固相萃取-超高效液相色谱-串联质谱法测定水中13种抗生素的含量

采用固相萃取-超高效液相色谱-串联质谱法测定水中13种抗生素的含量。水样中的抗生素富集于PLS固相萃取柱上,用甲醇洗脱,洗脱液进行LC分离,以Endeavorsil C18色谱柱为分离柱,以不同体积比的0.4%(体积分数)甲酸-水溶液和甲醇-乙腈(40+60)溶液的混合液为流动相进行梯度洗脱。质谱分析中,采用电喷雾正离子源多反应监测模式检测。13种抗生素均在一定的质量浓度范围内与其对应的峰面积呈线性关系,方法的检出限(3S/N)在0.4~1.5ng·L~(-1)之间。以空白样品为基体进行加标回收试验,所得回收率在70.4%~101%之间,测定值的相对标准偏差(n=5)在1.1%~4.8%之间。     

固相萃取-高效液相色谱-串联质谱法同时测定不同基质保健食品中10种减肥药物

采用固相萃取-高效液相色谱-串联质谱法同时测定不同基质保健食品中10种减肥药物。保健食品样品采用甲醇超声提取,经Oasis HLB固相萃取柱净化,以Zorbax-SB-C_(18)色谱柱为分离柱,以不同体积比的10mmol·L~(-1)乙酸铵-0.1%(体积分数)甲酸溶液和乙腈的混合液为流动相进行梯度洗脱,采用电喷雾正离子源多反应监测模式检测。10种减肥药物的质量浓度均在1.0~100.0μg·L~(-1)内与其对应的峰面积呈线性关系,方法的检出限(3S/N)为1.2~3.8μg·kg~(-1)。以空白样品为基体进行加标回收试验,所得回收率为79.5%~106%,测定值的相对标准偏差(n=6)为2.5%~9.7%。     

超高效液相色谱-串联质谱法测定保健食品中7种非法添加的化学镇静剂

采用固相萃取-超高效液相色谱-串联质谱法测定保健食品中7种非法添加的化学镇静剂的含量。保健食品样品以甲醇为溶剂进行提取,经高速离心处理后,取上清液,经Oasis MCX固相萃取柱净化。所得净化液以Zorbax-SB-C18色谱柱为分离柱,以不同体积比的0.1%(体积分数)甲酸溶液和乙腈混合液为流动相进行梯度洗脱,采用电喷雾正离子源多反应监测模式检测。7种化合物的质量浓度均在0.10~30.0μg·L~(-1)范围内与其峰面积呈线性关系,方法的测定下限(10S/N)在0.1~2.1μg·kg~(-1)之间。在0.30,3.0,10.0μg·L~(-1)等3个浓度水平进行加标回收试验,回收率在76.7%~104%之间,测定值的相对标准偏差(n=6)在2.1%~9.8%之间。     

超高效液相色谱-质谱法测定饮用水中14种氟喹诺酮类抗生素的残留量

采用超高效液相色谱-质谱法测定饮用水中的14种氟喹诺酮类抗生素的残留量。饮用水样品经Oasis HLB(200mg/6mL)固相萃取柱富集。柱上的浓集物用甲醇洗脱,洗脱液以Acquity UPLC BEH C_(18)色谱柱为分离柱,以不同体积比的0.1%(体积分数)甲酸溶液和0.1%(体积分数)甲酸乙腈溶液的混合液为流动相进行梯度洗脱,采用电喷雾正离子模式进行质谱检测。14种氟喹诺酮类抗生素均在一定的质量浓度范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.04~1.8ng·L~(-1)之间。以空白样品为基体进行加标回收试验,所得回收率在69.2%~85.2%之间,测定值的相对标准偏差(n=6)在4.5%~11%之间。     

超高效液相色谱-串联质谱法测定蜂蜜中甲硝唑

采用超高效液相色谱-串联质谱法测定蜂蜜中甲硝唑的含量。蜂蜜样品经磷酸氢二钾溶液溶解,乙酸乙酯提取,用MCS固相萃取柱净化。以Hypersil Gold-C_(18)色谱柱为分离柱,以不同体积比的0.1%(体积分数)甲酸溶液和乙腈混合液为流动相进行梯度洗脱,采用电喷雾正离子源多反应监测模式检测。以D4-甲硝唑为内标物。甲硝唑的线性范围为0.5~64.0μg·L~(-1),方法的测定下限(10S/N)为0.15μg·kg~(-1)。以空白样品为基体进行加标回收试验,所得回收率在95.6%~98.8%之间,测定值的相对标准偏差(n=6)在4.2%~8.3%之间。     

