凝胶渗透色谱净化-气质联用法测定土壤中三嗪类除草剂

建立了以超声波提取、凝胶渗透色谱净化(GPC)、HP-5 MS石英毛细管柱分离、E1离子源质谱法测定土壤中13种三嗪类除草剂的多残留检测方法.三嗪类除草剂的添加水平为0.010～0.100 mg/kg时,平均回收率为72.1%～118.3%,相对标准偏差为2.6%～19.8%(n=4);方法的检出限为0.30～2.50μg/kg.     

超高效液相色谱-串联质谱法测定中药材中三唑类杀菌剂及三嗪类除草剂的残留量

建立了超高效液相色谱-串联质谱(UPLC-MS/MS)同时测定甘草、西洋参、三七、人参、丹参5种中药材中10种三唑类杀菌剂、18种三嗪类除草剂(包括有毒代谢物)残留量的分析方法。采用QuEChERS前处理方法,样品经1%(v/v)醋酸乙腈提取,乙二胺-N-丙基硅烷(PSA)净化处理,以Shim-pack XR-ODSII(75 mm×2.0 mm)为色谱柱,0.05%(v/v)甲酸溶液-乙腈为流动相梯度洗脱,在多反应监测(MRM)模式下测定。25种农药及其3种有毒代谢物的定量限(S/N≥10)为0.20～5.52 μg/kg;检出限(S/N≥3)为0.10～2.57 μg/kg;在各自的考察浓度范围内线性关系良好(r≥0.999);在0.20～55.2 μg/kg添加水平内,平均加标回收率为70.6%～125.7%,RSD为0.7%～14.2%。该方法样品前处理简单、快速、灵敏,可用于中药材中三唑类杀菌剂和三嗪类除草剂农药残留量的快速筛查。     

气相色谱化学电离二级质谱法测定土壤中16种三嗪类除草剂的残留

建立了气相色谱化学电离二级质谱法(GC-CI-MS/MS)同时测定土壤中16种三嗪类除草剂多残留量的方法,测定16种三嗪类除草剂仅需12min。样品采用乙腈与盐酸混合溶液,加入氯化钠超声波辅助提取,离心后,乙腈层经过国产石墨化炭黑(GCB)柱净化,流出液浓缩后环己烷定容,GC-MS/MS测定。研究比较了在不同进样溶剂下的化合物响应和不同填料固相萃取(SPE)柱的萃取净化效果,结果表明,环己烷作为进样溶剂效果最好,国产GCB和C18-SPE柱的回收率较好,同时国产GCB对色素的净化效果好,替代进口SPE柱,可以节约实验成本。16种三嗪类除草剂在0.05(0.1)～8.0mg/L范围内线性良好,相关系数在0.9952～0.9999之间;在0.005～0.02μg/g添加水平范围内,平均添加回收率在91.41%～114.12%之间;相对标准偏差在1.1%～16.8%之间。本方法中16种三嗪类除草剂在土壤中的检出限均低于0.005μg/g。     

超高效液相色谱-串联质谱法测定猪肉中硝基呋喃类代谢物

建立了超高效液相色谱-串联质谱(UPLC-MS/MS)测定猪肉组织中4种硝基呋喃类代谢物的分析方法.样品经盐酸水解,2-硝基苯甲醛衍生,乙酸乙酯提取净化,在正离子模式下以电喷雾电离串联质谱进行测定,内标法定量.在优化的实验条件下,4种代谢物在0.5~50μg/kg范围内线性良好,相关系数大于0.995,方法检出限为0.2μg/kg,定量限为0.5μg/kg.在0.5、1.0和10.0μg/kg的添加水平下,4种代谢物的平均回收率在74.6%~104.8%之间,相对标准偏差(RSD,n=6)在2.4%~15.6%之间.方法可应用于猪肉中4种硝基呋喃类药物代谢物残留的同时检测.     

分散固相萃取-超高效液相色谱-串联质谱法测定鸡肝中磺胺类、喹诺酮类和苯并咪唑类药物及其代谢物的残留量

建立了一种分散固相萃取-超高效液相色谱-串联质谱(QuEChERS-UPLC-MS/MS)测定鸡肝中12种磺胺类、19种喹诺酮类和8种苯并咪唑类药物及其代谢物残留的分析方法。样品用1%乙酸-乙腈溶液提取,NH2吸附剂净化,正己烷脱脂。用Kromasil Eternity C18色谱柱(100 mm×2.1 mm, 2.5 μm)分离,以0.1%甲酸水溶液和甲醇为流动相进行梯度洗脱,电喷雾正离子(ESI+)模式电离,多反应监测模式检测,内标法定量。39种药物在5～100 μg/kg的空白添加浓度范围内线性良好(r2＞0.98);在10～50 μg/kg的添加水平范围内,平均回收率为72%～121%,相对标准偏差(RSD)为1.5%～23.4%; 39种药物的检出限(LOD)为5 μg/kg,定量限(LOQ)为10 μg/kg。该方法简便、快速、灵敏、准确,适合鸡肝中磺胺类、喹诺酮类和苯并咪唑类药物残留的确证和定量测定。     

