Current status and need for standards in ion mobility spectrometry

Point-of-care detection of sevoflurane anesthetics in exhaled breath using a miniature TOFMS for diagnosis of postoperative agitation symptoms in children

A miniature TOFMS with MEPEI has been developed for POC diagnosis of postoperative agitation symptoms, and can analyze sevoflurane by direct sampling. The risk is high when the sevoflurane in the exhaled breath is higher than 500 ppmv.

Isoflurane as an Accurate Negative Mode Calibrant for Ion Mobility Spectrometry

The search for suitable ion mobility spectrometry (IMS) calibrant compounds is ongoing and necessitates the use of highly accurate reduced ion mobility (K₀) values across a range of instrumental conditions. Such values will be used in calibrating devices to shift the ion mobility scales and alarm windows for chemicals of interest to their proper locations based on the instrumental conditions present during calibration and sampling. Many positive ion mode calibrants have been investigated, whereas investigations for a negative ion detection mode calibrant have been more limited. Isoflurane (IsoF) is a strong candidate as a negative ion mode calibrant. This report documents the accurately measured K₀ values for IsoF product ions as a function of multiple instrumental parameters. K₀ values were measured in two instrumentation modes as a function of drift gas temperature, water concentration, and dopant concentration. This report culminates with our evaluation of the suitability of IsoF as a negative ion mode calibrant for IMS applications.

Accurate Evaluation of Potential Calibration Standards for Ion Mobility Spectrometry

Ion mobility spectrometry (IMS)-based instruments have historically been accurate to, at best, ±2% of the reduced ion mobility (K₀) value of the chemical of interest. Fielded IMS-based detectors that are in use for hazardous and illicit substance detection are subject to false-positive alarms because of this inaccuracy and the resulting wide alarm windows, which are required to maintain a high rate of true-positive alarms. To reduce false-positive alarm rates and improve the accuracy of any IMS-based instrument, accurate K₀ values of an ion mobility reference standard need to be used for ion mobility scale calibration. However, a suitable calibrant has yet to be accurately analyzed and agreed upon by the IMS community. In this study, we have chosen five potential IMS calibrants on the basis of their rating against seven criteria for suitable standards and analyzed them as a function of drift gas temperature and humidity using an accurate ion mobility instrument. Recommendations are made herein for each potential calibrant's suitability as a standard for the wider IMS community.

Rapid detection of explosive vapors by thermal desorption atmospheric pressure photoionization differential mobility analysis tandem mass spectrometry

RATIONALE

The increased frequency in the number of international terror threats has led to a corresponding increase in demand for fast, sensitive and reliable screening methods suitable for the detection of airborne explosive vapors. We demonstrate herein a workflow suitable for the determination of nitrogen-based explosives at the picogram level in just minutes.

METHODS

A method is described that combines Thermal Desorption (TD) sample introduction with Differential Mobility Analysis (DMA) Tandem Mass Spectrometry (MS/MS), enabling a sensitive and accurate workflow suitable for the rapid detection of trace nitroaromatic, nitroester and nitramine explosive vapors. The methods are bridged using a novel low-flow, field-free Atmospheric Pressure Photoionization (APPI) source, intended specifically for the analysis of gas-phase analytes and airborne particles.

RESULTS

Limits of detection within or below the picogram range were determined for the analysis of a range of explosives standards including 2,6-DNT, TNT, TATB, Tetryl, RDX, EGDN, PETN, HMX, and NG. Practical application of the TD-APPI-DMA-MS/MS workflow was demonstrated for the detection of real trace explosive vapors produced from the volatilization of solid explosive samples stored within a sealed cardboard box. A single complete analysis was performed in less than 2 min.

CONCLUSIONS

The highly sensitive and accurate detection of a variety of common nitrogen-based explosive vapors has been demonstrated, at levels suitable for practical, high-throughput security screening applications.