Sub-microgram-scale analysis by coulometry at controlled potential

✍ Scribed by Louis Meites

• Book ID: 102980816
• Publisher: Elsevier Science
• Year: 1959
• Tongue: English
• Weight: 598 KB
• Volume: 20
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(59)80097-0

✦ Synopsis

The utility of coulomctry at controlled potential in analyses at the decigram to milligram lcvcl is now well established, but the practical problems involved insecuring accurate current integrations at that lcvcl liavc been solved too recently to permit any concern with the further problems that may bc cxpcctcd to arise in dealing with much smaller amounts of material. 1Meanwhilc many successful applications of coulomctry at controlled current to microgram-scale analyses have been described. These facts have led to a general belief that the controlled-current tcclmiquc is the more useful of tile two in trace analyses.

This belief has been held dcspitc the demonstration by I,OICII, O'NEIIL, AND ROGEI~S~ that cvcn rnillimicrogram amounts of silver can bc determined with good accuracy by a procedure which, though quite diffcrcnt in apparatus and mcthoclology, conforms to any operational definition of coulomctry at controlled potential. More recently, using more conventional proccdurcs, UOOMAN, 'l-Ic~L131~ooxc, ANI) k151N2 have succccdcd in determining 7.5 ,ug of uraniuln with a standard deviation of j= 2.2O/c,, while MEITES~ was able to obtain a mean clcviation of & I.o"/~ in the determination of 5.2 pg of chromium.

The present paper dcscribcs the results of an attempt to extend coulomctry at controlled potential to its cxtrcmc lower limit, using a chemical system which was believed to be ideally suited to that purpose togcthcr with conventional apparatus and techniques for current integration. This attempt was made, partly in pursuance of the considerations described above, and partly in the hope of casting new light on the sources of error which afflict all analyses by coulomctry at controlled potential and on the techniques by which these errors can bc cl'minatcd.