Relative Retention Times Research Articles

Application of Chemometrics and HPLC Fingerprint for Species Differentiation and Authentication of the Genus Pterocarpus

Pterocarpus species are well known for their nutritional and medicinal values, in order to examine the similarities or differences in the chemical profile of some common Pterocarpus species, four species of the genus namely; Pterocarpus erinaceus, P. mildbraedii, P. osun and P. santalinoides were analyzed using HPLC combined with Principal component analysis (PCA) and Hierarchical clustering analysis (HCA). This study aims to investigate the chemical fingerprints of the species and compare them in order to highlight the similarities in their chemical constituents. The ethanol extract of each sample was taken and filtered through a 0.45 μm millipore membrane filter and then transferred into the HPLC vial before injecting it into the HPLC machine. PCA and HCA were performed on the relative retention times and percentage peak composition. The species were chemically similar with nine (9) peaks in common, the most prominent peaks in all samples appeared at 3.26 min which corresponds to gallic acid (a known compound). Cluster analysis revealed some similar chemical variables with Gallic acid being the major compound in the Pterocarpus species and could be used as a marker compound for taxonomic purposes.

Structure-Kinetic Relationship for Drug Design Revealed by a PLS Model with Retrosynthesis-Based Pre-Trained Molecular Representation and Molecular Dynamics Simulation.

Drug design based on kinetic properties is growing in application. Here, we applied retrosynthesis-based pre-trained molecular representation (RPM) in machine learning (ML) to train 501 inhibitors of 55 proteins and successfully predicted the dissociation rate constant (koff) values of 38 inhibitors from an independent dataset for the N-terminal domain of heat shock protein 90α (N-HSP90). Our RPM molecular representation outperforms other pre-trained molecular representations such as GEM, MPG, and general molecular descriptors from RDKit. Furthermore, we optimized the accelerated molecular dynamics to calculate the relative retention time (RT) for the 128 inhibitors of N-HSP90 and obtained the protein-ligand interaction fingerprints (IFPs) on their dissociation pathways and their influencing weights on the koff value. We observed a high correlation among the simulated, predicted, and experimental -log(koff) values. Combining ML, molecular dynamics (MD) simulation, and IFPs derived from accelerated MD helps design a drug for specific kinetic properties and selectivity profiles to the target of interest. To further validate our koff predictive ML model, we tested our model on two new N-HSP90 inhibitors, which have experimental koff values and are not in our ML training dataset. The predicted koff values are consistent with experimental data, and the mechanism of their kinetic properties can be explained by IFPs, which shed light on the nature of their selectivity against N-HSP90 protein. We believe that the ML model described here is transferable to predict koff of other proteins and will enhance the kinetics-based drug design endeavor.

Evaluation of a Delta-9-Tetrahydrocannabinol Carboxylic Acid (Δ9-THC-COOH) Immunoassay and a Gas Chromatography-Mass Spectrometry (GC-MS) Method for the Detection of Delta-8-Tetrahydrocannabinol Carboxylic Acid (Δ8-THC-COOH).

Delta-8 tetrahydrocannabinol (Δ8-THC) is a naturally occurring or synthetically prepared cannabinoid that elicits psychological and physiological experiences commonly reported for its more infamous isomer, delta-9 tetrahydrocannabinol (Δ9-THC). Unlike Δ9-THC, Δ8-THC products are generally legal under federal law and there has been a rise in their usage. One of the main targets for detection and quantitation of Δ9-THC is its inactive metabolite, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (Δ9-THC-COOH). This study evaluated the ability of the currently used Δ9-THC-COOH immunoassay and gas chromatography-mass spectrometry (GC-MS) methods to detect 11-nor-9-carboxy-Δ8-tetrahydrocannabinol (Δ8-THC-COOH) and distinguish it from Δ9-THC-COOH. The EMIT II Plus® Cannabinoid immunoassay for Δ9-THC-COOH with a cutoff of 20 ng/mL showed positive results for Δ8-THC-COOH with concentrations of 30 ng/mL or higher. Although many of the ion fragments generated by mass spectrometry were found to overlap between the 2 compounds, the GC-MS method presently used to quantify Δ9-THC-COOH separated the 2 compounds sufficiently to identify them independently by relative retention time. Current immunoassays and GC-MS methods should be evaluated for the ability to detect and distinguish the presence of Δ8-THC-COOH.

