Synthetic Phenolic Antioxidants in Middle Distillate Fuels Analyzed by Gas Chromatography with Triple Quadrupole and Quadrupole Time-of-Flight Mass Spectrometry

Abstract

Methods for the selective determination and quantification of 10 synthetic phenolic antioxidants (SPA) in jet and diesel fuels have been developed. The analytical procedure involves no sample preparation and uses direct injection of the diluted parent fuel into the GC column. Gas chromatography with both triple quadrupole and quadrupole time-of-flight mass spectrometry was used to quantify synthetic phenolic antioxidants in the range of 0.1−20 mg/L. Precision was in the range of 3− 9%. The method is demonstrated to be rugged and robust and, since no extraction is required, does not require estimation of extraction efficiencies. It is generally suited to volatile SPA compounds included in jet and diesel fuel specifications. The method is appropriate for the estimation of SPA in fresh and in-service middle distillate fuels stored on military bases and tankers or in use on aviation or naval platforms.

Detailed Chemical Analysis Using Multidimensional Gas Chromatography–Mass Spectrometry and Bulk Properties of Low-Temperature Oxidized Jet Fuels

“…The alternative fuels, however, do not contain aromatics other than what may have been added during the manufacturing process as additives, for example, synthetic phenolic antioxidants. Strong positive library matches (match quality ≥ 700) in alternatively derived fuels for aromatic oxidized species, as indicated in Table , are likely the result of oxidation of the additives included in the product and are supported by previous analyses of antioxidant content in these fuels . Chromatograms of the alternatively derived fuels were generally far less complex, with fewer large peaks eluting after the dominant alkanes at the beginning of each heart-cut (Figure ).…”

Detailed Chemical Analysis Using Multidimensional Gas Chromatography–Mass Spectrometry and Bulk Properties of Low-Temperature Oxidized Jet Fuels

“…The alternative fuels, however, do not contain aromatics other than what may have been added during the manufacturing process as additives, for example, synthetic phenolic antioxidants. Strong positive library matches (match quality ≥ 700) in alternatively derived fuels for aromatic oxidized species, as indicated in Table , are likely the result of oxidation of the additives included in the product and are supported by previous analyses of antioxidant content in these fuels . Chromatograms of the alternatively derived fuels were generally far less complex, with fewer large peaks eluting after the dominant alkanes at the beginning of each heart-cut (Figure ).…”

Analysis of Phenolic Antioxidants in Navy Mobility Fuels by Gas Chromatography–Mass Spectrometry

“…The heart-cutting method is a practical method for the routine determination of each of the five hindered phenolic AOs in any type of fuel, down to 0.5 mg/L (MQL), with minimal interference from fuel. A GC–MS/MS method was also developed that is similar to a method reported by Webster et al However, we have found that, by employing a soft CI source, ion interferences are greatly reduced over what is encountered with traditional EI, thus enabling method quantification limits as low as 0.05 mg/L. Both of these analytical methods represent a significant advantage for routine analysis of phenolic AOs in fuels, over traditional HPLC–ECD, which is more labor-intensive and not capable of separating each of the individual phenolic AOs.…”

“…The GC–MS/MS method offers a more straightforward option to the heart-cutting GC–MS method. It requires minimal sample preparation, and with soft CI, analyte detection limits an order of magnitude lower than those shown in Webster et al can be achieved. However, it should be noted that the method detection limits are related to column performance, because as the column ages, more interfering ions can co-elute with the AO target analytes.…”

“…Initial trials using a 60 m, 100% dimethylpolysiloxane column and MS/MS operating in EI mode produced an unacceptably high background signal in fuel, as shown in Figure . Alternatively, using the SIM ions as described by Webster et al did not improve the EI background using the GC parameters in the Experimental Section. This may have been due to co-eluting compounds that would not be a factor if the Webster GC–MS/MS method is used.…”

Chemical Characterization and Quantitation of Phenols in Fuel Extracts by Using Gas Chromatography/Methane Chemical Ionization Triple Quadrupole Mass Spectrometry

“…The performance of the GC/positive-ion-mode (methane CI) QqQ method was evaluated by measurements on naturally occurring and additive phenols. This work expands previous QqQ studies wherein the focus was exclusively on additive phenols. , Methane reagent gas was selected for CI as it can be used to protonate all analyte molecules of interest via reactions that are less energetic than EI. , To evaluate the repeatability of the GC/(methane CI) QqQ method, intra- and interday measurements were performed using equimolar standard mixtures containing four phenol model compounds (2,6-di- tert -butylphenol, 2- tert -butylphenol, 2,6-dimethylphenol, and m -cresol). In addition, the response factors for the four phenols were determined.…”

Detailed Chemical Analysis Using Multidimensional Gas Chromatography–Mass Spectrometry and Bulk Properties of Low-Temperature Oxidized Jet Fuels

“…The alternative fuels, however, do not contain aromatics other than what may have been added during the manufacturing process as additives, for example, synthetic phenolic antioxidants. Strong positive library matches (match quality ≥ 700) in alternatively derived fuels for aromatic oxidized species, as indicated in Table , are likely the result of oxidation of the additives included in the product and are supported by previous analyses of antioxidant content in these fuels . Chromatograms of the alternatively derived fuels were generally far less complex, with fewer large peaks eluting after the dominant alkanes at the beginning of each heart-cut (Figure ).…”

