A correct sample represents the whole lot. That means choosing packages at random, using clean tools suited to the product, sampling from the right depths, and sealing and labelling the samples so nobody can swap or alter them.
Poor sampling causes more disputes than poor testing. If the sample is not representative, even a perfect lab result tells you nothing about the shipment. ASTM E300 is a widely used reference practice for sampling industrial chemicals.
How many drums or bags to sample
A common rule of thumb for packaged goods is to sample the square root of the number of packages, plus one, rounded up. For 80 drums, that means about 10. Your contract or the relevant standard may set a different plan.
Choose the packages yourself, at random, from across the whole lot. Do not let the factory pick them. Check that their batch numbers match the packing list and the certificate of analysis.
Sampling liquids
- Mix or roll drums first where the product may settle or separate, if the product allows it.
- Use a clean sampling tube or drum thief that reaches the full depth, so you capture top, middle and bottom.
- For tanks, take samples from upper, middle and lower levels, and keep them separate or combine them as the contract requires.
- Take a separate bottom sample from tanks where water or sediment may collect.
- Use sample bottles made of material that will not react with or contaminate the product, often glass or suitable plastic.
Sampling solids
- Use a sampling spear or trier that reaches the centre and bottom of the bag or drum, not just the surface.
- Avoid surface material that may have absorbed moisture or been contaminated when the package was opened.
- Combine increments from each package into a composite if the specification is checked on the lot as a whole.
- Reduce a large composite by quartering or a sample divider, rather than scooping from the top.
Sealing and records
Divide the sample into identical portions, usually three: one for testing, one retained by you and one for the supplier. Seal each container with a numbered seal, and label it with product, batch, date, packages sampled and the names of those present.
Record the process in writing with photos, including seal numbers. Reseal the opened packages so the shipment is not contaminated. This record, called a chain of custody, is what makes the sample count in a dispute, as explained in handling a quality claim.
Safety
Sampling hazardous chemicals exposes people to the product. The sampler should read the SDS and wear the protective equipment it specifies, work in a ventilated area, and follow the plant's own safety rules. Flammable products need tools that do not cause sparks.
Next step
We draw, split and seal samples at the factory and keep the chain-of-custody record. To start, book a free sourcing review.