Mean Relative Standard Deviation Research Articles

Speed of sound measurement and mapping in transparent materials by impulsive stimulated Brillouin microscopy

Impulsive stimulated Brillouin scattering (ISBS) is a variant of stimulated Brillouin scattering, which can overcome the shortcomings of the long acquisition time of traditional Brillouin microscopy. We introduce the difference between ISBS and other Brillouin microscopies in calculating longitudinal modulus. The Brillouin frequency shift obtained by ISBS is only related to the system parameters and the speed of sound (SOS) in the sample, not to the refractive index. Non-contact SOS measurement of homogeneous samples is an important application of Brillouin scattering, used in the early study of Brillouin spectroscopy and the mechanical properties of liquids. However, the measurement requires prior knowledge of the sample refractive index, which limits the measurement of the unknown refractive index sample. Here, we propose a method to measure the SOS based on ISBS, which in principle avoids the need for refractive index parameters. The SOS of several liquids are measured and compared with the standard values. The mean relative standard deviation is 1.13%. Moreover, we measure the SOS of a mixture of ethanol and water to demonstrate an application of measuring SOS without refractive index information. We also demonstrate the high spatial resolution of ISBS with a methanol-filled PDMS sample.

Chemometric method development for the determination of naringin and verapamil

BackgroundBy resolving complicated spectra from drug combinations, chemometric techniques are valuable for multi-component investigation. The capacity to properly estimate combinations of components without separating drugs from their mixture is one of the benefits of chemometric analysis approaches over traditional analytical methods. These approaches are easy to use and sensitive even to the lowest concentrations. They are also practical, affordable, and cost-effective. In the current study, the chemometric aided spectrophotometric approach was used to evaluate the two drugs naringin and verapamil. The approach is multidimensional and based on chemometrics, which includes an orthogonal partial least square method that is a new refinement of the partial least squares regression analysis method. With this technique, no conversions are made to the spectrum that overlaps the two drugs. The tools UV-PROBE, SIMCA version 17, and excel were used to process the chemometric data.ResultsAccording to results from an orthogonal partial least square model, the mean percent recovery and relative standard deviation for the combination of verapamil with naringin were 100.80/1.19 and 100.836/1.35, respectively.The calibration model was used to predict known synthetic mixtures.This method shows good consistency in recovery ranging between 98.92 and 103.59% for VER and from 96.21 to 101.84% NAR. As saying the synthetic mixture revealed that it had a high percentage of purity.ConclusionsThe proposed chemometric method can estimate the quantitative amount of pharmaceuticals based on their dosage forms. This approach meets the requirements for the international conference on harmonization's (ICH) analytical criteria, such as precision and accuracy.Graphical

Simultaneous determination of emtricitabine and tenofovir disoproxil fumarate in pharmaceutical preparations using spectrophotometric, chemometric and chromatographic methods

Simple, accurate and sensitive spectrophotometric, chemometric and chromatographic methods were used for the simultaneous determination of emtricitabine (ETC) and tenofovir disoproxil fumarate (TDF) in tablets. In 1st derivative spectrophotometry, the first derivative spectra of the solution of ETC and TDF in water were recorded as ?? = 4 nm and the first derivative absor-bances were measured at the zero-crossing points at 297.3 and 281.2 nm for ETC and TDF, respectively. In ratio of the 1st derivative spectrophotometry measurements were recorded at 239.0 and 270.2 nm for ETC and TDF, respect-ively. Then analytical signals were measured at the wavelengths corresponding to either maximum or minimum for both drugs. For these spectrophotometric methods Beer?s law is obeyed in the concentration range of 2?15 ?g mL-1 for both drugs. As chemometric method, the PLS technique was used. In chroma-tographic method, the separation was achieved on a C18 column with DAD (262 nm) and isocratic elution of methanol, acetonitrile and 0.1 % orthophos-phoric acid in the volume ratio of 40:40:20, respectively, containing the mob-ile phase. The mean recovery and the relative standard deviation of the methods were found as 97.51?100.17 % and 0.55?1.26 % respectively. All these methods were statistically compared, and they were successfully applied to a pharmaceutical preparation.

