"微量无机物" can be translated into English as "trace inorganic substances" or "trace inorganic compounds".
"Trace" means a very small amount, which accurately conveys the meaning of "微量" (trace amount).
"Inorganic substances" or "inorganic compounds" refers to substances or compounds that do not contain carbon-hydrogen bonds (with some exceptions, like carbonates), aligning with the concept of "无机物" (inorganic matter).
Both translations are appropriate, and the choice between them may depend on the specific context or the level of technicality desired.