# Chlorine Dioxide and Chlorite in

Drink ing Water by Amperometry using Disposable Sensor s

November 2013

PALINTEST LTD 1455 Jamike Avenue (Suite 100) Erlanger Kentucky 41018 (859) 341 7423________________________________________________________________

ii 

## Acknowledgements

This method was prepared by Stephen W Birch of Palintest Ltd.

The method was developed by S. W. Bir ch & S.R. Johnston of Palintest Ltd.



## Disclaimer

The mention of trade names or commercial products does not constitute

an endorsement or recommendation for use.________________________________________________________________

iii 

## Introduction

The electrochemical sensor method was developed by Palintest Ltd to provide a simple and rapid analysis of drinking water for chlorine dioxide and chlorite r emoving almost all sources of technique dependence.

This method is applicable to the determination of chlorine dioxide and chlorite. Water samples are analyzed by amperometry using pre

- calibrated disposable sensors. Chlorite determination requires the a d dition of reagents to the sample.

Copies of the method can be obtained from, 

### or questions concerning this method or its application should be addressed to:

Palintest Ltd 1455 Jamike Avenue (Suite 100) Erlanger Kentucky 41018 (859) 341 7423________________________________________________________________

1 

## Method

A Method for the Determination of Chlorine dioxide and Chlorite in Drinking Water by Amperometry using disposable sensor s

1.0 Scope and Application

This method is for the determination of chlorine dioxide and chlorite i n drinking water.

1.1 The method detection limit (MDL), minimum level (ML) and application range for each analyte is shown below. The MDL was calculated from analysis of

se ven aliquots of analyte free water fortified to 0.1mg analyte/L.

Analyte MDL (mg/L) ML (mg/L) Application Range (mg/L)

Chlorine dioxide 0.02 0.05 0.02

- 50

Chlorite 0.02 0.05 0.02

- 50

1.2 The laboratory is not allowed to omit any quality control analyses. Each operator that uses this method must demonstrate the ability to generate acceptable results using the procedure in Section 9.2.

1.3 Chlorine dioxide is a volatile, reactive gas. Care was taken during method development to minimize steps that could result in the loss of chlorine dioxide during analysis. Analyst technique can affect the method precision and

accuracy

.



### 2.0 Summary of Method

2.1 This is an extension of the ChloroSense  method (see Reference 16.1 ). It

utilises a di s posable sensor s , the ChlordioX  Plus sensor. Chlorine dioxide present in the sample can be reduced directly at the surface of the

ChlordioX  Plus sensor. The current that flows is directly proportional to the amount of chlorine dioxide in the sample. To determine chlorite

, any chlorine dioxide in the sample must be removed. This is done by degassing the sample using a degassing unit and portable air pump. Chlorite is determined by first adding potassium iodide (KI) to the sample at a pH where the chlorite does not react but any free or total chlorine in the sample does react to

liberate iodine. The amount of iodine released is reduced at the surface of

the ChlordioX  Plus sensor . The current that flows is directly proportional to the amount of free and total chlorine in the sample (Reading A). The sample is then acidified by the addition of dilute hydrochloric acid. The iodide then

reacts with chlorite and free and combined chlorine to release iodine. The

amount of iodine released is reduced at the surface of the ChlordioX  Plus sensor. The current that flows is directly proportional to the amount of

chlorite and free & combined chlorine in the sample (R eading B). The

amount of chlorite can then be calculated by subtracting Reading A from Reading B. The current is converted to mg analyte/L by reference to calibration parameters stored in the instrument software. The appropriate calibration parameters are transferred from a calibration chip that is provided with each batch of sensors. Quality is assured through calibration and verification with externally referenced standard solutions.________________________________________________________________

2 2.2 Chlorine dioxide : The test container is filled with a sample of water, approximately 5 0mL. 6 drops of glycine solution are added and gently stirred.
A disposable ChlordioX  Plus sensor is inserted in to the instrument and the lid is closed to begin the test. After completion of the test, the value for

chlorine dioxide is read from the instrument display.

2.3 Sample Degassing: The degasser unit is filled with a second sample of water (50m L ). Air is passed through the water sample using a portable air pump to remove the chlorine dioxide from the sample. The degassing time is determined by the amount of chlorine dioxide found to be in the sample in

section 2.2 and is timed by the instrument

.

2. 4 Chlorite: The test container is filled with the degassed sample. P otassium

iodide solution is added from a dropper bottle ( 6 drops) to the degassed
sample

. A disposable ChlordioX  Plus sensor is inserted in to the instrument and the lid is closed to begin the test. The sensor is then discarded and an acidification solution (2.9M HCl) is added to the sample. The instrument lid is

closed and a timer is started. After a 2 minute reaction period

, a new disposable ChlordioX  Plus sensor is inserted in to the instrument and the lid is closed to begin the test. After completion of the test, the value for chlorite is read from the instrument display.

