I am Ivan Viveros, auditor of IDEAM the institution that accredits environmental laboratories in Colombia in ISO 17025. This message is aimed to inquire about the current validity of the method published from page 355-357, volume 11, issue 7, Analytical Methods, H. Gustafson A. S. Behrman. The IDEAM received a request to accredit an environmental laboratory in total dissolved solids in water under the method mentioned above; however, the date of the article attracts attention. I would like to confirm if the method quoted is valid yet. If you a technical reason to reject it or to accept it please let me know it.