Lab-on-a-chip device to quantify buffer capacity of blood

An accurate estimation of physiological buffer capacity and total titratable buffer concentration of blood can give a great deal of insight into the physiological stability of a patient and yet it remains an undervalued diagnostic marker. This thesis highlights the need for a lab-on-chip device to quantify buffer capacity of whole blood samples by estimating the total titratable buffer concentration. Buffer capacity is quantified by titrating the buffer to its end point using monoprotic acids. More sophisticated ways include electrolytic titration, i.e. producing a proton flux using electrodes in a controlled environment. This thesis looks at a novel approach to electrolytic (coulometric) titration by inhibiting the production of OH ions during electrolysis and titrating the sample due to the proton flux from the anode. By definition, is the amount of acid or base added to change the pH of 1 litre of buffer by 1 pH unit. The carbonic acid bicarbonate buffer system is the most important buffer that maintains the body’s pH within a stable range. To quantify this buffer’s total buffering concentration, it is important to know and indicate its titration end point which signifies the total exhaustion of all buffering constituents. Colorimetric indicators have been used to indicate this end point which can be quantified through cameras or spectrophotometric techniques. Using this novel coulometric titrator and the colorimetric end point detector, this thesis presents a portable lab-on-chip prototype to spectrophotometrically quantify total titratable buffer concentration. Clinically, this device could benefit patients with sickle cell disease, nephritic disease and those admitted in accident and emergency wards. This research work is aimed at presenting a proof-of-concept for a device that can titrate nano-litre samples and be able to detect the end point of a titration in a controlled way.Open Acces

A Study comparing the moisture barrier characteristics of flat liners versus stoppers in continuous thread closures on glass viles

The combination of glass vial, elastomeric stopper, and aluminum crimp seal represents one of the principal packaging systems used to package diagnostic reagents, ophthalmic and veterinary medicines, and pharmaceutical products. This work states that elastomeric flat liners are an alternative to traditional stoppers. To confirm this position, several comparative moisture transmission evaluations are conducted to contrast the barrier performance of glued flat liners against stoppers in continuous thread closures on glass vials. After a review of several standard packaging integrity testing methods, this thesis demonstrates the use of coulometric titration as an alternative package system testing methodology. Coulometric titrators are commercially available, and coulometric titration is well established as a precise moisture determination method for determining the micro-moisture contents in both solid and liquid products. The accuracy of coulometric titration technique is well suited for discerning the slight changes in moisture content of hygroscopic products after being packaged in candidate high moisture barrier packaging systems

Curriculum Development for Water Chemistry Analysis

The goal of this project was to support the creation of a water chemistry analysis module for high school students that catered to various learning styles. To realize this goal, we researched educational programs, determined successful educational elements, and developed alternative learning modules. The project resulted in the development of a three-day curriculum that includes an introduction to the topic, videos demonstrating water chemistry tests, a workbook with procedures, and recommendations for data analysis and reflection. This project was sponsored by the National Park Service at Rock Creek Park and was co-developed with Montgomery County Public Schools and the Audubon Naturalist Society

