We understand that when performing analytical filtration in your laboratory, particle retention efficiency is critical to your research. In this type of testing, the production of accurate results depends especially on the filter's performance in retaining microorganisms on the membrane. With the above in mind, we have carefully crafted Nalgene analytical filter products. For over 50 years, we have provided precise, easy-to-use microbial and particle recovery systems for QC testing and research. Equipment performance exceeds recycling requirements specified in ISO 7704. CN membranes for bacteriological analysis of drinking water are produced according to the procedures in the referenced APHA standard methods and laboratory standards for equipment and materials specified by the US Environmental Protection Agency.