An approach to select linear regression model in bioanalytical method validation

Strategies for assessing the limit of detection in voltammetric methods: comparison and evaluation of approaches

The realm of analytical chemistry continues to struggle with defining and evaluating the limit of detection in analytical methods in the sense that a multitude of definitions, criteria, caveats, and methods have been proposed, developed, and adopted across disciplines. The last decade has seen a surge in the growth of electrochemical methods and studies in the field of forensic science and forensic chemistry. While many disciplines within forensic science have established method validation guidelines, the historical and current lack of electrochemical methods within forensic laboratories throughout the United States has left a major gap in knowledge, inhibiting the adoption and utilization of electrochemistry, which may serve as a powerful tool in many subdisciplines of forensics. As such, this work begins this discussion by focusing first on the limit of detection (LOD), with application toward both qualitative and quantitative methods. Both inorganic (ferrocyanide and lead) and organic (diphenylamine, naltrexone, and acetaminophen) target analytes were analyzed via two common voltammetry methods: cyclic voltammetry and square-wave voltammetry. The LOD for each analyte was estimated and/or calculated following a variety of literature-described methods and compared. The accuracy and reliability of these LOD characteristics based on the experimental data is described herein along with suggestions and recommendations. This manuscript is intended to compare the resulting LOD values from various methods and provide a starting point for the incorporation of electrochemistry into the forensic science laboratory, beginning a focused discussion on the development of validation guidelines and parameters needed for the adoption of this technology in forensic laboratories in order to meet the standards required by the criminal justice system.

A linear validation method of analytical procedures based on the double logarithm function linear fitting

BACKGROUND

The ICH Q2(R1) guideline defines linearity as its ability to obtain test results which are directly proportional to the concentration of the analyte. However, the coefficient of determination typically used is limited to evaluating the response function rather than the linearity of results, the current guidelines fail to provide a method for assessing the linearity of results.

RESULTS

The paper presents a data analysis method to validate the linearity of results. The method demonstrates the degree of data proportionality by applying double logarithm function linear fitting and solves the problem of setting the acceptance criterion by investigating the relationship between the slope, working range ratio, and maximum error ratio. In principle, this method has advantages over the coefficient of variation and recovery rate recommended by the ICH M10 guideline. Moreover, the relative error data show that the double logarithm function is more effective in overcoming heteroscedasticity than straight-line fitting.

SIGNIFICANCE

This method is more consistent with the linear definition outlined in ICH Q2 guidelines and has the potential to further clarify the concept and validation method of linearity in the future.

A comprehensive LC-MS/MS method for simultaneous analysis of 65 synthetic cannabinoids in human hair samples and application to forensic investigations

Synthetic cannabinoids (SCs) represent a diverse class of new psychoactive substances characterized by extensive substance variety and severe abuse implications. The current situation of synthetic cannabinoid abuse in China is getting worse, with an increasing number of SC variants emerging. Therefore, it is imperative to improve synthetic cannabinoid detecting methods to align with the prevalent abuse situation in the region. In this study, a reliable and validated liquid chromatography-tandem mass spectrometry method was developed for the qualitative and quantitative analysis of 65 SC analogues in human hair samples. The validation results demonstrated satisfactory linearity (r ≥ 0.99) within the range of 25-2500 pg/mg for each SC analogue. The method exhibited limits of detection ranging from 10 to 15 pg/mg and limits of quantification ranging from 25 to 40 pg/mg. The relative standard deviations of intra-day precision and inter-day precision were below 15 %. Furthermore, negligible matrix effects were observed, with recovery rates ranging from 85.70 % to 119.43 %. Analysis of abuser demographics revealed that the primary group engaged in SC analogue abuse consisted of adolescents, predominantly males, accounting for 79.5 % of cases. Among the suspected individuals, ADB-BUTINACA and MDMB-4en-PINACA were the most frequently detected substances. The present study develops a highly sensitive analytical method and provides a comprehensive overview of the prevalence of SC abuse in the eastern region of China.

