Use of the Operational Air Quality Monitor (AQM) for In-Flight Water Testing Project

<p>Currently, the Air Quality Monitor (AQM) on-board ISS provides specific information for a number of target compounds in the air. However, there is a significant subset of common target compounds between air and water.&nbsp; Naturally, the following question arises, &ldquo;Can the AQM be used for both air and water quality monitoring?&rdquo;&nbsp; Previous directorate-level IR&amp;D funding led to the development of a water sample introduction method for mass spectrometry using electro-thermal vaporization (ETV).&nbsp; This vaporization source allows analytes in water samples to enter the gas phase, where they can be analyzed using a variety of techniques.&nbsp; This project will focus on the integration of the ETV with a ground-based AQM.&nbsp; The capabilities of this integrated platform will be evaluated using a subset of toxicologically important compounds.</p><p>The ETV unit was constructed using two glass tubes and a nichrome ribbon powered by a programmable DC power supply (G W Instec, PSM-3004).&nbsp; The nichrome ribbon was threaded through two 3-mm wide, 1-cm-long slot cuts on the inner tube placed 1.5 cm past the inlet.&nbsp; The ribbon was held securely by compressing it between the inner tube and two halves of an outer glass tube.&nbsp; These halves were held together using a flexible metal clamp.&nbsp; Inside the inner tube the ribbon was slightly curved, and an indent (1 mm diameter) was made on its surface for depositing a measured liquid sample drop.&nbsp; The ribbon was positioned in the upper half of the inner tube in such a way that the edge of the ribbon faced the front (inlet) side of the ETV unit.&nbsp; Holes (1 mm diameter) were made on the outer and inner glass tubes for sample introduction and were aligned with the ribbon indent.</p><p>The viability of the ETV approach for the analysis of water analytes was demonstrated using a ground-based, laboratory scale analyzer (reference:&nbsp; Dwivedi, P. et al.&nbsp; &ldquo;Electro-Thermal Vaporization Direct Analysis in Real Time-Mass Spectrometry for Water Contaminant Analysis During Space Missions,&rdquo; Analytical Chemistry, 85, 9898-9906 (2013)).&nbsp; The work in this proposal will extend that effort and interface the ETV to a ground version of the current in-flight AQM.&nbsp; Liquid sample will be introduce via a pipet through the sample injection port and placed onto the nichrome ribbon heated to a set temperature by an external, programmable power supply.&nbsp; Upon vaporization of the water sample, the target analytes will be swept into the AQM Sample-In port using nitrogen carrier gas.&nbsp; A vapor-phase analysis can then be performed by the AQM to identify and quantify the target analytes in the water samples.&nbsp; Parameters to be optimized include water sample size, carrier gas sweep rate, and ribbon temperature.&nbsp; The operating parameters of the vapor-phase analysis performed by the AQM will also need to be modified for this type of sampling methodology.&nbsp; A simple two-position valve attached to the ETV and a diverter tube will allow for manual selection of either a water sample through the ETV or an air sample through the diverter tube.&nbsp; The primary objective of this effort is to evaluate the viability of the ETV with ground-based, flight hardware.&nbsp; A proof-of-concept unit capable of water and air analysis utilizing the ETV will be developed.&nbsp; The target water analytes to be used in this work will come from a list provided by the water SMEs in the Toxicology and Environmental Chemistry Laboratories at JSC.&nbsp; These analytes are commonly observed in the ground analysis of water samples from ISS.&nbsp; A preliminary engineering evaluation of this set-up could potentially be performed with the goal of formulating a viable plan of integrating the ETV to the control soft