Applicable Pharmacokinetic Study: Development and Validation of Bioanalytical LC-MS/MS Method for Simultaneous Determination of Tipiracil, Trifluridine and Its Two Metabolites 5-Trifluoromethyluracil, 5-Carboxy 2′-Deoxyuridine in Rat Plasma

A novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the simultaneous determination of tipiracil (TIP), trifluridine (FTD), and their metabolites, 5-trifluoromethyluracil (FTY) and 5-carboxy-2′-deoxyuridine (5CDU), in rat plasma. This method is highly sensitive, specific, and fast. Paracetamol (PAR) is used as an internal standard (IS). Using acetonitrile-induced protein precipitation, the analytes were extracted from a plasma sample and separated on a Waters BEH C18 (1.7 μm particle size, 50 mm × 2.1 mm ID) column protected by a security guard cartridge (C18, 4 × 2.0 mm). The isocratic mobile phase was made up of methanol and water containing 0.1% formic acid (80:20, v/v) at a flow rate of 0.5 mL/min for 4 min. The quantification was performed using a positive electrospray ionization (ESI) interface and a multiple-reaction monitoring (MRM) mode. The MRM transitions employed were m/z 242.96 → 182.88 for TIP, 296.96 → 116.86 for FTD, 180.98 → 139.85 for FTY, 272.96 → 156.86 for 5CDU, and 151.97 → 92.68 for IS. The validated method complied with the guidelines set by the US-FDA over on a linear concentration range of 5–4000 ng/mL for FTD, FTY, and 5CDU, and 5–1000 ng/mL for TIP. The coefficient of determination (r2) was equal to or greater than 0.997. The corresponding lower limits of detection (LLOD) were 1.5 ng/mL for FTD, FTY, and 5CDU and 1.0 ng/mL for TIP. The recoveries of all analytes from rat plasma ranged from 88.67% to 112.18%, and the mean relative standard deviation (RSD) of accuracy and precision result was less than or equal to 6.84%. FTD, FTY, 5CDU, and TIP demonstrated adequate stability throughout the various circumstances examined. Additionally, no matrix effects were identified for any of the analytes. The assay was effectively utilized to conduct a pharmacokinetic study in rats following the oral administration of FTD and TIP at a dosage of 5.6 mg/kg, with a ratio of 1:0.5 for FTD and TIP, respectively. This indicates that the suggested approach is suitable for future clinical research. The pharmacokinetic parameters Cmax (maximum concentration), Tmax (time to reach maximum concentration), t1/2 (half-life), AUC0-24 (area under the concentration–time curve from 0 to 24 h), AUC total (total area under the concentration–time curve), Ke (elimination rate constant), Vd (volume of distribution), and CL (clearance) of all analytes were assessed. The assay developed exhibits significant advancements compared to earlier bioanalytical methods documented in the literature. These improvements include high sensitivity, specificity, and efficacy in high throughput analysis of complex matrices. Additionally, the assay offers a shorter run time and smaller sample volume (50 μL).

Extended total number density compensation for uranium determination by laser-induced breakdown spectroscopy

BackgroundVariations in plasma properties among spectra and samples lead to significant signal uncertainty and matrix effects in laser-induced breakdown spectroscopy (LIBS). To address this issue, direct compensation for plasma property variations is considered highly desirable. However, reliably compensating for the total number density variation is challenging due to inaccurate spectroscopic parameters. For reliable compensation, a total number density compensation (TNDC) method was presented in our recent work, but its applicability is limited to simple samples because of its strict assumptions. In this study, we propose a new pre-processing method, namely extended TNDC (ETNDC), to reduce signal uncertainty and matrix effects in the more complex analytical task of uranium determination. ResultsETNDC reflects the total number density variation with a weighted combination of spectral lines from all major elements and incorporates temperature and electron density compensation into the weighting coefficients. The method is evaluated on yellow cake samples and combined with regression models for uranium determination. Using the typical validation set and line combination, the mean relative standard deviation (RSD) of U II 417.159 nm in validation samples decreases from 4.92% to 2.27%, and the root mean square error of prediction (RMSEP) and the mean RSD of prediction results decrease from 4.81% to 1.93% and from 1.92% to 1.56%, respectively. Furthermore, the results of 10 validation sets and 216 line combinations show that ETNDC outperforms baseline methods in terms of average performance and robustness. SignificanceFor the first time, ETNDC explicitly addresses the temperature and electron density variations while compensating for the total number density variation, where the inaccurate spectroscopic parameters are avoided by fitting related quantities using concentration information. The method demonstrates effective and robust improvement in signal repeatability and analytical performance in uranium determination, facilitating accurate quantification of the LIBS technique.

