Spectrophotometric and cloud point extraction methods to detect Quercetin Dihydrate in supplement formulations and urine samples

The accurate detection and quantification of quercetin dihydrate (QRC) are vital for quality control, pharmacokinetic studies, and bioavailability assessments in pharmaceutical and biological samples. This study aimed to develop and validate a cloud point extraction (CPE) method combined with spectrophotometry for the sensitive and environmentally friendly detection and quantification of QRC in pharmaceutical formulations and spiked urine samples. Methods. The CPE method employed Triton X-114 as a non-ionic surfactant to extract QRC from samples. The extraction process was optimized by evaluating key parameters, including surfactant concentration, incubation temperature, extraction time, and centrifugation speed. Spectrophotometric analysis was conducted before and after extraction to assess the sensitivity and linearity of the method. The method was validated using spiked urine samples and pharmaceutical formulations of QRC, with recovery rates, limits of detection (LOD), and linearity evaluated to ensure accuracy and precision. Results. The optimized CPE conditions included an incubation temperature of 65°C, a 5-minute extraction time, and centrifugation at 3500 rpm. The CPE method significantly improved the sensitivity of QRC detection, reducing the LOD from 0.0351 μg/mL (without CPE) to 0.0234 μg/mL (with CPE). The method exhibited excellent linearity (r² > 0.998) over a wide concentration range (1–12 μg/mL). High recovery rates (98.88% to 101.6%) and low relative standard deviations (RSD < 2%) were observed in pharmaceutical formulations and spiked urine samples, demonstrating the method’s accuracy and precision. The enrichment factor was 1.75, and the preconcentration factor was 4.6. Conclusions. The proposed CPE method combined with spectrophotometry provides a simple, sensitive, and environmentally friendly approach for QRC analysis. It offers significant advantages over conventional methods, including reduced organic solvent use and waste generation, making it suitable for routine analysis in pharmaceutical quality control and pharmacokinetic studies. The method’s adaptability to complex matrices, such as urine, and its potential for broader applications, including the analysis of other polyphenolic compounds, were also demonstrated.