JEOL Resources

Material Evaluation using msFineAnalysis - MSTips 330

Fri, 03 Sep 2021 10:02:44 GMT

MSTips No. 330

Introduction

As polymer materials have become more complex and diverse, the details of their chemical composition have become more critical for the end users. This knowledge allows manufacturers and users to understand the effects of incorporating these polymer materials into their products. Additionally, it is critical to also have tools that can quickly compare two-samples to each other like conventional materials versus alternative materials, new products versus old products, and good products versus defective products.

Gas chromatography-mass spectrometry (GC-MS) is an analytical technique that is widely used for both qualitative and quantitative analysis of volatile compounds in materials. For these types of measurements, GC-MS analyses typically only involve library database searches to identify each analyte. However, it is not uncommon to measure unknown analytes that are not registered in the databases so for these compounds, it is not possible to identify them with the database search method. To address this problem, we developed the msFineAnalysis software in 2018 that uses an "integrated analysis" approach in which the EI fragmentation information is combined with the soft ionization (SI) accurate mass information for the molecular ion to automatically determine the most logical chemical formula for each analyte.

More recently, msFineAnalysis Ver. 3 was introduced in which a differential analysis function was added to the software that uses t-tests to compare two samples to each other. In this work, we compared two polypropylene/polyethylene (PP/PE) copolymerized polymers to show the differential analysis capabilities of msFineAnalysis Ver. 3.

Download the article below to Read More

AccuTOF GC Materials and Chemistry Applications Notebook

Thu, 11 Mar 2021 09:59:16 GMT

Various applications on the topics of Materials and Chemistry for the AccuTOF GC Series

Please click below to download.

Analysis of Additives in Plastic by Thermal Desorption (TD)

Tue, 18 Aug 2020 20:19:08 GMT

MSTips No. 138

Among the various methods used for characterizing plastics, pyrolysis (Py) GC/MS and thermal desorption (TD) GC/MS are widely used for both qualitative and quantitative analyses. These are simple techniques that provide detailed information about the samples. In this application note, we report the analysis of additives in plastic by using a thermal desorption system and a JEOL JMS-T100GCV "AccuTOF GCv" GC-TOFMS. Identification of the analytes was accomplished by library search and accurate mass measurement. Additionally, isotope cluster pattern matching was performed using the "Mass Spec Tools™" software to help identify an unknown compound that was present in the sample.

Integrated Analysis of a Vinyl Acetate Resin using Pyrolysis GC-HRMS - MSTips 275

Mon, 22 Jun 2020 12:07:06 GMT

MSTips No. 275

Electron ionization (EI) is a hard ionization method that is commonly used with gas chromatography mass spectrometry (GC-MS). The mass spectral fragmentation patterns produced by EI are used for library database searches to identify compounds. Conversely, soft ionization methods like field ionization (FI) tend to produce clear molecular ions with minimal fragmentation. When high-resolution MS is used with these ionization techniques, the accurate masses for the fragment ions produced by EI and the molecular ions produced by soft ionization provide an additional dimension of information for the analytes. Combining the exact mass information with the results of conventional library search can enhance the accuracy of identification compared to the use of library search alone. In this work, we introduce the msFineAnalysis software and use it to automatically combine data acquired by GC/EI and GC/soft ionization for the qualitative analysis of compounds produced by the pyrolysis of a vinyl acetate resin.

Integrated Analysis of Coffee Aroma by using a Headspace GC-HRMS - MSTips 280

Mon, 13 Apr 2020 12:12:21 GMT

Experiment

A commercial coffee was prepared as follows:

One gram of coffee beans was loaded into a 22 mL HS vial, 15 mL of 100˚C water was added, and the vial was sealed.
After the sample was cooled to room temperature, 10 mL of the supernatant was loaded into a HS vial, and 2 µL of an internal reference (p-Bromofluorobenzene) was added to the sample.
Finally, 2 mL of the above solution was transferred and sealed in a vial that was then used as a sample.

Table 1 shows the measurement conditions used for the headspace/GC-TOFMS system.