The manufacturer’s instructions should be followed regarding the use and

care of the instrument.



### 3.0 Definitions

The definitions and purposes below are specific to this method, but have been conformed to common usage as much as possible.

3.1 Calibration Check (CC) : A calibration standard containing the method analyte that is analyzed periodically to verify the accuracy of the existing calibration.

3.2 Initial demonstration of capability (IDC) : Four aliquots of the diluted Quality Control Standard (QCS) are a nalyzed to establish the ability to generate acceptable precision and accuracy. An IDC is performed the first time this method is used by each operator.

3.3 Laboratory reagent blank (LRB) : An aliquot of reagent water or other blank matrix that is treated as a sample including exposure to all glassware, equipment, solvents, and reagents that are used with the samples. The LRB is used to determine if method analytes or other interferences are present in the laboratory environment, the reagents or the ap paratus.

3.4 Linear calibration range (LCR) : The concentration range over which the instrument response is linear.

3.5 Laboratory Fortified Matrix S pike (LFMS) a nd Laboratory Fortified Matrix Spike

D uplicate (LFMSD) : Aliquots of an environmental sample to which known quantities of the analytes are added in the laboratory. The LFMS and LFMSD are prepared and/or analyzed exactly like a field sample. Their purpose is to quantify any additional bias and imprecision caused by the sample matrix. The background concentration of the analyte in the sample matrix must be determined in a separate aliquot and the measured values in the LFMS and LFMSD are corrected for background concentrations.________________________________________________________________

3 3.6 Material Safety Data S heet (MSDS) : Written information p rovided for the chemical reagents concerning a chemical’s toxicity health hazards, physical properties, fire, and reactivity data including storage, spill and handling precautions.

3.7 Minimum Reporting Level (MRL) : The lowest level at which the entire analytical system gives a reproducible signal that meets the method quality objectives. It is never lower than the concentration of the lowest calibration check (CC) standard.

3.8 Q uality Control S ample (QCS) : A solution of method analyte of known concentration. The QCS is obtained from a source external to the laboratory or is prepared from standards obtained from a different source than the calibration standards. The purpose is to check laboratory performance using test materials that have been prepared independently from the normal calibration

process.

3.9 R eagent water : Water demonstrated to be free from the method analyte and interfering substances.



### 4.0 Interferences

4.1 Other disinfectant residuals such as bromine, iodine, ozone and peroxide may react with or KI or directly with the electrode surface and cause a positive interference.

4.2 The chlorite test gives a small positive intercept (equivalent to 0.16mg/l chlorite) i n the presence of Fe 3+ (5 mg/L) . Fe 3+ strongly catalyses the decomposition of chlorite. In the presence of Fe 2+ chlorite is reduced to

chloride.

4.3 No interferences have been encountered with the chemical species found naturally in drinking water or added as treatment chemicals. The method is without interference in the presence of 0.5 mg/L aluminium, 5 mg/L zinc, 10 mg/l sodium tripoly

- phosphate, 800 mg/L chloride, 4 mg/L fluoride, 4 mg/L phosphate, 500 mg/L sulfate, 300 mg/L CaCO 3 alkalinity, 350 mg/L calcium hardness, 300 mg/L magnes ium hardness or 1000mg/L total dissolved

solids

.



### 5.0 Safety

5.1 Use good laboratory practice throughout the test procedure. Follow the test instructions carefully.

5.2 When working with chlorine dioxide standards it is necessary to use a fume

hood.

5.3 This method does not address all safety issues associated with its use. The laboratory is responsible for maintaining a safe working environment and a current awareness file of OSHA regulations regarding the safe handling of the

chemical s specified in this method. A reference file of material safety data sheets (MSDS) should be available to all personnel involved in these________________________________________________________________

4 analyses. Additional information on laboratory safety can be found in

References 16.2 to 16.4

.

NOTE: Do not allow a water sample to remain in the instrument following analysis.



### 6.0 Equipment and Supplies

_________________________________________________________________________ Note: Brand names, suppliers and part numbers are for illustrative purposes only. No

endorsement is implied.

_________________________________________________________________________

6.1 Sampling equipment:

6.1.1 Sample collection bottles - amber glass bottles with PTFE

- lined screw caps or opaque, high

- density polyethylene (HDPE) bottles

.

6.1.2 Palintest ChlordioX  Plus potentiostat dedicated to the analysis of

chlorine dioxide and chlorite in drinking water. If measuring chlorine dioxide only, then the Palintest ChlordioXense  potentiostat can also be used.

