Photochemical vapor generation combined with headspace solid phase microextraction for determining mercury species by microwave-induced plasma optical emission spectrometry

A new and simple photochemical vapor generation (PCVG) technique utilizing UVC irradiation combined with headspace solid phase microextraction (HS SPME) is developed for the unified separation and preconcentration of mercury species followed by their determination through miniaturized thermal desorption argon microwaveinduced plasma optical emission spectrometry (TD-MIP-OES). Inorganic mercury (Hg2+), methylmercury, and ethylmercury are decomposed and reduced to mercury cold vapor in 2% formic acid through combined UVC irradiation and thermochemical reduction. The mercury vapor is subsequently liberated from the liquid phase and transported to the headspace. Without any tedious sample pretreatments, HS SPME using DVB/CAR/PDMS fiber affords clean and convenient one-step extraction followed by direct desorption into the injection port of the detection system. The 15 min-long UVC irradiation, thermal reduction of mercury species, and preconcentration of mercury vapor resulted in low limits of detection between 0.08 and 0.10 ng mL-1 for all mercury species. The method performance was validated by determining the total mercury and MeHg concentration in a tuna fish certified reference material (ERM CE464) and total mercury in sediment ERM CC580, and the results agreed well with the certified values.