固相萃取-高效液相色谱法检测牛奶和猪肉中5种β-内酰胺类抗生素

建立了牛奶和猪肉样品中氨苄西林、青霉素V、青霉素G、苯唑西林和氯唑西林等5种β-内酰胺类抗生素残留量的高效液相色谱(HPLC)测定方法。实验采用固相萃取法(SPE)富集抗生素残留,考察了样品前处理方法;并对色谱分离条件加以优化,在C18色谱柱上以乙腈-0.1%氨水进行梯度洗脱,可在10min内实现5种抗生素的分离与检测,检测波长为210nm。方法可用于动物性食品中上述抗生素残留的同时检测。     

高效液相色谱-串联质谱法同时测定牛奶和奶粉中的青霉素类药物及其主要酶解代谢产物

建立了液相色谱-串联质谱法同时测定牛奶和奶粉中4种青霉素(青霉素G、青霉素V、阿莫西林、氨苄西林)及其4种 β-内酰胺酶酶解产物(青霉素G脱羧噻唑酸、青霉素V脱羧噻唑酸、阿莫西林脱羧噻唑酸、氨苄西林脱羧噻唑酸)残留的方法。样品采用乙腈-水提取,浓缩后经HLB柱净化,用液相色谱-串联质谱检测,外标法定量。结果表明,青霉素原药在4~200 μg/L,酶解产物在10~500 μg/L范围呈良好线性,线性相关系数均大于0.99;样品检出限为5~50 μg/kg(S/N≥3),定量限为8~100 μg/kg(S/N≥10);对牛奶和奶粉样品分别进行3个水平的加标回收实验(n=6),牛奶中青霉素及其酶解产物的平均回收率为83.48%~96.97%,相对标准偏差为3.86%~10.87%;奶粉中青霉素及其酶解产物的平均回收率为82.70%~95.14%,相对标准偏差为3.02%~9.81%。该方法稳定、可靠,适用于牛奶和奶粉中青霉素类药物及其酶解代谢产物的测定。     

固相萃取-胶束电动色谱法测定牛奶中的4种β-内酰胺类抗生素

建立了同时分离检测牛奶中的氨苄西林、阿莫西林、青霉素V和头孢氨苄4种β-内酰胺类抗生素的固相萃取-胶束电动色谱法。牛奶样品经沉淀蛋白后,采用HLB固相萃取柱净化浓缩;以含十二烷基硫酸钠(SDS)的磷酸盐为缓冲液,胶束电动色谱分离,210 nm波长下检测。分离电压为18 kV,于9 min内达到基线分离。各组分在0.5～20 mg/L范围内呈良好的线性关系,相关系数(r2)为0.9943～0.9976;检出限为0.16～0.20 mg/L;除了阿莫西林外,回收率均大于70%。该方法准确可靠,重复性好,灵敏度高,可以用于牛奶中β-内酰胺类抗生素的定量检测。     

食用菌中多菌灵残留的分散固相萃取/高效液相色谱法测定

建立了食用菌中多菌灵残留量的测定方法.采用乙腈提取样品,提取液经十八烷基硅烷(ODS)和乙二胺-N-丙基硅烷(PSA)吸附净化后,采用反相高效液相色谱-紫外可见检测器进行测定,外标法定量.色谱条件:色谱柱为Agilent Eclipse XDB C18柱(4.6 mm×150 mm,5 μm,i.d.),流动相为甲醇-0.02 mol/L磷酸盐缓冲溶液(pH 7.4)(体积比25 ∶ 75),流速1 mL/min,柱温30 ℃,检测波长282 nm.结果表明,多菌灵在0.05 ～10 mg/L质量浓度范围内线性良好,相关系数为0.999 9;方法的相对标准偏差(RSD)不大于3.4%,添加回收率为81% ～98%;多菌灵在食用菌中的检出限(LOD)和定量下限(LOQ)分别为0.03、0.10 mg/kg.该方法操作简单快速、准确度高,能够满足多菌灵残留限量标准的检测要求.     

液相色谱-串联质谱法测定牛奶中35种四环素类、磺胺类、青霉素类、大环内酯类、氯霉素类抗生素残留

建立了液相色谱-质谱测定牛奶中35种四环素类、磺胺类、青霉素类、大环内酯类、氯霉素类等5类抗生素残留的检测方法。样品经碱性乙腈-Mcllvaine缓冲液超声提取,用Eclipse XDB-C₈色谱柱(150 mm×2.1 mm, 3.5 μm)分离,梯度洗脱,流速0.25 mL/min,进样量10 μL,采用多反应监测正离子或负离子模式,可以一次性对牛奶中的目标化合物进行定性和定量测定。在优化条件下,35种化合物的检出限均低于10.0 μg/kg,方法回收率为70.1%~109.9%,相对标准偏差(RSD)为2.89%~9.99%。结果表明该方法适用于牛奶中抗生素残留的检测。采用所建立的检测方法对市售的50种不同乳品进行了检测,其中一个样品检出氯霉素含量为0.48 μg/kg。检测结果表明,中国市场上销售的乳品氯霉素污染的风险仍然存在。本研究建立的液相色谱-质谱联用方法实现了牛奶中35种四环素类、磺胺类、青霉素类、大环内酯类、氯霉素类等5类抗生素残留的测定。该方法简单、快捷、经济,可实现多种抗生素残留的快速测定。     

