Using ultrapure water in ion chromatography to run analyses at the ng/L level

Stripping Voltammetry of Nanomolar Potassium and Ammonium Ions Using a Valinomycin-Doped Double-Polymer Electrode

“…The trace K + contamination originates from laboratory-purified water because no ITSV response to K + was observed when the blank solution of 0.5 mM H 2 SO 4 and 0.1 mM HCl was prepared using commercial ultrapure water (data not shown). In fact, the low-nanomolar K + contamination is hard to eliminate from purified water and is undetectable as a change in its resistivity (i.e., 18.2 MΩ·cm), which is limited by 0.1 μM H 3 O + and OH – with high mobility . Moreover, small ITSV peaks at ∼0.42 V (Figure A) indicate the contamination of laboratory-purified water with NH 4 + , which can originate from NH 3 in ambient air.…”

“…In fact, the low-nanomolar K + contamination is hard to eliminate from purified water 41 and is undetectable as a change in its resistivity (i.e., 18.2 MΩ•cm), which is limited by 0.1 μM H 3 O + and OH − with high mobility. 42 Moreover, small ITSV peaks at ∼0.42 V (Figure 4A) indicate the contamination of laboratory-purified water with NH 4 + , which can originate from NH 3 in ambient air.…”

Supplementary material to "Imprint of Arctic sea ice cover in North-Greenland ice cores"

“…for anions (F -, Cl -, SO4 2-, Br -, NO3and MSA) and a IonPac CS12A column for cations (Ca 2+ , Mg 2+ , K + , NH4 + and Na + ) measurements. Accuracy has been calculated as relative standard deviation (in %) of ionic species measured in Milli-Q © water collected during the B17 melting campaign and it is defined as:where σ is standard deviation and µ is the mean of concentration of ionic species I in Milli-Q © water.Similarly, precision has been calculated as the average of the relative standard deviation of ionic species measured in Milli-Q © water by Ion Chromatography and nominal values for Milli-Q © water reported in (Kano et al, 2004) and it is defined as:where n is the number of measurements, σ is again standard deviation and xi is the nominal concentration of the species i in Milli-Q © water as in (Kano et al, 2004).Overall reproducibility (precision) and accuracy are 0.05% and 0.01% RSD respectively, maintaining the sensitivity of the conductivity detector in the range of 0.2-0.5 nS·ng·g -1 , resulting in a Limit of Detection (LOD) between 0.07 and 0.1 ng·g -1 for most elements. Limit of Detection for each element has been calculated as in Hubaux & Vos (1970).…”

“…Similarly, precision has been calculated as the average of the relative standard deviation of ionic species measured in Milli-Q © water by Ion Chromatography and nominal values for Milli-Q © water reported in (Kano et al, 2004) and it is defined as:…”

“…where n is the number of measurements, σ is again standard deviation and xi is the nominal concentration of the species i in Milli-Q © water as in (Kano et al, 2004).…”