《lcms質(zhì)譜》ppt課件-文庫(kù)吧
2025-04-13 22:27 本頁(yè)面
【正文】 ct ? Ions can be positive or negative (1) Requirements of LC/MS Interfaces LC/MS接口的要求 ? Elimination of the mobile phase – Most difficult step – Can use splitters – Volatilized solvent vapor removed under vacuum ? Often where ionization occurs ? Vacuum required by mass analyzers (2) Challenges in Interfacing LC to MS ? Flow Rate Concerns ? Differential pumping can only handle 2 ?L/min of water ? For maximum sensitivity, want to use all of the eluent ? Use of Buffers and Additives ? Nonvolatile buffers a concern ? Some additives suppress ionization ? Wide Range of Analytes ? Many are nonvolatile, thermally labile (3) Transport Devices 傳送裝置 ? One of the first mercial interfaces ? Sample deposited onto a moving belt or wire ? Sample passes through multiple vacuum zones – Solvent elimination ? Sample is desorbed into source using heat – Electron impact ionization ? Belt/wire cycles back Moving Belt Interface From: Niessen (4) Particle Beam Interface （ PB， 粒子束接口） ? Column effluent is nebulized – Pneumatic or thermospray nebulization ? Desolvation chamber is under a moderate vacuum ? A momentum separator is used for analyte enrichment – High MW pounds favored ? Analytes into the EI or CI source as small particles – Evaporative collisions with the walls Particle Beam Interface Analyte Enrichment in PB Interfaces 分析物在 PB接口中富集 Analyte enrichment with a molecular beam approach Heavier molecules are in the core of the vapor jet and are sampled through the skimmer ? 在常壓下（借助氣動(dòng)霧化）產(chǎn)生氣溶膠； ? 氣溶膠擴(kuò)展進(jìn)加熱的去溶劑室蒸發(fā)掉殘余的溶劑， 待測(cè)分子在動(dòng)量分離器與溶劑分離。 ? 釋放出的氣態(tài)待測(cè)分子即可用所選的方法（主要為 EI或 CI）進(jìn)行離子化。 粒子束（ PB）接口 ? 能夠獲得像氣相色譜一樣且可用圖庫(kù)檢索的EI譜 是 PB接口的最有價(jià)值的優(yōu)點(diǎn) PBLCMS可產(chǎn)生像氣相色譜一樣的可用圖庫(kù)檢索的 EI譜 ? 其效率強(qiáng)烈地依賴于所生成的 氣溶膠的均勻性 。 因?yàn)闅馊苣z的大小分布越窄，動(dòng)量分離器工作得越好 粒子束（ PB）接口 ? PB接口雖然應(yīng)用廣泛，但在其它方面的應(yīng)用中，例如在環(huán)境分析中，仍存在一些不足： – 檢出限不適當(dāng)（ ng絕對(duì)范圍） – 靈敏變化范圍大（即便對(duì)結(jié)構(gòu)類似的化合物也這樣） – 缺乏較寬濃度范圍內(nèi)線性響應(yīng) – 兩種化合物的協(xié)同洗脫會(huì)對(duì)響應(yīng)產(chǎn)生不可預(yù)測(cè)的效應(yīng) ? 帶 PB接口的 LCMS已將 GCMS的應(yīng)用擴(kuò)展到了更多極性和較高分子質(zhì)量的化合物 ，但這似乎也已被其他的接口取代了 。 (5) Thermospray Interface （ TSP，熱噴霧接口） 溶劑是通過(guò)在加熱毛細(xì)管中形成噴霧的辦法而被蒸發(fā)的 ? Nebulization of the eluent from a heated transfer tube ? Uses a “reagent gas” – Mobile phase buffer – Added buffer solution – Similar spectra to GC/MS CI ? Reagent gas is ionized – Volatilization – EI with high energy electrons ? Charge transfer to the analyte(s) Thermospray Interface ? Effectively replaced transport systems ? Ionization in a medium pressure environment – Approx. 1000 Pa or atm ? Inlet flows of 1 to 2 mL/min – Can use standard LC column flows ? Positive and negative ions are possible ? Temperature optimization is critical – Maintain gas phase Thermospray LC/MS System From: McMaster and McMaster ?HPLC柱的流出物 電阻加熱毛細(xì)管蒸發(fā)器 ?在毛細(xì)管的出口端形成霧滴小于 1?m的氣溶膠，此氣溶膠則直接擴(kuò)展進(jìn)加熱的離子化室。 ?為了除去引入 MS系統(tǒng)的流量達(dá) 2mL/min的含水溶劑，需有一個(gè)容量非常大的 抽氣系統(tǒng) 。 ? 待測(cè)物的離子化可通過(guò) 以溶劑為媒介的化學(xué)離子化或通過(guò)熱噴霧離子化 過(guò)程來(lái)完成 – 化學(xué)離子化： 用噴霧電極（或細(xì)絲）的電子完成。它先由溶劑分子產(chǎn)生試劑氣，再由試劑氣將
教學(xué)課件相關(guān)推薦
鄂ICP備17016276號(hào)-1