Investigations On A Dielectric Barrier Discharge Optical Emission Spectrometric System For Bromide And Bromate Screening In Water Samples

Naturally, bromide widely presents in many water sources and some are used as drinking waters for human needs via disinfection process. Various by-products, e.g., brominated organic compounds and bromate, are prone to be formed during disinfection process of drinking water. Among these by-products, bromate is classified as a potential human carcinogen by the International Agency for Research on Cancer, whose maximum allowed concentration is limited at 10 μg L-1 in drinking water by China National Standard. As the precursor of bromate, the concentration of bromide in water has a significant impact on the quality of drinking water. Therefore, it is highly desired to provide a timely warning of possible pollution from bromide and bromate in environmental waters.Dielectric barrier discharge (DBD), which makes a high dielectric material (quartz, ceramic, glass, etc.) inserted between the two electrodes, can generate a stable and homogeneous gas discharge, when a high-frequency AC voltage is applied. As a low-temperature micro-plasma, DBD has many unique advantages, e.g., low power consumption, small size and simple configuration, which facilitate the miniaturization of analytical instruments. Recently, more attentions have been focused on the miniaturization of optical emission spectrometric (OES) system with DBD as a novel excitation source.Dielectric barrier discharge (DBD) at atmospheric pressure provides an efficient radiation source for the excitation of bromine and it is used for the first time for optical emission spectrometric (OES) detection of bromide and bromate. A portable DBD-OES system is developed for screening potential pollution from bromide and bromate in environmental waters. Bromide is on-line oxidized to bromine for in-situ generation ofvolatile bromine. Meanwhile, a helium stream carries bromine into the DBD micro-plasma for its excitation at a discharging voltage of 3.7 kV and optical emission spectrometric detection with a QE65000 charge-coupled device (CCD) spectrometer in the near-infrared spectral region. Similarly, the quantification of bromate is performed by its pre-reduction into bromide and then oxidized to bromine. The spectral characteristics and configuration of the DBD micro-plasma excitation source in addition to the oxidation vapor generation of bromine have been thoroughly investigated. With a sampling volume of 1 mL, a linear range of 0.05-10.0 mg L-1 is obtained with a detection limit of 0.014 mg L-1 by measuring the emission at 827 nm. A precision of 2.3% is achieved at 3 mg L-1 bromide. The system is validated by bromine detection in certified reference material of laver (GBW10023) at mg L-1 level, giving rise to satisfactory agreement. In addition, it is further demonstrated by screening trace bromide and bromate as well as spiking recoveries in a series of environmental water samples.