《质谱条件的优化策略（简化板）》由会员分享，可在线阅读，更多相关《质谱条件的优化策略（简化板）（42页珍藏版）》请在金锄头文库上搜索。
1、液质分析条件的优化策略 （简化板）,液相色谱与液质联用仪使用的要点,质量校正的正确 对于相关分析要有合适的支持软件（Maxnet，TargeLyness） 合适的液相色谱平台 合适的质谱接口方式 液相色谱分析中合适的色谱柱的选用 质谱检测模式的选择 必要的后液流补充,质量校正的正确（Myoglobin校正）,质量校正的正确（Myoglobin校正）,质量校正的正确（CsI校正）的肽测定,质量校正的正确（CsI校正）的蛋白测定,质量校正的关键点,针对不同的分析采用不同的校正，一般蛋白质采用Myoglobin，对于小分子分析建议采用CsI校正。 对于采用Myoglobin校正的建议采用高次方的校正
2、曲线（3-4）；对CsI校正的建议采用低次方的校正曲线（1-2）,合适的液相色谱平台,能提供一个连续、稳定的液流环境 真空脱气设备 系统的死体积尽可能小，减少管路的长度 输液泵的设计能适用于微径柱的要求 二极管阵列检测器的池体积与质谱仪匹配 必要的液相色谱辅助配件 必要的液相色谱与质谱仪的软件操作平台,合适的液相色谱柱,柱内径：2.1mm 柱长度： 根据分析的目的选择50mm或150mm 柱填料选用新型的填料： Symmetry，Discovery，Vydac，Zorbax，Xterra，Intersil，Diamonsil等,LC/MS Flow Injection Analysis of
3、Peptides and Proteins by Reversed-Phase HPLC,1.0% HOAc,min,Abundance,Reverse-Phase LC/MS Solvents ACN, MeOH, H2O, Isopropanol Normal-Phase LC/MS Solvents (for APCI-MS) Hexane, Methylene Chloride, Acetone, Ethanol Compatible LC/MS Buffers and Modifiers: Formic acid, acetic acid, ammonium acetate, amm
4、onium formate, ammonium hydroxide, trifluoroacetic acid TFA concentration should be 0.1% v/v Keep volatile buffer concentrations 20 mM to minimize ESI ion suppression Avoid Non-volatile Buffers Alkali-metal phosphates, borates, etc.,Suitable Solvents for LC/MS,Volatile buffer minimize instrument dow
5、ntime Buffer concentration: High ion suppression decreases ESI sensitivity Low system adequately buffered? pH range permitted by stationary phase Methanol or acetonitrile Start with acetonitrile,01111,Change Retention to Improve Resolution Select Solvents/ Modifiers that are MS Compatible,Useful pH
6、Ranges for Volatile Buffers,Buffers normally used in LC/MS :,01094,Diethylamine,10.5,9.5 11.5,?,Ammonia,7,6 8,Buffer Concentrations/Additive amounts: 10 to 50 mM formic, acetic acids 0.01 - 1% v/v trifluoroacetic acid 0.1% v/v alkylamine type bases 0.1% v/v,Effect of Buffer on Analyte Response,Phosp
7、hate buffers suppress the MS response of caffeine at all pHs and also the MS response of Oxazepam at pH 8. Volatile buffers (formate, acetate, ammonia) generally provide good responses.,01121,Mobile phase: A - 10mM buffer pH 6.0; B methanol Gradient: 5% to 75% in 4 min,Mobile Phase pH effect on ESI,
8、Column : HyPURITY C18 5m, 50x2.1mm Aqueous mobile phases: 0.1% Formic acid pH 3, Ammonium formate 20 mM pH 5, Ammonium acetate 20 mM pH 8.2, Ammonium acetate 20 mM pH 9, Ammonium acetate 20 mM Aqueous/methanol (50:50) Flow rate: 0.2 ml/min Temperature: 25C Detection: +ESI, 450C, 4.5kV, 20V -ESI, 450
9、C, 3.5kV, 20V Scan: 120 480u,Analytes: Nortriptyline Propranolol Tetracycline Caffeine Paracetamol Tryptophan Salicylic acid Nicotinic acid,01113,Effect of Mobile Phase pH on +ESI Response,01115,Effect of Mobile Phase pH on -ESI Response,01116,Solution Chemistry Effects on Positive Ion ESI-MS of Leu
10、-Enkephalin,LC/MS Sensitivity vs. Mobile Phase Modifier GluC Digest of BS,5% Acetic,0.001% TFA,0.005% TFA,0.01% TFA,Zorbax 300SB-C3 (2.1 x 150 mm) HP1100 MSD,Reversed-phase HPLC/MS analysis of a GluC digest of BSA was used as a model to test the recovery and peakshape of peptides using varying conce
11、ntrations of TFA or 5% acetic acid as a mobile-phase additive in combination with the Zorbax 300SB-C3. Digestion of BSA was carried out 37C overnight, using GluC in a 1:20 ratio with BSA (by weight). The final mixture contained 1M urea and 25mM sodium phosphate. A significant increase in sensitivity
12、 of peptides was observed for most peptides analyzed using 5% acetic acid rather than TFA. Reducing TFA concentration to 0.001% caused only a minor improvement in sensitivity. Some peptides were much less affected by additive change than others.,0 for 5min, 0-40% B/55 min then 40-100% B/20 min F=0.2
13、mL / min, A= 5%Acetic Acid, B= ACN,MSD1 TIC, MS,Stable, Sterically Protected C3 Bonded Phase in LC and LC/MS Applications, R.D. Ricker (1), B.E. Boyes (1), J.P. Nawrocki (2), and L.K. Pannell (2)(1) Agilent Technologies, Inc. LC Applicatons Lab 538 First State Blvd, Newport, DE 19804-3552 USA. (2) S
14、tructural Mass Spectrometry Group NIDDK, NIH, Bethesda, MD, 20892 USA. Eastern Analytical Symposium, Nov., 1999,Proposed Mechanism for TFA Signal Suppression and the “TFA-Fix“,1:2 post-column addition of 75% propionic acid in IPA,Tryptic Digest Map by ES-LC/MS 1 nmol Chicken Lysozyme,Signal Suppress
15、ion due to Additives,Ion pairing with analyte, surface tension effect Solutions: Post-column addition of a sheath liquid of propionic acid (10%) in 2-propanol (TFA Fix) Use low concentrations of TFA with acetic acid (TFA Light) Replace TFA,ESI signal suppression by TFA,01122,Achievement of gaseous a
16、nalyte ionization at API interface is the key to MS detection,离子化方式,极性化合物多采用电喷雾（ESI），其中含氮的化合物一般在酸性条件下用ESI+（生物碱），含多羟基化合物采用中心条件下的ESI-（玉米赤酶醇）。 非极性化合物多采用大气压化学电离源（APcI）（激素），原则上不建议采用添加其它化学试剂,Steps for ESI Optimization,If analytes pKa is unknown, evaluate 3 pH regions in positive and negative ion modes. Ac
17、ids Negative Ion detection, adjust pH 2 units above pKa Increase pH with NH4OH, TEA, TMA Bases Postive Ion Detection, adjust pH 2 units below pKa 1 Decrease pH use formic acid , acetic acid, TFA Remove salts which may cause ion suppression Adjust source temperature and source voltages to maximize signal In negative ion mode, use lower spray voltage to minimize discharge,
