# Novel spectrophotometric method for the determination of paclitaxel through complex formation with osmium

## TL;DR

A new spectrophotometric method using osmium to accurately measure paclitaxel in drugs and biological samples is developed and validated.

## Contribution

A novel spectrophotometric method for paclitaxel quantification via osmium complex formation is introduced.

## Key findings

- The method shows a linear calibration curve from 1.0–55 μg/mL with high precision and accuracy.
- The method was successfully applied to pharmaceutical injections and spiked biological fluids.
- Recovery values ranged from 98.70% to 100.23% with low LOD and LOQ values.

## Abstract

Paclitaxel (Pac) is an important anticancer bioactive compound, and the availability of an accurate and robust analytical method for its quantification is of utmost importance. In this investigation, a novel, direct, and reliable spectrophotometric method has been proposed for the estimation of Pac via a complex formation reaction with osmium (Os). The method was based on the reaction of Pac with Os tetroxide, which produced a yellowish-brown complex. The resulting complex is soluble in water and displays a maximum absorption peak at 482 nm. The reaction conditions, including reactant concentration, pH, temperature, and reaction time, were optimized to obtain the best spectrophotometric response. A thorough method validation study was conducted, demonstrating that the calibration curve is linear over the concentration range of 1.0–55 μg/mL and follows Beer’s law, with a molar absorptivity of 3.01 × 10−4 L/mol−1.cm−1. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.0098 and 0.0328 μg/mL, respectively. The recovery values were planned and found to be 98.70%–100.23%. At the same time, the precision values (represented by relative standard deviation percent [RSD%]) were better than 0.81% (in injections) and 1.859% (in biological fluids), depending on the Pac concentration. The suggested method was successfully applied to estimate Pac in a pharmaceutical formulation (as injections) and in spiked biological fluids (serum and urine), with results showing good accuracy and precision compared to the reference method.