Analysis of Phenolic Antioxidants in Navy Mobility Fuels by Gas Chromatography–Mass Spectrometry

“…The heart-cutting method is a practical method for the routine determination of each of the five hindered phenolic AOs in any type of fuel, down to 0.5 mg/L (MQL), with minimal interference from fuel. A GC–MS/MS method was also developed that is similar to a method reported by Webster et al However, we have found that, by employing a soft CI source, ion interferences are greatly reduced over what is encountered with traditional EI, thus enabling method quantification limits as low as 0.05 mg/L. Both of these analytical methods represent a significant advantage for routine analysis of phenolic AOs in fuels, over traditional HPLC–ECD, which is more labor-intensive and not capable of separating each of the individual phenolic AOs.…”

“…The GC–MS/MS method offers a more straightforward option to the heart-cutting GC–MS method. It requires minimal sample preparation, and with soft CI, analyte detection limits an order of magnitude lower than those shown in Webster et al can be achieved. However, it should be noted that the method detection limits are related to column performance, because as the column ages, more interfering ions can co-elute with the AO target analytes.…”

“…Initial trials using a 60 m, 100% dimethylpolysiloxane column and MS/MS operating in EI mode produced an unacceptably high background signal in fuel, as shown in Figure . Alternatively, using the SIM ions as described by Webster et al did not improve the EI background using the GC parameters in the Experimental Section. This may have been due to co-eluting compounds that would not be a factor if the Webster GC–MS/MS method is used.…”

Chemical Characterization and Quantitation of Phenols in Fuel Extracts by Using Gas Chromatography/Methane Chemical Ionization Triple Quadrupole Mass Spectrometry

“…The performance of the GC/positive-ion-mode (methane CI) QqQ method was evaluated by measurements on naturally occurring and additive phenols. This work expands previous QqQ studies wherein the focus was exclusively on additive phenols. , Methane reagent gas was selected for CI as it can be used to protonate all analyte molecules of interest via reactions that are less energetic than EI. , To evaluate the repeatability of the GC/(methane CI) QqQ method, intra- and interday measurements were performed using equimolar standard mixtures containing four phenol model compounds (2,6-di- tert -butylphenol, 2- tert -butylphenol, 2,6-dimethylphenol, and m -cresol). In addition, the response factors for the four phenols were determined.…”

Detailed Chemical Analysis Using Multidimensional Gas Chromatography–Mass Spectrometry and Bulk Properties of Low-Temperature Oxidized Jet Fuels

“…The alternative fuels, however, do not contain aromatics other than what may have been added during the manufacturing process as additives, for example, synthetic phenolic antioxidants. Strong positive library matches (match quality ≥ 700) in alternatively derived fuels for aromatic oxidized species, as indicated in Table , are likely the result of oxidation of the additives included in the product and are supported by previous analyses of antioxidant content in these fuels . Chromatograms of the alternatively derived fuels were generally far less complex, with fewer large peaks eluting after the dominant alkanes at the beginning of each heart-cut (Figure ).…”

Analysis of Phenolic Antioxidants in Navy Mobility Fuels by Gas Chromatography–Mass Spectrometry

“…The heart-cutting method is a practical method for the routine determination of each of the five hindered phenolic AOs in any type of fuel, down to 0.5 mg/L (MQL), with minimal interference from fuel. A GC–MS/MS method was also developed that is similar to a method reported by Webster et al However, we have found that, by employing a soft CI source, ion interferences are greatly reduced over what is encountered with traditional EI, thus enabling method quantification limits as low as 0.05 mg/L. Both of these analytical methods represent a significant advantage for routine analysis of phenolic AOs in fuels, over traditional HPLC–ECD, which is more labor-intensive and not capable of separating each of the individual phenolic AOs.…”

“…The GC–MS/MS method offers a more straightforward option to the heart-cutting GC–MS method. It requires minimal sample preparation, and with soft CI, analyte detection limits an order of magnitude lower than those shown in Webster et al can be achieved. However, it should be noted that the method detection limits are related to column performance, because as the column ages, more interfering ions can co-elute with the AO target analytes.…”

“…Initial trials using a 60 m, 100% dimethylpolysiloxane column and MS/MS operating in EI mode produced an unacceptably high background signal in fuel, as shown in Figure . Alternatively, using the SIM ions as described by Webster et al did not improve the EI background using the GC parameters in the Experimental Section. This may have been due to co-eluting compounds that would not be a factor if the Webster GC–MS/MS method is used.…”

Chemical Characterization and Quantitation of Phenols in Fuel Extracts by Using Gas Chromatography/Methane Chemical Ionization Triple Quadrupole Mass Spectrometry

“…The performance of the GC/positive-ion-mode (methane CI) QqQ method was evaluated by measurements on naturally occurring and additive phenols. This work expands previous QqQ studies wherein the focus was exclusively on additive phenols. , Methane reagent gas was selected for CI as it can be used to protonate all analyte molecules of interest via reactions that are less energetic than EI. , To evaluate the repeatability of the GC/(methane CI) QqQ method, intra- and interday measurements were performed using equimolar standard mixtures containing four phenol model compounds (2,6-di- tert -butylphenol, 2- tert -butylphenol, 2,6-dimethylphenol, and m -cresol). In addition, the response factors for the four phenols were determined.…”