Determination of Oxyhalide Disinfection By-products in Water by Suppressed Anion Chromatography Coupled with Mass Spectrometry

New Organic Monitoring Techniques
Poster Presentation

Presented by R. Marfil-Vega
Prepared by H. Guo1, R. Marfil-Vega2
1 - Shimadzu Scentific Instruments, 7102 Riverwood Drive, Columbia, MD, 21046, United States
2 - Shimadzu Scientific Instruments, 7102 Riverwood Drive, Columbia, MD, 21046, United States


Contact Information: huguo@shimadzu.com; 410-910-0985

ABSTRACT

Potable waters are usually treated with disinfectants such as chlorine dioxide and ozone to protect public health. Disinfectants are applied for inactivating harmful microorganisms present in the water. An unintended consequence of the disinfection process is the formation of oxyhalide disinfection by-products (DBPs) such as chlorite and bromate, which have shown negative effects on to human health. Therefore, EPA National Drinking Water Regulations has established Maximum Contaminant Level (MCL) for bromate and chlorite at10 ppb and 1 ppm, respectively. There are numerous techniques for the analysis of oxyhalide DBPs in water. Ion chromatography is now considered the most popular and fast technique. Chlorite (ClO2-), chlorate (ClO3-) and bromate (BrO3-) have been widely and routinely determined by suppressed ion chromatography with conductivity detection. However, reaching the sensitivity required with IC based methods such as EPA 300 and 300.1 may be challenging during the analysis of complex environmental samples; alternative methods relying in post-column additions or 2D chromatography (i.e EPA method 317, 326, 302…) may be needed for achieving the desired performance. As alternative to these complex methods, the use of IC coupled with MS was evaluated to demonstrate the improved sensitivity and selectivity for accurate measurement of ionic substances at the trace concentrations in complex sample matrix.

In this study, an IC-MS method was developed using a novel electrolytically regenerated anion suppressor as a part of a modular IC system coupled with a single quadrupole MS to achieve higher sensitivity and selectivity for DBPs determination in water and bottled beverages. Both conductivity detection (CDD) and MS with electrospray ionization are used in the method. The CDD is used to monitor the ionic effluent; only the oxyhalides DBPs of interest are directed to MS via a divert valve. With the addition of MS detection, the method has improved the identification, sensitivity and selectivity. Confirmation of the oxyhalides DBPs is based on retention time and mass to charge ratio. Selected ion monitoring (SIM) was used in the study for identification and quantification of DBPs in five water and beverages samples. The system produced a linear response with a correlation coefficient greater than 0.999 from concentration range of 0.5-25 ppb for bromate and 0.5-100 ppb for chlorite and chlorate. This study demonstrated robust and reliable performance of the novel modular IC-MS for the determination of Oxyhalide DBPs in water and beverage.