Papain (CAS 9001-73-4): storage and disposal

The hazard that decides where papain goes is its dust. It is a respiratory sensitiser as well as an irritant, so keep it in a tightly closed bottle on a general shelf below eye level, with the label visible and a note of the opening date. A school or college may also hold meat tenderiser or food-grade papain bought for the kitchen or the canteen, and that must stay with food supplies, never in the prep room beside laboratory stock. Keep the powder away from damp areas by the prep room washing area, because it absorbs moisture and cakes. In a university lab, avoid sharing one spatula between bottles. Buy small, because a half-used bottle of fine sensitising powder is the stock that causes most trouble later.

A good papain bottle holds a loose, pale to buff powder. What looks normal for papain is a little fine dust in the neck. What does not is hard lumps, a darker caked patch, a smell that was not there before or a sticky film on the inside of the cap. Papain breaks down proteins, but damage to labels, gloves or card is not a reliable sign of deterioration. Record any powder residue, damaged labels or container defects. As with every enzyme its activity fades invisibly, so a bottle that no longer softens jelly or meat in a practical may look entirely normal. Do not blow or sweep dust from a cracked bottle.

By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a non-regulated or low hazard laboratory pack with compatible chemicals.

Specialist collection takes it away, with sealed bottles grouped alongside other compatible solids in a lab pack. The code that fits a laboratory item is 16 05 06*. Say plainly on the paperwork that it carries the inhalation sensitiser statement, because the people loading and unloading the packs will be exposed to the dust if a bottle breaks. Leftover powder should not be brushed into the bin, washed into a sink or drain, or collected in general waste. If the stock is food-grade kitchen papain and not a laboratory reagent, describe it as such and let the collector decide how it is classed.

Usually held as: solid.

Part-used bottles and full containers are both fine. Tell us the size and how many, and an estimate is enough for a first price.