6.1.3 Laboratory glassware and plastic ware required : includes sample containers, volumetric flasks, pipettes, sample storage vials, conical beakers (250 mL).

6.1.4 Sample degassing unit and portable air pump, Palintest number PT 553

and PT 554 or equivalent.



### 7.0 Reagents and Standards

7.1 D ISPOSABLE SENSORS
– Palintest ChlordioX  Plus sensors (catalogue

number CDX310 or CDX 350) are for the determination of chlorine dioxide and chlorite in drinking water. Disposable sensors have a shelf life of 24 months.

7.2 GLYCINE REAGENT
– Palintest n umber PT 549

7.3 POTASSIUM IODIDE SOLUTION
– Palintest number PT 546

7.4 ACIDIFICATION SOLUTION
– Palintest number PT 547



### 7. 5 REAGENT WATER
– Purified water (typically either deionized or distilled) is acceptable. Reagent water can be purchased from a scientific supply company, if it is not available on site. If a chlorine dioxide/chlorine demand is
present, suggested procedures for preparing chlorine demand

- free water are

included in ASTM D 1253

- 03 ( Reference 16.5 ) and Standard Method 4500

- Cl

C ( Reference 16.6 ).

7. 6 CALIBRATION STANDARD SOLUTIONS

7.6 .1 C HLORINE DIOXIDE STOCK SOLUTION (CDSS) – C hlorine dioxide solutions are unstable and must be prepared just prior to use. Chlorine dioxide solution can be prepared following the method described in Standard Methods ( Reference 16.7 )

. Chlorine dioxide solution should be stored in a glass

- stop p ered dark

- colored bottle in a refrigerator. Chlorine dioxide________________________________________________________________

5 solution should be standardized by titration with sodium thiosulphate in the presence of potassium iodide, acid and starch indicator ( Reference 16.7 )

.

Alternately, a rapid standard generation kit for chlorine dioxide is available

from Palintest

, number PT544, which produces approximately 95 mg/L. The actual Chlorine Dioxide concentration can be determined by measuring the absorbance at 360nm in a spectrophotometer using a cell with a 1cm light path. The concentration is given by Abs 360nm *54 (assuming a molar extinction coefficient of 1250). Transfer to an amber bottle with PTFE lined cap or

HDPE container. This solution should be stored at ≤ 6 o C.

7.6.1.1 C HLORINE DIOXIDE PRIMARY DILUTION STANDARD (CDPDS) (9.5mg/L) - This solution is used to prepare Calibration Standards and Continuing Calibration Check standards. It assumes that the CDSS is 95mg/L. Partially fill a 100mL volumetric flask with reagent water. Add 10

mL of the chlorine dioxide stock standard solution ( section 7.6.1) using a pipette and fill to the mark using reagent water. Invert the flask several times to ensure it is properly mixed and then transfer to an amber bottle with PTFE lined cap or HDPE container. This solution should be prepared when required

and stored at ≤ 6 o C . The actual concentration will depend on the spectrophotometer measurement in 7.6.1.

7.6.1. 2 C ALIBRATION ST AN DARDS
– 5 calibration standards are recommended that span the anticipated reporting range

. All Calibration

Standards are to be prepared using Class A volumetric or variable

- volume pipettes and volumetric flasks. An example of the dilutions that were used to

prepare the standards used in the development of this method is included in

the table below. Transfer an aliquot of the appropriate Chlor ine D ioxide

standard to a flask and dilute to the mark with reagent water. Mix the contents

of the fl ask by inverting 3 to 4 times and transfer to an amber glass bottle or opaque plastic container. These solutions should be used immediately

Chlorine Dioxide

Volume (mL) Standard used ( CD PDS or

C D SS) Final volume (mL) Calibration Std. Conc. (mg/L)

2 CD PDS 1 00 0.19

10 CD PDS 1 00 0.95

5 C D SS 1 00 4.75

10 C D SS 1 00 9.5

50 C D SS 1 00 47.5

7.6 .2 C HLORITE STOCK STANDARD SOLUTION (S SS ) ( 1000mg/L ) – Certified chlorite standards are commercially available (e.g. Absolute Standards, cat .# 54109 or equivalent). Commercial standards should be

stored at ≤6 o C in an amber bottle with a PTFE

- lined cap or an HDPE

container.

7.6. 2 .1 CHLORITE PRIMARY DILUTION STANDARD (PDS) (1 0mg/ L) - This solution is used to prepare Calibration Standards and Continuing C alibrat ion Check standards. Partially fill a 500m L volumetric flask with reagent water.

