array filled with identical dielectrics of different heights.It is found that when Fabry-Perot(FP)resonances occur locally inside the dielectric regions,in addition to the common phenomenon of complete transmission,the transmitted phase differences between two adjacent slits are exactly the same,being a nonzero constant.These local FP resonances ensure total phase shift across a supercell,fully covering a range of 0 to 2π,satisfying the design requirements of PGMs.Further research reveals that,due to local FP resonances,there is a one-to-one correspondence between the phase difference and the permittivity of the filled dielectric.A similar approach can be extended to the reflection-type case and other wavefront transformations,creating new opportunities for wave manipulation.