Imprinted polymer/reduced graphene oxide-modified glassy carbon electrode-based highly sensitive potentiometric sensing module for imidacloprid detection

A sensitive and highly selective potentiometric sensor for imidacloprid detection (IMD) is presented. Reduced graphene oxide (rGO) was used to modify a glassy carbon electrode in the fabrication of this sensor. The rGO is coated with IMD molecularly imprinted polymer (MIP), which serves as a sensing compound for herbicide recognition. Under ideal circumstances, a linear range of 0.5 µM-1.0 mM was measured, with a detection limit of 0.2 µM IMD. The method exhibits great selectivity towards the IMD's determination, according to the examination of the effects of potentially interfering species. For the direct potentiometric detection of IMD in several pesticide formulation samples, the assay method has been validated and shown to be adequate. The obtained recovery ranges from 94.5 to 106.4 % of the nominal or spiked concentration, with a mean relative standard deviation of 1.3 %. The applicability outcomes of using the presented sensor were contrasted with those attained by high-performance liquid chromatography (HPLC). There was no discernible difference between the suggested and HPLC procedures. Due to the sensitive membrane's and the liquid junction's proximity, this module's use permits applications with a small sample volume. The proposed sensor's effectiveness in a complicated matrix points to applications for rapid detection and tests for quality assurance and control in the agro-industry.

A theoretical model for the oblique impact of fragments

A portion of the casing charge's fragments would strike the target plate and ricochet when it exploded close to or inside a steel structure, like a ship or manufacturing facility. Considering the high pressure, high temperature, and high strain rate during the impact, the kinematic characteristics of the ricochet fragment, such as ricochet velocities and ricochet angle, are challenging to describe using the existing methods. In this study, a novel theoretical model of ricochet fragment kinematics under oblique impact was proposed, and the corresponding initial assumptions and application conditions were presented. A series of oblique impact experiments was conducted to obtain the differences in kinematic characteristics under various impact velocities and impact angles. The parameters of the proposed theoretical model were determined. The accuracy of the theoretical model was verified by using 921A hull steel target plate. The average relative error and standard deviation of ricochet velocity were 7.4 % and 2.3 %, respectively, and the mean relative error and standard deviation of the ricochet angle are 11.2 % and 1.1 %, respectively. The results showed that the theoretical model can predict the ricochet velocity well, and the error of ricochet angle increased due to the different pile-up effect of different strength target plates, but it was still within the reasonable range. In addition, the effects of the impact velocity and angle on the ricochet velocity and angle were analyzed. When the impact angle was small, the ricochet angle and velocity were affected by both impact velocity and angle. When the impact angle increased to a certain Angle (>64.2°), the ricochet velocity only increased linearly with the impact velocity. The ricochet angle increased with the increase in the impact angle. When the impact velocity was less than 400 m/s, the ricochet angle increased with the increase in the impact velocity. When the velocity is greater than 400 m/s, the ricochet angle decreased with the increase in the impact velocity. When the impact angle was greater than 57° and the impact velocity was greater than 400 m/s, the ricochet angle was almost only related to the impact angle. The results indicate that the proposed model has good accuracy and can have high application value in terminal effects, safety engineering, and structural defense fields.

A sensitive ZIF-67/ MWCNTs composite-based sensor for the detection of sunset yellow in food and beverages

This study introduces an innovative sensing platform designed for the detection of sunset yellow (SY). The platform employs a composite electrode material comprising of a zeolitic imidazole framework (ZIF-67) and multiwalled carbon nanotubes (MWCNTs) on a glassy carbon electrode (GCE). The synergy between ZIF-67 and MWCNTs leads to an enhancement in the electrochemical sensing behaviour for SY oxidation. Notably, the electrostatic interaction between ZIF-67 particles and MWCNTs results in a 6.26-fold increase in the current response. Additionally, the charge transfer resistance (Rct) was remarkably low, measuring at only 114 Ω. Under ideal conditions, the SY sensor demonstrated a minimum detectable concentration (LOD) and quantifiable concentration (LOQ) of 0.103 and 0.343 µM, respectively. The detection of SY was effectively conducted in snacks and beverages, showcasing its practical applicability. The results obtained demonstrate exceptional mean relative standard deviations (RSDs) < 1 %, indicating high precision. Additionally, the recovery ranges achieved, ranging from 95 % to 105 %, validate the sensor’s reliability and accuracy. Furthermore, the chemical reactivity of SY was investigated through density functional theory (DFT) calculations, which identifies the redox-reactive site in SY, aligning with the postulated reaction mechanism observed in cyclic voltammograms. Monte Carlo (MC) simulations provide insight into the electrostatic and covalent interactions between the functional groups of the analyte and the designed sensor. This novel sensing approach demonstrates significant promise in the identification and surveillance of artificial food colourants in the food manufacturing sector.

