RB/T 208-2016 Comparative test for internal quality control in chemical laboratories RB/T208-2016 |tt||Standard compression package decompression password: www.bzxz.net
This standard specifies the general requirements for internal quality control by comparative tests in chemical laboratories. This standard is applicable to internal quality control and test quality evaluation by comparative tests in chemical testing laboratories. Laboratories in other testing fields and disciplines can also use it as a reference.

ICS03.120.00
Certification and Accreditation Industry Standard of the People's Republic of China RB/T208—2016
Internal Quality Control of Chemical Laboratory-Comparison Test
Internal Quality Control of Chemical Laboratory-Comparison Test2016-12-01Issued
Certification and Accreditation Administration of the People's Republic of China Quality Management
Implementation on 2017-06-01
This standard was drafted in accordance with the rules given in GB/T1.1—2009. This standard was proposed and managed by the Certification and Accreditation Administration of the People's Republic of China. RB/T208—2016
Drafting units of this standard: Shandong Exit-Entry Inspection and Quarantine Bureau of the People's Republic of China, Qingdao Institute of Food and Drug Inspection, Qingdao Huace Testing Technology Co., Ltd., Noan Testing Services (Qingdao) Co., Ltd., SGS-CSTC Standards Technical Services Co., Ltd. The main drafters of this standard are: Wang Manxia, ​​Lei Zhiwen, He Fei, Ma Weixing, Liu Peihai, Xu Meiling, Cao Wenqing, Wu Qiangou, Liu Xingmin, Fu Meng and Dai Jianhua.
1 Scope
Internal quality control of chemical laboratories
Comparative test
RB/T208—2016
This standard specifies the management requirements, steps and technical requirements and result utilization of chemical laboratories for internal quality control using comparative tests.
This standard is applicable to chemical testing laboratories using comparative tests for internal quality control and test quality evaluation. Laboratories in other testing fields and disciplines can also refer to it.
2 Normative references
The following documents are indispensable for the application of this document. For all dated references, only the dated version applies to this document. For all undated references, the latest version (including all amendments) applies to this document. GB/T19000—2008 Fundamentals and vocabulary of quality management systems GB/T20000.1 Guide to standardization work Part 1: General terms for standardization and related activities GB/T27025 General requirements for the competence of testing and calibration laboratories 3 Terms and definitions
The terms and definitions defined in GB/T27025 and GB/T20000.1 and the following terms and definitions apply to this document. 3.1
Quality control
quality control
Part of quality management, dedicated to meeting quality requirements. [GB/T19000—2008, definition 3.2.10] 3.2
Comparison test
comparison test
Organization, implementation and evaluation of tests on the same or similar test objects by setting up two or more experimental groups according to pre-specified conditions.
4 Management requirements
4.1 The laboratory shall formulate a comparative test plan for internal quality control according to the needs of the annual quality control plan. 4.2 The comparative test plan used by the laboratory for internal quality control shall clearly specify the test items, comparison form, participants, reservation date, result evaluation criteria, and handling requirements for unsatisfactory results of each comparative test. 4.3 When conducting comparative tests, the laboratory shall take necessary measures to prevent fraud, result collusion or result correction. 4.4 After the comparative test is completed, the laboratory shall summarize, analyze and evaluate the results of the comparative test and form a comparative test report. 4.5 The laboratory shall conduct a cause analysis for the problems encountered in the comparative test and take corrective measures, preventive measures or corresponding improvement measures based on their impact on the test results issued by the laboratory. 1
RB/T208—2016
5 Steps and technical requirements
5.1 Form and content of comparison test
5.1.1 Personnel comparison
Personnel comparison test refers to a test in which different test personnel test the same sample under the same environmental conditions, using the same test method, the same test equipment and facilities. When a test can be performed by multiple people, the laboratory can use personnel comparison test to conduct internal quality control. By arranging two or more representative people at different levels to carry out comparison tests, the ability level of the test personnel can be assessed, and whether the test personnel operate correctly and skillfully can be judged, so as to evaluate the impact of personnel on the accuracy, stability and reliability of laboratory test results. As an internal quality control method, personnel comparison test is preferably applied to the following situations: projects that rely more on subjective judgment of testers, such as sensory and tasting items in food; a) employees in training and new employees; c) key control points or key control links in the testing process; d) samples with high operating difficulty or test items with test results near the critical value, newly installed equipment, newly tested test items; method comparison; method comparison test refers to the use of different test methods by the same testers under the same environmental conditions. Tests in which the same sample is tested by different methods
