液質(zhì)聯(lián)用中質(zhì)譜條件的優(yōu)化策略-預(yù)覽頁
【正文】 orizer Temp (176。C): 250350C? Tube Lens Offset (V): 3060V?Higher flow rate means more solvent for plasma production?Position of corona discharge needle is critical for sensitivity“ Works better at higher flow rates”02386APCITips? Ensure that the APCI probe is hot enough so that the spray shield is not dripping wet? Vaporizer Temp: 400450C is a good start (4001000uL/min)? Reduce temperature of heated capillary if needed? Check sheath gas carefully? Begin with aux gas at 0? Memory effect due to pounds burning onto probe parts if injected in large concentrations? Bake out source periodically02385APCI Summary? Analyte type:–low to mid polarity–high proton affinity –high gas phase acidity– 1200 da? Typical flow rates : ml/min? Tolerates buffers better than ESI? Produces singly charged ions only? Soft ionization technique ? Typical applications: Drugs, Pesticides, Steroids, Azo dyes01332Obtaining a Reference Spectrum? Unlike the EI process, spectra generated by API LC/MS vary depending on– mobile phase– source conditions– ionization mode– insource CID conditionsSpectral Variations mobile phasem/z75 100 125 150 175 200 225 NaOAc + % HOAc m/z75 100 125 150 175 200 2250100002023030000400005000004000080000120230% HOAc Spectral Variations CID conditionsm/z100 150 200 250 300010000202303000040000Fragmentor = 120 Volts m/z100 150 200 250 30004000080000120230Fragmentor = 75 Volts Spectral Variations ion polaritym/z100 150 200 250 300APIES Negative m/z100 150 200 250 300020406080100020406080100APIES Positive 質(zhì)譜參數(shù)的控制? 電離電壓（ capillary voltage）? 導(dǎo)入電壓（ cone voltage）? Probe 位置? 霧化氣流與干燥氣流? 聚焦棱鏡電壓（ Len）? 根據(jù)需求條件一級(jí)、三級(jí)的分辨率，原則上 scan、daughter條件下，選用單位質(zhì)量分辨條件，在 mrm條件下，選用 23單位質(zhì)量分辨率。多級(jí)質(zhì)譜提高靈敏度的方法? 通過合適的電離方式進(jìn)行，尤其是對(duì)于能否將 [M+Na]+改變?yōu)?[M+H]+? 通過合適的方法提高電離效率，如后補(bǔ)液來調(diào)整流動(dòng)相的 PH值和有機(jī)溶劑比例關(guān)系等。? 色譜行為服從于質(zhì)譜行為要求，尤其是在電離要求上。Guidelines for Choosing Ionization MethodYesIs pound polar?Is pound thermally labile?Is pound basic, acidic or neutral?APCI or APPINoYesESINeutral BasicAcidicESI (positive)ESI (negative) APCINo殘留分析的一般工作策略? 確定目標(biāo)化合物，研究目標(biāo)化合物結(jié)構(gòu)特性，預(yù)期可能的電離模式。殘留分析的一般工作策略? 對(duì)目標(biāo)化合物采用適當(dāng)?shù)姆绞竭M(jìn)行電量?jī)?yōu)化，如直接進(jìn)樣、載流恒比進(jìn)樣、載流定量管進(jìn)樣等，得到最優(yōu)化的質(zhì)譜參數(shù)。
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