Abstract
A flow-through spectrophotometric bulk optode for the flow-injectiondetermination of thiocyanate is described. As active constituents, the optode incorporatesthe lipophilized pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo)phenol andmethyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl)chloridemembrane entrapped in a cellulose support. The optode is applied, in conjunction with theflow injection technique, to the determination of thiocyanate at pH 7.5 (TRIS/H2SO4). Thesensor is readily regenerated with a 10-2 M NaOH carrier solution. The analyticalcharacteristics of this optode with respect to thiocyanate response time, dynamicmeasurement range, reproducibility and selectivity are discussed. The proposed FI methodis applied to the determination of thiocyanate in waters from different sources and in humansaliva samples in order to distinguish between smokers and non-smokers.
Highlights
Many areas of applied analytical chemistry, such as process control and clinical, food and environmental sampling, require a fast and simple method for determining the concentrations of ionic species in aqueous systems
We described flow-through bulk optode membranes for the flow injection systems (FI)-determination of various inorganic ions [24,25,26,27,28]
We present a flow-through bulk optode for FIspectrophotometric determination of thiocyanate using the lipophilized pH indicator 5octadecanoyloxy–2–4–(nitrophenylazo) phenol and methyltridodecil ammonium chloride as the active constituents in a plasticized poly(vinyl) chloride membrane entrapped in a cellulose-based support
Summary
Many areas of applied analytical chemistry, such as process control and clinical, food and environmental sampling, require a fast and simple method for determining the concentrations of ionic species in aqueous systems. [8] One type of optode makes use of a plasticized polymeric membrane and is based on the reversible mass transfer of analyte from the sample into the bulk of the sensing layer. This type of optical sensor was named “bulk optode membrane” by Seiler and Simon, who described the basic principles and techniques that can be used with it [9]. We present a flow-through bulk optode for FIspectrophotometric determination of thiocyanate using the lipophilized pH indicator 5octadecanoyloxy–2–4–(nitrophenylazo) phenol and methyltridodecil ammonium chloride as the active constituents in a plasticized poly(vinyl) chloride membrane entrapped in a cellulose-based support. The flow-optode developed was applied with satisfactory results to the FI-spectrophotometric determination of thiocyanate in waters from different sources and human saliva
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