Investigation of Pulsed Electrolysis for Hypochlorous Acid Production

Because of the Covid-19 pandemic along with the delay in the worldwide supply chain, there were disinfectant shortages that lasted for weeks around the world. Therefore, on-site production is a promising solution to satisfy the increasing demand. As more and more people are shifting toward safer and more environmentally friendly products, we are interested in investigating the electrolysis of sodium chloride (NaCl) solution to produce hypochlorous acid (HOCl). Electrolysis is inexpensive as it requires only sodium chloride and electricity, and it does not have any negative impact on the environment. Moreover, electrolysis can be coupled with renewable energy to utilize the excess energy that is hard to store. Meanwhile, hypochlorous acid was proven to be 80-100 times more effective than sodium hypochlorite, commonly known as bleach. Hypochlorous acid was also shown to be a non-toxic, anti-inflammatory, and non-corrosive disinfectant. Since electrolysis is an energy-intensive process, this project will study if using a pulsed direct current to perform electrolysis can improve the current efficiency or electricity requirements of the process. There was evidence showing that pulsed electrolysis was able to improve the electrolysis efficiency because of the reduction of bubbles coverage, perturbation of the electrical double layer, and enhancement of mass transportation. A flow-through reactor was made with a cathode made from titanium and an anode made from titanium coated with mixed metal oxide (a mixture of Iridium oxide and Tantalum oxide). The squared-shaped pulsed current was generated by utilizing MOSFET. The results showed that pulsed electrolysis increased the number of electrons converted into final products up to 10% more. Pulsed electrolysis also reduced the electricity requirement by 10%-15%. However, it significantly increased the need for sodium chloride because there was no reaction during the off-time. There are several proposed methods to minimize this disadvantage, but more experiments need to be done to assess them. Nevertheless, in the current density range from 2000 to 4500 A/m2, for the same amount of supplied power, pulsed electrolysis with a duty cycle of 80% required less sodium chloride to produce 1 kg of Cl2 than conventional constant electrolysis. Although frequency only affected the electrolysis efficiency slightly, operating at the optimized frequency extended the improvement of the pulsed electrolysis compared to the constant electrolysis. Utilizing pulsed electrolysis with the optimized settings can effectively decrease the operating cost of producing disinfectant (hypochlorous acid)

Environmental Behavior of Hafnium: the Impact on the Disposition of Weapons-Grade Plutonium

Experimental and analytical studies were performed to examine the environmental behavior of hafnium and its utility as a neutron poison for the disposition of weapons-grade plutonium in Yucca Mountain. The hydrolysis of hafnium was investigated by potentiometric titration in solutions of varying ionic strength to determine the stability constants for the first four monomeric hydrolysis products. The specific ion interaction theory is used to extrapolate these results to infinite dilution. The solubility of hafnium hydroxide and a meta-stable hafnium carbonate solid phase are studied via solubility experiments using ICP-AES. An upper bound for the stability constant of the first carbonate complex is determined. The solubility of hafnium oxide is investigated via solubility experiments using neutron activation analysis, which is also used to investigate the complexation of hafnium by silicates. The potential for a near field criticality incident resulting from the disposition of weapons-grade plutonium at Yucca Mountain is examined using two integrated chemistry and transport models, which are then fed into an MCNP model of the near field at the Yucca Mountain repository. These models are used to predict the effective neutron multiplication factor for the system as the waste package degrades over time. Using the integrated degradation and criticality models, the long term criticality behavior of the proposed WGPu host phase ceramic is examined, as well as the utility of hafnium as a criticality control element for the disposition of weapons-grade plutonium

Characterisation of Microparticle Waste from Dental Resin-Based Composites

Clinical applications of resin-based composite (RBC) generate environmental pollution in the form of microparticulate waste. Methods: SEM, particle size and specific surface area analysis, FT-IR and potentiometric titrations were used to characterise microparticles arising from grinding commercial and control RBCs as a function of time, at time of generation and after 12 months ageing in water. The RBCs were tested in two states: (i) direct-placement materials polymerised to simulate routine clinical use and (ii) pre-polymerised CAD/CAM ingots milled using CAD/CAM technology. Results: The maximum specific surface area of the direct-placement commercial RBC was seen after 360 s of agitation and was 1290 m2/kg compared with 1017 m2/kg for the control material. The median diameter of the direct-placement commercial RBC was 6.39 μm at 360 s ag-itation and 9.55 μm for the control material. FTIR analysis confirmed that microparticles were sufficiently unique to be identified after 12 months ageing and consistent alteration of the outermost surfaces of particles was observed. Protonation-deprotonation behaviour and the pH of zero proton charge (pHzpc) ≈ 5–6 indicated that the particles are negatively charged at neutral pH7. Conclusion: The large surface area of RBC microparticles allows elution of constituent monomers with potential environmental impacts. Characterisation of this waste is key to understanding potential mitigation strategies