When a test item can be operated by multiple methods, the laboratory can use the method comparison test to conduct internal quality control to determine whether the standard or method followed by the test is correctly understood and strictly implemented to evaluate the impact of the test method on the accuracy, stability and reliability of the laboratory test results
As an internal quality control means, the method comparison test is preferably applicable to the following situations a) New standards or new methods that have just been implemented;
b) New technologies, new methods and new methods developed; existing projects with multiple inspection standards or methods. c
5.1.3 Instrument comparison
Instrument comparison test refers to the test in which the same sample is tested by the same test personnel using different instruments and equipment under the same environmental conditions, using the same test method. When a test is operated by multiple equipment, the laboratory can use the equipment comparison test to conduct internal quality control to determine whether the equipment that affects the measurement accuracy and effectiveness meets the measurement traceability requirements, and to evaluate the impact of the instrument and equipment on the accuracy, stability and reliability of the laboratory test results. As an internal quality control method, equipment comparison test is preferably applied to the following situations: a) newly installed equipment;
repaired equipment;
equipment whose test results appear near the critical value. c
5.1.4 Retesting of retained samples
Retesting of retained samples refers to the test in which the same test personnel retest the samples that have been tested during the storage period of the retained samples under the same environmental conditions as much as possible, using the same test methods, the same test equipment and facilities. RB/T208—2016
The laboratory re-measures the retained samples and compares and analyzes the differences between the last test results and the current test results to find out the impact of accidental factors on the accuracy, stability and reliability of the laboratory test results. As an internal quality control method, retesting of retained samples can be used in the following situations: a) verify the accuracy of the test results;
verify the repeatability of the test results;
c) monitor the characteristics of retained samples.
Other forms
There are many other forms of comparison for laboratory internal comparison tests. There are many factors that affect the test results in chemical laboratories. Different factors correspond to different comparison forms. Usually, a single-factor comparison test is used, that is, a comparison test only examines one main test factor, such as: comparison of environmental conditions (temperature and humidity, etc.) of different laboratories, comparison of reagents, instruments or consumables of different batches or brands, etc. 5.2 Design of comparison test plan
5.2.1 Personnel involved in the design of the comparison test plan should include technical personnel who are familiar with laboratory quality management, test methods and statistics. If necessary, a comparison test technical team can be established to be responsible for the design of the plan, supervision of its implementation and guidance of the comparison process. 5.2.2 The contents of the comparison test plan generally include but are not limited to # aspects a) Purpose; b) Start time and end time; comparison form, test items and equipment, test method; d) Description of the samples used, such as uniformity and stability; e) Test technical requirements, such as repetition (#); f) Record requirements; Evaluation conclusions of participants; Distribution form and disposal requirements, etc.; Number of measurements; g) Evaluation method and result judgment criteria; h) Disposal requirements for unsatisfactory results and other matters that require special attention.
5.3Sample management for comparative test
Sample requirements
Samples used for comparative test should meet the following conditions: a)
Samples should be sufficiently uniform and stable. The number of samples stored under appropriate conditions should be able to meet the requirements of all test items. If necessary, samples for additional tests should be reserved; b)
Sample preparation should have a documented processing procedure, and samples should be confirmed before use. c
2Sample preparation/preparation
Samples for comparative test can be divided into negative samples and positive samples. For positive samples, they can be obtained through the following ways: a) Self-made samples
With the understanding of the sample preparation method, the laboratory can use its own instruments and equipment to prepare simple samples, or cooperate in preparation. Regardless of the preparation method adopted, the prepared samples should be sampled and tested to evaluate their uniformity and stability to confirm that they can be used for comparative tests.
b) Positive retention samples
For positive samples encountered during routine testing, you can choose whether to retain the sample3
RB/T208—2016
and use it for comparative tests according to the nature of the sample and the target test item.
