Liquid Chromatography Approach Research Articles

Highly sensitive two-dimensional profiling of N-linked glycans by hydrophilic interaction liquid chromatography and dual stacking capillary gel electrophoresis

BackgroundN-Glycosylation is one of the most important post-translational modifications in proteins. As the N-glycan profiles in biological samples are diverse and change according to the pathological condition, various profiling methods have been developed, such as liquid chromatography (LC), capillary electrophoresis (CE), and mass spectrometry. However, conventional analytical methods have limitations in sensitivity and/or resolution, hindering the discovery of minor but specific N-glycans that are important both in the basic glycobiology research and in the medical application as biomarkers. Therefore, a highly sensitive and high-resolution N-glycan profiling method is required. ResultsIn this study, we developed a novel two-dimensional (2D) separation system, which couples hydrophilic interaction liquid chromatography (HILIC) with capillary gel electrophoresis (CGE) via large-volume dual preconcentration by isotachophoresis and stacking (LDIS). Owing to the efficient preconcentration efficiency of LDIS, limit of detection reached 12 pM (60 amol, S/N = 3) with good calibration curve linearity (R2 > 0.999) in the 2D analysis of maltoheptaose. Finally, 2D profiling of N-glycans obtained from standard glycoproteins and cell lysates were demonstrated. High-resolution 2D profiles were successfully obtained by data alignment using triple internal standards. N-glycans were well distributed on the HILIC/CGE 2D plane based on the glycan size, number of sialic acids, linkage type, and so on. As a result, specific minor glycans were successfully identified in HepG2 and HeLa cell lysates. Significance and noveltyIn conclusion, the HILIC/CGE 2D analysis method showed sufficient sensitivity and resolution for identifying minor but specific N-glycans from complicated cellular samples, indicating the potential as a next-generation N-glycomics tool. Our novel approach for coupling LC and CE can also dramatically improve the sensitivity in other separation modes, which can be a new standard of 2D bioanalysis applicable not only to glycans, but also to other diverse biomolecules such as metabolites, proteins, and nucleic acids.

Comparative Evaluation of Secondary Metabolite Chemodiversity of Citrus Genebank Collection in Greece: Can the Peel be More than Waste?

Citrus fruits are among the most economically important crops in the world. In the global market, the Citrus peel is often considered a byproduct but substitutes an important phenotypic characteristic of the fruit and a valuable source of essential oils, flavonoids, carotenoids, and phenolic acids with variable concentrations. The Mediterranean basin is a particularly dense area of autochthonous genotypes of Citrus that are known for being a source of healthy foods, which can be repertoires of valuable genes for molecular breeding with the focus on plant resistance and quality improvement. The scope of this study was to characterize and compare the main phenotypic parameters (i.e., peel thickness, fruit volume, and area) and levels of bioactive compounds in the peel of fruits from the local germplasm of Citrus in Greece, to assess their chemodiversity regarding their polyphenolic, volatile, and carotenoid profiles. A targeted liquid chromatographic approach revealed hesperidin, tangeretin, narirutin, eriocitrin, and quercetin glycosides as the major polyphenolic compounds identified in orange, lemon, and mandarin peels. The content of tangeretin and narirutin followed the tendency mandarin > orange > lemon. Eriocitrin was a predominant metabolite of lemon peel, following its identification in lower amounts in mandarin and at least in the orange peel. For these citrus-specific metabolites, high intra- but also interspecies chemodiversity was monitored. Significant diversity was found in the essential oil content, which varied between 1.2 and 3% in orange, 0.2 and 1.4% in mandarin, and 0.9 and 1.9% in lemon peel. Limonene was the predominant compound in all Citrus species peel essential oils, ranging between 88 and 93% among the orange, 64 and 93% in mandarin, and 55 and 63% in lemon cultivars. Carotenoid analysis revealed different compositions among the Citrus species and accessions studied, with β-cryptoxanthin being the most predominant metabolite. This large-scale metabolic investigation will enhance the knowledge of Citrus peel secondary metabolite chemodiversity supported by the ample availability of Citrus genetic resources to further expand their exploitation in future breeding programs and potential applications in the global functional food and pharmaceutical industries.

A Combined Gas and Liquid Chromatographic Approach for Quality Evaluation of Saffron-Based Food Supplements.

