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EasyChem Methodology 

Nitrate by Discrete Analysis 

Easy (1-Reagent) Nitrate Method 

(Colorimetric, Automated, 1 Reagent) 

Revision Date: 

November 12, 2011 

Craig R. Chinchilla 

900 Jorie Blvd., Suite 35 

Oak Brook, Illinois 60523 
 

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CONTENTS 

1. Scope and Application........................................................................................3 

2. Summary of Method...........................................................................................3 

3. Common Abbreviations.......................................................................................3 

4. Interferences...................................................................................................4 

5. Safety............................................................................................................4 

6. Equipment and Supplies......................................................................................4 

7. Reagents and Standards.......................................................................................5 

8. Sample Collection, Preservation, and Storage.............................................................7 

9. Quality Assurance/Quality Control. ........................................................................8 

10. Calibration and Standardization............................................................................14 

11. Procedure......................................................................................................15 

12. Data Analysis and Calculations..............................................................................19 

13. Method Performance.........................................................................................19 

14. Pollution Prevention.........................................................................................19 

15. Waste Management...........................................................................................19 

16. References.....................................................................................................20 

17. Tables, Diagrams, and Validation Data...................................................................20 

18. Definitions.....................................................................................................20 

19. Consumables...................................................................................................23 
 

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 EasyChem Applications

Easy (1-Reagent) Nitrate 

Nitrate in Water and Wastewater

1.0 Scope and Application 

1.1 This method is applicable to the analysis of nitrate (CASRN 14797-55-8) in 

wastewater and drinking water. If this method is being used for compliance with 

the Clean Water act (CWA), the flexibility to modify this method as described in 

CFR 136.6 applies. Modifications to this method are not allowed when it is 

being used for compliance monitoring under the Safe Drinking Water Act 

(SDWA). Requirements for establishing method equivalency for CWA use are 

given in Section 9.1.2. 

 

2.0 Summary of Method 

2.1 The automated procedure for the determination of nitrate utilizes the reaction 

whereby nitrate is reduced to nitrite by a proprietary Chemical R1 under acidic 

conditions to form a soluble dye which is measured colorimetrically at 546nm. 

The final product measured represents the nitrite ion originally present plus that 

formed from the nitrate. Regardless of the sample matrix used, recovery of NO3

to NO2 is consistently between 95% and 105% recovery. 

In order to determine nitrate levels, the nitrite alone must be subtracted from the 

total (nitrate+nitrite). 

3.0 Definitions 

3.1 The abbreviations below are specific to this method, but have been conformed to 

common usage as much as possible. 

 CWA Clean Water Act 

 DI Water Deionized Water 

 EPA Environmental Protection Agency 

 CASRN Chemical Abstracts Service Registry Number 

 CERCLA Comprehensive Environmental Resource Compensation Liability Act 

 IPR Initial Precision and Recovery 

 MDL Method Detection Limit 

 MS Matrix Spike 

 MSD Matrix Spike Duplicate 

 MSDS Material Safety Data Sheets 

 NIST National Institute of Standards and Technology 

 OSHA Occupational Safety and Health Administration 

 QC Quality Control 

 RCRA Resource Conservation and Recovery Act 
 

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SWDA Safe Water Drinking Act 

4.0 Interferences 

 4.1 Particulates create an interference, samples may be pre-filtered. 

4.2 Residual chlorine can produce a negative interference by limiting reduction 

efficiency. Before analysis, samples should be checked and if required, 

dechlorinated with sodium thiosulfate. 

5.0 Safety 

 5.1 The toxicity or carcinogenicity of each analyte or reagent 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 suggested that the laboratory perform personal hygiene monitoring of 

each analyst using this method and the results of this be made available to the 

analyst. 

5.2 This method does not address safety issues associated with its use. The 

laboratory is responsible for maintaining a safe work environment and a current 

awareness file of OSHA regulations regarding the safe handling of the chemicals 

specified in this method. A reference file of material safety data sheets (MSDS) 

should be available to all personnel involved in the analyses. Additional 

information on laboratory safety can be found in References 16.4 - 16.6. 