Analytical method development and validation for the determination of Rifampicin, Isoniazid and Pyrazinamide in “Rifampicin, Isoniazid, Pyrazinamide and Ethambutol hydrochloride” tablets

A simple and efficient method for the quantification of rifampicin, isoniazid and pyrazinamide in a fixed dose combination of anti-tuberculosis drug product was developed and validated by using HPLC system. The separation of rifampicin, isoniazid and pyrazinamide was carried out on a Waters 2690, composed of a quaternary pump, autosampler and PDA detector by chromatographic technique. Empower 3 software was used for data acquisition and analysis. Optimization of chromatographic separations was achieved using Phenomenex curosil-pfp column (250 × 4.6 mm, 5 μm particle size), with gradient program using disodium hydrogen phosphate and sodium 1- octane sulfonate buffer solution (pH adjusted to 7.0) as mobile phase A and acetonitrile (100%) as mobile phase B at a flow rate of 0.8 mL/min and UV detection at 238 nm. Approximate relative retention times of isoniazid, pyrazinamide and rifampicin were found to be 0.89, 1.00 and 2.63 respectively.

Separation of Methanolic Leaf Extracts of Three Rutaceous Plants by Capillary Electrophoresis and High-Performance Liquid Chromatography Methods

Pharmacognosy Research,2023,15,2,392-398.DOI:10.5530/pres.15.2.042Published:February 2023Type:Original Article Authors:Chakravarthi Guntupalli, Narender Malothu, Ankarao Areti, Buchi N Nalluri, Praveen Sivadasu, and Narayanarao Alla Author(s) affiliations:Chakravarthi Guntupalli*, Narender Malothu, Ankarao Areti, Buchi N Nalluri, Praveen Sivadasu, Narayanarao Alla K L College of Pharmacy, Koneru Lakshmaiah Education Foundation, Vaddeswaram, Guntur, Andhra Pradesh, INDIA. Abstract:Introduction: In the phytochemical analysis of various multi component mixtures, Capillary electrophoresis (CE) method was considered as the best alternative tool due to high efficiency resolution separations, low solvent consumption and less maintenance costs. Materials and Methods: This study uses CE and high-performance liquid chromatography (HPLC) methods to evaluate the major components of methanolic leaf extract of Rutaceous plants. And also, to assess the purity of the components in isolated fractions and most importantly for the qualitative identification of the individual components of extracts based upon the relative retention time and UV profile. Results: The separation of the compounds in HPLC was attained by using ACE-5-C18 (250 x 4.6 mm) with a flow rate of 1.5 ml/min, with the UV detection at 254 nm and CE was equipped with a UV diode-array detector and bare, fused silica capillaries (56 cm 50 μm) with micro extended light path were used for the separations. Conclusion: Our study reveals that CE technique is a simple, economical and convenient method and shown high-resolution for multi-components found in plant extracts compared with HPLC profiles. Keywords:Capillary Electrophoresis, HPLC, Relative Retention Time, Rutaceae.View:PDF (425.61 KB)

Gram-scale preparation of quercetin supramolecular nanoribbons for intestinal inflammatory diseases by oral administration

Gastrointestinal (GI) tract, which possesses the largest surface area of mucosa in the body, is easily suffered from inflammatory damages under the exposure of external stimulations. Excessive reactive oxygen species (ROS) production and continuous oxidative stress in intestines can elicit local mucosal injury, accelerate mucosal ulceration, and amplify the inflammatory response. Thereby, antioxidant therapy is a potential strategy against intestinal inflammatory diseases. Herein, we demonstrate the gram-scale preparation of quercetin supramolecular nanoribbons (SNRs) by using free quercetin molecules as the sole building block for preventing and treating intestinal inflammatory diseases. Unlike current clinical medicines, which mainly confront with poor response and severe adverse effects via bloodstream delivery, our quercetin SNRs possess an excellent antioxidant activity in the harsh environments of GI tract, a relative long retention time in GI tract, an admirable metabolism in GI tract without burdening other organs, and a specific adhesion to the inflamed intestinal epithelium via electrostatic interactions. These advantages strongly guarantee the applications of quercetin SNRs as oral medicines for intestinal inflammatory diseases. After establishing the models of intestinal inflammatory diseases caused by irradiation and drug stimulations, our quercetin SNRs exhibit the promising protective and therapeutic effects for radiation-induced acute enteritis and dextran sulfate sodium (DSS)-induced acute colitis. Because the super easy and fast preparation procedure and the nearly 100% loading capacity of quercetin SNRs, the current work provides a supramolecular nanomedicine with great clinical translation potential against intestinal inflammatory diseases.

