Quartz Crystal Nanobalance Sensor Research Articles

Application of polydimethylsiloxane/ acrylic resins coated quartz crystal nano balance sensor for detection of glyphosate pesticide

ABSTRACTIn this study, a mixture of polydimethylsiloxane and polyacrylic resins was used as adsorbent for the detection of Glyphosate (GLY) pesticide. A simple and cost-effective analysis method based on Quartz Crystal Nano Balance technique (QCN) was developed to detect GLY. A thin layer of (Polydimethylsiloxane/acrylic resins) mixture was coated on the surface of gold-coated quartz crystal electrodes. The frequency shifts were found to be linear against the concentration of Analytes tested (0.2–8.6 mg/L), with correlation coefficient above 0.98 and sensitivity factor of 70.73 Hz/mg L−1. Among some possible interferences tested (NaCl, CaSO4, MgSO4 and NaHCO3), no major interference was observed in the performance of the sensor.

Application of Molecularly Imprinted Polymer for Determination of Glucose by Quartz Crystal Nanobalance Technique

Accurate determination of glucose is of great importance in various biotechnological processes, food industries, and diagnosing several metabolic disorders. To this point, many methods have been developed to meet this goal. Most of these methods are based on the enzymatic oxidation of glucose. However, the enzymes may be deactivated in different possible condition during storage and use. In this paper, a quartz crystal nanobalance (QCN) modified with a molecularly imprinted polymer (MIP) was developed for online monitoring of glucose in aqueous media without the use of enzymes. The MIP was synthesized by free radical polymerization using different functional monomers, including acrylamide, acrylic acid, allyl alcohol, and acrylonitrile. The findings indicate that acrylic acid has significantly better performance in terms of sensitivity and response time as compared with the other functional monomers. All measurements were performed in a flow cell. The frequency shifts due to the adsorption of glucose were found to be linear versus the concentration of glucose within the concentration range of 10-200 mg L -1 with a correlation coefficient of R 2 = 0.9996. The sensitivity and lower limit of detection of the sensor were found to be 1.20 Hz/mg L -1 and 4.4 mg L -1 , respectively. The results also indicate that organic compounds do not cause any significant interference with glucose determination by the MIPmodified QCN sensor, and using ion exchange resins can eliminate interference of ionic compounds.

Modification of a QCN sensor by SiO2 nanoparticles and MIP for telone determination: Improving its selectivity and sensitivity

A quartz crystal nanobalance (QCN) sensor was developed for the selective determination of telone in aqueous solutions. Telone imprinted nanocomposite was synthesized using SiO2 nanopowders and acrylic acid. FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the morphology and microstructure of the SiO2-MIP nanocomposite. The prepared SiO2-MIP nanocomposite particles were coated on quartz crystal electrode to form complementary structures for the template recognition of telone. The SiO2-MIP coated electrode was used to determine telone levels in solution. The developed sensor demonstrated a high selectivity and sensitivity (4.96Hz per mgL−1) for telone. It can also be used for telone determination in the concentration range between 1 to 40mgL−1. Furthermore, a good reproducibility, R.S.D.=1.66% (n=5) was observed. During its photocatalytic degradation by UV/ZnO, telone residue process was measured by the developed sensor and GC to validate the accuracy of the developed sensor in real world situation. According to the results of the t-test, QCN sensor and GC spectroscopy measurement results enjoy good agreement. Therefore, a fabricated sensing system has the potential for real sample application.

Quartz crystal nanobalance in conjunction with principal component analysis for identification and determination of Telone, Methyl Iodide, Endosulfan, and Methyl Bromide

This study reports the capability of a system based on single silicon OV‐25 (a methylphenylsilicon (∼75% phenyl)) modified quartz crystal nanobalance (QCN) sensor with the application of principal component analysis (PCA) as a pattern recognition technique for the detection and determination of some organo‐halide pesticides (Telone, Methyl Iodide, Endosulfan, and Methyl Bromide) in aqueous solutions. It was found that the sensor response is linear against the organo‐halide pesticides in the concentration ranged between of 5–30 mg L−1 for Endosulfan and 5–60 mg L−1 for three other studied pesticides. The correlation coefficients (0.992, 0.989, 0.994, and 0.993), the sensitivity factors (2.27, 2.41, 3.61, and 1.44 Hz/mg L−1), and the lower limit of detections (1.4, 4.6, 2, and 4.6 mg L−1) were obtained for Telone, Methyl Iodide, Endosulfan, and Methyl Bromide, respectively. PCA has been performed based on the silicon OV‐25‐modified QCN sensor measurement results, and the signals were transformed into feature space. It was found that the transformed values of Telone, Methyl Iodide, Endosulfan, and Methyl Bromide were well separated. Thus, the developed QCN sensor has very good applicability to successfully determine organo‐halide pesticides. Also, it was found that over 93.5% of the data variance could still be explained by using two principal components (PC1 and PC2). © 2013 American Institute of Chemical Engineers Environ Prog, 33: 267–274, 2014

