## Hach Method 10272

Spectrophotometric Measurement of Copper in Finished

Drinking Water1 Hach Company Method 10272

Revision 1 .2

December 201 5

Spectrophotometric Measurement of Copper in Finished Drinking Water

1.0 Scope and Application

1.1 Th is method is for the determination of copper (Cu) in finished drinking water.

1.2 The method is applicable in the range from 0. 1 to 5.75 mg/L Cu

. High er Cu values can be

determined by sample dilution.

1.3 This method is equally effective in performance and use to EPA 200.7 for the purposes of

regulatory compliance reporting of Cu

.

2.0 Summary of Method

2.1 The Hach Cu chemistry uses 2,2 ’

- biquinoline

- 4,4’

- dicarboxylic acid ( bicinchoninic acid )

for color development. Cuprous c opper complexes with bicinchoninic acid to form a

purple colored complex. The intensity of the color of this complex is proportional to the

concentration of copper in the sample . Cu pric copper is chemically reduced. Metal and

hardness interferences are overcome through the addition of a chelating agent. Test

results are measured at 560 nm.

3.0 Interferences

3.1 The items listed in the Interfering substances table have been identified as interferences

for this chemistry. Sample treatments have been identified to overcome these

interferences.

Interfering substance Sample treatment

Acidity For sample pH < 2, raise pH with 8 N KOH.

CN

- Add 2.0 mL formaldehyde to 1 0 0 mL of

sample prior to measurement . Multiply the test

results by 1.02 to correct for the formaldehyde

addition.

Ag + Add 20 drops of saturated KCl solution to

150 mL of sample and filter to remove

precipitate.

4.0 Safety

4.1 The toxicity or carcinogenicity of each reagent used in this method has not been precisely

determined; however, each chemical should be treated as a potential health hazard.

Exposure to these chemicals should be reduced to the lowest possible level. It is

su ggested that the laboratory perform personal hygiene monitoring of each analyst using

this method and that the results of this monitoring be made available to the analyst.

4.2 Unknown samples may contain high concentrations of volatile toxic compounds. Sample

containers should be opened in a hood and handled with gloves to prevent exposure.2 4.3 This method does not address all safety issues associated with its use. The laboratory is

responsible for maintaining a safe work environment and a current awarene ss file of

OSHA regulations regarding the safe handling of any chemicals specified in this method.

A reference file of material safety data sheets (MSDSs) should be available to all

personnel involved in these analyses. Additional information on laborato ry safety can be

found in Sections 1 6 .3 and 1 6 .4.

5.0 Equipment

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

endorsement is implied. Equivalent performance may be achieved using apparatus and

materials other than those specified here, but demonstration of equivalent performance

that meets the requirements of this method is the responsibility of the laboratory.

5.1 Sampling equipment

5.1.1 Sample collection bottles

– Collect samples in acid

- cleaned glass or plasti c bottles

.

6.0 Equipment for sample analysis

6.1 Hach Company SL1000 analyzer , or equivalent

6. 2 Equipment for standard preparation

6. 2 .1 Volumetric flask s

– Glass, 1 00 mL and 1000 mL

.

6. 2 .2 Volumetric pipette s

– Glass, 2.00 mL and 4.00 mL

.

7.0 Reagent s and Standards

7.1 Metal

- free water

– Water in which Cu concentration is below the detection limit of this

method

. W ater prepared by passage of tap water through ion exchange and reverse

osmosis has been shown to be an acceptable source of reagent water.

7.2 Hach Company Copper Chemkey , Cat. No. 9429200

.

7.3 Hach Company Cu Standard Solution: 100 mg/L as Cu (Cat. No. 12842 ) or equivalent

7.4 Method detection limit (MDL) solution

7.4.1 If an MDL is required, p repare a stock MDL solution by diluting 2 .0 mL of the 100 mg/L

standard spiking solution (Section 7.3) to 10 00 mL . Measure 7 or more replicate s . Final

concentration = 0.2 mg /L Cu

.

7.5 Initial precision and recovery (IPR) solution

7.5.1 P repare a stock IPR solution by diluting 2.0 mL of the 100 mg/L standard spik ing

solution (Section 7.3) to 1 00 mL. Measure 4 or more replicates. Final concentration =

2.0 mg /L Cu

.3 8.0 Sample Collection, Preservation and Storage

8.1 Samples should be collected in acid

- cleaned glass or plastic b ottles.

8.1.1 Rinse the sample bottle several times with sample

. Fill the bottle completely full.

8.2 Preserve samples by acidifying to pH 2 or less with concentrated nitric acid

. Preserved

samples may be stored up to 6 months at room temperature prior to analysis.

9.0 Quality Control

9. 1 Each laboratory that uses this method is expected to operate a formal quality assurance

program (1 6 .1). The minimum requirements of this program consist of an initial

demonstration of laboratory capability and ongoing analyses of laboratory prepared water

standards as a test of continued performance to assess accuracy and precision.

