Analysis of the Detection of Organophosphate Pesticides in Aqueous Solutions Using Polymer-Coated SH-SAW Devices

Organophosphate pesticides (OPs) have been found as contaminants in surface and ground waters, soil, and agricultural products. Because OPs are toxic compounds, rapid detection/monitoring of OPs in groundwater is necessary to allow for real-time remediation. Detection of OPs in water has already been demonstrated using poly(epichlorohydrin) [PECH] and polyurethane as the sensing layers. However, the response times were relatively long, hindering real-time monitoring. In this work, a hybrid organic/inorganic chemically sensitive layer [bisphenol A-hexamethyltrisiloxane (BPA-HMTS)] that shows a high degree of partial selectivity for OPs is synthesized, characterized (in terms of the glass transition temperature, Tg, water stability, sensitivity, selectivity, detection limit, and absorption/response time) for the rapid detection of organophosphate pesticides. Direct chemical sensing in aqueous solutions is performed using guided shear horizontal surface acoustic wave sensor platforms on 36° rotated Y-cut LiTaO3 and 42.75° rotated Y-cut Quartz, respectively. It is shown that, for the same coating thickness, a 60% reduction in sensor response time is achieved without reduction in sensitivity compared to PECH. Considering the Tg, for the polymers, it is seen that the faster response shown by BPA-HMTS is due to the porous siloxane backbone, HMTS. Kinetic studies for the absorption of OPs (parathion-methyl, parathion, and paraoxon) from aqueous solutions into the BPA-HMTS coating are conducted. The data are analyzed within the context of two absorption models: penetration-limited and diffusion-limited absorptions. It is shown that the absorption process is rate limited by penetration with a concentration independent absorption time constant or mass transfer coefficient. The absorption time constants for parathion-methyl, parathion, and paraoxon are calculated. A limit of detection of 60, 20 and 100 μg/L (ppb) for parathion-methyl, parathion, and paraoxon, respectively, is calculated for the present non-optimized sensor. Concentrations as low as 500 μg/L (ppb) parathion are actually measured. This is much lower than the typical concentrations found on agricultural produce (≥ 10 ppm). Furthermore, sensor signal analysis in the form of the extended Kalman filter (EKF) is employed on-line during the detection process. The sensor response was first represented by a state-space model which includes all relevant contributions to the polymer-coated device response. This allows for the steady-state response and absorption time constant to be extracted on-line well before the steady-state is reached, thus further reducing the time for analyte identification and quantification. It is noted the absorption time constant, often unique to a class of analyte-coating pairs, can be used to improve analyte recognition

Online Drift Compensation for Chemical Sensors Using Estimation Theory

Sensor drift from slowly changing environmental conditions and other instabilities can greatly degrade a chemical sensor\u27s performance, resulting in poor identification and analyte quantification. In the present work, estimation theory (i.e., various forms of the Kalman filter) is used for online compensation of baseline drift in the response of chemical sensors. Two different cases, which depend on the knowledge of the characteristics of the sensor system, are studied. First, an unknown input is considered, which represents the practical case of analyte detection and quantification. Then, the more general case, in which the sensor parameters and the input are both unknown, is studied. The techniques are applied to simulated sensor data, for which the true baseline and response are known, and to actual liquid-phase SH-SAW sensor data measured during the detection of organophosphates. It is shown that the technique is capable of estimating the baseline signal and recovering the true sensor signal due only to the presence of the analyte. This is true even when the baseline drift changes rate or direction during the detection process or when the analyte is not completely flushed from the system

Analysis of the Detection of Organophosphate Pesticides in Aqueous Solutions Using Hydrogen-Bond Acidic Coating on SH-SAW Devices

The work presented in this paper focuses on the synthesis and characterization of a hybrid organic/inorganic chemically sensitive layer for rapid detection and analysis of OPs in aqueous solutions using SH-SAW devices. Coated SH-SAW devices on 36° YX-LiTaO and 42.75° YX-Quartz (ST-90° X Quartz), are used to determine the optimum operating conditions for achieving rapid sensor responses with high sensitivity. Three analytes (parathion-methyl, parathion, and paraoxon), having similar molecular mass and volume, are used to evaluate the performance of the hybrid organic/inorganic coating in terms of sensor properties of interest including sensitivity, selectivity, reproducibility. It is shown that the coating has a high degree of partial selectivity and sensitivity towards the analytes. With the present non-optimized chemical sensor, a limit of detection of 60 (ppb), 20 (ppb) and 100 (ppb) is estimated for parathion-methyl, parathion, and paraoxon, respectively, when using a 0.5 -thick BPA-HMTS sensing layer. Concentrations as low as 500 (ppb) parathion have been measured. This concentration is significantly much lower than the typical concentrations found on agricultural produce (≥10 ppm)

High-Sensitivity Magnetic Sensors Based on GMI Microwire-SAW IDT Design

This work presents a design approach for a highly sensitive, miniaturized magnetic sensor. The design makes use of GMI microwires and a multi-electrode SAW IDT. The use of SAW IDTs allows for the magnetic effect of the GMI microwire to be measured through the transduction process. This approach permits simultaneous measurement at different frequencies of operation, enabling highly sensitive measurement over a wide range of magnetic fields. This technique may find application in magnetic sensing for non-invasive battery SOC measurement

The influence of blanching, anti-browning agent and processing time on some physico-chemical properties and appearance of green peppers (Capsicum sinensis) during canning

