HACH COMPANY

Validation Study Report Hach Company SPADNS 2 

(Arsenic-Free) Fluoride Method 10225 

Prepared by:

Dr. Cary B. Jackson

8/20/2010
Validation Study Report

Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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Background

Purpose of Study

The purpose of this study was to evaluate the proposed Hach Company 

SPADNS 2 (Arsenic-Free) Fluoride Method 10225 against the USEPA reference 

fluoride method (SM4500-F D) for approval and use in USEPA regulatory drinking water 

programs.

Method Summary

Fluoride reacts with a zirconium SPADNS dye. The loss of color during this 

reaction is proportional to the fluoride concentration in the sample. The SPADNS 2 

reagent contains a non-toxic species to prevent chlorine interference rather than sodium 

arsenite that is used in the reference method. Test results are measured at 580 nm.

Method Justification

The presence of chlorine and its oxidizing capability is a known interference in

the measurement of fluoride with SPADNS chemistry. To mitigate this interference, the 

USEPA reference method calls for the addition of sodium arsenite. However, arsenite 

is a highly toxic chemical that is hazardous to the environment. The SPADNS 2 method 

replaces sodium arsenite with a non-toxic and non-hazardous a proprietary chlorine 

scavenger that produces results that are equivalent or better than the SPADNS arsenite 

method.

Scope of Method

The SPADNS 2 method is applicable for use in drinking water, surface and saline 

waters, and domestic and industrial wastewaters. The measurement range for this 

method is in the range from 0.10 to 2.00 mg F- /L.

Study Design and Objectives

The design and objectives of this validation study are detailed in the Validation 

Study Plan1 appended to this report.

 1 Revised Hach Validation Study Plan, August 2010
Validation Study Report

Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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Study Implementation

Study Sponsor

The organizational sponsor responsible for managing this study is Hach 

Company.

Study Participants

The participants, laboratories, and test matrices were selected from 

geographically diverse regions of the United States and are listed in the following table.

Matrix Facility Laboratory Source of Treated Test 

Water

Loveland, Colorado Water 

Treatment Plant

Hach Company Surface water from river

Roseville, California Water 

Treatment Plant

Roseville, California Water 

Treatment Plant

Surface water from river

Storm Lake, Iowa Water 

Treatment Plant

Storm Lake, Iowa Water 

Treatment Plant

Ground Water

Tier Study

The validation study was performed under Tier II requirements.

Sample Collection and Distribution

Matrix samples for this validation study were collected at the tap for each 

laboratory. Collection followed standard USEPA sampling procedures2

.

Analysis Description

The description of the type and number of analyses are described in the 

Validation Study Plan appended to this report.

Data Reporting and Validation

Data reporting and validation of data are described by the following processes:

Data Collection, Laboratory Submission, and Validation

For each laboratory performing analyses, results from each test measurement 

were read from a Fluoride Pocket Colorimeter II and manually transferred to an 

 2 40CFR 141.23
Validation Study Report

Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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electronic spread sheet. Each laboratory then submitted the electronic spread sheet to 

the Hach Study Director for review and statistical evaluation. 

Results

Summary results of the validation study are listed in Tables 1-3.

 

Table 1 - City of Roseville Water Treatment Plant Summary Results 

Matrix

Standard Method 4500-F D Hach Method 10225

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Low Ionic 

Strength 

Reagent 

Water

0.08 0.30 0.04 0.10

High Ionic 

Strength 

Reagent 

Water

0.06 0.20 0.05 0.20

Initial Precision and 

Recovery

Initial Precision and 

Recovery

Average 

Percent (%) 

Recovery

Standard 

Deviation

Average 

Percent (%) 

Recovery

Standard 

Deviation

Low Ionic 

Strength 

Reagent 

Water

103 0.03 101 0.03

High Ionic 

Strength 

Reagent 

Water

100 0.03 106 0.02

Matrix Analysis Matrix Analysis

Average 

Result 

(mg/L)

Percent (%) 

Relative 

Standard 

Deviation

Average 

Result 

(mg/L)

Percent (%) 

Relative 

Standard 

Deviation

Roseville 

Tap 0.93 2.4 0.90 2.7
Validation Study Report

Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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Table 2 – Storm Lake Treatment Plant Summary Results 

Matrix

Standard Method 4500-F D Hach Method 10225

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Low Ionic 

Strength 

Reagent 

Water

0.11 0.40 0.08 0.20

High Ionic 

Strength 

Reagent 

Water

0.05 0.20 0.05 0.20

Initial Precision and 

Recovery

Initial Precision and 

Recovery

Average 

Percent (%) 

Recovery

Standard 

Deviation

Average 

Percent (%) 

Recovery

Standard 

Deviation

Low Ionic 

Strength 

Reagent 

Water

95 0.02 99 0.02

High Ionic 

Strength 

Reagent 

Water

96 0.02 100 0.02

Matrix Analysis Matrix Analysis

Average 

Result 

(mg/L)

Percent (%) 

Relative 

Standard 

Deviation

Average 

Result 

(mg/L)

