December 2003 Sampling and Analysis Protocol for Ontario Regulation 267/03 Made under the Nutrient Management Act, 2002

Part 3 - Laboratory Analysis

Table of Contents

  1. Laboratory Quality Management
  2. Laboratory Method
  3. Method Detection Limit (MDL)
  4. Reporting Detection Limit (RDL)
  5. Precision
  6. Accuracy and Recovery
  7. Method Linearity
  8. Recommended Laboratory QC/QA Procedures
  9. Data Acceptance Criteria
  10. Data Reporting

3.1 Laboratory Quality Management

Laboratories participating in the analysis of soil and land applied materials for the Nutrient Management Act (NMA) are required to have a sound quality management program.

Quality Management (QM) is that aspect of the over-all management function that determines and implements the quality policy. International Standard ISO/IEC 17025 outlines management and technical requirements for implementing a laboratory quality management system.

Laboratory Accreditation Requirement

Laboratories analyzing soil for available nutrients as required by the Nutrient Management Act (NMA) must be accredited for the applicable nutrient tests by the Ontario Ministry of Agriculture and Food under the OMAF Agronomic Test Accreditation Program.

Laboratories analyzing soil and land applied materials for nutrients as required by the NMA must be accredited by the Ontario Ministry of Agriculture and Food under the OMAF Agronomic Test Accreditation Program, or by a body which accredits laboratories to ISO/IEC 17025 standards for analytical laboratories (e.g. the Standards Council of Canada through Canadian Association of Environmental Analytical Laboratories).

Laboratories analyzing soil and land applied materials for metals and E. coli as required by the NMA must be accredited by a body which accredits laboratories to ISO/IEC 17025 standards for analytical laboratories (e.g. the Standards Council of Canada through Canadian Association of Environmental Analytical Laboratories).

3.2 Laboratory Method

All laboratories participating in the analysis of soil and land applied materials for NMA activities must have a formal written method used for the analysis. Bench procedures must be documented in sufficient detail to ensure uniform application and must be readily available to technical staff.

Method Summary

A summary of the method used for such analysis may be required by the Ministry to review data. It will assist the Ministry in evaluating if the laboratory method/performance data is in compliance with the data quality requirements of this program (Section 4).

A method summary should contain the following information as a minimum:

  • Method Used, e.g., EPA 5030, MOE/LSB E3394 or your laboratory Reference Method.
  • Method Principle - Brief description of sample preparation and instrumentation.
  • Sample preservation if required.
  • Sample storage temperature.
  • Accreditation (laboratory/method) - Type of accreditation and name of accrediting body.
  • Method performance characteristics - Provide such information in a tabular form. The example is given in table 3-1.

Table 3.1 Method Performance Characteristics

Analyte MDL
Unit
Accuracy
% Recovery
Precision Method Linearity/Working Range
Unit
Within-Run
% RDS
Between-Run
% RSD
           
           
           
           

Provide the following information:

Accuracy: Material used for accuracy determination, e.g., in-house spiked matrix blank, CRM, other and number of determinations used for this study.

Precision: Material used for precision determination, e.g., in-house spiked matrix blank, CRM, other and number of determinations used for this study.

 3.3 Method Detection Limit (MDL)

The method detection limit is a statistically defined method attribute. Measured results falling at or above this point are interpreted to indicate the presence of an analyte in the sample with a specified probability—usually greater than 99%—and assumes that sources of error in identification or biases in measurement are known and controlled.

Procedure for MDL Determination

Take a minimum of eight aliquots of the sample to be used to calculate the method detection limit and process each through the entire analytical method.

If a blank measurement is required to calculate the measured level of analyte, obtain a separate blank measurement for each sample aliquot analyzed.

Calculate a result (x) for each sample/blank pair.

Calculate the standard deviation (S) of the replicate measurements as follows:

S = √ [(∑ (xi - 0 )2)/(n - 1)]

where:

xi = the analytical results in the final method reporting units for the eight replicate aliquots (i = 1 to 8)

0 = the average of the eight replicate measurements

An alternative is to use historic within run replicate analysis data and calculate the standard deviation (S) of the replicate measurements as follows. This is suggested for soil samples.

S = √ [(∑ (x1 - x2 )i 2)/(2 n)]

where:

x1, x2 = the two replicate results for each of the n replicate pairs (minimum n = 40)

Compute the MDL as follows:

MDL = t( n-1, α = 0.01 ) S

where: t( n-1, α = 0.01 ) is the Student's value appropriate for a 99% confidence level given the degrees of freedom n-1.

S = the standard deviation as determined above.

Table 3.2 Student's t Values at the 99 Per Cent Confidence Level
Number of Replicates Degree of Freedom
(n-1)
t (n-1)
7 6 3.143
8 7 2.998
9 8 2.897
10 9 2.821
11 10 2.764
16 15 2.603
21 20 2.528
26 25 2.485
31 30 2.457
2.369

3.4 Reporting Detection Limit (RDL)

This has been set at 1/10 of the maximum permissible contaminant concentration criteria or laboratory MDL whichever is higher.