Analysis of teicoplanin impurities by two-dimensional ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

A two-dimensional ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry （2D-UPLC-Q/TOF-MS） method was established for the separation and structural analysis of the components in teicoplanin. This method effectively solved the problems associated with chromatographic systems， such as liquid chromatography-mass spectrometry （LC-MS）， which used a non-volatile phosphate buffer as the mobile phase and were not suitable for the rapid identification of impurities. Moreover， this method circumvented the complexities associated with locating and identifying impurities using the original method by re-establishing a chromatographic system suitable for LC-MS. In this study， for one-dimensional （1D） chromatography， the chromatographic separation was performed on an Octadecyl silica （ODS） hypersil column （250 mm×4.6 mm， 5 μm） with gradient elution using 3.0 g/L sodium dihydrogen phosphate buffer （pH 6.0）/acetonitrile=9/1 （v/v） as mobile phase A and 3.0 g/L sodium dihydrogen phosphate buffer （pH 6.0）/acetonitrile=3/7 （v/v） as mobile phase B. The column temperature was maintained at 30 ℃ and an ultraviolet detector was used at 254 nm for analysis. For 2D chromatography， desalting was performed on a Waters ACQUITY UPLC BEH C18 column （50 mm×2.1 mm， 1.7 μm） with gradient elution using ammonium formate buffer （pH 6.0） and acetonitrile as the mobile phases. The column temperature was maintained at 45 ℃. The MS data for the components and impurities were collected by positive ion electrospray ionization （ESI） using the full-information tandem MS mode （MSE）. The cone and nebulizer gas flow rates were set at 50 and 900 L/h， respectively. The ion source and nebulizer gas temperatures were set at 120 ℃ and 500 ℃， respectively. The ESI and cone needle voltages were set at 2500 and 60 V， respectively. The collision energy was set at 20-50 eV. The molecular formulas of the components and impurities were determined using their exact masses and isotope distributions， and the structural components and impurities of teicoplanin were deduced from their fragment ions according to the fragmentation pathway of the TA2-2 component. Moreover， the 10 components reported in the European Pharmacopoeia 10.0 were analyzed and 22 impurities of teicoplanin were identified by 2D-UPLC-Q/TOF-MS. Three new impurities and two characteristic fragment ions of the teicoplanin parent nucleus were detected， and the fragmentation pathway of TA2-2 was deduced. Using this method， 1D-UPLC is applicable for the accurate qualification of components based on relative retention times， and 2D-UPLC-Q/TOF-MS is suitable for the rapid identification of the structure of components based on their fragment ions. The results indicate that 2D-UPLC-Q/TOF-MS may be used to analyze the structure of impurities in teicoplanin based on their exact masses， isotope distributions， and fragment ions. The method is rapid， simple， and sensitive， which provides a novel strategy for the quality control and process optimization of teicoplanin.

Scribe: Next Generation Library Searching for DDA Experiments.

Spectrum library searching is a powerful alternative to database searching for data dependent acquisition experiments, but has been historically limited to identifying previously observed peptides in libraries. Here we present Scribe, a new library search engine designed to leverage deep learning fragmentation prediction software such as Prosit. Rather than relying on highly curated DDA libraries, this approach predicts fragmentation and retention times for every peptide in a FASTA database. Scribe embeds Percolator for false discovery rate correction and an interference tolerant, label-free quantification integrator for an end-to-end proteomics workflow. By leveraging expected relative fragmentation and retention time values, we find that library searching with Scribe can outperform traditional database searching tools both in terms of sensitivity and quantitative precision. Scribe and its graphical interface are easy to use, freely accessible, and fully open source.