Improving signal stability and analysis accuracy in laser-induced breakdown spectroscopy by multi-directional collection

Poor spectral signal stability has always been a key problem limiting the development of laser-induced breakdown spectroscopy (LIBS). The spatiotemporal inhomogeneity of the plasma between pulses is one of the direct causes of the poor stability of the spectral signal. In this paper, a multi-directional plasma emission light collection method is proposed and its performance is tested. The main idea is to suppress the difference caused by the spatial fluctuation of the plasma by increasing the acquisition range and size. Plasma emission spectra of 11 kinds of mixed lithium ore standard samples are collected with 7 different collection schemes. The experimental results show that the intensity and stability of Ca, Al, and Mn spectral lines collected from multiple directions significantly improved compared to the single lateral and single coaxial collection methods. The mean characteristic spectral intensities are increased by a factor of 4.41 and 6.84, respectively. Meanwhile, the mean relative standard deviation of multiple-directional (1.95%) is much smaller than that of the single lateral (4.31%) or single coaxial (4.16%). The mean coefficient of determination of the univariate linear regression is also improved from RL2¯=0.8722 (single lateral) and RC2¯=0.8849 (single coaxial) to RC+4L2¯=0.9351 (multiple-directional). The innovative and developed system based on LIBS and the multi-directional plasma collection method can effectively improve the detection repeatability and accuracy and has application values in sample measurement.

Analysis of surface roughness in optical coherence elastography using a novel phantom

Compression optical coherence elastography (OCE) has shown promise in detecting diseases, such as breast cancer, based on changes in the elasticity of tissue. While the mechanical models used in OCE assume a flat surface, tissue typically exhibits surface topography that can lead to inaccurate estimation of elasticity in OCE images (elastograms). The coupling of surface topography and heterogeneous mechanical properties in tissue make it challenging to study the relative impact of surface roughness on image formation. To address this, we developed mechanically homogeneous phantoms that accurately replicate the surface topography of human breast tissue. Surface topography of breast tissue specimens was captured in three-dimensional (3-D) optical coherence tomography (OCT) scans. Molds replicating the surface roughness of tissue were generated using 3-D modelling and 3-D printing. The phantoms were then fabricated in the molds using polydimethylsiloxane. OCT was used to validate the accuracy of the phantom surface topography and the phantoms were then used to determine the impact of surface roughness in compression OCE elastograms. Surface roughness phantoms were shown to accurately reflect the surface topography of six breast tissue specimens with a correlation of 0.96 ± 0.03. When imaged with a variant of compression OCE called quantitative micro-elastography, surface roughness resulted in a slight decrease in elasticity accuracy with a mean percentage error of 8.2 % for a flat phantom compared to 11.7 % for the roughness phantom, and a larger decrease in elasticity precision, or sensitivity, with a mean relative standard deviation of 9.4 % for the flat phantom compared to 21.2 %, for the roughness phantom. Our results show that contrast in elastograms moderately correlated with the phantom surface profile (r = 0.59, p < 0.001) and that surface roughness introduces spatially-varying elasticity that should be considered in the analysis of elastograms in compression OCE.

Weakly supervised learning-based 3D bladder reconstruction from 2D ultrasound images for bladder volume measurement.

