Limits...
Determination of Chlorophenoxy Acid Methyl Esters and Other Chlorinated Herbicides by GC High-resolution QTOFMS and Soft lonization.

Lopez-Avila V, Roach P, Urdahl R - Anal Chem Insights (2015)

Bottom Line: Gas chromatography with quadrupole time-of-flight mass spectrometry (GC-QTOFMS) and soft ionization generated by a rare-gas plasma is described here for the determination of various chlorophenoxy acid methyl esters and a few chlorinated herbicides.This plasma-based, wavelength-selectable ionization source, which can use Xe, Kr, Ar, Ne, or He as the plasma gas, enables ionization of GC-amenable compounds with ionization energies below 8.4, 10, 11.6, 16.5, or 22.4 eV, respectively.Data generated with the Ar plasma and real matrices such as a peppermint extract, a plum extract, and an orange peel extract, spiked with 16 test compounds, indicate that the test compounds can be detected at 1-10 pg/μL of extract, and compounds such as menthone, limonene, eucalyptol, pinene, caryophylene, and other C15H24 isomers, which are present in the peppermint and the orange peel extracts at ppm to percent levels, do not appear to interfere with the determination of the chlorophenoxy acid methyl esters or the chlorinated herbicides, although there were matrix effects when the test compounds were spiked at 1-10 pg/μL of extract.

View Article: PubMed Central - PubMed

Affiliation: Agilent Technologies, Santa Clara, CA, USA.

ABSTRACT
Gas chromatography with quadrupole time-of-flight mass spectrometry (GC-QTOFMS) and soft ionization generated by a rare-gas plasma is described here for the determination of various chlorophenoxy acid methyl esters and a few chlorinated herbicides. This plasma-based, wavelength-selectable ionization source, which can use Xe, Kr, Ar, Ne, or He as the plasma gas, enables ionization of GC-amenable compounds with ionization energies below 8.4, 10, 11.6, 16.5, or 22.4 eV, respectively. The advantages of soft ionization include enhanced molecular ions, reduced fragmentation, and reduced background noise as compared to electron ionization. In the study presented here for two plasma gases, we demonstrate that Kr plasma, which is softer than Ar plasma, yields molecular ions with a relative intensity >60% for 11 of the 16 test compounds. When using this "tunable" plasma to ionize the analytes, there is the possibility for selective ionization and less fragmentation, which may lead to increased sensitivity and may help structure elucidation, especially when using high-resolution mass spectrometry that generates accurate masses within a few parts per million (ppm) mass errors. Data generated with the Ar plasma and real matrices such as a peppermint extract, a plum extract, and an orange peel extract, spiked with 16 test compounds, indicate that the test compounds can be detected at 1-10 pg/μL of extract, and compounds such as menthone, limonene, eucalyptol, pinene, caryophylene, and other C15H24 isomers, which are present in the peppermint and the orange peel extracts at ppm to percent levels, do not appear to interfere with the determination of the chlorophenoxy acid methyl esters or the chlorinated herbicides, although there were matrix effects when the test compounds were spiked at 1-10 pg/μL of extract.

No MeSH data available.


Related in: MedlinePlus

TICs of the unspiked orange peel extract, orange peel extract spiked with the 16 chlorinated acids, and the reference standard of the 16 chlorinated acids. Concentrations are in the range 2.5–10 ng/μL. The TICs do not show limonene because the peak is saturated. Also not shown are dalapon at 2.64 minutes and acifluorfen at 12.7 minutes. The chromatograms were obtained with a DB-5 MS capillary column (same GC conditions), so there is a slight increase in the retention time of all compounds as compared to the HP-5MS capillary column. Dinoseb before 2,4-DB on the DB-5MS capillary column.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4325682&req=5

f4-aci-10-2015-001: TICs of the unspiked orange peel extract, orange peel extract spiked with the 16 chlorinated acids, and the reference standard of the 16 chlorinated acids. Concentrations are in the range 2.5–10 ng/μL. The TICs do not show limonene because the peak is saturated. Also not shown are dalapon at 2.64 minutes and acifluorfen at 12.7 minutes. The chromatograms were obtained with a DB-5 MS capillary column (same GC conditions), so there is a slight increase in the retention time of all compounds as compared to the HP-5MS capillary column. Dinoseb before 2,4-DB on the DB-5MS capillary column.

Mentions: The orange peel extract contained percent levels of limonene, and, despite all this, there was no shift in the retention times of the 16 test compounds in the spiked matrix relative to the reference standard, except for the switch in the elution order of 2,4-DB methyl ester and bentazon methyl, as shown in Figure 4, which occurred for both the matrix and the reference standard because a DB-5MS column was used for these measurements.