Measurement of the pesticide methomyl by modified quartz crystal nanobalance with molecularly imprinted polymer

A simple and cost-effective analysis method based on quartz crystal nanobalance (QCN) coated with a molecularly imprinted polymer (MIP) for measurement of methomyl was investigated. In the first part of this study, a sensitive, selective and reliable quartz crystal nanobalance (QCN) sensor was designed for the selective determination of methomyl in aqueous solutions. In the second part, in order to demonstrate the applicability and performance of the fabricated sensor in the real world situation, it was successfully applied for the determination of methomyl residual in photo catalytic degradation by ZnO powders in aqueous solutions. The fabricated sensor presents a high selectivity and sensitivity (4.56 Hz per mg L−1) for methomyl and it can be used for determination of methomyl concentration ranged between 1 to 45 mg L−1. Furthermore, good reproducibility, R.S.D. = 2.14% (n = 5) was observed. To investigate the performance of the sensor, the change in the insecticide concentration during the photocatalytic degradation of methomyl by ZnO was investigated by QCN and UV/Vis spectroscopy. Results obtained from QCN sensor and UV/Vis spectroscopy measurement are in good mutual agreement. So the fabricated sensor may provide an efficient, low cost, easy-to-use method for the in-field evaluation of specific targeted analytes in aqueous solutions which in turn may lead to improved food and water safety.

Application of nanobalance technique and principal component analysis for detection of the soil fumigant Telone residues in the air

Quartz crystal nanobalance (QCN) technique is considered as a powerful mass sensitive sensor for monitoring of materials in the sub-nanogram level. In the current study, a method based on QCN technique developed to determine Telone in air. Various coating materials including methyl phenyl silicon, 75% phenyl (OV25) and molecularly imprinted polymer (MIP) were employed. The frequency shift of OV25-modified quartz crystal was found to be linear against organohalogen compounds [Telone (soil fumigant), Koril (Herbicide), Endosulfan (organochlorine insecticide) and Chloroform (solvent)] concentrations in the range of 2.4 to 48 mg L−1 for Telone vapor and 4.8–24 mg L−1 for three other vapors. The correlation coefficients for Telone, Koril, Endosulfan and Chloroform were 0.992, 0.996, 0.989 and 0.991, respectively. The principal component analysis was also utilized to process the frequency response data of the organic vapors. Using principal component analysis, it was found that more than 93.85% of the data variance could still be explained by use of two principal components (PC1 and PC2). Subsequently, the successful discrimination of Telone and other compounds was quite possible through the principal component analysis of the transient responses of the OV25-modified electrode. In the second method, a molecularly imprinted polymer-coated sensor for Telone was developed. Molecularly imprinted polymer coated quartz crystal (MIP-QCN) showed a selective response to Telone and gave a linear relationship between frequency shift and amount of Telone from 1 to 48 mg L−1. In this investigation, the proficiency of MIP-QCN and OV25-modified QCN sensors were compared.

Selective determination of ethyl acetate, acetone, ethanol, and methyl ethyl ketone using quartz crystal nanobalance combined with principle component analysis

Quartz crystal nanobalance (QCN) sensors are considered as powerful mass sensitive sensors to determine materials in the sub-nanogram level. In the current study a method based on QCN modified with polyethylene glycol (PEG) has been developed to determine organic vapors (ethyl acetate, acetone, ethanol and methyl ethyl ketone). The frequency shift of QCN was found to be linear against analytes concentrations in the range between 4 to 35 mg/L for acetone vapor and 4–70 mg/L for 3 other vapors. The correlation coefficients for ethyl acetate, acetone, ethanol, and methyl ethyl ketone were 0.9971, 0.9976, 0.9984 and 0.9927, respectively. The principal component analysis was also utilized to process the frequency response data of the organic vapors. Using principal component analysis, it was found that over 95% of the data variance could still be explained by use of two principal components (PC1 and PC2). Subsequently, the successful discrimination of ethyl acetate and other compounds was possible through the principal component analysis of the transient responses of the PEG-modified QCN sensor.

