Page 102 - Geochemistry of Oil Field Waters

90 ANALYSIS OF OILFIELD WATERS

Procedure. The spectrochemical excitations used are the same as those
shown in the procedure to determine barium, etc., with the exception that
the spectral region is 2300-3300 8, first order and the slit is 10 p. The plate
development conditions are the same as those shown in the procedure to
determine barium, etc., and the microphotometer conditions are the same
except that the background and the intensity of only the following lines are
read: Be, 11, 3131.07 a, internal standard line, 3036.3 8; or if the 3131.07-8
line is too intense, the Be, 11, 3130.42-a line can be used.
To prevent precipitation and adsorption, immediately acidify the clean,
oil-free sample to a pH of approximately 1.5 with concentrated hydrochloric
acid. Store the sample for transportation to the laboratory, in a good quality
plastic bottle which previously was washed with dilute nitric acid, rinsed with
distilled water, and dried.
Transfer an aliquot of the sample estimated to contain 0.01-0.05 pg of
beryllium to a 100-ml beaker, adjust the pH to 0.5 with concentrated
hydrochloric acid, adjust the volume to about 30-50 ml with distilled water,
boil gently for 5 minutes, and then cool. Add 2 ml of the EDTA solution
and adjust the pH of the mixture to 7.0 with 0.5N sodium hydroxide. Add 2
ml of acetylacetone, readjust the pH to 7.0, mix thoroughly, and allow the
solution to stand for 15 minutes. Transfer the sample to a 125-ml Teflon-
stoppered, separatory funnel and adjust the volume to 75 ml with distilled
water, add 10 ml of chloroform, and shake the mixture vigorously for 2
minutes. After the phases separate, extract the chloroform phase and cen-
trifuge it. Aspirate the centrifuged extract into the plasma arc using the
above excitation conditions. For optimum accuracy, prepare duplicate
samples.
Develop the plates, make background corrections, and determine the rela-
tive intensity ratios for the following lines:
Be 3131.07 Be 3130.42
3036.3 and 3036.2
Determine the concentration of beryllium using a calibration curve pre-
pared by using 0.01-0.05 pg of beryllium standard. This concentration in
micrograms can be converted to milligrams per liter by this formula:
pg Be (from curve)
ml sample = mg/l Be+2
Less than 1 ppb of beryllium can be detected with this method, the
precision and accuracy of the method are about 2% and 496, respectively, of
the amount present.

Aluminum,

Petroleum-associated water containing more than 5 mg/l of aluminum can
be analyzed using the same procedure and internal standard that are