The number of substances monitored in the environment is rapidly increasing in the last years. Among them, some substances such as the Bis(2-ethylhexyl) phthalate (DEHP) are already part of the first priority substances list to be monitored in the European Water Framework Directive (No. 2477/2001/EC). In addition to these substances, since August 2013 new substances have been included in this list (Directive 2013/39/EU), such as the perfluorooctane sulfonic acid and its derivatives (PFOS). Moreover, other phthalates, perfluorooctanoic acid (PFOA) and PFOS compounds were recently largely investigated in national screening studies in surface and groundwater (France, 2011 and 2012). Due to their properties, these compounds are often part of composition of many plastics that are used in tubing material for surface water or wastewater sampling operations. Nowadays, it is generally accepted that the uncertainty of a chemical measurement is a crucial parameter for enabling the reliable interpretation of a measurement result for any purpose. It is also widely agreed that the measurement process begins at the time when a primary sample is taken, rather than when a delivered sample arrives at the analytical laboratory. Water sampling within environmental monitoring programs often require operations that involve more or less prolonged contact between water sample and different materials such as pumping tubes. AQUAREF (National reference laboratory for water and the aquatic environment) technical guidances suggested the use of Teflon® material as a component of the sampling equipment for the monitoring of the micropollutants. However, these guidances were established taking in account studies essentially performed on inorganic (metals) or organic (pesticides or PAHs) compounds. The results obtained on phthalates join the findings observed in the tests conducted by the BRGM for groundwater in 2012 and may partly explain the high frequency of quantification found during the 2012 screening study (see presentation Botta et. al, SETAC 2015). From the point of view of technical instructions for WFD monitoring programs, these results do not lead to a categorical choice of material for tubing to improve the quality of results on phthalates. Only possible research or monitoring of the substance DEP/ DiBP may lead to pay attention to the material used for sampling or the sampling duration. We conclude that field blank must become of routine in monitoring.