NP-40 is a commercially available detergent. The full name of NP-40 is Tergitol-type NP-40, which is nonyl phenoxypolyethoxylethanol.
Care should be taken to avoid confusing NP-40 with Nonidet P-40 (octyl phenoxypolyethoxylethanol).
This detergent is not powerful enough to break the nuclear membrane, but can break the cytoplasmic membrane. As such, it can be used to obtain the cytoplasmic contents of a cellular culture.