ALTERNATE TEST PROCEDURE (ATP) 

VALIDATION STUDY REPORT

For

Free and Total Chlorine Using Disposable “Planar” Reagent-Filled 

Cuvettes 

Revised

8/15/13 

HACH COMPANY

5600 LINDBERGH DRIVE

LOVELAND, CO 805378

Page 1 of 34
1.0 Background

The objective of this study is to evaluate Hach’s disposable Planar Reagent-Filled 

Cuvette (PRFC) method for the measurement of free, total, and combined free and total 

chlorine (Hach Methods 10260, 10270 and 10280) against the USEPA reference method 

SM-4500 Cl G for approval and use in USEPA regulatory drinking water programs. The 

methods are applicable to measure chlorine (Free and/or total) between 0.2 and 2.0 mg/L 

Cl2. The methods use disposable planar reagent-filled cuvettes (PRFCs) that are based on 

the standard (approved) DPD (N, N-diethyl-p-phenylenediamine) reaction (See Figure 1). 

The absorbance of the Wurster Dye is measured at 510 nm and the intensity of the 

absorbance is directly proportional to the concentration of chlorine. The DPD-filled

planar cuvettes, when interfaced with the pumping and optical system of the instrument, 

act as a sampling, mixing and measurement vessel. The PRFCs are in the form factor 

similar to a popsicle stick (~85 mm x11 mm x 1 mm, see Figure 2) and contain all of the 

required reagents to perform a DPD based chlorine test (Free and Total).

Figure 1: Mechanism for the reaction of DPD with Chlorine

Figure 2: Schematic of the disposable reagent-filled planar cuvette for Free and Total 

Chlorine (Note that the amount of DPD placed on the chip for the 30μL sample is in 

exact proportion to the amount of DPD placed in the Hach Powder Pillows for a 10 mL 

sample)

Page 2 of 34
 For this ATP study a prototype benchtop instrument was used to make the chlorine 

measurements (Figure 3). It is envisioned that the commercial version of this prototype 

will contain up to 4 slots to make up to 4 simultaneous measurements using PRFCs. This 

will allow drinking water facilities the capability to measure other colorimetric

parameters in the field beyond chlorine in approximately the same amount of time it takes 

them to perform a single chlorine measurement today. Figure 4 shows a schematic for 

the future embodiment of the instrument that would have 4 individual ports for 

measurement. The future system will use the same cuvettes, wavelength, optical path, 

and mixing protocol as prototype instrument used in this study. 

Figure 3: Prototype breadboard setup used to make the free and total chlorine 

measurements for the ATP study 

Page 3 of 34
Figure 4: Future Industrial design of a hand-held 4 port instrument 

Chlorine measurements were performed by drawing sample into the cuvette, mixing the 

sample with the pre-filled reagent(s), followed by an optical measurement at 510 nm after 

the reaction is complete across the width of the cuvette (11 mm optical path). Sample 

measurement, mixing, timing, and measurement are all controlled by a pumping system 

within the instrument. The only step that needs to be performed to make a measurement 

is to connect the PRFC(s) into the instrument and place it in the water and draw in the 

sample (The instrument uses a conductivity probe to determine when the chips have been 

dipped in the sample). The rest of the measurement is controlled by the system.

Page 4 of 34
The detailed approach to make a free and total chlorine measurement using PRFCs is as 

follows: 

1) Draw 30 μL of sample into the cuvette. 

2) Mix the sample with the DPD and buffer 

3) Wait 30 seconds for the reaction to be complete 

4) Draw the sample into the optical path and take and optical measurement at 510 

nm for free chlorine

5) Move the sample up to mix with the potassium iodide 

6) Wait 180 seconds for complete reaction of monochloramine (Also dichloramine 

and trichloramine, if present). 

7) Draw the sample back into the optical path to make a measurement for total 

chlorine 

8) Move the sample up to mix with the ascorbic acid to bleach out the Wurster’s Dye 

9) Wait 1 minute

10) Draw the sample back into the optical path and make a measurement to zero out 

any imperfections from the cuvette and blank on the sample. 

Total Testing time for Free and Total Chlorine~4.5 minutes

Note: In step 7 the blanking is performed after the measurement to improve analytical 

performance. If the sample was zeroed prior to reaction with the DPD it was noticed 

that the chlorine demand of the polystyrene cuvette impacted analytical performance. 

 

The method was compared to the standard Hach DPD methods (0.2-2.0 mg/L Cl2) for 

free and total chlorine in a 3 lab ATP study (Hach method numbers 8021 (Free) and 8167 

(Total)). The method was found to perform well in both high and low ionic strength 

matrices between pH 6 and 8.8. The method also generated MDLs for free chlorine of 

0.023 mg/L and total chlorine of 0.027 mg/L. 

 

1.1 Method Justification

The most widely used EPA approved method for the measurement of chlorine in the field 

(SM 4500 Cl-G) involves the use of powder pillows and colorimeter. Powder pillowbased methods are very dependent on technique and can be prone to inter-operator error. 

Errors in wavelength selection, sample measurement, reagent addition, mixing, and/or 

timing can cause variability in the chlorine measurement. Scratched cuvettes can also 

cause problems in measurements. The proposed method using disposable PRFCs 

automates the entire process from sampling to measurement eliminating all of the

potential areas for operator error because each planar cuvette is barcoded to identify the 

method, all of the reagents for the test are contained in the cuvette, and the mixing and 

timing of the sample reaction are controlled by the instrument.

 

1.2 Method Equivalency

The QC acceptance criteria for the method were determined based on analytical 

performance relative to SM 4500 Cl G (DPD powder pillow method) for both free Cl2

Page 5 of 34
and total Cl2. Method performance was based on side-by-side studies against DPD 

powder pillows using 3 analytical performance metrics: 

1) MDLs in low and high ionic strength matrices

2) Precision and accuracy of the method at the ~2.0 mg/L Cl2 in low and high 

ionic strength matrices

3) Spike recoveries relative to SM4500-Cl G (DPD powder pillow) in ground 

water and surface water matrices at various pH values (3 different ground 

water matrices and 3 different surface water matrices from 6 different 

locations tested in 3 different laboratories) 

4) Monochloramine interference on a free chlorine measurement relative to the 

approved method 

The recoveries that are calculated for this method were calculated against the results 

generated by Hach Free and Total chlorine powder pillows (SM4500-Cl G). This was 

due to the difficulty of preparing accurate and stable chlorine standards. Chlorine 

standards are inherently unstable and degrade over time causing issues with repetitive 

precision based tests such as MDL studies. For our studies the same sample was used for 

both the reagent-filled cuvette tests and the powder pillow tests. 10 mL samples were 

prepared and measured with the disposable cuvettes first (30 μL) immediately followed 

by the powder pillow tests (~10 mL). Both samples were reacted with DPD (either in the 

chip or with the powder pillow) within 30 seconds to ensure the same concentration was 

measured using both methods. This eliminated the variable of chlorine degradation 

between measurements and allowed for better correlation between the methods.

Below is a summary of the pooled data from the three different labs that were normalized 

to a single concentration for each specific test. Note: Due to the instability of chlorine 

standard each location was not able to prepare exactly the same concentration samples for 

each test.

Test

% recovery for 

Free Cl chip

% recovery for 

Total Cl chip

MDL (mg/L) or 

%RSD Free Cl2 

PRFC

MDL (mg/L) or % 

RSD Free Cl2 

Powder Pillow

MDL (mg/L) or 

%RSD Total Cl2 

PRFC

MDL (mg/L) or % 

RSD Total Cl2 

Powder Pillow

0.2 mg/L Low Ionic Strength (MDL) 97% 85% 0.019 0.019 0.025 0.050

0.2 mg/L High Ionic Strength (MDL) 89% 93% 0.025 0.020 0.033 0.040

2 mg/L Low Ionic Strength 103% 93% 2.30% 2.50% 2.88% 2.25%

2 mg/L-High Ionic Strength 102% 92% 5.22% 3.38% 4.15% 4.02%

GW Matrix Sample 48% 291%

below detection 

limit

below detection 

limit

below detection 

limit

below detection 

limit

GW Matrix Spike (Spike to ~2 mg/L) 104% 95% 1.27% 1.25% 0.88% 0.62%

SW Matrix Sample 75% 94%

below detection 

limit

below detection 

limit

below detection 

limit

below detection 

limit

SW Matrix Spike (Spike to ~2 mg/L) 103% 97% 2.54% 2.25% 1.41% 0.86%

GW Matrix pH 6 (Spike to ~2 mg/L) 105% 98% 2.00% 1.34% 1.46% 1.00%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 104% 97% 1.16% 1.86% 0.69% 0.56%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 103% 96% 1.40% 2.01% 1.56% 0.49%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 103% 95% 2.43% 1.24% 1.43% 0.69%

SW Matrix pH 6 (Spike to ~2 mg/L) 105% 97% 1.32% 1.80% 2.00% 1.07%

SW Matrix pH7.4 (Spike to ~2 mg/L) 104% 96% 2.69% 2.12% 1.07% 0.64%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 103% 95% 3.86% 1.77% 3.30% 1.19%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 104% 95% 1.72% 1.40% 4.67% 3.26%

Pooled Data (All sites normalized)

Page 6 of 34
The pooled results for the planar reagent-filled cuvette (PRFC) tests compared favorably 

in many individual tests for both free and total chlorine. Based on this data it was 

determined that the method is “equally effective” in testing free and total chlorine when 

compared to the reference method. We also believe that the method will be significantly 

improved upon once automated production equipment is used to manufacture the PRFCs

and the commercial version of the instrument is available. 