Electroanalytical biosensor based on GOx/FCA/PEG-modified SWCNT electrode for determination of glucose

This paper describes a simple electrochemical sensing platform based on single-walled carbon nanotube (SWCNT) electrodes for glucose detection. The device fabrication using O2-plasma treatment allows precision and uniformity for the construction of three SWCNT electrodes on the flexible plastic substrate. Glucose assay can be simply accomplished by introducing a glucose sample into the fabricated biosensor. The marked electrocatalytic and biocompatible properties of biosensors based on SWCNT electrodes with the incorporation of ferrocenecarboxylic acid and polyethylene glycol enable effective amperometric measurement of glucose at a low oxidation potential (0.3 V) with low interferences from coexisting species. The device shows efficient electroanalytical performances with high sensitivity (5.5 μA·mM−1·cm−2), good reproducibility (CV less than 3%), and long-term stability (over a month). A linear range of response was found from 0 to 10 mM of glucose with a fast response time of 10 s. This attractive electroanalytical device based on GOx/FCA/PEG/SWCNT electrodes offers a promising system to facilitate a new approach for diverse biosensors and electrochemical devices.

Analysis of N7-(2-carbamoyl-2-hydroxyethyl)guanine in dried blood spot after food exposure by Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry

N⁷-(2-carbamoyl-2-hydroxyethyl)guanine (N7-CAG) is a DNA adduct formed by glycidamide, which is the metabolite of acrylamide. Acrylamide can be found in foods containing reducing sugars and asparagine that are heated at high temperatures. Analysis of N7-CAG was performed in Dried Blood Spot (DBS) samples from 25 subjects of group test who consumed a lot of acrylamide-containing foods and 25 subjects of negative control group. This study aimed to determine whether there is a significant difference in the levels of N7-CAG between the two groups. DBS samples were extracted using the QIAamp DNA Mini Blood Kit and analyzed using Ultra High Performance Liquid Chromatography–Tandem Mass Spectrometry (UHPLC-MS/MS). Separation was performed using an Acquity UPLC BEH C₁₈ column (2.1 mm × 100 mm; 1.7 μm), eluted a flow rate of 0.1 ml/min under an isocratic of mobile phase of 0.1% formic acid and acetonitrile. The bioanalytical method of N7-CAG in DBS with allopurinol as the internal standard by using UHPLC-MS/MS has been validated. The calibration curve range of N7-CAG obtained was 10–300 ng/ml with a coefficient of correlation of 0.997. The results of the analysis on 25 test group subjects showed that the concentration of N7-CAG ranged from 1.87 to 23.71 ng/ml, while the 25 subjects in the negative group ranged from 1.18 to 8.47 ng/ml. The results of the Mann Whitney test showed that there was a significant difference in the levels of N7-CAG between the test group and the negative control group with p value less than 0.001.

Development, validation, and uncertainty measurement of HPLC-DAD method for determination of some free amino acids in infant formula and medical food products for inborn errors of metabolism

This research aims at determining some free amino acids in amino acid-based infant formulas and amino acid-modified medical foods for inborn errors of metabolism to prove their quality. A method based on high-performance liquid chromatography and diode array detection was developed and validated. Then, overall uncertainty was estimated by the bottom-up approach. Applying the weighted least squares regression method suggested good linearity with coefficient of determinations ≥ 0.9960. The limits of detection were calculated between 0.01 and 0.28 μg/mL. The most repetitive recovery values were obtained in the range of 91-108%, with RSDs ≤ 15%. The expanded uncertainties were below 20% for most amino acids. The contributions of linear regression and repeatability are two main factors in estimating overall uncertainty. The results offer this method as a simple and easy procedure for analyzing free amino acids in seven powdered medical foods designed for phenylketonuria, maple syrup urine disease, methylmalonic, and propionic acidemia.