Add 5mL of the chlorite stock standard solution using a pipette and fill to the mark using reagent water. Invert the flask several times to ensure it is properly mixed and then transfer to an amber bottle with PTFE lined cap or

HDPE container. This solution should be stored at ≤ 6 o C. If stored correctly

this solution should be stable for 3months.________________________________________________________________

6 7.6. 2 .2 C ALIBRATION STANDARDS
– It is recommended that 5 calibration

standards are used to establish an initial calibration curve. The concentration of the standards must span the intended reporting range. All Calibration

Standards are to be prepared using Class A volumetric or varia ble

- volume pipettes and volumetric flasks

. An example of the dilutions that were used to

prepare the standards used in the development of this method is included in

the table below. Transfer an aliquot of the appropriate Chlorite solution to a

flask and dilute to the mark with reagent water. Mix the contents of the flask by inverting 8 to 10 times and transfer to an amber glass bottle or opaque plastic container. These solutions should be stored at ≤ 6 °C. If stored properly, these solutions should be stable for 3 months.

Chlorite Volume (mL) Standard used (PDS or S SS) Final volume (mL) Calibration Std. Conc. (mg/L)

10 PDS 500 0.2

50 PDS 500 1.0

2.5 S SS 500 5

5 S SS 500 10

25 S SS 500 50

7. 7 ROUTINE CALIBRATION CHECK STANDARD -- Calibration standards prepared above may also be used as calibration check standards. Calibration check standards must be freshly prepared as needed.

7.8 CONTINUING CALIBRATION CHECK (CCC) STANDARDS
– calibration standards produced above can also be used as CCC standards.



### 8.0 Sample Collection, Preservation and Storage

8.1 Collect samples in chlorine dioxide/chlorine demand free amber glass

containers or opaque, high

- density polyethylene (HDPE) bottles, filling the

container so there is no headspace. Avoid exposure to sunlight or agitation during sampling. Analyze immediately after sample collection as chlorine dioxide in aqueous solution is not stable.

9.0 

### Quality Control

9.1 Quality Control (QC) requirements include the Initial Demonstration of Capability and on

- going QC requirements that must be met when preparing and analyzing field samples. This section describes each QC parameter, its required frequency, and the performance criteria that must be met in order to meet EPA quality objectives. These QC requirements are considered the minimum acceptable QC criteria. Laboratories are encouraged to institute additional QC practices to meet their specific needs.

9.2 INITIAL DEMONSTRATION OF CAPABILITY (IDC)
– The IDC must be successfully performed prior to analyzing any field samples. Prior to conducting the IDC, the analyst must meet the calibration requirements outlined in Section 10. Requirements for the initial demonstration of

labo ratory capability are described in the following sections.________________________________________________________________

7 9.2.1 DEMONSTRATION OF LOW SYSTEM BACKGROUND
– Analyze a LRB after processing through all sample collection steps outlined in Section

8.1. The method blank concentration must be ≤ 1⁄3 the concen tration of the lowest standard used to prepare/verify the calibration curve.

9.2.2 INITIAL DEMONSTRATION OF ACCURACY
– Prepare and analyze a method blank (reagent water) and five independent reference samples at the same concentration. The concentration of the samples should be in the mid range of the calibration curve or near the expected concentration of the water samples. Complete for each of the analytes, chlorine dioxide and chlorite. Calculate the average concentration for the five analyses for each analyte

. The average concentration for the five replicates must be within ± 15% of the expected value for each analyte.

9.2.3 INITIAL DEMONSTRATION OF PRECISION
– Using the same set of replicate data generated for Section 9.2.2 calculate the standard deviation and relative standard deviation ( RSD ) of the replicate values. The RSD is calculated using the equation

where

S is the standard deviation for the replicate values,

and is the average value for the replicates.

The RSD of the results of the replicate analyses for each analyte must be

≤15%.

9.3 ONGOING QC REQUIREMENTS
– This section describes the ongoing QC criteria that must be followed when processing and analyzing field samples.

9.3.1 DEMONSTRATION OF LOW SYSTEM BACKGROUND
– Analyze a LRB with each analytical batch. The LRB should be processed through all sample collection steps outlined in Section 8.1. The method blank

concentration must be ≤ 1⁄3 the concentration of the lowest standard used to prepare/verify the calibration curve.

9.3.2 CONTINUING CALIBRATION CHECK
– Analyze a CCC standard for each analyte with each analytical batch. Prepare an aqueous calibration check standard at a concentration near the expected concentration of the water samples (as in Section 7 ). Over time, vary the calibration check

standard concentration. The measured concentration of the calibration check standard must be within ± 15% of the expected value. If this criterion is not met, then the analyst must identify and resolve the problem.