1.3 Analytes

Free Chlorine [CAS# 7782-50-5] 

Total Chlorine (Can be composed of one or more of the following) 

Monochloramine [CAS# 14611-51-9] 

Dichloramine [CAS# 3400-09-7] 

Tri-Chloroamine [CAS# 10025-85-1] 

 

2.0 Study Implementation

The Hach Company was responsible for setting up the ATP study plan with collaboration 

from Glynda Smith and Steve Wendelken of the EPA. The test plans were executed at 3 

facilities using 2 different matrices at each facility (Ground water and Surface water). 

The facilities were:

1) Hach Company Laboratories (Loveland, CO surface water and Greely, CO 

ground water. 5/3/2011-5/16/2011 

a. Hach Company laboratories were selected because to the simplified 

logistics and to reduce cost

2) Test America labs (2 labs, Cedar Falls and Phoenix) were selected through their 

corporate manager who found labs that had available time to perform the 

analyses. Each lab was paid $60/hour for their work. Each study took 

approximately 40 hours at each laboratory to complete 

a. Cedar Falls 5/23/2011-5/27/2011 and 7/10/2011-7/13/2011 (Samples: 

Cedar Falls, IA ground water and Chicago, IL surface water)

b. Phoenix Test America Laboratory 5/16/201-5/20/2011 (Fond du Lac, WI 

ground water and Phoenix, AZ surface water) 

The labs were supplied with 2 Hach prototype PRFC measurement systems, disposable 

PRFCs to run the tests, reagents to prepare standards, a Hach Pocket Colorimeter, Hach 

free and total Chlorine powder pillows, and Hach cuvettes for the colorimeters. 

2.1 Study Schedule

Hach Loveland Lab Studies: 5/3/2011-5/16/2011 

Cedar Falls, IA Test America Laboratory 5/23/2011-5/27/2011 and 7/10/2011-7/13/2011 

Phoenix, AZ Test America Laboratory 5/16/201-5/20/2011 

2.2 Sample Collection 

• Samples were collected following standard USEPA sampling procedures

• Samples measured in Loveland, CO 

Page 7 of 34
o Surface Water: Loveland Tap water samples were collected directly from 

the taps in the Hach Loveland facility

o Ground Water: Greeley, CO ground water was collected from Hach 

employee’s well directly outside of his house and directly transported to 

the Hach Laboratories

• Samples measured in Cedar Falls IA

o Surface Water: Chicago, IL surface water samples were collected from at

190 South LaSalle Street, 25th Floor Chicago, IL 60603 and shipped to the 

Hach Laboratories and then subsequently shipped to the Cedar Falls, IA 

Test America Laboratory

o Ground Water: Cedar Falls, IA ground water samples were collected 

directly from the tap at the Cedar Falls, IA Test America Laboratory

• Samples measured in Phoenix, AZ 

o Surface Water: Phoenix, AZ surface water samples were collected directly 

from the tap at the Phoenix, AZ Test America Laboratory

o Ground Water: Fond du Lac, WI ground water samples were collected at 

45 S. Main St., Fond du Lac, WI 54935 and directly shipped to the Phoenix 

Test America Laboratories

All samples that were shipped to the labs did not have any chlorine residual by the 

time they reached the test laboratories due to the stability of free chlorine.

 

2.3 Types of Analyses Performed

The matrix of tests that were performed at each site is below. 

Page 8 of 34
All free chlorine tests were performed using a free chlorine standard prepared from stock 

6%-8% sodium hypochlorite. All total chlorine tests were performed using a 

monochloramine standard that was prepared by mixing the appropriate amount of 

ammonium chloride standard with a free chlorine standard prepared from sodium 

hypochlorite. The monochloramine interference test was performed by measuring the 

free chlorine result of a 2.0 mg/L monochloramine standard. 

2.4 Study Plan Deviations

There were some issues that were encountered during the testing with the 

prototype system (instrument and cuvettes). There were several tests that were 

performed that the software deemed “bad” tests and did not record those results. 

There were also some communication issues between the computers and the 

“prototype breadboards” that happened sporadically. These issues seemed to 

cause issues for the technicians running the tests with keeping count of how many 

tests they performed. In all, there were 18 total tests (9 pairs) that were missed 

out of 912 tests (456 pairs). We believe that in most cases the combination of the 

relatively high frequency of system errors with the complicated test plans caused 

Hach DPD 

Free Chlorine 

Powder 

Pillow

Hach DPD 

Total Chlorine 

Powder 

Pillow

Hach Free 

Chlorine 

(Disposable 

PRFC)

Hach Total 

Chlorine 

(Disposable 

PRFC)

Standard Verification 0 0 0 0

0.2 mg/L Low Ionic Strength 7 7 7 7

0.2 mg/L High Ionic Strength 7 7 7 7

2 mg/L Low Ionic Strength 7 7 7 7

2 mg/L-High Ionic Strength 7 7 7 7

GW Matrix Sample 4 4 4 4

GW Matrix Spike (Spike to ~2 mg/L) 4 4 4 4

SW Matrix Sample 4 4 4 4

SW Matrix Spike (Spike to ~2 mg/L) 4 4 4 4

Monochlormaine Interference at 2 mg/L NH2Cl 4 4 4 4

GW Matrix pH 6 (Spike to ~2 mg/L) 4 4 4 4

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 4 4 4

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 4 4 4

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH 6 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 4 4 4

Total # of Tests 64 64 64 64

Page 9 of 34
the technicians to miscount the tests that they ran at different facilities. That 

being said we believe that the 892 data points that were generated in the test plan 

should suffice as a very comprehensive data set. 

The individual deviations are outlined below: 

1) Loveland, CO : There were 4 missing reading from the Loveland, CO total 

chlorine set of tests. There were two 2.0 mg/L high ionic strength spikes, one 2.0 

mg/L low ionic strength spike, and one 2.0 mg/L surface water spike. The reason 

these tests were not performed was there were communication issues with the 

“prototype breadboard instrument” that made the technician running the samples 

assume the test had been performed. It was an oversight by the technician 

running the samples. 

2) Phoenix, AZ: One missing reading was found in the Phoenix data (2.0 mg/L high 

ionic strength spike). The reason this data point is missing is unknown. It is 

assumed the operator who performed the analysis miscounted how many 

replicates that he ran and missed by one. Since it was a single data point out of 

the 151 pairs of tests (302 total tests) performed in Phoenix we don’t believe it 

should have much impact on the interpretation of the data. 

3) Cedar Falls IA: All of the total chlorine data in Cedar Falls had to be rerun on a 

second date because the preparation of the monochloramine standard was 

performed wrong. A large excess of ammonia was added to the free chlorine 

standard, which made the total chlorine standard mostly di- and tri-chloramines 

rather than monochloramine. Although this did not impact the results it did not 

represent what would traditionally be measured in drinking water systems that use 

monochloramine as a disinfectant. Therefore, we decided to re-run the tests at a 

later date to ensure a more homogeneous set of data between the three sites.

There were 4 missing total chlorine data points in the second set of tests 

performed in Cedar Falls. They were all 2.0 mg/L spikes of ground water that 

were pH adjusted (2 pH 7.4, 1 pH 6.0, and 1 pH 8.2). The reasons that these 

samples were missing were oversights by the technician performing the tests. 

During the second sets of test there were several communication and analyses 

issues the led to invalid results that were not reported by the prototype system. 

Because of these different hardware issues it is believed that the technician 

performing the analyses lost count of the different tests he was performing.

There also was one missing free chlorine test (2.0 mg/L spike into low ionic 

strength water). We believe this was an oversight by the technician performing 

the tests.

There was a major outlier in the low ionic strength 2 mg/.L total chlorine spiked 

samples. The disposable PRFC test reported a value of 0.05 mg/L for a ~2.0 

mg/L total chlorine spike. The best rationale for this outlier was that the chip did 

not have DPD in the sample channel of the PRFC and therefore no color was 

generated to measure. 

3.0 Method Procedure and Data

Page 10 of 34
Method is attached. 