高效液相色谱法检测水产品中硝基呋喃类代谢物残留量

建立了水产品中硝基呋喃类代谢物残留量测定的样品处理方法和高效液相色谱分析方法.样品经酸解、2.氯苯甲醛衍生后用乙酸乙酯萃取、SPE柱净化,经高效液相-紫外检测器测定.本方法4种硝基呋喃类代谢物的定量限均为1.0μg/kg,在5.0～500μg/L质量浓度范围内,4种硝基呋喃类代谢物的工作曲线均呈良好线性,在2个添加浓度水平的平均回收率为76%～102%,相对标准偏差均小于10%(n=6).该方法适用于定性定量水产品中硝基呋喃类代谢物的残留分析.     

水产品中酰胺类除草剂及其代谢物的气相色谱-质谱法测定

建立了同时测定水产品中5种酰胺类除草剂（乙草胺、甲草胺、异丙甲草胺、丁草胺、丙草胺）及其代谢物2-甲基-6-乙基苯胺（MEA）、2, 6-二乙基苯胺（DEA）的气相色谱－质谱联用（GC－MS）分析方法。样品经二氯甲烷－乙酸乙酯（3∶2,体积比）混合溶剂提取,正己烷洗脱后进行GC－MS检测。在优化检测条件下,MEA、DEA、异丙甲草胺在1.0～25 μg/L质量浓度范围内,其余4种目标物在2.0～50 μg/L质量浓度范围内与其响应值线性关系良好,相关系数（r2）均不低于0.998 8。在低、中、高3个加标水平下,四角蛤蜊的回收率为69.7%～111%,相对标准偏差（RSD）为0.40%～7.6%;许氏平鮋和三疣梭子蟹的回收率分别为65.3%～118%、61.4%～113%,RSD分别为1.7%～9.3%、0.90%～7.1%。MEA、DEA、异丙甲草胺的检出限和定量下限分别为0.5、1.5 μg/kg,其余4种农药的检出限、定量下限分别为1.0、3.0 μg/kg。用该方法检测山东省沿海海域的四角蛤蜊、大菱鲆、中国对虾和半滑舌鳎样品,在一份四角蛤蜊样品中检出代谢物MEA,检出率为2.5%。该方法灵敏度、精密度均满足农药残留检测要求,适用于水产品中5种酰胺类除草剂及其代谢物的残留检测。     

粮食中磺酰脲类除草剂的UPLC/MS/MS测定方法

建立了多类粮食作物中15种磺酰脲类除草剂的超高效液相色谱-串联质谱联用仪(UPLC/MS/MS)多离子监测(MRM)的多残留检测方法。样品经乙腈提取,乙腈饱和的正己烷液-液分配,石墨化碳氨基小柱净化,采用UPLC-MS/MS(ESI+)测定。方法中各种磺酰脲类除草剂在5～200μg/L浓度范围内线性良好,相关系数在0.9995～0.9999。在5～100μg/kg范围内,平均加标回收率在71.6%～115.3%之间,相对标准偏差不大于15%。各种药物的定量限(S/N≥10)均可达到5μg/kg。该方法可同时满足大豆、大米、玉米等多种粮食中磺酰脲类除草剂的检测需求。     

改进的QuEChERS结合LC-MS/MS同时测定蜂蜜中60种兽药残留

建立了同时测定蜂蜜中60种兽药残留的LC-MS/MS检测方法。蜂蜜样品采用Mcllvaine缓冲溶液(pH 4)稀释,5%乙酸乙腈提取,提取液经盐析,NH2吸附剂分散固相萃取净化,LC-MS/MS动态多反应监控模式测定。在3个添加水平下(n=6),60种兽药平均回收率在70%～120%范围内的占比分别为96.7%,98.3%和98.3%,RSD为0.6%～20%。在0.1～1000μg/kg范围内,81.7%的目标物的线性相关系数(r2)>0.995,检出限和定量限范围分别为0.01～17.99μg/kg和0.02～59.97μg/kg。对16个市售蜂蜜样品进行测定,其中5个样品中检出磺胺类、喹诺酮类、硝基咪唑类等兽药残留。该方法具有一次处理样品,可同时测定60种兽药残留的特点,适合于蜂蜜中多类兽药的高通量筛查检测。     

