超高效液相色谱法测定食品中5种人工合成甜味剂

提出了超高效液相色谱法测定食品中5种人工合成甜味剂安赛蜜、糖精钠、阿斯巴甜、甘素和纽甜含量的方法。详细叙述了不同样品的前处理方法,以MN NUCLEODUR C18Pyramid(3mm×250mm,5.0μm)色谱柱为固定相,以不同体积比混合的pH 6.0的5.0mmol.L-1乙酸-乙酸铵缓冲溶液和甲醇为流动相进行梯度洗脱,采用二极管阵列检测器于波长235nm处进行测定。5种甜味剂的质量浓度分别在一定的范围内与峰面积呈线性关系,安赛蜜、糖精钠、阿斯巴甜、甘素和纽甜的检出限(3S/N)依次为0.476,0.005,3.590,0.002,219.9mg.L-1。加标回收率在75.0%～104%之间;测定值的相对标准偏差(n=5)在0.3%～7.2%之间。     

乳及乳制品中多种防腐剂和甜味剂的同时测定

建立了高效液相色谱法同时测定乳及乳制品中安赛蜜、苯甲酸、糖精钠、山梨酸和阿斯巴甜的方法。通过加入适量沉淀剂除去样品中绝大部分蛋白质后,采用C18色谱柱分离,以甲醇-0.05 mol/L磷酸二氢钾溶液为流动相梯度洗脱,用二极管阵列检测器于230 nm波长处检测安赛蜜、苯甲酸和山梨酸,于210 nm波长处检测糖精钠和阿斯巴甜。被测物的回收率为96.0%～103.5%,精密度(以相对标准偏差(RSD)计)为1.93%～2.76%,安赛蜜、苯甲酸、糖精钠、山梨酸和阿斯巴甜的检出限分别为1.0, 1.0, 0.5, 1.0, 1.5 μg/g。该方法可用于乳及乳制品中这5种添加剂的同时测定。     

反相高效液相色谱法测定食品中防腐剂和甜味剂

建立了高效液相色谱法测定食品中苯甲酸、山梨酸、安赛蜜、糖精钠和阿斯巴甜含量的方法.试验采用ODS-3色谱柱,以乙腈-20 mmol·L-1磷酸二氢钾溶液为流动相梯度洗脱,用紫外检测器于210 nm波长处检测糖精钠和阿斯巴甜,于230 nm波长处检测另外3种化合物.结果表明:当各个组分的质量浓度在10～200 mg·L-1范围内,质量浓度与峰面积呈线性关系.对5种化合物的测定作了精密度及回收率试验,所得结果在文中详述.     

5种甜味添加剂的反相高效液相色谱法同时测定

建立了同时测定5种人工合成甜味剂阿斯巴甜、糖精钠、甜蜜素、安赛蜜、纽甜的反相高效液相色谱分析方法.以Synergi Fusion-RP柱为分离柱,20mmol/L硫酸铵缓冲溶液(pH 4.4)-乙腈为流动相,梯度洗脱.采用二极管阵列检测器进行检测,整个分离过程在9min内完成.样品加标回收率为89%～107%;相对标准偏差小于3.2%.该法可用于食品和饮料中5种甜味剂的同时测定.     

高效液相色谱-串联质谱法测定食品中6种人工合成甜味剂

建立了食品中6种人工合成甜味剂(甜蜜素、糖精钠、安赛蜜、阿斯巴甜、阿力甜、纽甜)的高效液相色谱-串联质谱检测方法。样品经甲醇-水溶液(1:1, v/v)提取,以C18柱为分离柱,0.1%(v/v)甲酸-5 mmol/L甲酸铵溶液/乙腈为流动相,经高效液相色谱分离,采用电喷雾串联四极杆质谱进行检测。结果表明,6种人工合成甜味剂在20～500 μg/L范围内定量离子对的响应峰面积和样品质量浓度之间有良好的线性关系(相关系数＞0.998)。在3个添加水平下,样品平均回收率为81.3%～106.0%,相对标准偏差小于11%。该方法简单、灵敏、准确,可用于食品中6种人工合成甜味剂的同时检测。     

