2
Experimental Details
Consumables
Part Number
Column:
TraceGOLD TG-5MS, 30 m × 0.25 mm × 0.25 μm
26098-1420
Septum:
Thermo Scientific BTO, 17 mm
31303211
Liner:
Thermo Scientific™ Splitless Straight Liner,
45350033
5 × 8 × 105 mm
Column ferrules:
100% graphite ferrules for Thermo Scientific™ 29053488
TRACE™ injector, 0.1–0.25 mm i.d.
Colum ferrules:
Graphite/Vespel
®
for transfer line 0.1–0.25 mm i.d.
29033496
Injection syringe:
10 μL fixed needle syringe for a Thermo Scientific™ 36500525
TriPlus™ Autosampler
Sample Handling Equipment
Part Number
System:
Thermo Scientific™ eVol™ Sample Dispensing System 66002-024
(containing Sample Dispensing System, eVol XCHANGE™
Syringes in 5, 50, and 500 µL volumes and eVol stand)
Vials and closures:
Thermo Scientific 9 mm Wide Opening Screw Thread 60180-599
Vial Convenience Kit, 2 mL Clear Vial with Patch, Blue
Polypropylene Closure with Clear PTFE/Blue Silicone Septa
Chemicals and Reagents
Part Number
Fisher Scientific™ HPLC grade acetone
A/0600/15
Fisher Scientific HPLC grade dichloromethane
D/1856/17
Fisher Scientific HPLC grade hexane
H/0406/15
Fisher Scientific HPLC grade water
W/0106/17
Preparation of Calibration Standard
A stock standard solution of 1000 µg/mL of phthalate esters listed in Table 1 was prepared in hexane / acetone (8:2 v/v)
(Standard A). This was then used to prepare standard solutions in hexane of 5000, 3000, 1000, 500, 300, and
100 ng/mL. These were Standards B–G. For construction of the calibration curve, the standards B–G were fortified with
benzyl benzoate as an internal standard to a level of 1000 ng/mL.
Sample Preparation
The standards and extracts were prepared in scrupulously clean glassware. Avoiding any contact with plastic is vital as
phthalates can contaminate glassware and blank samples very easily. Glass analytical syringes, glass pipettes, and
pesticide grade solvents were used for preparing samples.
Glassware was scrupulously cleaned by rinsing first with water and then with acetone and hexane. For accuracy, the
calibration samples were prepared using an eVol dispensing system. This avoided the use of plastic pipettes as the eVol
system has a glass syringe barrel and stainless steel dispensing needle. Any plastic containers were avoided to reduce
potential phthalate contamination in the sample preparation.
To prepare the spiked soft drink samples, 300 ng/mL and 1000 ng/mL of phthalate esters (listed in Table 2) prepared in
acetone were spiked into 5 mL of soft drink followed by the addition of 5 mL of dichloromethane containing 1000 ng/mL
internal standard. The solution mixture was shaken vigorously. An aliquot of organic layer was transferred to the GC vial.
A high injector temperature (320 °C) was used to release the high MW phthalates or any adsorbing phthalates in the
injector head. The high temperature resistant BTO septa were used.
Separation Conditions
Instrumentation:
Thermo Scientific™ TRACE™ GC Ultra gas chromatograph
Carrier gas:
Helium
Column flow:
1.0 mL/min, constant flow
Oven temperature:
80 °C (1 min), 10 °C/min, 320 °C (8 min)
Injector type:
Split/Splitless
Injector mode:
Splitless (1 min), 20 mL/min flow rate, constant septum purge
Injector temperature:
320 °C