Sulfonated graphene oxide impregnated cellulose acetate floated beads for adsorption of methylene blue dye: optimization using response surface methodology

New multi-featured adsorbent beads were fabricated through impregnation of sulfonated graphene (SGO) oxide into cellulose acetate (CA) beads for fast adsorption of cationic methylene blue (MB) dye. The formulated SGO@CA composite beads were thoroughly characterized by several tools including FTIR, TGA, SEM, XRD, XPS and zeta potential. The optimal levels of the most significant identified variables affecting the adsorption process were sequential determined by the response surface methodology (RSM) using Plackett–Burman and Box–Behnken designs. The gained results denoted that the surface of SGO@CA beads displayed the higher negative charges (− 42.2 mV) compared to − 35.7 and − 38.7 mV for pristine CA and SGO, respectively. In addition, the floated SGO@CA beads demonstrated excellent floating property, fast adsorption and easy separation. The adsorption performance was accomplished rapidly, since the adsorption equilibrium was closely gotten within 30 min. Furthermore, the adsorption capacity was greatly improved with increasing SGO content from 10 to 30%. The obtained data were followed the pseudo-second order kinetic model and agreed with Langmuir adsorption isotherm model with a maximum adsorption capacity reached 234.74 mg g⁻¹. The thermodynamic studies designated the spontaneity and endothermic nature of MB dye adsorption. Besides, the floated beads exposed acceptable adsorption characteristics for six successive reuse cycles, in addition to their better adsorption selectivity towards MB dye compared to cationic crystal violet and anionic Congo red dyes. These findings assume that the formulated SGO@CA floated beads could be used effectively as highly efficient, easy separable and reusable adsorbents for the fast removal of toxic cationic dyes.

A comprehensive review on the decontamination of lead(ii) from water and wastewater by low-cost biosorbents

The disadvantages of conventional methods in water and wastewater management including the demand for high energy consumption, the creation of secondary toxic sludge, and operation cost are much too high for developing countries. However, adsorption using low-cost biosorbents is the most efficient non-conventional technique for heavy metals removal. The high adsorption capacities, cost-effectiveness, and the abundance of agricultural waste materials in nature are the important parameters that explain why these biosorbents are economical for heavy metals removal. The present investigation sought to review the biosorption of lead [Pb(ii)] onto low-cost biosorbents to understand their adsorption mechanism. The review shows that biosorption using low-cost biosorbents is eco-friendly, cost-effective, and is a simple technique for water and wastewater treatment containing lead(ii) ions. The batch biosorption tests carried out in most studies show that Pb(ii) biosorption by the low-cost biosorbents is dependent on biosorption variables such as pH of the aqueous solution, contact time, biosorbent dose, Pb(ii) initial concentration, and temperature. Furthermore, batch equilibrium data have been explored in many studies by evaluating the kinetics, isothermal and thermodynamic variables. Most of the studies on the adsorptive removal of Pb(ii) were found to follow the pseudo-second kinetic and Langmuir isotherm models with the thermodynamics variables suggesting the feasibility and spontaneous nature of Pb(ii) sequestration. However, gaps exist to increase biosorption ability, economic feasibility, optimization of the biosorption system, and desorption and regeneration of the used agricultural biosorbents.

Development and validation by statistical treatment of stability indicating RP-HPLC method for quantification of Orlistat in Orlistat-loaded solid dispersion

Background

Most of the analytical methods reported for the estimation of Orlistat were complex, expensive, and deficient in reproducibility with no or very less informative regarding various statistical methods and equations used for the validation purpose. This study provides a fast, accurate, descriptive, and precise isocratic reversed phase high-performance liquid chromatographic (HPLC) method using Waters Spherisorb 5 μm Octadecyl-silica-2 (250 × 4.6 mm) column, for the estimation of Orlistat in bulk drug and pharmaceutical formulations with minimized drug extraction steps. The drug was detected in an analytical column with mobile phase comprising a mixture of methanol, acetonitrile, and 2% phosphoric acid in the ratio of 85:14:1 v/v/v at flow rate of 1 ml/min with elution monitoring at 215.0 nm.

