祛痘化妆品中苯海拉明的高效液相色谱检测及质谱确证

建立了祛痘化妆品中苯海拉明的高效液相色谱(HPLC)分析方法及液相色谱-串联质谱(LC-MS/MS)确证方法。水剂类和膏霜类祛痘化妆品样品分别采用适宜提取溶剂超声提取,提取液离心处理后,以HPLC测定。选用Waters XTerra MS C18色谱柱(250×4.6mm,5μm),以甲醇-10mmol/L碳酸氢铵缓冲溶液(体积比78∶22,氨水调节pH至10)为流动相,等度洗脱,流速1.0mL/min,检测波长218nm,外标法定量。阳性样品采用LC-MS/MS进行确证。苯海拉明的定量限为1.0mg/kg,在低、中、高添加水平的平均回收率为88.2%~105.0%,相对标准偏差在2.8%~7.9%之间。该方法简便、准确、灵敏度高,适用于祛痘化妆品中苯海拉明的测定。     

化妆品中碘丙炔醇丁基氨甲酸酯的高效液相色谱检测及质谱确证

建立了高效液相色谱(HPLC)-二极管阵列检测器(DAD)测定化妆品中碘丙炔醇丁基氨甲酸酯的方法.化妆品样品经超声提取后,高效液相色谱-二极管阵列扫描检测,并在235 nm波长进行分析.用保留时间结合紫外光谱定性,外标法定量,并采用液相色谱-质谱法确证.碘丙炔醇丁基氨甲酸酯的回收率为92.7%～99.8%,相对标准偏差在0.8%～2.1%之间,定量限为20 mg/kg.     

化妆品中6种卤代水杨酰苯胺的高效液相色谱检测及质谱确证

建立了同时测定化妆品中6种卤代水杨酰苯胺的高效液相色谱检测方法及质谱确证方法。化妆品样品以甲醇为提取溶剂进行超声提取,提取液离心处理,取上清液经微孔滤膜过滤后进行高效液相色谱测定。采用Eclipse XDBPhenyl(4.6 mm×250 mm,5μm)色谱柱进行分离,等度洗脱,外标法定量。化妆品中6种卤代水杨酰苯胺的方法定量限为10 mg/kg,在低、中、高3个添加水平范围内平均回收率在89.4%~107.8%之间,相对标准偏差为2.1%~6.7%。对于疑似阳性样品,进一步采用高效液相色谱-串联质谱法进行确证分析。方法适用于化妆品的实际检测。     

祛痘类化妆品中3种禁用除螨剂的高效液相色谱检测及质谱确证

建立了同时测定祛痘类化妆品中3种禁用除螨剂(克霉丹、灭螨猛和克螨特)的高效液相色谱分析方法及质谱确证方法。化妆品样品以甲醇为提取溶剂进行超声提取,提取液离心处理,取上清液经微孔滤膜过滤后测定。采用Kromasil C18(4.6 mm×250 mm,5μm)色谱柱进行分离,外标法定量。祛痘类化妆品中克霉丹、灭螨猛和克螨特的方法定量限分别为0.05,0.005和0.02 mg/kg,在低、中、高3个添加水平范围内平均回收率为80.7%~110.4%,相对标准偏差为2.3%~10%。采用高效液相色谱-串联质谱法进一步确证分析,电喷雾正离子模式电离,多反应监测模式检测。该方法适用于祛痘类化妆品的实际检验工作。     

