Automated Data Analysis

An automated data analysis method for data collected using the Velox 360 ion source was developed using the Thermo Scientific Xcalibur mass spectrometer control and data analysis software package. The automated data analysis options in the Xcalibur software are designed for use with chromatographic peaks. The peak detection algorithms employed are not designed for use with ion sources, like paper spray ionization, which yield a minute or more of signal duration. However, by switching the spray voltage on after data collection begins and off before it ends, a “peak” of sorts is obtained and the software may be set to detect it. The key settings are in the “detection” tab of the processing method builder, shown in Figure 4.11. The baseline window should be set to as large a value as possible, which directs the program to search for the beginning and end of the peak over the maximum time

Table 4.6: Limits of detection for atrazine, simazine, and metabolites measured using the Velox 360 coupled to the TSQ Quantum Ultra mass spectrometer.

Figure 4.10: Calibration curves for atrazine, simazine, desethyl-atrazine, and desisopropyl- atrazine in water generated using the Velox 360 ion source coupled to a Thermo TSQ Quantum Ultra triple quadrupole mass spectrometer. The top panel shows all analytes

simultaneously (error bars omitted for clarity). The four lower panels show each analyte with error bars representing one standard deviation.

range. The peak noise and area noise factors should be set as small as possible. These settings adjust the peak signal threshold and peak edge detection threshold.

In the “advanced” settings accessible from the detection tab, shown in

Figure 4.12, the multiplet resolution should be set to the largest possible value and the minimum peak width set to a value reflecting the number of scans collected, which is instrument dependent. Setting the multiplet resolution high prevents the program from dividing the signal into multiple “peaks”. Because only one peak is present, and its w idth is known, these settings should be set to large values to prevent misidentification of multiple

Figure 4.12: The advanced peak detection parameters in Xcalibur. The indicated settings must be changed to ensure that the signal is considered a single peak for data analysis purposes.

Figure 4.11: The detection tab of the Thermo Xcalibur

processing method development program. The circled parameters must be adjusted to achieve automated peak integration.

peaks. A set of typical settings for automated analysis of data collected using the Velox 360 with the Thermo Scientific TSQ Quantum Ultra is shown in Table 4.7.

This method enables the automatic analysis of quantitative data collected using the Velox ion source in the same manner as LC-MS data would be analyzed. The algorithm does not identify the signal as a single peak with complete efficiency, and in some cases manual integration is required, especially when designing a new method. Regardless, the time required is dramatically reduced compared to manual data analysis by exporting extracted ion current traces into a spreadsheet, which is

the primary data analysis method used with the custom paper spray source. 4.6 Summary and Conclusions

The first commercially available paper spray ion source, the Velox 360 produced by Prosolia, Inc. has been investigated and characterized with several pesticides of regulatory interest. This ion source, while still open to improvement in some mechanical details, is certainly suited to use in qualitative and quantitative analyses of common pesticides such as the triazine family of herbicides. The Velox 360 is compatible with current and recent model Thermo Scientific mass spectrometers equipped with an atmospheric pressure inlet.

Quantitative data collected using the Velox 360 coupled to these instruments is amenable to automated data processing using the same tools used for peak identification and integration in liquid chromatography-mass spectrometry experiments, although some adaptation is

Table 4.7: Typical settings for automated signal integration for data collected using the Velox 360 with a triple quadrupole mass spectrometer.

required. The Velox 360 is also suited to the simultaneous analysis of multiple analytes, particularly when coupled to a triple quadrupole instrument operated in multiple reaction monitoring mode.

Several mechanical problems and minor design flaws were identified; all were reported to Prosolia, Inc. and resolved with assistance from Prosolia engineers. The majority of these problems are amenable to correction through minor design changes. Despite these difficulties, the Velox 360 is far easier to use than the custom ion source described in Chapter 2, and provides significantly better overall performance. In particular, the reproducibility of the Velox 360 is dramatically better than the custom ion source, an improvement that derives from the more precise mounting system, reproducible sample positioning, and reliable mass produced sample cartridges. The only significant feature lacking in the Velox 360 is

provision for the continuous application of solvent, which would be advantageous in performing instrument tuning and experiments investigating the behavior of samples over a longer period of time than is practical with the current design. However, this is not an essential feature, and the improvements in reproducibility, automation, ease of use, and expert support are sufficient to justify use of the Velox 360 rather than a custom ion source for routine analytical applications.

REFERENCES

(1) Espy, R. D.; Teunissen, S. F.; Manicke, N. E.; Ren, Y.; Ouyang, Z.; van Asten, A.; Cooks, R. G. Paper Spray and Extraction Spray Mass Spectrometry for the Direct and Simultaneous Quantification of Eight Drugs of Abuse in Whole Blood. Anal. Chem. 2014, 86 (15), 7712–7718 DOI: 10.1021/ac5016408.

(2) Prosolia Inc. Velox 360 | Prosolia http://www.prosolia.com/products/velox-360 (accessed Dec 8, 2015).

(3) Prosolia. Quantitation of Immunosuppressive Drugs Directly from Dried Blood Spots, App Note: 502; 2014,

www.prosolia.com/sites/default/files/APP%20NOTE%20502%20Velox%20360%20T acrolimus_Cyclosporine.pdf.

(4) Prosolia Inc. Velox 360 Paper Spray Installation and Operation Manual, Revision A.; Indianapolis, IN, 2015.

(5) Prosolia Inc. Velox Control Software Installation and Reference Manual, Revision A.; Indianapolis, IN, 2014.

(6) Hollinshead, D. Personal Communication. 12 March 2016. Prosolia, Inc.

(7) Huang, S.-B.; Mayer, T. J.; Yokley, R. A.; Perez, R. Direct Aqueous Injection Liquid Chromatography/Electrospray Ionization-Mass Spectrometry Analysis of Water for Atrazine, Simazine, and Their Chlorotriazine Metabolites. J. Agric. Food Chem. 2006, 54 (3), 713–719 DOI: 10.1021/jf052968q.

CHAPTER 5: PAPER SPRAY IONIZATION-MASS SPECTROMETRY FOR