A hyphenated technique for the determination of As ^III , As ^V , arsenobetaine (AsB), arsenocholine (AsC), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) has been developed by coupling an anion-exchange column to an inductively coupled plasma mass spectrometer, using an in-house developed thermospray nebulizer (TN) as an interface. Optimisation of the chromatographic conditions led to baseline separation of the signals from the six aforementioned compounds in approximately 10 min, using isocratic elution. Application of the TN offered a ten-fold improvement in sensitivity in comparison with the standard pneumatic nebulizer. To prevent clogging of the torch and to slow down deposit formation on the sampling cone, use was made of a second HPLC pump and a switching valve, allowing rinsing with HNO ₃ between two measurements. Detection limits were also improved and were in the range 0.04–0.12 µg l ^-1 as arsenic. Finally, the technique developed was used for the analysis of several mineral waters and urine samples. The improved sensitivity was also obtained for real samples. In the mineral waters analysed only As ^V could be detected. In the ten-fold diluted urine samples, all aforementioned arsenic compounds were present, except for AsC, which could not be detected.