Percent (%) 

Relative 

Standard 

Deviation

Storm 

Lake Tap 1.22 2.2 1.23 1.4
Validation Study Report

Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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Table 3 – Loveland/Fort Collins Water Treatment Plant

Matrix

Standard Method 4500-F D Hach Method 10225

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Low Ionic 

Strength 

Reagent Water

0.02 0.10 0.02 0.10

High Ionic 

Strength 

Reagent Water

0.07 0.20 0.02 0.20

Initial Precision and 

Recovery

Initial Precision and 

Recovery

Average 

Percent (%) 

Recovery

Standard 

Deviation

Average 

Percent (%) 

Recovery

Standard 

Deviation

Low Ionic 

Strength 

Reagent Water

102 0.01 100 0.01

High Ionic 

Strength 

Reagent Water

106 0.01 102 0.01

Matrix Analysis Matrix Analysis

Average 

Result 

(mg/L)

Percent (%) 

Relative 

Standard 

Deviation

Average 

Result 

(mg/L)

Percent (%) 

Relative 

Standard 

Deviation

3

0.96

Loveland/Fort 

Collins Tap 

(non-distilled)

0.7 0.94 0.6

4

1.01

Loveland/Fort 

Collins Tap 

(distilled)

7.4 1.00 7.9

 3 Matrix collected on June 8, 2010

4 Matrix Collected on August 9, 2010
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Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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Development of QC Acceptance Criteria

Development of quality control acceptance criteria for method detection limit (MDL) and 

initial precision and recovery (IPR) followed the criteria detailed in Appendix D, Tier 2 of 

Section 9 of the guidance document for EPA approval of new methods5. A summary of 

the pooled quality control acceptance criteria is described in Table 4.

Table 4 – Pooled Statistical Results

Matrix

Standard Method 4500-F D Hach Method 10225

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Method 

Detection 

Limit (mg/L)

Minimum 

Quantitation 

(mg/L)

Low Ionic 

Strength 

Reagent 

Water

0.06 0.20 0.04 0.10

High Ionic 

Strength 

Reagent 

Water

0.05 0.15 0.03 0.10

Initial Precision and 

Recovery

Initial Precision and

Recovery

6 Precision of 

Recovery 

(RSD)

Percent (%) 

Recovery 

Range

6

Percent (%) 

Recovery 

Range

Precision of 

Recovery

(RSD)

Low Ionic 

Strength 

Reagent 

Water

Lower 

Limit

Upper 

Limit 0.02

Lower 

Limit

Upper 

Limit 0.02

84 116 95 105

High Ionic 

Strength 

Reagent 

Water

Lower 

Limit

Upper 

Limit 0.02

Lower 

Limit

Upper 

Limit 0.02

82 119 93 113

 5 Protocol for EPA Approval of New Methods for Organic and Inorganic Analytes in Wastewater and Drinking 

Water, March 1999 EPA-821-98-003 6 95% Confidence
Data Analysis/Discussion

MDL Results

Method detection limit results for from each laboratory yielded expected results from 

that of Hach Company single-laboratory data. The range of results of the LIS matrix 

were 0.02 mg/L F- to 0.11 mg/L F- for the reference method and 0.02 mg/L Fto 0.08 

mg/L Ffor the Hach method. For the reference HIS matrix, the range was 0.05 mg/L Fto 0.07 mg/L F- and 0.02 mg/L F- to 0.07 for the Hach method.

Initial precision and recovery results were similar and yielded expected results from that 

of Hach Company single-laboratory data. The range of recovery results of the LIS 

matrix were 95% to 103% for the reference method and 99% to 101% for the Hach 

method. For the reference HIS matrix, the recovery range was 96% to 106 % mg/L Fand 0.02 mg/L F- to 0.07 and 100% to 106% for the Hach method. For both the LIS and 

HIS matrix, the range of precision (standard deviation) for the reference method 0.01 to 

0.03 and likewise, 0.01 to 0.03 for the Hach method.

Matrix result %RSDs ranged from 0.7 to 2.4 for the reference method and 0.6 to 2.7 for 

the Hach method. An addition to the three sets of matrix sample analyses, the 

Loveland/Fort Collins laboratory performed a distillation analysis. The %RSD of the 

distilled matrix with the reference method was 7.4% and 7.9 % with the Hach method.

Conclusions

A validation study was conducted to compare the performance of the Hach Method to 

that of the EPA approved reference method. Laboratory results from each of the 

laboratories indicate that the Hach Method 10025 is equally effective in mitigating 

chlorine interference and analytical performance for the determination of fluoride to that 

of the EPA reference method SM 4500-F D.
Validation Study Report

Hach Company SPADNS 2 (Arsenic-Free) Fluoride Method 10225

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Appendices

Appendix A – EMMC formatted Hach Method 10025 (Hach Method 10025 SPADNS 

II.pdf)

Appendix B – Revised Validation Study Plan (SPADNSIIValidationPlan.pdf)

Appendix C – Supporting Data (Supporting Data.xls)