Application of Quartz Crystal Nanobalance for Simultaneous Determination of Vanillylmandelic and Homovanillic Acids by a Net Analyte Signal-Based Method

Homovanillic acid (HVA) and vanillylmandelic acid (VMA) were selectively determined by quartz crystal nanobalance sensor in conjunction with net analyte signal (NAS)-based method called HLA/GO. An orthogonal design was applied for the formation of calibration and prediction sets including HVA, VMA, and some common and structurally similar urine compounds. The selection of the optimal time range involved the calculation of the NAS regression plot in any considered time window for each test sample. The searching of a region with maximum linearity of NAS regression plot (minimum error indicator) and minimum of predicted error sum of squares value was carried out by applying a moving window strategy. Based on the obtained results, the differences on the adsorption profiles in the time range between 1 and 300 s were used to determine mixtures of compounds by HLA/GO method. Several figures of merit like selectivity, sensitivity, analytical sensitivity, and limit of detection were calculated for both compounds. The results showed that the method was successfully applied for the determination of VMA and HVA.

Ruthenium dioxide quartz crystal nano-balance

A new type of quartz crystal nano-balance (QCN) has been designed using ruthenium oxide (RuO 2) electrodes as substitutes for the metallic ones, which are generally used to prepare QCN sensors. The conductive RuO 2 electrodes were deposited on quartz discs using reactive magnetron sputtering. XPS measurements showed the ratio of atomic concentrations [Ru]/[O] close to 1:2. XRD indicated crystalline structure of the deposits and AFM showed highly developed surface with pits and other features of various sizes. The oxide-based resonator operated stable in both gaseous and liquid environments as demonstrated by the prolonged experiments of water adsorption–absorption in humid air and electrochemical copper deposition–dissolution in acid solution. The sensor opens new opportunities to study thin films of RuO 2. One of the advantages of the sensor is possibility to avoid the galvanic effects, which may occur when using the conventional QCN with metallic electrodes.

Net analyte signal-based simultaneous determination of ethanol and water by quartz crystal nanobalance sensor

Net analyte signal (NAS)-based method called HLA/GO was applied for the selectively determination of binary mixture of ethanol and water by quartz crystal nanobalance (QCN) sensor. A full factorial design was applied for the formation of calibration and prediction sets in the concentration ranges 5.5–22.2 μg mL −1 for ethanol and 7.01–28.07 μg mL −1 for water. An optimal time range was selected by procedure which was based on the calculation of the net analyte signal regression plot in any considered time window for each test sample. A moving window strategy was used for searching the region with maximum linearity of NAS regression plot (minimum error indicator) and minimum of PRESS value. On the base of obtained results, the differences on the adsorption profiles in the time range between 1 and 600 s were used to determine mixtures of both compounds by HLA/GO method. The calculation of the net analytical signal using HLA/GO method allows determination of several figures of merit like selectivity, sensitivity, analytical sensitivity and limit of detection, for each component. To check the ability of the proposed method in the selection of linear regions of adsorption profile, a test for detecting non-linear regions of adsorption profile data in the presence of methanol was also described. The results showed that the method was successfully applied for the determination of ethanol and water.

Analysis of transient response of single quartz crystal nanobalance for determination of volatile organic compounds

Quartz crystal nanobalance (QCN) sensors are considered as powerful mass sensitive sensors. In this study, a single quartz crystal nanobalance modified with polystyrene has been employed to determine benzene, toluene, ethylbenzene and xylene (BTEX compounds). The frequency shift of QCN sensor was found to be linear against the BTEX compound concentrations in the range about 0–27 mg l −1. The correlation coefficients for benzene, toluene, ethylbenzene, and xylene were 0.9917, 0.9904, 0.9904 and 0.9925, respectively. The principal component analysis was also utilized to process the transient response data of the single quartz crystal, considering to the different adsorption–desorption dynamics of BTEX compounds. Using principal component analysis, it was found that over 75% of the data variance could still be explained by use of three principal components (PC1, PC2 and PC3). The score plot of the three first PCs data were used to classify and identify organic vapors. The results showed that the polystyrene modified QCN had favorable identification and quantification performances for the BTEX compounds.