Lab Instruments and Precision and Accuracy

Here we show you images of the instruments used for teaching and research. We use lab protocols, quality assurance and quality control techniques derived from standard methods and EPA protocols for regulated materials. Specialized training on an instrument can be arranged, if necessary, plus Williams College researchers can reserve a particular instrument for lab on our Equipment Signup page.

Instrument Precision and Accuracy

Analysis Instrument Detection limit Run Precision
Calcium (Ca+2) Perkin-elmer PinAAcle 900H 0.49 µeq/L 0.19 %RSD
Magnesium (Mg+2) Perkin-elmer PinAAcle 900H 0.41 µeq/L 0.53 %RSD
Sodium (Na+) Perkin-elmer PinAAcle 900H 0.43 µeq/L 0.55 %RSD
Potassium (K+) Perkin-elmer PinAAcle 900H 0.26 µeq/L 0.78 %RSD
Ammonium (NH4+) Technicon Auto-analyzer II 0.56 µeq/L 2.64 %RSD
Silica (SiO2) Technicon Auto-analyzer II 0.33 µeq/L 1.46 %RSD
Chloride (Cl-) Metrohm 883/863 IC 0.57 µeq/L 0.28 %RSD
Nitrate (NO3-) Metrohm 883/863 IC 0.16 µeq/L 0.10 %RSD
Phosphate (HPO4-3) Metrohm 883/863 IC 0.21 µeq/L 0.16 %RSD
Sulfate (SO4-2) Metrohm 883/863 IC 0.21 µeq/L 0.18 %RSD
pH Radiometer Analytical TIM840 pH 2 to 12 pH 2 + 0.02 to pH 12 + 0.12
Alkalinity by auto-titrator Radiometer Analytical TIM840 0.16 µeq/L 0.45 %RSD

Notes about data quality: Most samples are analyzed 2 to 4 times but there are still anomalies in the data that should be carefully evaluated. Sample charge balance is used as the initial screen. For individual ions, quality control and quality assurance are performed with commercial standard reference standards and using intra-laboratory comparisons. The standard reference materials are used as a single-blind setup until after results obtained. Using archived samples as intra-laboratory comparisons assures researchers of reproducibility and statistical replication.