LIS 41 Study Summary

These tables summarize the measurements reported to the QA-SAC for the 41st Laboratory Intercomparison Study. A total of 78 laboratories reported measurements. Some measurements were missing or below the analytical detection limit (DL). N designates the number of reported values above the DL. Target values were provided by the reference laboratory. At the center of each set of N measurements is the Median or accepted target value of the set. Sigmas were estimated from the interquartile ranges and can be used to calculate Z-values. Half of the N measurements are within the 25th to 75th percentiles, which defines the range of Good measurements. Satisfactory measurements fall within the range defined by the Median ± Sigma. The limits for a measurement that Meets Data Quality Objectives are defined on page 4 of the Manual for the GAW Precipitation Chemistry Programme.

Email any questions you have to manager@qasac-americas.org.

Last update: February 4, 2012, 2:41 pm

Sample 1 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)		Satisfactory
(Median ±
Sigma)		Meets Data
Quality
Objectives
pH pH units 72 4.55 4.57 0.04 4.54 4.59 4.53 4.61 4.50 4.64
Conductivity μS/cm 68 20.4 20.1 1.4 18.9 20.7 18.7 21.4 18.7 21.4
Acidity (optional) μeq/L 7 N/A 28.5 17.4 24.0 47.6 11.1 45.9 21.4 35.6
Sulfate as SO42- mg/L 71 2.006 1.996 0.066 1.948 2.038 1.930 2.062 1.857 2.135
Nitrate as NO3- mg/L 73 1.964 1.960 0.050 1.919 1.986 1.910 2.010 1.823 2.097
Ammonium as NH4+ mg/L 69 0.555 0.545 0.027 0.529 0.566 0.518 0.572 0.507 0.583
Fluoride (optional) mg/L 25 0.101 0.098 0.010 0.094 0.107 0.088 0.108 N/A N/A
Chloride mg/L 71 0.330 0.315 0.017 0.303 0.327 0.298 0.332 0.284 0.346
Sodium mg/L 73 0.190 0.182 0.018 0.168 0.193 0.164 0.200 0.164 0.200
Potassium mg/L 65 0.044 0.044 0.009 0.038 0.050 0.035 0.053 0.036 0.052
Calcium mg/L 71 0.305 0.298 0.031 0.270 0.312 0.267 0.329 0.254 0.342
Magnesium mg/L 67 0.055 0.055 0.007 0.050 0.060 0.048 0.062 0.050 0.060

Sample 2 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)		Satisfactory
(Median ±
Sigma)		Meets Data
Quality
Objectives
pH pH units 72 4.84 4.85 0.06 4.81 4.89 4.79 4.91 4.78 4.92
Conductivity μS/cm 67 8.2 8.4 0.6 7.9 8.8 7.8 9.0 7.9 8.9
Acidity (optional) μeq/L 7 N/A 20.6 9.7 13.2 26.3 10.9 30.3 15.5 25.7
Sulfate as SO42- mg/L 71 0.683 0.679 0.045 0.653 0.715 0.634 0.724 0.632 0.726
Nitrate as NO3- mg/L 73 0.728 0.722 0.031 0.698 0.740 0.691 0.753 0.672 0.772
Ammonium as NH4+ mg/L 69 0.146 0.143 0.019 0.134 0.160 0.124 0.162 0.133 0.153
Fluoride (optional) mg/L 13 0.005 0.009 0.010 0.005 0.018 -0.001 0.019 N/A N/A
Chloride mg/L 63 0.069 0.070 0.012 0.063 0.080 0.058 0.082 0.063 0.077
Sodium mg/L 57 0.027 0.029 0.006 0.025 0.033 0.023 0.035 0.027 0.031
Potassium mg/L 47 0.012 0.015 0.006 0.011 0.020 0.009 0.021 0.012 0.018
Calcium mg/L 64 0.069 0.070 0.016 0.060 0.082 0.054 0.086 0.060 0.080
Magnesium mg/L 56 0.013 0.013 0.005 0.011 0.017 0.008 0.018 0.012 0.014

Sample 3 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)		Satisfactory
(Median ±
Sigma)		Meets Data
Quality
Objectives
pH pH units 72 4.55 4.56 0.05 4.52 4.60 4.51 4.61 4.49 4.63
Conductivity μS/cm 68 20.4 20.4 1.4 19.1 21.0 19.0 21.7 19.0 21.7
Acidity (optional) μeq/L 7 N/A 32.3 16.9 24.0 46.8 15.4 49.2 24.3 40.3
Sulfate as SO42- mg/L 71 2.006 2.004 0.080 1.941 2.049 1.924 2.084 1.864 2.144
Nitrate as NO3- mg/L 73 1.964 1.968 0.056 1.920 1.996 1.912 2.024 1.831 2.105
Ammonium as NH4+ mg/L 69 0.555 0.546 0.026 0.528 0.563 0.520 0.572 0.508 0.584
Fluoride (optional) mg/L 25 0.101 0.099 0.013 0.092 0.110 0.086 0.112 N/A N/A
Chloride mg/L 71 0.330 0.315 0.020 0.301 0.329 0.295 0.335 0.284 0.346
Sodium mg/L 72 0.190 0.187 0.020 0.171 0.198 0.167 0.207 0.169 0.205
Potassium mg/L 65 0.044 0.043 0.008 0.039 0.050 0.035 0.051 0.035 0.051
Calcium mg/L 70 0.305 0.297 0.026 0.279 0.315 0.270 0.323 0.253 0.340
Magnesium mg/L 66 0.055 0.055 0.006 0.050 0.059 0.049 0.061 0.050 0.060