How to analyze heavy metals in limestone?
Thread Content
I would like to analyze the heavy metal content (in terms of lead) in the limestone (calcium carbonate) used by the company. Do you have any good recommendations?
Limestone generally belongs to sedimentary rocks, and the proportion of heavy metals is not high. Select an appropriate acid to dissolve the sample, and then analyze it using atomic absorption or ICP atomic emission spectroscopy. Atomic emission spectroscopy analysis allows for the simultaneous analysis of multiple elements, making it a good choice. For the accurate quantitative analysis of a certain heavy metal, colorimetry can be used.
It is best to describe the types of heavy metals to be analyzed and the quality requirements to be met. For example, calcium carbonate, which is a food additive, has requirements regarding lead content (I can’t remember whether it’s less than 5 mg/kg or what exactly); flame atomic absorption spectroscopy cannot be used for analysis after simple acid digestion, but graphite furnace spectroscopy can be employed. Arsenic determination can be carried out using the silver salt method or atomic fluorescence method. The ICP mentioned by Teacher Q is a relatively ideal testing device.
The heavy metal content in limestone (calcium carbonate), expressed in terms of lead, can be determined using methods such as graphite furnace atomic absorption spectroscopy and ICP. If it’s only flame atomic absorption, direct acid hydrolysis seems not to work; could organic extraction followed by analysis be considered? I haven’t tried it. Also, atomic fluorescence and hydride generation seem to work; I haven’t tried them either.
ICP certainly works, but not many users who ask such questions actually have access to ICP, as the equipment is quite expensive and not commonly found in small and medium-sized enterprises.
A few million bucks, I guess:lol
There are also domestic ICP-OES instruments that cost hundreds of thousands of yuan; I haven’t used them, so I don’t dare to speak casually about them.
I was wrong; it’s not that expensive: lol
This post was last edited by qugd on 2022-5-16 at 13:57. If an accurate determination is not necessary, there is a simple method: dissolve the sample in hydrochloric acid; if needed, add nitric acid or use aqua regia to completely decompose the sample. Then remove the nitric acid, adjust the sample solution to a weakly acidic or neutral pH, add thiourea to precipitate most transition metals and heavy metals as sulfides, wash, dry, and weigh them. The result can then be expressed in terms of lead sulfide. Don’t assume that all analytical tests require the use of instruments; in fact, some simple and practical methods can solve many real-world problems.