3.1 Validation Study Demonstration Data 

All data is summarized below from each individual site for each specific analyte (Free or 

total chlorine). Tables 7 and 8 show compiled sets of data with all data normalized to the 

same concentration (Each site did not necessarily spike to exactly 2 mg/L so the data was 

normalized to 2.0 mg/L for all of the spike concentrations) 

 

Table 1: Loveland Free Chlorine Data

LOVELAND 

FREE Cl2 # of reps

Hach 

Disposable 

Chips Free 

Chlorine 

Ave Conc

Hach DPD 

Free 

Chlorine 

Powder 

Pillow Ave 

Conc

Free 

Chlorine 

Hach PPA 

Chip % 

Recovery

Free 

Chlorine 

Hach PPA 

Chip % RSD 

(MDL For 

0.2 mg/L 

standards)

Free Chlorine Hach 

Powder Pillow % RSD 

(MDL For 0.2 mg/L 

standards)

0.2 mg/L Low Ionic Strength 7 0.21 0.22 96% 0.014 0.012

0.2 mg/L High Ionic Strength 7 0.26 0.27 96% 0.025 0.017

2 mg/L Low Ionic Strength 7 1.96 1.89 104% 0.5% 3.2%

2 mg/L-High Ionic Strength 7 1.80 1.79 100% 7.2% 2.8%

GW Matrix Sample 4 0.01 0.02 33% 12.2% 0.0%

GW Matrix Spike (Spike to ~2 mg/L) 4 1.91 1.81 105% 1.5% 0.0%

SW Matrix Sample 4 0.43 0.42 103% 5.4% 3.6%

SW Matrix Spike (Spike to ~2 mg/L) 4 2.03 1.94 105% 1.7% 3.4%

GW Matrix pH 6 (Spike to ~2 mg/L) 4 2.08 1.93 108% 3.5% 0.5%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 2.05 1.95 105% 1.2% 2.1%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 2.04 1.98 103% 1.7% 3.7%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 2.01 1.90 106% 4.1% 1.6%

SW Matrix pH 6 (Spike to ~2 mg/L) 4 2.11 2.00 106% 0.8% 1.4%

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 2.06 2.00 103% 4.2% 3.0%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 2.10 2.06 102% 1.9% 3.2%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 2.04 1.96 104% 2.4% 1.7%

Page 11 of 34
Table 2: Phoenix Free Chlorine Data 

Table 3: Cedar Falls Free Chlorine Data

PHOENIX 

FREE Cl2 # of reps

Hach 

Disposable 

Chips Free 

Chlorine 

Ave Conc

Hach DPD 

Free 

Chlorine 

Powder 

Pillow Ave 

Conc

Free 

Chlorine 

Hach PPA 

Chip % 

Recovery

Free 

Chlorine 

Hach PPA 

Chip % RSD 

(MDL For 

0.2 mg/L 

standards)

Free Chlorine Hach 

Powder Pillow % RSD 

(MDL For 0.2 mg/L 

standards)

0.2 mg/L Low Ionic Strength 7 0.23 0.21 111% 0.022 0.025

0.2 mg/L High Ionic Strength 7 0.18 0.20 90% 0.042 0.038

2 mg/L Low Ionic Strength 7 1.97 1.87 106% 3.9% 3.0%

2 mg/L-High Ionic Strength 6 1.94 1.84 106% 1.2% 1.8%

GW Matrix Sample 4 0.01 0.05 16% 15.8% 54.2%

GW Matrix Spike (Spike to ~2 mg/L) 4 2.00 1.90 106% 1.0% 2.0%

SW Matrix Sample 4 2.02 1.89 107% 1.8% 1.5%

SW Matrix Spike (Spike to ~2 mg/L) 4 1.95 1.86 105% 0.3% 0.8%

GW Matrix pH 6 (Spike to ~2 mg/L) 4 0.39 0.37 106% 1.5% 2.6%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 2.03 1.91 107% 1.0% 0.6%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.99 1.89 105% 1.9% 0.5%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.99 1.91 104% 1.6% 1.6%

SW Matrix pH 6 (Spike to ~2 mg/L) 4 2.05 1.98 103% 2.0% 2.6%

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 1.97 1.90 104% 2.7% 2.2%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.96 1.89 104% 7.0% 0.5%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.95 1.84 106% 1.5% 1.5%

CEDAR 

FALLS FREE 

Cl2 # of reps

Hach 

Disposable 

Chips Free 

Chlorine 

Ave Conc

Hach DPD 

Free 

Chlorine 

Powder 

Pillow Ave 

Conc

Free 

Chlorine 

Hach PPA 

Chip % 

Recovery

Free 

Chlorine 

Hach PPA 

Chip % RSD 

(MDL For 

0.2 mg/L 

standards)

Free Chlorine Hach 

Powder Pillow % RSD 

(MDL For 0.2 mg/L 

standards)

0.2 mg/L Low Ionic Strength 7 0.18 0.21 85% 0.033 0.040

0.2 mg/L High Ionic Strength 7 0.17 0.21 81% 0.023 0.024

2 mg/L Low Ionic Strength 6 1.90 1.88 101% 1.1% 0.9%

2 mg/L-High Ionic Strength 7 1.83 1.81 101% 5.8% 5.0%

GW Matrix Sample 4 0.63 0.68 94% 3.9% 0.9%

GW Matrix Spike (Spike to ~2 mg/L) 4 1.95 1.91 102% 1.6% 1.2%

SW Matrix Sample 4 0.00 0.03 15% 35.3% 40.0%

SW Matrix Spike (Spike to ~2 mg/L) 4 1.81 1.82 99% 4.6% 2.5%

GW Matrix pH 6 (Spike to ~2 mg/L) 4 1.84 1.83 101% 1.0% 0.7%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 1.86 1.84 101% 1.6% 2.8%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.94 1.91 101% 0.8% 0.9%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.90 1.89 100% 1.4% 0.7%

SW Matrix pH 6 (Spike to ~2 mg/L) 4 1.93 1.85 104% 1.3% 1.8%

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 1.92 1.83 105% 1.1% 1.6%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.88 1.84 102% 1.3% 1.1%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.89 1.85 102% 1.7% 1.5%

Page 12 of 34
Table 4: Loveland Total Chlorine Data 

Table 5: Phoenix Total Chlorine Data 

LOVELAND 

TOTAL Cl2 # of reps

Hach 

Disposable 

Chips Total 

Chlorine 

Ave Conc

Hach DPD 

Total 

Chlorine 

Powder 

Pillow Ave 

Conc

Total 

Chlorine 

Hach PPA 

Chip % 

Recovery

Total 

Chlorine 

Hach PPA 

Chip % RSD 

(MDL For 

0.2 mg/L 

standards)

Total Chlorine 

Hach Powder 

Pillow % RSD 

(MDL For 0.2 mg/L 

standards)

0.2 mg/L Low Ionic Strength 7 0.16 0.20 82% 0.010 0.017

0.2 mg/L High Ionic Strength 7 0.16 0.19 85% 0.015 0.022

2 mg/L Low Ionic Strength 6 1.97 2.02 98% 3.5% 1.0%

2 mg/L-High Ionic Strength 5 1.66 1.78 93% 1.8% 1.1%

GW Matrix Sample 4 0.03 0.06 52% 285.5% 110.9%

GW Matrix Spike (Spike to ~2 mg/L) 4 1.66 1.81 92% 2.1% 0.8%

SW Matrix Sample 4 0.29 0.33 86% 9.4% 1.2%

SW Matrix Spike (Spike to ~2 mg/L) 3 1.83 1.85 99% 0.9% 0.3%

GW Matrix pH 6 (Spike to ~2 mg/L) 4 1.69 1.74 97% 1.8% 1.4%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 1.78 1.84 97% 5.7% 0.7%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.76 1.83 96% 1.4% 0.5%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.70 1.81 94% 1.5% 1.0%

SW Matrix pH 6 (Spike to ~2 mg/L) 4 1.77 1.80 99% 1.5% 0.6%

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 1.74 1.76 99% 1.0% 0.7%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.69 1.73 98% 4.0% 1.2%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.64 1.70 96% 1.6% 0.9%

PHOENIX 

TOTAL Cl2 # of reps

Hach 

Disposable 

Chips Total 

Chlorine 

Ave Conc

Hach DPD 

Total 

Chlorine 

Powder 

Pillow Ave 

Conc

Total 

Chlorine 

Hach PPA 

Chip % 

Recovery

Total 

Chlorine 

Hach PPA 

Chip % RSD 

(MDL For 

0.2 mg/L 

standards)

Total Chlorine 

Hach Powder 

Pillow % RSD 

(MDL For 0.2 mg/L 

standards)

0.2 mg/L Low Ionic Strength 7 0.20 0.21 96% 0.027 0.018

0.2 mg/L High Ionic Strength 7 0.19 0.20 95% 0.023 0.012

2 mg/L Low Ionic Strength 7 1.92 1.96 98% 0.9% 0.7%

2 mg/L-High Ionic Strength 7 1.79 1.92 93% 0.9% 0.8%

GW Matrix Sample 4 0.04 0.01 708% 6.3% 11.5%

GW Matrix Spike (Spike to ~2 mg/L) 4 1.85 1.90 97% 0.5% 0.6%

SW Matrix Sample 4 0.50 0.48 104% 0.6% 0.4%

SW Matrix Spike (Spike to ~2 mg/L) 4 1.76 1.86 94% 1.6% 1.4%

GW Matrix pH 6 (Spike to ~2 mg/L) 4 1.88 1.89 99% 5.1% 2.6%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 1.83 1.89 97% 0.8% 0.5%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.81 1.90 95% 1.4% 0.7%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.80 1.90 95% 0.5% 0.7%

SW Matrix pH 6 (Spike to ~2 mg/L) 4 1.81 1.93 94% 2.2% 1.8%

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 1.75 1.89 93% 0.5% 0.8%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.70 1.87 91% 3.0% 0.4%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.69 1.84 92% 0.5% 1.6%