Considering the interest in the bioactive properties of saffron (Crocus sativus L.), as well as its limited production and high price, saffron-based food supplements (SFS) are highly susceptible to adulteration. However, their complex composition and the wide variety of potential fraudulent practices make the comprehensive assessment of SFS quality a challenging task that has been scarcely addressed. To that aim, a new multianalytical strategy based on gas chromatography coupled to mass spectrometry (GC-MS) and liquid chromatography with diode array detection coupled to mass spectrometry (HPLC-DAD-MS) was developed and validated in order to detect different frauds affecting SFS. Dried saffron stigmas and a commercial standardized saffron extract (affron®) were selected as reference samples (RS) to obtain an authenticity profile, which was further used to evaluate the quality of 17 SFS. Up to 17 crocins and crocetins, 5 kaempferol glycosides, picrocrocin (determined for the first time by GC-MS), safranal, furanone and isophorone-related compounds were determined in RS. Safranal and crocins were identified in all SFS except for one sample. However, discrepancies with the content declared were detected in 65% of the cases. Moreover, this multianalytical methodology also allowed identifying undeclared additives and the non-declared addition of vegetable sources other than saffron.

N-Acetylcysteine Displaces Glutathionyl-Moieties from Hg2+ and MeHg+ to Form More Hydrophobic Complexes at Near-Physiological Conditions.

The anthropogenic release of Hg is associated with an increased human exposure risk. Since Hg2+ and MeHg+ have a high affinity for thiols, their interaction with L-glutathione (GSH) within mammalian cells is fundamentally involved in their toxicological chemistry and excretion. To gain insight into the interaction of these mercurials with multiple small molecular weight thiols, we have investigated their competitive interactions with GSH and N-acetylcysteine (NAC) at near-physiological conditions, using a liquid chromatographic approach. This approach involved the injection of each mercurial onto a reversed-phase (RP)-HPLC column (37 °C) using a PBS buffer mobile phase containing 5.0 mM GSH to simulate cytosolic conditions with Hg being detected in the column effluent by an inductively coupled plasma atomic emission spectrometer (ICP-AES). When the 5.0 mM GSH mobile phase was amended with up to 10 mM NAC, gradually increasing retention times of both mercurials were observed. To explain this behavior, the experiment with 5.0 mM NAC and 5.0 mM GSH was replicated using 50 mM Tris buffer (pH 7.4), and the Hg-containing fractions were analyzed by electrospray ionization mass spectrometry. The results revealed the presence of Hg(GS)(NAC) and Hg(NAC)2 for Hg2+ and MeHg(GS) and MeHg(NAC) for MeHg+, which suggests that the coordination/displacement of GS-moieties from each mercurial by the more hydrophobic NAC can explain their retention behavior. Since the biotransformations of both mercurials were observed at near-physiological conditions, they are of toxicological relevance as they provide a biomolecular explanation for some results that were obtained when animals were administered with each mercurial and NAC.

Development and Validation of Stability indicating HPLC method for determination of related substances and assay of Monobenzone drug substance

Monobenzone, a mono benzyl ether of hydroquinone, is used as a topical drug for skin depigmentation. It increases the excretion of melanin from melanocytes. A novel stability-indicating high performance liquid chromatographic approach has been established in the current study to identify related compounds and assay of Monobenzone. The Agilent 1260 system was used for the HPLC analysis, and a gradient method using 0.1% orthophosphoric acid in water and acetonitrile as the eluent was used to separate Monobenzone from known contaminants and degradation products on a Zorbax SB-phenyl (250 mm x 4.6 mm) 5 μm column. The flow rate was set at 0.8 mL/min, the column oven temperature was 30 °C, and the detector wavelength was maintained at 215 nm. The relative retention times for Hydroquinone and Monobenzone dimer were around 0.35 and 1.86 respectively, while the Monobenzone retention time was approximately 10.4 min. The total run time was 30 min. For all known analytes spanning the concentration range from LOQ to 200% of the specification level, the calibration plot revealed a linear relationship (minimum r=0.999). All known analytes' LOD and LOQ were found to be within 0.06–0.10 μg/mL and 0.15–0.24 μg/mL, respectively. A recovery study determined the accuracy of the proposed method. For Hydroquinone and Monobenzone dimer, mean recovery was found to be in the range of 95.86%–99.89% and 93.02%–99.84% respectively. The repeatability study showed that the method is precise enough within acceptable limits. Studies on solution stability and robustness produced results that fell within acceptable bounds. The proposed method shows excellent linearity, accuracy, precision, specificity, robustness, LOD, LOQ and system suitability findings. Additionally, the forced degradation study showed that the approach was stability indicating in nature.