Accurate measurement of bladder volume is necessary to maintain the consistency of the patient's anatomy in radiation therapy for pelvic tumors. As the diversity of the bladder shape, traditional methods for bladder volume measurement from 2D ultrasound have been found to produce inaccurate results. To improve the accuracy of bladder volume measurement from 2D ultrasound images for patients with pelvic tumors. The bladder ultrasound images from 130 patients with pelvic cancer were collected retrospectively. All data were split into a training set (80 patients), a validation set (20 patients), and a test set (30 patients). A total of 12 transabdominal ultrasound images for one patient were captured by automatically rotating the ultrasonic probe with an angle step of 15°. An incomplete 3D ultrasound volume was synthesized by arranging these 2D ultrasound images in 3D space according to the acquisition angles. With this as input, a weakly supervised learning-based 3D bladder reconstruction neural network model was built to predict the complete 3D bladder. The key point is that we designed a novel loss function, including the supervised loss of bladder segmentation in the ultrasound images at known angles and the compactness loss of the 3D bladder. Bladder volume was calculated by counting the number of voxels belonging to the 3D bladder. The dice similarity coefficient (DSC) was used to evaluate the accuracy of bladder segmentation, and the relative standard deviation (RSD) was used to evaluate the calculation accuracy of bladder volume with that of computed tomography (CT) images as the gold standard. The results showed that the mean DSC was up to 0.94 and the mean absolute RSD can be reduced to 6.3% when using 12 ultrasound images of one patient. Further, the mean DSC also was up to 0.90 and the mean absolute RSD can be reduced to 9.0% even if only two ultrasound images were used (i.e., the angle step is 90°). Compared with the commercial algorithm in bladder scanners, which has a mean absolute RSD of 13.6%, our proposed method showed a considerably huge improvement. The proposed weakly supervised learning-based 3D bladder reconstruction method can greatly improve the accuracy of bladder volume measurement. It has great potential to be used in bladder volume measurement devices in the future.

Applicable pharmacokinetic study: Development and validation of bioanalytical LC-MS/MS method for the simultaneous quantification of cytarabine and glasdegib used for the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is characteristic by high concentrations of immature bone marrow myeloid cells. Glasdegib (DaurismoTM, GSB) in combination with low dose cytarabin (DepocytTM, CTB) have recently been approved by the US Food and Drug Administration for the treatment of newly diagnosed AML in patients over 75 years of age or who have comorbidities that are prohibitive to intensive induction chemotherapy. However, the pharmacokinetic characteristics of the CTB and GSB is yet unknown. This study developed a selective, sensitive and fast analytical method using liquid chromatography-electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify of CTB and GSB in rat plasma using duvelisib as internal standard (IS). The LC-MS/MS instrument was performed in the ESI interface operating at positive ionization and multiple reaction monitoring (MRM) mode. The CTB and GSB with the IS were extracted from rat plasma by using cation exchange solid-phase extraction cartridge before the analysis. The cartridge gave high recovery rates for both drugs without interference from plasma endogenous. Chromatographic separation was performed on reversed-phase polar-100 column (100 mm × 2.1 mm, 3 µm), with an isocratic mobile phase consisted of a mixture of water containing 0.1% formic acid and acetonitrile (85:15, v/v, pH 3.2) at a flow rate of 0.4 mL/min and the process of analysis was run for 3.5 min. The developed method was validated as per the FDA guidelines over a linear concentration range of 5–3000, for both CTB and GSB with high correlation coefficient (r2 ≥ 0.99). The lower limits of detection (LLOD) were 2.0 ng/mL for both drugs. The overall recoveries of CTB and GSB from rat plasma were in the range of 93.93–101.43%, and the mean relative standard deviation (RSD) of the results was 2.99%. The validated-method was successfully applied for the first time, to a pharmacokinetic study on concurrent oral administration of CTB and GSB in rats (12.0 mg/kg of CTB and 8.5 mg/kg of GSB). The maximum plasma concentration (Cmax) for CTB and GSB was 2312.23 ± 448.26 ng/mL and 1710.61 ± 166.04 ng/mL achieved at 2.83 ± 0.14 h and 2.39 ± 0.10 h, respectively. The AUC0-∞ for CTB and GSB was found to be 8592.49 ± 1714.12 and 4527.67 ± 390.01 ng/mL.h; respectively. The elimination half-life (t1/2kel) of CTB and GSB in rat plasma, were determined to be 2.00 ± 0.19 h and 1.58 ± 0.13 h, respectively. The newly developed approach stands out for its high extraction recovery and absence of matrix interference. Findings further demonstrated the high sensitivity of the developed method, which allowed for effective routine tests in pharmacokinetic investigations with LLOD of 2.0 ng/mL and a run time of 3.5 min.