高效液相色谱法测定牛奶中的氯霉素残留

建立牛奶中氯霉素残留的高效液相色谱测定方法。牛奶样品用乙腈提取,超声离心后采用液相色谱柱分离,外标法定量。色谱条件:Agilent ZORBAX SB-C18柱(4.6mm×250mm,5μm),流动相:甲醇-水(40∶60,V/V),波长:278nm,流速0.8mL.min-1。线性范围为0.1～10.0 mg·L-1,相关系数R2为0.9995,最低检测限为0.009 mg·L-1。平均回收率在93.0%～97.3%之间,相对标准偏差在3.67%～5.25%之间(n=6),该方法简便、准确,适用于牛奶中氯霉素的检测。     

LC-MS/MS法检测牛奶中14种β-内酰胺类抗生素残留

采用超高效液相色谱串联质谱建立了牛奶中14种β-内酰胺类抗生素残留检测方法。样品经过乙腈提取、氮吹、HLB柱净化后,经Acquity UPLC BEH Shield RP18(100 mm×2.1 mm,1.7μm)分离,以乙腈和体积分数0.02%甲酸溶液为流动相进行梯度洗脱,14种化合物在8 min内分离效果良好。方法的定量限均低于2.5μg/L,在2.5~250μg/L范围内线性良好,相关系数均在0.99以上;通过2,10,100μg/L 3个浓度的加标回收实验表明,回收率为73.2%~109.8%,RSD%为1.5%~12%,方法满足牛奶中β-内酰胺类抗生素药物残留检测要求。     

固相萃取/反相高效液相色谱法对血清中胰岛素的测定

采用固相萃取纯化血清样品,荧光胺柱前衍生,建立了反相高效液相色谱/荧光检测血清中胰岛素的方法.色谱条件:LunaC5柱(100 mm×4.6 mm,5 μm)分离,流动相为乙腈-Tris缓冲溶液(10 mmol/L,pH 8.5)梯度洗脱,流速:1 mL/min.激发波长(λex)273 nm,发射波长(λem)476 nm,进样量20 μL.结果表明:胰岛素在10 ～800 μg/L范围内峰面积和质量浓度呈良好的线性关系,相关系数r为0.997 1;检出限为5 μg/L.日内、日间精密度分别为1.5%、1.0%,回收率为92%.     

凝胶柱净化-高效液相色谱检测食品中的苏丹红

建立了凝胶柱净化-高效液相色谱同时检测食品中苏丹红Ⅰ,Ⅱ,Ⅲ和Ⅳ的方法。样品用乙醇提取,提取液经Bio-Beads SX3凝胶柱(200 mm×10 mm i.d.)净化,用环己烷-乙酸乙酯(体积比为1∶1)洗脱。采用Symmetry Shield RP18柱(250 mm×4.6 mm i.d.,　5　μm)分离,以100%甲醇为流动相,流速1.5 mL/min;用二极管阵列检测器检测,检测波长478 nm。上述4种苏丹红组分在其质量浓度为0.1~10.0 mg/L时有良好的线性关系(r>0.999),方法的检测限为7~14 μg/kg;平均加标回收率为80.7%~96.3%(添加水平为0.25,2.5 mg/kg),相对标准偏差为2.4%~5.9%。方法灵敏可靠,能满足食品中苏丹红检测的需要。     

超高效液相色谱-串联质谱法测定水产品中三聚氰胺残留量

建立超高效液相色谱-串联质谱(UPLC-MS/MS)快速测定水产品中三聚氰胺残留的方法.采用ACQUITY UPLC BEH HILIC色谱柱(100 mm×2.1 mm, 1.7 μm),流动相为乙腈-0.5 mmol/L乙酸铵溶液(0.1%甲酸),流速为0.3 mL/min.采用电喷雾质谱检测,以正离子模式5 min完成质谱分析.实验结果表明,三聚氰胺在水产品中的检测限为0.05 mg/kg,在0.05～0.50 mg/kg添加水平时的加标回收率为63%～90%,测定结果的相对标准偏差均小于7.2%(n=6).     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.