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Nitrogen is a significant indicator in environmental studies, due to its importance in treatment processes, quality control of waters and control of wastewater discharge to the environment. The Kjeldahl method is the most widely used for determining total nitrogen. There are different nitrogen species in wastewater: organic and ammonia nitrogen, nitrites, nitrates, among others. The National Standard of Wastewater Discharge (NC: #2012) mandates the determination of total nitrogen (Ntotal) by the Kjeldahl method. Selective electrodes (SE) have allowed the determination of ammonia nitrogen (Namm) with limits of quantification (LOQ) below the Kjeldahl method. This paper, evaluates the problems of determination of Ntotal and Namm in wastewater, taking into account the maximal permissible averages limits (MPAL) of the NC 27:2012 and the LOQ of the analytical methods studied.For the experiments, reference materials and swine wastewater were used. Under laboratory conditions, the LOQ of Kjeldahl nitrogen was higher (10 mg/L) the one established in the standard method (5 mg/L), which matches with the MPAL for the Cuban standard of discharge. Therefore, the laboratory has had to implement multiple standard additions, just to achieve reliable results at concentrations below its LOQ. Furthermore, it was proven that Kjeldahl and SE methods showed no significant differences in determining Namm, for concentrations at or above 10 mg/L, but for those one below the lab LOQ in the Kjeldahl method. [ABSTRACT FROM AUTHOR]

The third edition of the ISO/IEC 17025 standard had significant changes with respect to its predecessor version, such as the approach and structure based on the process, the thought and action based on risk and the new requirement of impartiality and confidentiality, among others, no less important. The problem was how to deal with the transition to this third version of the standard and meet all its requirements. The mission of the DECA Scientific-Technical Services Management Group (GG SCTDECA), of the CNIC, is to provide specialized Scientific-Technical Services (SCT) for the characterization of water, wastewater and solid waste, the design and technical task of technological treatment solutions, as well as material protection services. All of them are covered by a management system in accordance with NC-ISO / IEC 17025 and accredited by the National Accreditation Body of the Republic of Cuba (ONARC). The objective of the work was the strategy to be followed in the Group to comply with the new requirements of ISO/IEC 17025. The procedure, descriptive and qualitative, took into account the main changes, taking as a guide a correlation between the second and third edition of the standard, which allowed, together with a documentary review, to define what needed to be done or improved. The necessary actions were defined to comply with the new requirements of the third edition and a plan was drawn up, establishing the deadlines for compliance and those responsible for executing them. Among other actions, an Impartiality Policy was developed and records of Confidentiality Commitments were established for internal and external personnel who can influence the Laboratory's activities. A procedure was implemented to address the Risks and Opportunities, the risks to impartiality were identified, a Policy for information and communication with the interested parties was defined, the Process Map and the Process Files were improved, the Profiles were adapted staff competence and training seminars were held. [ABSTRACT FROM AUTHOR]

A laboratory must produce analytical data of sufficient precision and reliability within an acceptable time frame and at an allowable cost. For laboratories accredited by the 17025 standard, this objective becomes even more important, being the participation in Proficiency Testing (PT), as external quality control, the superior way of demonstrating their technical competence. DECA (formerly the Department of Studies on Environmental Pollution, today the Scientific-Technical Services Management Unit DECA), belonging to the National Center for Scientific Research in Cuba, with a long tradition of work in the field of the environment (including the characterization of water, wastewater and solid waste), achieved its first accreditation by the National Accreditation Body of the Republic of Cuba (ONARC, acronym in Spanish) in 2001 and has maintained a regular participation in PT. The objective of this work is to demonstrate the technical competence of the Unit of Management of Scientific-Technical Services (UG SCT-DECA, acronym in Spanish) in the analytical services it provides, through the results it has obtained from its continued participation in PT. Taking into account the PTs (national and international) in the period 2008-2019, different indicators were used to measure their performance, as well as graphic tools that allowed to visualize the behavior over time. The evidence demonstrates the technical competence maintained by DECA's analytical services, strengthening the quality and reliability of the results it brings to its clients, which has allowed the faithfulness of a considerable number of them. [ABSTRACT FROM AUTHOR]