21 Table 4. Instrument detection limit in pg on column for the 19 native PAHs in DCM solvent


Compound name IDLs pg on column


Naphthalene


2 - methyl Naphthalene


1 - methyl Naphthalene


Acenaphthylene Acenaphthene Dibenzofuran Fluorene


Phenanthrene Anthracene Fluoranthene Pyrene


Benz[a]anthracene Chrysene Benzo[b]


fluoranthene Benzo[k]


fluoranthene Benzo[a]pyrene


Dibenzo[a,h] anthracene


Indeno[1,2,3-cd] pyrene


Benzo[g,h,i] perylene


Repeatability


Repeatability was tested by n=10 consecutive injections of a 20 ng/mL QC in water and 20 ng/mL QC in soil. The QCs were prepared spiking blank matrices. Results are reported in Figure 4. Overall %RSD was <5.5% for water and <15% for soil matrix.


Instrument robustness for the analysis of PAHs in environmental samples according to EPA Method 8270


System robustness and suitability for high-throughput analysis was assessed for a total of n=136 samples and 52 hours of consecutive injections, without any GC and MS maintenance (liner change, column trimming, MS tune). Details on the batch are reported in Figure 5.


Tune check


Tuning verification was performed after each series of samples, every 6 hours, injecting 1 µL of a tuning verification solution containing DFTPP at 20 µg/mL, acquired in full scan. Tune verification criteria reported in EPA Method 8270 were automatically verified by the system suitability test (SST) in Chromeleon CDS (Figure A1 in Appendix). At the end of the batch, tune verification was still passing the specifications.


Calibration check


Calibration check throughout the batch was done by injecting the calibration standards at different levels. The last two samples of the batch were the lowest (2.5 ng/mL) and the second to lowest (5 ng/mL) calibration points. (The accuracy in the back-calculation of these concentrations was still within ±10%.)


QCs


QCs for water and soil matrices, at three different levels (10, 1,000, and 10,000 ng/ mL) were prepared and injected every 17 samples. Calculated concentrations were accurate and consistent over the batch and were ±20% of the amount spiked (Figures 6 and 7).


Figure 7. Calculated value of QC soil, blank matrix spiked at 1,000 ng/mL. Calculated values are consistent and accurate (±15%) after 52 consecutive hours of injections and n=136 samples.


Figure 6. Calculated value of QC water blank matrix spiked at 10 ng/mL


0.51 0.67


0.41 0.33


6.94 1.24


1.73 0.86


6.59 1.76


4.36 1.48


0.97 0.30


0.42


0.59 0.51 0.42 0.58 0.45 0.64 0.39 0.58 0.49 0.33 0.37


0.50


MDLs water pg on column


0.44 0.42


0.71


0.40 2.27 0.61 1.04 1.69 2.92 1.84 1.57 0.66 0.49 1.59


1.11


MDLs soil pg on column


0.48 0.64


0.51


0.73 0.81 0.65 1.46 1.33 1.40 1.73 1.94 0.76 3.45 5.71


7.60


Figure 4. Peak area precision calculated in blank water and blank soil spiked at 20 ng/mL


Figure 5. Part of the batch used for robustness assessment. The batch contained 8 series of 17 samples each, namely 1 tuning mix, 1 calibration verification (CCV), 6 QCs (QC low, middle, and high for water and soil matrices) and 9 extracts of water and soil, randomly chosen. A total of n=136 samples were injected, for 52 hours of consecutive injections.


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