Indoor Carbonyls

⏻ Learning Objectives

At the end of this lab you will be

able to collect air samples for analysis by offline techniques
able to explain the principle of operation of high performance liquid chromatography
able to interpret chromatograms in the context of instrument standards to separate, identify and quantify components in a mixture
able to contextualize the results using peer-reviewed studies

⌨ Prompt

The objective is to separate, identify, and quantify carbonyls in indoor and outdoor environments. You will sample carbonyls at an indoor location and an outdoor location in close proximity, e.g. inside an apartment and just outside. The samplers should be started and stopped at the same time. Sample for as close to 24 hours as possible. Record the actual start time and stop time and use the sampling duration in your analysis and not just the nominal 24 hours. You will decide and describe where the samples are collected. Indoor concentrations will likely be higher at a location that has new carpet, paint, furniture, etc. and where windows are typically closed. In your report, discuss your results in the context of commonly identified and quantified carbonyl compounds in indoor and outdoor environments reported in the literature.

You will be provided two DNPH cartridges in sealed pouches. Air is forced to flow through the cartridge with the help of a pump. Carbonyls present in the air are trapped and extracted at a later time for chemical analysis. Be sure to label the sample bags and keep track of the two cartridges; mixing up the indoor and outdoor samples would obviously negatively impact your results. Also be sure to remove the cap on the cartridge. The samplers are started simply by connecting the pump electrical leads to one of the batteries you are provided. After stopping the samplers at the end of 24 hours, remove the DNPH cartridges, return them to their pouches, and keep them in a refrigerator until returning to campus on Wednesday.

During lab on Wednesday, the instructors will assist you in eluting the carbonyls that are trapped on the cartridges using acetonitrile and then injecting the resulting solution into a high performance liquid chromatograph (HPLC) with UV/Vis detector. Discuss the methods and instrumentation with the instructors so that appropriate detail can be provided in your laboratory report, including the mobile and stationary phase, the mode of HPLC operation, and the mode of detection, and the appropriate instrument calibrations. Pay close attention to the instruction you are provided for using measurements of standards to relate the retention times (x-axis of the chromatogram) and intensities (y-axis) to the types and abundances of the set of carbonyl compounds present. You should report on both the relationship between indoor and outdoor concentrations and the health concerns associated with the concentrations of those detected at both locations.

Motivation

There is significant debate in the health and exposure community about the relative importance of indoor and outdoor air quality. While we most often think about emissions sources that directly impact outdoor air such as vehicle exhaust, industrial facilities, and wildfires, most of us spend much more time indoors than outdoors. Indoor air quality is influenced both by infiltration of outdoor air and by numerous indoor activities such as cooking and vacuuming, and numerous indoor emissions sources such as carpet, particle board, paint, cleaning products, and air fresheners. The relative importance of outdoor and indoor sources is impacted by individual preference and behavior (e.g., leaving windows open) and by increasingly common and effective energy savings measures incorporated in houses and buildings that reduce indoor/outdoor exchange of air. Carbonyls are one particular class of compounds that has garnered significant interest for indoor air quality. Several carbonyl compounds are known to pose significant health concerns when present at sufficiently high concentrations.

Indoor Carbonyls

Motivation

Resources