Development and Validation of New Methods for Quality Control of the Antiviral Substance FAVIPIRAVIR

The introduction into the production of medicinal substances involves the creation of a pharmaceutical dossier, an important component of which is data on pharmaceutical development and quality control methods. The physico-chemical properties of the antiviral substance of favipiravir were investigated, and some basic sections of the analytical documentation were developed. With the help of a complex of physical, chemical, and physico-chemical methods of analysis, the "Identification" test was developed, and the structure of favipiravir was proven. Methods for the determination of related substances by the HPLC with UV detection and the assay of favipiravir by the acid-base titration method, suitable for substance quality control, have been developed. Relative retention times and correction factors for calculating their content are established for all impurities. The methods were validated on the parameters of specificity, accuracy, correctness, and linearity in the studied range of concentrations.

Synthesis, Isolation, Identification and Characterization of a Drug-Excipient Interaction Degradation Impurity in Pramipexole by HPLC, LC/MS and NMR

A drug-excipient interaction impurity associated with the degradation process of pramipexole was isolated. The impurity was detected during the stability study of pramipexole extended-release tablets. It was found at a relative retention time of 0.88 with respect to pramipexole, using the pramipexole gradient HPLC-UV detection method described in the USP. The structure of the impurity was identified and fully characterized using high resolution mass spectrometry, IR and NMR techniques, as presented herein. The degradation impurity was identified as (S)-N2-(methoxymethyl)-N6-propyl-4,5,6,7-tetrahydro-1,3-benzothiazole-2,6-diamine. The drug-excipient interaction mechanism of its formation was proposed. An efficient and straightforward synthetic approach was developed to prepare the degradation impurity to confirm its proposed degradation pathway and structure.

Simultaneous determination of five metabolites of nitrofurans including the metabolite nifursol in shrimp and fish by UPLC- MS/MS: in-house method validation according to commission implementing regulation (EU) 2021/808

For the simultaneous identification and quantification of five nitrofurans metabolites in farmed shrimp and fish, 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), 1-aminohydantoine (AHD), semicarbazide (SEM), and 3,5-dinitrosalicylic acid hydrazide (DNSH), an accurate, precise, and specific method was developed. The mixture of water and methanol (60/40; v/v) was found to be the final optimised solvent for injection. The analytical run duration was 7 min, and the mobile phase included 2 mM methanol and ammonium formate. The new reference point for action (RPA) of 0.50 µg kg−1 as per EC/1871/2019 was taken into consideration and evaluated for the performance characteristics as per the CIR (EC)/2021/808 criteria. Specificity, relative retention time (≤0.25%) relative ion ratio (≤40%), linearity (0.25 to 2.0 µg kg−1), trueness (between 82.8 and 118.1%), repeatability (RSDr ≤14%), within lab reproducibility (RSDwr ≤16.9%), CCα (0.32–0.36 μg kg−1), ruggedness and relative matrix effect (≤14.26%) achieved acceptable values.

Procedure for chromatography using mobile phase with high elution strength to recover tacrolimus from the fermentation broth

A simple, accurate, cost effective and precise method of reverse phase - high performance preparative liquid chromatography was developed to maximize recovery and yield of tacrolimus and to bring down the concentration of analog impurities with relative retention time (RRT) 0.94 and 1.2 less than 0.5%, the two impurities that affect the assay of the product. For the high performance preparative liquid chromatography, Kromacil-C8, 13 μm column consisting of 10*250mm I.D. was used with the flow rate of 3.925 ml/min and eluent was monitored at 210 nm. In isocratic mode, mobile phase containing KH2PO4 Buffer: Acetonitrile: Butanol of varying ratios was used for the resolution study. The retention time was analyzed and gradient run was carried out for the mobile phase ratio that gives maximum resolution. The gradient run was carried out for two different trials with mobile phase in two different lanes. Loading trials were carried out for the trials which gave maximum resolution. The samples were analyzed and the yield on load was calculated for all the runs. The gradient run with gradient time of 200 mins and mobile phase ratio 22.2:77.8 to 28.8:71.2 acetonitrile:butanol:buffer gave 82% yield on the basis of load which was found to be maximum among all the trials carried out. Adsorption isotherm parameters were determined for the same.

