An ion guide chamber comprising a gas-tight elongate chamber, at least one first electrode for generating a field for transporting ions along the elongate chamber and at least one second electrode for generating a field for focusing ions within the elongate chamber. The elongate chamber, e. g. constituted by a glass tube, comprises a resistive structure extending substantially along a main axis of the chamber, whereas the first electrode is constituted by the resistive structure. Furthermore, the second electrode is arranged outside the elongate chamber. Having the RF electrodes arranged outside the vacuum chamber, provides a mechanically simple solution as well as insuring that contamination of the RF electrodes to the analyte gas cannot occur. This allows for a cost-saving design of the RF electrodes and with the corresponding voltages outside the chamber, preferably at atmospheric pressure or high vacuum, avoids discharges within the tube.