Revised vapor diffusion coefficients and an improved ion chromatography method for detecting acetic and formic acid vapors

摘要

Museums are continually working to preserve their collections for future generations. Preventive conservation measures begin with air quality monitoring in galleries, display cases, and storage facilities to quantify levels of pollutants potentially harmful to the collections. Other measures include identifying the composition of museum artifacts and specimens for determining optimal storage conditions, potential cleaning methods, and susceptibility to corrosion and degradation. This dissertation reports an improved ion chromatography (IC) quantification method and revised vapor diffusion coefficients for acetic and formic acids for air quality monitoring, identifies harmful pollutant levels within a local museum, identifies corrosion products on museum specimens and identifies components of new artists' materials.;We report development of a rapid IC method with 2 to 60-fold improvement in detection limits for acetate and formate. Baseline resolution is achieved in 4.5 min using an AS11-HC anion exchange column with 4 mM NaOH eluent at 1.5 mL/min flow rate. The detection limits are 12 microg/mL (0.24 ng) for acetate and 11 microg/mL (0.21 ng) for formate.;An environmental monitoring study was conducted at the Natural History Museum of Los Angeles County using passive samplers and the improved IC method. Elevated levels of acetic and formic acid were found within the collection and suggestions were made to reduce acid levels and protect the collection from further damage. Additionally, efflorescence from affected fossils was analyzed using x-ray diffraction, infrared spectroscopy, and a newly developed IC method with excellent separation of acetate, formate and seven standard inorganic anions. Identified efflorescence includes calclacite, thecotrichite, calcium formate, sodium acetate, and coquimbite.;A revised model is presented to more accurately calculate acetic and formic acid vapors generated from acid solutions using a combination of modified Raoult's law and vapor-liquid equilibrium theory. The new model was validated experimentally using headspace gas chromatography-mass spectrometry. The model was used in conjunction with passive sampling to experimentally determine acetic and formic acid vapor diffusion coefficients. The revised diffusion coefficients are 0.126 cm2/s for acetic acid and 0.110 cm 2/s for formic acid. Acetic acid is 13% higher and formic acid is 13% lower than experimentally determined literature values. The presented model can be used to experimentally determine vapor diffusion coefficients for other polar compounds.;A preliminary investigation was conduced to identify the constituents and basic properties of two new artists' acrylic dispersion paints, Golden OPEN acrylics and Winsor & Newton Artists' Acrylics. A selected group of colors has been analyzed for polymer and pigment content, water-extractable materials and other basic properties such as gloss and the migration of materials to the paint surface. The preliminary results indicate that both brands incorporated 2-ethylhexyl acrylate into the binding medium polymer that was previously poly(n-butyl acrylate/ methyl methacrylate).