Different Concentrations Of Analyte Research Articles

B-216 Ethanol/isopropanol-free and enzyme-free universal nucleic acid extraction and purification system for fast molecular detection from swab samples

Abstract Background Efficient nucleic acid (NA) extraction has been made technology advancement in molecular science. However, there are several challenges yet to address. Firstly, ethanol or isopropanol are important components of the buffers for the most commercially available NA extraction kits. When put on cartridge for POC applications, they can react with plastic materials, undermining their mechanical/physiochemical properties. They can also be problematic due to their volatility, flammability and potential to leak. Secondly, turn-around time for most commercial kits is long and procedure is rather tedious. Thirdly, most of the extraction buffers can only be used to extract either DNA or RNA from either viruses or bacteria. A universal buffer system is lacking. Lastly, special components in some extraction buffers require -20°C or 4°C storage for desired performance, especially for those kits containing proteinase for cell lysis and nuclease denaturation and carrier NA for low quantity of template, causing inconvenience in shipping and storage. Delta developed buffers and associated protocol to address the challenges listed above. This study is to evaluate the performance of the Delta TNA buffer system in NA extraction and purification from various target pathogens in swab samples when compared to that of the leading commercial products. Methods The stock strains of staphylococcus aureus, pseudomonas aeruginosa and H-coronavirus OC43 were diluted in Delta Molecular Transport Media containing swab sample matrix to the testing concentrations before performing NA extraction. Vircell SARS-CoV-2 RNA was spiked directly into PCR reactions to generate a standard curve with 10x serial dilutions for the recovery rate test using Delta TNA kit. 300ul of samples were used for the NA extraction and purification with 80 ul eluate generated. The manufacturers’ instructions were followed. The extracted RNA or DNA was amplified on BioRAD CFX96. Results The extraction efficiency on RNA from H-coronavirus OC43, DNA from pseudomonas aeruginosa and staphylococcus aureus in swab samples, was compared with Katsura Respi and MN Pathogen kits, Qiagen DNA and viral RNA kits respectively. Delta TNA kit outperformed in either earlier Cq value or higher detection rate for different concentrations of analytes in <10 min comparing to up to 95 min for the commercial kits tested. The RNA recovery rate of Delta TNA kit was comparable to that of the Qiagen Viral Kit with 37.54% vs 29.84% at 10 copies/rxn, 146.84% vs 140.76% at 100 cpies/rxn and 118.29% vs 111.76% at 1000 copies/rxn. Meanwhile, Delta Swab TNA buffer was compatible with large spectrum of magnetic beads possessing various coating groups and particle sizes. Conclusions We provided a stable, user- and environment-friendly total nucleic acid extraction and purification system which is ethanol/isopropanol-free and enzyme-free. There is no pre-treatment or drying steps in the protocol and no centrifugation required. Delta’s protocol has the least total number of steps and least amount of total time taken amongst the kits compared. It serves as a universal recipe for both DNA and RNA from pathogens in swab samples including viruses and bacteria in less than 10 min, with competitive performance in both PCR and LAMP.

A multi-site recognition molecularly imprinted solid-phase microextraction fiber for selective enrichment of three cross-class environmental endocrine disruptors.

Molecularly imprinted solid-phase microextraction fibers with multi-site recognition were prepared for the simultaneous enrichment of three cross-class environmental endocrine disruptors (EEDs) in environmental water. The surface morphology of the multi-site recognition molecularly imprinted fibers was characterized using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and surface area and pore size analyzer. Under optimal extraction conditions, the molecularly imprinted fibers showed higher extraction capacity to bisphenol F, diethyl phthalate, and methyl paraben than non-imprinted polymer fibers and commercial fibers. Compared with commercial solid-phase microextraction fibers, the multi-site recognition molecularly imprinted fibers showed superior extraction performance at different concentrations of analytes. The selectivity study confirmed that the multi-site recognition molecularly imprinted solid-phase microextraction fibers were highly selective not only for specific template molecules but also for bisphenols, parabens, and phthalates. Furthermore, the method achieved a limit of detection of 0.003-0.02 μg L-1 for the three cross-class EEDs in environmental water samples with recoveries ranging from 75.76% to 112.69% and relative standard deviations below 11.46%. Thus, the novel MIP fibers with multi-site recognition prepared in this work have provided a promising approach in the field of specific adsorption and a strategy for the simultaneous and sensitive monitoring of multiple cross-class trace EEDs.

