Obtaining Chemical Selectivity from a Single, Nonselective Sensing Film: Two-Stage Adaptive Estimation Scheme with Multiparameter Measurement to Quantify Mixture Components and Interferents

Abstract

A new approach is reported to detect and quantify the members of a group of small-aromatic-molecule target analytes: benzene, toluene, ethylbenzene, and xylenes (BTEX), dissolved in water, in the presence of interferents, using only the data collected from a single polymer-coated SH-SAW (shear horizontal surface acoustic wave) device and a two-stage adaptive estimation scheme. This technique is composed of exponentially weighted recursive least-squares estimation (EW-RLSE) and a bank of Kalman filters (BKFs) and does not require any prior knowledge of the initial concentration range of the target analytes. The proposed approach utilizes the transient sensor response to sorption and/or desorption of the analytes as well as the error range associated with the response time constants to provide more information about the analyte-specific interactions with the polymer film. The approach assumes that the sensor response to contaminated groundwater is a linear combination of the responses to the single target analytes, the interferents that interact with the selected polymer sensor coatings, and measurement noise. The proposed technique was tested using actual sensor responses to contaminated groundwater samples containing multiple BTEX compounds with concentrations ranging from 10 to 2000 parts per billion, as well as common interferents including ethanol, 1,2,4-trimethylbenzene, naphthalene, n-heptane, and MTBE (methyl tert-butyl ether). Estimated concentration values, accurate to ±10% for benzene/toluene and ±15% for ethylbenzene/xylenes, are obtained in near-real time. The utilization of sorption and/or desorption data enables detection and quantification of BTEX compounds with improved accuracy, high tolerance to measurement noise, and improved chemical selectivity.

Bulk and Surface Acoustic Wave Sensor Arrays for Multi-Analyte Detection: A Review

“…Aliphatic components, however, did not interfere with the signal responses. In mixtures, the concentrations obtained with the sensor were comparable to those obtained with GC-PID (GC with photoionization detector), with the average difference being ±6.3% [72,86].…”

“…One way to overcome this problem is to adapt the carrier medium transporting the liquid samples to the sample background in a way that the electrical differences are minimized. Newer approaches include the combination of SAW resonators with electrical sensors resulting in a dual signal response, which would allow an improved characterization of the individual sensor responses [54,[70][71][72][73][74].…”

Quantitative Detection of Complex Mixtures using a Single Chemical Sensor: Analysis of Response Transients using Multi-Stage Estimation

“…In this case, valuable time (∼20 min) could be saved by utilizing the proposed technique. Note that estimation of BTEX concentrations in the presence of various interferents, including TMB, has also been demonstrated in a recent publication by the authors …”

“…Note that estimation of BTEX concentrations in the presence of various interferents, including TMB, has also been demonstrated in a recent publication by the authors. 27 In addition to the two sample results discussed above, further tests were performed to more fully characterize the detection and quantification of both multi-analyte and singleanalyte samples using our method. Results obtained from these tests are summarized in Table 5, which includes data on SH-SAW sensors coated with 0.6 μm PECH and 0.8 μm PIB.…”

Real-Time Measurement of Polymer Brush Dynamics Using Silicon Photonic Microring Resonators: Analyte Partitioning and Interior Brush Kinetics

“…The resonance wavelengths of the brush-coated microrings were tracked as the solution was changed from water to the specific analyte (Figure a). The shifts in resonance wavelength as a function of time measured during this partitioning were fit to a Langmuir binding isotherm derived by Sothivelr et al for analyzing molecular partitioning into a thin film where the relative shift is the given shift (Δpm) at any time point t , A is a constant dependent on the maximum observed shift at equilibrium, T is the response time for a given analyte-coating combination (the time required to reach half of the maximum value), C amb is the ambient concentration of the analyte, and P is the brush–solvent partition coefficient. Note that in using this equation, it is assumed that there is a constant value for the analyte concentration in the bulk, due to constant flow of fresh analyte-containing solution, and that the only cause of the change being measured is due to single-analyte partitioning.…”