Characterization of a high throughput approach for large scale retention measurement in liquid chromatography

Many contemporary challenges in liquid chromatography—such as the need for “smarter” method development tools, and deeper understanding of chromatographic phenomena—could be addressed more efficiently and effectively with larger volumes of experimental retention data than are available. The paucity of publicly accessible, high-quality measurements needed for the development of retention models and simulation tools has largely been due to the high cost in time and resources associated with traditional retention measurement approaches. Recently we described an approach to improve the throughput of such measurements by using very short columns (typically 5 mm), while maintaining measurement accuracy. In this paper we present a perspective on the characteristics of a dataset containing about 13,000 retention measurements obtained using this approach, and describe a different sample introduction method that is better suited to this application than the approach we used in prior work. The dataset comprises results for 35 different small molecules, nine different stationary phases, and several mobile phase compositions for each analyte/phase combination. During the acquisition of these data, we have interspersed repeated measurements of a small number of compounds for quality control purposes. The data from these measurements not only enable detection of outliers but also assessment of the repeatability and reproducibility of retention measurements over time. For retention factors greater than 1, the mean relative standard deviation (RSD) of replicate (typically n=5) measurements is 0.4%, and the standard deviation of RSDs is 0.4%. Most differences between selectivity values measured six months apart for 15 non-ionogenic compounds were in the range of +/- 1%, indicating good reproducibility. A critically important observation from these analyses is that selectivity defined as retention of a given analyte relative to the retention of a reference compound (kx/kref) is a much more consistent measure of retention over a time span of months compared to the retention factor alone. While this work and dataset also highlight the importance of stationary phase stability over time for achieving reliable retention measurements, we are nevertheless optimistic that this approach will enable the compilation of large databases (>> 10,000 measurements) of retention values over long time periods (years), which can in turn be leveraged to address some of the most important contemporary challenges in liquid chromatography. All the data discussed in the manuscript are provided as Supplemental Information.

Determination of glyphosate and its derivative, aminomethylphosphonic acid, in human urine by gas chromatography coupled to tandem mass spectrometry and isotope pattern deconvolution

An analytical method for the simultaneous determination of glyphosate (GLY) and its main derivative, aminomethyl-phosphonic acid (AMPA), in human urine has been developed using gas chromatography coupled to tandem mass spectrometry (MS/MS) operated in multiple reaction monitoring mode (MRM). Sample preparation involved dilution of urine with water and derivatization with a mixture of trifluoroacetic acid anhydride and trifluoroethanol. Derivatization conditions such as reaction time and temperature, derivative stability, injection solvent, MS ionization mode and MS-MS transitions, among others, were studied to obtain the highest method sensitivity. The target compounds were initially quantified by the isotope dilution method using isotopically labelled analogs of GLY and AMPA as internal standards. However, due to spectral overlap between GLY and labelled GLY in the selected quantitative transition, a quantification method based on isotope pattern deconvolution (IPD) has been developed. The instrumental limits of detection were 0.05 ng mL−1 for both compounds, while the method detection limits were 0.39 and 0.25 ng mL−1, for AMPA and GLY, respectively. The mean recoveries from urine and water spiked at different concentrations were 77 and 69% for AMPA and 90 and 102% for GLY, respectively, with mean relative standard deviations of 8–10% (urine samples, n = 12) and 3.6–4% (water samples, n = 6). Once validated, the feasibility of the method was tested by determination of AMPA and GLY in human urine samples from people living close to agricultural areas. The developed method affords the determination of these compounds at trace concentrations in complex matrices such as urine, avoiding elaborate handling and cleanup steps. Isotope pattern deconvolution has proven to be a successful alternative to calibration curve for GLY overriding the method uncertainties associated to spectral overlapping.

Quantitative Representation of Water Quality Biotoxicity by Algal Photosynthetic Inhibition.

The method based on the photosynthetic inhibition effect of algae offers the advantages of swift response and straightforward measurement. Nonetheless, this effect is influenced by both the environment and the state of the algae themselves. Additionally, a single parameter is vulnerable to uncertainties, rendering the measurement accuracy and stability inadequate. This paper employed currently utilized photosynthetic fluorescence parameters, including Fv/Fm(maximum photochemical quantum yield), Performance Indicator (PIabs), Comprehensive Parameter Index (CPI) and Performance Index of Comprehensive Toxicity Effect (PIcte), as quantitative toxicity characteristic parameters. The paper compared the univariate curve fitting results with the multivariate data-driven model results and investigated the effectiveness of Back Propagation(BP) Neural Network and Support Vector Machine for Regression (SVR) models to enhance the accuracy and stability of toxicity detection. Using Dichlorophenyl Dimethylurea (DCMU) samples as an example, the mean Relative Root Mean Square Error (RRMSE) corresponding to the optimal parameter PIcte for the dose-effect curve fitting was 1.246 in the concentration range of 1.25-200 µg/L. On the other hand, the mean RRMSEs corresponding to the results of the BP neural network and SVR models were 0.506 and 0.474, respectively. Notably, BP neural network exhibited excellent prediction accuracy in the medium-high concentration range of 7.5-200 µg/L, with a mean RRSME of only 0.056. Regarding the stability of the results, the mean Relative Standard Deviation (RSD) of the univariate dose-effect curve results was 15.1% within the concentration range of 50-200 µg/L. In contrast, the mean RSDs for both BP neural network and SVR results were less than 5%. In the concentration range of 1.25-200 µg/L, the mean RSDs were 6.1% and 16.5%, with the BP neural network performing well. The experimental results of Atrazine were analyzed to further validate the effectiveness of the BP neural network in improving the accuracy and stability of results. These findings provided valuable insights for the development of biotoxicity detection by using the algae photosynthetic inhibition method.

