顶空进样GC-SIM-MS测定硝唑尼特中溶剂残留甲醇含量

利用气相色谱-选择离子监测质谱联用仪(GC-SIM-MS)测定硝唑尼特样品中溶剂残留甲醇的含量,顶空进样,温度为70℃,时间为20 min.SIM定量离子m/z 32,参考离子m/z 31,30和29.甲醇质量浓度在0.5~100μg/m L内呈良好的线性(R~2=0.999 92).方法相对标准偏差为2.49%~4.85%,样品加标回收在94.5%~102.8%之间,检测限为0.5μg/m L,符合定量分析的要求.     

气相色谱法测定虾中有机氯农药和多氯联苯残留量

建立了气相色谱法检测虾中12种有机氯农药(OCPs)和7种多氯联苯(PCBs)残留的方法。捣碎匀浆后的样品采用正己烷/二氯甲烷提取,H2SO4(浓)净化,气相色谱仪电子捕获检测器进行分析测定。有机氯农药和多氯联苯的定量限为0.3~1.5μg/kg;在虾中2,10,20μg/kg添加水平的平均回收率为70.6%~102%,相对标准偏差为2.4%~6.2%。方法适用于虾中有机氯农药和多氯联苯的定性定量分析。     

高效液相色谱-串联质谱法对家畜尿液中苯乙醇胺A残留检测研究

建立了高效液相色谱-串联质谱(HPLC-MS/MS)检测猪尿、牛尿和羊尿中苯乙醇胺A残留的方法。尿液经酶解、加入内标物、乙酸乙酯萃取、MCX固相萃取柱净化后,供HPLC-MS/MS检测。采用电喷雾离子源正模式,在多反应检测(MRM)模式下分析,苯乙醇胺A定性离子对分别为m/z 345/150和345/327,定量离子对为m/z 345/327;苯乙醇胺A内标物定性离子对为m/z 348/330,定量离子对为m/z 348/330。苯乙醇胺A含量在0～50.0μg/L范围内的线性关系良好(R2=0.9990);检出限为0.03μg/L,定量限为0.1μg/L。在猪尿、牛尿和羊尿中的回收率分别78.4%～82.9%,85.7%～93.3%和79.8%～84.9%;相对标准偏差分别为0.8%～4.2%,1.6%～5.6%和2.9%～5.8%。     

动物肌肉组织中己烯雌酚残留量的液相色谱-串联质谱法测定

建立了动物肌肉组织中己烯雌酚残留的液相色谱-串联质谱分析方法。样品用乙腈-甲酸溶液均质提取,以乙腈-水(体积比85∶15)为流动相经反相色谱柱分离后,采用多反应监测(MRM)负离子模式检测,定性离子对为m/z266.9/237.0和266.9/251.0;其中m/z266.9/251.0用于外标法定量。空白样品及其加标实验结果表明,特征离子相对强度比值稳定,无基质干扰,结合保留时间可实现准确的定性定量,方法检出限为0.10μg/kg(S/N=3),不同肌肉基质样本添加水平在0.5~5.0μg/kg时,平均回收率为82%~96%,相对标准偏差(n=6)为3.7%~6.4%。     

顶空固相微萃取-气质联用法检测尿液中的曲马多

建立尿液中曲马多的顶空固相微萃取气相色谱质谱联用(HS-SPME-GC/MS)分析方法。利用响应面法对顶空固相微萃取的条件进行优化,在优化的条件下,采用SKF为内标,在选择离子模式下,选取m/z 58(曲马多)和m/z 86(SKF)为定量离子,利用GC/MS对尿液中的曲马多进行定量分析。工作曲线线性范围超过0.05~1.0μg/mL(r2=0.9962)。检测限为0.011μg/mL(S/N=3),定量限为0.038μg/mL(S/N=10),用0.1μg/mL和0.75μg/mL曲马多标准液计算回收率分别在100.20%~109.65%和98.43%~103.82%之间,RSD为5.32%和9.13%(n=5)。建立的方法适用于尿液中曲马多。     

