Total, Inorganic, and Organic Chloride in Hydrocarbons
UOP Method 588-12
Scope
This potentiometric method is for determining total and inorganic chloride, and calculating organic
chloride, in hydrocarbons. The method is applicable to samples with chloride concentrations of 1
mass-ppm or higher. For lower levels of chloride use UOP Method 991 “Chloride, Fluoride, and
Bromide in Liquid Organics by Combustion Ion Chromatography (CIC).” Iodide and/or bromide, if
present, are calculated as chloride. Samples that are polymerized by sodium biphenyl (such as
styrene) cannot be analyzed by this method. Results for samples containing ammonia and/or amines
may be biased high (see Note 1).
Reference
UOP Method 991, “Chloride, Fluoride, and Bromide in Liquid Organics by Combustion Ion
Chromatography (CIC),” www.astm.org
UOP Method 999, “Precision Statements in UOP Methods,” www.astm.org
Outline of Method
To determine total chloride, the hydrocarbon sample is weighed and transferred to a separatory
funnel containing toluene. Sodium biphenyl reagent is added to promote rapid conversion of the
organic chloride into inorganic chloride. Excess reagent is decomposed with alcohol and water, and
the phases are separated. The chloride containing aqueous phase is acidified, concentrated, acetone is
added, and the solution titrated potentiometrically.
Inorganic chloride determination is identical to total chloride except that the addition of sodium
biphenyl reagent is omitted. Organic chloride is then calculated as the difference between the total
chloride and inorganic chloride determinations.
Apparatus
References to catalog numbers and suppliers are included as a convenience to the method user.
Other suppliers may be used.
Balance, readable to 0.0001 g
Balance, readable to 0.01 g
IT IS THE USER'S RESPONSIBILITY TO ESTABLISH APPROPRIATE PRECAUTIONARY PRACTICES AND TO
DETERMINE THE APPLICABILITY OF REGULATORY LIMITATIONS PRIOR TO USE. EFFECTIVE HEALTH AND
SAFETY PRACTICES ARE TO BE FOLLOWED WHEN UTILIZING THIS PROCEDURE. FAILURE TO UTILIZE THIS
PROCEDURE IN THE MANNER PRESCRIBED HEREIN CAN BE HAZARDOUS. MATERIAL SAFETY DATA SHEETS
(MSDS) OR EXPERIMENTAL MATERIAL SAFETY DATA SHEETS (EMSDS) FOR ALL OF THE MATERIALS USED IN
THIS PROCEDURE SHOULD BE REVIEWED FOR SELECTION OF THE APPROPRIATE PERSONAL PROTECTION
EQUIPMENT (PPE).
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Nonconfidential UOP Methods are available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West
Conshohocken, PA 19428-2959, USA. The UOP Methods may be obtained through the ASTM website, www.astm.org, or by
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Beaker, 250-mL, tall, without spout, borosilicate glass, Wilmad-LabGlass, Cat. No. G-9906-002
Boiling chips, Fisher Scientific, Cat. No. 09-191-12
Bottles, glass, 60-mL, Fisher Scientific, Cat. No. 02-911-787
Cylinders, graduated, Class B, 10-, 25-, 50-, and 100-mL, Fisher Scientific, Cat. Nos. 08-550B, C,
D, and E, respectively
Desiccator, with plate, Fisher Scientific, Cat. No. 08-615B
Electrode, combination silver/glass Titrode Model 6.0430.100, Metrohm USA, Cat. No. 020948507
Flask, volumetric, Class A, 500-mL, Fisher Scientific, Cat. No. 10-208K
Funnel, separatory, 250-mL, Fisher Scientific, Cat. No. 10-437-5C
Hot plate, electric, capable of maintaining 150ºC, Fisher Scientific, Cat. No. 11-100-49H
Oven, drying, capable of operation at 110ºC, Fisher Scientific, Cat. No. 13-247-725G
Pipet, volumetric, Class A, 50-mL, Fisher Scientific, Cat. No. 13-650-2S
Pipet filler, Fisher Scientific, Cat. No. 13-681-102A
Stirring bars, Teflon-coated, Fisher Scientific, Cat. No. 14-512-148
Titrator, potentiometric, recording, ± 2000-mV range, 1-mV resolution, with dispenser having a
volume readout of 0.00 to 99.9 mL and 0.01% resolution, Titrando Model 904, Metrohm USA
Tongs, beaker, Fisher Scientific, Cat. No. 02-622
Tray, for ice bath, polypropylene, Fisher Scientific, Cat. No. 13-361-10
Reagents and Materials
References to catalog numbers and suppliers are included as a convenience to the method user.
