Loughborough University, Translational Chemical Biology Research Group
Abstract
Compact mass spectrometry (CMS) is a versatile and transportable analytical instrument that has the potential to be used in clinical settings to quickly and non-invasively detect a wide range of relevant conditions from breath samples. The purpose of this study is to optimise data preprocessing protocols by three proposed methods of breath sampling, using the CMS. It also lays out a general framework for which data processing methods can be evaluated. Methods.This paper considers data from three previous studies, each using a different breath sampling method. These include a peppermint washout study using continuous breath sampling with a purified air source, an exercise study using continuous breath sampling with an ambient air source, and a single breath sampling study with an ambient air source. For each dataset, different breath selection (data preprocessing) methods were compared and benchmarked according to predictive performance on a validation set and quantitative reliability of m/z bin intensity measurements. Results. For both continuous methods, the best breath selection method improved the predictive model compared to no preselection, as measured by the 95% CI range for Youden’s index, from 0.68–0.86 to 0.86–0.97 for the exercise study and 0.69–0.82 to 1.00–1.00 for the peppermint study. The reliability of intensity measurements for both datasets (as measured by median relative standard deviation (RSD)), was improved slightly by the best selection method compared to no preselection, from 18% to 14% for the exercise study and 7%–5% for the peppermint study. For the single breath samples, all the models resulted in perfect prediction, with a 95% CI range for Youden’s index of 1.00–1.00. The reliability of the proposed method was 38%. Conclusion. The method of selecting exhaled breath from CMS data can affect the reliability of the measurement and the ability to distinguish between breath samples taken under different conditions. The application of appropriate data processing methods can improve the quality of the data and results obtained from CMS. The methods presented will enable untargeted analysis of breath VOCs using CMS to be performed.
Compact Mass Spectrometer (CMS).
Volatile Atmospheric Pressure Chemical Ionization (vAPCI) combined with Advion Interchim Scientific’s expression® compact mass spectrometer (CMS) is a fast and easy method to analyze the headspace of a sample with no additional sample prep.
The vAPCI ion source is a simple, powerful tool for gas phase sample analysis. The technique can quickly and confidently identify compounds in air, breath, headspace and other gas samples.
Direct sample analysis of liquids, solids and powders without chromatography is as easy as it sounds, and provides mass spectral information within seconds. The video demonstrates analysis of a reaction mixture.
Advion’s direct atmospheric solids analysis probe, otherwise known as ASAP®, permits chemists fast and reliable sample analysis of liquid and solid samples such as reaction mixtures, food samples, natural products and tablets.
Stephanie Rankin-Turner, Matthew A. Turner, Paul F. Kelly, Roberto S. P. King, James Reynolds
The ability to achieve rapid, in situ identification and age estimation of human bodily fluids can provide valuable information during the investigation of a crime. A novel direct analysis method now permits the rapid in situ identification and age estimation of human bodily fluids for forensic analysis at crime scenes. A thermal desorption surface sampling probe was developed and coupled with a compact mass spectrometer for the direct analysis of volatile organic compound (VOC) profiles of human bodily fluids within two months and in different environmental conditions, without the need for prior sample preparation. The method is not only capable of identifying bodily fluids and discriminating against common interferent species, but also differentiating between bodily fluid stains of different ages over a time period of two months. This demonstrates the potential for rapid in situ identification and age estimation of bodily fluids without the need for contaminative presumptive tests or time-consuming sample preparation.
The MS analysis was carried out using Advion Interchim Scientific Expression® CMS vAPCI.
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For Direct Mass Analysis of Liquid & Solid Samples with the expression® CMS
The direct atmospheric solids analysis probe, otherwise known as ASAP®, permits chemists fast and reliable sample analysis of liquid and solid samples such as reaction mixtures, food samples, natural products and tablets.
Chemists simply dip the closed end of a glass capillary into the sample of interest (even complex mixtures) or scrape the surface of a solid, and then place the capillary into the CMS for analysis.
Clean-up and analysis is a single step. Involatile buffers and salts remain on the capillary ensuring they do not suppress ionization or interfere with the measurement, while the compounds of interest are identified by the CMS.
In addition, users benefit from solvent-free APCI, which ionizes a wider range of compounds.
Provides simple, automated MS analysis in seconds, directly from TLC plates
The Plate Express® is a device that provides a simple, automated means of obtaining mass spectra directly from TLC plates, creating a technique known as TLC/MS. Combined with Advion Interchim Scientific’s expression® compact mass spectrometer (CMS) this becomes TLC/CMS. Using this technique, chemists can quickly and confidently identify products even in complex mixtures without additional sample preparation.
Identify spots in <1 minute
Avoid the risk of overloading the mass spectrometer – TLC spots contain the ideal amount of sample for mass spectrometry
Software controlled – spectra obtained within a few mouse clicks
Simplify the process of obtaining spectra – ideal for multi-user labs
Providing simple, high-performance, LC/CMS with the expression® CMS
Modular, stackable design, with many options provides custom solutions for both HPLC and UHPLC needs. From the simplest manual injection HPLC to a fully automated, streamlined UHPLC system and everything in-between, the Avant series can be configured to fit your analytical requirements and your budget.
The AVANT® (U)HPLC series is the latest in Advion’s innovative line of sample inlet devices for the expression® CMS which include:
Plate Express® for automated mass assays from TLC plates
The ASAP® direct analysis probe for solid, liquid and even air sensitive samples using iASAP
vAPCI for analysis of volatile organic compounds (VOCs) from head spaces, breath, and other gas samples.
Flow chemistry interfaces
All these techniques can be simply, simultaneously, interfaced with the CMS so that the chemist can move quickly and effortlessly between workflows.
For One-Touch Mass Analysis of Solids, Liquids,Surfaces and Fibers with the expression® CMS
The Touch Express™ Open Port Sampling Interface (OPSI), is designed for simple sampling of surfaces, solids, liquids and sample preparation tips and fibers. The novel ambient sampling technique was developed by Gary Van Berkel and Vilmos Kertesz, of Oak Ridge National Laboratory.
Paired with the electrospray ion source of the expression® Compact Mass Spectrometer, the solvent forms a meniscus at the open port before being drawn down the inner path into the electrospray ion source of the mass spectrometer under the Venturi effect of the nebulization gas. Any soluble sample touching the port is analyzed by the mass spectrometer in just seconds. Touch Express™ OPSI offers a fast assay bench-top solution for solid, liquids, and surfaces in a small-footprint, easy-to-use system.