Biosorption of uranium and its effect on uranium transport in groundewater

In past years, microbial reduction has been explored as a remediation method for uranium-contaminated groundwater at U.S. Department of Energy sites with promising results. Although transport models have been improved to include variations in geochemical concentrations, reductive microbial processes, and adsorption of uranium to minerals, they do not incorporate the presence of microorganisms as sorption sites that may influence the overall transport of uranium. The main objective of this research was to determine the effects of uranium biosorption on the overall transport of uranium by understanding the solution chemical equilibrium and its effects on modeling sorption. This was done by first evaluating the uncertainty associated with uranium equilibrium speciation and its effect on the prediction of uranium sorption to minerals. Then, the partition coefficient between U(VI) and the microbial species Geobacter uraniireducens and Acholeplasma palmae were experimentally determined. The experimentally obtained partition coefficients were used to incorporate biosorption into a thermodynamic model that describes the distribution of uranium in a system with microorganisms available as sorption sites. When considering mineral adsorption equilibrium, modeling predictions were robust with respect to adsorbed U(VI) concentration, as indicated by the resulting normal Gaussian distributions. Modeling predictions also indicated the amplification of uncertainty with background levels of total U(VI) and higher estimates of input uncertainty (spatial and temporal variability), as indicated by the resulting bi-modal Gaussian distributions. Experimental results indicate that U(VI) sorbs more strongly, approximately 300 times, to G. uraniireducens under low-dissolved inorganic carbon (DIC) conditions and decreases as DIC increases. Under low-DIC conditions, the KD obtained for uranium sorption to G. uraniireducens is 7985 ± 1024 L kg-1, which is larger than the KD of 1850 ± 1.8 L kg-1 determined for uranium sorption to the surface of A. palmae. Beamline analysis on sorption tests with G. uraniireducens detected reduction had occurred in these experiments without the addition of an external electron source, indicating that the obtained KD values are overestimated for G. uraniireducens. While the partition coefficients of the bacteria in high-DIC waters are comparable to reported U(VI)- mineral sorption, when combined with the bacterial concentration during and after remediation, the amount of uranium sorbed to the microorganisms is not large enough to produce a noticeable effect on the transport of uranium in a bioremediated aquifer. Finally, the reactions that describe sorption as captured by the experimentally obtained partition coefficients were best described by the sorptive site reacting with uranium and one or two carbonate groups

Soil, grain and water chemistry and human selenium imbalances in Enshi district, Hubei Province, China

Many elements which are essential to human and other animal health in small doses can be toxic if ingested in excess. Selenium (Se), a naturally occurring metalloid element is found in all natural materials on earth including rocks, soils, waters, air, plant and animal tissues. Since the early 1930’s, it has been recognised that Se toxicity causes hoof disorders and hair loss in livestock. Se was also identified as an essential trace element to humans and other animals in the late 1950’s. It forms a vital constituent of the biologically important enzyme glutathione peroxidase which acts as an anti-oxidant preventing cell degeneration. Se deficiency has been implicated in the aetiology of several diseases including cancer, muscular dystrophy, muscular sclerosis and cystic fibrosis. Se can be assimilated in humans through several pathways including food, drinking water and inhalation of Se-bearing particles from the atmosphere. In the majority of situations, food is the most important source of Se, as levels in water are very low. The narrow range between deficiency levels (<40 pg per day) and toxic levels in susceptible people (> 900 pg per day) makes it necessary to carefully control the amount of Se in the diet. In China, Se deficiency has been linked to an endemic degenerative heart disease known as Keshan Disease (KD) and an endemic osteoarthropathy which causes deformity of affected joints, known as Kaschin-Beck Disease. These diseases occur in a geographic belt stretching from Heilongjiang Province in north-east China to Yunnan Province in the south-west. In the period between 1959 and 1970, peak KD incidence rates exceeded 40 per 100 000 (approximately 8500 cases per annum) with 1400 - 3000 deaths recorded each year. Incidence rates have since fallen to less than 5 per 100 000 with approximately 1000 new cases reported annually (Levander, 1986). Se toxicity (selenosis) resulting in hair and nail loss and disorders of the nervous system in the human population, has also been recorded in Enshi District, Hubei Province and in Ziyang County, Shanxi Province. China possesses one of the best epidemiological databases in the world on Se-related diseases which has been used in conjunction with geochemical data to demonstrate a significant geochemical control on human Se exposure. However, the precise geographical areas at risk and the geochemical controls on selenium availability have yet to be established