What is the Traceability of Water to the SI?

1. What is the Traceability of Water to the SI? The measurement of water Marlene Moore Advanced Systems, Inc. mmoore@advancedsys.com

2. Objective • Present perspectives on Metrological Traceability of Water • Provide background on regulatory science versus theoretical science • Testing and Calibration aspects related to Water

3. Traceability of Water • Not possible unless you are talking about water sources • Where does my water come from? • Sources: River, groundwater, ocean, surface water, etc….. • These are not SI but we can trace the water….

4. Traceability of Water • When measuring water our first question is: • What will the water be used for? • Knowing the answer will define the measurement requirements: • Drinking water : 40 CFR Part 141 • Wastewater: 40 CFR Part 136 • Reagent Water used in testing: ASTM D1193 • Purified Water : USP <645> • Bottled Water, Cleaning Water, etc….

5. Traceability of Water • Water - Used everywhere – but little understood • When measuring water: • Specification related to the use of the water in a process or activity. (drinking water, treatment, manufacturing, processes, etc.) • Looking for impurities that affect the water • Measuring a characteristic of the water that is an industry standard for defining the quality – often quick and easy measurement…

6. Traceability of Water • Therefore… • We are looking at a measurand: • -- define a concentration or amount of a contaminant or substance in the water • -- the amount is NOT traceable to the SI in the pure sense, but is traceable to a reference material that has been defined as suitable for that use

7. Regulatory Science • FDA, EPA, Nuclear Commission, state, local and industry have specifications for water • These specifications require measurements to determine if the water can be used for a specific application (e.g. drinking, pharmaceutical, nuclear, etc.) • The specification requires a measurement using a specific reference material, method and controls • MOST OFTEN NOT WRITTEN IN METROLOGICAL TERMS! • Results in confusion and misunderstandings

8. Testing NOT Calibration of Water • Therefore we are testing water not calibrating water. • When we perform testing of water we are looking for traceability to the SI of the measurement or measurand. • Conductivity in treated, process or drinking water • pH – Harned Cell – IUPAC convention – • Primary method traceability not SI • Total Organic Carbon (TOC) – Reference material • Potassium hydrogen phthalate, (KHP) • NO NIST SRM for TOC

9. Testing • Calibration is part of the testing performed. Calibration is performed just prior to the testing and includes Quality Control to verify no significant drift or problems occurred during testing • Equipment Servicing confused with calibration • Most regulatory programs may require calibration 1/year • Default from older units where failure more common • Calibration of the meter without the probe has been observed and therefore the calibration is not performed to the measurand (conductivity, pH) • Calibration TOC is defined by the test method traceability is to the method and RM. • Instrument calibration to mfg specs - a problem

10. Summary • Testing labs and calibration labs must understand the reason for the measurement. • When measuring water to specifications you are most often testing with calibration being part of the process. • The calibration is often an insignificant or minor contributor to the overall process. (After all other influence quantities have been controlled)