Presence of parabens in children’s faeces. Optimization and validation of a new analytical method based on the use of ultrasound-assisted extraction and liquid chromatography-tandem mass spectrometry

Due to their antimicrobial properties, parabens are a family of synthetic chemical compounds widely used as preservative additives in food and cosmetics. For this reason, humans are highly exposed to them. These substances are capable of altering the proper functioning of the endocrine system and are classified as endocrine disrupting chemicals (EDCs). Traditionally, urine has been the typical matrix studied as an excretion route. However, faeces contain valuable information. In the present study, the presence of methyl-, ethyl-, isopropyl-, propyl-, isobutyl-, butyl- and phenylparaben in stool samples from children has been evaluated. A new analytical method has been optimised and validated. The method is based on the use of ultrasound-assisted extraction followed by clean-up of the extracts by dispersive solid phase extraction dSPE). Parabens were analysed by ultrahigh performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The matrix effect was evaluated and a significant effect was observed for all analytes. Therefore, calibration and validation were performed by addition of different concentrations of analytes to faecal blanks. The coefficient of determination (%R2) for calibration curves was higher than 98.9% in all cases. The limits of detection and quantification were between 0.2 and 0.4 and 0.6–1.0 ng g−1 respectively. The recovery for accuracy assessment had values between 89.0% and 112.7% with an RSD of less than 15% in all cases. The method was successfully applied to 14 samples from children volunteers, 100% of which showed contamination by at least one of the analysed compounds.

Construction of a Homogeneous Enzyme-Free Autocatalytic Nucleic Acid Machinery for High-Performance Intracellular Imaging of MicroRNA

Construction of a Homogeneous Enzyme-Free Autocatalytic Nucleic Acid Machinery for High-Performance Intracellular Imaging of MicroRNA

Design and Performance Analysis of Reconfigurable 1D Photonic Crystal Biosensor Employing Ge₂Sb₂Te₅ (GST) for Detection of Women Reproductive Hormones.

The present research demonstrates a novel 1D photonic crystal (PhC) based reconfigurable biosensor pertaining to label-free detection of different concentrations of progesterone and estradiol, which play a vital role in developing reproductive hormones in women. The proposed sensor is designed by an alternative arrangement of Na3 AlF6 and CeO2, with a central defect layer. A thin layer of novel phase change chalcogenide material (Ge2 Sb2 Te5) is deposited along the two sides of the defect layer to improve the sensing performance. Numerical simulation of transmission spectrum for TE mode is carried out by using the transfer matrix method (TMM). The mainstay of this research is centered on the assay of shift in the defect mode position and intensity with respect to different concentrations of analyte, by changing the phase of the GST material from amorphous to crystalline. Interestingly, we observed a high tunability in defect mode wavelength, when the phase is changed from amorphous to crystalline, which leads to accomplishment of a high sensitivity of 1.75 nm/nmol/L for progesterone and 20.5 nm/nmol/L for estradiol. Aside from sensitivity, other significant parameters like figure of merit and detection limit are computed, which give a deep insight into the sensing performance. These encouraging sensing performances pave the path for efficient detection of different concentrations of progesterone and estradiol to monitor various gynecological problems in women.

Application of Chemometrics-assisted HPLC-DAD Strategies for Simultaneous Determination of Paracetamol, Pseudoephedrine HCl, Dextromethorphan HBr, Doxylamine Succinate and Saccharin in Syrup Formulation

Introduction:This study introduces an effective strategy, which combines high performance liquid chromatography coupled with diode array detection (HPLC-DAD) with multivariate calibration methods for the simultaneous determination of paracetamol (PAR), pseudoephedrine HCl (PSE), dextromethorphan HBr (DEX) and doxylamine succinate (DOX) along with sweetener saccharin (SAC) in syrup formulation. Methods: PLS-2 and PCR calibration algorithms were selected for data processing. Based on the strategy, all target analytes were rapidly quantified within 5.3 min under the simple isocratic elution (water: methanol, 20/80, v/v) without a complete separation. The performances of the proposed methods were confirmed by analyzing a series of synthetic solutions including different concentrations of analytes. Results:The average recovery values were in the range of 100.33 to 103.70%, and the REP (relative error of prediction) values ranged from 1.96 to 4.36% showed that these methods could provide satisfactory predictions. Conclusion:Novel HPLC methods coupled with PLS and PCR algorithm enable a simple, fast and low-cost analysis of similar pharmaceutical products for simultaneous determination of the target compounds.

