500 mL地表水样经0.45 μm滤膜过滤后,加入0.4 g乙二胺四乙酸二钠,以约2 mL·min^-1上样速率过已串联好的由混合型阳(MCX小柱)、阴(MAX小柱)离子交换反相吸附固相萃取柱。上样完毕后,将2根小柱分开。MCX小柱先用2%(体积分数,下同)甲酸溶液10 mL淋洗,再用氮气吹扫30 min,然后依次用甲醇4 mL、含5%(体积分数,下同)氨水的甲醇溶液4 mL洗脱。MAX小柱先用5%氨水溶液10 mL淋洗,再用氮气吹扫30 min,然后依次用甲醇4 mL、含2%甲酸的甲醇溶液4 mL洗脱。合并两个小柱的洗脱液,用氮气浓缩至尽干,用50%(体积分数)乙腈溶液稀释至1.0 mL,加入各内标物,使其在上述溶液中的质量浓度达到20.0 μg·L^-1,混匀后过0.22 μm滤膜,滤液进入超高效液相色谱仪,在BEH C₁₈色谱柱上以不同体积比的0.1%(体积分数)甲酸溶液-乙腈混合溶液进行梯度洗脱,分离后的四环素类、磺胺类、大环内酯类、喹诺酮类、β-内酰胺类、林可酰胺类等6类抗生素以串联质谱仪的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:32种抗生素标准曲线的线性范围为1.0~50.0 μg·L^-1,检出限(3s)为0.3~1.4 ng·L^-1;对实际地表水样品进行3个浓度水平的加标回收试验,回收率为48.5%~93.4%,测定值的相对标准偏差(n=6)为1.3%~17%。方法用于太湖流域8个水源地地表水的分析,检出了磺胺甲恶唑、磺胺间甲氧嘧啶、林可霉素、克林霉素、克拉霉素和诺氟沙星,最大检出量为33.9 ng·L^-1(林可霉素)。

The surface water sample (500 mL) was passed through a 0.45 μm filtrate membrane, and the filtrate was mixed with disodium ethylene diamine tetraacetic acid (0.4 g). The mixed cation (MCX cartridge) and anion (MAX cartridge) ion exchange reversed phase adsorption solid phase extraction columns were coupled, and loaded with the above sample solution at sampling rate of about 2 mL·min^-1. The 2 cartridges were separated after sampling, and the MCX cartridge was rinsed with 10 mL of 2% (φ, the same below) formic acid solution, dried with nitrogen for 30 min, and eluted with 4 mL of methanol and 4 mL of methanol solution containing 5% (φ, the same below) aqueous ammonia. The MAX cartridge was rinsed with 10 mL of 5% aqueous ammonia solution, dried with nitrogen for 30 min, and eluted with 4 mL of methanol and 4 mL of methanol solution containing 2% formic acid. The eluates collected from the 2 cartridges were combined, blown to nearly dry with nitrogen, and diluted to 1.0 mL with 50% (φ) acetonitrile solution. The internal standards were added, to make their mass concentrations in the above solution reach to 20.0 μg·L^-1. After mixing evenly, the mixed solution was passed through a 0.22 μm filtrate membrane, and the filtrate was introduced into the ultra-high performance liquid chromatograph. Six kinds of antibiotics (including etracyclines, sulfonamides, macrolides, quinolones β-lactams, and linkolamides) were sepatated on BEH C₁₈ column with mixed solutions composed of 0.1% (φ) formic acid solution and acetonitrile at various volume ratios under the gradient elution procedure, ionized and detected by positive electrospray ionization ion source mode and multiple reaction monitoring mode in the tandem mass spectrometer, with internal standard method as quantification method. It was shown that linear ranges of standard curves of the 32 antibiotics were in the range of 1.0-50.0 μg·L^-1, with detection limits (3s) of 0.3-1.4 ng·L^-1. The spiked recovery test was made on the actual surface water samples at the 3 concentration levels, giving values of recovery in the range of 48.5%-93.4%, and RSDs (n=6) of the determined values ranged from 1.3% to 17%. The proposed method was applied to the analysis of the 8 surface water sources in the Taihu lake basin, in which sulfamethoxazole, sulfamethoxam, lincomycin, clindamycin, clarithromycin, and norfloxacin were detected, and the maximum detection amount was 33.9 ng·L^-1 (lincomycin).