Utility of detecting fentanyl analogs during LC-MS/MS confirmation for positive fentanyl urine drug screens

Abstract Introduction Fentanyl immunoassays have considerable crossreactvitiy with fentanyl derivatives such as acetylfentanyl, acrylfentanyl, furanyfentanyl and the primary fentanyl metabolite norfentanyl. This poses substantial analytical challenges to clinical laboratories that confirm fentanyl by mass spectrometry and may lead to false negative confirmations in patients that have analogs or primarily metabolites in their urine. As a result, some laboratories have developed targeted liquid chromatography tandem mass spectrometry (LS-MS/MS) methods to detect analogs and/or metabolites. However, there is no data in the literature demonstrating the frequency of analog detection in urine drugs screens, and the potential false positive immunoassay rate as a result of analogs and metabolites that are undetected is not known. Of note, acetyl-, acryl- and furanyl-fentanyl analogs have been confirmed in our testing region, and they cross-react with the Ark Fentanyl I and II immunoassays. Methods Results from 6,192 urine drugs screens positive for fentanyl by immunoassay [ARK I fentanyl assay and ARK II fentanyl immunoassays between January 1, 2020 to December 31, 2021 performed on a Roche cobas c502 chemistry analyzer with confirmatory LC-MS/MS (Waters Xevo TLD) at the Barnes Jewish Hospital Laboratory (St. Louis, MO) were retrospectively extracted from the laboratory information system (Cerner). The confirmatory assay was clinically validated to detect fentanyl (0.3 ng/mL), norfentanyl (5 ng/mL), acetylfentanyl (1 ng/mL), acrylfentanyl (1 ng/mL), and furanylfentanyl (1 ng/mL). An internal standard mix was added to patient samples followed by vortexing, centrifugation, and separation of the supernatant over a 6min linear gradient using a 2.1 × 150 mm 1.8µm C18 column. Data were acquired in positive ion mode and resulted as positive if predefined criteria for relative retention time, product ion ratio, peak shape/resolution, and signal intensity were met. Results 84.8% of the samples (n= 5247) confirmed positive for fentanyl, norfentanyl or a fentanyl analog, whereas 15.2% (n=944) did not confirm by LC-MS/MS. Of the 5247 positive results, fentanyl alone was present in 1,279 (24.4%) specimens while norfentanyl alone was present in 235 (4.48%) specimens. Both fentanyl and norfentanyl were present in 3968 (75.6%) specimens. 239 (4.55%) specimens confirmed positive for acetylfentanyl, all of which (100%) had fentanyl and/or norfentanyl concurrently detected. Among 61 (1.16%) specimens which were positive for acrylfentanyl, fentanyl and/or norfentanyl were concurrently detected in 60 specimens, and 1 had neither fentanyl nor norfentanyl detected. Furanylfentanyl was undetected in all specimens. Conclusions The fentanyl analogs acetylfentanyl, acrylfentanyl, and furnaylfentanyl are infrequently detected in our patient population. Furthermore, the assessed analogs are almost exclusively detected in the presence of fentanyl and/or norfentanyl by LC-MS/MS confirmatory assays. This implies that fentanyl analogs may not be a common source of false positive results by fentanyl immunoassays.

The impact of ECMO lower limb cannulation on the aortic flow features under differential blood perfusion conditions

The purpose of this study is to investigate the impact of veno-arterial (VA) ECMO cannulation on hemodynamic distribution and organ perfusion within aorta under differential blood perfusion conditions. The total blood flow volume supplied by failure heart and ECMO keep constant, flow volume ratio of heart output (FVR-HO) increases from 0% to 100% and correspondingly flow volume ratio of ECMO (FVR-ECMO) decreases from 100% to 0%. The flow patterns within aorta, wall shear stress (WSS), oscillatory shear index (OSI), relative retention time (RRT) were analyzed. The locations of oxygenated and de-oxygenated blood mixing region (BMR) was influenced by FVR-HO. With FVR-HO increasing, BMR moves from proximal to distal side of heart. When FVR-HO was 0%, oxygenated blood supplied by ECMO completely perfuses the aortic vessels. High WSS appears in the iliac artery and abdominal aorta vessel walls closed to cannula position. When FVR-HO was in the range of 10%–30%, the BMR was in aortic arch. The higher OSI and RRT were exhibited in ascending aorta and aorta arch. When FVR-HO was 40% and 50%, the BMR was in ventral trunk for systolic period and in aortic arch for diastolic period. The higher OSI and RRT regions enlarge and metastasize to the descending aorta. When FVR-HO was larger than 50%, the BMR was in the downstream region of the renal artery. Of note, when FVR-HO increases from 0% to 100%, the flow ratios in the two renal arteries change from significant different to be closed at systolic period. Peripheral VA-ECMO with various perfusion levels from cardiac output and ECMO has significant effect on aortic flow surrounding. Partial recovery of heart function can impel BMR moves from proximal to distal side of the heart, which may lead to inadequate supply of oxygenated blood to the upper limb and cephalic vessels.