When using such samples for comparative tests, it should be confirmed that such samples have been in a properly preserved state that meets the requirements since the last test, and the composition and content of the analyte therein should be confirmed to have not changed through effective means such as expert evaluation or sample evaluation. ) Standard samples or quality control samples
Certified reference materials, comparison samples remaining from inter-laboratory comparisons or proficiency testing activities, and laboratory quality control samples usually have good homogeneity and have specified reference values ​​and measurement uncertainties. Therefore, such samples can be used as comparative test samples as long as they are confirmed to have been in a properly preserved state that meets the requirements. d) Spiked samples
Add appropriate concentrations of standard materials to a series of weighed samples at the same time. The addition process should be independent of the test process. The person who adds should be an experienced technician. The concentration of addition should be suitable for the day of the comparative test. The volume of addition should be accurate and small. The added sample should be placed for a certain period of time under appropriate conditions. 5.3.3 Disposal of samples
5.3.3.1 After the sample is prepared or prepared, the sample should be packaged in a way that will not affect the test results, and the sample should be distributed in the way specified in the comparative test plan or the requirements of the laboratory's relevant quality control procedure documents. 5.3.3.2 If the disposal of the sample will affect the test results, it should be clearly stated in the comparative test plan implementation plan, or the test personnel should be reminded of it in the form of special instructions. After receiving the sample, the test personnel should keep it properly as required. 5.3.3.3 The unique identification and inspection status identification of the sample should comply with the provisions of GB/T27025. 5.4 Conducting comparative tests
5.4.1 When the laboratory conducts comparative tests for internal quality control, it should confirm that its environmental conditions will not have an adverse effect on the required test quality.
5.4.2 When the laboratory conducts comparative tests for internal quality control, it shall confirm that all equipment used for testing that has a significant impact on the accuracy or validity of the results, including auxiliary measurement equipment (for example, equipment used to measure environmental conditions), has been calibrated and the confidence level of its calibration status has been maintained through effective period verification.
5.4.3 Personnel participating in comparative tests shall conduct tests in accordance with the requirements of the test methods, truthfully record the test results and related information, and submit test reports and original records. The records shall comply with the provisions of GB/T27025. 5.4.4 When unexpected circumstances occur during the test that may affect the statistical analysis of the comparative test results, the person in charge of the comparative test shall promptly analyze various factors, fully coordinate with the test personnel, and make a decision to continue with the original test plan or to modify the original test plan and implement a new plan.
5.5 Evaluation of the results of the comparative test
5.5.1 Statistical evaluation (1 test)
For any form of comparative test, when the number of parallel measurements n for each group of tests is large (n≥6), the two groups of comparative data can be first subjected to variance analysis according to step "a) F test" to determine whether there is a significant difference in the precision of the two means. If there is no significant difference, it means that the two groups of measurement results have equal precision, and continue to evaluate the comparative test results according to step "b) t test". a) F test
The F test value is calculated according to formula (1):
Wherein:
5largest——the value with the larger standard deviation in the two sets of data;4
·（1）
the value with the smaller standard deviation in the two sets of data
If F calculated>F table, it means that there is a significant difference in the precision of the two sets of data and the comparison result is unsatisfactory.RB/T208—2016
If F calculated≤F table·it means that there is no significant difference in the precision of the two sets of data. The test results are evaluated by comparing them according to the 1 test method. b) t-test
The t-test value is calculated according to formula (2):
In the formula:
The average value of the results of the first group of measurements;
The average value of the results of the second group of measurements;
Vni+n2
The combined experimental standard deviation of the two groups of equal-precision measurement results;The number of parallel measurements of the first group of measurements;
The number of parallel measurements of the second group of measurements.
