A New Design for Reference Values Assignment in Proficiency Testing for Fat and Crude Protein in Raw Milk for a Limited Number of Participants
Abstract
:1. Introduction
2. Materials and Methods
2.1. Planning, Preparation and Distribution of the PT Items
2.2. Reference Value Assignment
2.2.1. Experimental Design
2.2.2. Data Source
2.2.3. Chemical Analysis for the Assignment of the Reference Value
- is the reference value of the PT item,
- is the reference value of the CRM,
- is the mean of the results from the n replicas of the PT item and
- is the mean of the results from the n replicas of the CRM.
2.2.4. Standard Uncertainty of the Assigned Value
- is the standard uncertainty of the assayed PT item. For this source of uncertainty, and in order to facilitate the comparison between rounds, a common uncertainty for all the PT items analyzed in a round was estimated:
- is the standard uncertainty of the CRM assay, which is obtained as follows: If is the result obtained from session l and replica m, let n be the number of sessions and q the number of replicas in one session, then
- is the CRM standard uncertainty, which is obtained based on the expanded uncertainty as set out in the CRM certificate, where and is the declared coverage factor.
2.3. Criteria to Evaluate the Performance of the Participants
2.3.1. Mid-Infrared Spectroscopy (MIR) (Fat and Crude Protein)
2.3.2. The Röse Gottlieb Method (Fat)
- is the standard deviation of the reproducibility of the analytical method,
- is the standard deviation of the repeatability of the analytical method and
- m is the number of replicas performed by each laboratory participating in the PT.
2.3.3. The Gerber Method (Fat)
2.3.4. The Kjeldahl Method (Crude Protein)
3. Results
3.1. Reference Values Assigned to the PT Items
3.1.1. Combined Standard Uncertainty of the Assigned Values
3.1.2. Uncertainty Components of the Assigned Values
3.2. Criteria for the Evaluation of the Participants’ Performance
3.2.1. Instrumental MIR Method (Fat and Crude Protein)
3.2.2. The Röse Gottlieb Method (to Determine Fat Content)
3.2.3. The Gerber Method (to Determine Fat Content)
3.2.4. The Kjeldahl Method (to Determine the Crude Protein Content)
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
PT Code | (g/100 g Milk) | CRM Assigned Value (g/100 g Milk) | Bias (g/100 g Milk) |
---|---|---|---|
EA GP LC 1701 | 3.475 | 3.477 | −0.002 |
EA GP LC 1702 | 3.524 | 3.525 | −0.001 |
EA GP LC 1801 | 3.485 | 3.474 | 0.011 |
EA GP LC 1802 | 3.482 | 3.474 | 0.008 |
EA GP LC 1901 | 3.511 | 3.498 | 0.013 |
EA GP LC 1902 | 3.478 | 3.498 | −0.020 |
EA GP LC 2001 | 3.590 | 3.594 | −0.004 |
EA GP LC 2101 | 3.621 | 3.614 | 0.007 |
PT Code | (g/100 g Milk) | CRM Assigned Value (g/100 g Milk) | Bias (g/100 g Milk) |
---|---|---|---|
EA GP LC 1701 | 3.386 | 3.392 | −0.006 |
EA GP LC 1702 | 3.481 | 3.473 | 0.008 |
EA GP LC 1801 | 3.503 | 3.502 | 0.001 |
EA GP LC 1802 | 3.502 | 3.502 | 0.000 |
EA GP LC 1901 | 3.573 | 3.563 | 0.010 |