 5.3 List of Raw Materials 

 Unless otherwise specified all chemicals should be of ACS grade or equivalent 

 Safety Classification 

 

 5.3.1 R1 – Chemical IR (Proprietary) acidic 

 5.3.2 Potassium nitrate, KNO3 (CASRN 7757-79-1) toxic 

 

6.0 Equipment and Supplies 

 

6.1 EasyChem analyzer 

 

6.2 Computer for data collection 

 

6.3 Printer 

7.0 Reagents and Standards 

7.1 Preparation of Reagents 
 

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7.1.1 R1 Easy (1-Reagent) Nitrate Solution (Proprietary) 

R1 - 1.0 Liter Size. Part Number E/R1-10 

R1 - 0.5 Liter Size. Part Number E/R1-05 

Available for purchase from: 

Craig R. Chinchilla 

900 Jorie Blvd., Suite 35 

Oak Brook, IL 60523 

Phone: 630 645-0600 

Fax: 630 645-0601 

7.2 Preparation of Standards 

7.2.1 Stock Standard, 1000mg/L N-NO3

Potassium nitrate 7.218g 

DI water to 1000mL 

Dissolve 7.218g of potassium nitrate, in approximately 600mL of DI 

water. Mix thoroughly and dilute to one liter with DI water. 

 7.2.2 Working Standard Solution A, 100mg/L 

 1000 mg/L Stock Standard 10mL 

DI water to 100mL 

Dilute 10mL of 1000 mg/L Stock Standard A in a 100mL volumetric 

flask with DI water 

 7.2.3 Working Standard Solution B, 10mg/L 

 100 mg/L Working Standard Solution A 10mL 

DI water to 100mL 

Dilute 10mL of 100 mg/L Working Standard A in a 100mL volumetric 

flask with DI water 

7.2.4 Working calibrants may be prepared to cover the desired range by adding 

the appropriate amount of working standard solutions (Section 7.2.3) to 

100mL volumetric flasks that contain approximately 80mL DI water. 

Dilute the solutions to 100mL with DI water. 

Prepare working calibration standards daily. See the Table on page 7 for 

specific directions. 

The following formula can be used to calculate the amount of stock (or 

working) calibrant to be used. 

 C1V1 = C2V2 
 

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 where: 

 C1 = desired concentration (in mg/L) of working calibrant to be 

prepared 

V1 = final volume (in mL) of working calibrant to be prepared 

(generally 100mL) 

 C2 = concentration (in mg/L) of stock (or working) calibrant 

 V2 = volume (in mL) of stock (or working) calibrant to be used 

Rearranging the equation to solve for V2 yields: 

 V2 = C1V1

 C2

For example, to prepare a 1.0mg/L working calibrant from a 1000mg/L 

stock calibrant, use 0.1mL (100μL) of the stock calibrant in 100mL final 

volume. 

 V2 = (1.0mg/L) (100mL)

 1000mg/L 

 V2 = 0.1mL 

Add this amount of stock calibrant to the volumetric flask and then dilute 

to volume. 

Standard curves in desired ranges can be derived from the formula above 

or from the table on page 7 of this method 
 

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The following table provides the quantity of secondary standard necessary to prepare 

working standards of the specified concentration. 

Working Calibration 

Standard 

Concentration 

(mg/L) 

(100mL) 

Standard Solution Volume Added to Volumetric Flask 

 Working Standard 

B 

Concentration 

(Section 7.2.3) 

10 mg/L 

Working Standard 

A 

Concentration 

(Section 7.2.2) 

100 mg/L 

Stock Standard 

Concentration 

(Section 7.2.1) 

1000 mg/L 

0.0 

0.001 10 μL 1 μL 

0.005 50 μL 5 μL 

0.01 100 μL 10 μL 1 μL 

0.05 500 μL 50 μL 5 μL 

0.10 1,000 μL 100 μL 10 μL 

0.50 5,000 μL 500 μL 50 μL 

1.00 10,000 μL 1,000 μL 100 μL 

5.00 5,000 μL 500 μL 

10.0 10,000 μL 1,000 μL 

50.0 5,000 μL 

7.3 DI water refers to high quality water, Type I or Type II as defined in ASTM 

 Standards, Part 31, D1193-91. 