Can salivary lactate be used as an anaerobic biomarker?

Salivary lactate has been suggested as a non-invasive anaerobic biomarker in sports medicine for decades, yet has not been widely applied until now. This study aimed to explore possible issues related to its application and suggest directions for future method improvement. A liquid chromatography-mass spectrometry (LC-MS) method for the determination of salivary lactate was developed, validated and applied on saliva samples collected from a group of professional sprinters (n=20). The samples were collected via chewing a cotton ball for one minute and centrifuging it afterwards. The evaluation included variation with mouth rinse times, consistency at different sampling times, change after treadmill or cycle ergometer trainings, and association with blood lactate. Sample sizes were calculated prior to the study. One-way analysis of variance (ANOVA), intra-class correlation coefficients (ICC) and relative standard deviation (RSD) were used to evaluate data variances. Pearson correlation was applied to show correlation between salivary and blood lactate. Effect sizes and power were calculated following ANOVA and correlation analyses. The RSD of the LC-MS method was 19.70%. Salivary lactate concentration was affected by mouth rinse times before sampling (ANOVA p=0.025, η 2=0.40, 1-β=0.99, ICC = 0.23, mean RSD of four sampling = 55.30%), and stabilized after mouth rinsing for three times. The concentrations at resting state across three weeks were consistent at group level (ANOVA p=0.57, η 2=0.03, 1-β=0.20), but varied greatly individually (ICC = 0.22, mean RSD = 56.16%). Salivary lactate level significantly increased after treadmill and cycle ergometer trainings (ANOVA p=0.0002, η 2=0.46, 1-β=0.9999 and ANOVA p=0.0019, η 2=0.40, 1-β=0.9993, respectively), and displayed positive correlation with blood lactate concentration (r=0.61, p=0.0004, 1-β=0.9596). Significant difference between male and female participants was observed in none of the tests conducted in this study. Salivary lactate was found to be a potential anaerobic biomarker. However, reproducible methods for sample collection and analysis, as well as more knowledge on the secretion mechanism and pattern of salivary lactate are required to make it a practical anaerobic biomarker.

The importance of inspecting the inoculum’s methane production for estimating kinetic parameters in biochemical methane potential tests

The aim of this study was to improve the quality of estimations of the first-order kinetic constant k, in Biochemical Methane Potential (BMP) tests. The results showed that existing guidelines for BMP tests are not sufficient to improve the estimation of k. The methane production of the inoculum itself exerted a major influence on the estimation of k. A flawed value in k was correlated with a high endogenous methane production. Excluding blanks that showed a distinct lag-phase of >1 day and a mean relative standard deviation >10% during the first ten days of a BMP test helped to retrieve more consistent estimates for k. For improving the repeatability in the determination of k in BMP tests, it is strongly recommended to inspect the methane production rate of the blanks. The proposed threshold values may be applied by other researchers but need further verification with different data.