Utility of Quality by Design approach in RP-HPLC method development for quantification of lamivudine and effavirenz in combination formulation

Objective: For the measurement of lamivudine(LAM) and effavirenz (EVZ) in combination formulation, a uncomplicated and reliable liquid chromatographic approach has been proposed.
 Material and Method: Multivariate optimization of the RP-HPLC method, experimental conditions were accomplished using the design of experiments (DoE). The crucial method parameters were determined by a risk assessment. The mathematical models were created using three independent variables: percentage of acetonitrile, percentage of methanol, and buffer pH. The impacts of these independent elements were thoroughly investigated using the central composite design (CCD), which was utilized to analyze the response surface methodology. 
 Result and Discussion: The LAM and EVZ retention time and resolution were both concurrently optimized using the desirability function. Acetonitrile, methanol, and phosphate buffer (pH 7.0) in the proportions of 40:20:40 v/v each were used in the optimized and anticipated data from the contour diagram, with detection occurring at a wavelength of 215 nm. Baseline separation of both pharmaceuticals with high resolution and a run time of under 6 minutes was accomplished under these ideal conditions. The validated test parameters followed ICH recommendations. As a consequence, the findings demonstrated that the Quality by Design methodology could be successfully used to optimize the RP-HPLC technique for the concurrent quantification of LAM and EVZ.

Liquid Chromatographic Approach for Analysis of Favipiravir–A Repurpose Drug for COVID-19

Favipiravir is a potential repurpose moiety to treat COVID-19 by depletion of virus load in infectious patients. To analyze and separate Favipiravir with remarkable effi ciency, X-Bridge C8 column (150 x 4.6 mm, 5 μ) and a solvent phase of 0.1% TEA and acetonitrile (40:60 v/v) with 1-mL/min fl ow rate were used. The eluted favipiravir and possible degradants were detected at 225 nm. Further, the process was validated by using ICH (Q2R1) guidelines to ensure the method’s suitability in the pharmaceutical sector. The RT of Favipiravir was observed at 3.7 min with good linearity of 2 to 30 μg/mL. %RSD of both system and method precision was assessed in the series of 0.32 to 0.98. The mean percentage recovery of Favipiravir was in the range of 99.0–100.4%. The limit of detection (LoD) and limit of quantifi cation (LoQ) were assessed to be 0.024 and 0.084 μg/mL for favipiravir. The outcomes confi rmed that the projected approach was economical, insightful, simple and precise with better sensitivity. Investigation of Favipiravir in the incidence of a variety of stressed or forced degradation environments ensures stability indicating quality of the developed approach

Greener Stability-Indicating HPLC Approach for the Determination of Curcumin in In-House Developed Nanoemulsion and Curcuma longa L. Extract

Despite the fact that several analytical methodologies have been reported for the determination of curcumin (CCM) in a wide range of sample matrices, the greener liquid chromatographic approaches to determine CCM are scarce in the literature. Therefore, this research is designed to develop and validate a greener stability-indicating “high-performance liquid chromatography (HPLC)” methodology to determine CCM in an in-house developed nanoemulsion, Curcuma longa L. extract, and commercial tablets. CCM was measured on a Nucleodur (150 mm × 4.6 mm) RP C18 column with 5 µm-sized particles. Ethanol and ethyl acetate (83:17 v/v) made up the greener eluent system, which was pumped at a flow speed of 1.0 mL/min. At a wavelength of 425 nm, CCM was detected. The greener HPLC methodology was linear in the 1–100 µg/mL range, with a determination coefficient of 0.9983. The greener HPLC methodology for CCM estimation was also rapid (Rt = 3.57 min), accurate (%recoveries = 98.90–101.85), precise (%CV = 0.90–1.11), and sensitive (LOD = 0.39 µg/mL and LOQ = 1.17 µg/mL). The AGREE approach predicted the AGREE score of 0.81 for the established HPLC technique, indicating an outstanding greenness profile. The utility of the greener HPLC methodology was demonstrated by determining CCM in the in-house developed nanoemulsion, Curcuma longa extract, and commercial tablets. The % amount of CCM in the in-house developed nanoemulsion, Curcuma longa extract, and commercial tablets was found to be 101.24%, 81.15%, and 78.41%, respectively. The greener HPLC methodology was able to detect its degradation product under various stress conditions, suggesting its stability-indication characteristics. These results suggested that CCM in developed nanoemulsion, plant extract samples, and commercial tablets may be routinely determined using the greener HPLC methodology.

