2005 Sampling and Analysis
Protocol for Ontario Regulation 267/03 Made under the Nutrient
Management Act, 2002
|Precision|| Method Linearity/Working Range
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.
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.
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 - xo)2/(n-1)]
where: xi =the analytical results in the final method reporting units for the eight replicate aliquots (i = 1 to 8)
xo = 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 )i2/(2n)]
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.
|Number of Replicates||Degree of Freedom (n-1)||t(n-1)|
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.
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
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.
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.
The following are recommended laboratory quality procedures:
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.
|Analyte||Instrument Control||Run Control|
| Accuracy/ Recovery
| Replicate Analysis
(Sample # )
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.
The basis for determining the acceptability of laboratory data should include the following:
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 (greater than or equal to 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.
|Creation Date:||12 August 2005|
|Last Reviewed:||12 August 2005|