高效液相色谱法同时测定防晒类化妆品中15种紫外线吸收剂

建立了一种反相高效液相色谱同时测定防晒类化妆品中15种紫外线吸收剂的分析方法。化妆水、乳液、膏霜和蜡质样品中首先加入四氢呋喃(含2 g/L氢氧化铵),涡旋、振荡、混匀(若蜡质样品仍分散不完全,可超声振荡加热至50 ℃),再加入80%(v/v)甲醇水溶液振荡混匀、超声提取、离心、过滤后,采用XTerra MS C₁₈柱分离,经水(含0.1%(v/v)甲酸)和甲醇(含0.1%(v/v)甲酸)梯度洗脱,以二极管阵列检测器检测,检测波长为280 nm和311 nm,外标法定量。实验中对不同基质类型样品的前处理条件(样品分散溶剂、萃取溶剂和萃取时间等)进行了重点优化。结果表明,15种紫外线吸收剂在各自的线性范围内呈良好的线性关系(r²≥0.9991),方法的定量限为1.2~5.1 μg/g,在低、中、高3个添加水平下的回收率为84.2%~100.7%,相对标准偏差(RSD)为0.9%~9.5%。该分析方法分离效果好、灵敏度高、定量准确,可用于防晒类化妆品的实际检测。     

化妆品中8种呋喃香豆素的高效液相色谱法检测及质谱确证

建立了同时测定化妆品中8种呋喃香豆素类化合物(8-羟基补骨脂素、补骨脂素、异补骨脂素、8-甲氧基补骨脂素、5-甲氧基补骨脂素、三甲沙林、欧前胡素和异欧前胡素)的高效液相色谱分析方法及液相色谱-串联质谱确证方法。膏霜类、水剂类、香波类、散粉类、唇膏类等不同类型的化妆品样品分别经适宜的提取溶液进行超声提取,提取液以离心处理后,取上清液经微孔滤膜过滤后测定。采用Agilent Zorbax SB-Phenyl色谱柱(250 mm×4.6 mm, 5 μm)分离,以甲醇-乙腈-水三元流动相梯度洗脱,流速1.0 mL/min,柱温30 ℃,检测波长250 nm。8-羟基补骨脂素的定量限为0.25 mg/kg,补骨脂素、异补骨脂素、8-甲氧基补骨脂素、5-甲氧基补骨脂素、三甲沙林、欧前胡素、异欧前胡素的定量限为0.5 mg/kg。在低、中、高3种加标水平下,8种待测组分的平均回收率为85.0%～105.8%,相对标准偏差为0.41%～7.90%。采用本方法在一日内不同时间点(6个时间点,每隔1 h测定一次)和不同日期(6 d内)测定混合标准溶液,得到8个目标物峰面积的日内精密度均小于1%,日间精密度均小于2%。该方法准确、简便、快速,适用于不同类型化妆品中8种呋喃香豆素类化合物的测定。     

超高效液相色谱法测定美白、祛痘化妆品中4种禁用激素

建立了超高效液相色谱同时测定美白、祛痘化妆品中4种糖皮质激素氢化可的松、曲安奈德醋酸酯、氯倍他索丙酸酯、倍他米松双丙酸酯的方法。样品采用甲醇涡旋超声提取,色谱柱采用Waters ACQUITY UPLC BEH C18柱(100 mm×2.1 mm,1.7μm),流动相为乙腈–水溶液,梯度洗脱,流量为0.5 m L/min,用PDA检测器检测,检测波长为240 nm。方法检出限以3倍空白噪音计,氢化可的松、曲安奈德醋酸酯、氯倍他索丙酸酯、倍他米松双丙酸酯的检出浓度分别为0.12,0.18,0.30,0.30 mg/kg。在质量浓度为1.0~40.0 mg/L时,标准工作曲线相关系数r0.999 8,4种激素的回收率为85.3%~102.8%,测定结果的相对标准偏差为2.1%~5.0%(n=6)。该方法前处理简单,分离效果好,且灵敏度高,速度快,能满足美白、祛痘化妆品中4中糖皮质激素的检测需要。     

化妆品中苔黑醛和氯化苔黑醛的超高效液相色谱法测定及质谱确证

采用超高效液相色谱建立了化妆品中苔黑醛和氯化苔黑醛的分析方法,并采用液相色谱-串联质谱法进行确证。化妆品试样采用5%三氯乙酸-乙腈混合溶液(70/30,V/V)超声提取15 min,离心过膜后即可直接上机分析。采用亚二微米超高效液相色谱柱分离,外标法定量;质谱确证采用水和乙腈作为流动相梯度洗脱,电喷雾负离子模式电离,多反应监测模式检测。苔黑醛和氯化苔黑醛在0.1~50 mg/L范围内线性关系良好(线性相关系数r≥0.9990),方法的定量限为5.0 mg/kg(信噪比为10)。膏霜、乳液和香水等样品在5.0,10,25 mg/kg的添加回收率在87.4%~96.3%之间,RSD(n=6)为1.4%~4.6%。方法适用于化妆品中苔黑醛和氯化苔黑醛的检测及其含量水平的普查。     

