Abstract: In an arrangement for producing a directional and cooled gas jet in an ion source with a gas inlet or a UV/fluorescence detection cell including a gas inlet, wherein a capillary extends with one end into the interior of the ion source which is evacuated, the one end is provided with a nozzle for discharging a gas sample into the ion source while being subjected to adiabatic cooling and the width of the nozzle opening is at most 40% of the inner diameter of the capillary and the capillary is heatable for preventing condensation of gas sample components in the nozzle.