I made a 5M NaCl solution and tried to pass it through a 0.02 anotop filter. After the first 10 ml, the filter seem to have clogged. Is NaCl somehow crystallizing and clogging the filters? Which means the final concentration will not be 5M. If something like that is happening, it'd be better to keep the 5M stock as is and filter the working solutions from the 5M stock.