You are encouraged to attend the defence. The details of the defence and attendance information is included below:  

Date: February 14, 2025
Time: 2:00 PM to 4:00 PM (PT)

Defence mode: Hybrid
In-Person Attendance: Senate Chambers, UNBC Prince George Campus
Virtual Attendance: via Zoom 

LINK TO JOIN: Please contact the Office of Graduate Administration for information regarding remote attendance for online defences. 

To ensure the defence proceeds with no interruptions, please mute your audio and video on entry and do not inadvertently share your screen. The meeting will be locked to entry 5 minutes after it begins: please ensure you are on time.

Thesis entitled: DEVELOPING A SEQUENTIAL ANALYTICAL PROCEDURE FOR EVALUATING CHROMIUM(III) AND CHROMIUM(VI) SPECIATION AND THEIR DIFFERENTIAL SOLUBILITIES FROM AIR SAMPLES

Abstract: Workplace exposure to chromium species presents significant health risks, yet current standardized analytical methods lack the sensitivity to detect at the required detection limits to meet the threshold limit values (TLV®) and require multiple samples to quantify different chromium species, increasing both cost and complexity. A novel sequential analytical procedure was developed for the quantification of soluble Cr(III), soluble Cr(VI), and insoluble chromium species from a single air sample using Disposable Inhalable Samplers (DIS)s. The method combines ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) with EPA Method 6800 speciated isotope dilution mass spectrometry (SIDMS) to enable precise quantification and correction of species interconversion. An insoluble chromium microwave digestion method was developed using nitric acid, sulfuric acid, and hydrogen peroxide for difficult-to-digest chromium oxides.

Method validation demonstrated detection limits below 0.03 × TLV for soluble chromium species and insoluble chromium. The use of EPA 6800 SIDMS improved method precision for soluble species, with recoveries of 99-109% for Cr(VI) at concentrations ranging from 0.1 to 2 × TLV. The standalone insoluble chromium digestion achieved 90-105% recovery across all concentration levels. Matrix effect studies revealed that soluble iron(III) (Fe(III)) reduced Cr(VI) recoveries to 52-64%, but this interference could be corrected using isotope dilution techniques.

The sequential procedure showed promising results but indicated potential losses during filtration, with insoluble chromium recoveries of 75-80%. This work provides a foundation for chromium speciation analysis that meets current ACGIH exposure limit requirements while reducing analytical costs by eliminating the need for multiple samples.

Defence Committee:  
Chair: Dr. Thomas Tannert, University of Northern British Columbia  
Supervisor: Dr. Hossein Kazemian, University of Northern British Columbia  
Committee Member: Dr. Kerry Reimer, University of Northern British Columbia  
Committee Member: Dr. Martin Harper, University of Florida
External Examiner: Dr. Kevin Ashley, USA Centers for Disease Control and Prevention