Does money earned from working in an interest-based bank become purified by giving a portion of it in charity?

It is impermissible, according to Islamic law, to work in usurious banks. The money earned from such work is not purified by donating a portion of it or by performing some charitable acts. If the questioner cannot find any other work and is compelled to work there, she may do so only to the extent that it alleviates her dire need.