液相色谱-串联质谱法同时测定调制乳制品中5种人工合成甜味剂

建立了调制乳制品中安赛蜜、甜蜜素、糖精钠、阿斯巴甜和纽甜等5种人工合成甜味剂的液相色谱-串联质谱测定方法。对蛋白沉淀剂、色谱柱、流动相组成、超声时间以及质谱参数进行了优化。结果表明,样品经过0.2%乙酸水沉淀蛋白,MGⅢ-C18色谱柱(150 mm×2.0 mm,5μm)分离,甲醇和10 mmol/L乙酸铵水溶液流动相进行梯度洗脱,流速0.3 m L/min,采用液相色谱-串联质谱仪对目标化合物进行测定,基质外标法定量。在10~1020μg/kg范围内,线性相关系数(R2)0.999,3个不同浓度添加水平下平均加标回收率90.0%~109.7%,精密度(RSD)为0.8%~7.6%(n=6)。调制乳制品中安赛蜜、甜蜜素、糖精钠、阿斯巴甜和纽甜的检出限分别为3.0,30,10,5和1.0μg/kg,定量限为10,100,40,20和3.3μg/kg。采用所建立的方法对市面上销售的8种调制乳中5种人工合成甜味剂进行筛查,达到预期效果。方法适用于调制乳制品中人工合成甜味剂的快速分析。     

UHPLC-MS/MS法同时测定水果中的7种人工甜味剂

建立了同时测定水果中7种人工甜味剂的超高效液相色谱-串联质谱法。样品经纯水超声提取,经离心沉淀残渣,以Waters CORTECDT3(2.7μm,2.1 mm×100 mm)色谱柱分离,0.1%甲酸水-乙腈作为流动相梯度洗脱,电喷雾负离子模式(ESI-)电离,多反应监测(MRM)测定,外标法定量。结果表明:三氯蔗糖在5～500 ng/mL范围内,安赛蜜、甜蜜素、糖精钠、阿斯巴甜、阿力甜、纽甜在1～100 ng/mL范围内呈良好的线性关系,相关系数r≥0.998,在4个不同浓度添加水平下,平均加标回收率为79.0%～111.4%,RSDs为0.3%～8.8%,检出限为0.26～25μg/kg,定量限为2.2～85μg/kg。该方法适用于大批量水果中7种人工甜味剂的快速筛查及定量。     

饮料中4种人工合成甜昧剂同时测定的超高效液相色谱快速检测方法

建立了采用超高效液相色谱同时测定饮料中4种甜味剂(安赛蜜、糖精钠、甜味素、纽甜)的方法.样品经简单的预处理后,通过ACQUITY UPLCTM BEH C18色谱柱分离,以乙腈-20 mmol/L磷酸二氢钠水溶液为流动相进行梯度洗脱,于220 nm波长下紫外检测.一次进样分析仅需6 min.4种甜味剂在0.5～20.0 mg/L范围内的线性关系良好,在加标水平为1,10和20 mg/L时,被测物的回收率为80.5%～95.2%,相对标准偏差为0.50%～8.7%.     

超高效液相色谱-串联质谱法测定饮品中7种人工合成甜味剂

建立了超高效液相色谱-串联质谱(UPLC-MS/MS)同时测定饮品中安赛蜜、糖精钠、甜蜜素、阿斯巴甜、阿力甜、纽甜、三氯蔗糖的分析方法,对白酒、葡萄酒、果汁3种样品进行了分析.样品经稀释后,13 000 r/min高速离心10 min,以5 mmol/L甲酸铵缓冲溶液/甲醇为流动相,梯度洗脱.在优选条件下,方法线性范围为10~500μg/L,线性相关系数R2不低于0.998 1,检出限(S/N=3)为0.003~8μg/L,样品回收率为77.10%~118.94%,7种化合物测定结果的相对标准偏差(RSD)为0.19%~5.24%.方法操作简便,灵敏度高,适用于3种基质中7种人工合成甜味剂的快速检测.     

高效液相色谱-串联质谱法测定葡萄酒中的5种人工合成甜味剂

建立了测定葡萄酒中安赛蜜、糖精钠、甜蜜素、阿斯巴甜和纽甜等5种人工合成甜味剂的高效液相色谱-电喷雾电离串联质谱(HPLC-ESI MS/MS)分析方法。采用Ultimate C18色谱柱,对流动相的组成、柱温以及质谱的各种参数进行了优化和探讨。结果表明,以含0.1%(体积分数)甲酸的20 mmol/L甲酸铵缓冲液(pH 3.8)和甲醇为流动相,梯度洗脱,柱温为45 ℃下,可以在5 min内完成5种人工合成甜味剂的基线分离。在ESI负离子模式下,采用多反应监测模式进行测定时,安赛蜜、糖精钠、甜蜜素、阿斯巴甜和纽甜的检出限分别为0.6、5、1、0.8和0.2 μg/L,回收率为87.2%～103%,相对标准偏差不高于1.2%。该方法快捷、准确,灵敏度高,可用于葡萄酒及其他复杂基质食品中低剂量、复合甜味剂的测定。     

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%.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.