9.4 Laboratories/water systems are encouraged to institute additional QC practices to meet their specific needs. The remainder of this section describes various optional QC procedures that may be incorporated into a QC program for grab sample verification

.

9.4.1 SAMPLE DUPLICATE
– Analysis of duplicate samples (two samples collected at the same time) provides an estimate of the precision of the sample analyses. Calculate the relative percent difference (RPD) between the Sample (FD1) and the Sample Duplicate (FD2) as shown below. The RPD for samples with concentrations greater than the lowest calibration 

### RSD S

X % = × 100



### X________________________________________________________________

8 standard should not exceed 15%. The RPD at concentrations at or near the

lowest calibration standard should not exceed 50%.

If the RPD for the Sample and the Sample Duplicate falls outside the designated range, then perform duplicate analyses of a calibration check

standard to verify that the grab sample method is in control.

9.4.2 INDEPENDENT REFERENCE SAMPLE
– Analysis of a sample from an external source (different from the calibration standards) provides an independent check of the calibration of the method. It is recommended semiannually or any time a new calibration curve is validated. In cases where there may not be many external vendors, it is acceptable to evaluate a different lot of material from that used to prepare the CAL standards.

9.4.3 PROFICIENCY TESTING (PT) or PERFORMANCE EVALUATIO N (PE)

SAMPLE – Successful participation in a PT or PE Study is a good QC tool for demonstrating proficiency with the grab sample method. A certified solution

of chlorite whose concentration is unknown to the analyst can be purchased by the laboratory/water system. An aliquot of the certified solution is added to a known volume of reagent water and analyzed as a grab sample. The analytical results are reported to the PT/PE Study Provider where they are compared to data from all analyses of the sample. Acceptance criteria are established by the provider for each study. Because of the nature of chlorine dioxide it is not possible to obtain a certified solution.

10.0 Calibration and Standardization

10.1 Verify the initial calibration curve for each analyte

. This must be done for each

instrument according to the procedure described below. This must also be performed when a new calibration code or lot of disposable sensors is put into service. These steps can be performed by laboratory personnel or field samplers. A record of the calibration results must be maintained for each

instrument

.

10.1.1 Prepare a set of at least three aqueous calibration standards. The lowest concentration calibration standard must be at or below 0.2 mg/L. The

st andards must span the concentration range that is expected to be observed in the grab samples.

10.1.2 Analyze the calibration standards and method blank according to the grab sample procedure. (Note: If the highest concentration standard is above the maximum concentration specified for the instrument , dilute and analyze it according to manufacturer’s instructions. Use the data from this analysis to check the accuracy of the dilution process, not the calibration curve.)

10.1.3 To verify the factory set calibration curve, compare the measured concentration of each standard to the expected value. Each calibration point

must be within ± 15% of its expected value. If the internal curve does not meet these criteria, the internal curve must be updated by following the manufacturers’ instructions for generating or inputting a curve. Otherwise,

send the instrument to the manufacturer for repair/updating.________________________________________________________________

9 

### 11.0 PROCEDURE

11.1 Press and hold the power button until the title screen is displayed.

11.2 When the instrument passes all internal functional checks on start up, the screen displays the current batch code. To accept the batch code, press the right arrow key. To change the batch code, see section 11.3.

11.3 Ensure the calibration code shown on screen matches with the number on the foil of the batch of sensors in use. If it does not, press the left arrow key, the screen prompts to insert a calibration sensor ( section 11.3.1)

.

11.3.1 To enter the c alibration code , s lide the front catch to the right and op en the instrument case fully. Press the blue lever to open the jaw and

insert the ChlordioX  Plus calibration sensor, connecting tracks
uppermost, fully into the slot revealed. Release the blue lever. Close the instrument lid. The display indicates Reading Calibration. The calibration number will be displayed briefly and the display will then

return to the start screen. Check that the new code number displayed on screen matches the number on the sensor packaging. Open the case and remove the calibration chip. Press the right arrow key to accept the batch code. A test can now be performed.

11.4 To begin an analysis slide the front catch to the right, and open the instrument case fully.

11.5 Remove the sample container. Rinse and then fill one half

, to the stepped

line

, with the water sample.

11.6 Replace the filled sample container in the instrument with the filled half

towards the front.

11.7 Add 6 drops of glycine reagent (provided in the test kit) to the sample and stir gently for 5 se c onds with the rod provided.

11. 8 Holding the sensor through the foil pack t ear open the foil along the tear line to expose the connecting tracks.

11. 9 Press the blue lever to open the jaw of the sensor connector. Insert the exposed end of the sensor, connecting tracks uppermost, into the slot, and release the lever. The jaws will close to hold the sensor in place. Slide the foil pouch off to expose the sensor.