高效液相色谱法测定化妆品中4种禁用醛酮化合物

建立了同时测定化妆品中4种禁用醛酮化合物(巴豆醛、苯乙酮、2,4-二羟基-3-甲基苯甲醛和2-亚戊基环己酮)的高效液相色谱(HPLC)分析方法。样品使用50%乙腈(体积比)溶液提取,经AQ-C18(4.6 mm×150 mm,5μm)色谱柱分离后,高效液相色谱/二极管阵列检测器检测,以保留时间和紫外吸收光谱定性,外标法定量,高效液相色谱-质谱/质谱法确证。结果表明,4种醛酮化合物在0.05~2.0 mg/L质量浓度范围内呈良好的线性关系,相关系数均不小于0.999 9;方法检出限和定量下限分别为0.5~1.0 mg/kg和1.5~3.0 mg/kg。样品加标回收率为89.0%~106.7%,相对标准偏差(RSDs,n=6)为2.0%~6.9%。该方法准确可靠,适用于化妆品中4种禁用醛酮化合物的测定。     

化妆品中甲氧基补骨脂素同分异构体的液相色谱法分离和测定

建立了用高效液相色谱(HPLC)-二极管阵列检测器(DAD)测定化妆品中两种呋喃香豆素同分异构体-8-甲氧基补骨脂素(8-MOP)和5-甲氧基补骨脂素(5-MOP)的简便方法。样品用甲醇超声提取,高速冷冻离心,经0.45μm滤膜过滤,注入高效液相色谱,用DAD进行扫描检测,并在301 nm波长进行分析。用保留时间结合紫外光谱图定性,外标法定量,并且采用液质联用(LC/MS/MS)确证。测试结果对8-MOP的回收率为87.0%~105.0%,RSD为0.41%~5.3%,检出限为5.0 mg/kg;5-MOP的回收率为88.0%~105.0%,RSD为0.33%~4.1%,检出限为5.0 mg/kg。本文用DAD同时分离和检测了化妆品中的8-MOP和5-MOP,方法可用于化妆品安全性监控。     

Enantiomer separation by CEC——Enantiomer separation by packed-capillary electrochromatography

Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography (CEC). (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclodextrin (β-CD) chiral stationary phase (CSP). Effects of voltage, pH and concentration of organic modifier on electroosmotic flow (EOF) and chiral separations were investigated systematically. Enantiomers of a neutral compound (benzoin) and a neutral drug (mephenytoin) were separated within a short time with high efficiency. Efficiency of 32 000 theoretical plates per meter and resolution (R_s) of 1.42 were achieved for enantiomers of benzoin using a βCD packed column with 6.2 cm packed length. Efficiency of 45 000 theoretical plates per meter and R_s of 3.40 were obtained for enantiomers of mephenytoin. Especially, the enantiomer separation of mephenytion was performed in just 3.4 min with R_s of 2.60. (ⅱ) 75 μm I.D. capillary was packed with octadecylsilica particles (ODS). Chiral separat     

Regioselectivity of olefin oxidation by iodosobenzene catalyzed by metalloporphyrins : control by the catalyst

The regioselectivity of the oxidation of three monosubstituted olefins, 6-phenoxyhex-1-ene, hex-1-ene and styrene, by iodosobenzene in the presence of various Fe-, Mn- or Cr-tetraaryl-porphyrins, was studied. It was found that, besides epoxides, known products from such systems, allylic alcohols and aldehydes were formed, the latter not being derived from the corresponding epoxides. The relative importance of these reactions greatly depends upon both the metal and porphyrin constituents of the catalyst. More particularly, the competition between epoxidation and allylic hydroxylation can be efficiently controlled by non-bonded interactions between the olefin and porphyrin substituents. No hydroxylation of the aromatic rings and no oxidative dealkylation of the ether function was detected.     