禽蛋中头孢噻肟残留的高效液相色谱-串联质谱法测定

建立了高效液相色谱-串联质谱(LC-MS/MS)测定禽蛋中头孢噻肟药物残留的方法。禽蛋样品中的头孢噻肟用纯水提取,乙腈沉淀蛋白,Oasis HLB(500 mg,6 mL)固相萃取柱净化,8 mL甲醇洗脱。采用Zorbax XDB-C18(2.1 mm×50 mm,3.5μm)色谱柱,以0.2%甲酸水-乙腈为流动相,0.3 mL/min梯度洗脱,经高效液相色谱分离后,采用电喷雾质谱正离子模式电离,多反应选择离子检测(MRM)模式测定。检测离子对为m/z456.1/396.1、m/z456.1/324.1,其中m/z456.1/396.1为定量离子对。在1.35~135μg/L范围内标准曲线的线性关系良好,相关系数为0.999 3;在1.0、50.0、100μg/kg3个添加水平的平均加标回收率为87%~99%,相对标准偏差为1.9%~3.9%;方法检出限为0.3μg/kg,定量下限为1.0μg/kg。该方法简便、灵敏、准确、可靠,适用于禽蛋中头孢噻肟药物残留的分析。     

两次液液萃取-气相色谱-质谱联用法测定动物肝脏中左旋咪唑残留

建立了液液萃取-气相色谱-质谱联用法测定动物组织中残留左旋咪唑的方法。在碱性溶液中将左旋咪唑盐酸盐转化为左旋咪唑,以乙酸乙酯进行提取;分别以HCl水溶液、氢氧化钾-二氯甲烷体系进行两次液液萃取净化,依次消除提取液中的脂溶性杂质和水溶性杂质,最后进入气相色谱-质谱系统,在选择离子监测模式下,以m/z 148、176、204为定性离子,m/z 204为定量离子进行结构确证和定量检测。结果表明: 左旋咪唑含量在0.25～3.0 mg/L范围内方法的线性关系良好(相关系数为0.999);定量限为5 μg/kg,低于当前国际最低限量标准;在鸡肝、鸭肝、兔肝和猪肝样品中的加标回收率在76%～106%范围内,相对标准偏差(RSD)小于9%。该法简便、稳定性好,无需对样品进行复杂的预处理即可实现对动物肝脏中左旋咪唑残留的快速准确测定。     

高效液相色谱-串联质谱法测定稻米和稻壳中井冈霉素A的残留

本文建立了稻米和稻壳中井冈霉素A的高效液相色谱-串联质谱(HPLC-MS/MS)分析方法。样品用甲醇-水(9+1)涡旋提取,过滤膜后进行HPLC-MS/MS分析。用多反应监测技术确定井冈霉素A的两对离子对m/z498.2/178.1、m/z498.2/336.1为定性离子对,m/z498.2/178.1为定量离子对。方法的线性范围为0.005～0.2mg/L,其中稻壳的线性相关系数为0.9993,稻米的线性相关系数为0.9988。稻米、稻壳的0.05、0.1、0.5 mg/kg三个浓度的添加回收率为71.6%～88.8%,相对标准偏差(RSD)为1.89%～8.16%。方法的定量限(LOQ)为5μg/kg。     

乳制品中那他霉素的超高效液相色谱-串联质谱法快速测定

建立了超高效液相色谱-电喷雾串联质谱(UPLC-MS/MS)快速检测乳制品中那他霉素的方法。样品用甲醇提取,以甲醇-水为流动相经反相色谱柱分离后,采用多反应监测(MRM)负离子模式检测,定性离子对为m/z663.6/421.1和m/z663.6/439.1,其中m/z663.6/421.1用于外标法定量。空白样品及其加标实验结果表明:特征离子相对强度比值稳定,无基质干扰,结合保留时间可实现准确的定性定量;方法定量下限为50.0μg/kg;乳制品加标量为50~500μg/kg时,平均回收率为80%~91%,相对标准偏差(n=6)为2.7%~5.2%。方法简单、灵敏、稳定,可满足乳制品中那他霉素的快速检测与确证需要。     