Other suppliers may be used. Unless otherwise specified references to water mean deionized or
distilled water.
Acetone, 99.9% minimum purity, Fisher Scientific, Cat. No. A18-4
Cleaning pad, synthetic, mildly abrasive, Scotch-Brite™, Runco Office Supply, Cat. No. MMM-
96
Congo red paper, VWR, Cat. No. 60791-006
Detergent, cleaning compound, Liqui-Nox, Fisher Scientific, Cat. No. 04-322-15B
Desiccant, Drierite, indicating, 10- to 20-mesh, Fisher Scientific, Cat. No. 07-578-4A
Gloves, nitrile, Fisher Scientific, Cat. No. 11-395-19C
Ice, water
Isooctane, 99.9% minimum purity, Fisher Scientific, Cat. No. O301-4
Isopropyl alcohol, 99.9% minimum purity, Fisher Scientific, Cat. No. A416-4
Nitric acid, concentrated, Certified ACS Plus, Fisher Scientific, Cat. No. A200-212
Nitric acid, approximately 5N. Add 160 mL of concentrated nitric acid slowly to approximately
200 mL of water in a 500-mL volumetric flask. Dilute to the mark with water, cap and invert
several times to mix thoroughly.
588-12
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Pipet, disposable, LDPE, Fisher Scientific, Cat. No. 13-711-9AM
Potassium chloride, 99.995% minimum purity, Alfa Aesar, Cat. No. 87626, VWR. Oven dry an
aliquot before each use at 105ºC for 2.5 hours, and cool in a desiccator.
Silver nitrate, 0.1N solution, Fisher Scientific, Cat. No. SS72-4, see Silver Nitrate Standardization
Silver nitrate, 0.01N standard aqueous solution. Prepare by diluting the 0.1N solution, see Silver
Nitrate Standardization.
Sodium biphenyl reagent, commercially obtainable under the name of “Organic Halogen Reagent”
from GFS Chemicals. The reagent is packed in 18-mL bottles (hereafter referred to as “vials”).
One vial contains 13 to 15 milli-equivalents of active sodium. The reagent cannot be used after
the expiration date stated on the package (see Note 2).
Toluene, 99.9% minimum purity, Fisher Scientific, Cat. No. T324-4
Water, deionized or distilled
Wipers, Kimwipes, lint free, Fisher Scientific, Cat. No. 06-666A
Procedure
The analyst is expected to be familiar with general laboratory practices, the technique of titration,
and the equipment being used. Dispose of used reagents, materials, and samples in an
environmentally safe manner according to local regulations.
Silver–Silver Chloride Electrode Preparation and Reconditioning
Proper electrode preparation is essential to obtain reproducible and noise-free titration curves
having good endpoints. An electrode should be dedicated to chloride analysis. Prepare and
recondition the silver-silver chloride electrode as follows:
1. Clean the silver surface with a Scotch-Brite pad. Rinse with water and dry.
2. Weigh approximately 0.1 g of potassium chloride and place in a beaker. Using a graduated
cylinder, add 20 mL of 5N nitric acid and 80 mL of water to the beaker. Immerse the electrode;
and titrate to the endpoint with 0.1N silver nitrate.
3. Remove the electrode from the solution and rinse with water.
4. Wipe the excess silver chloride from the electrode with a wiper.
• The electrode should be cleaned after each titration by rinsing with water.
The freshly coated silver-silver chloride electrode may be stored in water or carefully dried using
wipers and stored for future use. It is necessary to repeat the electrode preparation when the AgCl
begins to peel from the surface.
Silver Nitrate Standardization
The 0.1N silver nitrate solution may be purchased at a certified concentration. Alternatively, the
solution may be standardized as follows.
1. Weigh 0.10 ± 0.01 g of dried potassium chloride to the nearest 0.0001 g into a clean, dry 250-
mL electrolytic beaker.
2. Using a graduated cylinder, add 100 mL of water and a stirring bar to the beaker. Add a few
drops of 5N nitric acid to acidify.
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