Glycosidase inhibition by macrolide antibiotics elucidated by STD-NMR spectroscopy

A glycosynthase approach was attempted to glycodiversify macrolide antibiotics, using DesR, a family-3 retaining beta-glucosidase involved in the self-resistance mechanism of methymycin production. STD-NMR was used to probe enzyme-substrate interactions. Analysis of competitive STD-NMR experiments between erythromycin A and a chromogenic substrate (pNP-beta-d-glucose) with the hydrolytically inactive nucleophile mutants led us to discover a family of unprecedented glycosidase inhibitors. Analysis of kinetic data with wild-type DesR determined that erythromycin is a competitive inhibitor of the glucosidase (IC50 = 2.8 +/- 0.3 microM and Ki = 2 +/- 0.2 microM) with respect to the hydrolysis of pNP-beta-d-glucose. Comparable inhibitory data was obtained for clarithromycin; however, the inhibitory effect of azithromycin was weak and no significant inhibition was observed with methymycin or d-desosamine. This report documents significant inhibition of glycosidases by macrolide antibiotics and provides insight into the design of novel glycosidase inhibitors based on the macrolactone ring of macrolide antibiotics.     

Membrane solubilization by detergent: resistance conferred by thickness

The commonly held model for membrane dissolution by detergents/surfactants requires lipid transport from the inner to the outer bilayer leaflet ('flip-flop'). Although applicable to many systems, it fails in cases where cross-bilayer transport of membrane components is suppressed. In this paper we investigate the mechanism for surfactant-induced solubilization of polymeric bilayers. To that end, we examine the dissolution of a series of increasingly thick, polymer-based vesicles (polymersomes) by a nonionic surfactant, Triton X-100, using dynamic light scattering. We find that increasing the bilayer thickness imparts better resistance to dissolution, so that the concentration required for solubilization, after a fixed amount of time, increases nearly linearly with membrane thickness. Combining our experimental data with a theoretical model, we show that the dominant mechanism for the surfactant-induced dissolution of polymeric vesicles, where polymer flip-flop across the membrane is suppressed, is the surfactant transport through the bilayer. This mechanism is different both qualitatively and quantitatively from the mechanisms by which surfactants dissolve pure lipid vesicles.     

Antibiotic recognition by binuclear metallo-beta-lactamases revealed by X-ray crystallography

Metallo-beta-lactamases are zinc-dependent enzymes responsible for resistance to beta-lactam antibiotics in a variety of host bacteria, usually Gram-negative species that act as opportunist pathogens. They hydrolyze all classes of beta-lactam antibiotics, including carbapenems, and escape the action of available beta-lactamase inhibitors. Efforts to develop effective inhibitors have been hampered by the lack of structural information regarding how these enzymes recognize and turn over beta-lactam substrates. We report here the crystal structure of the Stenotrophomonas maltophilia L1 enzyme in complex with the hydrolysis product of the 7alpha-methoxyoxacephem, moxalactam. The on-enzyme complex is a 3'-exo-methylene species generated by elimination of the 1-methyltetrazolyl-5-thiolate anion from the 3'-methyl group. Moxalactam binding to L1 involves direct interaction of the two active site zinc ions with the beta-lactam amide and C4 carboxylate, groups that are common to all beta-lactam substrates. The 7beta-[(4-hydroxyphenyl)malonyl]-amino substituent makes limited hydrophobic and hydrogen bonding contacts with the active site groove. The mode of binding provides strong evidence that a water molecule situated between the two metal ions is the most likely nucleophile in the hydrolytic reaction. These data suggest a reaction mechanism for metallo-beta-lactamases in which both metal ions contribute to catalysis by activating the bridging water/hydroxide nucleophile, polarizing the substrate amide bond for attack and stabilizing anionic nitrogen intermediates. The structure illustrates how a binuclear zinc site confers upon metallo-beta-lactamases the ability both to recognize and efficiently hydrolyze a wide variety of beta-lactam substrates.