8.0 Sample Collection, Preservation, and Storage 

8.1 Sample preservation and holding time requirements for drinking water samples 

are as follows: 

8.1.1 For nitrate: Chill the sample to 40

C and analyze within 48 hours, unless 

the sample is chlorinated. If the sample is chlorinated, chill the sample to 

40

C and analyze within 14 days. 

8.1.2 For nitrite: Chill the sample to 40

C and analyze within 48 hours. Do 

NOT acid preserve! 

8.1.3 For nitrate-nitrite (combined): Acidify to pH<2 with concentrated H2SO4

at the time of collection, and analyze within 28 days. 
 

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8.2 For wastewater samples, requirements are nearly identical, except that samples to 

be analyzed for nitrate only must be analyzed within 48 hours whether or not 

chlorine is present, and sample to be analyzed for nitrate-nitrite must be acidified 

to pH<2 with concentrated H2SO4 at the time of collection, chilled to <60

C and 

analyzed within 28 days. 

8.2.1 In all cases, samples should be analyzed as soon as possible after 

collection. For the analysis of nitrate or nitrite only, samples must be 

chilled to 60

C and analyzed within 48 hours. 

 

9.0 Quality Assurance/Quality Control 

 9.1 Each laboratory that uses this method is required to operate a formal quality 

assurance program (Reference 16.3). The minimum requirements of this 

program consist of an initial demonstration of laboratory capability, and the 

periodic analysis of QCSs and MS/MSDs as a continuing check on performance. 

If the determined concentrations are not within +/- 10% of the stated values, 

performance of the determinative step of the method is unacceptable. The source 

of the problem must be identified and corrected before continuing with on-going 

analysis. 

 9.1.1 The analyst shall make an initial demonstration of the ability to generate 

acceptable precision and accuracy with this method. This ability is 

established as described in Section 9.2. 

 9.1.2 In recognition of advances that are occurring in analytical technology, 

and to allow the analyst to overcome sample matrix interferences, the 

analyst is permitted certain options to improve performance or lower the 

costs of measurements. Alternate determinative techniques, such as the 

substitution of spectroscopic or immuno-assay techniques, and changes 

that degrade method performance, are not allowed. If an analytical 

technique other than the techniques specified in this method is used, that 

technique must have specificity equal to or better than the specificity of 

the techniques in this method for the analytes of interest. 

 9.1.2.1 Each time a modification is made to this method, the analyst is 

required to repeat the procedure in Section 9.2. If the detection 

limit of the method will be affected by the change, the laboratory 

is required to demonstrate that the MDL (40 CFR Part 136, 

Appendix B) is lower than one-third the regulatory compliance 

level or as low as or lower than that listed in Section 13. If 

calibration will be affected by the change, the analyst must 

recalibrate the instrument per Section 10. The laboratory is 

required to maintain records of modifications made to this 

method. These records include the information in this 

subsection, at a minimum. 

9.1.2.2 The names, titles, addresses, and telephone numbers of the 

analyst(s) who performed the analyses and modification, and of 
 

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the quality control officer who witnessed and will verify the 

analyses and modification. 

9.1.2.3 A narrative stating the reason(s) for the modification. 

9.1.2.3 Results from all quality control (QC) tests comparing the 

modified method to this method including: 

(a) Calibration (Section 10.3) 

(b) Calibration verification (Section 9.5) 

(c) Initial precision and recovery – IPR (Section 9.2.2) 

(d) Laboratory reagent blank – LRB (Section 9.4) 

(e) Laboratory Control Sample – LCS (Section 9.6) 

(f) Matrix spike and matrix spike duplicate (Section 9.3) 

9.1.2.4 Data that will allow an independent reviewer to validate each 

determination by tracing the instrument output (optical density 

and reading) to the final result. These data are to include: 

(a) Sample numbers and other identifiers 

(b) Analysis dates and times 

(c) Analysis sequence/run chronology 

(d) Sample weight or volume 

(e) Sample volume prior to each cleanup step, if applicable 

(f) Sample volume after each cleanup step, if applicable 

(g) Final sample volume prior to injection (Section 11.0) 

(h) Injection volume (Section 11.0) 

(i) Dilution data, differentiating between dilution of a 

sample or modified sample 

(j) Instrument and operating conditions 

(k) Other operating conditions (temperature, incubation 

times, etc.) 