Comparison between one and two-dimensional liquid chromatographic approaches for the determination of plasmatic stroke biomarkers by isotope dilution and tandem mass spectrometry.

This work presents the evaluation of one- and two-dimensional liquid chromatography for the quantification of three stroke outcome predictors in plasma. Isotopically labelled analogues of L-arginine (L-Arg), asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are used to quantify the three analytes by isotope dilution and tandem mass spectrometry. Chromatographic isotope effects were not observed between natural L-Arg and its 15N-labelled analogue but they were observed between natural ADMA and SDMA and their multiple deuterated analogues. Under these conditions, bidimensional chromatography through the use of an automated multiple heart cutting mode provided unsatisfactory results for ADMA and SDMA due to the different amounts of natural and labelled compounds transferred from the first to the second chromatographic dimension. In contrast, using one dimensional liquid chromatography after a derivatization step to esterify carboxylic groups, chromatographic isotope effects did not alter the initial mass balance as full coelution of natural and labelled analogues or baseline resolution between the analytes was not required. This method was successfully validated following the Clinical & Laboratory Standards Institute guidelines and applied to the analysis of plasma samples from patients who had suffered from an intraparenchymal haemorrhagic stroke.

An Integrated HPLC Assay Technique for the Detection of Omeprazole in Mixed Dose Forms with Aspirin, Diclofenac or Domperidone

Omeprazole (OMP), which is given for treatment in conjunction with a number of medications, is drawing increased attention for its capacity to reduce gastric acid formation. Commonly administered OMP-loaded dose forms include aspirin (ASN), diclofenac (DCF) and domperidone (DMP). As a result, a single liquid chromatographic approach, which can simultaneously determine OMP-ASN, OMP-DCF or OMP-DMP in commercial formulations was developed. On a reverse-phase Agilent Eclipse XBD C18 analytical column (4.6 × 150 mm; 3.5 (m), the requisite separation was accomplished utilizing a gradient flow of the mobile phase made up of a mixture of solvents A and B (50:50 v/v) and diode array detection at 272 nm. Where solvent A is acetonitrile:buffer-A:buffer-B (10:90:50 v/v/v) and solvent B is acetonitrile:buffer-A:buffer-B (90:10:50 v/v/v). The buffer-B is made up of an equal mixture of 100 mM acetic acid and 100 mM triethyl-amine with a final attained pH of 5.2, whereas the buffer-A is made up of 10 mM trifluoroacetic acid (pH adjusted to 2.2). According to ICH Q2(R1) criteria, the method had been validated and verified the senstivity of the proposed method with a linearity range of 0.5-20 mcg/mL for all the analytes. The established technique for concurrently quantifying OMP with DCF, ASN or DMP in commercial formulations can be regularly employed in the quality control laboratory in accordance with the validation conditions.

New Potentiometric Screen-Printed Platforms Modified with Reduced Graphene Oxide and Based on Man-Made Imprinted Receptors for Caffeine Assessment.

