> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/library-preparation/general/library-preparation-general-faq-list/000005128.md).

# Can PhiX and denatured PhiX be stored and used again?

Store non-denatured, undiluted 10 nM stock PhiX at -25°C to -15°C until the expiration date.

Store non-denatured, diluted 4 nM PhiX at -25°C to -15°C for up to 3 months.

Store the denatured, diluted 20 pM PhiX at -25°C to -15°C for up to 3 weeks. After 3 weeks, cluster numbers tend to decrease.

For use with the NextSeq 500/550: Store the denatured 1.8 pM PhiX at -25°C to -15°C for up to 2 weeks. After 2 weeks, cluster numbers tend to decrease.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #5128), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000005128%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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