Page 13 of 34
Table 6: Cedar Falls Total Chlorine Data

CEDAR 

FALLS 

TOTAL Cl2 # of reps

Hach 

Disposable 

Chips Total 

Chlorine 

Ave Conc

Hach DPD 

Total 

Chlorine 

Powder 

Pillow Ave 

Conc

Total 

Chlorine 

Hach PPA 

Chip % 

Recovery

Total 

Chlorine 

Hach PPA 

Chip % RSD 

(MDL For 

0.2 mg/L 

standards)

Total Chlorine 

Hach Powder 

Pillow % RSD 

(MDL For 0.2 mg/L 

standards)

0.2 mg/L Low Ionic Strength 7 0.14 0.18 78% 0.035 0.099

0.2 mg/L High Ionic Strength 7 0.17 0.17 98% 0.047 0.069

2 mg/L Low Ionic Strength 7 1.62 1.93 84% 36.7% 2.8%

2 mg/L-High Ionic Strength 7 1.80 1.98 91% 3.5% 0.4%

GW Matrix Sample 4 0.10 0.09 115% 1.8% 1.4%

GW Matrix Spike (Spike to ~2 mg/L) 4 1.93 2.00 97% 1.4% 0.7%

SW Matrix Sample 4 0.12 0.13 94% 81.5% 68.3%

SW Matrix Spike (Spike to ~2 mg/L) 4 1.90 1.96 97% 1.8% 0.7%

GW Matrix pH 6 (Spike to ~2 mg/L) 3 1.84 1.91 96% 1.1% 0.3%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 2 1.87 1.93 97% 0.4% 0.8%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 3 1.86 1.93 96% 2.1% 0.3%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.82 1.90 96% 2.0% 0.5%

SW Matrix pH 6 (Spike to ~2 mg/L) 4 1.94 1.98 98% 2.3% 0.5%

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 1.93 1.97 98% 1.6% 0.5%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 1.91 1.98 97% 1.7% 1.9%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 1.95 2.03 96% 9.0% 6.5%

Page 14 of 34
Table 7: All sites Normalized Free Chlorine Data

Table 8: All sites Normalized Total Chlorine Data

Test

Number of 

Samples

% recovery for 

Free Cl chip

MDL (mg/L) or 

%RSD Free Cl2 

Chip

MDL (mg/L) or % 

RSD Free Cl2 PP

0.2 mg/L Low Ionic Strength (MDL) 21 97% 0.019 0.019

0.2 mg/L High Ionic Strength (MDL) 21 89% 0.025 0.020

2 mg/L Low Ionic Strength 20 103% 2.30% 2.50%

2 mg/L-High Ionic Strength 20 102% 5.22% 3.38%

GW Matrix Sample 12 48%

below detection 

limit

below detection 

limit

GW Matrix Spike (Spike to ~2 mg/L) 12 104% 1.27% 1.25%

SW Matrix Sample 12 75%

below detection 

limit

below detection 

limit

SW Matrix Spike (Spike to ~2 mg/L) 12 103% 2.54% 2.25%

GW Matrix pH 6 (Spike to ~2 mg/L) 12 105% 2.00% 1.34%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 12 104% 1.16% 1.86%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 12 103% 1.40% 2.01%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 12 103% 2.43% 1.24%

SW Matrix pH 6 (Spike to ~2 mg/L) 12 105% 1.32% 1.80%

SW Matrix pH7.4 (Spike to ~2 mg/L) 12 104% 2.69% 2.12%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 12 103% 3.86% 1.77%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 12 104% 1.72% 1.40%

Pooled Data (All sites normalized)

Test

Number of 

Samples

% recovery for 

Total Cl chip

MDL (mg/L) or 

%RSD Total Cl2 

Chip

MDL (mg/L) or % 

RSD Total Cl2 PP

0.2 mg/L Low Ionic Strength (MDL) 21 85% 0.025 0.050

0.2 mg/L High Ionic Strength (MDL) 21 93% 0.033 0.040

2 mg/L Low Ionic Strength 20 98% 23.13% 2.24%

2 mg/L-High Ionic Strength 19 92% 4.15% 4.02%

GW Matrix Sample 12 290%

below detection 

limit

below detection 

limit

GW Matrix Spike (Spike to ~2 mg/L) 12 95% 0.88% 0.62%

SW Matrix Sample 12 94%

below detection 

limit

below detection 

limit

SW Matrix Spike (Spike to ~2 mg/L) 11 97% 1.41% 0.86%

GW Matrix pH 6 (Spike to ~2 mg/L) 11 98% 1.46% 1.00%

GW Matrix pH 7.4 (Spike to ~2 mg/L) 10 97% 0.69% 0.56%

GW Matrix pH 8.2 (Spike to ~2 mg/L) 11 98% 1.56% 0.49%

GW Matrix pH 8.8 (Spike to ~2 mg/L) 12 95% 1.43% 0.69%

SW Matrix pH 6 (Spike to ~2 mg/L) 12 96% 2.00% 1.07%

SW Matrix pH7.4 (Spike to ~2 mg/L) 12 97% 1.07% 0.64%

SW Matrix pH 8.2 (Spike to ~2 mg/L) 12 95% 3.30% 1.19%

SW Matrix pH 8.8 (Spike to ~2 mg/L) 12 95% 4.67% 3.26%

Pooled Data (All sites normalized)

Page 15 of 34
Table 9: Monochloramine Interference

 3.1.1 Calibration

In future embodiments of the system each disposable PRFC will be barcoded so that the 

instrument can identify the parameter, range, and calibration associated with the reagent

lots. Therefore, for this ATP study, slightly different calibration curves were used for 

each lot of PRFCs. The specific calibration equations for each site are listed below. 

Each calibration was linear from 0-2.0 mg/L Cl2. 

Loveland Free Chlorine: Concentration=2.971*abs 

Loveland Total Chlorine: Concentration=3.299*abs+0.01 

Phoenix Free Chlorine: Concentration=2.928*abs 

Phoenix Total Chlorine: Concentration=3.281*abs+0.022 

Cedar Falls Free Chlorine: Concentration=2.928*abs 

Cedar Falls Total Chlorine: Concentration=3.281*abs+0.022 

 3.1.2 Initial Demonstration of Capability

MDL’s were determined using 7 standards at about 0.2 mg/L Cl2. Precision was defined 

by the %RSD at about 2.0 mg/L Cl2. Accuracy was defined as the % recovery relative to 

the DPD powder pillow method. All of the data is summarized in Tables 1-8. 

 3.1.3 QC Controls

Due to the instability of chlorine standards QC controls were not used in this study.

 3.1.4 Precision and Accuracy

Precision was defined by the %RSD at about 2.0 mg/L Cl2. Accuracy was defined as the 

% recovery relative to the DPD powder pillow method. All of the data is summarized in 

Tables 1-8. 

3.2 Holding Time/Storage Stability

A holding time study was not required for this ATP study. 

4.0 Data Analysis and Discussion

All testing that was performed on the Hach Disposable PRFCs were performed on 

prototype bench top equipment that incorporated the same optics and pumping system 

that will be incorporated into the commercial hand-held system. It is the goal of Hach to 

MONOCHLORAMINE

INTERFERENCE PRFC Powder pillow

Average Monochloramine Interference 

(12 measeurements) 6.3% 4.0%

Page 16 of 34
commercialize a hand-held system that has the capability to perform 4 simultaneous 

analyses using the same measurement paradigm as the breadboard instrument. Hach 

understands that to receive EPA approval the 4-slot handheld system will have to 

undergo similar testing that was performed in this study to ensure similar analytical 

performance

Standard and Spike Preparation 

Unfortunately because of the instabilities of the chlorine standards and spikes we could 

not evaluate the recoveries of the disposable cuvette and powder pillow methods relative 

to a known spike concentration. Therefore, all recovery calculations were based on the 

recovery of the PRFCs relative the results obtained by the Hach powder pillow method 

(SM4500-Cl G). To minimize drift of the prepared spiked samples the samples were run 

on the PRFC system and then immediately run using the Hach powder pillow method. 

Results are discussed below.

Free Chlorine 

MDL’s in Low and High Ionic Strength Water 

The MDL for the disposable cuvettes compared well against the powder pillow 

tests in both low and high ionic strength waters. For the pooled data both 

methodologies (PRFCs and Powder pillows) obtained the same MDL (0.19 mg/L 

Cl2) in low ionic strength water. In high ionic strength water the PRFC method 

obtained a pooled MDL of 0.025 mg/L and the powder pillow method obtained an 

MDL of 0.020 mg/L. Based on this data we consider the PRFC method equally 

sensitive for detecting free chlorine. 

Spike Recoveries/Accuracy in Low and High Ionic Strength Water 

There was very good agreement between the PRFC method and the Hach powder 

pillows for low and ionic strength water that were spiked to approximately 2 

mg/L free Cl2. The pooled average recovery for the 2 mg/L Cl2 spiked samples 

were 103% in low ionic strength and 102% in high ionic strength. Based on this 

data we consider the PRFC method equally accurate at measuring free chlorine in 

low and high ionic strength water. 

