Accreditation and Standards

Standards used to design this proficiency test :

• Proficiency test Not accredited, but based in UNE-EN ISO/IEC 17043:2023 General requirements for proficiency testing. Check our accreditation scope.
• UNE-EN ISO/IEC 15328:2015 Statistical methods for use in proficiency testing
• HARMONIZED PROTOCOL FOR THE PROFICIENCY TESTING OF (CHEMICAL) ANALYTICAL LABORATORIES
• SANTE Guide into force: ANALYTICAL QUALITY CONTROL AND METHOD VALIDATION PROCEDURES FOR PESTICIDE RESIDUES ANALYSIS IN FOOD AND FEED
• Quick Polar Pesticides Method (QuPPe) latest version.

Why TestQual proficiency test ?

• 20 years of experience in proficiency test s since TestQual's foundation.
• Customized reports: Global report, individual reports, and option for reports by analyte groups.
• Fortification and quality controls available for participants upon request.
• Distributor network: Conveniently place orders in your local language and without worrying about time differences. participation confidentiality is not compromised.
• We take care of everything so you can focus on the analysis.
• Customer service and quick support on all our channels (email, phone, web).
• Innovation and cost-effectiveness: Constant negotiation of shipping costs and materials to ensure your samples arrive in perfect condition and for the best price.

Proficiency test Information

This proficiency test will consist of a single round, in which a sample will be distributed on the specified date (see calendar). Detailed information about this Proficiency test can be found in the protocol (Calendar, sample quantity, analytes, concentrations, deviation/deviations from target standard). The protocol can be downloaded from the right column of this page.

Intercomparison Calendar

Check the right column of this page, in the "Dates" section.

*These dates are indicative and should always be verified with the dates in the Proficiency test protocol and with the news on the TestQual homepage.
Only registered participants in this proficiency test will receive emails with instructions and confirmation of the definitive distribution date.

Analytes

Ethephon

Ethephon is an organophosphorus pesticide that inhibits plasma cholinesterase in humans (e1). One of its metabolites is phosphonic acid, and it is unstable in alkaline and oxidizing media. (e2), (e3), (e4). Ethephon is a plant growth regulator used for ripening, floral induction, to mention some. Its mode of function is by releasing ethylene, chloride, and phosphate, which are absorbed by the plant, affecting the growth process (e4). This pesticide is moderately toxic orally, dermally, and by inhalation. It is also corrosive and can cause eye irritation, as well as dermal irritation (according to a study in rabbits) and neurotoxic effects (cholinesterase inhibition). (e4), (e5). The MRL for Ethephon can be consulted in Regulation (EU) 2015/399 of the Commission of February 25, 2015, which can be found at this link (EU LEX etefón)

Glyphosate and AMPA

Glyphosate is a wordlwide used herbicide, which has been renewed its at least until 2033 (g5). Glyphosate and other pesticides are mainly used to control weeds that may compete with crops (g1), (g2), thanks to their herbicidal mechanism that kills by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which is necessary for the production of key components and affects the carbon absorption mechanism for plants (g3). Glyphosate has been determined to be toxic to aquatic life with long-lasting effects (g2), and it is an endocrine disruptor that causes oxidative stress due to excess Ca2+, which alters the reproductive functions of male rats (g4). For glyphosate, in its 2019 review of MRLs for this compound and its derivatives, EFSA considered different residue definitions depending on whether crops were genetically modified to tolerate glyphosate. In this study, the main residue definition was considered as Glyphosate for conventional crops and as "sum of glyphosates, AMPA, N-acetyl-glyphosate, and N-acetyl-AMPA, expressed as glyphosate" for crops genetically modified to better tolerate glyphosate (g4). AMPA is the main metabolite of Glyphosate and has been considered by the EFSA even a better marker of glyphosate usage than glyphosate itself (g4).

