LIS 56 Study Summary

These tables summarize the measurements reported to the QA-SAC for the 56th Laboratory Intercomparison Study. A total of 81 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: June 23, 2017, 1:14 pm

Sample 1 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 75 4.97 4.98 0.06 4.94 5.03 4.92 5.04 4.91 5.05
Conductivity μS/cm 69 6.2 6.7 0.4 6.3 6.9 6.3 7.1 6.3 7.1
Acidity (optional) μeq/L 11 N/A 12.0 5.5 9.3 16.8 6.5 17.5 9.0 15.0
Sulfate as SO42- mg/L 67 0.529 0.528 0.040 0.507 0.561 0.488 0.568 0.492 0.564
Nitrate as NO3- mg/L 76 0.537 0.533 0.028 0.516 0.554 0.504 0.561 0.496 0.569
Ammonium as NH4+ mg/L 71 0.107 0.108 0.009 0.101 0.114 0.099 0.117 0.101 0.115
Fluoride (optional) mg/L 20 0.005 0.006 0.007 0.004 0.012 0.000 0.012 N/A N/A
Chloride mg/L 64 0.071 0.070 0.007 0.066 0.076 0.063 0.077 0.063 0.077
Sodium mg/L 60 0.036 0.037 0.006 0.034 0.042 0.031 0.043 0.034 0.040
Potassium mg/L 55 0.019 0.019 0.011 0.016 0.031 0.008 0.030 0.016 0.022
Calcium mg/L 60 0.050 0.050 0.014 0.044 0.063 0.036 0.064 0.043 0.057
Magnesium mg/L 56 0.015 0.017 0.008 0.014 0.026 0.008 0.025 0.015 0.018

Sample 2 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 75 4.73 4.77 0.06 4.73 4.82 4.71 4.83 4.70 4.84
Conductivity μS/cm 69 11.3 11.2 0.5 10.8 11.5 10.7 11.7 10.5 11.9
Acidity (optional) μeq/L 11 N/A 18.0 5.9 15.0 23.0 12.1 23.9 13.5 22.5
Sulfate as SO42- mg/L 71 1.025 1.000 0.051 0.974 1.043 0.949 1.051 0.930 1.070
Nitrate as NO3- mg/L 76 1.058 1.038 0.050 1.006 1.073 0.987 1.088 0.965 1.110
Ammonium as NH4+ mg/L 77 0.208 0.203 0.015 0.191 0.212 0.188 0.218 0.189 0.217
Fluoride (optional) mg/L 25 0.020 0.019 0.002 0.016 0.020 0.017 0.021 N/A N/A
Chloride mg/L 70 0.117 0.116 0.009 0.110 0.123 0.107 0.125 0.105 0.127
Sodium mg/L 63 0.078 0.079 0.008 0.075 0.086 0.071 0.087 0.072 0.086
Potassium mg/L 61 0.031 0.031 0.011 0.028 0.043 0.020 0.042 0.025 0.037
Calcium mg/L 67 0.108 0.109 0.016 0.095 0.117 0.093 0.125 0.093 0.125
Magnesium mg/L 63 0.042 0.043 0.005 0.040 0.047 0.038 0.048 0.039 0.047

Sample 3 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 75 5.35 5.28 0.10 5.20 5.34 5.18 5.38 5.21 5.35
Conductivity μS/cm 69 7.5 7.8 0.4 7.6 8.2 7.4 8.2 7.3 8.3
Acidity (optional) μeq/L 11 N/A 10.0 11.1 5.0 20.0 0.0 21.1 7.5 12.5
Sulfate as SO42- mg/L 70 0.906 0.897 0.052 0.863 0.933 0.845 0.948 0.834 0.959
Nitrate as NO3- mg/L 76 1.019 1.004 0.044 0.972 1.031 0.960 1.048 0.934 1.074
Ammonium as NH4+ mg/L 76 0.392 0.379 0.026 0.361 0.396 0.352 0.405 0.353 0.404
Fluoride (optional) mg/L 26 0.050 0.045 0.007 0.039 0.049 0.038 0.052 N/A N/A
Chloride mg/L 72 0.188 0.184 0.014 0.176 0.194 0.170 0.198 0.166 0.202
Sodium mg/L 64 0.099 0.098 0.008 0.092 0.103 0.090 0.106 0.089 0.107
Potassium mg/L 61 0.035 0.033 0.009 0.029 0.041 0.024 0.042 0.027 0.039
Calcium mg/L 67 0.199 0.197 0.028 0.172 0.210 0.169 0.225 0.168 0.226
Magnesium mg/L 62 0.039 0.040 0.005 0.037 0.045 0.035 0.045 0.036 0.044