Determination of vitamin E and its metabolites in equine urine using liquid chromatography-mass spectrometry.

Equine neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM) is a hereditary, deteriorating central nervous disease in horses. Currently, the only way to confirm eNAD/EDM is through a postmortem histological evaluation of the central nervous system. Vitamin E, specifically the isoform alpha-tocopherol (α-TP), is known to protect eNAD/EDM susceptible horses from developing the clinical phenotype. While vitamin E is an essential nutrient in the diet of horses, there are no diagnostic tests able to quantitate vitamin E and its metabolites in urine. An ultra-performance liquid chromatography-atmospheric-pressure chemical ionization mass spectrometry (UPLC-APCI-MS/MS) method was developed and validated following acidic hydrolysis and solid phase extraction to quantitate vitamin E and its metabolites in equine urine. A blank control horse urine matrix was used and spiked with different concentrations of analytes to form a standard curve using either alpha-tocopherol-d6 or chlorpropamide as the internal standard. Inter-day and intra-day statistics were performed to evaluate the method for accuracy (90% to 116%) and precision (0.75% to 14%). Matrix effects, percent recovery, and stability were also assessed. The method successfully analyzed alpha-carboxyethyl hydroxychroman (α-CEHC), alpha-carboxymethylbutyl hydroxychromans (α-CMBHC), gamma-carboxyethyl hydroxychroman γ-CEHC, and α-TP concentrations in urine to determine a baseline levels of analytes in healthy horses, and can be used to determine concentrations of vitamin E metabolites in equine urine allowing for its evaluation as a diagnostic approach in the treatment of eNAD/EDM.

A ratiometric benzothiazole-based fluorescence probe for selectively recognizing HClO and its practical applications

A ratiometric probe (HBT-HBZ) bearing 2-hydrazino benzothiazole and 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzaldehyde for sensing HClO with high selectivity and sensitivity is reported in this article. The fluorescence intensity ratios (I470 nm/I572 nm) of the probe with different concentrations of analyte showed excellent selectivity and a linear response to minor changes in HClO. The detection limit of 24 nmol/L suggests that the sensor is very sensitive to HClO. According to the series of performed experiments, HBT-HBZ has practical applications, such as the detection of HClO residues in tap water, which has been rarely reported. In addition, confocal laser microscopy experiments confirmed that HBT-HBZ can selectively recognize HClO in HeLa cells. A ratiometric probe (HBT-HBZ) for sensing hypochlorous acid (HClO) with high selectivity and sensitivity is reported in this article. The probe exhibited high selectivity for HClO among other ROS, RNS and anions. In addition, HBT-HBZ has some practical applications such as the analysis of the HClO content in tap water. Furthermore, confocal fluorescence microscopy imaging showed that HBT-HBZ can be applied for detecting HClO in living cells.

Quantitative Analysis of Food Additives in a Beverage using High Performance Liquid Chromatography and Diode Array Detection Coupled with Chemometrics.

In many countries, the levels of synthetic food additives causing harm to humans have been determined and their use has been controlled by legal regulations. Sensitive, accurate and low-cost analysis methods are required for food additive determination. In this study, a fast high performance liquid chromatography-diode array detection (HPLC-DAD) analytical methodology for quantification of sodium benzoate, potassium sorbate, ponceau 4R, and carmoisine in a beverage was proposed. Partial least squares (PLS) and principal component regression (PCR) multivariate calibration methods applied to chromatograms with overlapped peaks were used to establish a green and smart method with short isocratic elution. A series of synthetic solutions including different concentrations of analytes were used to test the prediction ability of the developed methods. The average recoveries for all target analytes were in the range of 98.27-101.37% with average relative prediction errors of less than 3%. The proposed chemometrics-assisted HPLC-DAD methods were implemented to a beverage successfully. Analysis results from sodium benzoate, potassium sorbate, ponceau 4R, and carmoisine in a beverage by PLS-2 and PCR were statistically compared with conventional HPLC. The HPLC methods coupled with the PLS-2 and PCR algorithm could provide a simple, quick and accurate strategy for simultaneous determination of sodium benzoate, potassium sorbate, ponceau 4R, and carmoisine in a beverage sample.