EA GP LC 1902 | 3.546 | 3.563 | −0.017 |
EA GP LC 2001 | 3.452 | 3.431 | 0.021 |
EA GP LC 2101 | 3.391 | 3.368 | 0.023 |
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Session 1 | Session 2 | Session 3 | ||||||
---|---|---|---|---|---|---|---|---|
PT Item | Vial | Replica | PT Item | Vial | Replica | PT Item | Vial | Replica |
1 | 1 | 1 | 1 | 2 | 1 | 1 | 3 | 1 |
2 | 1 | 1 | 2 | 2 | 1 | 2 | 3 | 1 |
3 | 1 | 1 | 3 | 2 | 1 | 3 | 3 | 1 |
4 | 1 | 1 | 4 | 2 | 1 | 4 | 3 | 1 |
5 | 1 | 1 | 5 | 2 | 1 | 5 | 3 | 1 |
6 | 1 | 1 | 6 | 2 | 1 | 6 | 3 | 1 |
CRM | 1 | CRM | 1 | CRM | 1 | |||
2 | 2 |
PT Code | Date | CRM Code | CRM Producer |
---|---|---|---|
EA GP LC 1701 | April 2017 | m-0135 | muva (Kempten, Germany) |
EA GP LC 1702 | October 2017 | m-0138 | |
EA GP LC 1801 | May 2018 | m-0140 | |
EA GP LC 1802 | November 2018 | m-0140 | |
EA GP LC 1901 | June 2019 | m-0143 | |
EA GP LC 1902 | October 2019 | m-0143 | |
EA GP LC 2001 | October 2020 | RM CP L MR M 84 | DRRR (Kempten, Germany) |
EA GP LC 2101 | October 2021 | RM CP L MR M 93 |
PT Identification Code | Measurand | Standard Uncertainty in the CRM Certificate (g/100 g Milk) | Standard Uncertainty of the CRM Analysis (g/100 g Milk) | Standard Uncertainty of the PT Item (g/100 g Milk) | Combined Standard Uncertainty of the Assigned Value (g/100 g Milk) |
---|---|---|---|---|---|
EA GP LC 1701 | Fat | 0.0070 | 0.0090 | 0.0102 | 0.0153 |
EA GP LC 1702 | 0.0050 | 0.0020 | 0.0072 | 0.0090 | |
EA GP LC 1801 | 0.0080 | 0.0010 | 0.0083 | 0.0116 | |
EA GP LC 1802 | 0.0080 | 0.0040 | 0.0075 | 0.0117 | |
EA GP LC 1901 | 0.0180 | 0.0030 | 0.0112 | 0.0214 | |
EA GP LC 1902 | 0.0180 | 0.0040 | 0.0059 | 0.0194 | |
EA GP LC 2001 | 0.0090 | 0.0040 | 0.0036 | 0.0105 | |
EA GP LC 2101 | 0.0110 | 0.0030 | 0.0063 | 0.0130 | |
EA GP LC 1701 | Crude protein | 0.0050 | 0.0071 | 0.0079 | 0.0117 |
EA GP LC 1702 | 0.0060 | 0.0024 | 0.0029 | 0.0071 | |
EA GP LC 1801 | 0.0130 | 0.0048 | 0.0034 | 0.0143 | |
EA GP LC 1802 | 0.0130 | 0.0080 | 0.0031 | 0.0156 | |
EA GP LC 1901 | 0.0110 | 0.0051 | 0.0046 | 0.0130 | |
EA GP LC 1902 | 0.0110 | 0.0032 | 0.0024 | 0.0117 | |
EA GP LC 2001 | 0.0210 | 0.0025 | 0.0015 | 0.0212 | |
EA GP LC 2101 | 0.0110 | 0.0020 | 0.0026 | 0.0115 |
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Poo, S.; Palma, M.; Muñoz, O. A New Design for Reference Values Assignment in Proficiency Testing for Fat and Crude Protein in Raw Milk for a Limited Number of Participants. Foods 2024, 13, 2693. https://doi.org/10.3390/foods13172693
Poo S, Palma M, Muñoz O. A New Design for Reference Values Assignment in Proficiency Testing for Fat and Crude Protein in Raw Milk for a Limited Number of Participants. Foods. 2024; 13(17):2693. https://doi.org/10.3390/foods13172693
Chicago/Turabian StylePoo, Susan, Miguel Palma, and Ociel Muñoz. 2024. "A New Design for Reference Values Assignment in Proficiency Testing for Fat and Crude Protein in Raw Milk for a Limited Number of Participants" Foods 13, no. 17: 2693. https://doi.org/10.3390/foods13172693