Tools for Understanding and Predicting the Affinity of Per- and Polyfluoroalkyl Substances for Anion-Exchange Sorbents.

Anion-exchange (AE) sorbents are gaining in popularity for the remediation of anionic per- and polyfluoroalkyl substances (PFAS) in water. However, it is unclear how hydrophobic and electrostatic interactions contribute to anionic PFAS retention. The goal of this study was to understand the effects of PFAS chain length and head group on electrostatic interactions between PFAS and an aminopropyl AE phase. Liquid chromatography-mass spectrometry (LC-MS) was used with an aminopropyl AE guard column to find relative retention times. The average electrostatic potential (EPavg) of each PFAS was calculated, which correlated positively with the PFAS chromatographic retention time, demonstrating the value of EPavg as a proxy for predicting electrostatic interactions between PFAS and the aminopropyl AE phase. The order of greatest to lowest PFAS AE affinity for an aminopropyl column based on chromatographic retention times and electrostatic interactions was n:3 fluorotelomer carboxylic acids (n:3 FtAs) > n:2 fluorotelomer carboxylic acids (n:2 FtAs) > perfluoroalkyl carboxylates (PFCAs) > perfluoroalkyl sulfonamides (FASAs) ∼ n:2 fluorotelomer sulfonates (n:2 FtSs) > perfluoroalkyl sulfonates (PFSAs). This study introduces a methodology for qualitatively characterizing electrostatic interactions between PFAS and AE phases and highlights that electrostatic interactions alone cannot explain the affinity of PFAS for AE resins in water treatment/remediation scenarios.

Potential application of novel [formula omitted]-indices as molecular descriptors

A topological index or a descriptor is a graph invariant that describes the structure of a graph as a numerical value. This paper proposes eight novel indices called AL-indices, based on distance and degree, and analyzes their behavior to show that they can serve as potentially useful molecular descriptors. We find that among the proposed indices many have very good discriminative power when compared to the existing vertex-degree based indices and justifies the requirement of these new indices. Further, we propose a method to compute these indices and vertex-degree-based indices from a recently proposed graph matrix, referred to as neighborhood matrix.Computationally, we correlate the proposed indices’ efficiency against the octane isomers’ and polychlorobiphenyls’ physicochemical properties. We perform a comparative study of these indices with a few well-known vertex degree-based indices. Further, the proposed indices’ discriminative capacity is analyzed and shown to have higher discriminative power on the considered datasets. Among all the indices under study, four indices, namely AL4, AL5, AL7, and AL8 have shown the highest discriminative power on the set of octane isomers. While the indices AL4 and AL7 have the highest discriminative power on the set of PCB molecules compared to the other VDB indices.Among the proposed and considered indices, we show that the first index AL1 has a good correlation with the Acentric factor and entropy of octane isomer and with the total surface area, log-water-solubility, relative retention time, octanol–water-partition, and log-water-activity coefficient of PCBs.