水中苯氧羧酸类除草剂的液相色谱-串联质谱测定方法研究

建立了固相萃取(SPE)/超高效液相色谱-三重四极杆串联质谱(UPLC-MS/MS)同时测定水中8种苯氧羧酸类除草剂残留的方法。过滤后的样品经HLB固相萃取柱富集净化后,采用BEH C18柱,以2 mmol/L乙酸铵-乙腈作为流动相进行梯度洗脱,采用串联质谱进行检测。8种苯氧羧酸类除草剂在0.8～100μg/L质量浓度范围内线性关系良好(r=0.995 8～0.999 6),回收率为74%～90%,相对标准偏差为1.0%～12.0%,方法检出限(3S)为1.0～1.8 ng/L。该方法快速、灵敏,适用于水体中8种苯氧羧酸类除草剂残留的测定。     

红景天苷及其酯化产物的ESI MS和MS/MS裂解途径

糖苷广泛存在于自然界中,常以糖苷酯形式存在,这有效地提高了它们的酯溶性,增加它们在肠内和胞内的吸收[1-3]。红景天苷是一种具有抗疲劳、抗辐射、抗缺氧、提高记忆、延缓衰老等药理活性的天然糖苷[4-8],在此先导化合物的基础上合成了各种红景天苷酯。本文对这类红景天苷酯的E     

MS/MS: Cloned mass spectrometers

Coupling mass spectrometers in tandem (MS/MS) can greatly increase the specificity of MS analysis without significantly decreasing its unusual sensitivity and speed, particularly for trace levels of preselected compounds in complex organic mixtures. MS/MS also gives more detailed structural information for larger organic molecules in submicrogram quantities.     

Dual parallel electrospray ionization and atmospheric pressure chemical ionization mass spectrometry (MS), MS/MS and MS/MS/MS for the analysis of triacylglycerols and triacylglycerol oxidation products

Two mass spectrometers, in parallel, were employed simultaneously for analysis of triacylglycerols in canola oil, for analysis of triolein oxidation products, and for analysis of triacylglycerol positional isomers separated using reversed-phase high-performance liquid chromatography. A triple quadrupole mass spectrometer was interfaced via an atmospheric pressure chemical ionization (APCI) interface to two reversed-phase liquid chromatographic columns in series. An ion trap mass spectrometer was coupled to the same two columns using an electrospray ionization (ESI) interface, with ammonium formate added as electrolyte. Electrospray ionization mass spectrometry (ESI-MS) under these conditions produced abundant ammonium adduct ions from triacylglycerols, which were then fragmented to produce MS/MS spectra and then fragmented further to produce MS/MS/MS spectra. ESI-MS/MS of the ammoniated adduct ions gave product ion mass spectra which were similar to mass spectra obtained by APCI-MS. ESI-MS/MS produced diacylglycerol fragment ions, and additional fragmentation (MS/MS/MS) produced [RCO](+) (acylium) ions, [RCOO+58](+) ions, and other related ions which allowed assignment of individual acyl chain identities. APCI-MS of triacylglycerol oxidation products produced spectra like those reported previously using APCI-MS. APCI-MS/MS produced ions related to individual fatty acid chains. ESI-MS of triacylglycerol oxidation products produced abundant ammonium adduct ions, even for those molecules which previously produced little or no intact molecular ions under APCI-MS conditions. Fragmentation (MS/MS) of the [M+NH(4)](+) ions produced results similar to those obtained by APCI-MS. Further fragmentation (MS/MS/MS) of the diacylglycerol fragments of oxidation products provided information on the oxidized individual fatty acyl chains. ESI-MS and APCI-MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols.     

LC/MS and LC/MS/MS determination of protein tryptic digests

Tryptic digests were analyzed by means of online microbore liquid chromatography combined with mass spectrometry (LC/MS) for some common proteins. Following conventional enzymatic digestion with trypsin, the freeze-dried residues were dissolved in high-performance liquid chromatography (HPLC) eluent and subjected to gradient reversed-phase microbore HPLC separation with mass spectrometric detection. The latter was done in the full-scan single or tandem (MS/MS) mass spectrometry mode. The formation of gas-phase ions from dissolved analytes was accomplished at atmospheric pressure by pneumatically assisted electrospray (ion spray) ionization. This produced field-assisted ion evaporation of dissolved ions, which could then be mass-analyzed for molecular mass or structure. In the full-scan LC/MS mode, the masses for the peptide fragments in the tryptic digests can be determined as either their singly or multiply charged ions. When the molecular weights of the peptides lie outside the mass range of the mass spectrometer, the multiply charged feature of these experimental conditions still provides reliable molecular weight determinations. In addition, collision-activated dissociation (CAD) on selected peptide precursor ions provides online LC/MS/MS sequence information for the tryptic fragments. Results are shown for the tryptic digests of horse heart cytochrome c, bovine β-lactoglobulin A, and bovine β-lactoglobulin B.     

