Page 200 - Geochemistry of Oil Field Waters

DETERMINATION OF OIL IN WATER 187

Apparatus. The necessary apparatus consists of:
(1) Microsyringe - evaporating flask (see Fig. 6.1): this assembly consists
of a single-neck flask of approximately 20 ml volume which tapers opposite
and slightly offset to the neck into a microsyringe equipped with a gas-tight
Teflon-tipped plunger and calibrated to measure 0-500 pl.
(2) 1,000-ml pear-shaped separatory funnel.
(3) Hotplate or hot-water bath: capable of being controlled in the range of
45O-55'~ at *~OC.
(4) 500-ml Berzelius, tall form beaker.

Reagents. The necessary reagents are:
(1) 50% hydrochloric acid solution, reagent-grade.
(2) pH paper indicating strip or pH meter.
(3) 1,1,2-trichlorotrifluoroethane (Freon TF) reagent-grade, purified,
48OC boiling point.

Sampling. Collect a composite or spot sample representative of stream to be
measured. Volume to be taken will be dependent on content of oily material
and should be in the range of 1-5 liters. Sample should be caught in glass
container.

Procedure. Extraction: adjust pH of entire sample to pH 5 or below using
hydrochloric acid added in small increments. Thoroughly mix the sample
and allow it to stand 15 minutes. Measure the volume of entire sample and
transfer to separatory funnel. Add portion of 1,1,2-trichlorotrifluoroethane
extraction fluid (see Note 1) to sample container, thoroughly rinsing any
adhering oil material. Add this and balance of fluorocarbon to separatory
funnel. Shake thoroughly for 5 minutes and let stand to separate layers.
Draw off fluorocarbon layer into suitable beaker, filtering any entrained
solids, if necessary, and warm gently to boiling point (see Note 2). Continue
boiling until volume remaining can be contained in measuring flask.
Transfer to measuring flask with fluorocarbon rinse of beaker, and
immerse the flask and contents into 500-ml beaker partially filled with water
and warmed to 65°C on hotplate or in hot-water bath. Be sure open neck of
flask is clear of upper edge of beaker (can be maintained by extension of
syringe piston). Continue until volume is reduced to that of syringe volume.
Draw fluid into syringe and increase heat slowly to remove last traces of
solvent, indicated by lack of bubbles forming in the syringe column.
Measure amount of oil material in graduated syringe using graduations
midway in syringe.
Note 1: for single extractions fluorocarbon volume should be one-tenth of
the original sample volume. In double extractions for better accuracy and
reproducibility use two volumes of fluorocarbon, each onetwentieth of the
original sample volume.
Note 2: although fluorocarbon is essentially considered nontoxic, the