Results

The retention time for Orlistat was found to be 5.9 min with sharp and proper peak. The linearity was covered over the concentration range of 1.00–10.00 μg/ml (r2 = 0.9997) with a limit of detection and limit of quantitation 0.06 and 0.2 μg/ml, respectively. The developed analytical technique was found to be validated for all the parameters within the acceptance criteria of ICH guidelines. The mean ± standard deviation (SD) recoveries of Orlistat were 99.87 ± 0.45.

Conclusion

The optimized method was well precise, accurate, sensitive, stability indicating, and tested with all statistical parameters. Thus, the method can be conveniently used in quality control and routine analysis of Orlistat containing solid dispersions and other formulations. The main advantage of the developed method was its high specificity for the estimation of Orlistat in presence of various degradation products resulting from stress conditions and formulation excipients.

Development, validation, and application of an HPLC-MS/MS method for quantification of oxidized fatty acids in plants

Oxylipins constitute a huge class of compounds produced by oxidation of long-chain unsaturated fatty acids either chemically (by radicals such as reactive oxygen species, ROS) or enzymatically (by lipoxygenases, LOX; cyclooxygenases, COX; or cytochrome P450 pathways). This process generates fatty acids peroxides, which can then be further modified in a broad range to epoxy, hydroxy, keto, ether fatty acids, and also hydrolyzed to generate small aldehydes and alcohols. In general, oxylipins are present in almost all living organisms and have a wide range of signaling, metabolic, physiological, and ecological roles depending on the particular organism and on their structure. In plants, oxylipins have been extensively studied over the past 35 years. However, these studies have focused mainly on the jasmonates and so-called green leaves volatiles. The function of early LOX products (like keto and hydroxy fatty acids) is yet not well understood in plants, where they are mainly analyzed by indirect methods or by GC-MS what requires a laborious sample preparation. Here, we developed and validated a straightforward, precise, accurate, and sensitive method for quantifying oxylipins in plant tissues using HPLC-MS/MS, with a one-step extraction procedure using low amount of plant tissues. We successfully applied this method to quantify the oxylipins in different plant species and Arabidopsis thaliana plants treated with various biotic and abiotic stress conditions.

Validation of the Developed Zero-Order Infrared Spectrophotometry Method for Qualitative and Quantitative Analyses of Tranexamic Acid in Marketed Tablets

(1) Background: The functional groups present in tranexamic acid allow direct infrared detection analysis. This study aimed to develop, apply, and validate an infrared spectrophotometry method used for qualitative and quantitative analyses of tranexamic acid in marketed tablets. (2) Methods: This was a descriptive observational study that consisted of several stages: determining the specific wavenumber for analysis, obtaining a simple linear regression equation, analyzing tranexamic acid both qualitatively and quantitatively, and validating the developed method for routine analysis. (3) Results: The peak analysis obtained a range of baseline wavenumbers from 1679.17 to 1295.25 cm⁻¹. The regression equation obtained was Y = 310.8527 × X + 0.9718, and the coefficient of determination (R²) obtained was 0.9994. The tranexamic acids in marketed tablets overall have a similarity index value of more than 0.90 and overall have levels ranging between 97.0% and 103.0%. The infrared spectrophotometry method that was successfully developed, applied, and validated for qualitative and quantitative analyses of tranexamic acid in marketed tablets meets the requirements both qualitatively and quantitatively of the tablet monograph. (4) Conclusions: The infrared spectrophotometry method has been validated and meets the requirements for accuracy, precision, detection limit, quantitation limit, linearity, range, and specificity.

CCWeights: an R package and web application for automated evaluation and selection of weighting factors for accurate quantification using linear calibration curve

Summary

The accuracy of any analytical method is highly dependent on the selection of an appropriate calibration model. Here, we present CCWeights, an R package for automated assessment and selection of weighting factors for accurate quantification using linear calibration curve. Additionally, CCWeights includes a web application that allows users to analyze their data using an interactive graphical user interface, without any programming requirements. The workflow and features of CCWeights are illustrated by the analyses of two datasets acquired by liquid chromatography-mass spectrometry (LC-MS). The resulting quantification table can be directly utilized for further model assessment and subsequent data analysis.