SERS Activity of Silver Nanosphere, Triangular Nanoplates, Hexagonal Nanoplates and Quasi-Spherical Nanoparticles: Effect of Shape and Morphology

In this work, we prepared different morphologies of silver nanoparticles: nanosphere, triangular nanoplates, hexagonal nanoplates, and quasi-spherical shapes, through one-step synthesis. Hydrogen peroxide was used as the oxidizing agent during the reduction of silver nitrate by sodium borohydride, in the presence of tri-sodium citrate and poly-vinyl-pyrrolidone. The obtained silver nanoparticles were fully characterized by UV-Vis spectroscopy, Dynamic Light Scattering and Scanning Electron Microscopy, and successfully used as Surface Enhanced Raman Scattering (SERS) substrates. The effect of shape and morphology on the Raman scattering enhancement was evaluated by using methylene blue as target molecules. The Raman measurements demonstrated that the prepared substrates are reliable and sensitive with analytical enhancement factors, estimated to be around 105 with a concentration of methylene blue 1 μM. When triangular and hexagonal nanoplates were tested with different concentrations of analyte, they demonstrated a good linearity in Raman intensity with a good detection of methylene blue 0.1 μM.

Simultaneous HPLC-DAD determination of pseudoephedrine HCl, sodium benzoate, sunset yellow, and methyl paraben in syrup preparation by use of partial least squares and principal component regression

The chromatographic methods (high performance liquid chromatography-diode array detection (HPLC-DAD)) combined with a partial least squares (type PLS-2) and principal component regression (PCR) were applied to the simultaneous determination of pseudoephedrine hydrochloride, sodium benzoate, sunset yellow, and methyl paraben in a syrup sample. By the aid of chromatographic data, the developed methods successfully solved the overlapped chromatographic peaks in HPLC analysis with the short elution time. A series of synthetic solutions containing different concentrations of analytes were used to check the prediction ability of the proposed methods. Satisfactory results were obtained by the PLS-2 and PCR methods for synthetic samples, with the average recoveries ranging from 98.33–100.20% to 98.44–100.07%, respectively. The developed methods were applied to a commercial syrup sample and the results were statistically compared with the conventional HPLC method. Considering the advantages of the chemometrics-assisted HPLC-DAD strategy, such as a short analysis time, simple and low-cost mobile phase, rapid sample preparation, the proposed methods could be an attractive alternative and green chromatography strategy for the determination of pseudoephedrine hydrochloride, sodium benzoate, sunset yellow, and methyl paraben in pharmaceutical samples.

Counterflow gradient electrophoresis for focusing and elution.

Counterflow gradient electrofocusing uses the bulk flow of a liquid solution to counterbalance the electrophoretic migration of an analyte. When either the bulk velocity or the electrophoretic velocity of the analyte is made to vary across the length of the channel, there exists a unique zero-velocity point for the analyte. This focusing method enables simultaneous separation and concentration of different analytes. The high resolution and sensitivity achieved are similar to that of isoelectric focusing, which separates analytes based on their isoelectric points, but the key difference is that analytes will instead focus based on their electrophoretic mobility. Dynamically changing the applied voltage or the counterflow rate over time will shift the zero-velocity point, and therefore allows the focused analytes to pass through a fixed detection point, or elute from the separation channel. Throughout the review, a number of different counterflow gradient techniques will be discussed, along with their recent advancements and potential applications.