(l) Detector (operating condition, etc.) 

(m) Printer tapes, disks, and other recording of raw data 

(n) Quantization reports, data system outputs, and other data 

necessary to link raw data to the results reported 

 9.1.3 Analyses of matrix spike and matrix spike duplicate samples are required 

to demonstrate method accuracy and precision and to monitor matrix 

interferences (interferences caused by the sample matrix). The procedure 

and QC criteria for spiking are described in Section 9.3. 

 9.1.4 Analyses of blanks are required to demonstrate freedom from 

contamination and that the compounds of interest and interfering 

compounds have not been carried over from a previous analysis. The 

procedures and criteria for analysis of a blank are described in Section 

9.4. 
 

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 9.1.5 The laboratory shall, on an ongoing basis, demonstrate through the 

analysis of the LCS that the analysis system is in control. This procedure 

is described in Section 9.6. 

 9.1.6 The laboratory should maintain records to define the quality of data that 

is generated. Development of accuracy statements is described in 

Sections 9.3.8 and 9.6.3. 

 9.1.7 Accompanying QC for the determination of nitrate is required per 

analytical batch. An analytical batch is a set of samples analyzed at the 

same time, to a maximum of 10 samples. Each analytical batch of 10 or 

fewer samples must be accompanied by a laboratory blank (Section 9.4), 

an LCS (Section 9.6), and a matrix spike and matrix spike duplicate 

(MS/MSD, Section 9.3), resulting in a minimum of five analyses (1 

sample, 1 blank, 1 LCS, 1 MS, and 1 MSD) and a maximum of 14 

analyses (10 samples, 1 blank, 1 LCS, 1 MS, and 1 MSD) in the batch. 

If greater than 10 samples are analyzed at one time, the samples must be 

separated into analytical batches of 10 or fewer samples. 

9.2 Initial demonstration of laboratory capability 

 9.2.1 Method Detection Limit (MDL)—To establish the ability to detect 

nitrate at low levels, the analyst shall determine the MDL per the 

procedure in 40 CFR 136, Appendix B using the apparatus, reagents, and 

standards that will be used in the practice of this method. An MDL less 

than or equal to the MDL listed in Section 13.0 must be achieved prior to 

practice of this method. Calculate the MDL as follows: 

 MDL = (t) x (S) 

 Where, t = Student’s t value for a 99% confidence level and a standard 

deviation estimate with n-1 degrees of freedom (t = 3.143 for seven 

replicates), S = standard deviation of the replicate analysis. MDLs 

should be determined every 6 months, when a new operator begins work, 

or whenever there is a significant change in the background or 

instrument response. 

 9.2.2 Initial Precision and Recovery (IPR)—To establish the ability to generate 

acceptable precision and accuracy, the analyst shall perform the 

following operations: 

 9.2.2.1 Analyze four samples of the LCS according to the procedure 

beginning in Section 10.0. 

 9.2.2.2 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 nitrate. Use Equation 1 for calculation of the 

standard deviation of the percent recovery. 
 

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EQUATION 1

 s = 

 where: 

 x = percent recovery in each sample 

 n = number of samples 

s = standard deviation of the population

 9.2.3 Compare s and X with the acceptance criteria. If s exceeds the precision 

limit or X falls outside the range for recovery, system performance is 

unacceptable and the problem must be found and corrected before analyses can 

begin. 

 9.3 Matrix spike/matrix spike duplicate (MS/MSD)—The laboratory shall spike, in 

duplicate, a minimum of 10 percent of all samples (one sample in duplicate in 

each batch of ten samples) from a given sampling site. 