Table 1. Measurement conditions

[Headspace Conditions]
System	MS-62070STRAP (JEOL)
Mode	Trap mode
Extract	3 times
Heating condition	60°C, 15 min
[GC-TOFMS Conditions]
System	JMS-T200GC (JEOL)
Ionization mode	EI+: 70 eV, 300 μA FI+: -10 kV, 8mA (Carbotec 5 mm)
GC column	ZB-WAX, 30 m x 0.18 mm, 0.18 μm
Oven temp.	40°C (3 min) → 30°C/min → 250°C (10 min)
Inlet temperature	250°C
Inlet mode	Split 30:1

Results and discussions

Figure 1 shows the operational flow chart for the integrated analysis steps used for the JEOL msFineAnalysis software (chart on the right). First, the data is acquired by using both EI and soft ionization (SI), and all peaks and associated mass spectra are detected in the chromatograms. Afterwards, the mass spectra produced by these ionization methods are linked using their retention times, and these linked mass spectra are recorded as single components. Next, the EI mass spectrum is used for the library database search (1), and the SI mass spectrum is used to identify the analyte molecular ion (2). Afterwards, the molecular ion is used for exact mass analysis to determine possible elemental compositions, and these candidate formulas are then filtered by using the EI library search results (3). Next, the molecular ion is subjected to isotopic pattern analysis to help further limit the candidate formulas (4). Each candidate formula is then used as a search constraint for the exact mass analysis of the EI fragment ions (5). If the molecular ion formula candidate is incorrect, the EI fragment ions will not result in many (if any) compositional formulas, thus indicating that the molecular ion formula is not a good candidate for that particular analyte. These results are then output as an integrated qualitative report (6).

Figure 1. Qualitative Analysis Flow

Figure 2. TIC chromatograms of coffee aroma acquired by a HS/GC/TOFMS

Figure 3. Integrated qualitative analysis results on msFineAnalysis

The msFineAnalysis Auto Analysis function detected 67 components in the GC/EI and GC/FI measurements (Figure 2) that were automatically linked using their retention time. The Auto Analysis function then automatically used the steps in Figure 1 to analyze the linked data, and the results were output as a color-coded table as shown in Figure 3. Each color indicates a level of confidence for the identity of the compound:

Green: A molecular formula candidate was uniquely identified.
Orange: Multiple molecular formula candidates were identified.
White: No significant molecular formula candidates were identified.

The components classified as orange or white can be further reviewed manually to potentially identify a unique candidate formula. In this example, the software was able to automatically determine a unique molecular formula for 63 of the 67 components in the coffee headspace sample.

Conclusions

The msFineAnalysis software produces highly accurate qualitative analysis results by automatically combining the EI library search results and soft ionization (SI) molecular formula determinations. Additionally, this software makes it possible to determine molecular formulas for unknown components not registered in library (match factor score: low), which can not be identified by database search alone (Figure 1, left side). The effectiveness of the msFineAnalysis integrated analysis method effectiveness for GC/MS qualitative analysis was demonstrated by automatically determining molecular formulas from exact masses, regardless of the level of match factor score, to limit the candidate formulas.

Integrated Analysis of an Acrylic Resin using msFineAnalysis v2 - MSTips 300

Mon, 13 Apr 2020 11:34:01 GMT

Software Enhancements

Changes in msFineAnalysis Ver.2:
Version 2 continues to use the integrated analysis work flow (see MS Tips 275) and TICC peak detection developed in Ver.1. Major changes from Version 1 include: 1) Improved graphical user interface (GUI), 2) chromatographic deconvolution, and 3) Group Analysis.

1) Improved GUI:
Version 2 supports two languages: English and Japanese. The GUI was extensively modified to display tabulated integrated analysis results and chromatograms on a single view. Color schemes are now represented by Color Universal Design (CUD) to enhance visibility for people with different kinds of color vision.

2) Chromatographic deconvolution:
Chromatographic deconvolution reconstructs mass spectra by using information (m/z, area) of peaks detected in extracted ion chromatograms (EIC) using the exact masses of the ions observed. This provides high-quality mass spectra for coeluting components that may appear as a single peak in the total ion current chromatogram (TICC).

3) Group Analysis:
Group analysis identifies related compounds in a complex mixture by creating selected ion chromatograms for compounds that have common fragment ions or common neutral losses. This makes it easier to examine component groups and isomers having a similar partial structure.

Experiment

A commercial acrylic resin was used as a model sample. A JEOL JMS-T200GC GC-HRTOFMS was used for analysis, and a Frontier Lab pyrolysis inlet was used for sample pretreatment. Additionally, the system was equipped with an EI/FI combination ion source for this work. The resulting data were analyzed by using msFineAnalysis version 2 (JEOL). Table 1 shows the pyrolysis and GC-HRTOFMS analysis conditions.

