Optimizing solid phase extraction and HPLC-MS/MS parameters for reliable quantification of COVID-19 pharmaceuticals in Mexico City’s wastewater: A design of experiments approach

• Published in: Microchemical journal 2024-05, Vol.200, p.110493, Article 110493
• Main Authors: Cortés-Lagunes, Ruth Silvana, Garduño-Jiménez, Andrea-Lorena, Romero-Solano, Alonso, Zanella, Rodolfo, Prado, Blanca, Zamora, O., Durán-Álvarez, Juan C.
• Format: Article
• Language: English
• Subjects: Box-Behnken; Pharmaceuticals; Plackett-Burnam; Validation; Water reuse
• ISSN: 0026-265X
• DOI: 10.1016/j.microc.2024.110493

[Display omitted] •COVID-19 prompted widespread disposal of a plethora of pharmaceuticals in sewage.•Validation of a SPE-HPLC-MS/MS method for analyzing six COVID-19 pharmaceuticals.•Box-Benhken and Plackett-Burman DoE to optimize the HPLC-MS/MS conditions.•SPE optimized using HLB cartridges retaining both polar and non-polar analytes.•The validated method displayed robustness when analyzing different types of water. Through the COVID-19 health crisis, a plethora of new medications, along with some discontinued pharmaceuticals, were directly tested on population to assess their efficacy in symptom management. Consequently, residues from these treatments were systematically disposed into sewage systems, presenting a novel contamination challenge in urban centers. To effectively address this issue by environmental authorities, the presence of these pollutants in wastewater must be accurately quantified. Herein, we conducted a meticulous study to validate an analytical method based on solid-phase extraction (SPE) and high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) to detect six pharmaceuticals (metformin, famotidine, indomethacin, dexamethasone, azithromycin, and ivermectin) in wastewater. Using a Plackett-Burman design (PBD), the eight parameters significantly impacting on the HPLC-MS/MS technique were established based on the analytical signal of the six analytes. Subsequently, in conjunction with a Box-Behnken design (BBD), optimal analysis conditions were determined as follows: injection volume: 10 µL, column temperature: 20 °C, capillary voltage: 4100 V, drying gas temperature and flow rate of 350 °C and 7 L min−1 respectively, nebulizer pressure: 15 psi, concentration of formic acid and ammonium acetate in the mobile phase of 0.1 % and 10 mmol/L, respectively. SPE was optimized through a univariable experimental design. OASIS HLB cartridges exhibited the highest extraction efficiency compared to highly polar and non-polar adsorbents. The optimal sample loading conditions were set as 250.0 mL of water sample at pH = 9.0. The washing conditions were 5.0 mL of a 95:5 water:methanol solution, while elution conditions were optimal using 6.0 mL of a 98:2 methanol:formic acid solution. After evaporating the eluate to dryness and reconstituting in 1.0 mL of a 98:2 methanol:formic acid solution, a concentration factor of 250 was achieved. The analytical method was validated using for matrices, namely, raw and treated was