 9.3.1 The concentration of the spike in the sample shall be determined as 

follows: 

 9.3.1.1 If, as in compliance monitoring, the concentration of nitrate in 

the sample is being checked against a regulatory concentration 

limit, the spiking level shall be at that limit or at 1 to 5 times 

higher than the background concentration of the sample 

(determined in Section 9.3.2), whichever concentration is higher. 

 9.3.1.2 If the concentration of nitrate in a sample is not being checked 

against a limit, the spike shall be at the concentration of the LCS 

or at 1 to 5 times higher than the background concentration, 

whichever concentration is higher. 

 9.3.2 Analyze one sample aliquot out of each set of ten samples from each site 

or discharge according to the procedure beginning in Section 11.0 to 

determine the background concentration (B) of nitrate. 

 9.3.2.1 Spike this sample with the amount of nitrate stock solution 

(Section 7.2.1) to produce a concentration in the sample of 1 

mg/L. If necessary, prepare another stock solution appropriate to 

produce a level in the sample at the regulatory compliance limit 

or at 1 to 5 times the background concentration (per Section 

9.3.1). 

∑x2 - (∑x) 2

 n____ 

 n-1 
 

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 9.3.2.2 Spike two additional sample aliquots with the spiking solution 

and analyze these aliquots to determine the concentration after 

spiking (A). 

 9.3.3 Calculate the percent recovery of nitrate in each aliquot using Equation 

2. 

EQUATION 2

P = 100 (A – B)

 T 

Where: 

P = Percent recovery 

A = Measured concentration of nitrate after spiking 

B = Measured background concentration of nitrate 

T = True concentration of the spike

 9.3.4 Compare the spike recovery percentage to the QC acceptance criteria of 

90 to 110%. If spike percent recovery is outside of the acceptance 

criteria, and the recovery of the LCS in the ongoing precision and 

recovery test (Section 9.6) for the analytical batch is within the 

acceptance criteria, an interference is present. In this case, the result may 

not be reported for regulatory compliance purposes. 

 9.3.5 If the results of both the MS/MSD and the LCS test fail the acceptance 

criteria, the analytical system is judged to be out of control. In this case, 

the problem shall be identified and corrected, and the analytical batch 

reanalyzed. 

 9.3.6 Compute the relative percent difference (RPD) between the two spiked 

sample results using Equation 3. 

EQUATION 3 

RPD = ⏐D1 – D2⏐ x 100 

---------------

 [D1 + D2]/2 

where: 

RPD = Relative percent difference 

D1 = Concentration of nitrate in the spiked sample 

D2 = Concentration of nitrate in the spiked duplicate sample

 9.3.7 The precision of the RPD for the MS/MSD should be less than 20%. If 

the RPD is greater than the acceptance criteria, the analytical system is 
 

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judged to be out of control, and the problem must be immediately 

identified and corrected, and the analytical batch reanalyzed. 

 9.3.8 As part of the QC program for the laboratory, method precision and 

accuracy for samples should be assessed and records should be 

maintained. After the analysis of five spiked samples in which the 

recovery passes the test in Section 9.3.4, compute the average percent 

recovery (Pa) and the standard deviation of the percent recovery (sp). 

Express the accuracy assessment as a percent recovery interval from Pa – 

3sp to Pa + 3sp. For example, if Pa = 100% and sp = 5% for five analyses, 

the accuracy interval is expressed as 85 – 115%. Update the accuracy 

assessment on a regular basis (e.g., after each five to ten new accuracy 

measurements). 

 9.4 Laboratory Reagent Blanks (LRB)—Laboratory reagent water blanks are 

analyzed to demonstrate freedom from contamination. 

 9.4.1 Analyze a reagent water blank initially and with each analytical batch. 

The blank must be subjected to the exact same procedural steps as the 

samples. 

 9.4.2 If nitrate is detected in the blank at a concentration greater than the 

MDL, analysis of samples is halted until the source of contamination is 

eliminated and a blank shows no evidence of contamination. 