The Reporting Detection Limit requires laboratories to achieve Method Detection Limit (MDL) less than or equal to the RDL value.

Laboratories that achieve MDL less than RDL must therefore report results below RDL values.

3.5 Precision

Precision is the degree of agreement among independent measurements of the same quantity under specified conditions.

Both within-run and between-run precision must be established. This can be done by using replicate sample analysis (within-run) and analysis of spiked blank samples, in-house control or certified reference material, if and when available (between-run). Control limits for these should be established and maintained as part of the analytical performance criteria.

It is desirable to determine precision at ≈ 10MDL.

Requirement - The precision requirement for each test is given in Section 4.

3.6 Accuracy and Recovery

Certified reference materials (CRMs), if and when available, should be used to assess laboratory accuracy. Accuracy is the degree of agreement of individual measurements with an accepted reference value. If a CRM of exactly the same type of material as the sample is unavailable, a similar CRM may be used. For example, a CRM of plant tissue or sludge may be used for manure analysis.

For metals, accuracy is based upon the analytical results compared to the listed values of the certified reference material. It is a certified value 20 % allowable error. For this program, certified reference material(s) are identified under each test (Section 4). Other CRMs may be used, provided they produce data within the above allowable range when subjected to the same method principle.

Recovery is the measured value of that portion of an analyte or surrogate added to a sample that is recovered by testing.

The accuracy/recovery requirement for each test is given in Section 4.

Participation in one or more proficiency testing (PT) programs also demonstrates acceptable method performance.

3.7 Method Linearity

The linearity (working range) of the method for each analyte must be established and documented in the method. Linearity is the range over which the analytical system exhibits a linear or other well established relationship between the amount of material introduced into the analytical system and the instrument's response.

No sample result should be reported that is outside the calibration range of the method. If a result is too high, the sample should be diluted. If too low, a larger aliquot (portion) of sample must be analyzed to meet the requirements of the method detection limit.

3.8 Recommended Laboratory QC/QA Procedures

The following are recommended laboratory quality procedures:

Pre-service QC:
  • labware and reagent blanks
  • instrument setup standard
  • reference standard to validate in-house standards
  • certified reference material to validate method recovery
  • instrument detection limits (IDLs) and detector linearity curves
    (minimum of 3 point calibration)
In-service QC:
  • baseline drift blanks
  • standards
  • instrument checks
Run quality QC and QA:
  • method spiked blanks
  • method blanks
  • in-house matrix check material
  • replicate sample (minimum of one set per run of 30 samples)
  • spiked samples, if applicable.

Laboratories should maintain records of data to show that the analytical systems were in control at the time of analysis. The results of these quality control and performance-monitoring checks should be tabulated and summarized for ready retrieval, evaluation and auditing. A sample is shown in Table 3-3.

Table 3.3 Laboratory QC Data

Identify validation standards, in-house spiked matrix blank, CRM’s, etc.

Analyte Instrument Control Run Control
Amount
Injected
(Unit)
Amount Recovered (Unit) Blank (Unit) Accuracy/Recovery (%) Replicate Analysis
(Sample # ) (Unit)
           
           
           

a) Name/identify externally validated standard (s) used to verify calibration or validate in-house standards.

b) Name/identify material used for accuracy/recovery determination, e.g., in-house spiked matrix blank, CRM, other.

3.9 Data Acceptance Criteria

The basis for determining the acceptability of laboratory data should include the following:

  • Method should be consistent with the principle as given under specific test (Section 4) has been applied.
  • The performance characteristics (RDL, accuracy and precision) of a method used for NMA analysis should be within specifications as given under each test (Section 4).
  • The results of all applicable quality control samples should be within the acceptable range. See specific tests (Section 4).
  • The analytical system should be in control at the time of analysis.

3.10 Data Reporting

A laboratory's data-management system should establish and maintain direct links between sample information (such as source, field sample number or code, date and time sampled, tests required), and laboratory information (such as laboratory sample number or code, date and time analyzed, tests performed and identification of the analyst who did the work).

A properly recorded result shall include the test or analyte name or code, the units of measure, the method used for analysis and any qualifying remarks.

The number of digits following a decimal point should not exceed the number of digits after a decimal point appearing in the method detection limit.

Analytical results may be corrected to take into account any positive results of associated method blank for some specific analysis. A method blank result above the method detection limit is normally considered a positive result. The criteria or control limits for blank corrections should be determined by laboratories on the basis of historical data, and these should be documented. Otherwise, data should be reported without correction. If a correction is made, it should be clearly identified and described.

All data should be reported. Data below RDL should have remark as < RDL. Data below MDL should have remark as < MDL.

All data for soil and land applied materials (≥ 1% solid) should be reported on a dry weight basis. Dry matter content should also be reported.

All data for dilute liquid land applied materials (< 1 % solid) should be reported on a volume basis.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 10 December 2003
Last Reviewed: 10 December 2003