Caffeine is a psychoactive drug that is administered as a class II psychotropic substance. It is also considered a component of analgesics and cold medicines. Excessive intake of caffeine may lead to severe health damage or drug addiction problems. The assessment of normal caffeine consumption from abusive use is not conclusive, and the cut-off value for biological samples has not been established. Herein, new cost-effective and robust all-solid-state platforms based on potentiometric transduction were fabricated and successfully utilized for caffeine assessment. The platforms were modified with reduced graphene oxide (rGO). Tailored caffeine-imprinted polymeric beads (MIPs) based on methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were prepared, characterized, and used as recognition receptors in the presented potentiometric sensing devices. In 50 mM MES buffer, the sensors exhibited a slope response of 51.2 ± 0.9 mV/decade (n = 6, R2 = 0.997) over the linear range of 4.5 × 10−6–1.0 × 10−3 M with a detection limit of 3.0 × 10−6 M. They exhibited fast detection of caffeinium ions with less than 5 s response time (<5 s). The behavior of the presented sensors towards caffeinium ions over many common organic and inorganic cations was evaluated using the modified separate solution method (MSSM). Inter-day and intra-day precision for the presented analytical device was also evaluated. Successful applications of the presented caffeine sensors for caffeine determination in commercial tea and coffee and different pharmaceutical formulations were carried out. The data obtained were compared with those obtained by the standard liquid chromatographic approach. The presented analytical device can be considered an attractive tool for caffeine determination because of its affordability and vast availability, particularly when combined with potentiometric detection.

Etravirine Lipid Nanoparticles: Development and Validation Using Specific RP-HPLC Technique

Introduction: A common, exact &amp; economical reverse phase-high performance liquid chromatographic approach for coinciding measurement of anti-retroviral medicine, Etravirine in the formulation of nanoparticle has been devised. This approach is a revolutionary analytical methodology for detecting substance at the same time.&#x0D; Methods: Validation &amp; optimization chromatographic conditions were completed as per the guidelines of ICH. The disconnection was done on a column measuring (150mm x 4.6mm, 5μ) using the mobile phase consisted of acetonitrile and 10mM ammonium acetate buffer in the ratio of 90:10 v/v of pH 2.7 as the mobile phase in the ratio 85:15 at a flow rate of 1ml/min for a short run time of 13 minutes. The wavelength was 310nm &amp; the column temperature was kept at 26°C.&#x0D; Results: The devised technique was linear at 10, 20, 30, 40, as well as 50 g/ml, with a regression coefficient of 0.999 for each of these concentrations. For etravirine, the LOD readings were 0.514 g/ml, whereas the LOQ readings were 1.713 g/ml. Etravirine was shown to have a recovery rate of 98.8%.&#x0D; Conclusion: The approach was, precise, accurate &amp; rapid with excellent inter- &amp; intra-day accuracy. The approach was also useful for characterization &amp; coinciding measurement of medicines in formulation of nanoparticles.

Sustainable liquid chromatographic determination and purity assessment of a possible add-on triple-action over-the-counter pharmaceutical combination in COVID-19

Nowadays, all researchers are focused on combating the pandemic COVID-19. According to recent statistics, most patients are managed at home. An over-the-counter (OTC) triple action formula containing paracetamol (PAR), aspirin (ASP), and diphenhydramine (DIPH) is widely prescribed for pain, fever and as night-time sleep aid. For COVID-19 patients, this combination is now suggested as part of symptomatic therapy and prophylaxis. In this work, two simple liquid chromatographic approaches were designed for simultaneous determination of PAR, ASP, and DIPH in Excedrin® PM caplets, beside three specified official toxic impurities, namely, p-aminophenol, p-nitrophenol, and salicylic acid. The first method comprised high-performance thin-layer chromatographic separation coupled with densitometric quantification, on silica gel HPTLC 60 F254 aluminium sheets as the stationary phase, ethyl acetate–methanol-aqueous ammonium hydroxide (10.0: 2.0: 0.1, by volume) as the developing system and scanning was performed at 210.0 nm. The second one is a high-performance liquid chromatography coupled with diode array detector. Successful separation of the six components was performed on XTerra C18 column with isocratic elution of mobile phase 0.1% triethylamine acidified water: methanol (70:30, v/v) adjusted with o-phosphoric acid to pH 3.0 and methanol (90:10, v/v) with flow rate programming and detection at 210.0 nm. Validation of the proposed methods was performed according to ICH guidelines. Both methods were successfully used for quality control of the cited drugs in their marketed formulation. Moreover, the in-vitro release study was monitored using the proposed HPLC-DAD method. The greenness profile of the proposed methods was assessed and comparatively evaluated through various assessment tools, specifically; the analytical eco-scale system, national environmental method index (NEMI), green analytical procedure index (GAPI) and analytical greenness (AGREE) metric.