 9.5 Calibration Verification—Verify calibration of the analytical equipment before 

and after each analytical batch of 14 or fewer measurements. (The 14 

measurements will normally be 10 samples, 1 reagent blank, 1 LCS, 1 MS, and 1 

MSD). This can be accomplished by analyzing the mid-range calibration 

standard and verifying that it is within +/- 10% of the true value. (The 

concentration of the calibration verification depends on the calibration range 

being used.) Failure to attain recoveries within the acceptance criteria requires 

recalibration of the analysis system. 

 9.6 Laboratory Control Sample (LCS)—To demonstrate that the analytical system is 

in control and acceptable precision and accuracy is being maintained with each 

analytical batch, the analyst shall perform the following operations. 

 9.6.1 Analyze a LCS with each analytical batch according to the procedure in 

 Section 11.0. 

 9.6.2 If the results for the LCS are within +/-10% of the true value, analysis of 

the batch may continue. If, however, the concentration is not within this 

range, the analytical process is not in control. In this event, correct the 

problem, repeat the LCS test, and reanalyze the batch. 

 9.6.3 The laboratory should add results that pass the specification in Section 

9.6.2 to IPR and previous LCS data and update QC charts to form a 

graphic representation of continued laboratory performance. The 
 

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laboratory should also develop a statement of laboratory data quality for 

nitrate by calculating the average percent recovery (R) and the standard 

deviation of the percent recovery (sr). Express the accuracy as a 

recovery interval from R – 3sr to R + 3sr. For example, if R = 100% and 

sr = 5%, the accuracy is 85% to 115%. 

 9.7 Reference Sample—To demonstrate that the analytical system is in control, the 

laboratory may wish to periodically test an external reference sample, such as a 

Standard Reference Material (SRM) available from the National Institutes of 

Standards and Technology (NIST). Corrective action should be taken if the 

measured concentration significantly differs from the stated concentration. 

10.0 Calibration and Standardization 

10.1 Working Standards should be prepared as required to cover the range of analysis 

at a minimum of three standards and a blank. If analyzing samples not dissolved 

in pure DI water, dilute the working standards with sample matrix solution. 

10.2 Calibration should include a minimum of 4 standards and a blank. The linear 

correlation coefficient (r 2) should be greater than 0.995. 

10.3 Prepare standard curve by plotting instrument response against concentration 

readings. A calibration curve may be fitted to the calibration standards response 

data using the computer. Acceptance or control limits should be established 

using the difference between the measured reading of the calibration standards 

and the “true” value concentration. 

10.4 After the calibration has been accomplished, it must be verified by the analysis of 

a suitable Quality Control Sample (QCS). If measurement exceeds the +/-10% of 

the QCS true value the analysis should be terminated and the instrument 

recalibrated. The new calibration must be verified before continuing analysis. 

Periodic reanalysis of the CCV is recommended as a continuing calibration 

check. 
 

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11.0 Procedure 

11.1 User parameter settings 

 11.1.1 Flow Cell 

Standard 10 mm pathlength 

11.2 Method Parameters 

11.2.1 Method Parameters 

Range 0.001-0.150mg/L
 

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11.2.2 Method Parameters 

Range 0.020-2.0mg/L
 

Page 17 of 23 

11.2.3 Method Parameters 

Range 0.050-10mg/L
 

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11.2.4 Method Parameters 

Range 0.25-50mg/L
 

Page 19 of 23 

12.0 Data Analysis and Calculations 

 12.1 Report results to three significant figures for nitrate and/or nitrite concentrations 

 above the MDL. Do not report results below the MDL unless required by the 

 permitting authority or in the permit. 

13.0 Method Performance 

 13.1 Performance data using aqueous standards 

 

 Test Range 0.050-10 mg/L N-NO3 

 Sensitivity at 10 mg/l as N 1.8 O.D. 

