PhD Scientific Days 2026

Poster Session 2.G - Pharmaceutical Sciences and Health Technologies

A new insight on the potentiometric log P determination of therapeutically important opioids and fluoroquinolones

Name of the presenter

Malik, Alaa

Institute/workplace of the presenter

Semmelweis University

Authors

Alaa Malik¹, Béla Noszál¹, Károly Mazák¹
1: Semmelweis University, Department of Pharmaceutical Chemistry, Hőgyes E. u. 9., H-1092 Budapest, Hungary

Text of the abstract

Introduction:
Lipophilicity is a crucial physicochemical property that affects ADME behavior, toxicity, and adverse effects of drugs. It is commonly quantified using partition coefficients, typically determined in octanol–water systems. Reliable determination of partition coefficients and their logarithms (log P) is essential in pharmaceutical research and drug design. However, traditional methods such as the shake-flask procedure, chromatographic techniques, or potentiometric titration with specialized instruments are often time-consuming or require expensive equipment.
Aims:
This study aims to demonstrate that potentiometric titration using a simple and affordable titrator can serve as a practical and efficient alternative method for evaluating lipophilicity.
Methods
The partitioning behavior of opioids and fluoroquinolones was investigated by determining their apparent protonation macro- and microconstants in aqueous/organic biphasic systems. Titrations were performed under controlled aqueous–organic phase ratios with optimized equilibration times to ensure accurate electrode response. Species-specific log p values for amphoteric compounds were calculated based on shifts in apparent protonation constants in the presence of the organic solvent at different phase ratios, using established equations.
Results:
The results showed that log p values derived from potentiometric measurements using species-specific microconstants are highly reproducible and internally consistent. These values were found to be more reliable than those obtained using macroconstants, which has been the only approach reported in the literature until now.
Conclusion:
This study demonstrates that accurate lipophilicity assessment does not require costly or specialized equipment. A standard, low-cost potentiometric setup can provide accurate, reliable, and robust lipophilicity data under moderate cost conditions.
Funding:
This research was supported by the Stipendium Hungaricum scholarship.