Matrices

The pooled average spike recovery for all matrices spiked to ~2 mg/L free 

chlorine samples was 103.9% (N=120 samples including SW and GW with all pH 

adjustments; spike recovery was calculated relative to the average powder pillow 

results). The %RSD for the same pooled samples was 2.1% for the PRFC tests 

and 1.7% for the powder pillow test (N=120 samples). Based on this data we 

consider the PRFC method equally effective at recovering and detecting free 

chlorine in different matrices at different pH values.

Monochloramine Interference on a Free Chlorine Test 

The free chlorine interference from a 2.0 mg/L monochloramine standard was 

4.0% for the free chlorine powder pillow and 6.3% for the PRFC’s. This 

difference is likely due to the powder pillow measurement being made 

Page 17 of 34
immediately after dissolution of the powder and the chip measurement being 

made at ~30 seconds. If the powder pillow measurement was made at ~20 

seconds it would be expected to have a slightly lower monochloramine 

interference. 

Total Chlorine 

MDL’s in Low and High Ionic Strength Water 

The MDL for the PRFC method compared well against the powder pillow tests. 

For the pooled data the PRFC method obtained an MDL of 0.025 mg/L Cl2 and 

the Hach powder pillow method obtained an MDL of 0.05 mg/L Cl2. In high 

ionic strength water the PRFC method obtained a pooled MDL of 0.033 mg/L and 

the powder pillow method obtained an MDL of 0.040 mg/L. Based on this data 

we consider the PRFC method equally sensitive for detecting total chlorine.

Spike Recoveries/Accuracy in Low and High Ionic Strength Water 

There was very good agreement between the PRFC method and Hach powder 

pillows for low and ionic strength water that were spiked to approximately 2 

mg/L total Cl2. The pooled average recovery for the 2 mg/L Cl2 spiked samples 

were 92% in low ionic strength and 93% in high ionic strength. Based on this 

data we consider the PRFC method equally accurate at measuring total chlorine in 

low and high ionic strength water. 

Matrices

The pooled average spike recovery for all matrix spiked 2 mg/L total chlorine 

samples was 96.5% (N=114 samples included SW and GW with all pH 

adjustment; spike recovery was calculated relative to the average powder pillow 

results). The %RSD for the same pooled samples was 2.1% for the PRFC tests 

and 1.3% for the powder pillow test (N=114 samples). Based on this data we 

consider the PRFC method equally effective at recovering and detecting total

chlorine in different matrices at different pH values.

5.0 Conclusions

The Hach disposable cuvette method compared very well against the approved powder 

pillow method. We expect the analytical performance to improve significantly once the 

reagents are deposited on to the disposable cuvettes with an automated manufacturing

line and the instrument is commercial ready and out of the prototype phase. Once the 

manufacturing line is commissioned and the hand-held instrument is in the final form 

factor Hach plans on generating another set of data at a single laboratory to verify the 

hand-held system performance in addition to providing the EPA with a system to 

evaluate internally.

Page 18 of 34
APPENDIX A.

VALIDATION STUDY PLAN

The spreadsheet below describes the validation study plan that was executed at each 

facility. 

General testing procedure for Hach 

chips (Provided to the testing labs) 

Overview: 

This is intended to be a guide for operation of the PPA instrument for outside 

technical personnel. The detailed test plan is covered in a separate document. This 

Hach DPD 

Free Chlorine 

Powder 

Pillow

Hach DPD 

Total Chlorine 

Powder 

Pillow

Hach 

Disposable 

Chips Free 

Chlorine

Hach 

Disposable 

Chips Total 

Chlorine

0.2 mg/L Low Ionic Strength 7 7 7 7

0.2 mg/L High Ionic Strength 7 7 7 7

2 mg/L Low Ionic Strength 7 7 7 7

2 mg/L-High Ionic Strength 7 7 7 7

GW Matrix Sample 4 4 4 4

GW Matrix Spike (Spike to ~2 mg/L) 4 4 4 4

SW Matrix Sample 4 4 4 4

SW Matrix Spike (Spike to ~2 mg/L) 4 4 4 4

Monochlormaine Interference at 2 mg/L NH2Cl 4 4 4 4

GW Matrix pH 6 (Spike to ~2 mg/L) 4 4 4 4

GW Matrix pH 7.4 (Spike to ~2 mg/L) 4 4 4 4

GW Matrix pH 8.2 (Spike to ~2 mg/L) 4 4 4 4

GW Matrix pH 8.8 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH 6 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH7.4 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH 8.2 (Spike to ~2 mg/L) 4 4 4 4

SW Matrix pH 8.8 (Spike to ~2 mg/L) 4 4 4 4

Total # of Tests 64 64 64 64

Page 19 of 34
contains information that may be considered “helpful hints” on standard handling and 

instrument operation. 

Background:

 Drinking water is purified in the US by a series of steps that involve mechanical 

(settling) means. Water is chemically decontaminated by one of two methods: direct 

chlorination or reaction with monochloramine. The tests for the two primary residuals 

(Cl2 or NH2Cl) are termed “free” and “total”, and the sum of the two methods is termed 

“free and total”. Hach “powder pillow” test methods (Hach method 8021) are the 

standard for most drinking water systems in the US, so the new PPA chip method (Hach 

method 10260) results will be compared to the powder pillow method results. As a rule 

during the testing procedure, samples should be tested by both methods whenever 

possible and as temporally close together as possible.

Handling of standards:

 Aqueous chlorine standards are inherently unstable. In aqueous solutions chlorine 

gas is in equilibrium with hypochlorous acid and its conjugate base hypochlorite. When 

the solution is left open to the atmosphere, chlorine gas will leave the solution, causing a 

downward drift in the concentration. Thus, chlorine solutions should be made as close to 

measurement time as possible and kept tightly covered. Samples should be read on the 

instrument (aka “breadboard”), then immediately read with a powder pillow. 

 Tap water has residual chlorine/monochloramine content when it comes out of the 

faucet. Like all chlorine solutions, the chlorine content of tap water goes down with time. 

Time in pipes will also cause the chlorine content to drop; therefore when a draw of tap 

water is needed, the tap water should be run full open for at least five minutes before a 

sample is taken to insure consistency between runs. Additionally, large volumes of water 

(>1000mL) should be used. The bulk of samples this size (and the increased 

volume/surface area ratio) helps keep the chlorine concentration relatively constant over 

the life of the experiment.

 Gloves should be used at all times when hands will be in contact with the 

solutions or with the chips, as skin oils have a chlorine demand. 

Spiking calculations:

 Spiking solutions requires calculations based on the initial concentration of the 

standard solution. Each batch of standard solution will be different and the exact 

concentration of the standard is listed on the vial label. This is the concentration that 

should be used in calculations. The most basic equation for calculating the volume 

needed of a concentrated standard to reach a particular end concentration of a diluted 

standard is 

M1V1 = M2V2

where M1 = concentration of the concentrated standard (in mg/L), M2 = concentration of 

the diluted solution (the solution being spiked)(in mg/L), V1 = volume of the 

concentrated standard (in mL), and V2 = the target concentration of the spiked solution 

(in mL).

 The equation is rearranged to isolate the volume of the concentrated standard (that 

which will be measured and added to the solution being spiked): 

V1 = M2V2 / M1

 So to spike a 10 mL DI water sample with a 0.2 mg/L spike using a 65 mg/L 

standard, the equation will read: 

Page 20 of 34
V1 = (0.2 mg/L)(10 mL) / (65 mg/L) = 0.031 mL = spiking volume 

It is important to remember that drinking water samples will have some residual 

chlorine. The residual chlorine must be taken into account when calculating the 

additional chlorine needed. For example, Loveland, CO tap water has 0.4 mg/L Cl2

residual. Thus to spike to 1.75 mg/L requires only an additional 1.35 mg/L Cl2 from the 

spike. 

 Before testing on chips, run a powder pillow test using the calculated spike to be 

sure that the spike will give the desired concentration (within 0.05 mg/L). It has been 

observed that occasionally the calculated volume does not give the target spike; this may 

be due to a release of chlorine immediately upon opening the ampule. If the initial test 

does not give the desired concentration, adjust the spiking volume. 

After the chlorine standard is opened it will immediately start to lose chlorine. 

Therefore, on-the-fly adjustments to the volume are required; as a rule of thumb, if the 

chlorine content is 10% low on a run, the spike should be increased for the next run. 

Spiking and Data Acquisition Procedure:

 General procedure: Obtain ~1000-1500mL of the unspiked water to be tested (e.g. 

distilled (low ionic strength) water, high ionic strength water, surface water, ground 

water, pH adjusted water) and place it in a large beaker between the two breadboards. 

Have a pipetteman (and fresh tip for each water type), colorimeter vial and cap, small 

plastic sample cup, and Excel spreadsheet ready. 

1) Withdraw 10.0 mL unspiked water from the beaker with the pipetteman and 

place it in the colorimeter vial.

2) Using good laboratory practices open the chlorine standard ampule (or in the 

case of total chlorine the monochloramine standard). After each withdrawal 

cap the ampule with parafilm, taking care to avoid getting cut by the sharp 

edges of the ampule. 