 Reagent Absorbance 0.07 

 Linear Correlation Coefficient 0.999 

 Recovery ratio 10 ppm N-NO2 90-110% 

versus 10 ppm N-NO3 

 Method Detection Limit 0.011mg/L 

 (determined according to 40 CFR 136, Appendix B) 

Note: the above performance specifications were developed with the exclusive use of 

genuine parts and consumables. 

14.0 Pollution Prevention 

 14.1 Standards should be prepared in volumes consistent will 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 Samples preserved with HCl or H2SO4 to a pH<2 are hazardous and must be 

 neutralized before being disposed, or must be handled as a hazardous waste. 

 

15.3 For further information on waste management, consult ”The Waste Management 

 Manual for laboratory Personnel,” and “Less is Better: Laboratory Chemical 

 Management for Waste Reduction,” both available from the American Chemical 

Society’s Department of Government Relations and Science Policy, 1155 16th

Street, N.W., Washington DC, 20036. 

16.0 References 
 

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16.1 Methods for the Determination of Inorganic Substances in Environmental 

Samples – Nitrate 353.2 Rev. 2.0 Determination of Nitrate-Nitrite by Automated 

Colorimetry, U.S. EPA National Exposure Research Laboratory EPA600/R93/100 (NTIS PB 94-120821), 1993. 

 16.2 Grasshoff, K., Technicon International Congress. 

16.3 “Handbook of Analytical Quality Control in Water and Wastewater 

Laboratories,”USEPA EMSL, Cincinnati, OH EPA-600/4-79-019, March 1979. 

16.4 “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. 

 16.5 “OSHA Safety and Health Standards, General Industry,” (29 CFR 1910), 

Occupational Safety and Health Administration, OSHA 2206 (Revised, January 

1976). 

 16.6 “Safety in Academic Chemistry Laboratories,” American Chemical Society, 

 Committee on Chemical Safety, 3rd Edition, 1979. 

17.0 Tables, diagrams, and validation data 

See Sections 7.0 and 13.0 

18 The definition and purposes below are specific to this method, but have been conformed 

 to common usage as much as possible. 

18.1 Calibration Blank (CB): A volume of reagent water in the same matrix as the 

calibration standards, but without analyte. 

18.2 Calibration Standard (CAL): A solution prepared from the primary dilution 

standard solution or stock standard solutions. The CAL solutions are used to 

calibrate the instrument response with respect to analyte concentration. 

18.3 Clean Water Act (CWA): An act to provide for water pollution control in the 

Public Health Services of the Federal Security Agency and in the Federal Works 

Agency and for other purposes as specified in the Federal Water Pollution 

Control Act. 

18.4 Chemical Abstracts Service Registry Number (CASRN): The largest 

substance identification system in existence. When a chemical substance, newly 

encountered in the literature, is processed by CAS, its molecular structure 

diagram, systematic chemical name, molecular formula, and other identifying 

information are added to the Registry and it is assigned a unique CAS Registry 

Number. 

18.5 Comprehensive Environmental Resource Compensation Liability Act 

(CERCLA): The 1980 Superfund statute established liability to the U.S. 
 

Page 21 of 23 

Government for damage to natural resources over which the U.S. has sovereign 

rights and requires the President to designate Federal officials to act as trustees 

for natural resources. 

18.6 Deionized Water (DI Water): The vast majority of dissolved impurities in 

modern water supplies are ions such as calcium, sodium, chlorides, etc. The 

deionization process removes ions from water via ion exchange. 

18.7 Environmental Protection Agency (EPA): The mission of the Environmental 

Protection Agency is to protect human health and the environment. 

18.8 Instrument Precision Check (IPC): Also known as a Continuing Calibration 

Verification (CCV) used to evaluate the performance of the instrument 

throughout the analysis. 

18.9 Linear Calibration Range (LCR): The concentration range over, which the 

instrument response is linear. 

18.10 Laboratory Reagent Blank (LRB): An aliquot of reagent water or other blank 

matrices that is digested exactly as a sample including exposure to all glassware, 

equipment, and reagents that are used with other samples. The LRB is used to 

determine if method analytes or other interferences are present in the laboratory 

environment, the reagents, or other apparatus. 

