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Chemical collection and stock control for UK schools, universities and hospitals

DAPI (CAS 28718-90-3): storage and disposal

Nuclei glow blue under UV because of DAPI, the fluorescent DNA stain held in university, pathology and histology stores as the dihydrochloride powder and in mounting media. It irritates skin and airways and can cause an allergic skin reaction. Solutions are light sensitive and are often kept frozen in small aliquots, so a research lab may have a freezer box of tiny tubes as well as a jar of powder to account for.

CAS number
28718-90-3
Form
Solid
Storage class
General
Signal word
Warning
Usual EWC code
16 05 06*
  • Harmful or irritant pictogramHarmful or irritant

What to do this week

  1. Check the label is readable and write down the opened date if it is not already there.
  2. Check it is stored as general stock and apart from the items listed under "Do not store with".
  3. If you no longer need it, add it to your disposal list so it goes on the next collection.

Safe storage in a school or lab

In a university research lab, the stock usually sits in two places: the powder jar in a dry cupboard, and the frozen aliquots in a freezer box. Both need records. Because it can cause an allergic skin reaction, gloves are essential and repeated skin contact should be avoided. Keep solutions in the dark, in foil or amber tubes, and label each tube with the date. The mounting media with DAPI should be kept with its own label and supplier information, since the powder jar does not describe it. Freezer labels peel in the cold, so use ones that stay legible.

How to tell it has deteriorated

Condition of the container and label is the first thing to check. Frozen tubes lose labels as the ink fades or peels, and a tube without a legible label is an unknown, not a spare. Thaw marks, cracked caps and ice on the outside of a box can suggest repeated freezing and thawing. The powder should be dry and free flowing, so clumping or a damp look shows moisture has entered. Because solutions are light sensitive, prolonged light exposure may affect their suitability for staining, even where the contents remain correctly identified. Few other signs can be relied on, so a missing date or record is enough to list the item.

How it must be disposed of

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.

Freezer aliquots and the powder jar are separate lines on the request, along with any mounting media bottles, each with size and a count of tubes. A university or laboratory store uses 16 05 06* for this stain, and a human healthcare pathology service uses 18 01 06*. Keep the tubes together in a labelled box so they can be grouped in a lab pack. Tubes are never thawed and emptied into a sink, and the stain does not go in general waste. Nobody should try to treat the contents. Mention if a freezer clear-out is the reason for the request.

Waste codes and transport details for DAPI
EWC code, laboratory chemicals16 05 06*
Discarded organic chemical, not a laboratory pack16 05 08*
Human healthcare setting18 01 06*
Hazardous wasteYes

The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.

Common quantities we collect

Usually held as: dihydrochloride, mounting media.

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.

Where it is commonly held

Hazard statements

  • H315 Causes skin irritation.
  • H317 May cause an allergic skin reaction.
  • H335 May cause respiratory irritation.
Precautionary statements
  • P261 Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264 Wash hands and exposed skin thoroughly after handling.
  • P271 Use only outdoors or in a well-ventilated area.
  • P272 Contaminated work clothing should not be allowed out of the workplace.
  • P280 Wear protective gloves, protective clothing, eye protection and face protection.
  • P302+P352 IF ON SKIN: Wash with plenty of water.
  • P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
  • P319 Get medical help if you feel unwell.
  • P321 Specific treatment (see supplemental first aid instruction on this label).
  • P332+P317 If skin irritation occurs: Get medical help.
  • P333+P317 If skin irritation or rash occurs: Get medical help.
  • P362+P364 Take off contaminated clothing. And wash it before reuse.
  • P403+P233 Store in a well-ventilated place. Keep container tightly closed.
  • P405 Store locked up.
  • P501 Dispose of contents and container in accordance with local, regional, national and international regulations.

Substance as classified, dilutions may differ.

Questions

How do we list a freezer box of DAPI aliquots?

Treat the box as one line, with the number of tubes, the approximate volume of each and the date if known. Keep it labelled and sealed, and mention that the contents are light sensitive solutions.

Is DAPI more hazardous than other nuclear stains?

Its classification covers skin and airway irritation and an allergic skin reaction. That is enough to need gloves, careful opening of the powder and controlled storage, whatever neighbouring stains are classified as.

Do tubes with faded freezer labels count as unknown?

Yes. If the label has gone, the contents cannot be confirmed. Keep the tube sealed, note where it was found and list it as unknown stock.

Is DAPI mounting medium the same as the powder?

No. Mounting media are separate products with their own labels and safety information, so list each bottle as its own item on the request, separate from the powder jar and from any frozen aliquots.

Guidance only. Check your own risk assessment and your supplier's safety data sheet.

Hazard data source: PubChem GHS Classification, retrieved 31 Oct 2026. Formula C16H17Cl2N5. EC number 249-186-7.

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