Laboratory and Field Evaluation of a SAW Microsensor Array for Measuring Perchloroethylene in Breath

Abstract

This article describes the laboratory and field performance evaluation of a small prototype instrument employing an array of six polymer-coated surface acoustic wave (SAW) sensors and a thermal desorption preconcentration unit for rapid analysis of perchloroethylene in breath. Laboratory calibrations were performed using breath samples spiked with perchloroethylene to prepare calibration standards spanning a concentration range of 0.1-10 ppm. A sample volume of 250 mL was preconcentrated on 40 mg of Tenax GR at a flow rate of 100 mL/min, followed by a dry air purge and thermal desorption at a temperature of 200 degrees C. The resulting pulse of vapor was passed over the sensor array at a flow rate of 20 mL/min and sensor responses were recorded and displayed using a laptop computer. The total time per analysis was 4.5 min. SAW sensor responses were linear, and the instrument's limit of detection was estimated to be 50 ppb based on the criterion that four of the six sensors show a detectable response. Field performance was evaluated at a commercial dry-cleaning operation by comparing prototype instrument results for breath samples with those of a portable gas chromatograph (NIOSH 3704). Four breath samples were collected from a single subject over the course of the workday and analyzed using the portable gas chromatograph (GC) and SAW instruments. An additional seven spiked breath samples were prepared and analyzed so that a broader range of perchloroethylene concentrations could be examined. Linear regression analysis showed excellent agreement between prototype instrument and portable GC breath sample results with a correlation coefficient of 0.99 and a slope of 1.04. The average error for the prototype instrument over a perchloroethylene breath concentration range of 0.9-7.2 ppm was 2.6% relative to the portable GC. These results demonstrate the field capabilities of SAW microsensor arrays for rapid analysis of organic vapors in breath.

Analysis of Airborne Biomarkers for Point-of-Care Diagnostics

“…The major chemical sensor technologies include optical, 125–129 electrochemical, 130–137 conductive polymer, 138 –143 semiconductor, 144–146 and mass sensitive (piezoelectric) 147 –151 technologies. Due to their sensitivity and selectivity, optical and electrochemical devices are often the technologies of choice for monitoring inorganic compounds (e.g., NO, CO 2 , and H 2 ), which are often associated with cardiovascular conditions, asthma, and COPD.…”

Surface acoustic wave (SAW) microsensor array for measuring VOCs in drinking water

“…[17][18][19] Selection of a diverse set of polymer coatings provides a broad range of solubility interactions and yields an array with characteristic response patterns that can be used for the identification and quantification of a large number of individual vapors and simple mixtures. 12,[17][18][19][20][21][22][23] Laboratory and field applications of SAW-based instrumentation have recently been described for breath analysis, 19,24 occupational exposure monitoring, 17,23 nerve agent detection, 25 chemical protective clothing permeation testing, 26 and in situ environmental monitoring. 27 The response of a polymer-coated SAW sensor is a shift in frequency, Df v , that is proportional to the amount of vapor absorbed.…”

“…The SAW instrument used in this project is a slightly modified version of that described previously for breath analysis. 24 The primary components are shown schematically in Fig. 1a.…”

“…Polymers were obtained from Scientific Polymer Products, Inc. (Ontario, NY) or on pre-coated sensors supplied by Femtometrics, Inc. (Irvine, CA). This set of polymers was selected on the basis of previous studies demonstrating stability and potential selectivity 18,19,24 and upon the recommendation of the SAW array manufacturer. Coatings were applied using an airbrush and dilute solutions of each polymer in chloroform.…”

Trace Analysis in End-Exhaled Air Using Direct Solvent Extraction in Gas Sampling Tubes: Tetrachloroethene in Workers as an Example

“…Sample analyses were performed using a gas chromatograph [5–13, 15–22], surface acoustic wave sensors [14], an atmospheric-pressure ionization mass spectrometer [24], or an infrared spectrometer [8, 25]. The gaseous samples were transferred directly into the measurement device using gas-tight syringes [5–9, 11, 15–19, 22], or the tetrachloroethene was extracted from the breath or breath samples using solid-phase microextraction (SPME) [10] or adsorption tubes and then analysed following thermal desorption [10, 13, 14] or liquid elution [12, 20, 21]. …”