On-Chip Liquid Chromatography

On-chip liquid chromatography (LC) refers to LC technology that is miniaturized to fit on a microchip to enable fast, high-throughput analysis, with small sample volumes and low reagent consumption. Four different on-chip LC approaches have been developed to date: use of open-tubular, packed-particle, monolithic, and pillar array columns. These methods have been applied to proteomics as well as the analysis of small molecules and drugs in various biological samples. Recent advances in on-chip LC are summarized herein.

Embossed Paper Platform for Whole Blood Collection, Room Temperature Storage, and Direct Analysis by Pinhole Paper Spray Mass Spectrometry.

Dry-state microsampling techniques are convenient and advantageous for sample collection in resource-limited settings, including healthcare systems designed for the underserved population. In this work, a microsampling platform based on an embossed hydrophobic paper substrate is introduced together with three-dimensional (3D) printed cartridges that offer opportunities for rapid (<30 min) drying of the collected samples while also preserving sample integrity when the embossed paper chip is shipped at room temperature. More importantly, a new pinhole paper spray ionization method was developed that facilitates direct mass spectrometry (MS) analysis of the dried blood samples without prior sample preparation. We compared the direct pinhole paper spray MS method with a liquid chromatographic (LC) MS approach that relied upon electrospray ionization (ESI) after analytes present in the blood sample were extracted through liquid-liquid extraction. Limits of detection as low as 0.12 and 0.49 ng/mL were calculated for cocaine and its metabolite benzoylecgonine, respectively, when using the direct pinhole paper spray MS method. Analytical merits such as precision and accuracy, recovery, carryover effects, and analyte stability were all quantified for this new paper spray method and compared to the traditional LC-ESI-MS. Although LC-ESI-MS was observed to be 10× more sensitive, the linear dynamic range for both methods was determined to be the same, in the range of 1-500 ng/mL for both cocaine and benzoylecgonine analytes. When fully developed, the current microsampling strategy could offer an easy-to-use kit that can enable a more effective MS analysis of 20 μL dried blood samples delivered by mail. Both sensitivity (10×) and sample stability are found to be more superior for blood prepared in the embossed hydrophobic paper compared to samples prepared in the planar hydrophilic paper.

Impact of pesticide formulation excipients and employed analytical approach on relative matrix effects of pesticide determination in strawberries

Relative matrix effects between an ambient mass spectrometric technique known as coated blade spray (CBS) and liquid chromatographic separation approach when applied to multiresidue pesticide analysis in strawberry samples are explored. Acceptable slope relative standard deviations (RSD <15 %) were observed for the 9 compounds under study for both CBS-MS/MS (2.2–12.6 %) and LC-MS/MS (2.8–12.9 %) approaches. The findings signify both the elimination of relative matrix effects with the sample preparation and matrix match calibration with internal standard correction methods employed along with no matrix effect compromise made when using the direct-to-MS approach. Similarly, slopes of pesticides spiked from commercially available formulations (containing one or two pesticides) were found to not differ significantly from slopes generated with multiresidue pesticide standards (containing 24 additional pesticides besides the target 9 analytes) with either technique, highlighting the resistance of the employed methods to the excipients present in pesticide formulations in large amounts.

Chemometric Assisted Development and Validation of a Stability-indicating LC Method for Determination of Related Substances in Haloperidol Decanoate Injection

Abstract: Aim: Haloperidol decanoate injection is a phenyl butyl piperadine derivative with antipsychotic, neuroleptic, antiemetic effects and has multiple related substances as process and degradant impurities. Objectives: This study focuses on chemometric assisted liquid chromatographic approach to develop a stability indicating impurity profile of Haloperidol decanoate injection. Methodology: Dual experimental designs (combined mixture I-optimal design and response surface historical data design) were employed to resolve all thirteen known impurities of Haloperidol decanoate. Chromatographic separation was achieved on a Hypersil BDS C18 (100 x 4.0 mm) 3-μm column to attain separation of related compounds. Results: The optimum conditions for the chromatographic system resulted in a mobile phase consisting of tetra butyl ammonium hydrogen sulphate/ 1-decane Sulphonate sodium buffer solution and acetonitrile with linear gradient elution at a flow rate of 1.4 mL/min. Selectivity, forced degradation, linearity, accuracy and precision were demonstrated in a range of 0.75-30.0 μg/mL. Conclusion: The optimized method was able to resolve the ghost peak observed because of gradient change of mobile phase and is able to separate both polar and non-polar impurities within 60 min, in single method, with resolution of more than 2.0 between adjacent impurities. The inter-day precision for all impurities and haloperidol decanoate were evaluated and found to have a % RSD of less than 10. Key words: Design of Experiments, Haloperidol decanoate Injection, Stability indicating method, DoE aided chromatographic method development, Artifact optimization.

