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Proficiency testing (PT)
Proficiency tests in the RL are organized in accordance with the requirements of the standard ISO/IEC 17043:2023 "Conformity assessment - General requirements for the competence of proficiency testing providers".
All laboratories (industrial, official, scientific, etc.) involved in the analysis of milk and/or dairy products can participate in the proficiency testing.
The RL organizes proficiency tests for cow's milk (fresh, pasteurized and sterilized), and sheep's and goat's fresh milk, as well as for dairy products (cheese, cream, yoghurt and butter). The components of milk and dairy products covered by the proficiency testing are listed below the table with the Delivery schedule of PT samples. One proficiency testing set includes 3 milk samples (10 samples are delivered for the IBC component) and 2 dairy product samples.
Participants in the proficiency testing can use any analytical method they use in their laboratory. The number of repetitions of analysis of each sample should be equal to the number of repetitions that the laboratory routinely performs in its practice, but not more than 5. Participants should enter their results in the appropriate forms that can be downloaded below the table Delivery schedule of PT samples and send them by e-mail to rlm@agr.hr.
RL treats all data provided by the participant as a secret. The results of the analysis of samples of each participant in the proficiency testing report are listed under a specific laboratory code to ensure data confidentiality.
The reference values (assigned values) of the components in the proficiency testing are determined based on the results of one laboratory (RL) as required by the standard ISO 13528:2022, point 7.5 or based on a consensus value from the results of all participants as required by the standard ISO 13528:2022, point 7.7.
The assessment of the participant's performance is performed by calculating the values of z and/or z' and En (if the participant submits the expanded measurement uncertainties of the analysis results, k=2). The standard deviation for proficiency assessment (σpt) is determined according to the requirements of the standard ISO 13528:2022, points 8.3 and 8.6, i.e. it is based on experience from previous rounds of proficiency testing or is calculated using robust consensus statistics of the results of participants in the current round of proficiency testing.
Notification of the analysis deadline and the deadline for submission of participant results for each term from the table Delivery schedule of PT samples is sent to registered participants by e-mail a few days before the delivery date.
At the request of the relevant Ministry of the Republic of Croatia, the RL sends an annual report on the results of official laboratories of the Republic of Croatia that participated in proficiency testing organized by the RL.
Samples for proficiency testing can be ordered in the form of an annual order or at least 7 days before the planned delivery, by sending an e-mail with the order form to rlm@agr.hr. The order form must contain: company name, address and company OIB, name of contact person, method of sample delivery (personal collection or delivery by express mail), DHL number (if delivery is carried out by express mail).
Prices for participation in proficiency testing, as well as all other information, can be obtained by sending an inquiry to e-mail: rlm@agr.hr.
Handling of proficiency testing samples
Storage and sample handling are prescribed in the documents " Instructions for users on the handling and preparation of milk samples for PT " and " Instructions for users on the handling and preparation of cheese, cream, yoghurt and butter samples for PT ", which can be downloaded below the table Delivery schedule of PT samples.
Transport of proficiency testing samples
Users collect proficiency testing samples in person at the RL and transport them in transport coolers with ice packs or they are delivered to users by express mail in appropriate packaging (styrofoam boxes) with ice packs or dry ice.
Delivery schedule of PT samples in 2025
| Cow milk | Goat milk | Sheep milk |
| 15. - 16. January (1) | - | - |
| 12. - 13. February (2+6) | - | - |
| 05. - 06. March (1+3) | - | - |
| 03. - 04. April (5) | 10. – 11. April (4+8) | - |
| 07. - 08. May (1) | - | 21. - 22. May (4+8) |
| - | 11. - 12. June (4) | - |
| 02. - 03. July (1) | - | - |
| - | - | 27. - 28. August (4+5) |
| 10. - 11. September (1) | 17. - 18. September (4+5) | - |
| 08. - 09. October (6) | - | - |
| 12. - 13. November (1) | - | - |
| Pasterised milk | Sterilised milk | Cheese, Cream, Yoghurt, Butter |
| 22. - 23. October (7) | 03 - 04. December (7) | 26. - 27. November (9) |
| - | - | - |
basic chemical composition of milk: milk fat, protein, lactose, dry matter
(1) basic chemical composition, somatic cell count, individual bacterial count-IBC (flow cytometry), freezing point
(2) acidity (pH, °SH, alcohol test)
(3) total bacterial count-CFU (aerobic mesophilic bacteria) (horizontal method, 30°C, 72h)
(4) basic chemical composition, individual bacterial count-IBC (flow cytometry)
(5) urea
(6) detection of antibiotics (β-lactam + tetracycline) (qualitative), density
(7) basic chemical composition
(8) freezing point
(9) cheese: milk fat, protein, dry matter, pH, NaCl;
cream: milk fat, protein, dry matter
yogurt: milk fat, protein, dry matter, pH, lactic acid
butter: milk fat, solids-non-fat, water
Documents
Result sheets for PT- Excel .xlsx format
Results of PT fat, protein, lactose and dry matter in milk | Download
Results of PT freezing point of milk | Download
Results of PT IBC Flow citometry - milk | Download
Results of PT pH, SH and alcohol test of milk | Download
Results of PT presence of antibiotics in milk | Download
Results of PT somatic cells count in milk | Download
Results of PT total count of aerobic mesofilic (AM) bacteria in milk | Download
Results of PT urea in milk | Download
Results of PT dry matter, fat, protein, NaCl and pH in CHEESE | Download
Results of PT for dry matter, fat and protein in CREAM| Download
Results of PT for dry matter, fat, protein, lactic acid and pH in YOGHURT | Download
Results of PT fat, water and non-fat dry matter in BUTTER | Download
Instructions for users on the handling and preparation of milk samples for PT | Download
Instructions for users on the handling and preparation of cheese, cream, yoghurt and butter samples for PT | Download
