Date of Award

Spring 5-7-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Carl Tripp

Second Committee Member

Alice Bruce

Third Committee Member

Mitchell Bruce

Additional Committee Members

Brian Frederick

Doug Bousfield

Abstract

Karl Fischer Titration (KFT) is the “gold standard” method for measuring the amount of water in oils. KFT is a laborious and time-consuming method that requires expensive and hazardous chemicals which has provided the impetus to develop alternative methods. In this thesis, we investigated three approaches for determining water content in oils that are based on the use of infrared spectroscopy. In the first approach, we developed a simple method for measuring water concentrations from 1 to 5000 ppm in various types of oil that uses no hazardous, and expensive, chemical reagents or matrix specific calibrations. This approach involves capturing the water from the oil on an infrared transparent membrane and then recording an IR spectrum in transmission mode through the membrane. The second approach involves adding CaO powder to an oil sample and measuring the amount of Ca(OH)2 produced by the reaction of CaO with water. The Ca(OH)2 particles was collected on an infrared transparent membrane for analysis by infrared spectroscopy. No calibration is required and the amount of water is determined from measuring the intensity of the OH stretching mode of Ca(OH)2 at 3645 cm-1. The third approach is based on adding CuSO4 to the oil and forms copper sulfate monohydrate after reacting with water. The CuSO4·H2O particles are collected by passing a known volume of oil through the membrane and measuring the intensity of the bending mode of the water band at 1743 cm-1. All three methods achieved high accuracy and precision when compared to KFT over a linear range of 1 ppm to 10000 ppm. These were achieved by overcoming problems from light scattering by the water droplets, as well as the distortions in the water bands due to interactions of the water with the oil that occur when measuring water levels using transmission in a fixed pathlength liquid cell, as described in the ASTM standard practice E2412 method. Our recommendation and preference is the CaO method because it does not require a cooling stage, that is used in the membrane method, and can be used with a wider range of oils than what is possible with CuSO4·H2O.

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