Liquid chromatography–mass spectrometry/mass spectrometry method development for the determination of carbaryl residue in honey

Background: Honey, the natural sweetener, obtained from Apis mellifera (honey bees) possesses many medicinal properties. Intensive use of carbamate insecticide in agricultural land not only contaminates the crop but also affects the honey and honey matrices. Hence, this study focused on the analysis of insecticide in honey. Objective: Liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) method development for the determination of Carbaryl insecticide in honey and Comparisons of different extraction techniques to determine the efficiency of extraction process. Materials and Methods: The LC-MS/MS method was developed by optimizing the multiple reaction monitoring (MRM) parameters. Further, the comparison study was done for the optimized extraction techniques such as quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and ultrasound solid phase extraction (SPE) in the developed method. The validation was studied for the developed method as well as the extraction techniques to confirm the robustness of the developed method. Results: The validation study showed good accuracy for the developed method for the concentration from 2 to 9 ppb of the working solution. Limit of detection for the developed method was 0.08 and 0.05 ppb for the fragments 145.1 m/z and 127.1 m/z, respectively. Moreover, limit of quantification for the fragment 145.1 m/z was 0.24 ppb and for 127.1 m/z was 0.16 ppb. The average accuracies for the developed method of both the fragments (145.1 m/z and 127.1 m/z) were 98.51% and 98.15%, respectively. Recovery percentage for optimized QuEChERS ranged from 107% to 112% and for the ultrasound-SPE and from 107% to 118% of the honey samples which were spiked with three different concentrations of analyte. Conclusion: From the validation, it was confirmed that the developed method was robust and simple and provides better sensitivity and intensity and low consumption of chemicals. Thus, the developed method can be used for the routine analysis of carbaryl in honey.

Parallel comparison of in situ Raman and NIR spectroscopies to simultaneously measure multiple variables toward real-time monitoring of CHO cell bioreactor cultures

For the first time, the ability of in situ Raman and Near Infrared (NIR) spectroscopies to predict in real-time the concentration of viable Chinese Hamster Ovary (CHO) cells, glucose, lactate, glutamine, ammonium and antibodies in bioreactors has been compared in parallel. PLS models were developed using Raman and NIR spectra recorded at same time points and in same cultures. Multivariate figures of merit were established to thoroughly compare the performances of models. Raman spectroscopy was found to better predict concentrations of glucose, lactate and antibody, while NIR spectroscopy predicted better glutamine and ammonium ion concentrations. By applying the models developed on spectra recorded continuously during a batch culture, both spectroscopies were able to monitor simultaneously the general trends of the concentration of different analytes, while Raman predictions were more accurate at the beginning of the culture. Moreover, other chemometric methods (partial least square regression of type 2 and spectral combination) were tested, but leading to only limited model performance improvements. Both spectroscopies are suitable tools for real-time monitoring of cell culture bioprocesses, while Raman spectroscopy provides several advantages concerning sensibility, selectivity and limit of detection. These results provide useful information for academic researchers and pharmaceutical industries to choose the most adequate spectroscopic technology for their cell culture bioprocesses.

Coupled electrochemical-chemical procedure used in construction of molecularly imprinted polymer-based electrode: a highly sensitive impedimetric melamine sensor

A novel molecularly imprinted sensor was fabricated and used for the impedimetric detection of melamine. Considering the identity of polymeric film and the pK a of a melamine template, an effective procedure was established to construct the MIP-based melamine sensor. The proposed method is based on the electropolymerization of pyrrole (Py) in the presence of melamine on the electrochemically reduced graphene oxide modified glassy carbon electrode (ERGO/GCE), followed by treatment with the solution of 1% H2O2 in alkaline water/CH3CN-mixed solvents. The surface morphology and the electrical feature of molecularly imprinted polymer (MIP) were characterized by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The EIS was also utilized to transduce the change of charge transfer resistance (R ct) at the interface of polymer film-electrolyte, after subsequent incubation of electrode in the solution containing different concentrations of analyte, and consequently, a linear response was obtained over the range of 4.0 to 240 nM with a detection limit of 0.83 nM (S/N = 3). The effect of possible interferences on the response of sensor was studied, and the results confirmed the good selectivity of the proposed device for melamine assay. The MIP sensor was successfully applied to determine melamine in a multiple concentration-spiked milk sample.

Optical and acoustic sensing using Fano-like resonances in dual phononic and photonic crystal plate

We perform a theoretical study based on the transmissions of optical and acoustic waves normally impinging to a periodic perforated silicon plate when the embedded medium is a liquid and show the existence of Fano-like resonances in both cases. The signature of the resonances appears as well-defined asymmetric peaks in the phononic and photonic transmission spectra. We show that the origin of the Fano-like resonances is different with respect to the nature of the wave. In photonic, the origin comes from guided modes in the photonic plate while in phononic we show that it comes from the excitation of standing waves confined inside the cavity coming from the deformation of the water/silicon edges of the cylindrical inclusion. We finally use these features for sensing and show ultra-sensitivity to the light and sound velocities for different concentrations of analytes.

