Results of the first and second British Mass Spectrometry Society interlaboratory studies on ambient mass spectrometry

Performance Comparison of Ambient Ionization Techniques Using a Single Quadrupole Mass Spectrometer for the Analysis of Amino Acids, Drugs, and Explosives

The utilization of ambient ionization (AI) techniques for mass spectrometry (MS) has significantly grown due to their ability to facilitate rapid and direct sample analysis with minimal sample preparation. This study investigates the performance of various AI techniques, including atmospheric solids analysis probe (ASAP), thermal desorption corona discharge (TDCD), direct analysis in real time (DART), and paper spray coupled to a Waters QDa mass spectrometer. The focus is on evaluating the linearity, repeatability, and limit of detection (LOD) of these techniques across a range of analytes, including amino acids, drugs, and explosives. The results show that each AI technique exhibits distinct advantages and limitations. ASAP and DART cover high concentration ranges, which may make them suitable for semiquantitative analysis. TDCD demonstrates exceptional linearity and repeatability for most analytes, while paper spray offers surprising LODs despite its complex setup (between 80 and 400 pg for most analytes). The comparison with electrospray ionization (ESI) as a standard method shows that ambient ionization techniques can achieve competitive LODs for various compounds such as PETN (80 pg ESI vs 100 pg ASAP), TNT (9 pg ESI vs 4 pg ASAP), and RDX (4 pg ESI vs 10 pg ASAP). This study underscores the importance of selecting the appropriate ambient ionization technique based on the specific analytical requirements. This comprehensive evaluation contributes valuable insights into the selection and optimization of AI techniques for diverse analytical applications.

Assessment of atmospheric solids analysis probe as a tool for the rapid determination of drug purity

The ability to determine the purity (% controlled compound) of drug-of-abuse samples is necessary for public health and law enforcement. Here, we describe the assessment of atmospheric solids analysis probe (ASAP) for the rapid determination of drug purity for a set of formulated pharmaceuticals, chosen due to their availability, uncontrolled status and consistency. Paracetamol and loratadine were used as models of high and low purity compounds being ~90% and ~10% active ingredient, respectively. Individual tablets were ground up and diluted in an internal standard solution. The resulting samples were analysed by ASAP coupled to a Waters QDa mass spectrometer followed by confirmatory testing by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The inclusion of a non-matched internal standard (quinine) improved linearity and repeatability of drug analysis by ASAP-MS. Levels of drug purity using formulated pharmaceutical tablets were found to be highly comparable with results produced by the 'gold standard' LC-MS/MS technique. Rapid determination of drug purity is therefore possible with ASAP-MS for highly concentrated samples with minimal sample preparation. It may be possible to use this deployable system to determine drug purity outside of a laboratory setting.

Ambient ionisation mass spectrometry for drug and toxin analysis: A review of the recent literature

Ambient ionisation mass spectrometry (AIMS) is a form of mass spectrometry whereby analyte ionisation occurs outside of a vacuum source under ambient conditions. This enables the direct analysis of samples in their native state, with little or no sample preparation and without chromatographic separation. The removal of these steps facilitates a much faster analytical process, enabling the direct analysis of samples within minutes if not seconds. Consequently, AIMS has gained rapid popularity across a diverse range of applications, in particular the analysis of drugs and toxins. Numerous fields rely upon mass spectrometry for the detection and identification of drugs, including clinical diagnostics, forensic chemistry, and food safety. However, all of these fields are hindered by the time-consuming and laboratory-confined nature of traditional techniques. As such, the potential for AIMS to resolve these challenges has resulted in a growing interest in ambient ionisation for drug and toxin analysis. Since the early 2000s, forensic science, diagnostic testing, anti-doping, pharmaceuticals, environmental analysis and food safety have all seen a marked increase in AIMS applications, foreshadowing a new future for drug testing. In this review, some of the most promising AIMS techniques for drug analysis will be discussed, alongside different applications of AIMS published over a 5-year period, to provide a summary of the recent research activity for ambient ionisation for drug and toxin analysis.

Selectivity of Explosives Analysis with Ambient Ionization Single Quadrupole Mass Spectrometry: Implications for Trace Detection

Ambient ionization (AI) is a rapidly growing field in mass spectrometry (MS). It allows for the direct analysis of samples without any sample preparation, making it a promising technique for the detection of explosives. Previous studies have shown that AI can be used to detect a variety of explosives, but the exact gas-phase reactions that occur during ionization are not fully understood. This is further complicated by differences in mass spectrometers and individual experimental set ups between researchers. This study investigated the gas-phase ion reactions of five different explosives using a variety of AI techniques coupled to a Waters QDa mass spectrometer to identify selective ions for explosive detection and identification based on the applied ambient ionization technique. The results showed that the choice of the ion source can have a significant impact on the number of ions observed. This can affect the sensitivity and selectivity of the data produced. The findings of this study provide new insights into the gas-phase ion reactions of explosives and could lead to the development of more sensitive and selective AI-based methods for their detection.