Laboratory performance is compared to established performance criteria to determine if

the results of analyses meet the performanc e characteristics of the method.

9. 1.1 The analyst shall make an initial demonstration of the ability to generate acceptable

accuracy and precision with this method. This ability is established as described in

Section s 9. 2 and 9.3

. The laboratory shall, o n an ongoing basis, demonstrate through

analysis of the ongoing precision and recovery sample that the analysis system is in

control.

9.1.2 Accompanying QC for the determination of Cu is required per analytical batch. An

analytical batch is a set of samples processed during a contiguous 8

- hour period. Each

analytical batch must be accompanied by an ongoing precision and recovery sample

(OPR) , matrix spike sample (MS) , and matrix spike duplicate sample (MSD) resulting in

a minimum of four analyses (1 OPR, 1 sample, MS, and MSD).

9 .2 Initial demonstration of laboratory capability.

9 .2.1 To establish the ability to detect Cu the analyst shall determine the MDL using the

apparatus, reage nts, and standards that will be used in the practice of this method. An

achieved MDL less than or equal to the MDL in Section 1 3 .0 is recommended prior to

the practice of this method.

9 .2.2 Prepare and measure seven replicates of the MDL standard (Sect. 7 .4 ) according to the

procedure in Section 11

.

9.2

. 3 Using the results of the set of seven analyses, compute the MDL using the following

equation:

MMMMMM = 

# ( )

14

. 3

1 2

2

×

− − 

# ∑ ∑

n n x

x

where:

n = Number of samples (7)4 x = measured concentration of each sample

9 .3 Initial precision and recovery (IPR)

- To establish the ability to generate acceptable

precision and accuracy, the analyst shall perform the following operations:

9 .3.1 Prepare and measure four samples of the IPR standard (Sect. 7.5) according to the

procedure in Section 11

.

9 .3.2 Using the results of the set of four analyses, compute the average percent recovery (x)

and the standard deviation of the percent recovery ( s ) for Cu . Use the following equation

for calculation of the standard deviation of the percent recovery:



# ( )

1 2

2

−

−

= 

# ∑ ∑

n n x

x

s

where:

n = Number of samples (4)

x = % recovery in each sample

9 .3.2.1 Compare s and x with the corresponding limits for initial precision and recovery in Table

1 (Sect. 17) . If s and x meet the acceptance criteria, system performance is acceptable and

analysis of samples may begin. If, however, s exceeds the precision limit or x fall s

outside the range for recovery, system performance is unacceptable. In this event correct

the problem, and repeat the test.

9 .4 Ongoing precision and recovery (OPR)

- To demonstrate that the analysis system is in

control, and acceptable precision and ac curacy is being maintained with each analytical

batch, the analyst shall perform the following operations:

9 .4.1 Prepare a 2.0 mg/L recovery standard with each analytical batch as described in Sect.

7.5.1 and measure according to the procedure in Section 11

. Calculate the percent

recovery and compare this value with the limits for ongoing recovery in Table 2 (Sect.

17). If the percent recovery meets the acceptance criteria, sy stem performance is

acceptable. If the percent recovery falls outside the acceptance criteria, system

performance is unacceptable. In this event, correct the problem, and repeat the test.

9 .4.1.1 Measure a field sample. After measuring the background c oncentration, spike the sample

with a known concentration of Cu. The spike concentration should be 1

- 5 times the

background concentration, but still within the reporting range of the method. Prepare a

duplicate of this spiked sample.

9.4.1.2 Measure the spike duplicates and calculate the spike recovery for each sample and the

relative percent difference (RPD) between the two results.

Use the following equation to calculate the spike recovery:5 SSSSSSSSSS RR RRRRRR RRRR = [ CC CC ]

− [ BB BBBB ]

[ SSSS ] × 100

where:

[Conc] = the measured concentration of the spiked sample

[Bkgd] = the measured concentration of the un

- spiked sample

[Sp] = the concentration of the spike

RRRR = | CC CC 1 − CC CC 2 | � CC CC 1 + CC CC 2 2 � × 100

where:

Conc 1 = the concentration of the first spiked sample

Conc 2 = the concentration of the second spiked sample

9.4.1.3 Compare the spike recoveries and RPD with the corresponding limits in Table 2 (Sect.

17) . If recoveries and RPD meet the acceptance criteria, system performance is

acceptable and an alysis of samples may begin. If recoveries or RPD fall outside the

limits , system performance is unacceptable. In this event

, correct the problem, and repeat

the test.

9.4.1.4 The labor atory should add results that pass to IPR and previous OPR data and update QC

charts to form a graphic representation of continued laboratory performance. The

laboratory should also develop a statement of laboratory data quality for each analyte by

calcula ting the average percent recovery (R) and the standard deviation of the percent

recovery (sr). Express the accuracy as a recovery interval from R

- 2sr to R + 2sr. For

example, if R = 95% and sr = 5%, the accuracy is 85% to 105%. Control charts are

accept able for evaluating process control, but under no circumstances can the control

limits be widened beyond those established in the acceptance criteria defined in Section

13.