液相色谱-串联质谱检测蔬菜和茶叶中吡虫啉的残留量

介绍了利用液相色谱-串联质谱（LC-MS/MS）快速、准确地测定蔬菜、茶叶产品中吡虫啉残留量的方法。前处理方法为用乙腈提取,再用弗罗里硅土和活性炭混合柱净化。用多反应监测技术确定吡虫啉的两对离子(m/z 256.0/209.3,m/z 256.0/175.2)为定性离子对,m/z 209.3为定量离子。方法的定量限为0.01 mg/kg,线性范围为0.01～0.5 mg/L,加标回收率为76%～90%,相对标准偏差（RSD）为7.4%～11.0%。     

Mass spectrometric characterization of toremifene metabolites in human urine by liquid chromatography-tandem mass spectrometry with different scan modes

The metabolism and excretion of toremifene were investigated in one healthy male volunteer after a single oral administration of 120 mg toremifene citrate. Different liquid chromatographic/tandem mass spectrometric (LC/MS/MS) scanning techniques were carried out for the characterization of the metabolites in human urine for doping control purposes. The potential characteristic fragmentation pathways of toremifene and its major metabolites were presented. An approach for the metabolism study of toremifene and its analogs by liquid chromatography-tandem mass spectrometry was established. Five different LC/MS/MS scanning methods based on precursor ion scan (precursor ion scan of m/z 72.2, 58.2, 44.2, 45.2, 88.2 relative to five metabolic pathways) in positive ion mode were assessed to recognize the metabolites. Based on product ion scan and precursor ion scan techniques, the metabolites were proposed to be identified as 4-hydroxy-toremifene (m/z 422.4), 4'-hydroxy-toremifene (m/z 422.4), α-hydroxy-toremifene (m/z 422.4), 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2), 3-hydroxy-4-methoxy-toremifene (m/z 456.2), dihydroxy-dehydro-toremifene (m/z 440.2), 3,4-dihydroxy-toremifene (m/z 438.2), N-demethyl-4-hydroxy-toremifene (m/z 408.3), N-demethyl-3-hydroxy-4-methoxy-toremifene (m/z 438.3). In addition, a new metabolite with a protonated molecule at m/z 390.3 was detected in all urine samples. The compound was identified by LC/MS/MS as N-demethyl-4,4'-dihydroxy-tamoxifene. The results indicated that 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2) and N-demethyl-4,4'-dihydroxy-tamoxifene (m/z 390.3) were major metabolites in human urine.     

Metastable decompositions of gem-dialkoxyalkanes upon electron impact. III. Diethoxymethane (CH(2)(OCH(2)CH(3))(2))

Unimolecular metastable decomposition of diethoxymethane (CH(2)(OCH(2)CH(3))(2), 1) upon electron impact has been investigated by means of mass-analyzed ion kinetic energy (MIKE) spectrometry and theD-labeling technique in conjunction with thermochemistry. The m/z 103 ion ([M - H](+) : CH(OCH(2)CH(3)) = O(+)CH(2)CH(3)) decomposes into the m/z 47 ion (protonated formic acid, CH(OH) = O(+)H) by consecutive losses of two C(2)H(4) molecules via an m/z 75 ion. The resulting product ion at m/z 47 further decomposes into the m/z 29 and 19 ions by losses of H(2)O and CO, respectively, via an 1,3-hydroxyl hydrogen transfer, accompanied by small kinetic energy release (KER) values of 1.3 and 18.8 meV, respectively. When these two elimination reactions are suppressed by a large isotope effect, however, another 1,1-H(2)O elimination with a large KER value (518 meV) is revealed. The m/z 89 ion ([M - CH(3)](+) : CH(2)(OCH(2)CH(3))O(+) = CH(2)) decomposes into the m/z 59 ion (CH(3)CH(2)O(+) = CH(2)) by losing CH(2)O in the metastable time window. The source-generated m/z 59 ion ([M - OCH(2)CH(3)](+) : CH(2) = O(+)CH(2)CH(3)) decomposes into the m/z 41 (CH(2) = CH(+)CH(2)) and m/z 31 (CH(2) = O(+)H) ions by losses of H(2)O and C(2)H(4), respectively, with considerable hydrogen scrambling prior to decomposition. Copyright 2000 John Wiley & Sons, Ltd.     

