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建立了液相色谱-串联质谱检测雄蜂蛹粉中50种抗生素残留(大环内酯类、喹诺酮类、磺胺类、四环素类、硝基咪唑类、林可霉素和氯霉素)的方法。样品经高氯酸溶液和醋酸铅溶液提取沉淀蛋白质,清液用磷酸氢二钾溶液调节pH值至8,经固相萃取净化后进行仪器分析。采用多反应监测正离子或负离子模式检测,可以一次完成对雄蜂蛹粉中50种目标化合物的定性和定量测定。50种抗生素的加标回收率为70.2%~118.3%,相对标准偏差(RSD)为1.8%~13.6%。该方法操作简便,灵敏度高,适用于雄蜂蛹粉中多种兽药残留的分析确证。 相似文献
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落新妇苷具有选择性免疫抑制活性,基于前药原理在落新妇苷母核上引入D-半乳糖、D-葡萄糖、D-甘露糖和D-阿拉伯糖四种天然单糖,以增加其水溶性,提高生物利用度。首先以落新妇苷为起始原料,4-二甲氨基吡啶(DMAP)催化乙酰化反应制备C-5位羟基中间体(TR-B1),其次三氟甲磺酸三甲基硅酯(TMSOTf)催化三氯乙酰亚胺酸酯糖基供体与TR-B1进行糖苷化反应,甲醇钠脱保护基制备目标化合物TR-B3-GA、TR-B3-GL、TR-B3-MA和TR-B3-Ab。溶解性实验表明目标化合物极性显著增强,水溶性从原料(AB)的微溶提高到极易溶解。 相似文献
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Single crystal Er:LuAl_3(BO_3)(Er:Lu AB) is successfully grown using the top-seeded solution growth method with a K_2Mo_3O_(10) flux. The cell parameters of the grown crystal are estimated by an x-ray single crystal diffactometor and x-ray powder diffraction analysis. The result indicates that it still belongs to the space group R32. The obtained unit-cell parameters are a= 9.2793(19) ?, c= 7.210(3) ?, V= 537.65(27) ?~3, and Z=3.The absorption spectrum is measured at room temperature. The spectroscopy properties are investigated based on the Judd–Ofelt(J-O) theory, and the effective J-O parameters were calculated to be Ω_2=8.33×10~(-20),Ω_4=3.83×10~(-20), and Ω_6 =3.55×10~(-20). The emission spectra of Er:LuAB crystal at room temperature are also studied and the ~4I_(11/2)→~4I_(13/2) fluorescence around 3170 nm is observed. The emission cross section calculated by the F-L formula is 8.6×10~(-20) cm~2. These results suggest that the Er:LuAB crystal may be a promising ~3 μm laser material. 相似文献
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研究了在超临界乙醇中、氢气存在下,一系列金属-酸双功能催化剂的酸性、孔径大小、负载的金属对热解木质素加氢裂解过程的影响.制备并采用N2等温吸附和BET比表面、X射线衍射、NH3-程序升温脱附技术对催化剂进行表征.实验结果表明催化剂酸性增强可促进热解木质素的缩聚反应,从而产生大量的焦炭和水,导致其液化效率降低.微孔催化剂比介孔催化剂孔径小,与强酸共同作用会导致热解木质素裂解生成更多的小分子气体.在催化剂上负载金属Ru可有效地抑制热解木质素的缩聚反应,促进其裂解液化. 相似文献
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Optical properties of hexagonal boron nitride thin films deposited by radio frequency bias magnetron sputtering 下载免费PDF全文
The optical properties of hexagonal boron nitride(h-BN) thin films were studied in this paper.The films were characterized by Fourier transform infrared spectroscopy,UV-visible transmittance and reflection spectra.h-BN thin films with a wide optical band gap Eg(5.86 eV for the as-deposited film and 5.97 eV for the annealed film) approaching h-BN single crystal were successfully prepared by radio frequency(RF) bias magnetron sputtering and post-deposition annealing at 970 K.The optical absorption behaviour of h-BN films accords with the typical optical absorption characteristics of amorphous materials when fitting is made by the Urbach tail model.The annealed film shows satisfactory structure stability.However,high temperature still has a significant effect on the optical absorption properties,refractive index n,and optical conductivity σ of h-BN thin films.The blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures.In addition,it is found that the refractive index clearly exhibits different trends in the visible and ultraviolet regions.Previous calculational results of optical conductivity of h-BN films are confirmed in our experimental results. 相似文献
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建立了固相萃取-高效液相色谱法同时测定蚝油、虾油、鱼露中的7种对羟基苯甲酸酯类防腐剂(对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯、对羟基苯甲酸异丙酯、对羟基苯甲酸异丁酯、对羟基苯甲酸庚酯)。样品分别用甲醇和20%甲醇水溶液超声提取,离心后经MAX固相萃取小柱富集、净化。使用Chromcore 120 C18色谱柱(150 mm×4.6 mm, 3.0μm)分离,以乙腈-5 mmol/L乙酸铵水溶液为流动相(初始流动相体积比30∶70),梯度洗脱,流速0.7 mL/min,以二极管阵列检测器检测,检测波长254 nm,柱温35℃。7种对羟基苯甲酸酯类防腐剂在0.5~50.0 mg/L内具有良好的线性关系,相关系数均大于0.999 9,检出限为0.2~0.4 mg/kg,定量限为0.5~1.3 mg/kg。选用蚝油、虾油、鱼露3种样品在3个加标水平下做加标回收试验,7种防腐剂在3种样品中的回收率较好,分别为91.0%~102%、95.5%~106%、95.0%~105%,相对标准偏差≤6.97%。利用该研究建立的检测方法对135个实际样品进行风险筛查,发现某酱油... 相似文献