Separation and Detection of Toxic Metals

The same solvent is used in each case the orders of migration distances are  

Detection 1 group 0.5% aqueous NagS solution 2 group saturated solution of alizarin in 96% ethanol. The layers are exposed to NH3 vapour after spraying. 

Since the spectrophotometric determination of Hg by means of di-thizone can be falsified by other heavy metals and oxidation products of the dithizone, it is best to purify the dithizone extract by TLC beforehand. The various metal dithizonates, dithizone and its oxidation products are separated from one another on the chromatogram. In particular the ubiquitous Cu-dithizonate can be separated. The spots of Hg-dithizonate may be scraped off, eluted and evaluated colorimetric-ally. The order of migration distances is  

Layer Silica gel G (Firm 88) it is purified by allowing methanol-hydrochloric acid to ascend about 18 cm before separation. 

Good separations of the ci 4rans isomers of complexes of the type (Coen2Cl2)X (X = CF, NO3, SCN ) and of nitro-compormds of Co are possible. The cis-forms always migrate further than the corresponding trans-ionm. 

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