Page 66 - Application Notebook - PFAS Analysis

No. SSI-LCMS-120

■ Quantitative Analysis
Triple quadrupole instruments are typically the The quantitative capabilities of a QTOF for PFAS
instruments of choice for quantitative analysis. The analysis were compared to a triple quadrupole mass
MRM optimization for the analysis of PFAS was spectrometer traditionally used for EPA Method
conducted on a Shimadzu LCMS-8045 triple 537.1. Since a TOF mass analyzer does not operate
quadrupole instrument. The MRM method was then in the same fashion as a quadrupole mass analyzer, a
transferred from LCMS-8045 to LCMS-9030 QTOF MRM width of 20 ppm was used for all product ions.
2
instrument. The method transfer from triple All calibration curves showed a r value greater than
quadrupole instrument to a QTOF instrument could 0.99 as required by EPA Method 537.1. Figure 2
be easily achieved due to similar front end for both compares the chromatograms at a sample
the instruments. Both instruments comprise of a concentration of 5 ppt for all new targets in EPA
thermally assisted ESI probe where the sample is Method 537.1.
sprayed and ionized at atmospheric pressure. The
ionized sample is then introduced through the In order to assess TOF stability, a precision and
sample introduction unit (desolvation line) into the accuracy study was conducted at 25 ppt. Table 3 and
vacuum chamber where the ion focusing units guide Table 4 show replicated 25 ppt injections for the
the ions to the quadrupoles. Effective use of triple QTOF and QQQ, respectively. Figure 3 compares the
quadrupole and QTOF MS provides a comprehensive LOQs from QTOF and QQQ, with the results for the
and accurate data acquisition and analysis. majority of compounds being less than 3 ng/L.

Figure 2: QTOF (top) vs QQQ (bottom) Chromatograms at 5ppt of GenX, ADONA, 9Cl-PF3ONS and 11Cl-PF3OUdS.

Table 3: Summary P&A with QTOF LCMS-9030.

QTOF 25 ppt P&A True Value Avg Avg.%REC %RSD Std Dev
PFBS 22.2 23.7 107 7.6 1.80
PFHxA 25 29 116 4.8 1.39
HFPO-DA 62.5 80.4 129 7.3 5.89
PFHpA 25 27.6 110 7.8 2.16
PFHxS 22.8 25.9 113 14.4 3.73
ADONA 25 46.2 185 6.1 2.80
PFOA 25 28.7 115 5.8 1.65
PFOS 23.1 21.7 94 23.1 5.00
PFNA 25 28.2 113 6.3 1.78
9Cl-PF3ONS 23.2 28 121 6 1.68
PFDA 25 25 100 6.3 1.56
N-MeFOSAA 25 29.2 117 11.3 3.31
N-EtFOSAA 25 25.9 104 23.6 6.11
PFUnA 25 24.4 98 7.7 1.88
11Cl-PF3OUdS 23.5 44.5 189 6.6 2.94
PFDoA 25 22.1 88 6.5 1.43
PFTriA 25 22.8 91 6.3 1.44
PFTreA 25 22.8 91 6.8 1.55