Electrospray ionization-ion mobility spectrometry: a rapid analytical method for aqueous nitrate and nitrite analysis

Area of Science:

• Analytical Chemistry
• Environmental Science

Background:

• Ion mobility spectrometry (IMS) is a powerful technique for analyzing ions.
• Detecting anions in aqueous solutions using IMS can be challenging.
• Electrospray ionization (ESI) is commonly used for mass spectrometry but less explored for IMS of anions.

Purpose of the Study:

• To report the first application of electrospray ionization (ESI) for anion separation and detection in aqueous solutions using ion mobility spectrometry (IMS).
• To assess the feasibility of ESI-IMS as a rapid analytical method for monitoring nitrate and nitrite in water systems.
• To evaluate parameters for on-site measurement applications.

Main Methods:

• Anions (arsenate, phosphate, sulfate, nitrate, nitrite, chloride, formate, acetate) were analyzed using ESI-IMS.
• Reduced mobility constants (K(0)) were determined for standard anion solutions.
• Real-world water samples were analyzed for nitrate and nitrite.
• Direct sample introduction and air as a drift gas were evaluated for on-site measurements.

Main Results:

• Distinct peak patterns and K(0) values were observed for different anions.
• Satisfactory correlation was found between measured and reported nitrate-nitrogen concentrations in drinking water.
• Linear dynamic range of 3 orders of magnitude was achieved.
• Instrument detection limits were 10 ppb for nitrate and 40 ppb for nitrite.
• High r(2) values (0.98 for nitrate, 0.99 for nitrite) were obtained from calibration curves.

Conclusions:

• ESI-IMS is a viable technique for the separation and detection of anions in aqueous solutions.
• The method demonstrates potential for rapid, on-site monitoring of nitrate and nitrite in water systems.
• Further optimization for direct sample introduction and alternative drift gases enhances its practical applicability.