Liquid-liquid extraction with long wavelength fluorescence detection

Long wavelength fluorophores, methylene blue, Rhodamine 800, 3,3'diethyloxacarbocyanine iodide (DODC) and 1, 1',3,3,3' ,3' -hexamethylindotricarbocyanine perchlorate (HIDTCP) were investigated as probes to quantify drugs after liquid-liquid extraction. Fluorescence measurements in the long wavelength region (550-1000nm) are a recent development in photoluminescence spectroscopy and offer many advantages compared with conventional measurements which are made in the ultraviolet and visible spectral regions. These include, reduced background fluorescence in the presence of biological materials; reduced scattering; decreased photodecomposition and the availability of inexpensive, solid state optical components which operate in the long wavelength spectral region. On-line liquid-liquid extraction was carried out using a phase separator, with an efficiency of separation of 96%, designed "in-house". This technique offers the advantages of low sample consumption; rapid rates of analysis and minimisation of operator contact with the extracting solvent when compared with manual extraction. The proposed extraction manifold used was able to determine flufenamic acid, phenylbutazone and warfarin within their therapeutic ranges. Studies also revealed that the process was buffer pH and ion dependent. Ion pairs as well as differing ratios of fluorophore, depending upon the fluorophore, were found to be extracted in the presence of named drugs. The technique was found to be suitable for the detection of the drugs when present in human serum within their therapeutic ranges. Finally, an investigation into an alternative to chloroform (density = 1.47g/ml) as the extracting solvent using dimethylmaleonate (density = 1.154g/ml) and diethylacetoacetate (density = 1.025g/ml) proved unsuccessful.