P1160 : ANTI-GP210 antibody is a serological marker for the progression to end-stage enlarged liver with micronodular cirrhosis in primary biliary cirrhosis

multivariate analyses identified, however, taurochenodeoxycholic acid (2.85±0.76 vs 0.40±0.29mM, p < 0.001), 1-myristoyl-2hydroxy-sn-glycero-3-phosphocholine (2.38±0.31 vs 1.33±0.07mM, p < 0.0001), and docosapentaenoic acid (1.15±0.46 vs 0.20±0.02mM, p < 0.0001), as the analytes independently associated with pruritus. Conclusions: Pruritus in patients with primary biliary cirrhosis is associated with marked changes in the circulating concentration of different analytes, thus identifying one bile acid, one lysophosphatidylcholine and a free fatty acid as the major potential triggers of itching of cholestasis.

Genotoxicity of chemical compounds identification and assessment by yeast cells transformed with GFP reporter constructs regulated by the PLM2 or DIN7 promoter.

Yeast cells transformed with high-copy number plasmids comprising a green fluorescent protein (GFP)-encoding gene optimized for yeast under the control of the new DIN7 or PLM2 and the established RNR2 and RAD54 promoters were used to assess the genotoxic potential of chemical compounds. The activity of potential DNA-damaging agents was investigated by genotoxicity assays and by OxoPlate assay in the presence of various test compounds. The fluorescence signal generated by GFP in response to DNA damage was related to the different concentrations of analytes and the analyte-dependent GFP synthesis. The use of distinct DNA damage-inducible promoters presents alternative genotoxicity testing strategies by selective induction of promoters in response to DNA damage. The new DIN7 and PLM2 systems show higher sensitivity than the RNR2 and RAD54 systems in detecting 4-nitroquinoline-N-oxide and actinomycin D. Both DIN7 and PLM2 systems are able to detect camptothecin while RNR2 and RAD54 systems are not. Automated laboratory systems with assay performance on 384-well microplates provide for cost-effective high-throughput screening of DNA-damaging agents, reducing compound consumption to about 53% as compared with existing eukaryotic genotoxicity bioassays.

Temperature Sensing Using Photonic Crystal Fiber Filled With Silver Nanowires and Liquid

A temperature sensor based on photonic crystal fiber (PCF) surface plasmon resonance (SPR) is proposed in this paper. We use the dual function of the PCF filled with different concentrations of analyte and silver nanowires to realize temperature sensing. The proposed sensor has been analyzed through numerical simulations and demonstrated by experiments. The results of the simulations and experiments show that a blue shift will be obtained with the temperature increase, and different concentrations will change the resonance wavelength and confinement loss. Temperature sensitivity is as high as 2.7 $\hbox{nm}/^{\circ}\hbox{C}$ with the experiment, which can provide a reference for the implementation and application of a PCF-based SPR temperature sensor or other PCF-based SPR sensing.

A lower limit of detection for atrazine was obtained using bioluminescent reporter bacteria via a lower incubation temperature

The present article reports on the influence of various atrazine concentrations to the response of genetically modified Escherichia coli TV1061 bacterial cells while modulating the experimental conditions. Interesting increases of bioluminescence signals are recorded for E. coli TV1061 bacteria in the presence of 10μg/mL atrazine concentration named “high-toxicity bacteria alert” when compared with 1μg/mL –10fg/mL atrazine termed “low-toxicity bacteria alert”. Detecting the effect of atrazine via its effect on bioluminescence of bacteria has been carried out by two consecutive measurements (fresh and overnight modes) at different concentrations of analyte. We have shown that a more precise discrimination at lower-toxicity concentrations can be obtained through overnight incubation of bacteria with the analyte at 4°C. In addition, centrifugation of bacterial cells and analyte dilutions has been performed in order to ensure a better interaction between the insoluble atrazine pesticide and the bacterial cells.