Nitrates

Nitrates are used as fertilizers in agriculture and during food processing as a possible authorized food additive. They accumulate mainly in the green parts of the plant (n1), especially leafy vegetables were found to have the highest average nitrate levels among all food groups. (n2). Nitrate alone is not toxic; however, its toxicity results from its conversion to nitrite, which can occur, for example, through reduction at different stages of food (processing, storage, contact with saliva, or in the intestinal tract) (n1). The amount of nitrate and nitrite found in horticultural products can be affected by various factors such as storage time and storage conditions (room temperature, refrigerated, or frozen), and the final level is also affected by the processing given to the product (washing, peeling, or boiling) (n2). The consequence of the presence of nitrates and their final conversion into nitrites is that they oxidize the iron in hemoglobin, making them unable to transport oxygen (n1).

Bromide

Methyl bromide has had various uses for fumigation, including as a fungicide, herbicide, insecticide, and more. It could be fumigated on the soil or used as a post-harvest treatment (b1). Moreover, a significant amount of methyl bromide was likely lost to the atmosphere during fumigation before the gas could be recaptured, so environmental contamination could not be confirmed and had to be minimized. Methyl bromide released into the atmosphere had the potential to negatively impact ozone concentrations in the troposphere and stratosphere, which are very important filters for ultraviolet radiation (b2). To ensure safe products and protect public health, the European Union and the European Food Safety Authority (EFSA) issued a scientific opinion to establish a Maximum Residue Limit (MRL) for methyl bromide. However, due to low recoveries in plant-origin matrixes, a method could not be validated, and since this molecule could not be included in a multiresidue method, it was concluded that there was no evidence of being able to control the concentration of this molecule directly. However, the main metabolite of this molecule, the bromide ion, could be controlled in plant-origin food (except high-fat foods). (b3). Nevertheless, since the presence of bromide may not be exclusively due to the metabolite of methyl bromide but may also occur through natural means, especially in seawater, bromide can be detected in both soils and plant products at concentrations between 1 and 20 mg/kg (b2). For these reasons, it was decided not to include methyl bromide in Annex I of Directive 91/414/EEC and not to allow its use as an active substance in Europe (b4), while, on the other hand, a Maximum Residue Limit (MRL) was established for the bromide ion, which is still in effect to date (b5), (b3).

Why participate in a proficiency test program?

Participating in TestQual's proficiency test programs can help you maintain the utmost confidence in your results. The ability of laboratories to analyze and obtain reliable results is crucial for public health. TestQual's proficiency tests provide an opportunity to compare your analysis results with participants from all around the world, allowing you to evaluate your results over time and detect any deviations for prompt correction (specially now that we offer fast evaluation). While a single participation may reveal potential errors, the true value of TestQual's proficiency tests lies in regular and continuous participation, along with each laboratory's internal quality controls, ensuring proper control of the proposed parameters' analysis.

How to register for participation

Laboratories that wish to participate and are not yet registered on our website can do it completing the
REGISTRATION FORM.

If your laboratory is already registered on our website, you can request the participation in this proficiency test by clicking the "Participate" button located both at the top right and bottom of this page. After loggin in, in the PARTICIPATION REQUEST, you must submit your quantification limits of the analytes your laboratory studies. This information is reviewed to ensure the participation will be useful to your laboratory.

Analytes marked as "Not analyzed" (NA) will not appear later, when submitting your data in the results' form. We want to help you focus on the analysis and save you time while giving the best service: you can contact our team and they will give you different options to allow the inscription to this proficiency test, saving time and still ensuring the participation will be useful.
Once the registration is submitted, you will receive an email with your laboratory code for participation in this Proficiency test as soon as possible. Limits of Quantification are requested to ensure that the proficiency test will be useful for you, and in case of any doubts, we would contact you, so you can make an informed decision about your participation. Our aim is to help you showcase your quality.

Contact

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Thank you very much for your interest/trust in TestQual and our proficiency test programs.