A Dual GC-MS and LC-MS/MS Analytical Strategy for Evaluating Free Chlorine Toxicity in Aqueous Samples

Area of Science:

• Analytical Chemistry
• Environmental Science
• Forensic Science

Background:

• Chlorine gas is a highly toxic industrial chemical with risks from accidental releases and intentional attacks.
• Reliable analytical methods are crucial for detecting chlorine in aqueous samples for investigations.
• Existing methods may lack the speed or selectivity required for rapid forensic and environmental analysis.

Purpose of the Study:

• To develop a rapid and selective mass spectrometry-based method for chlorine determination in aqueous samples.
• To achieve reliable identification and quantification of chlorine following a derivatization process.
• To create a method suitable for both forensic toxicology and environmental monitoring.

Main Methods:

• Aqueous chlorine samples were derivatized using methyl 2-(3,4,5-trimethoxyphenyl)acetate (MTMPA) to form methyl 2-(2-chloro-3,4,5-trimethoxyphenyl)acetate (Cl-MTMPA).
• The derivatization product (Cl-MTMPA) was analyzed using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS).
• Reaction conditions were optimized for high derivatization yield, and LC-MS/MS analysis was performed directly, while GC-MS required liquid-liquid extraction.

Main Results:

• Optimized derivatization yielded Cl-MTMPA with high efficiency.
• Both GC-MS and LC-MS/MS analyses identified a common major fragment ion at m/z 215.0.
• Liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS/MS) confirmed a characteristic product ion at m/z 215.0473.
• Calibration curves demonstrated excellent linearity (R² > 0.99) for toxicologically relevant chlorine concentrations (5-200 mg/L).

Conclusions:

• A rapid, selective derivatization method for chlorine analysis was successfully developed.
• The method enables reliable detection and quantification using both GC-MS and LC-MS/MS.
• Characteristic fragmentation patterns and excellent quantitative performance make the method suitable for forensic and environmental chlorine investigations.