Availability and implementation

CCWeights is publicly available on CRAN repository (https://cran.r-project.org/web/packages/CCWeights), with source code available on GitHub (https://github.com/YonghuiDong/CCWeights) under a GPL-3 license. The web application can be run locally from R console using a simple command "runGui()". Alternatively, the web application can be freely accessed for direct online use at https://bcdd.shinyapps.io/CCWeights/.

Supplementary information

Supplementary data are available at Bioinformatics Advances online.

A Stability-Indicating Ultra Performance Liquid Chromato-Graphic (UPLC) Method for the Determination of a Mycophenolic Acid-Curcumin Conjugate and Its Applications to Chemical Kinetic Studies

A simple, precise, and accurate reversed-phase ultra-performance liquid chromatographic (UPLC) method was developed and validated for the determination of a mycophenolic acid-curcumin (MPA-CUR) conjugate in buffer solutions. Chromatographic separation was performed on a C18 column (2.1 × 50 mm id, 1.7 µm) with a gradient elution system of water and acetonitrile, each containing 0.1% formic acid, at a flow rate of 0.6 mL/min. The column temperature was controlled at 33 °C. The compounds were detected simultaneously at the maximum wavelengths of mycophenolic acid (MPA), 254 nm, and curcumin (CUR), or MPA-CUR, at 420 nm. The developed method was validated according to the ICH Q2(R1) guidelines. The linear calibration curves of the assay ranged from 0.10 to 25 μg/mL (r² ≥ 0.995, 1/x² weighting factor), with a limit of detection and a limit of quantitation of 0.04 and 0.10 μg/mL, respectively. The accuracy and precision of the developed method were 98.4-101.6%, with %CV < 2.53%. The main impurities from the specificity test were found to be MPA and CUR. Other validation parameters, including robustness and solution stability, were acceptable under the validation criteria. Forced degradation studies were conducted under hydrolytic (acidic and alkaline), oxidative, thermal, and photolytic stress conditions. MPA-CUR was well separated from MPA, CUR, and other unknown degradation products. The validated method was successfully applied in chemical kinetic studies of MPA-CUR in different buffer solutions.

Effects of low lead exposure on sperm quality and sperm DNA methylation in adult men

INSTRUCTION

Lead (Pb) exposure is a risk factor for male infertility, but the epigenetic changes in sperm DNAattributable to lead exposure is poorly defined.

METHODS

In this study, we investigated whether low Pb exposure (<  10 µg/dL) affects the sperm quality. Blood, urine, and semen samples of 297 men of childbearing age were analyzed for all relevant parameters. Based on the blood Pb level (BLL), participants were allocated to RL (0-2.5 µg/dL), RM (2.5-5 µg/dL), and RH (5-10 µg/dL) groups. The 5-methylcytosine and 5-hydroxymethylcytosine patterns in the sperm DNA were identified using methylated DNA immunoprecipitation and hydroxymethylated DNA immunoprecipitation sequencing.

RESULTS

The non-progressive motility (NP) was significantly increased and associated with global hypomethylation of sperm DNA in the RH group compared with the RL group, indicating that aberrant sperm methylation due to low Pb exposure is possibly associated with reduced sperm motility. The hypomethylated promoter regions were primarily enriched in the calcium (Ca) homeostasis pathway. Further, the interaction between Ca and Pb was associated with sperm rapid progressive motility and asthenospermia risk, although no significant methylation abnormality was observed in those with BLL  <  5 µg/dL. When BLL was  >  5 µg/dL or when predicting NP, no significant Pb-Ca interaction was observed.

DISCUSSION

Overall, our results indicate that aberrant DNA methylation of the Ca homeostasis pathway, induced by low Pb exposure, is the potential cause for reduced sperm velocity.