Penentuan Terbinafine Hidroklorida dalam Kosmetik Sediaan Pemutih Secara Kromatografi Cair Kinerja Tingg

Terbinafine hydrochloride is a synthetic allylamine drug with a broad spectrum of antifungal properties. The purpose of this study was to identify terbinafine hydrochloride in whitening cosmetic products using High Performance Liquid Chromatography (HPLC). The first stage starts with dissolving cosmetic samples (A, B, C) and blanks, diluted with 25 ml of methanol. Then the solution was vortexed for 2 and centrifuged for 10 minutes at 4000 rpm. The supernatant layer formed was filtered through a 0.45 m membrane filter. Then the filtrate obtained was tested by the HPLC method. Based on the results of the system suitability test of the sample and blank, the concentration was 16𝜇𝑔/ml, the average retention time was 8.934 minutes and the average area was 2163340. The standard deviation of the relative retention time was 0.3098% and the area was 0.0721%. The follow-up factor and theoretical plate obtained automatically from the HPLC tool obtained an average follow-up factor value of 0.9515 and an average theoretical plate value of 217.7531. The results of the HPLC system suitability test and the terbinafine hydrochloride blank were identical, but the retention time was different, obtained from each different sample. All cosmetic samples contained Terbinafine hydrochloride as they did not meet the requirements. Regulation of the Minister of Health of the Republic of Indonesia Number 3 of 2021.

Machine Learning-Assisted Identification and Quantification of Hydroxylated Metabolites of Polychlorinated Biphenyls in Animal Samples.

Laboratory studies of the disposition and toxicity of hydroxylated polychlorinated biphenyl (OH-PCB) metabolites are challenging because authentic analytical standards for most unknown OH-PCBs are not available. To assist with the characterization of these OH-PCBs (as methylated derivatives), we developed machine learning-based models with multiple linear regression (MLR) or random forest regression (RFR) to predict the relative retention times (RRT) and MS/MS responses of methoxylated (MeO-)PCBs on a gas chromatograph-tandem mass spectrometry system. The final MLR model estimated the retention times of MeO-PCBs with a mean absolute error of 0.55 min (n = 121). The similarity coefficients cos θ between the predicted (by RFR model) and experimental MS/MS data of MeO-PCBs were >0.95 for 92% of observations (n = 96). The levels of MeO-PCBs quantified with the predicted MS/MS response factors approximated the experimental values within a 2-fold difference for 85% of observations and 3-fold differences for all observations (n = 89). Subsequently, these model predictions were used to assist with the identification of OH-PCB 95 or OH-PCB 28 metabolites in mouse feces or liver by suggesting candidate ranking information for identifying the metabolite isomers. Thus, predicted retention and MS/MS response data can assist in identifying unknown OH-PCBs.

QSRR model for identification and screening of emerging pollutants based on artificial intelligence algorithms

ABSTRACT It is urgent to identify and screen emerging pollutants (EPs), which have caused great harm to human health and the environment. In their detection of liquid chromatography-mass spectrometry (LC-MS), the quantitative structure–retention relationship (QSRR) model is simple and efficient to predict the retention behavior of compounds. In the present work, we collected more data with the relative retention time (RRT) of 490 compounds, and filtered the molecular descriptors with lasso regression and multiple linear regression analysis. Then ten important molecular descriptors were screened and applied the QSRR models with deep neural network (DNN), multiple linear regression (MLR), and support vector machine. The DNN model had the best accuracy which the correlation coefficient R2 reached 0.913. Finally, we determined the applicability of the DNN model through a descriptor value range to assist in the identification and screening of EPs.

Prediction of Intact N-Glycopeptide Retention Time Windows in Hydrophilic Interaction Liquid Chromatography.

Analysis of protein glycosylation is challenging due to micro- and macro-heterogeneity of the attached glycans. Hydrophilic interaction liquid chromatography (HILIC) is a mode of choice for separation of intact glycopeptides, which are inadequately resolved by reversed phase chromatography. In this work, we propose an easy-to-use model to predict retention time windows of glycopeptides in HILIC. We constructed this model based on the parameters derived from chromatographic separation of six differently glycosylated peptides obtained from tryptic digests of three plasma proteins: haptoglobin, hemopexin, and sex hormone-binding globulin. We calculated relative retention times of different glycoforms attached to the same peptide to the bi-antennary form and showed that the character of the peptide moiety did not significantly change the relative retention time differences between the glycoforms. To challenge the model, we assessed chromatographic behavior of fetuin glycopeptides experimentally, and their retention times all fell within the calculated retention time windows, which suggests that the retention time window prediction model in HILIC is sufficiently accurate. Relative retention time windows provide complementary information to mass spectrometric data, and we consider them useful for reliable determination of protein glycosylation in a site-specific manner.