An unexpected ion-molecule adduct in negative-ion collision-induced decomposition ion-trap mass spectra of halogenated benzoic acids

The ion observed at m/z 145 when product ion spectra of iodobenzoate anions are recorded using ion-trap mass spectrometers corresponds to the adduct ion [I(H(2)O)](-). The elements of water required for the formation of this adduct do not originate from the precursor ion but from traces of moisture present in the helium buffer gas. A collision-induced decomposition (CID) spectrum recorded from the [M-H](-) ion (m/z 251) derived from 3-iodo[2,4,5,6-(2)H(4)]benzoic acid also showed an ion at m/z 145. This observation confirmed that the m/z 145 is not a product ion resulting from a direct neutral loss from the carboxylate anion. (79)Bromobenzoate anions produce similar results showing an ion at m/z 97 for [(79)Br(H(2)O)](-). The ion-molecule reaction observed here is unique to ion-trap mass spectrometers since a corresponding ion was not observed under our experimental conditions in spectra recorded with in-space tandem mass spectrometers such as triple quadrupole or quadrupole time-of-flight instruments.     

Mass spectrometry for the characterization of unsulfated chondroitin oligosaccharides from 2-mers to 16-mers. Comparison with hyaluronic acid oligomers

This study reports for the first time the complete liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (MS/MS) analyses performed in negative ion mode of saturated unsulfated chondroitin oligosaccharides up to 16-mers and comparison with hyaluronic acid (HA) oligomers differing only in the nature of the hexosamine residue. MS/MS of the chondroitin disaccharide on the singly charged precursor at m/z 396.1 afforded a glycosidic cleavage C1 product ion at m/z 192.9. In the tetrasaccharide, C2 (m/z 396.0) and C3 (m/z 572.0) product anions were generated by glycosidic cleavage. A C5 [M-2H]2- product ion at m/z 475.1 was generated by the glycosidic cleavage of the hexasaccharide, and a C7 ion (m/z 664.6, charge state of -2) was produced from the octasaccharide. The same fragmentation pattern of deprotonated oligomers was observed for the largest oligosaccharides, from 10- to 16-mers. There has been no previous report of MS/MS spectra for unsulfated chondroitin oligomers of these sizes. Unsulfated saturated chondroitin oligosaccharides with x-mer units and larger than a tetrasaccharide dissociate to almost exclusively form CX-1-type ions. Saturated HA oligomers also afforded the same fragmentation pattern as deprotonated oligomers by ESI-MS and MS/MS analyses. Thus, under the experimental conditions used in the current study, we were unable to distinguish between unsulfated chondroitin and HA.     

Collision‐induced dissociation processes of protonated benzoic acid and related compounds: competitive generation of protonated carbon dioxide or protonated benzene

Upon activation in the gas phase, protonated benzoic acid (m/z 123) undergoes fragmentation by several mechanisms. In addition to the predictable water loss followed by a CO loss, the m/z 123 ion more intriguingly eliminates a molecule of benzene to generate protonated carbon dioxide (H ‐ O⁺ ═ C ≡ O , m/z 45), or a molecule of carbon dioxide to yield protonated benzene (m/z 79). Experimental evidence shows that the incipient proton ambulates during the fragmentation processes. For the CO₂ or benzene loss, protonated benzoic acid transfers the charge‐imparting proton initially to the ortho position and then to the ipso position to generate a transient species which dissociates to form an ion‐neutral complex between benzene and protonated CO₂. The formation of the m/z 45 ion is not a phenomenon unique to benzoic acid: spectra from protonated isophthalic acid, terephthalic acid, trans‐cinnamic acid and some aliphatic acids also displayed a peak for m/z 45. However, the m/z 45 peak is structurally diagnostic only for certain benzene polycarboxylic acids because the spectra of compounds with two carboxyl groups on adjacent ring carbons do not produce a peak at m/z 45. For the m/z 79 ion to be formed, an intramolecular reaction should take place in which protonated CO₂ within the ion‐neutral complex acts as the attacking electrophile to transfer a proton to benzene. Copyright © 2017 John Wiley & Sons, Ltd.     

