"impossible to collect" is a correct and usable phrase in written English.
It can be used when describing something that cannot be gathered or obtained. Example: The scattered pieces of the broken vase were impossible to collect, so I just swept them into the trash.
That a graduate tax would be hard or impossible to collect from foreign students and being centrally-collected would rob universities of autonomy.
Partly that's because absolute scientific evidence one way or the other is impossible to collect.
"Evidence of the crime is nearly impossible to collect after the fact," he said.
This would make it impossible to collect anything close to the $250 billion a year promised by the tax's proponents.
She ignored advice that such a tax would be impossible to collect and that it was also severely regressive.
In fact, it would be nearly impossible to collect every specimen; the toothbrush is one of the most reinvented of human objects, with thousands of patents on file.
The Bloomberg administration argued that the automobile exemption would prevent them from towing some cars, which would make it impossible to collect outstanding traffic fines.
The hard cap is intended as a money saver, but it could also promote parity by making it nearly impossible to collect superstars.
If this is done properly, we can dislodge a perfect sample from a rock surface that would be nearly impossible to collect with just a hammer and chisel.
These species have been almost impossible to collect until recently when techniques allowing access to the canopies have been adapted from mountain-climbing methods.
Aggressive collectors buy credit card accounts from original lenders like Chase or Bank of America that have been written off as in default and impossible to collect on.