Development and Application of Liquid Chromatographic Retention Time Indices in HRMS-Based Suspect and Nontarget Screening.

There is an increasing need for comparable and harmonized retention times (tR) in liquid chromatography (LC) among different laboratories, to provide supplementary evidence for the identity of compounds in high-resolution mass spectrometry (HRMS)-based suspect and nontarget screening investigations. In this study, a rigorously tested, flexible, and less system-dependent unified retention time index (RTI) approach for LC is presented, based on the calibration of the elution pattern. Two sets of 18 calibrants were selected for each of ESI+ and ESI-based on the maximum overlap with the retention times and chemical similarity indices from a total set of 2123 compounds. The resulting calibration set, with RTI set to range between 1 and 1000, was proposed as the most appropriate RTI system after rigorous evaluation, coordinated by the NORMAN network. The validation of the proposed RTI system was done externally on different instrumentation and LC conditions. The RTI can also be used to check the reproducibility and quality of LC conditions. Two quantitative structure-retention relationship (QSRR)-based models were built based on the developed RTI systems, which assist in the removal of false-positive annotations. The applicability domains of the QSRR models allowed completing the identification process with higher confidence for substances within the domain, while indicating those substances for which results should be treated with caution. The proposed RTI system was used to improve confidence in suspect and nontarget screening and increase the comparability between laboratories as demonstrated for two examples. All RTI-related calculations can be performed online at http://rti.chem.uoa.gr/.

All-Solid-State Potentiometric Ion-Sensors Based on Tailored Imprinted Polymers for Pholcodine Determination.

In recent times, the application of the use of ion-selective electrodes has expanded in the field of pharmaceutical analyses due to their distinction from other sensors in their high selectivity and low cost of measurement, in addition to their high measurement sensitivity. Cost-effective, reliable, and robust all-solid-state potentiometric selective electrodes were designed, characterized, and successfully used for pholcodine determination. The design of the sensor device was based on the use of a screen-printed electrode modified with multiwalled carbon nanotubes (MWCNTs) as a solid-contact transducer. Tailored pholcodine (PHO) molecularly imprinted polymers (MIPs) were prepared, characterized, and used as sensory receptors in the presented potentiometric sensing devices. The sensors exhibited a sensitivity of 31.6 ± 0.5 mV/decade (n = 5, R2 = 0.9980) over the linear range of 5.5 × 10−6 M with a detection limit of 2.5 × 10−7 M. Real serum samples in addition to pharmaceutical formulations containing PHO were analyzed, and the results were compared with those obtained by the conventional standard liquid chromatographic approach. The presented analytical device showed an outstanding efficiency for fast, direct, and low-cost assessment of pholcodine levels in different matrices.

Application of Chiral and Achiral Supercritical Fluid Chromatography in Pesticide Analysis: A Review

Supercritical fluid chromatography (SFC), the most common mode of which employs pressurized carbon dioxide as the mobile phase, is enjoying resuscitation. It is once again reconsidered as a fast developing chromatographic technique for the separation and identification of compounds in mixtures. In recent years, significant improvements in instrumentation, and its proficiency in specialized applications, have rekindled interest in the technique. SFC applicability in various fields, such as pharmaceutical analysis, bioanalysis, forensic science, environmental analysis, food science, has continued to expand. The present article delineates a comprehensive up-to-date overview of the applications of SFC in pesticide analysis, including the monitoring of their residues in different matrices and the investigation of their environmental behaviors such as dissipation and bioaccumulation. Since ~30% of currently registered pesticides are chiral compounds, attention is also paid to the analysis of such pesticides due to their enantioselective biological activities. Thus, both achiral and chiral SFC in pesticide analysis is reviewed. The article covers discussions on chromatographic conditions, method validation, and sample preparation as well as comparisons with gas chromatographic and liquid chromatographic approaches.