高效液相色谱-串联质谱法测定猪肉中9种β_2-受体激动剂残留量

采用高效液相色谱-串联质谱法测定了猪肉中9种β-受体激动剂的残留量。样品经β-葡萄糖醛苷酶/芳基硫酸酯酶酶解后加入高氯酸沉淀蛋白并离心,取上清液过PCX阳离子固相萃取小柱净化,用氨水-甲醇(5+95)混合液洗脱,氮气吹干后用乙腈定容至1 mL。以CAPCELL PAK CR色谱柱为分离柱,以10mmol·L-1乙酸铵溶液-乙腈(55+45)混合溶液(含体积分数为0.1%的甲酸)为流动相进行洗脱,采用电喷雾正离子源及选择反应监测模式进行测定,内标法进行定量。9种β-受体激动剂的质量浓度在4.00~100μg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在0.09~0.50μg·L-1之间。对空白样品进行加标回收试验,回收率在83.2%~102%之间,测定值的相对标准偏差(n=6)在5.0%~12%之间。     

超高效液相色谱-串联质谱法同时测定保健品中26种非法添加物

提出了超高效液相色谱-串联四极杆质谱法测定各类功能保健品中具有降糖、降压、利尿、减肥、壮阳、抗过敏、抗抑郁、抗疲劳等功效的26种非法添加物的快速分析方法。样品采用甲醇超声提取,提取液经固相萃取柱净化后,以Waters HSS T3超高效液相色谱柱为分离柱,以不同体积比的含2mmol·L~(-1)乙酸铵的0.1%(体积分数)甲酸溶液和乙腈混合液为流动相进行梯度洗脱,采用电喷雾正离子源多反应监测模式检测。26种非法添加物的质量分数在1.0~200μg·kg-1范围内与峰面积呈线性关系,方法的检出限(3S/N)在0.5~2.0μg·kg-1之间;测定下限(10S/N)在2.0~10μg·kg-1之间,在3个不同浓度水平上进行了回收试验,回收率在78.1%~109%之间,测定值的相对标准偏差(n=10)在7.0%~16%之间。     

高效液相色谱-串联质谱法测定牛奶中3种糖肽类抗生素

提出了高效液相色谱-串联质谱法测定牛奶中万古霉素、去甲万古霉素和替考拉宁等3种糖肽类抗生素的含量。样品经乙腈-10%(体积分数)三氯乙酸(6+4)溶液提取,同时加入硫酸铵沉淀蛋白,以HLB固相萃取柱净化。以XBridge C18色谱柱为分离柱,以不同体积比的乙腈和乙酸(0.3+99.7)溶液的混合液为流动相进行梯度洗脱,采用电喷雾正离子源多反应监测模式检测。3种化合物的质量分数在5.00~500μg·kg-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在1.0~2.0μg·kg-1之间。在5.00,10.0,20.0μg·kg-1等3个浓度水平进行加标回收试验,回收率在70.0%~83.5%之间,测定值的相对标准偏差(n=6)在4.2%~11%之间。     

固相萃取-超高效液相色谱法测定水体中4种硝基呋喃类药物

采用固相萃取-超高效液相色谱法测定水体中呋喃西林、呋喃它酮、呋喃妥因、呋喃唑酮等4种硝基呋喃类药物的含量。样品经HLB固相萃取柱净化后,用氨水-甲醇(5+95)溶液洗脱。以BEH C18色谱柱为分离柱,以乙腈和含有0.1%(体积分数)甲酸的2mmol·L-1乙酸铵溶液以体积比23比77组成的混合液为流动相,在检测波长360nm处进行测定。4种硝基呋喃类药物的质量浓度均在5.0~200μg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)为0.02μg·L-1。以空白样品为基体进行加标回收试验,所得回收率在84.5%~97.2%之间,测定值的相对标准偏差(n=6)在1.5%~4.5%之间。     

固相萃取-高效液相色谱-原子荧光光谱法联用测定水中无机汞(Ⅱ)及有机汞

采用固相萃取-高效液相色谱-原子荧光光谱法联用技术测定了水样中无机汞及有机汞。水样流经以DDTC溶液改性的C18固相萃取小柱。用含有10%(体积分数)乙腈的混合洗脱液4mL,分4次,以1~2mL·min-1流量从小柱上将3种形态的汞洗脱。收集洗脱液,混匀,过滤后通过Venusil MP C18色谱柱,用乙腈、145mmol·L-1乙酸铵溶液和20mmol·L-1半胱氨酸溶液(5+45+50)混合液作为流动相进行色谱分离。根据选定的形态分析条件,用原子荧光光谱法进行测定。汞质量浓度在0.5~20μg·L-1范围内与其峰面积呈线性关系,汞(Ⅱ)、甲基汞、乙基汞的检出限(3S/N)依次为1.6,0.5,1.2ng·L-1。加标回收率在71.2%~95.2%之间,测定值的相对标准偏差(n=6)在4.9%~10%之间。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

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.     

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%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.