LIS 45 Study Summary

These tables summarize the measurements reported to the QA-SAC for the 45th 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: April 23, 2012, 10:52 am

Sample 1 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 69 4.68 4.71 0.06 4.67 4.76 4.65 4.77 4.64 4.78
Conductivity μS/cm 65 22.0 21.7 1.2 20.7 22.3 20.5 22.9 20.2 23.2
Acidity (optional) μeq/L 8 N/A 21.3 9.9 17.5 30.8 11.4 31.1 16.0 26.5
Sulfate as SO42- mg/L 69 2.435 2.436 0.118 2.363 2.522 2.318 2.554 2.266 2.606
Nitrate as NO3- mg/L 73 1.230 1.213 0.047 1.176 1.240 1.166 1.260 1.129 1.297
Ammonium as NH4+ mg/L 70 0.447 0.452 0.026 0.437 0.471 0.426 0.477 0.420 0.483
Fluoride (optional) mg/L 17 0.020 0.021 0.006 0.016 0.024 0.015 0.027 N/A N/A
Chloride mg/L 68 1.620 1.600 0.048 1.566 1.632 1.552 1.648 1.440 1.760
Sodium mg/L 68 1.035 1.019 0.048 0.991 1.056 0.971 1.067 0.918 1.120
Potassium mg/L 64 0.183 0.180 0.013 0.170 0.187 0.167 0.193 0.144 0.216
Calcium mg/L 67 0.240 0.239 0.026 0.220 0.256 0.213 0.265 0.204 0.274
Magnesium mg/L 66 0.123 0.120 0.012 0.113 0.129 0.108 0.132 0.108 0.132

Sample 2 Results

MeasurementUnitsNTargetMedianSigmaest.Good
(25th to 75th
percentiles)
Satisfactory
(Median ±
Sigma)
Meets Data
Quality
Objectives
pH pH units 69 4.72 4.74 0.07 4.70 4.80 4.67 4.81 4.67 4.81
Conductivity μS/cm 65 11.5 11.8 1.0 10.8 12.2 10.8 12.8 11.0 12.6
Acidity (optional) μeq/L 8 N/A 18.8 8.8 15.8 27.8 10.0 27.6 14.1 23.5
Sulfate as SO42- mg/L 68 1.028 1.041 0.064 0.995 1.081 0.977 1.105 0.969 1.113
Nitrate as NO3- mg/L 73 1.107 1.117 0.051 1.077 1.146 1.066 1.168 1.039 1.195
Ammonium as NH4+ mg/L 70 0.210 0.211 0.017 0.203 0.227 0.194 0.228 0.197 0.225
Fluoride (optional) mg/L 19 0.020 0.020 0.006 0.017 0.026 0.014 0.026 N/A N/A
Chloride mg/L 67 0.120 0.120 0.021 0.112 0.141 0.099 0.141 0.108 0.132
Sodium mg/L 60 0.084 0.081 0.010 0.074 0.086 0.071 0.091 0.073 0.089
Potassium mg/L 56 0.031 0.031 0.008 0.025 0.036 0.023 0.039 0.025 0.037
Calcium mg/L 64 0.110 0.112 0.014 0.103 0.122 0.098 0.126 0.096 0.128
Magnesium mg/L 59 0.043 0.043 0.005 0.040 0.048 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 69 4.59 4.60 0.06 4.56 4.65 4.54 4.66 4.53 4.67
Conductivity μS/cm 65 38.4 37.9 2.0 36.3 39.0 35.9 39.9 35.3 40.5
Acidity (optional) μeq/L 8 N/A 28.1 11.6 23.1 38.7 16.5 39.7 21.1 35.1
Sulfate as SO42- mg/L 69 4.262 4.320 0.235 4.147 4.464 4.085 4.555 4.018 4.622
Nitrate as NO3- mg/L 72 2.148 2.145 0.091 2.077 2.200 2.054 2.236 1.995 2.295
Ammonium as NH4+ mg/L 69 0.775 0.778 0.058 0.740 0.818 0.720 0.836 0.724 0.832
Fluoride (optional) mg/L 23 0.100 0.097 0.014 0.085 0.105 0.083 0.111 N/A N/A
Chloride mg/L 67 3.591 3.593 0.118 3.530 3.690 3.475 3.711 3.234 3.952
Sodium mg/L 67 2.301 2.312 0.095 2.236 2.365 2.217 2.407 2.081 2.543
Potassium mg/L 67 0.390 0.390 0.025 0.368 0.403 0.365 0.415 0.312 0.468
Calcium mg/L 68 0.623 0.612 0.037 0.583 0.633 0.575 0.649 0.521 0.703
Magnesium mg/L 66 0.248 0.248 0.013 0.238 0.256 0.235 0.260 0.223 0.272