11.10 Gently close the instrument lid to immerse the sensor in the sample. The test starts automatically. The display indicates progress of the test. Do not disturb the instrument during the test.

11.11 In less than one minute the chlorine dioxide result will be displayed. All

res ults are automatically stored in the instrument log.

11.12 To carry out a chlori te test press the right arrow key. The instrument prompts the user to discard the sample and sensor. Close the instrument lid. The display will show the sample degassing time required based on the

chlorine dioxide result.________________________________________________________________

10 To measure chlorite

, the chlorine dioxide must be removed from the sample. This is achieved using a degassing unit and po r table air pump (Palintest no.

PT 553 & PT 554 )

11.13 Place a s econd

, identical sample in to the degasser cup. Attach the portable

air pump and switch on. Press the right arrow key on the instrument to start

the timer. At the end of the degassing period the instrument will display the sensor calibration code and prompt the user to insert the sample to carry out

a chlorine test. The performance of the chlorine test is not covered by the scope of this method. For analy sis of free chlorine see 16.1.

11.14 To skip the chlorine test and proceed to the chlorite test press the right arrow key.

11.15 Transfer the sample in the d egasser cup to the sample container and place in the instrument, with the filled half towards the front.

11.16 The instrument prompts the user to add chlorite reagent 1 and insert a

chlorite sensor.

A **chlorite sensor** is the same as a chlorine dioxide sensor. S ensors from

the same batch should be used for chlorine dioxide and chlorite

measurements

11.21 Chl orite reagent 1 is added using dropper bottles. Add 6 drops of reagent to the water sample in the sample container. Gently stir using the supplied plastic paddle to mix the reagents

.

11.22 Holding the sensor through the foil pack tear open the foil along the tear line to expose the connecting tracks.

11.23 Press the blue lever to open the jaw of the sensor connector. Insert the exposed end of the sensor connecting tracks, into the slot, and release the lever. The jaws will close to hold the sensor in place. Slide the foil pouch off to expose the sensor

11.24 Gently close the instrument lid to immerse the sensor in the sample. The test starts automatically. The display indicates progress of the test. Do not disturb the instrument during the test.

11.25 After one minute the instrument prompts the user to discard the sensor, add chlorite reagent 2 and close the lid.

11.26 Chlorite reagent 2 is added using dropper bottles. Add 6 drops of reagent to the water sample in the sample container. Gently stir using the supplied plastic paddle to mix the reagents. Close the instrument lid.

11. 27 Closing the lid starts a 2 minute countdown timer. When the 2 minutes are complete the instrument will prompt the user to insert a chlorite sensor and will display the calibration code.

11. 28 Holding the sensor through the foil pack tear open the foil along the tear line to expose the connecting tracks.

11.29 Press the blue lever to open the jaw of the sensor connector. Insert the exposed end of the sensor connecting tracks, into the slot, and release the________________________________________________________________

11 lever. The jaws will close to hold the sensor in place. Slide the foil pouch off to expose the sensor.

11. 30 Gently close the instrument lid to immerse the sensor in the sample. The test starts automatically. The display indicates progress of the test. Do not disturb the instrument during the test.

11.31 In less than one minute the chlorite result will be displayed. All results are automatically stored to the instrument log.

Do not leave water in the instrument on completion of the test.

_________________________________________________________________________

Note: The instrument is programmed to recognize a number of user errors, such as unable to read: sensor not responding or lid opened during test. The instrument will abort the test and display an error message. **Never leave water in the sample container in the instrument following analyses.** 

_________________________________________________________________________



### 12.0 Data Analysis and Calculations

12. 1 Reporting

12.1.1 Repor t results in milligrams per liter (mg /L).

12.1.2 Report results to two significant figures.



### 13.0 Method Performance

13.1 Performance data – standards

Three certified laboratories tested the performance of ChlordioX  Plus using laboratory prepared standard solutions for chlorine dioxide and chlorite . The accuracy and precision was found to be better than the acceptance criter ia shown in 17.1 (see Table 17.7 & 17.8 )

13.2 Pe rformance data – drinking water samples

Three certified laboratories tested the performance of ChlordioX  Plus using real water samples. The accuracy and precision was found to be better than the acceptance criteria shown in 17.1 (see Table 17.7 & 17.8)

13.3 Performance data – Method Comparison

ChlordioX  Plus was shown to give equivalent performance to the approved method (SM 4500

- ClO 2 E, amperometric titration), see 17.2,17.3 & 17.9



### 14.0 Pollution Prevention

14.1 Used sensors and calibration chips can be returned to Palintest for recycling. Get in touch with your nearest Palintest office for details.________________________________________________________________

12 14.2 The quantity of chemical purchased should be based on expected usage during its shelf

- life and disposal cost of unused material.

