Cardinal Environmental Laboratories, LLC
Standard Operating Procedure
Procedure No.: 3030 Revision Date:
17/07
Subject: Alkalinity (Titrimetric) EPA 310.1
-------------------------------------------------------------------------------------------------
------
Approved By Title: Date Revised:
-------------------------------------------------------------------------------------------------
------
-------------------------------------------------------------------------------------------------
------
-------------------------------------------------------------------------------------------------
------
-------------------------------------------------------------------------------------------------
------
-------------------------------------------------------------------------------------------------
------
Alkalinity (Titrimetric) 310.1
Scope and Application
This method is applicable to drinking, surface, and saline waters;
domestic and industrial wastes. The method is suitable for all
concentration ranges of alkalinity; however appropriate aliquots should
be used to avoid a titration volume greater than 50mL
Matrix
Aqueous
Description
An aqueous sample's ability to neutralize an acid is termed "alkalinity
as calcium carbonate". Most water alkalinity is the result of
carbonates, bicarbonates and hydroxides, the alkalinity of a sample is
the measurement of these three primary components. The actual
value for alkalinity can vary greatly according to the pH selected for
the end point.
Definitions
Method Blank: aliquot of reagent water treated exactly as a sample
including exposure to all glassware, equipment, solvents, reagents,
internal standards, and surrogates used. Used to determine if
interferences or analytes are present in the lab environment.
Duplicate Sample: sample analyzed second time exactly the same way
as the first analysis. Used to calculate precision expressed as Relative
Percent Difference (RPD).
Precautions
Standard laboratory practices must be followed (see procedure 0010)
Sample Preservation and Preparation
Procedure 3030
Revised
17/07
A sample to be analyzed for alkalinity can be collected in either plastic
or glass containers. The sample should be cooled to 4°C. No further
preservation is required. Analysis is required prior to 14 days after sampling.
Apparatus
- pH Meter
- Erlenmyer flask
- Magnetic stirrer, stirbar
- 50, 10ml burets
Reagents
- Sodium Carbonate solution (Na2C03) 0.05N:
Weigh 2.5 ± 0.2g Na2CO3 (dried at 250°C for 4 hours and
cooled in a
desiccator) into l liter ultra pure water.
- Standard Sulfuric Acid (H 2S04) 0.1N:
Dilute 3ml concentrated H2SO4 to 1L with ultra pure water.
Standardize
against 40.0mls of 0.05N NaCO3 in 60mls ultra pure water by
titrating to a
pH of 5. Lift electrode. Rinse into flask. Cover with a watch
glass and boil
solution for 3 to 5 minutes. Cool, rinse, cover into flask,
continue titration
to pH inflection point.
Normality of H2SO4 = A X B
53.0 X C
Where:
A = g Na2CO3
B = mls Na2CO3 solution
C = mls acid used
- Standard Sulfuric Acid (H 2S04) 0.02N:
Dilute 200ml of 0.1000 N standard acid to 1L with ultra pure
water.
Standardize by titration of 15mls 0.05N Na2CO3 solution as
above.
Procedure 3030
Revised
17/07
Procedure
1.0 Sample Derivation
1.1 A preliminary titration of the sample may be helpful to determine
the correct
titrant to use for precise alkalinity measurement.
1.2 Place a volume of sample into Erlenmyer flask (volume used is a
function of step
1.1, use an appropriate amount to allow a sharp end point).
Several different
volumes should be titrated. Dilution with ultra pure water may be
necessary.
2.0 Sample Preparation
2.1 Place sample with stirbar on stir plate. Begin mixing, measure the
pH of the sample.
2.2 Begin to titrate with standard acid 0.2 or 0.02N slowly to a pH of
4.5.
Record the volume of titrant used. (use calculation A)
3.0 Sample Preparation (Low Level)
3.1 For samples with an alkalinity of <20 mg/l, titrate 200ml of sample
with 0.02N standard acid using a 10ml microburet.
3.2 Stop titration at pH 4.3 - 4.7 & record volume and exact pH.
3.3 Slowly add titrant to lower pH 0.3 units. Stop titration and record
the volume.
(use calculation B)
Calculations
A.) Potentiometric to pH 4.5
Alkalinity, mg/l CaCO3 = A X N X 50,000
mls sample
Where:
A = ml standard acid
N = Normality of standard acid
Procedure 3030
Revised
17/07
B.) Low Alkalinity Titration
Total Alkalinity, mg/l CaCO3 = (2B-C) X N X 50,000
mls of sample
Where:
B = ml titrant to first pH
C = total ml titrant to reach second pH
N = Normality of standard acid
Method Performance
See QAPP section 5.2.
Aqueous Precision = 20%, Aqueous Accuracy = 95-108%
Quality Control
* Each analytical batch analyzed for alkalinity must be
accompanied by a method
blank consisting of ultra pure water.
* All weights, volumes, comments etc. for each batch must be
entered in note book form for data review.
* Every tenth sample shall be run in duplicate and % RPD
calculated (see
procedure 0110 for calculations).
* Required recoveries for duplicates shall be determined using
historical data. The current acceptable limits for these
parameters are listed in procedure 0120.
* Failure to meet Quality Control acceptable limits requires
corrective action (see procedure 0150).
References
Methods for Chemical Analysis of Water and Wastes
EPA 600/4-79-020 March 1983
Method 310.1 pp. 310.1-1 thru pp. 310.1-3
Procedure 3030
Revised
17/07
National Environmental Methods Index. April 1994. Method 335.2. 31
March 2004. <http://www.nemi.gov>
Procedure 3030
Revised
17/07
