Determination of ionisation constants of radiopharmaceuticals in mixed solvents by HPLC.
The uptake of some ionogenic radiopharmaceuticals may be explained on the basis of a pH shift theory. An HPLC method for pKa measurement has been developed for radiotracers. It has been tested with several amines and used to estimate the pKsa (pKa in the mixed solvent 30% acetonitrile-water) of some 99mTc-PnAO complexes by observing the change in capacity factor k' with change in mobile phase pH. The non-ionogenic complexes Tc-PnAO and Tc-DE-PnAO showed constant k' values while the ionogenic complexes Tc-MNE-PnAO and Tc-IP-PnAO had pKsa values of about 6.6 and 8.3. The method is reproducible and is applicable to nearly all ionogenic radiopharmaceuticals.
Stylli
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Chelsea Department of Pharmacy, Kings College London (KQC), England.
Theobald
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D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006863:Hydrogen-Ion Concentration; D009942:Organometallic Compounds / Q000032:analysis*; D015609:Organotechnetium Compounds; D010091:Oximes / Q000032:analysis*; D011199:Potentiometry; D012997:Solvents; D013329:Structure-Activity Relationship; D013667:Technetium / Q000032:analysis*
D009942:Organometallic Compounds; D015609:Organotechnetium Compounds; D010091:Oximes; D012997:Solvents; C044310:technetium Tc 99m propylene amine oxime; D013667:Technetium