3) With a micropipetteman withdraw the calculated amount of chlorine and add 

it to the unspiked water. Cap the vial and shake vigorously for 2-3 seconds. 

a. For the first run, it is advisable to get a reading of chlorine content 

using a powder pillow to be sure that the chlorine content from the 

spike is correct.

b. If the powder pillow reading show that the chlorine content of the 

spikes solution is correct, wash the vial 3x with DI water and restart 

the procedure, moving on to the next step. 

4) Check to make sure that the instrument is reading “present sample”.

5) Pour the contents of the vial into the sample cup. 

6) Lift the cup up to the chip until the chip is touching the bottom of the cup. 

a. The instrument will read “remove sample”

7) Remove the sample.

8) Repeat the presentation of the sample on the second instrument. 

9) Pour the sample back into the vial.

10) Set a zero for the pocket colorimeter by placing the vial in the colorimeter, 

returning the cover, and pressing the “zero” button (on the left). 

Page 21 of 34
11) Open the appropriate powder pillow (free or total chlorine) (see below for 

procedure for using the powder pillow) and add it to the vial. Cap and mix the 

vial.

12) After the prescribed wait period (30 seconds for Free chlorine, 3 min for Total 

chlorine) take a measurement using the pocket colorimeter. Be sure that the 

white diamond on the vial is facing you. 

13) Rinse the vial 3x with DI water. Use the same vial for all measurements.

Using the instrument (breadboard): 

 The PPA instrument is intended to be straightforward to use. There are only a few 

steps: opening the chip bag, preparing the instrument, placing the chip in the slot, 

presenting the sample to the chip, removing the sample from the chip, and reading the 

output. Here are a few pointers for the operation of the instrument: 

1) Opening the chip bag. Wear gloves whenever handling or preparing to handle 

chips. To avoid cutting either the chip or the bag of desiccant, be sure to push the 

solids inside the bag to one side. Using a pair of scissors, make a cut lengthwise 

along the opposite side. Cutting the chip will compromise its integrity; cutting the 

desiccant bag simply makes a mess.

2) Preparing the instrument. Using the dropdown menu, select the parameter to be 

tested (Free Chlorine, Total Chlorine, or Free and Total). Several fields need to be 

entered before or during the measurement.

a. Before the measurement

i. Operator

ii. Chip lot-this is found on the outside of the bag, and should start 

with either V2A or C2A 

iii. Chip number-this is found on the back of the chip and should have 

a letter (A-J) and a number (1-22).

iv. Test type- this is entered in the comment field, and should be the 

name of the test as indicated on the test plan spreadsheet (e.g. 

Matrix spike, 0.5ppm). 

b. During the measurement

i. Powder pillow reading. 

ii. It is critical that the powder pillow reading be entered in the EPA 

for PPA software for each chip before hitting “OK” to accept the 

reading for the chip.

3) Placing the chip in the slot. The instrument should read “Insert chip”. At the 

bottom of the instrument, find two parallel metal rods protruding from the box. 

The back of the chip (the side with the ridge and the chip number) will be placed 

against these rods. Push the chip up into the instrument until it fits snugly in the 

instrument-a soft click can be heard when it is properly seated. At the bottom of 

Page 22 of 34
the chip is an angle that should have its lowest end on the right side of the chip. 

Once the chip is inserted, click on the “OK” button. 

4) Presenting the sample to the chip. Once the chip is installed the instrument will 

read “present sample”. At this time the sample (prepared just previously) should 

be placed in a small cup. The cup (with sample) is lifted to cover the entirety of 

the angled portion of the bottom of the chip. 

5) Removing the sample from the chip. When the instrument has drawn the sample, 

it will read “remove sample” and the cup should be withdrawn immediately. The 

instrument will not begin reading until the sample has been removed. At this point 

the sample should be transferred to a vial. The appropriate powder pillow is added 

and a measurement taken on the pocket colorimeter for comparison. 

After the breadboard reading is complete, a message saying “enter comment and remove 

chip” will appear.

6) Reading the output. The concentration will appear in large numbers. This should 

be recorded in the excel spreadsheet, along with the associated powder pillow 

value for that test.

7) Removing the chip. Pull down on the chip and it will dislodge. Be sure to pull 

straight down. Once the chip is out, place it in the used chips bag to be returned to 

Hach. 

8) Wipe the metal rods dry with a clean laboratory paper towel, such as a Kimwipe.

Powder Pillows:

 Hach method 8021 consists of foil pouches containing all the reagents for a given 

test, a cuvette, and a colorimeter. The procedure for using the powder pillows is 

straightforward.

 First obtain 10.0 mL of sample water and place it in the cuvette. Check the 

powder pillow to make sure it is the appropriate test (e.g. total chlorine or free chlorine), 

then hold the pouch by the top (crinkled edge) and flick it to make sure the contents are at 

the bottom of the pillow. Cut the top off the pillow close to the crinkled edge and push 

the two sides together to form a pouring spout (this is called pooching the pouch). Pour 

the contents into the cuvette, attach the cover to the cuvette and swirl vigorously for 

approximately 10 seconds, or until all the solid is dissolved. If a sonicator is available, a 

4-5 second sonication will remove bubbles and give more reliable readings. 

For the FREE CHLORINE test, wipe the vial with a clean towel/Kimwipe and 

measure the color in the colorimeter between 30 and 60 seconds after the pillow contents 

have been added. 

For the TOTAL CHLORINE test, wipe the vial with a clean towel/Kimwipe, and 

take a measurement 3 minutes after the pillow contents have been added. 

Be sure that the reading has stabilized by taking three measurements. If the 

reading doesn’t change, write the reading in the notebook. If the reading changes, 

continue to read until three identical readings are obtained. 

Page 23 of 34
Detailed Testing Schedule (Provided 

to the Laboratories)

Monday PM: Begin “Free Chlorine” testing

A. Low ionic strength standards, high and low spike: 

1. Obtain ~500 mL distilled or deionized water (DI water). 

2. Prepare two instruments. Instructions can be found in the document “Testing 

Procedure for Hach chips”.

a. The basic installation of the instrument will be performed by the Hach 

representative. 

b. Sample to sample preparation of the instrument involves inserting a 

new chip and entering data in the required fields: operator, chip lot 

number, chip ID, and test type (e.g. Low ionic, 1.9ppm).

c. In the dropdown menu of Test Types in the upper left of the screen 

(Free, Total, or Free + Total), select “Free”.

d. One breadboard should be marked C2A and the other V2A. Chips with 

the formulation C2A will be run exclusively on the C2A breadboard, 

and V2A chips on the V2A breadboard. 

i. Chip formulations are marked on the white label on the outside 

of the chip bag. 

ii. Note that in the Excel spreadsheet there are separate entries for 

C2A and V2A chips. 

3. Calculate the needed volume of high concentration (60-75 ppm) Cl2 (in 

ampoules provided by Hach) using the equation: 

M1V1 = M2V2 

V1 = M2V2 / M1

V1 = (0.2 mg/L)(10 mL) / (65 mg/L) = 0.031 mL = spiking volume (typically the 

practical value of the needed volume is 38-40 uL) 

V1 = (1.9 mg/L)(10 mL) / (65 mg/L) = 0.292 mL = spiking volume (typically the 

practical value of the needed volume is ~340-350 uL)

4. Check the validity of the calculation by spiking the calculated volume into 

10.0 mL DI water, then performing a powder pillow test. Adjust the spike 

volume according to the results of the powder pillow test. 

5. Repeat step 4 until the desired spike concentration is attained (0.2 mg/L or 

1.9 mg/L)(concentrations should be ±10% of target value; record exact 

concentrations measured). 

Page 24 of 34
6. Pipette 10.0 mL of DI water into the cuvette. Spike with the volume of 

concentrated Cl2 determined in Step 4. Cap and shake vigorously for 3 

seconds. 

7. Pour the contents into a plastic sample cup. 

8. Present the sample to the instruments (C2A and V2A) while the instruments 

are reading “present sample”. This is done by lifting the sample cup from 

underneath the chip until the instrument beeps and reads “remove sample”. 

Repeat the sample presentation on the second breadboard. 

9. Pour the contents of the sample from the cup back into the cuvette. 

10. Add the appropriate powder pillow (Free chlorine), cap and shake for 5 

seconds. 

11. If a sonication bath is available, immerse the cuvette into the bath deep 

enough to cover the sample but not the cover. 

12. Wipe the cuvette clean with a laboratory towel (e.g. Kimwipe).

13. Read the concentration using the pocket colorimeter; the reading must be 

taken within 60 seconds (preferably 30 seconds) of addition of the powder to 

the sample. Record the value in both the Excel spreadsheet and the 

instrument (in the box marked “powder pillow value”) 

14. Wash the cuvette 3x with DI water.

15. When the instrument reads “enter comment and remove chip” pull the chip 

out by pulling straight down on the end of the chip. 

16. Wipe the metal posts dry with a paper towel (i.e. Kimwipe).

17. Repeat this process to acquire seven 0.2 mg/L data points and seven 1.9 

mg/L data points using DI water as the matrix.

18. If the instrument reads “Bad Chip”, repeat the experiment with a new chip. 

Chips marked “bad chip” do NOT count toward the data point total.