手性化合物在质谱中光学稳定性的研究

反应质谱法自创立以来 ,已广泛应用于有机立体化学的研究领域 .其方法是在质谱离子源中引入反应试剂 ,使之与分析物发生立体选择性反应产生特征离子 ,通过这些特征离子可获得待分析样品的立体化学信息 [1] .我们 [2～ 5 ] 在前期工作中 ,通过在质谱中引入手性反应试剂造成手性环境 ,成功地研究了对映体的绝对构型 .由于质谱过程中常伴随着高温、质子酸催化等因素 ,因而随着反应质谱在对映体构型方面研究的深入进行 ,手性反应试剂及手性样品在质谱过程中是否会发生变旋这一问题日益引起我们的重视 .当对映异构体手性中心连接一个氢原子和一个…     

3-苯基-1-丁炔-3-醇质谱碎裂中[C8H7]^+的结构及分子内质子迁移反应

报道了3-苯基-1-丁炔-3-醇的常规电子轰击质谱(EIMS)。利用碰撞诱导解离(CID)技术研究了质谱碎裂过程中产生的[C8H7]^+的气相离子结构。同时, 氘代同位素交换、亚稳(MI)和CID实验进一步证实了m/z 103离子的形成并不是分子离子的质谱碎裂中顺次失去甲基自由基和中性CO分子的直接氢迁移的协同反应, 而是在失去CO分子前后发生了二次质子迁移反应的逐步过程。在此基础上提出了一种独特的双分子质子键合复合物中间体的碎裂机理。     

Fragmentation reactions of protonated peptides containing glutamine or glutamic acid

A variety of protonated dipeptides and tripeptides containing glutamic acid or glutamine were prepared by electrospray ionization or by fast atom bombardment ionization and their fragmentation pathways elucidated using metastable ion studies, energy-resolved mass spectrometry and triple-stage mass spectrometry (MS(3)) experiments. Additional mechanistic information was obtained by exchanging the labile hydrogens for deuterium. Protonated H-Gln-Gly-OH fragments by loss of NH(3) and loss of H(2)O in metastable ion fragmentation; under collision-induced dissociation (CID) conditions loss of H-Gly-OH + CO from the [MH - NH(3)](+) ion forms the base peak C(4)H(6)NO(+) (m/z 84). Protonated dipeptides with an alpha-linkage, H-Glu-Xxx-OH, are characterized by elimination of H(2)O and by elimination of H-Xxx-OH plus CO to form the glutamic acid immonium ion of m/z 102. By contrast, protonated dipeptides with a gamma-linkage, H-Glu(Xxx-OH)-OH, do not show elimination of H(2)O or formation of m/z 102 but rather show elimination of NH(3), particularly in metastable ion fragmentation, and elimination of H-Xxx-OH to form m/z 130. Both the alpha- and gamma-dipeptides show formation of [H-Xxx-OH]H(+), with this reaction channel increasing in importance as the proton affinity (PA) of H-Xxx-OH increases. The characteristic loss of H(2)O and formation of m/z 102 are observed for the protonated alpha-tripeptide H-Glu-Gly-Phe-OH whereas the protonated gamma-tripeptide H-Glu(Gly-Gly-OH)-OH shows loss of NH(3) and formation of m/z 130 as observed for dipeptides with the gamma-linkage. Both tripeptides show abundant formation of the y(2)' ion under CID conditions, presumably because a stable anhydride neutral structure can be formed. Under metastable ion conditions protonated dipeptides of structure H-Xxx-Glu-OH show abundant elimination of H(2)O whereas those of structure H-Xxx-Gln-OH show abundant elimination of NH(3). The importance of these reaction channels is much reduced under CID conditions, the major fragmentation mode being cleavage of the amide bond to form either the a(1) ion or the y(1)' ion. Particularly when Xxx = Gly, under CID conditions the initial loss of NH(3) from the glutamine containing dipeptide is followed by elimination of a second NH(3) while the initial loss of H(2)O from the glutamic acid dipeptide is followed by elimination of NH(3). Isotopic labelling shows that predominantly labile hydrogens are lost in both steps. Although both [H-Gly-Glu-Gly-OH]H(+) and [H-Gly-Gln-Gly-OH]H(+) fragment mainly to form b(2) and a(2) ions, the latter also shows elimination of NH(3) plus a glycine residue and formation of protonated glycinamide. Isotopic labelling shows extensive mixing of labile and carbon-bonded hydrogens in the formation of protonated glycinamide.     