10 .0 Calibration and Standardization

10. 1 The Hach SL1000 ha s a built

- in calibrat ion that is automatically initiated when the

Chemkey is inserted into the analyzer . No further initial calibration is required.

10. 2 Calibration Verification

10. 2.1 To verify that the instrument is measuring Cu properly, analyze 2 .0 mg/L (Sect. 7.5) and

0.2 mg/L (Sect. 7.4) Cu standard s . Results should be within 15 percent of the actual

value. Perform this calibration verification daily while instrument is in use. If the

calibration verification standard result is outside the limit, it is unaccepta ble. In this

event

, correct the problem, and repeat the test.6 11.0 Procedure

11.1 Instrument Setup

– follow the instrument manufacturer’s instructions for instrument

setup.

11.2 Remove the Chemkey from its package by peeling the wrapper back and exposing the

barcode

.

11.2. 1 Without touching the end of the Chemkey, slide the barcode end into the analyzer

. The

analyzer will initiate the copper program.

11.3 Rinse the sample cup twice with sample

.

11 .3.1 Fill sample cup to the fill line

.

11.4 Dip th e Chemkey and the base of the analyzer into the sample cup

.

11.4. 1 Remove the analyzer from the sample cup when prompted

.

1 1

. 5 Allow the sample to react for 6 min

.

11.6 Read the sample results from the analyzer screen . Sample results are reported in mg/L

Cu.

1 2 .0 Data Analysis and Calculations

1 2 .1 Cu concentration is calculated automatically against internal instrument calibration.

13 .0 Method Performance

Performance of the method was demonstrated in multi

- lab studies comparing the method

against EPA Reference Method EPA 200.7

. The method was evaluated in low ionic

strength reference matrix as well as multiple geographically diverse finished drinking

water samples obtained from both surface water and ground water sources.

Validation Results Section Limit

Method Detection Limit 9.2 0.02 mg/L Cu

Initial M ean Recovery 9.3 99.0%

Initial Recovery Range 9 .3 88.4 %

- 110 %

Initial Precision 95% 9 .3 0.0 6

Matrix Mean Recovery 9.5 88.7%

Ma trix Recovery Range 9.4 74.9 %

– 10 2 %

Matrix Recovery Precision 95% 9.4 0. 11

1 4 .0 Pollution Prevention

1 4 .1 Follow guidelines in Section 1 5

.7 1 5 .0 Waste Management

1 5 .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 air, water, and land by minimizing and control

all releases from fume hoods and bench operations. Compliance with all sewage

discharge permits and regulations is also required.

15.2 For further information on waste management, consult “The Waste Management manual

for Laboratory Personne l”, and “Less is Better: Laboratory Chemical Management for

Waste Reduction”, both available from the American Society’s Department of

Government Relations and Science Policy, 1155 16 th Street N.W., Washington, D.C.

20036.

1 6 .0 References

1 6 .1 “Protocol for the Evaluation of Alternate Test Procedures for Organic and Inorganic

Analytes in Drinking Water,” USEPA, EPA

- 815

- R

- 15

- 007, February 2015

.

16.2 40 CFR 136, Appendix B.

1 6 .3 “OSHA Safety and Health Standards, General Industry,” (29 CFR 1910), Occupational

Safety and Health Administration, OSHA 2206 (Revised, January 1976)

1 6 .4 “Safety in Academic Chemistry Laboratories,” American Chemical Society, Committee

on Chemical Safety, 3 rd Edition, 1979.

16.5 “Water Analysis Handbook,” Hach Company

, 8 th Edition, 2013

.

17 .0 Tables

1 7 .1 Acceptance Criteria for Performance tests

– The QC performance criteria for this method

were performed with a Hach Company SL1000 analyzer and Copper Chemkey Reagents

.

Table 1. Initial Precision and Recovery Acceptance Criteria

Parameter Acceptance Criteria

Relative Standard Deviation ≤ 10%

Percent Recovery 90

- 110%

Table 2. Ongoing Precision and Recovery Acceptance Criteria

Parameter Acceptance Criteria

Lab Fortified Blank Recovery 90

- 110%

Sample Matrix Spike Recovery 70%

- 130%

Sample Matrix Spike RPD ≤ 10%1 8 .0 Glossary of Definitions and Purposes

The definitions and purposes are specified to this method but have been conformed to common

usage as much as possible.

1 8 .1 Units of weight and measure and their abbreviations

18.1.1 Symbols

o C : degrees Celsius

18. 1.2 Alphabetical characters

mg/L : milligram per liter

18. 2 Definitions, acronyms, and abbreviations

18. 2.1 MDL : Method detection limit

18.2.2 IPR : Initial precision and recovery

18.2.3 OPR : On

- going precision and recovery

18.2.4 MS : Matrix spike

18.2.5 MSD : Matrix spike duplicate

18.2.6 LIS : Low ionic strength , deionized water