14.3 Standards should be prepared in volumes consistent with laboratory use to minimize the volume of expired standards to be disposed.



### 15.0 Waste Management

15.1 It is the laboratory’s responsibility to comply with all federal, state, and local regulations governing waste management, particularly the hazardous waste identification rules and land disposal restrictions, and to protect the air, water, and land by minimizing and controlling all releases from fume hoods and bench operations. Compliance with all sewage discharge permits and regulations is also required.

15.2 Excess reagents, samples and method process wastes should be characterized and disposed of in an acceptable manner. The MSDS sheet gives details of product composition and may be consulted for guidance on waste disposal.

15.3 For further information on waste management, consult “The Water

M anagement Manual for Laboratory Personnel”, and “Less is Better: Laboratory Chemical Management for Waste Reduction”, both available from

the American C hemical Society’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington DC, 20036.



### 16.0 References

16.1 ChloroSense  : “Measurement of Free & Total chlorine in Drinking water by

Palintest ChloroSense  ”, Sept. 2009. Available at http://www.nemi.gov or from Palintest Ltd.

16.2 “Carcinogens

- Working With Carcinogens”, Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Publication No. 77

- 206, August

1977.

16.3 “OSHA Safety and Hea lth Standards, General Industry”, (29 CFR 1910). Occupational Safety and Health Administration, OSHA 2206 (Revised, January 1976).

16.4 “Safety in Academic Chemistry Laboratories”, American Chemical Society, Committee on Chemical Safety, 3 rd Edition, 1979

16.5 Standard Test Method For Residual Chlorine in Water, ASTM D1253

- 08

16.6 Standard Method 4500

- Cl C, Standard Methods for the Examination of water

and Wastewater

16.7 Standard Method 4500

- ClO 2 B, Standard Methods for the Examination of

water and Wastewater________________________________________________________________

13 

### 17.0 Tables and Graphs

17.1 Acceptance Criteria for Performance Tests

Acceptance Criterion Section Limit (%)

Initial accuracy and precision

Ac curacy (X) 9.2.2 ±15

Precision (s) 9.2.3 ≤15

C ontinuing calibration Check

Accuracy (X) 9.3.2 ±15

Calibration verification

Accuracy (X) 10.1 ±15

M atrix spike/matrix spike duplicate

Relative percent difference 9.4.1 ≤15________________________________________________________________

14 17.2 Direct comparison between ChlordioX  Plus and Amperometric titration ( SM

4500

- ClO2 E) for determination of chlorine dioxide

17.3 Dir ect comparison between ChlordioX  Plus and Amperometric titration (SM 4500

- ClO2 E) for the determination of chlorite y = 1.0245x

R2 = 0.9997

0 1 2 3 4 5 6 7 8 9 10

0 2 4 6 8 10Chlorine Dioxide determined by ChlordioX Plus (mg/l)

Chlorine Dioxide determined by AutoCat 9000 (mg/l) Correlation between ChlordioX  Plus and the AutoCat 9000 Amperometric Titrator (equivalent to SM 4500

- ClO 2 E)

y = 0.9843x

- 0.0008

R2 = 0.9992

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0 0.5 1 1.5 2 2.5 3Chlorite concentration determined by ChlordioXPlus (mg/l)

Chlorite Concentration determined by Amperometric titration (mg/l) Correlation between AutoCat 9000 Amperometric Titration vs

ChlordioX  Plus for the determination of Chlorite

AutoCat 9000

- equiv. to Standard Methods 4500

- ClO 2 E________________________________________________________________

15 17. 4 Graph 1 Example calibration graph

17. 5 Graph 2 Example calibration graph________________________________________________________________

16 17. 6 Graph 3 Example calibration graph________________________________________________________________

18 17.7 Summary of Performance data from three Certified Laboratories (I) – Laboratory Standards

Mean values returned for Chlorine Dioxide and Chlorite in Part 1a to c of the Data Generation Plan

Acceptable limits : accuracy-%deviation = +/- 15%

precision-%RSD = +/- 15%

Utility Mean sd %RSD %deviation Mean sd %RSD %deviation Mean sd %RSD %deviation

Beaver Creek 0.45 0.018 4.0% 10% 0.54 0.027 5.0% 8% 0.47 0.02 4.3% 6%

Hamilton 0.45 0.018 4.0% 10% 0.42 0.015 3.6% 16% 1.04 0.03 2.9% 108% ClO 2 converted to

chlorite

Water One* 0.52 0.07 13.5% 4% 0.44 0.03 6.8% 12% 0.66 0.14 21.2% 32% treated river water