Collision-induced dissociation of the negative ions of simvastatin hydroxy acid and related species

Simvastatin hydroxy acid (1) is a well-known, potent HMG-CoA reductase inhibitor for the treatment of hypercholesterolemia. Its lactone, simvastatin (commercial name Zocor) (a prodrug of 1), has been widely prescribed in the USA and throughout the world. In this work, collision-induced dissociation (CID) of the negative ion of 1 (m/z 435), a carboxylic anion, was analyzed in detail. The major fragmentation pathway of this ion is a novel de-esterification to form the negative product ions at m/z 319 and 115. The ion at m/z 319 undergoes further collision-induced rearrangements to form the negative ions at m/z 215, 159 and 85. Possible mechanisms of the de-esterification are discussed in terms of both charge-initiated and charge-remote fragmentations. The de-esterification of the negative ion of 1 and the rearrangements of the ion at m/z 319 are rationalized by charge transfer and negative-charge initiated fragmentation. This study deepens our understanding of collision-induced fragmentations of carboxylic anions with multi-functional groups. A comparison of the CID data for the negative ions of 1 and 5 (a major oxidation degradate of 1) indicates that the analysis of the CID data for 1 can serve as a basis for identification of oxidation degradation products or metabolites of 1. The analysis of the CID data for the negative ion of 1 also reveals the fundamental characteristics of the CID data for the negative ions of other statin hydroxy acids such as lovastatin (3) and pravastatin (4).     

Electrospray ionization mass spectrometry monitoring of indigo carmine degradation by advanced oxidative processes

The degradation of the dye indigo carmine in aqueous solution induced by two oxidative processes (H(2)O(2)/iodide and O(3)) was investigated. The reactions were monitored by electrospray ionization mass spectrometry in the negative ion mode, ESI(-)-MS, and the intermediates and oxidation products characterized by ESI(-)-MS/MS. Both oxidative systems showed to be highly efficient in removing the color of the dye aqueous solutions. In the ESI(-)-MS of the indigo carmine solution treated with H(2)O(2) and H(2)O(2)/iodide, the presence of the ions of m/z 210 (indigo carmine in its anionic form, 1), 216, 226, 235, and 244 was noticeable. The anion of m/z 235 was proposed to be the unprecedented hydroperoxide intermediate 2 formed in solution via an electrophilic attack by hydroxyl and hydroperoxyl radicals of the exocyclic C=C bond of 1. This intermediate was suggested to be rapidly converted into the anionic forms of 2,3-dioxo-1H-indole-5-sulfonic acid (3, m/z 226), 2-amino-alpha-oxo-5-sulfo-benzeneacetic acid (4, m/z 244), and 2-amino-5-sulfo-benzoic acid (5, m/z 216). In the ESI(-)-MS of the indigo carmine solution treated with O(3), two main anions were detected: m/z 216 (5) and 244 (4). Both products were proposed to be produced via an unstable ozonide intermediate. Other anions in this ESI(-) mass spectrum were attributed to be [4 - H + Na](-) of m/z 266, [4 - H](2-) of m/z 121.5, and [5 - H](2-) of m/z 107.5. ESI-MS/MS data were consistent with the proposed structures for the anionic products 2-5.