Table 1. Measurement conditions

[Pyrolysis Conditions]
Pyrolyzer	PY-3030D (Frontier Lab)
Pyrolysis Temperature	600°C
[GC-TOFMS Conditions]
System	JMS-T200GC (JEOL)
Ion Source	EI/FI combination ion source
Ionization mode	EI+: 70 eV, 300 μA FI+: -10 kV, 40mA/30msec
Mass Range	m/z 35-800
GC column	ZB-5MSi, 30 m x 0.25 mm, 0.25 μm
Oven temp.	40°C (2 min) → 10°C/min → 320°C (15 min)
Inlet mode	Split 100:1
[Data processing Conditions]
Software	msFineAnalysis (JEOL)
Library database	NIST17
Tolerance	±5mDa
Electron	Odd
Element set	C: 0-50, H: 0-100, O: 0-10

Figure 1. Py-GC/EI and Py-GC/FI total ion current chromatograms of an acrylic resin polymer at 600°C

Figure 2. EI and FI mass spectra of related compounds with (a) monomers, (b) dimers, and (c) trimers.

Results and discussions

Figure 1 shows the TICC data for both GC/EI and GC/FI measurements. Methyl acrylate (MA) and methyl methacrylate (MMA) were detected at high intensity. Dimers and trimers were observed at retention times of 10 min and 18 min, respectively. Figure 2 shows typical mass spectra for the monomers, dimers, and trimers. Molecular ions were detected at high relative intensity in FI mass spectra but were weak or absent in the EI mass spectra. Many of the acrylic resin pyrolysates do not have entries in the library database, making it difficult to identify their components by library search alone. Additionally, soft ionization was essential because EI did not produce molecular ions for many compounds as shown in Figure 2b and 2c.

When the msFineAnalysis Auto Analysis was used on for the GC/EI and GC/FI data, 161 components were automatically detected. Ultimately, molecular formulas of 154 components out of the 161 were uniquely identified. Additionally, the formulas of EI fragment ions, which were obtained from accurate mass data, resulted in structural information for the sample molecules. Next, monomers, dimers, and trimers were examined using Group Analysis—the results are shown in Table 2. Out of the 161 components, 46 were directly related to the monomers, dimers, and trimers. In Group Analysis, molecular ions of a desired repeat unit formula are specified and analyzed, speeding up the analysis process. The results for the Group Analysis can be exported, making it easier to calculate the relative intensities using the sum of the chromatogram peak areas shown in Table 2. Other components detected include pyrolysis products in which alkyl chains are bonded with monomers, dimers, and trimers.

Conclusions

The integrated analysis method produces highly accurate qualitative analysis results from the database entries with high match scores by combining the library search results and molecular formula estimation. Additionally, this analysis makes it possible to determine molecular formulas for unknown components not registered in a library database that cannot be identified by database searching alone. The integrated analysis method made it possible to to determine molecular formulas from exact mass results, regardless of the level of match factor score.

Table 2. Integrated qualitative analysis results for monomers, dimers, trimers and their isomers.

This narrowed down the candidate compositions, demonstrating the effectiveness of this software for GC/MS qualitative analysis.

Analyzing a Specific Component using Group Analysis of msFineAnalysis Ver. 2 - MSTips 303

Mon, 13 Apr 2020 10:47:59 GMT

Software Enhancements

Chromatographic Deconvolution:
The msFineAnalysis Version 2 software supports chromatographic deconvolution to reconstruct mass spectra by using the information (m/z, area) from extracted ion chromatograms (EIC) created using exact mass information. Chromatographic deconvolution is effective in separating coeluting components which are detected as a single peak in the total ion current chromatogram (TICC).

Group Analysis:
Group analysis can be used after chromatographic deconvolution to identify compounds that have common substructures. Group analysis is accomplished by creating mass chromatograms from the exact mass data to identity compounds that have the same molecular weight, or that have common fragments or neutral losses. Figure 1 shows the graphical user interface (GUI) for Group analysis.

Experiment

A commercial vinyl acetate resin was used as a model sample. A JEOL JMS-T200GC GC-HRTOFMS was used for analysis, and a Frontier Lab pyrolysis inlet was used for sample pretreatment. Additionally, the system was equipped with an EI/FI combination ion source for this work. The resulting data were analyzed by using msFineAnalysis version 2 (JEOL). Table 1 shows the pyrolysis and GC-HRTOFMS analysis conditions.

