Determination of tyre wear particle (TWP) through microwave extraction of 6-PPDQ antioxidant

INSTRUMENT

• ETHOS X equipped with fastEX-24 eT extraction rotor
• 100-mL disposable glass vials (PN GB00122)
• Gas chromatograph with Mass Spectrometer detector (GC-MS)
• Analytical balance
• Vials for collection of extracts
• Glass funnels for filtration
• Glass fiber filters

STANDARD AND REAGENTS
For extraction Dichloromethane HPLC grade >99.9% (Rathburn chemical) and Sodium sulfate (Sigma Aldritch) were used. Each sample was spiked with labelled recovery standard (D10-Fluoranthene; Spex) For the GC-MS calibrarion curve a standard of 6-PPD (Sigma Aldrich) was employed.

SAMPLE INFORMATION
The sediments were collected in three replicates from two different sites along UK rivers. First site (urban) was on the Irk river in Greater Manchester while second (rural) was on Thames river in Wallingford, Oxfordshire.

ANALYTICAL PROCEDURE
Field samples were stored at -20°C in cleaned glass jars cautiously cleaned to avoid any contamination. Defrosted samples were mixed thoroughly using a metal spatula, to homogenize. 4 g of sample was decanted into a clean beaker, the weight was recorded accurately, and the samples were then dried with sodium sulphate. The sediments were then transferred into the glass vials of the fastEX-24 rotor. For the recovery essay all the sediments extracted were spiked with the recovery standard D10-Fluoranthene, an analogous compound to 6-PPD. 25 ml of mixture of DCM:Acetone 1:1 was added. The extraction procedure was carried out. After the extraction, samples were filtered on glass fiber filters and the vials were rinsed with additional solvent aliquots. Extracts and rinsates were collected and concentrated at low volumes (1.5 ml of solvents).

GC-MS QUANTIFICATION
Prior to GC analysis a step of cleaning through size exclusion chromatography was employed (Agilent HPLC 1200).
Injection was carried splitless mode in a GC 6890N Gas Chromatograph (Agilent, Santa Clara, CA, USA) equipped with HP5-MS column (30 m, 0.25 mm, 0.25 µm; Agilent J&W GC Columns). The injector was maintained at 250 °C. The injection quantity was 1.7 µL at a flow rate of 1.5 mL/min of He. The oven was held at 50 °C for 1.5 min, followed by a 30 °C/min increase to a final temperature of 260 °C, which was held for 10 minutes.
The detector was a 5975B Mass Spectrometer (Agilent, Santa Clara, CA, USA) working in SCAN/SIM mode. The range of SCAN was set at 50-800 m/z and SIM ions chosen were m/z 211, 212 and 268 (6-PPD fragments).
6PPD was quantified using a calibration curve of the 6PPD and the samples were recovery-corrected using the IS D10-Fluoranthene.