Selective and sentivive method based on capillary liquid chromatography with in-tube solid phase microextraction for determination of monochloramine in water

• A critical examination of monochloramine standard synthesis conditions has been performed.
• A comparative study for determination of monochloramine by using different colorimetric methods has been carried out.
• Influence of the pH of mobile phase and the volume of sample processed by using IT-SMPE Capillary LC DAD have been investigated and optimized.
• A selective and sensitive method for determination of monochlormine in water based in capillary HPLC has been developed.
• Better LOD and LOQ were found with respect other procedures for determination of monochloramines.

Due to the difficulties of working with chloramines, a critical examination of monochloramine standard preparation has been performed in order to select the best synthesis conditions. The analyte has been determined by in-tube solid phase extraction coupled to capillary liquid chromatography with UV detection (IT-SPME Capillary LC DAD). Potential factors affecting the response of monochloramine such as the pH of mobile phase and the volume of sample processed by IT-SPME Capillary LC DAD have been investigated and optimized. According to the results of the study, 0.1 mL or 4.0 mL of sample at neutral pH were loaded in the chromatographic system. A sensitive and selective method has been developed for the determination of monochloramine in water. Validation of the method has been performed. The linear range was 0.09-5 mg/L with linear regression coefficients (R2) greater than 0.995. Method reproducibility expressed as relative standard deviation (RSD, %), was lower than 15%. The limits of detection (LODs) were 0.029 and 0.01 mg/L by processing 0.100 mL or 4 mL of the samples, respectively, being below the maximum residues levels allowed for this compound. The sensitivity achieved by the developed method was better than that obtained by the reference method. The developed method was applied to water samples (tap and swimming pool water).