Table 1. Measurement conditions

[Pyrolysis Conditions]
Pyrolyzer	PY-3030D (Frontier Lab)
Pyrolysis Temperature	600°C
[GC-TOFMS Conditions]
System	JMS-T200GC (JEOL)
Ion Source	EI/FI combination ion source
Ionization mode	EI+: 70 eV, 300 μA FI+: -10 kV, 6mA/10msec (Carbotec)
GC column	DB-5MSUI, 30 m x 0.25 mm, 0.25 μm
Oven temp.	50°C (1 min) → 30°C/min → 330°C (1.7 min)
Inlet mode	Split 100:1

Figure 1. Group Analysis Window

Figure 2. Group analysis results of C₆H₅ ion

Results and discussions

Figure 1 shows the C₆H₅ fragment ions that were detected in the pyrolysis GC-MS results for the vinyl acetate resin. This fragment ion is characteristic for aromatic compounds. The table on the right shows that there are 26 compounds containing C₆H₅. The view on the left allows the operator to quickly identify where the components containing this ion were detected. The view on the left top shows the GC/EI data with the TICC marked by a solid black line. The bottom left view shows the soft ionization data with the TICC marked by a solid green line. The blue peaks in both views represent the components containing C₆H₅ extracted from the chromatographic deconvolution result. The operator can select an ion such as C₆H₅ from the table and click the OK button at the bottom right of the GUI to immediately create a C₆H₅ tab, thus allowing for extraction of the components containing that specific fragment (Figure 2).

Figure 2 shows the extracted results for components containing C₆H₅. The Group Analysis function displays an “All” tab for the entire analysis results and up to 5 tabs for groups created for ions or neutral losses specified from the exact mass list in Figure 1. For example, the operator can select a fragment ion containing nitrogen, phosphate, or sulfur to find a group of compounds containing the specified elements. The ID and integrated analysis results are then shared between tabs. The results under the C₆H₅ tab represent a group of aromatic compounds.

Conclusions

The msFineAnalysis program is designed to run integrated analysis with or without library search. It is a qualitative program based on a new concept that is effective for non-targeted analysis. The basic functions of the program are capable of identifying numerous components for non-targeted analysis. Group Analysis adds the capability to extract specific compounds or families of related compounds in the same manner as target analysis, speeding up the process of their detailed analysis.

Using Volcano Plots to Compare Vinyl Acetate Resin Samples Measured by Pyrolysis GC-MS

Thu, 05 Mar 2020 08:35:43 GMT

Experiment

As model samples, 6 commercial vinyl acetate resins (adhesives) were used. A gas chromatography time-of-flight mass spectrometer (GC-TOFMS) was used for the measurements. Since emulsion samples including adhesives are difficult to analyze without preliminary treatment, the samples were subjected to pyrolysis. Also, a column shorter than a typical GC column was used along with a Fast GC temperature sequence to speed up the measurement process.

The data acquired was examined using SpectralWorks Analyzer Pro, and 2 samples were compared by the Volcano Plot. Table 1 shows the pyrolysis fast GC/TOFMS measurement conditions.

The Qualitative Analysis of an Antioxidant Additive Using the Full Capabilities of the EI/FI/FD Combination Ion Source

Thu, 05 Mar 2020 08:31:48 GMT

JEOL has developed a unique EI/FI/FD combination ion source for the “AccuTOF GCv 4G”, a high- resolution GC-time-of-flight (TOF) MS system. This unique ion source provides the capabilities of GC/EI, GC/FI and FD measurements without having to break vacuum in order to switch between each ionization mode. Additionally, this combination is particularly powerful in that it provides library searchable fragmentation information by using EI and high mass accuracy molecular ion information by using FI and FD. In this work, we measured an antioxidant additive by using each ionization mode available on the AccuTOF GCv 4G combination ion source (EI/FI/FD).

The Power of Exact Mass Measurement: An Example of Unknown Compound Identification

Thu, 05 Mar 2020 08:29:47 GMT

Experimental

The system used for this work was the JEOL AccuTOF-GC TOF MS. Liquid crystal from a pocket calculator display was dissolved in hexane. Afterwards, the sample was injected onto a DB-5 GC column (0.18mm x 10m, 0.18μm film thickness). The oven temperature was held at 40°C for 1 min and then increased to 300°C at 50°C/min rate. The TOF MS was tuned to achieve a resolution of 5,000 (FWHM) at m/z 293 (Perfluorokerosene). 2,4,6-tris(trifluoromethyl)-1,3,5-triazine was used as an internal standard for the exact mass measurements in both EI and CI modes. The CI reagent gas was isobutane. The NIST mass spectral database (2002) was used for the EI spectrum searches.