Direct analysis in real-time mass spectrometry: Observations of helium, nitrogen and argon as ionisation gas for the detection of small molecules using a single quadrupole instrument

RATIONALE

Direct analysis in real time is typically performed using helium as the ionisation gas for the detection of analytes by mass spectrometry (MS). Nitrogen and argon are found with abundance in the air and provide a cheaper and greener alternative to the use of helium as ionisation gas. This study explores the use of helium, nitrogen and argon as ionisation gas for the detection of organic compounds.

METHODS

Four illicit drugs, two amino acids and five explosives were chosen as target analytes to understand selectivity, sensitivity and linearity when helium, nitrogen or argon was used as the ionisation gas with the direct analysis in real time (DART) source. Analysis was carried out on a Waters Acquity QDa single quadrupole mass spectrometer.

RESULTS

Calibration curves over the range of 5-100 ng were produced for each analyte using the different ionisation gases to assess the instrument response. Nitrogen gave a higher response to concentration than helium or argon; however, the lowest limits of detection were observed when helium was used.

CONCLUSIONS

All the target analytes were detected using DART-MS with helium, nitrogen or argon as the ionisation gas. Whereas helium provided the highest sensitivity, nitrogen produced reasonable limits of detection and had good linearity across the concentration range explored, suggesting it provides a greener and cheaper alternative to helium.

Algorithms and Databases: Unlocking Non-Targeted Screening of Small Molecules with Ambient Ionization Mass Spectrometry

Almost all sectors of analytical chemistry are finding applications for ambient ionization mass spectrometry (AI–MS) because of its ease of use, speed of analysis, and sensitivity. Although emphasis has been placed on developing new hardware that can help analyze unique samples across various applications, there has not been much innovation in the functionality of software tools and mass spectral libraries to support applications like non-targeted searching. In this article, we discuss new algorithms and libraries that have enabled non-targeted analysis of small molecules using AI–MS, as well as some of the key considerations and outstanding questions in the field.

THE SPACE DIMENSION AT THE MICRO LEVEL: MASS SPECTROMETRY IMAGING OF DRUGS IN TISSUES

Mass spectrometry imaging (MSI) has seen remarkable development in recent years. The possibility of getting quantitative or semiquantitative data, while maintaining the spatial component in the tissues has opened up unique study possibilities. Now with a spatial window of few tens of microns, we can characterize the events occurring in tissue subcompartments in physiological and pathological conditions. For example, in oncology-especially in preclinical models-we can quantitatively measure drug distribution within tumors, correlating it with pharmacological treatments intended to modify it. We can also study the local effects of the drug in the tissue, and their effects in relation to histology. This review focuses on the main results in the field of drug MSI in clinical pharmacology, looking at the literature on the distribution of drugs in human tissues, and also the first preclinical evidence of drug intratissue effects. The main instrumental techniques are discussed, looking at the different instrumentation, sample preparation protocols, and raw data management employed to obtain the sensitivity required for these studies. Finally, we review the applications that describe in situ metabolic events and pathways induced by the drug, in animal models, showing that MSI makes it possible to study effects that go beyond the simple concentration of the drug, maintaining the space dimension. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Analysis of food samples made easy by microextraction technologies directly coupled to mass spectrometry

Because of the complexity and diversity of food matrices, their chemical analysis often entails several analytical challenges to attain accurate and reliable results, especially for multiresidue analysis and ultratrace quantification. Nonetheless, microextraction technology, such as solid-phase microextraction (SPME), has revolutionized the concept of sample preparation for complex matrices because of its nonexhaustive, yet quantitative extraction approach and its amenability to coupling to multiple analytical platforms. In recent years, microextraction devices directly interfaced with mass spectrometry (MS) have redefined the analytical workflow by providing faster screening and quantitative methods for complex matrices. This review will discuss the latest developments in the field of food analysis by means of microextraction approaches directly coupled to MS. One key feature that differentiates SPME-MS approaches from other ambient MS techniques is the use of matrix compatible extraction phases that prevent biofouling, which could drastically affect the ionization process and are still capable of selective extraction of the targeted analytes from the food matrix. Furthermore, the review examines the most significant applications of SPME-MS for various ionization techniques such as direct analysis in real time, dielectric barrier desorption ionization, and some unique SPME geometries, for example, transmission mode SPME and coated blade spray, that facilitate the interface to MS instrumentation.