Sub-Femtogram Detection of Dioxins and Furans using Tandem Quadrupole Mass Spectrometer
Overcoming Legacy Obstacles with Innovative Approaches
Oral Presentation
Prepared by , R. Jones, K. Organtini, K. Rosnack, J. Romano, L. Mullin
Contact Information: [email protected]; 508-369-8311
ABSTRACT
Introduction
In the past magnetic sector mass spectrometers with electron ionization sources have been required to achieve the sensitivity, selectivity, and dynamic range required for the analysis of dioxins and furans extracted from environmental matrices. In this work a tandem quadrupole mass spectrometer incorporating new transfer optics and detector design has been developed with improvements to both sensitivity and dynamic range. Using an atmospheric pressure chemical ionization source, this GC/MS/MS instrument’s sensitivity for a dioxin and furan analysis was found to be 100 attograms on column.
Results and discussion
The system was optimized using the single component 2,3,7,8 TCDD sample. A dilution series was made from 1ng/µL to 100ag/µL. Once the optimal conditions for the ionization source, gas chromatograph and mass spectrometer has been determined for best sensitivity, various studies were conducted to explore the linearity, robustness and sensitivity of the system. The recorded peak intensities were approximately five times greater than had previously been observed on the previous instrument.
Reproducibility at a sample concentration of 500ag/µL was assessed using twelve successive injections. All isotope ratio errors were within the ±15% of the theoretical value, the tolerance permitted by relevant legislation1,2, with an average absolute error of 3.7%. The average signal to noise, using the peak-to-peak definition over a signal-free noise period of ten peak widths, was 38:1.
The linearity of the system was assessed by running 22 concentrations over the range of 100ag/µL to 1ng/µL and demonstrated linearity was within ±8% over the range of 100ag/µL to 100pg/µL with an r2 value of 0.998. Data above this upper concentration started to show saturation effects. All isotope ratios were within ±15% of the theoretical expected value.
The stability of the system was assessed by repeatedly injecting a 1000:1 dilution of an EPA1613 CS3 dioxin and furan standard. Analyte concentrations within this sample varied from 10fg/µL to 200fg/µL, with the majority of the 13C12 labeled components being of a concentration of 100fg/µL. 100 acquisitions were performed, and the 6800 peaks obtained were quantified and found to have an average standard deviation of 7.7%. The average absolute isotope ratio error of the 3400 ratios assessed was 3.2% with respect to the theoretical values, with only one measurement exceeding the ±15% legislative criteria.
An additional assessment of the instrument performance was made using a number of extracts from a variety of matrices. The results were in good agreement with previous analyses on a tandem quadrupole.
References
1. EPA Method 1613 (Revision B), U.S. Environmental Protection Agency (USEPA), Washington, DC, Sept. 1994.
2. Commission Regulation (EU) 589/2014, laying down methods of sampling and analysis for the control of levels of dioxins, dioxin-like PCBs and non-dioxin-like PCBs in certain foodstuffs.
Overcoming Legacy Obstacles with Innovative Approaches
Oral Presentation
Prepared by , R. Jones, K. Organtini, K. Rosnack, J. Romano, L. Mullin
Contact Information: [email protected]; 508-369-8311
ABSTRACT
Introduction
In the past magnetic sector mass spectrometers with electron ionization sources have been required to achieve the sensitivity, selectivity, and dynamic range required for the analysis of dioxins and furans extracted from environmental matrices. In this work a tandem quadrupole mass spectrometer incorporating new transfer optics and detector design has been developed with improvements to both sensitivity and dynamic range. Using an atmospheric pressure chemical ionization source, this GC/MS/MS instrument’s sensitivity for a dioxin and furan analysis was found to be 100 attograms on column.
Results and discussion
The system was optimized using the single component 2,3,7,8 TCDD sample. A dilution series was made from 1ng/µL to 100ag/µL. Once the optimal conditions for the ionization source, gas chromatograph and mass spectrometer has been determined for best sensitivity, various studies were conducted to explore the linearity, robustness and sensitivity of the system. The recorded peak intensities were approximately five times greater than had previously been observed on the previous instrument.
Reproducibility at a sample concentration of 500ag/µL was assessed using twelve successive injections. All isotope ratio errors were within the ±15% of the theoretical value, the tolerance permitted by relevant legislation1,2, with an average absolute error of 3.7%. The average signal to noise, using the peak-to-peak definition over a signal-free noise period of ten peak widths, was 38:1.
The linearity of the system was assessed by running 22 concentrations over the range of 100ag/µL to 1ng/µL and demonstrated linearity was within ±8% over the range of 100ag/µL to 100pg/µL with an r2 value of 0.998. Data above this upper concentration started to show saturation effects. All isotope ratios were within ±15% of the theoretical expected value.
The stability of the system was assessed by repeatedly injecting a 1000:1 dilution of an EPA1613 CS3 dioxin and furan standard. Analyte concentrations within this sample varied from 10fg/µL to 200fg/µL, with the majority of the 13C12 labeled components being of a concentration of 100fg/µL. 100 acquisitions were performed, and the 6800 peaks obtained were quantified and found to have an average standard deviation of 7.7%. The average absolute isotope ratio error of the 3400 ratios assessed was 3.2% with respect to the theoretical values, with only one measurement exceeding the ±15% legislative criteria.
An additional assessment of the instrument performance was made using a number of extracts from a variety of matrices. The results were in good agreement with previous analyses on a tandem quadrupole.
References
1. EPA Method 1613 (Revision B), U.S. Environmental Protection Agency (USEPA), Washington, DC, Sept. 1994.
2. Commission Regulation (EU) 589/2014, laying down methods of sampling and analysis for the control of levels of dioxins, dioxin-like PCBs and non-dioxin-like PCBs in certain foodstuffs.