B. Ground water matrix (procedure will be repeated for surface water matrix)

1. Obtain a 1000-1500 mL sample of ground water. 

2. Prepare the instrument as previously. 

3. Measure 10.0 mL of ground water into a plastic sample cup. 

4. Follow steps 8-18 above.

5. Acquire four data points by repeating the above procedure. 

6. When complete cover the water sample with Parafilm for use Tuesday AM for 

matrix spiking.

C. Prepare high ionic strength water for Tuesday.

1. To a 1 L volumetric flask add 1.40 g of NaHCO3, 1.48 g Na2SO4, and 1.54 g NaCl. 

Dilute to volume with deionized water. Prepare 4L of high ionic strength water. 

D. At the end of Monday there should be 18 entries in the Excel spreadsheet.

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Tuesday AM:

A. High ionic strength standards, high and low spike: 

1. Obtain ~500 mL high ionic strength water. 

2. Prepare two instruments: 

a. Sample to sample preparation of the instrument involves inserting a new 

chip and entering the required fields: operator, chip lot, chip ID, and test 

type.

3. Calculate the needed volume of high concentration (60-75 ppm) Cl2 (in 

ampoules provided by Hach using the equation: 

M1V1 = M2V2 

V1 = M2V2 / M1

V1 = (0.2 mg/L)(10 mL) / (65 mg/L) = 0.031 mL = spiking volume (typically 

the practical value of the needed volume is 38-40 uL)

V1 = (1.9 mg/L)(10 mL) / (65 mg/L) = 0.292 mL = spiking volume (typically 

the practical value of the needed volume is ~340-350 uL) 

4. Check the validity of the calculation by spiking the calculated volume into 

10.0 mL high ionic strength water, then performing a powder pillow test. 

Adjust the spike volume according to the results of the powder pillow test. 

5. Repeat step 4 until the desired spike concentration is attained (0.2 mg/L or 1.9 

mg/L) (concentrations should be ±10% of target value; record exact 

concentrations measured). 

6. Pipette 10.0 mL of high ionic strength water into the cuvette. Spike with the 

volume of concentrated Cl2 determined in Step 4. Cap and shake vigorously 

for 3 seconds. 

7. Pour the contents into a plastic sample cup. 

8. Present the sample to the instruments (C2A and V2A) while the instruments 

are reading “present sample”. This is done by lifting the sample cup from 

underneath the chip until the instrument beeps and reads “remove sample”. 

9. Pour the contents of the sample from the cup back into the cuvette. 

10. Add the appropriate powder pillow (Free chlorine), cap and shake for 5 

seconds. 

11. If a sonication bath is available, immerse the cuvette into the bath deep 

enough to cover the sample but not the cover. 

12. Wipe the cuvette clean with a laboratory towel (e.g. Kimwipe).

13. Read the concentration using the pocket colorimeter; the reading must be 

taken within 60 seconds (preferably 30 seconds) of addition of the powder to 

the sample. Record the value in both the Excel spreadsheet and the instrument 

(in the box marked “powder pillow value”) 

14. Wash the cuvette 3x with DI water.

Page 26 of 34
15. When the instrument reads “enter comment and remove chip” pull the chip 

out by pulling straight down on the end of the chip. 

16. Wipe the metal posts dry with a paper towel (i.e. Kimwipe).

17. Repeat this process to acquire seven 0.2 mg/L data points and seven 1.9 mg/L 

data points using high ionic strength water as the matrix.

18. If the instrument reads “Bad Chip”, repeat the experiment with a new chip. 

Chips marked “bad chip” do NOT count toward the data point total. 

B. Ground water 1.9 mg/L spike 

1. Repeat the above procedure substituting ground water for high ionic strength 

water.

Tuesday PM:

A. Ground water pH study 

1. Obtain 1500 mL of ground water (the sample used earlier can be reused). 

2. Measure the pH.

3. Determine if the pH is closer to 6.0 or 8.8. 

a. If the pH is closer to 6.0, adjust the full 1500 mL to pH 6.0 using the 

0.1 M HCl. Be sure to have active stirring during the pH adjustment. 

b. If the pH is closer to 8.8, adjust the full 1500 mL to pH 8.8 using the 

0.1 M NaOH. Be sure to have active stirring during the pH adjustment. 

4. Once the pH has been adjusted withdraw a 10.0 mL sample and place it in the 

cuvette.

5. Spike the sample with concentrated Cl2 (as done previously) to 1.9 mg/L. 

Cover the cuvette and shake the sample.

6. Pour the sample into the plastic sample cup.

7. Present the sample to each breadboard. 

8. Replace the sample into the cuvette, add a Free chlorine powder pillow, and 

read the concentration using the pocket colorimeter. 

9. Rinse the cuvette 3x with DI water.

10. Record the powder pillow data in the instrument and in the Excel spreadsheet 

(along with the breadboard data). 

11. Collect 4 data points at the pH 6.0/8.8 point by repeating steps 5 through 11. 

12. Adjust the pH to the next closest target pH on the Excel spreadsheet. 

a. If the solution pH is at 6.0, add 0.1 M NaOH to raise the pH to 7.4. 

b. If the solution pH is at 8.8, add 0.1 M HCl to lower the pH to 8.2. 

13. Repeat steps 5-11 to acquire four data points at the new pH. 

14. Continue to adjust the pH until all four pH’s (6.0, 7.4, 8.2, and 8.8) have four 

data points read. 

B. Surface water matrix

Page 27 of 34
1. Follow the same procedure as for ground water (Monday PM, part B). 

2. Allow the tap to run for at least 5 minutes before starting to fill the sample 

container.

3. Acquire four data points for the surface water matrix.

Wednesday AM:

A. Surface water spike

1. Obtain 1500 mL of fresh surface tap water, being sure to run the tap for 5 

minutes before collecting the sample.

2. Spike with concentrated Cl2 (as done earlier) to a concentration of 1.9 mg/L. 

Be sure to account for the Cl2 concentration found in the tap water. 

a. For example, Loveland, CO tap water has 0.4 mg/L Cl2. Thus, to reach 

1.9 mg/L requires only a 1.5 mg/L spike. 

3. Obtain breadboard and powder pillow readings as done earlier: spike the 

sample, transfer to the sample cup, present to breadboard C2A, present to 

breadboard V2A, run powder pillow test, record data on breadboard and 

spreadsheet.

B. Surface water pH study.

1. Follow the procedure for the ground water pH study, substituting surface (tap) 

water for the ground water. As with the spike above, the starting Cl2

concentration will need accounting. 

2. Four data points will need to be acquired for each of the 4 pH solutions (6.0, 

7.4, 8.2, and 8.8). 

At the completion of the surface water pH study, the entire “Free Chlorine” sheet in the 

Excel spreadsheet should be completed.

Wednesday PM: Begin “Total Chlorine” testing 

A. Low ionic strength standards, high and low spike: 

1. Prepare a high concentration monochloramine standard. 

a. Gather a 1000 mL beaker, 1.0 mL bleach, 60 mg NH4Cl,and 0.141 mL 

0.1M NaOH .

b. Fill the beaker to the 1000 mL mark with DI H2O.

c. Add the NH4Cl and stir 2 minutes after all solid has dissolved.

d. Add the NaOH.

e. Add 1.0 mL of bleach over 5 minutes, with vigorous stirring. 

f. Allow the solution to stir for 30 minutes. 

g. This solution will have a concentration of ~50 mg/L. The exact 

concentration will vary slightly depending on the exact concentration 

of the bleach.

2. Obtain ~500 mL distilled or deionized water (DI water).

3. Prepare two instruments. Instructions can be found in the document “Testing 

Procedure for Hach chips”. As a review, 

Page 28 of 34
a. In the dropdown menu of Test Types in the upper left of the screen 

(Free, Total, or Free + Total), select “Total”.

b. Sample to sample preparation of the instrument involves inserting a 

new chip and entering data in the required fields: operator, chip lot 

number, chip ID, and test type (e.g. Low ionic, 1.9ppm). 

c. One breadboard should be marked C2A and the other V2A. Chips with 

the formulation C2A will be run exclusively on the C2A breadboard, 

and V2A chips on the V2A breadboard. 

ii. Chip formulations are marked on the white label on the outside 

of the chip bag. 

iii. Note that in the Excel spreadsheet there are separate entries for 

C2A and V2A chips. 

4. Calculate the needed volume of high concentration monochloramine standard 

made in step 1. The concentration of the standard will be approximately 50 mg/L. 

M1V1 = M2V2 

V1 = M2V2 / M1

V1 = (0.2 mg/L)(10 mL) / (50 mg/L) = 0.040 mL = spiking volume 

V1 = (1.9 mg/L)(10 mL) / (50 mg/L) = 0.380 mL = spiking volume 

5. Check the validity of the calculation by spiking the calculated volume into 10.0 

mL DI water, then performing a powder pillow test with a Total chlorine powder 

pillow (note that the Total powder pillow requires 3 minutes wait before 

measuring). Adjust the spike volume according to the results of the powder pillow 

test.

6. Repeat step 5 until the desired spike concentration is attained (0.2 mg/L or 1.9 

mg/L) (concentrations should be ±10% of target value; record exact 

concentrations measured). 

