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Natural Product Discovery with LC-MS/MS Diagnostic Fragmentation Filtering: Application for Microcystin Analysis
07:18

Natural Product Discovery with LC-MS/MS Diagnostic Fragmentation Filtering: Application for Microcystin Analysis

Published on: May 31, 2019

Electrolyte-induced ionization suppression and microcystin toxins: ammonium formate suppresses sodium replacement

William M Draper1, Dadong Xu, S Kusum Perera

  • 1California Department of Public Health, Sanitation & Radiation Laboratory, 850 Marina Bay Parkway, Richmond, California 94804, USA. william.draper@cdph.ca.gov

Analytical Chemistry
|April 21, 2009
PubMed

Insights

Electrolytes like sodium replacement ions interfere with microcystin (MC) analysis using LC-MS-MS. Adding ammonium formate (AF) buffer improves accuracy and specificity for MC detection by suppressing these interferences.

Area of Science:

  • Environmental Chemistry
  • Analytical Chemistry
  • Mass Spectrometry

Background:

  • Microcystins (MCs) are potent cyanotoxins requiring accurate quantification.
  • Electrospray ionization (ESI) mass spectrometry (MS) can be affected by electrolytes, leading to sodium replacement ions (SRI) in MC spectra.
  • These SRI phenomena complicate congener-specific LC-MS-MS detection and reduce quantitative reliability.

Purpose of the Study:

  • To investigate the impact of electrolytes on microcystin (MC) electrospray ionization (ESI) and quantitative LC-MS-MS.
  • To evaluate the effectiveness of ammonium formate (AF) as a buffer additive for improving MC analysis.
  • To elucidate mechanisms of electrolyte-induced ionization suppression in MC determination.

Main Methods:

  • Analysis of MCs using electrospray ionization (ESI) and liquid chromatography-tandem mass spectrometry (LC-MS-MS).
  • Electrolyte effects were studied using methanol-water gradients with acetic acid.
  • Pulse addition experiments were conducted to assess the impact of ammonium formate (AF) on SRI and adduct formation.

Main Results:

  • Sodium replacement ions (SRI) were observed in MC ESI spectra, impairing congener-specific detection and quantitative accuracy.
  • Ammonium formate (AF) addition significantly suppressed SRI in both +1 and +2 charge states.
  • AF enhanced MH(+) and MNH(4)(+) adducts, leading to increased specificity and improved transitions for MC quantification.

Conclusions:

  • Electrolytes, particularly sodium, interfere with MC analysis by forming SRI, degrading LC-MS-MS performance.
  • Post-column or mobile phase addition of ammonium formate (AF) effectively suppresses SRI and enhances desired adducts.
  • Utilizing a buffer electrolyte like AF is crucial for achieving improved specificity and analytical ruggedness in quantitative LC-MS-MS of microcystins.

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