Central Composite Rotatable Design (CCRD) was used to generate twenty combinations of these factors: blanching time, processing time and sodium metabisulphite concentration. The optimized conditions were then adapted for the canning process of green pepper. Blanching time ranged from 0-1 min whereas processing time and sodium metabisulphite concentration ranged from 10-30 min and 0-0.2%, respectively. The canned products were analyzed for physico-chemical qualities using standard analytical methods. Results obtained from various physico-chemical analyses showed variable trends and influences of the linear, quadratic and exponential interactions on the measured quality indices such as pH of the drained liquid, drained weight of the canned product, leached solids and colour of the canned products. The results showed significant (p.0.05) quadratic effect of sodium metabisulphite as well as linear effect of blanching time on the drained weight of the canned green pepper. Generally, the pH of the medium decreased (increased acidity) with increasing processing time, which was also positively associated with the extent or amount of leaching. Additionally, all three factors were observed to have affected (to variable extent) the colour of the canned products. Blanching and processing times also affected the degree of browning. There was a strong significant (p.0.05) influence of the quadratic factors of blanching time, processing time and sodium metabisulphite concentration on the colour properties (a-values, b-values and L-values) of the canned products. Statistical analysis showed significant (p.0.05) linear effects of blanching time and sodium salt concentration as well as the combined effect of both factors on all the colour properties. All the studied parameters had significant  regression coefficients (p.0.05) suggesting the studied parameters  contributed significantly to the observed changes. Colour of the canned  products changed from green toward redness with increasing blanching time at all concentrations of sodium metabisulphite. Optimal processing  combination of 0 min blanching time, 10 min processing time and sodium metabisulphite concentration of 0.2% produced a highly acceptable canned pepper product with preferred physico-chemical and appearance properties.Key words: Canning, pepper, blanching, antibrowning agent

Optimization of the Production of a Chocolate-flavoured, Soy-peanut beverage with acceptable Chemical and Physicochemical Properties using a Three-component Constrained Extreme Lattice Mixture Design

This study explored the feasibility of producing a soy-peanut, chocolate-flavoured milk beverage with acceptable chemical and physico-chemical properties from soybeans, peanuts and cocoa powder. Ten formulations were processed by mixing three basic ingredients: soybeans (20g/100g-80g/100g), peanuts (Arachis hypogaea L.) (20g/100g-60g/100g) and cocoa powder (1g/100g-7g/100g). The optimized proportions of the ingredients were obtained using a three-component, constrained extreme lattice mixture design. The optimized product consisted of 54.0-58.5% soybeans, 37.0-42.0% peanut and 4.46 - 4.48% cocoa powder and had an energy value of 124.103kJ/100g.  Proximate analysis of the optimized products indicated that the beverage has a protein content of 2.77%, fat content of 1.38%, carbohydrate content of 1.26%, ash content of 0.32% and water content of 94.27%. This suggests that production of an acceptable full fat soy-peanut, chocolate-flavoured milk beverage is feasible through the optimization of the basic ingredients. Keywords: lattice mixture design, soybeans, peanuts, cocoa powder, soy-peanut, chocolate-flavoured milk beverage

Lack of Apoptosis of Infiltrating Cells as the Mechanism of High Susceptibility to EAE in DA Rats

Dark Agouti (DA) rats are highly susceptible to induction of Th-l-mediated autoimmunity disease, including experimental allergic encephalomyelitis (EAE). In contrast to other susceptible rat strains in which disease is induced only with encephalitogen emulsified in complete Freund's adjuvants (CFA), in DA rats EAE develops after injection of encephalitogen in incomplete Freund's adjuvants (IFA) or Titermax, putative Th-2 directed adjuvant. Lymph node cells derived from immunized DA rats and stimulated in vitro produce significantly more Interferon-γ (IFN-γ) than resistant Albino Oxford (AO) rats. However, cells derived from both strains produce large amounts of IL-10 but not IL-4. Immunized lymph node cells derived from EAE susceptible (AO × DA) F1rats induce clinical signs of disease in sublethally irradiated parental DA but not AO rats. The pathohistology of the target tissue in these recipients clearly demonstrated infiltration of mononuclear cells in both parental strains. However, the number of CD4+ cells was significantly higher and number of apoptotic cells significantly lower in DA rats sacrificed 8 days after passive transfer. We postulate that in addition to higher IFN-γ and TNF-α production, resistance to early apoptosis of the invading cells in the target tissue possibly due to lack of downregulation by TGF-β leads to exceptional susceptibility to EAE in DA rats

THE EFFECT OF LEADERSHIP QUALITIES ON THE PERFORMANCE OF SMALL AND MEDIUM ENTERPRISES

Purpose: This study aims to investigate the effect of leadership qualities on the performance of Small and Medium Enterprises (SMEs), and to examine the impact leadership qualities have on SMEs' performance.   Theoretical and Framework: Leadership qualities play a role in enhancing employee job satisfaction and organizational performance.  Trait theory believes that leaders are either born or made with some qualities that will make them excel in leadership roles.  Leaders’ emotional intelligence, integrity, honesty, creativity, and innovation are vital for Small and Medium Enterprises' sustainability.   Design/Methodology/Approach: Descriptive design was adopted, using cross-sectional approach. Purposive sampling was used with a sample size of 400 employees of SMEs in the Accra Metropolitan Area. Usable questionnaires of 344 were analysed using IBM SPSS for the descriptive statistics with structural equation model (SEM) AMOS to investigate the extent of the relationship.   Findings: The study discovered that each of the three leadership attributes has a strong statistically significant positive link with the success of SMEs. Emotional intelligence, integrity and honesty, and creativity and invention are factors that influence SMEs' performance.   Originality/Value: This work is unique because it adds to the literature on the impact of leadership traits on SME performance, which has not been thoroughly explored in a developing nation like Ghana. The study also illustrated how to utilize a structural equation model to examine the relationship between leadership and the performance of small businesses. Furthermore, by selecting samples from various SME sectors, the study enhanced the understanding of leadership attributes