3 結(jié)果與討論
3.1 實驗條件優(yōu)化
3.1.1 液相色譜條件的優(yōu)化 GB/T 219812008中僅用BEH C18柱分離各化合物,雖可獲得較好效果,但對雌激素中個別化合物保留弱,干擾較大;對α玉米赤霉醇和β玉米赤
圖2 樣品(a)及加標(biāo)樣品(b)中己二烯雌酚的質(zhì)譜色譜圖
Fig.2 Chromatograms of dienestrol in sample (a) and spiked sample (b)霉醇的分離較差。本研究選用HSS T3柱分離雄激素、孕激素、玉米赤霉醇和玉米赤霉酮,用Shield RP18柱分離雌激素。Shield柱對雌激素有較強保留,有效避免了雜質(zhì)的干擾(見圖2) \\3.1.2 凈化條件的優(yōu)化 GB/T 219812008中使用NH3和ENVICarb雙柱串聯(lián)凈化和富集樣品,雙柱串聯(lián)上樣速度較慢,且易堵塞,因而處理費時且重現(xiàn)性不佳。本研究僅用HLB柱進行凈化與富集,上樣速度快,用酸、堿、10%甲醇淋洗后,凈化效果好,保證了方法的重現(xiàn)性和準(zhǔn)確性,且費用低。兩方法的比較結(jié)果見圖3。部分化合物HLB的凈化效果明顯優(yōu)于雙柱聯(lián)用,尤其為孕二烯酮;其它化合物凈化效果相近。
圖3 凈化效果比較
Fig.3 Comparison of cleanup effect for seven compounds
a. 7種化合物凈化效果信噪比比較圖(Comparison of cleanup effect for seven compounds by signal to noise values); b. 孕二烯酮色譜圖(Chromatogram for gestodene)。
3.2 基質(zhì)效應(yīng)的評估
當(dāng)基質(zhì)效應(yīng)影響很大時,即使采用同位素內(nèi)標(biāo)也無法克服基質(zhì)干擾[9,10]。為考證基質(zhì)效應(yīng)對本方法結(jié)果的影響,用空白試樣基質(zhì)溶液和溶劑分別配制相同濃度的標(biāo)準(zhǔn),上機進樣比較,樣品經(jīng)本方法提取和凈化后,基質(zhì)效應(yīng)影響較小(圖4),在2%~32%之間,再用內(nèi)標(biāo)法計算,檢測結(jié)果更準(zhǔn)確[11]。
圖4 基質(zhì)效應(yīng)評估 (序號同表1)
Fig.4 Assessment of matrix effect. (Numbers of endogenous are the same as Table 1)
3.3 方法的評價
3.3.1 線性關(guān)系 取儲備液,用乙腈水(1∶1,V/V)配制成濃度分別為0.1, 0.5, 1.0, 2.5, 5.0 , 10, 20和50
3.4 實際樣品分析
對120個樣品進行了檢測,包括不同品牌的47個奶粉樣品、不同牛群不同階段的32個牛乳樣品和不同人群不同階段的41個人乳樣品。其中,101個樣品檢出孕酮,31個樣品檢出雌酮,26個樣品檢出雌三醇,未檢出外源性性激素。
實驗結(jié)果表明, 本方法操作簡便、凈化效果好;運用同位素內(nèi)標(biāo)校正,有效克服基質(zhì)效應(yīng)的影響,適用于日常乳及乳制樣品的檢測。
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Determination of 29 Kinds of Estrogens in Milk and Milk Products by
Liquid Chromatography Tandem Mass Spectrometry
LAI ShiYun2, TAO BaoHua2, FU ShiShan2, HE GuangHua2, WEI Ying2, ZHANG JingShun3, REN YiPing*1
1(Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou 310051)
2(Zhejiang Beingmate Rresearch Institute, Hangzhou 310057)
3(Zhejiang University, Hangzhou 310057)
Abstract A method was developed for the determination of 29 kinds of estrogens in milk and milk products by liquid chromatography tandem mass spectrometry. The sample was deposited protein with acetonitrile and extracted with ethyl acetate. then passed through HLB cartridge to clearup. The test potion was separated by Shield RP18 and HSS T3 columns with gradient elution program and the results were calculated by internal standard method. the LODs were 0.1-0.5