[ken3009]

i have used this method to measure fats, but sometimes for samples like honey i do not wash the fat flasks after taking the first constant weight because i dont see any black or insoluble particles in the flask. but the result is too high (like 4.5g/100g, and it should be 0.5g/100g for example). is it possible there could be sugars present in the flask? i extracted carefully with the mojonnier tubes, but could sugars dissolve in the ether?? how do i identify if a flask needs washing or not if there are no black/brown particles in it???

[Hunter2]

Did you compare with a new flask?  Sugar should be soluble in water.

[Arkcon]

Briefly, if the method calls for a washing, you should do it.  If the method doesn't say that you shouldn't wash a flask, you should wash thoroughly and dry to constant weight before performing any analytical procedure.  That's just good QA laboratory hygiene.

[ken3009]

no what im sayingis, how do i know which samples to wash and which not to. i know for sure that flasks wit black/brown insoluble residue i need to wash, but can the residue be almost the color of fat, or whitish??