18.11 Method Detection Limit (MDL): The EPA defines MDL as “the minimum 

concentration that can be determined with 99% confidence that the true 

concentration is greater than zero.” This procedure is outlined in 40 CFR 136. 

Prepare a solution of the analyte that is one to five times the estimated detection. 

Test this solution seven or more times, then determine the standard deviation of 

the data set. The method detection limit is calculated according to the formula: 

MDL = Student’s t value x the standard deviation. 

18.12 Matrix Spike (MS): Also known as a Laboratory Spiked Blank (LSB). An 

aliquot of reagent water or other blank matrices to which known quantities of the 

method analytes are added in the laboratory. The MS is analyzed exactly like a 

sample, and its purpose is to determine whether the methodology is in control, 

and whether the laboratory is capable of making accurate and precise 

measurements. 

18.13 Matrix Spike Duplicate (MSD): Also known as a Laboratory Spiked Sample 

Matrix (LSM). An aliquot of an environmental sample to which known 

quantities of the method analytes are added in the laboratory. The MSD is 

analyzed exactly like a sample, and its purpose is to determine whether the 

sample matrix contributes bias to the analytical results. 

18.14 Material Safety Data Sheets (MSDS): Written information provided by 

vendors concerning a chemical’s toxicity, health hazards, physical properties, 

fire, and reactivity data including storage, spill, and handling precautions. 
 

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18.15 National Institute of Standards and Technology (NIST): Founded in 1901, 

NIST is a non-regulatory federal agency within the U.S. Commerce Department's 

Technology Administration. NIST's mission is to develop and promote 

measurement, standards, and technology to enhance productivity, facilitate trade, 

and improve the quality of life. 

18.16 Occupational Safety and Health Administration (OSHA): OSHA's mission is 

to assure the safety and health of America's workers by setting and enforcing 

standards; providing training, outreach, and education; establishing partnerships; 

and encouraging continual improvement in workplace safety and health. 

18.17 Quality Control Sample (QCS): Also known as a Laboratory Control Sample 

(LCS). A solution of method analytes of known concentrations that are used to 

verify stock standard solutions or spike an aliquot of MS or MSD. The QCS is 

obtained from a source external to the laboratory and different from the source of 

the calibration standards. It is used to check laboratory performance with 

externally prepared test materials. 

18.18 Resource Conservation and Recovery Act (RCRA): RCRA gave EPA the 

authority to control hazardous waste from the "cradle-to-grave." This includes 

the generation, transportation, treatment, storage, and disposal of hazardous 

waste. RCRA also set forth a framework for the management of non-hazardous 

wastes. 

18.19 Safe Water Drinking Act (SWDA): The Office of Ground Water and Drinking 

Water (OGWDW), together with states, tribes, and its many partners, protects 

public health by ensuring safe drinking water and protecting ground water. 

OGWDW, along with EPA's ten regional drinking water programs, oversees 

implementation of the Safe Drinking Water Act, which is the national law 

safeguarding tap water in America. 

18.20 Stock Standard Solution (SSS): A concentrated solution containing one or 

more method analytes prepared in the laboratory using reference materials or 

purchased from a reputable commercial source. 
 

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19.0 Consumables used for this method. 

P/N Description Sales unit Estimated consumption 

CUP-EASY-02 SAMPLE CUPS 2.0 ml Pk/500 500 tests 

E/F25 FILTERS - SAMPLE PROBE CLEANER Pk/25 1 pk per month 

E/R18 REAGENT BOTTLES Pk/18 1 pk per 12 months 

E/RZ24 REACTION CUVETTES Pk/100 2400 tests 

E/T25 STOPPER - REAGENT BOTTLES Pk/25 1 pk per month 

E/K01 TUBE KIT EA 1 yearly 

E/K02 PROBES KIT EA 1 yearly 

E/LA01 SOURCE LAMP ASSEMBLY EA 1 yearly 

E/WT2X4-01 WASTE LINE TUBE meter 5m per year 

E/FC-10 EASYCHEM 10MM FLOWCELL EA 1 yearly