DBP
Water Sample Chlorination
* This procedure is for the chlorination of water samples prior to DBP analysis
Prior Experiments Needed
 DOC measurement of sample
 Preparation of Cl2 stock solution (see “DBP-Chlorination Procedure.xls)
 Preparation of buffer solution (see “DBP-Chlorination Procedure.xls)
Supplies needed
* Based on 1 sample
Reagents
 <1 ml from a 10-13% sodium hypochlorite (NaOCl) stock solution
 3 drops of sodium sulfite solution
 Hach reagents for free chlorine measurement
Equipment
 volumetric flasks (for dilution of stock solution during concentration check)
 1 ml plastic syringe
 22 gauge, 3” luer lock needle
 25 gauge, 5/8” luer lock needle
 40 ml sample vial or 72 ml sample bottle with cap for sample
 Hach Spectrophotometer
Procedure
A) Chlorine Dose Calculation
Typical Chlorine to DOC ratios are 1:1 for up to 24 hour SDS conditions. 3:1 ratios are common
for 7-day FP conditions. A more detailed procedure can be found in the file: “DBP-Chlorination
Procedure.xls”
C1V1 = C2V2
C1 = Stock Solution Cl2 Conc. = changes with time
V1 = Volume of Stock Solution added to 42 ml vial = dependent variable
C2 = Desired Cl2 Conc. in sample = # [DOC] + 7.6[NH3]
# is the amount of chlorine dose in the ratio Cl2 : DOC = # : DOC
V2 = Volume of sample = 42 ml
The stock solution concentration should be about 100,000 mg/L. This concentration will vary
with time (i.e. days), so a new stock solution concentration will need to be checked each time.
The stock solution will need to be diluted to be able to measure the concentration on the Hach
Spectrophotometer (see “DBP-Chlorination Procedure.xls)
02/17/16
1
106751079
B) Sample Chlorination
1) Measure the sample DOC
2) Adjust the pH of the sample to the desired pH (This is most easily accomplished by adjusting
a larger volume needed, i.e. 100 or 200 ml, and wasting the extra sample). Then add the
appropriate amount of phosphate buffer (see “Buffer Solution” binder section). The buffer
concentration in the sample should usually be 1 mM.
3) Fill sample vial to top so no headspace is present. This can best be achieved by filling the
sample vial just above the top and slip the septa on from the side.
4) Place a 5/8” - 25 gauge needle in the septa of the vial (Figure 1)
5) Inject the appropriate chlorine dose via a 3” - 22 guage needle plunged to the bottom of the
sample vial (Figure 1). During the injection, pull the dosing needle upward to more evenly
distribute the chlorine in the sample. The chlorine will displace an equal amount of sample
out the 5/8” needle.
6) Store sample at 20oC for desired time period
5/8” exhaust needle
3” injection needle
Figure 1
C) Chlorine Residual Measurement
Most often, the free chlorine residual needs to be measured to ensure that all the chlorine was not
consumed in the reaction, leading to a chlorine limited reaction. The free chlorine measurement
must be performed prior to any DBP analysis where the free chlorine must first be bound.
D) Stop chlorination
To end the chlorination process by binding the free chlorine, add 3 drops of sodium sulfite
solution to (10 g Na2SO3 / 100 ml MQ) to the 40 ml samples.
QA/QC
DBP analysis, following the chlorination of samples, can have a high variability in results due to
the many steps and variables in the process. It is recommended that triplicate samples be
provided for a minimum of 10% of the samples to quantify the variability in results. Duplication
for all samples is ideal, but very time consuming.
02/17/16
2
106751079