HEPES (CAS 7365-45-9): storage and disposal

Keep it away from strong acids and strong alkalis, simply to avoid mixed spills. The powder belongs on the general shelf, dry, labelled and dated on arrival, apart from food grade supplies. Keep the tub tightly closed because open powder may draw damp from the air and clump. The 1 M buffer is the item that causes confusion in a shared laboratory fridge or bench cupboard. Label it with the name, the strength, the date made and the person responsible, since colourless buffers look alike. Keep solutions in clean, capped bottles that are not topped up from used ones, and do not return a pipetted portion to the stock bottle.

Good powder is white and loose. Lumps, a damp look or a tub that rattles like a solid block mean moisture has entered, and the cause is almost always a cap left slack. Buffer solution that was clear when made may turn cloudy, show floating specks or develop a film once microbes have grown in it, which is common in solutions that have been opened many times. Otherwise this substance gives few visible signs. General checks also apply, including faded labels, cracked bottles and an unknown date of receipt. A bottle that is cloudy and unlabelled should be left closed, recorded and held for collection rather than examined further.

We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a non-regulated or low hazard laboratory pack with compatible chemicals.

Surplus HEPES does not go into a sink, a drain, a general waste bin or a skip, and nobody should try to treat the solution first, even though it is not normally classified as hazardous. Collection is by specialist route, with bottles grouped alongside compatible items. For a university store the entry usually sits under waste code 16 05 09 with a plain waste transfer note, and the producer confirms the classification. Note whether it is powder or 1 M buffer, the container size and anything added to it, because a used buffer with other components may need describing differently from clean stock.

Usually held as: solid, 1 M buffer.

Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.