Syringes are the most expensive consumables for analyses in the Liquid Water Isotope Analyser using commercial Cavity Ring-Down Spectroscopy (CRDS) systems. Our experience shows that although the syringe life significantly varies, it is not an exception that a syringe performs many thousands of injections. A simple maintenance procedure consisting of replacing the syringes two times per day and keeping them in the deionised water resulted in an average syringe life of over 3500 injections. Number of injections per sample affects the between-sample memory effect and the cost of the analysis (duration, energy, consumption of syringes). We studied the influence of the number of injections (six and nine) on the final δ(18)O and δ(2)H values using two sets of samples covering the ranges of isotopic composition typical for the natural waters of the highest part of the Carpathians (streams, springs, soil water and precipitation). The differences in the final δ-values between nine and six injections were within 0.1 ‰ for δ(18)O and 1.0 ‰ for δ(2)H for the Picarro 2120i and 2130i CRDS systems.
Keywords: Hydrogen-2; LIMS for lasers; isotope measurements; laser spectroscopy; memory effect; methods and equipment; number of injections; oxygen-18; syringe life; water.