7. Pipette 10.0 mL of DI water into the cuvette. Spike with the volume of 

concentration monochloramine determined in Step 4. Cap and shake vigorously 

for 3 seconds. 

8. Pour the contents into a plastic sample cup.

9. Present the sample to the instruments (C2A and V2A) while the instrument is 

reading “present sample”. This is done by lifting the sample cup from underneath 

the chip until the instrument beeps and reads “remove sample”. Repeat the sample 

presentation on the second breadboard. 

10. Pour the contents of the sample from the cup back into the cuvette. 

11. Add the appropriate powder pillow (Total chlorine), cap and shake for 5 seconds. 

12. If a sonication bath is available, immerse the cuvette into the bath deep enough to 

cover the sample but not the cover. 

13. Wipe the cuvette clean with a laboratory towel (e.g. Kimwipe).

Page 29 of 34
14. Read the concentration using the pocket colorimeter; the reading must be taken 3 

minutes after addition of the powder to the sample. Record the value in both the 

Excel spreadsheet and the instrument (in the box marked “powder pillow value”) 

15. Wash the cuvette 3x with DI water.

16. When the instrument reads “enter comment and remove chip” pull the chip out by 

pulling straight down on the end of the chip. 

17. Wipe the metal posts dry with a paper towel (i.e. Kimwipe).

18. Repeat this process to acquire seven 0.2 mg/L data points and seven 1.9 mg/L 

data points using DI water as the matrix.

19. If the instrument reads “Bad Chip”, repeat the experiment with a new chip. Chips 

marked “bad chip” do NOT count toward the data point total. 

E. Ground water matrix (procedure will be repeated for surface water matrix)

1. Obtain a 1000-1500 mL sample of ground water. 

2. Prepare the instruments as previously. 

3. Measure 10.0 mL of ground water into a plastic sample cup.

4. Follow steps 7-18 above. 

5. Acquire four data points by repeating the above procedure. 

6. When complete cover the water sample with Parafilm for use Thursday AM 

for matrix spiking.

F. At the end of Wednesday there should be 18 entries in the Excel “Total” 

spreadsheet, and the “Free” spreadsheet should be completed.

Thursday AM:

High ionic strength water, low and high spikes: 

1. Obtain ~500 mL high ionic strength water. 

2. Prepare two instruments: 

b. Sample to sample preparation of the instrument involves inserting a new 

chip and entering the required fields: operator, chip lot, chip ID, and test 

type.

3. Calculate the needed volume of high concentration monochloramine standard 

(prepared Wednesday afternoon, approx. 50 mg/mL) using the equation: 

M1V1 = M2V2 

V1 = M2V2 / M1

V1 = (0.2 mg/L)(10 mL) / (50 mg/L) = 0.040 mL = spiking volume 

V1 = (1.9 mg/L)(10 mL) / (50 mg/L) = 0.380 mL = spiking volume 

4. Check the validity of the calculation by spiking the calculated volume into 

10.0 mL high ionic strength water, then performing a powder pillow test. 

Adjust the spike volume according to the results of the powder pillow test. 

Page 30 of 34
5. Repeat step 4 until the desired spike concentration is attained (0.2 mg/L or 1.9 

mg/L) (concentrations should be ±10% of target value; record exact 

concentrations measured). 

6. Pipette 10.0 mL of high ionic strength water into the cuvette. Spike with the 

volume of monochloramine standard determined in Step 4. Cap and shake 

vigorously for 3 seconds. 

7. Pour the contents into a plastic sample cup.

8. Present the sample to the instruments (both C2A and V2A) while the 

instrument is reading “present sample”. This is done by lifting the sample cup 

from underneath the chip until the instrument beeps and reads “remove 

sample”.

9. Pour the contents of the sample from the cup back into the cuvette. 

10. Add the appropriate powder pillow (Total chlorine), cap and shake for 5 

seconds. 

11. If a sonication bath is available, immerse the cuvette into the bath deep 

enough to cover the sample but not the cover. 

12. Wipe the cuvette clean with a laboratory towel (e.g. Kimwipe).

13. Read the concentration using the pocket colorimeter; the reading must be 

taken 3 minutes after addition of the powder to the sample. Record the value 

in both the Excel spreadsheet and the instrument (in the box marked “powder 

pillow value”) 

14. Wash the cuvette 3x with DI water.

15. When the instrument reads “enter comment and remove chip” pull the chip 

out by pulling straight down on the end of the chip. 

16. Wipe the metal posts dry with a paper towel (i.e. Kimwipe).

17. Repeat this process to acquire seven 0.2 mg/L data points and seven 1.9 mg/L 

data points using high ionic strength water as the matrix.

18. If the instrument reads “Bad Chip”, repeat the experiment with a new chip. 

Chips marked “bad chip” do NOT count toward the data point total.

C. Ground water 1.9 mg/L spike 

1. Repeat the above procedure substituting ground water for high ionic strength 

water.

2. Acquire four data points, using a fresh spiked sample for each reading. 

Thursday PM:

A. Ground water pH study 

1. Obtain 1500mL of ground water (the sample used earlier can be reused). 

2. Measure the pH.

3. Determine if the pH is closer to 6.0 or 8.8. 

Page 31 of 34
d. If the pH is closer to 6.0, adjust the full 1500 mL to pH 6.0 using the 

0.1 M HCl. Be sure to have active stirring during the pH adjustment.

e. If the pH is closer to 8.8, adjust the full 1500 mL to pH 8.8 using the 

0.1 M NaOH. Be sure to have active stirring during the pH adjustment. 

4. Once the pH has been adjusted withdraw a 10.0 mL sample and place it in the 

cuvette.

5. Spike the sample with monochloramine (as done previously) to 1.9 mg/L. 

Cover the cuvette and shake the sample.

6. Pour the sample into the plastic sample cup. 

7. Obtain breadboard and powder pillow readings as done earlier: spike the 

sample, transfer to the sample cup, present to breadboard C2A, present to 

breadboard V2A, run powder pillow test, record data on breadboard and 

spreadsheet.

8. Replace the sample into the cuvette, add a Total chlorine powder pillow, and 

read the concentration using the pocket colorimeter. 

9. Rinse the cuvette 3x with DI water.

10. Record the powder pillow data in the instrument and in the Excel spreadsheet 

(along with the breadboard data). 

11. Collect 4 data points at the pH 6.0/8.8 point by repeating steps 4 through 11. 

12. Adjust the pH to the next closest target pH on the Excel spreadsheet.

a. If the solution pH is at 6.0, add 0.1 M NaOH to raise the pH to 7.4. 

b. If the solution pH is at 8.8, add 0.1 M HCl to lower the pH to 8.2. 

13. Repeat steps 4-11 to acquire four data points at the new pH. 

14. Continue to adjust the pH until all four pH’s (6.0, 7.4, 8.2, and 8.8) have four 

data points read. 

Surface water matrix

1. Follow the same procedure as for ground water (Monday PM, part B), 

substituting the monochloramine standard for the concentrated chlorine. 

2. Allow the tap to run for at least 5 minutes before starting to fill the sample 

container.

3. Acquire four data points for the surface water matrix.

Page 32 of 34
Friday AM:

A. Surface water spike

1. Obtain 1500 mL of fresh surface tap water, being sure to run the tap for 5 

minutes before collecting the sample.

2. Spike with monochloramine standard (as done earlier) to a concentration of 

1.9 mg/L (concentrations should be ±10% of target value; record exact 

concentrations measured). Be sure to account for the Cl2 concentration found 

in the tap water. For example, Loveland, CO tap water has 0.4 mg/L Cl2. 

Thus, to reach 1.9 mg/L requires only a 1.5 mg/L spike. 

3. Obtain breadboard and powder pillow readings as done earlier: spike the 

sample, transfer to the sample cup, present to breadboard C2A, present to 

breadboard V2A, run powder pillow test, record data on breadboard and 

spreadsheet.

4. Surface water pH study.

5. Follow the procedure for the ground water pH study, substituting surface (tap) 

water for the ground water. As with the spike above, the starting Cl2

concentration will need accounting. 

6. Four data points will need to be acquired for each of the 4 pH solutions (6.0, 

7.4, 8.2, and 8.8). 

B. Monochloramine interference:

1. In the dropdown menu of Test Types in the upper left of the screen (Free, 

Total, or Free + Total), select “Free + Total”.

2. To a 10.0 mL sample of DI water, add enough monochloramine standard to 

reach a concentration of 1.9 mg/mL (concentrations should be ±10% of target 

value; record exact concentrations measured).

3. Present the sample and acquire four data points as done earlier. 

At the completion of the surface water pH study, the entire “Free Chlorine” 

sheet in the Excel spreadsheet should be completed. 

Page 33 of 34
APPENDIX B.

SUPPORTING DATA

B.1 Raw Data

All raw data is attached in the 3 files (Loveland data.xlsx, Phoenix data.xlsx, and Cedar 

Falls data.xlsx). Within each file the raw data from the instrument can be found. 

B.2 Example Calculations

Sample concentrations were determined by the PRFC system and by the pocket 

colorimeters. There was no need to calculate the concentrations of the samples. 

B.3 Waveforms for a typical set of total chlorine data at 2.0 mg/L 

Page 34 of 34