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
| Measurement | Units | N | Target | Median | Sigmaest. | 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
| Measurement | Units | N | Target | Median | Sigmaest. | 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
| Measurement | Units | N | Target | Median | Sigmaest. | 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 |
