Hence, to collect the extractant phase, a micro-funnel was
used, the extractant layer was narrowed into the capillary
part of the micro-funnel, and using a syringe, it was simply
transferred to the injection port of the gas chromatograph.
This method is very simple, it can provide a high PF, and
using a micro-volume of a low-toxic solvent, it can be
categorized as an environmentally friendly method.
2 MATERIALS AND METHODS
2.1 Chemicals and supplies
The studied OPPs diazinon, malathion, and chlorpyrifos
were supplied from Sigma–Aldrich (St. Louis, MO,
USA). 1-Undecanol (≥97.5%), hydrochloric acid (37%),
analytical-grade sodium chloride (≥99%), NaOH (≥99%),
and chromatography-grade methanol, acetone, and acetonitrile
were obtained from Merck (Darmstadt, Germany).
Dihexyl ether (97%) was obtained from Fluka (Buchs,
Switzerland), and 1-octanol (≥95%) was supplied from
Sigma–Aldrich. Stock solutions of the pesticides with a
concentration of 1 mg/mL were prepared in methanol and
stored at 4
◦
C. The standard solutions were re-prepared every
2 weeks and the required working standard solutions were
prepared by their dilution.
2.2 Instrumentation
Syringe filters with nylon membranes (0.45 μm, Millex-HN,
nylon, Ireland) were used for phase separation. For the
chromatographic analysis of OPPs, a gas chromatograph
(GC–2014, Shimadzu, Japan) equipped with a flame ionization
detector (FID) and a splitless/split injector was utilized.
Separation of the target analytes was performed on a SPB–1
capillary column (100% dimethyl siloxane, film thickness of
0.25 μm, 30 m × 0.25 mm id) (Supelco, Bellefonte, USA),
and the carrier gas was helium (with a purity of 99.999%) that
was used at a constant linear velocity of 30 cm/s. A hydrogen
generator (OPGU–1500S, Shimadzu, Japan) was used to
produce the hydrogen required for FID. The FID temperature
was set to 300
◦
C. The injector was used in the splitless mode,
and its temperature was kept constant at 300
◦
C. The oven
temperature program was set as follows: 90
◦
C and held for
3 min, increased to 290
◦
C at 12 ◦
C/min, and held at this
temperature for 5 min.
2.3 Samples
The river water (Savad-kuh, Mazandaran, Iran), sea water
(Caspian Sea, Sari, Iran), and well water (Saveh, Iran) samples
were collected in amber glass containers and maintained
in the dark at 4◦C until analysis. No filtration or further
treatment was applied on the samples before extraction.