Determination of Chlorophenoxy Acid Methyl Esters and Other Chlorinated Herbicides by GC High-resolution QTOFMS and Soft lonization.

Lopez-Avila V, Roach P, Urdahl R - Anal Chem Insights (2015)

TICs of the unspiked orange peel extract, orange peel extract spiked with the 16 chlorinated acids, and the reference standard of the 16 chlorinated acids. Concentrations are in the range 2.5–10 ng/μL. The TICs do not show limonene because the peak is saturated. Also not shown are dalapon at 2.64 minutes and acifluorfen at 12.7 minutes. The chromatograms were obtained with a DB-5 MS capillary column (same GC conditions), so there is a slight increase in the retention time of all compounds as compared to the HP-5MS capillary column. Dinoseb before 2,4-DB on the DB-5MS capillary column.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4325682&req=5

f4-aci-10-2015-001: TICs of the unspiked orange peel extract, orange peel extract spiked with the 16 chlorinated acids, and the reference standard of the 16 chlorinated acids. Concentrations are in the range 2.5–10 ng/μL. The TICs do not show limonene because the peak is saturated. Also not shown are dalapon at 2.64 minutes and acifluorfen at 12.7 minutes. The chromatograms were obtained with a DB-5 MS capillary column (same GC conditions), so there is a slight increase in the retention time of all compounds as compared to the HP-5MS capillary column. Dinoseb before 2,4-DB on the DB-5MS capillary column.
Mentions: The orange peel extract contained percent levels of limonene, and, despite all this, there was no shift in the retention times of the 16 test compounds in the spiked matrix relative to the reference standard, except for the switch in the elution order of 2,4-DB methyl ester and bentazon methyl, as shown in Figure 4, which occurred for both the matrix and the reference standard because a DB-5MS column was used for these measurements.

Bottom Line: Gas chromatography with quadrupole time-of-flight mass spectrometry (GC-QTOFMS) and soft ionization generated by a rare-gas plasma is described here for the determination of various chlorophenoxy acid methyl esters and a few chlorinated herbicides.This plasma-based, wavelength-selectable ionization source, which can use Xe, Kr, Ar, Ne, or He as the plasma gas, enables ionization of GC-amenable compounds with ionization energies below 8.4, 10, 11.6, 16.5, or 22.4 eV, respectively.Data generated with the Ar plasma and real matrices such as a peppermint extract, a plum extract, and an orange peel extract, spiked with 16 test compounds, indicate that the test compounds can be detected at 1-10 pg/μL of extract, and compounds such as menthone, limonene, eucalyptol, pinene, caryophylene, and other C15H24 isomers, which are present in the peppermint and the orange peel extracts at ppm to percent levels, do not appear to interfere with the determination of the chlorophenoxy acid methyl esters or the chlorinated herbicides, although there were matrix effects when the test compounds were spiked at 1-10 pg/μL of extract.

View Article: PubMed Central - PubMed

Affiliation: Agilent Technologies, Santa Clara, CA, USA.

ABSTRACT
Gas chromatography with quadrupole time-of-flight mass spectrometry (GC-QTOFMS) and soft ionization generated by a rare-gas plasma is described here for the determination of various chlorophenoxy acid methyl esters and a few chlorinated herbicides. This plasma-based, wavelength-selectable ionization source, which can use Xe, Kr, Ar, Ne, or He as the plasma gas, enables ionization of GC-amenable compounds with ionization energies below 8.4, 10, 11.6, 16.5, or 22.4 eV, respectively. The advantages of soft ionization include enhanced molecular ions, reduced fragmentation, and reduced background noise as compared to electron ionization. In the study presented here for two plasma gases, we demonstrate that Kr plasma, which is softer than Ar plasma, yields molecular ions with a relative intensity >60% for 11 of the 16 test compounds. When using this "tunable" plasma to ionize the analytes, there is the possibility for selective ionization and less fragmentation, which may lead to increased sensitivity and may help structure elucidation, especially when using high-resolution mass spectrometry that generates accurate masses within a few parts per million (ppm) mass errors. Data generated with the Ar plasma and real matrices such as a peppermint extract, a plum extract, and an orange peel extract, spiked with 16 test compounds, indicate that the test compounds can be detected at 1-10 pg/μL of extract, and compounds such as menthone, limonene, eucalyptol, pinene, caryophylene, and other C15H24 isomers, which are present in the peppermint and the orange peel extracts at ppm to percent levels, do not appear to interfere with the determination of the chlorophenoxy acid methyl esters or the chlorinated herbicides, although there were matrix effects when the test compounds were spiked at 1-10 pg/μL of extract.

No MeSH data available.


Related in: MedlinePlus