液相色谱 - 串联质谱（LC-MS-MS）

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) - Technical Overview

LC-MS/MS is a powerful analytical technique that combines the exceptional separation capability of liquid chromatography with the high sensitivity and selective mass analysis capability of triple quadrupole mass spectrometry.

Separation Process:
The sample solution containing target analytes is pumped through the stationary phase (LC column) by a high-pressure mobile phase flow (typically 300-1000 bar). Differential migration rates through the LC column are determined by the chemical interactions between:

• Sample components

• Stationary phase (various bonded phases available)

• Mobile phase (adjustable composition)
  Multiple combinations of stationary and mobile phases enable customized separations for complex sample matrices.

Detection Process:
The column effluent is introduced into the mass spectrometer, which consists of:

1. Ion Source:

   • Nebulization: Converts liquid to fine droplets (2-5 μm diameter)

   • Desolvation: Removes solvent at 150-500°C

   • Ionization: Generates charged particles (typically ±1500-5000V)

2. Mass Analyzer (Triple Quadrupole):

   • Q1: Selects precursor ions (parent ions) with specific m/z ratios

   • Collision Cell (Q2): Fragments selected ions using inert gas (Ar/N₂) collision

   • Q3: Filters characteristic product ions (daughter ions)

3. Detection System:

   • Electron multiplier detects ions with 10⁶-10⁷ amplification

   • Data system records specific precursor→product ion transitions (MRM)

Key Advantages:

• High Specificity: MS/MS transitions provide structural confirmation

• Ultra-Sensitivity: Detection limits to sub-pg levels

• Wide Dynamic Range: >5 orders of magnitude

• High Throughput: Simultaneous monitoring of 100+ transitions

Technical Specifications:

• Mass Range: 50-2000 m/z

• Resolution: 0.7 FWHM (unit mass)

• Scan Speed: Up to 10,000 amu/sec

• Sensitivity: <1 pg for most compounds

• Precision: <5% RSD (peak area)