NP-40 is a commercially available detergent

Detergent

A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...

. 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

Nonidet P-40

Nonidet P-40 is a nonionic, non-denaturing detergent. Its official IUPAC name is octylphenoxypolyethoxyethanol. Nonidet is a trademark of Shell Chemical Co....

 (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.