OPTICAL SENSING OF SULFITE WITH A PHOSPHORESCENT PROBE

Spectral-luminescent properties and quenching behavior of the covalent conjugate of the platinum(II) complex of coproporphyrin-I and bovine serum albumin (PtCP-BSA) was investigated. Quenching of phosphorescenc e by sulfite was studied in detail in an acidic range as a function of pH. Strong dynamic quenching of the phosphorescence by sulfite occurr ed at pH below 4.0 which was attributed to the formation of sulfur dio xide. The quenching reached its maximal level at pH below 1.5, Stern-V olmer quenching constants being as high as 2000 M-1. A new flow-inject ion system for the determination of sulfite was developed based on the PtCP-BSA conjugate immobilized on a preactivated Biodyne ABC membrane and placed in a flow-cell, with an acidic carrier buffer and fiber-op tic phosphorescent detector. Such a solid-state phosphorescent probe i s quenchable by sulfite and allowed rapid on-line detection of sulfite with a detection Limit of about 10 mu M. Performance of the new syste m and possible interferences were investigated. (C) 1998 Elsevier Scie nce B.V. All rights reserved.