OPTICAL SENSORS FOR DETERMINATION OF HEAVY-METAL IONS

A review is given on optical means for single shot testing (''probing' ') as well as continuous monitoring (''sensing'') of heavy metal ions (HMs). Following an introduction into indicator,based approaches, we d iscuss the types of indicator dyes and polymeric supports used, as wel l as existing sensing schemes for HMs. The wealth of information is co mpiled in the form of tables and critically reviewed. Notwithstanding the tremendous work performed so far, it is obvious that still severe limitations do exist in terms of selectivity, limits of detection, dyn amic ranges, applicability to specific problems, and reversibility. On the other hand, such sensors have found - and will find - their appli cation whenever rapid and cost-effective testing is required, where pe rsonnel is scarce or unskilled, and in field tests. Despite their limi tations, the number of such sensors (and of irreversible ''probes'') f or HMs is likely to increase in future.