Resolving interferences in negative mode ion mobility spectrometry using selective reactant ion chemistry

Area of Science:

• Analytical Chemistry
• Spectrometry

Background:

• 2,4,6-trinitrotoluene (TNT) degradation analysis presents challenges due to overlapping signals from interferents like 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (DCP).
• Standard Cl(-) reactant ion chemistry in ion mobility spectrometry (IMS) is not always sufficient for resolving these analyte and interferent peaks.

Purpose of the Study:

• To explore alternative methods for improving the resolution of analytes and interferents in IMS analysis of TNT degradation products.
• To overcome the limitations of Cl(-) reactant ion chemistry in distinguishing between TNT degradation products and common interferents.

Main Methods:

• Utilized ion mobility spectrometry (IMS) to analyze degradation products of 2,4,6-trinitrotoluene (TNT).
• Investigated the use of air as a reactant ion source for improved peak separation.
• Explored the efficacy of bromide (Br-) as an alternative reactant ion to chloride (Cl(-)).
• Assessed the impact of reduced IMS temperature on adduct stability and analyte resolution.

Main Results:

• Observed significant overlap between the IMS responses of TNT degradation products and interferents (2,4-D, DCP) using standard Cl(-) chemistry.
• Demonstrated that using air as the reactant ion source can sometimes resolve overlapping peaks.
• Showed that employing Br(-) as the reactant ion can also achieve resolution in specific cases.
• Found that lowering the IMS temperature enhances adduct stability, contributing to better separation of analytes and interferents.

Conclusions:

• Standard Cl(-) IMS methods are insufficient for resolving all analyte/interferent overlaps in TNT degradation studies.
• Alternative reactant ions (air, Br(-)) and temperature control offer viable strategies to enhance IMS resolution for complex mixtures.
• These optimized IMS conditions provide a more robust analytical approach for identifying TNT degradation products in the presence of interferents.