Determination of partition coefficients from surface acoustic wave vapor sensor responses and correlation with gas-liquid chromatographic partition coefficients

Abstract

Surface acoustic wave (SAW) devices coated with a thin film of a stationary phase sense chemical vapors In the gas phase by detecting the mass of the vapor that distributes Into the stationary phase. This distribution can be described by the partition coefficient. An equation is presented that allows partition coefficients to be calculated from SAW vapor sensor frequency shifts. The experimental responses of fluoropolyd-coated 158-MHz dual delay line SAW vapor sensors are converted to partition coefficients by this method, and these results are compared with partition coefficients determined by gas-liquid chromatography. These two methods rank the vapors In the same order of Increasing sorption, but Individual partition coefficient values are not always In precise agreement. The Influence of temperature and gas-phase vapor concentration on vapor sorption Is also examined.

Surface acoustic wave vapor sensors based on resonator devices

“…Temperature compensation, if perfect (which it never is) only compensates for the frequency drift of the bare devices. Thermal expansion of the polymer on a vapor sensor also induces a temperature drift which remains uncompensated, and the sorption of vapors is highly temperature dependent (17). Therefore, we find that little is lost by separating the reference and sensor chips, and much is gained by actively thermostatting the sensors.…”

“…This consideration demands that selectivity be achieved, a topic not considered in this paper. Selectivity with SAW resonators will be achieved by the same methods used with SAW delay lines and quartz crystal microbalances, namely: the development of selective sorbent materials, the use of sensor arrays with pattern recognition, and pre-separation or pre-concentration methods (2)(3)(4)(5)(6)(7)(8)17,18,(32)(33)(34)(35). Thus the requirements of real world applications will be met by integrating individual SAW vapor sensors into complete detection systems.…”

Theoretical Analysis of Strong-Axis Bending Mode Vibrations for Resonant Microcantilever (Bio)Chemical Sensors in Gas or Liquid Phase

“…In terms of the (dimensionless) partition coefficient of the coating/analyte pair in a given fluid environment, the variation of the sensor's mass is given by [20] (10) in which is the sensitive coating thickness, the coated surface area of the microcantilever, the analyte concentration in the fluid (mass per unit volume), and the partition coefficient is a measure of the distribution of the analyte between the sorbed phase and the surrounding medium. Then, under the assumption , the sensor sensitivity (frequency shift per unit analyte concentration) due to analyte sorption reduces to the following linear relationship between sensitivity and the ratio of coating volume to the microstructure volume : (11) Here is the mass density of the beam's substrate material.…”

Polymers for Chemical Sensors Using Hydrosilylation Chemistry

“…Accordingly, a number of synthetic materials have been prepared and investigated as sensor phases, most of which incorporate hexafluoroisopropanol moieties as the hydrogen-bond acidic group. [28][29][30][31][32][33][34][35][36][37][38][39] A study several years ago compared the hydrogen-bond acidities of several propyl-or allylsubstituted bisphenol structures using inverse gas chromatography and LSERs. 40 It was shown that fluorinated bisphenol-A structures were substantially more hydrogen-bond acidic than non-fluorinated analogs; fluorination improved sorption of basic compounds by factors of 100 or more.…”

“…28,29,41 Figure 5 shows the calibration curves for SAW sensors coated with BSP3, fluoropolyol (FPOL), and polydimethylsiloxane (PDMS) when tested against dimethyl methylphosphonate, a nerve-agent simulant. FPOL is a sensor coating for nerve agents described in the past, 26,27,33,42 and PDMS serves as an example of a sorbent polymer lacking functionalities designed for sorption of basic vapors. Signals of greater than 20,000 Hz are observed at a concentration of only 8 mg/m 3 using BSP3.…”