Investigating the chlorination of acidic pharmaceuticals and by-product formation aided by an experimental design methodology

• Published in: Water research (Oxford) 2010-01, Vol.44 (1), p.243-255
• Main Authors: Quintana, José Benito, Rodil, Rosario, López-Mahía, Purificación, Muniategui-Lorenzo, Soledad, Prada-Rodríguez, Darío
• Format: Article
• Language: English
• Subjects: Acidic pharmaceuticals; Anti-Inflammatory Agents, Non-Steroidal - analysis; Anti-Inflammatory Agents, Non-Steroidal - chemistry; Applied sciences; Bromides; By-products; Byproducts; Chlorination; Chromatography, Liquid; Degradation; Diclofenac; Diclofenac - analysis; Diclofenac - chemistry; drinking water; drugs; Environmental fate; Exact sciences and technology; Halogenation; Hydrogen-Ion Concentration; indomethacine; Kinetics; liquid chromatography; Liquid chromatography–mass spectrometry (LC–MS); Mass Spectrometry; methodology; Molecular Structure; Naproxen; Naproxen - analysis; Naproxen - chemistry; Non-steroidal anti-inflammatory drugs (NSAIDs); Other industrial wastes. Sewage sludge; Pharmaceuticals; Pollution; Salicylic acid; Salicylic Acid - analysis; Salicylic Acid - chemistry; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tandem Mass Spectrometry; Time-of-flight (TOF); Wastes; wastewater; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water Supply - analysis; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2009.09.018

The degradation of seven acidic drugs and two metabolites during chlorination was investigated by liquid chromatography–mass spectrometry (LC–MS). A triple-quadrupole (QqQ) system was used to follow the time course of the pharmaceuticals and by-products, while a quadrupole time-of-flight (Q-TOF) system was also used for the identification of the by-products. Under strong chlorination conditions (10mg/L Cl2, 24h), only four of the target compounds were significantly degraded: salicylic acid, naproxen, diclofenac and indomethacine. The degradation kinetics of these four compounds were investigated at different concentrations of chlorine, bromide and pH by means of a Box–Behnken experimental design. Depending on these factors, measured pseudo-first order half-lives were in the ranges: 23–573h for salicylic acid, 13–446min for naproxen, 5–328min for diclofenac and 0.4–13.4min for indomethacine. Also, it was observed that chlorine concentration was the overall most significant factor, followed by the bromide concentration (except for indomethacine), resulting in increased degradation kinetics as they are increased. The degradation path of salicylic acid, naproxen and diclofenac consisted of aromatic substitution of one or two hydrogens by chlorine and/or bromide. Moreover, for diclofenac, two other by-products corresponding to a decarboxylation/hydroxylation pathway from the monohalogenated products were also identified. On the other hand, indomethacine degradation did not lead to halogenation products but to oxidation ones. The investigation of these by-products in real samples by LC–MS/MS (QqQ) showed that the halogenated derivates of salicylic acid occurred in all the drinking water and wastewater samples analysed.