四環黴素類抗生素 (tetracyclines) 由於具有廣泛的抗菌能力及價格低廉，常添加於飼料或是用於治療產食性動物 (food-producing animal) 之感染性疾病。本方法利用超高效液相層析搭配串聯質譜儀 (ultra performance liquidchromatography/tandem mass spectrometry, UPLC/MS/MS) 檢測四環黴素 (tetracycline)、羥四環黴素(oxytetracycline)、氯四環黴素 (chlortetracycline)、脫氧羥四環黴素(doxycycline) 與三種四環黴素類抗生素之同分異構物4-epimertetracycline、4-epimer-oxytetracycline、4-epimer-chlortetracycline，於肌肉、乳品、內臟等基質中可成功分離出四環黴素類抗生素及其同分異構物。樣品經MacIlvaine緩衝溶液 (pH 4.0) 萃取後，通過經活化後之Oasis HLB(hydrophilic-lipophilic balance) 固相萃取匣淨化，選用Waters Acquity CSH C18層析管柱，搭配含0.1%甲酸之乙腈及0.1%甲酸水溶液進行分析。試驗結果於雞肉、豬肉、魚肉、牛乳、羊乳、豬肝及豬腎平均回收率分別為50.8-95.6%，定量極限為肉品5 ppb、乳品5 ppb與內臟15 ppb，變異係數則為11%以下，本方法具有可靈敏且快速的同時檢測四環黴素類抗生素及其四差向同分異構物之優點。

Tetracyclines (TCs) are commonly used antibiotics both for the treatment of infectious diseases and as an additive to animal feeds for their broad-spectrum antibacterial activity and cost effectiveness. We used a method combining liquid chromatography tandem mass spectrometry (LC/MS/MS) positive electrospray ionization to identify tetracyclines and their 4-epimer derivatives in edible tissues, porcine liver, porcine kidney and fresh milk. Extraction of those drugs was primarily performed using a liquid extraction with MacIlvaine buffer followed by cleaning up with OASIS hydrophilic lipophilic balance (HLB) cartridge. The chromatography was carried out on a Waters Acquity CSH C18 column, as the mobile phase components. A and B were water with 0.1% formic acid and acetonitrile with 0.1% formic acid, respectively. The overall average recoveries were 50.8-95.6% in edible tissue of chicken, pork, fish, cow milk, sheep milk, liver and kidney. The coefficients of variation were below 11% and the quantification limits for all antibiotics are 5, 5 and 15 ppb in edible muscle, milk and internal organs, respectively. This method is considered a sensitive and rapid mean to determine tetracyclines and 4-epimer derivatives in edible muscle, daily milk and porcine internal organs.