*Water One used treated river water

Utility Mean sd %RSD %deviation Mean sd %RSD %deviation Mean sd %RSD %deviation

Beaver Creek 0.52 0.047 9.0% 4% 0.46 0.02 4.3% 8% 0.49 0.02 4.1% 2%

Hamilton 0.53 0.028 5.3% 6% 0.5 0.025 5.0% 0% 0.08 0.011 13.8% 84% ClO 2 demand

Water One 0.51 0.02 3.9% 2% 0.54 0.08 14.8% 8% 0.46 0.02 4.3% 8% DI water DI+Int Tap water Chlorine dioxide 0.5mg/L DI water DI+Int Tap water Chlorite 0.5mg/L

Int

- Hi Ionic Strength potential interferent

To 1000 mL reagent water add 1.40 g of NaHCO3, 1.48 g of Na2SO4 and 1.54 g of NaCl ( Fluka 71627, Fluka

71959, Fischer S

- 271 respectively.) The concentration will be 1000 mg/L. Dilute to give 500 mg/L ionic
interferent in the 100 mL sample to be analyzed, i.e. Add 50 mL to the 100 mL reagent water sample container. Add 50 mL reagent water. Then spike with chlorine dioxide/chlorite standard. Analyze. Each Utility evaluated three fortified matrices (DI water, high ionic strength water and tap water).
Seven replicates were evaluated st two fortification levels (0.5 and 2.5mg/L chlorine dioxide and
chlorite)________________________________________________________________

19 17.8 Summary of Performance data from three Certified Laboratories (II) – Real water samples

Mean values returned for Chlorine Dioxide and Chlorite in Part 1a to c of the Data Generation Plan

Acceptable limits : accuracy-%deviation = +/- 15%

precision-%RSD = +/- 15%

Utility Mean sd %RSD %deviation Mean sd %RSD %deviation Mean sd %RSD %deviation

Beaver Creek 2.5 0.12 4.8% 0% 2.28 0.07 3.1% 9% 2.39 0.06 2.5% 4%

Hamilton 2.36 0.09 3.8% 6% 2.09 0.13 6.2% 16% 2.7 0.082 3.0% 8% Tap water ClO 2 converted

to chlorite

Water One 2.26 0.29 12.8% 10% 2.29 0.2 8.7% 8% 2.47 0.14 5.7% 1%

Utility Mean sd %RSD %deviation Mean sd %RSD %deviation Mean sd %RSD %deviation

Beaver Creek 2.5 0.05 2.0% 0% 2.47 0.07 2.8% 1% 2.51 0.055 2.2% 0%

Hamilton 2.52 0.065 2.6% 1% 2.5 0.09 3.6% 0% 2.19 0.036 1.6% 12% Tap water ClO 2 demand

Water One 2.47 0.07 2.8% 1% 2.55 0.15 5.9% 2% 2.43 0.06 2.5% 3% Chlorite 2.5mg/L

Chlorine dioxide 2.5mg/L DI water DI+Int Tap water

DI water DI+Int Tap water

Hamilton Tap Water Results were obtained using Well water. The well water is

known to have a chlorine dioxide demand. A blank test showed a chlorite residual of 0.14mg/L. ~0.3 to 0.4mg/L chlorine dioxide has been consumed,
therefore the expected results for chlorite was ~1.0mg/L and ~2.9 to 3.0 mg/L________________________________________________________________

20 17.9 Summary of Performance data from three Certified Laboratories (III) – Method Comparison



### Utility mean sd %deviation from

nominal 

### mean sd %deviation from

nominal % difference Chlordiox vs

SM 4500



### Beaver Creek 2.5 0.11 0% 2.52 0.145 1% 1%

Hamilton 0.5 0.04 0% 0.44 0.018 12% 14%

Water One 1.93 0.62 23% 2.18 0.1 13% 11%

Utility mean sd %deviation from

nominal 

### mean sd %deviation from

nominal % difference Chlordiox vs

SM 4500



### Beaver Creek 2.34 0.08 6% 2.46 0.03 2% 5%

Hamilton 0.46 0.03 8% 0.53 0.03 6% 13%

Water One 2.61 0.3 4% 2.51 0.04 0% 4% SM 45000 Chlordiox  Plus Chlorine dioxide 2.5mg/L

Chlorite 2.5mg/L SM 45000

Chlordiox  Plus

Hamilton carried out the method comparison with 0.5mg/L spike for chlorine dioxide and

chlorite Each Utility prepared fortified tap water samples. Seven replicates were evaluated using ChlordioX  Plus and SM

4500

- ClO2 E to determine method equivalency