First Retrieval of Total Ozone Columns from EMI-2 Using the DOAS Method

The Environmental Trace Gases Monitoring Instrument 2 (EMI-2), a second-generation Chinese hyperspectral satellite-based spectrometer, was launched on 7 September 2021. The total ozone column (TOC) product, which is one of the most important elements of the EMI-2 mission, is required for monitoring the Antarctic ozone hole and regional tropospheric ozone pollution. The first EMI-2 TOC results using the differential optical absorption spectroscopy (DOAS) method are presented in this study. Significant improvements, such as the fitting interval, reference spectrum, and iterative air mass factor (AMF) calculation scheme, were implemented in the EMI-2 TOC retrieval in comparison with the EMI DOAS TOC algorithm, thus generating more accurate reads. The monthly average EMI-2 DOAS TOCs in November 2021 were compared with the TROPOspheric Monitoring Instrument (TROPOMI) TOCs, and the results showed a good correlation (R = 0.99). The EMI-2 TOCs showed similar global spatial distributions to those of TROPOMI, with an overall mean relative bias and mean standard deviation of 0.16% and 2.38%, respectively. However, large differences (up to 7%) appeared in some polar areas near the coastline, which were mainly caused by different surface albedo algorithms. Furthermore, ground-based measurements from 20 stations across different latitudes derived from the World Ozone and Ultraviolet Radiation Data Center dataset were used to assess the accuracy of the EMI-2 DOAS TOCs, and they had a mean relative bias and mean standard deviation of 0.70% and 3.65%, respectively. These results indicate that the EMI-2 DOAS TOC algorithm can yield reliable global TOCs and monitor daily Antarctic TOCs for assessing the healing of ozone holes.

Closed-Vessel Conductively Heated Digestion System for the Elemental Analysis of Agricultural Materials by High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS)

Novel applications of the closed-vessel conductively heated digestion system (CHDS) are proposed to digest biomass, biochar, oyster shell flour, bone meal and swine manure for the determination of Ca, K, Mg, Na, Cu, Fe, Mn, and Zn by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). The performance of the digestion method using 14 and 7 mol L−1 HNO3 was checked by analyzing soil, rock, and plant certified reference materials (CRMs). For comparative purposes, all samples were analyzed after microwave-assisted digestion (MW-AD). Results obtained for most analytes by the closed-vessel conductively heated digestion system (CHDS) were in agreement with certified values and those attained by the comparative digestion method. The use of 7 mol L−1 HNO3 furnished lower blanks for most analytes and was effective to prepare challenging samples as biomass, biochar, shell and bone meal, swine manure, plants, soil, phosphate rock, and may be a good alternative for elemental determinations using most analytical techniques that rely on solution-based sample introduction systems. The detection limits (dry basis, mg kg−1) for Ca, Cu, Fe, K, Mg, Mn, Na, and Zn were 3, 0.4, 4, 4, 0.7, 0.4, 3, and 2, respectively. The mean relative standard deviations were close to 4.9% for closed-vessel conductively heated digestion (CHDS) and 5.9% for microwave-assisted digestion (MW-AD).

Residues of the Acaricides Abamectin, Hexythiazox, and Spiromesifen in Eggplant (Solanum melongena L.) Fruits Grown under Field Conditions in Najran, Saudi Arabia

The dissipation profiles of the acaricides abamectin, hexythiazox, and spiromesifen in the fruits of eggplant (Solanum melongena L.) grown under field conditions in Najran, Saudi Arabia, were studied. Extraction was performed with acetonitrile, and UPLC-MS/MS was used for quantification. Instead of conventional adsorbents, a 2-fold dilution of the sample extract quickly and efficiently reduced interfering co-extracts and matrix effects. The method was successfully validated according to EU regulations. The limit of quantification was set at 5 µg/kg for hexythiazox and spiromesifen and 20 µg/kg for abamectin. The mean recoveries and relative standard deviations were 88.6–98.7% and 5.2–12.4%, respectively. The method precision was evaluated at the LOQ level for each analyte and ranged from 6.7 to 15.7%, with good trueness (recovery) ranging from 85.7 to 97.2%. The matrix effect ranged from −2.2% to −4.6%, indicating negligible signal suppression. First-order kinetics were used to characterize the dissipation rates of abamectin, hexythiazox, and spiromesifen with half-lives (t1/2) of 2.11–2.42, 2.3–2.73, and 1.31–1.47 days, respectively, using the authorized and double authorized doses. Terminal residues were 0.028–0.331 mg/kg, 0.019–0.592 mg/kg, and 0.044–0.408 mg/kg, respectively, at 3, 7, and 10 days after the second treatment. According to the risk assessment results, the percentage of chronic dietary risk quotient was &lt;100, meaning that abamectin, hexythiazox, and spiromesifen are not considered a risk to human health. The preharvest interval (PHI) should be 7, 7, and 3 days, respectively, if the authorized dose is used, and 10, 10, and 3 days, respectively, if double the authorized dose is used. The current study can be a helpful resource for the responsible and safe use of the tested acaricides on eggplant fruits.