Ion chromatography determination of trace level bromate by large volume injection with conductivity and spectrophotometric detection after post column derivatisation.
Bromate is a well known by-product produced by the ozonisation of drinking water; the allowed concentration for human consumption has to be regulated to the low microg l(-1) range. A direct injection, ion chromatographic method was developed using a tetraborate eluent with serially connected conductivity and spectrophotometric detection. Bromate was detected after post-column reaction with fuchsin at 520 nm. Sample capacity was investigated by injecting large volumes (up to 6 ml) using a high total hardness and chloride tap water. Linear correlation of bromate response with volumes from 1 ml to 6 ml was demonstrated, the main limitation being the overlapping of the chloride peak with bromate. Up to 1.5 ml sample can be injected without any pre-treatment. With more than 1.5 ml injection volume, a sample pre-treatment with a cartridge in Ag and H form, followed by a 10 min degassing in an ultrasonic bath, was needed. This method was validated by analysing secondary reference materials and real samples from a drinking water treatment plant. The method was linear from the limit of quantification to 20 microg l(-1). Reproducibilities in tap water were 18% (5 microg l(-1), n=12) and 21% (1 microg l(-1), n=4) respectively for 1.5 and 6 ml injection volumes with conductivity detection, and 17% at 0.5 microg l(-1) (n=9) with spectrophotometric detection. Calculated detection limits were 0.5 microg l(-1) (6 ml) ahd 2 microg l(-1) (1.5 ml) for conductivity detection and 0.3 microg l(-1) (1.5 ml) for spectrophotometric detection.
Valsecchi
S
S
CNR-IRSA, Brugherio, Italy. valsecchi@server-mi.irsa.rm.cnr.it
Isernia
A
A
Polesello
S
S
Cavalli
S
S
D001959:Bromates / Q000032:analysis*; D002138:Calibration; D002254:Carbonates / Q000032:analysis; D002712:Chlorides / Q000032:analysis; D002852:Chromatography, Ion Exchange; D004553:Electric Conductivity; D010126:Ozone / Q000737:chemistry; D013053:Spectrophotometry; D014881:Water Supply / Q000032:analysis*
D001959:Bromates; D002254:Carbonates; D002712:Chlorides; D010126:Ozone