Analytical performance of the various acquisition modes in Orbitrap MS and MS/MS

Quadrupole Orbitrap instruments (Q Orbitrap) permit high‐resolution mass spectrometry‐based full scan acquisitions and have a number of acquisition modes where the quadrupole isolates a particular mass range prior to a possible fragmentation and high‐resolution mass spectrometry‐based acquisition. Selecting the proper acquisition mode(s) is essential if trace analytes are to be quantified in complex matrix extracts. Depending on the particular requirements, such as sensitivity, selectivity of detection, linear dynamic range, and speed of analysis, different acquisition modes may have to be chosen. This is particularly important in the field of multi‐residue analysis (eg, pesticides or veterinary drugs in food samples) where a large number of analytes within a complex matrix have to be detected and reliably quantified. Meeting the specific detection and quantification performance criteria for every targeted compound may be challenging. It is the aim of this paper to describe the strengths and the limitations of the currently available Q Orbitrap acquisition modes. In addition, the incorporation of targeted acquisitions between full scan experiments is discussed. This approach is intended to integrate compounds that require an additional degree of sensitivity or selectivity into multi‐residue methods.     

Selective detection and identification of phosphopeptides by dansyl MS/MS/MS fragmentation

Protein phosphorylation regulates many cellular processes and pathways, such as cell cycle progression, signal transduction cascades and gene expression. Selective detection of phosphopeptides from proteolytic digests is a challenging and highly relevant task in many proteomics applications. Often phosphopeptides are present in small amounts and need selective isolation or enrichment before identification. Here we report a novel approach to label selectively phospho-Ser/-Thr residues by exploiting the features of a novel linear ion trap mass spectrometer. Using dansyl labelling and MS3 fragmentation, we developed a method useful for the large-scale proteomic profiling of phosphorylation sites. The new residues in the sequence were stable and easily identifiable under general conditions for tandem mass spectrometric sequencing.     

Analysis of MS/MS fragmentation of taxoids

The fragmentation pathways of seven types of taxoids were investigated by using a LC-MS/MS method, namely: (1) neutral taxoids with a C-4(20) double bond; (2) taxoids with a C-4(20) double bond and oxygenation at C-14; (3) 5-cinnamoyl taxoids with a C-4(20) double bond; (4) a basic taxoid with a C-4(20) double bond; (5) a taxoid with a C-4(20) epoxide; (6) taxoids with an oxetane ring; and (7) taxoids with an oxetane ring and a phenylisoserine C-13 side chain. Depending on the class of core structure and the substitution pattern, each taxoid gave either the molecular adduct ion [M+NH4]+ or [M+H]+. In the MS/MS, the molecular adduct ion gave characteristic product ions corresponding to the loss of water, acetic acid, benzoic acid, and cinnamic acid or the phenylisoserine group. These could reflect the difference of the substitutions and structural modifications and should be utilized for the structure elucidation oftaxoids by LC-MS.     

An impulse-driven liquid-droplet deposition interface for combining LC with MALDI MS and MS/MS

A simple and robust impulse-driven droplet deposition system was developed for off-line liquid chromatography matrix-assisted laser desorption ionization mass spectrometry (LC-MALDI MS). The system uses a solenoid operated with a pulsed voltage power supply to generate impulses that dislodge the hanging droplets from the LC outlet directly to a MALDI plate via a momentum transfer process. There is no contact between the LC outlet and the collection surface. The system is compatible with solvents of varying polarity and viscosity, and accommodates the use of hydrophobic and hydrophilic MALDI matrices. MALDI spots are produced on-line with the separation, and do not require further processing before MS analysis. It is shown that high quality MALDI spectra from 5 fmol of pyro-Glu-fibrinopeptide deposition after LC separation could be obtained using the device, indicating that there was no sample loss in the interface. To demonstrate the analytical performance of the system as a proteome analysis tool, a range of BSA digest concentrations covering about 3 orders of magnitude, from 5 fmol to 1 pmol, were analyzed by LC-MALDI quadrupole time-of-flight MS, yielding 6 and 57% amino acid sequence coverage, respectively. In addition, a complex protein mixture of an E. coli cell extract was tryptically digested and analyzed by LC-MALDI MS, resulting in the detection of a total of 409 unique peptides from 100 fractions of 15-s intervals.