Among them, the combined experimental standard deviation s of the two groups of equal-precision measurement results is calculated according to formula (3):(n-1)si+(n2-1)s
n+nz-2
（2）
（3）
If t>tn1+2-2, it is considered that there is a significant difference between the measurement result and the standard value, indicating that the comparison test result is unsatisfactory; if tt. 1 + cell - 3, it is considered that there is no significant difference between the measurement result and the standard value, indicating that the comparison test result is satisfactory. 5.5.2 Personnel comparison
When the method specifies the allowable difference, the measurement value of the party with higher accuracy for personnel comparison is used as the reference value, and the comparison test result is evaluated according to formula (4):
X100≤D%
Where:
Measured value of the comparison party;
Measured value of the reference party;
D%—allowable difference specified by the method, expressed in percentage (%). If formula (4) is satisfied, it indicates that the comparison test result is satisfactory; if formula (4) is not satisfied, it indicates that the comparison test result is unsatisfactory. · (4) When the
method does not specify the allowable difference, the two parties conducting the personnel comparison shall evaluate the measurement uncertainty of the measured value, and the comparison test result shall be evaluated according to formula (5):
In the formula:
The measured value of the personnel of one party of the comparison;
The measured value of the personnel of the other party;
[yr-|sVU+U
Ui—— The measurement uncertainty of the measured value y of the personnel of one party of the comparison, k=2U—— The measurement uncertainty of the measured value y2 of the personnel of the other party of the comparison, k=2. If formula (5) is satisfied, it indicates that the comparison test result is satisfactory; if formula (5) is not satisfied, it indicates that the comparison test result is unsatisfactory. 5.5.3 Method comparison
The method comparison test results are evaluated according to formula (6): [yi-y2l≤VUi+U
.... (5)
(6)
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Wherein:
Measurement value of the first method;
Measurement value of the second method;
U1——Measurement uncertainty of the measurement value y, measured by the first method, k=2; U1——Measurement uncertainty of the measurement value y2 measured by the second method, k=2. If formula (6) is satisfied, it indicates that the comparison test results are satisfactory; if formula (6) is not satisfied, it indicates that the comparison test results are unsatisfactory. 5.5.4 Equipment comparison
5.5.4.1 Comparison between two equipments
When one equipment is compared with another equipment of high accuracy level, the measured value of the equipment of high accuracy level is taken as the reference value, and the comparison test result is evaluated according to formula (7): [-U+a
Wherein: bzxz.net
Measured value of the comparison party;
Measured value of the reference party;
U,——Measurement uncertainty of the measured value of the comparison party, k-2; U. Measurement uncertainty of the measured value of the reference party, k-2. If formula (7) is satisfied, it indicates that the comparison test result is satisfactory; if formula (7) is not satisfied, it indicates that the comparison test result is unsatisfactory. 5.5.4.2 Comparison of multiple devices
When multiple devices with the same accuracy level are compared, the comparison test results are evaluated according to formula (8): lyi-yls
Wherein:
the measured value of the th device;
the average value of the measured values ​​of multiple devices with the same accuracy level; the number of devices participating in the comparison;
the measurement uncertainty of multiple devices with the same accuracy level participating in the comparison, k=2. If formula (8) is satisfied, it indicates that the comparison test results are satisfactory; if formula (8) is not satisfied, it indicates that the comparison test results are unsatisfactory. 5.5.5 Re-test with retained samples
When re-testing with retained samples, the comparison test results are determined according to formula (9): 1yi-y2≤V2U
Wherein:
is the first measured value of the sample;
is the measured value of the retained sample re-tested; the measurement uncertainty of the measured value is 2. If formula (9) is satisfied, it indicates that the comparison test results are satisfactory; if formula (9) is not satisfied, it indicates that the comparison test results are unsatisfactory. 5.6 Comparison test report
The content of the comparison test result report generally includes (but is not limited to) the following aspects: a) Month;
· (9)
Start time and end time;
Comparison form, test items, instruments and equipment, test methods, participants, etc.; RB/T208-2016
Description of the samples used, such as: uniformity and stability evaluation conclusions, distribution form and disposal requirements, etc.; original test records;
Result evaluation criteria and evaluation conclusions;
When the results are abnormal, it should also include cause analysis and rectification measures requirements; evaluators, reviewers and approvers.
If necessary, the comparison test result report should also include the consistency of the test result data, the various factors that may affect the test results, the analysis of abnormal test result data, etc., and explore the possible causes of the abnormality, and put forward suggestions for improvement when necessary. 6 Utilization of results
The evaluation results of the comparison test are divided into satisfactory and unsatisfactory. According to work needs, the laboratory may add provisions for critical criterion for comparison test result evaluation.
When the comparison test results are satisfactory, it is considered that the laboratory's monitoring of the test results is effective and meets the requirements of internal quality control. When the comparison test results are suspicious, the laboratory should analyze the reasons for the suspicion as soon as possible, carry out effective improvement activities, and modify the operational documents when necessary.
When the comparison test results are unsatisfactory, the laboratory should take planned measures to correct the problems and prevent reporting of erroneous results.
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