Development and Validation of a Method for Quantification of Favipiravir as COVID-19 Management in Spiked Human Plasma

In the current work, a simple, economical, accurate, and precise HPLC method with UV detection was developed to quantify Favipiravir (FVIR) in spiked human plasma using acyclovir (ACVR) as an internal standard in the COVID-19 pandemic time. Both FVIR and ACVR were well separated and resolved on the C18 column using the mobile phase blend of methanol:acetonitrile:20 mM phosphate buffer (pH 3.1) in an isocratic mode flow rate of 1 mL/min with a proportion of 30:10:60 %, v/v/v. The detector wavelength was set at 242 nm. Maximum recovery of FVIR and ACVR from plasma was obtained with dichloromethane (DCM) as extracting solvent. The calibration curve was found to be linear in the range of 3.1-60.0 µg/mL with regression coefficient (r2) = 0.9976. However, with acceptable r2, the calibration data's heteroscedasticity was observed, which was further reduced using weighted linear regression with weighting factor 1/x. Finally, the method was validated concerning sensitivity, accuracy (Inter and Intraday's % RE and RSD were 0.28, 0.65 and 1.00, 0.12 respectively), precision, recovery (89.99%, 89.09%, and 90.81% for LQC, MQC, and HQC, respectively), stability (% RSD for 30-day were 3.04 and 1.71 for LQC and HQC, respectively at -20 °C), and carry-over US-FDA guidance for Bioanalytical Method Validation for researchers in the COVID-19 pandemic crisis. Furthermore, there was no significant difference for selectivity when evaluated at LLOQ concentration of 3 µg/mL of FVIR and relative to the blank.

Green synthesized plant-based silver nanoparticles: therapeutic prospective for anticancer and antiviral activity

Nanotechnology holds an emerging domain of medical science as it can be utilized virtually in all areas. Phyto-constituents are valuable and encouraging candidates for synthesizing green silver nanoparticles (AgNPs) which possess great potentials toward chronic diseases. This review gives an overview of the Green approach of AgNPs synthesis and its characterization. The present review further explores the potentials of Phyto-based AgNPs toward anticancer and antiviral activity including its probable mechanism of action. Green synthesized AgNPs prepared by numerous medicinal plants extract are critically reviewed for cancer and viral infection. Thus, this article mainly highlights green synthesized Phyto-based AgNPs with their potential applications for cancer and viral infection including mechanism of action and therapeutic future prospective in a single window.

Removal of a cationic dye from aqueous solution by a porous adsorbent templated from eco-friendly Pickering MIPEs using chitosan-modified semi-coke particles

Porous materials prepared from high internal phase emulsions have been attracting much attention in recent years, but two major defects related to the high consumption of organic solvent and surfactants are always difficult to solve.

An Advanced Statistical Approach Using Weighted Linear Regression in Electroanalytical Method Development for Epinephrine, Uric Acid and Ascorbic Acid Determination

In this study, the use of weighted linear regression in the development of electrochemical methods for the determination of epinephrine (EP), ascorbic acid (AA), and uric acid (UA) is presented. The measurements were performed using a glassy carbon electrode and square-wave voltammetry (SWV). All electroanalytical methods were validated by determination of the limit of detection, limit of quantification, linear concentration range, accuracy, and precision. The normal distribution of all data sets was checked using the quantile-quantile plot and Kolmogorov-Smirnov statistical tests. The heteroscedasticity of the data was tested using Hartley's test, Bartlett's test, Cochran's C test, and the analysis of residuals. The heteroscedastic behavior was observed with all analytes, justifying the use of weighted linear regression. Six different weighting factors were tested, and the best weighted model was determined using relative percentage error. Such statistical approach improved the regression models by giving greater weight on the values with the smallest error and vice versa. Consequently, accuracy of the analytical results (especially in the lower concentration range) was improved. All methods were successfully used for the determination of these analytes in real samples: EP in an epinephrine auto-injector, AA in a dietary supplement, and UA in human urine. The accuracy and precision of real sample analysis using best weighted model gave satisfactory results with recoveries between 95.21-113.23% and relative standard deviations between 0.85-7.98%. The SWV measurement takes about 40 s, which makes the presented methods for the determination of EP, AA, and UA a promising alternative to chromatographic techniques in terms of speed, analysis, and equipment costs, as the analysis is performed without organic solvents.

Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.