ppm同concentration (M) 轉換

ppm is what you said: parts per million. It is strictly not used to describe concentration; for ppm has NO unit; concentration has unit, e.g. g/cc.

So what is ppm? To give you an example first: 1 ppm of sugar in water is equivalent to 1 microgram (ug) of sugar in 1 gram (g) of water. Why is that? 1 g = 1,000,000 ug; so it is like 1 ug of sugar in 1 million ug of water, which is equivalent to 1 ppm. Hope this is easy to understand. So technically, anything which represents itself among 1 million of other things is ppm.

So you see it applies to any state: gas, liquid or solid. It also applies to anything. If someone says 1 ppm of chlorine in water, which is 1 ug of chlorine (gas) in 1 g of water (liquid). Also ppm can be applied to other context; like 1 person out of 1 million is a genius; that's also 1 ppm. See, it can be used anywhere; but mostly in chemistry.