Peak Resolution Research Articles

Beyond helium: hydrogen as a carrier gas in multiresidue pesticide analysis in fruits and vegetables by GC-MS/MS.

In this comprehensive study, we evaluated the feasibility of using hydrogen instead of helium as a carrier gas in a GC-MS/MS system for pesticide residue analysis, spanning three matrices: pepper, tomato, and zucchini. Initial assessments focused on the ion source's chemical inertness, employing nitrobenzene as a benchmark to monitor the hydrogenation process. A method with a duration of less than 12 minutes was developed, achieving good chromatographic peak resolution attributable to the enhanced chromatographic performance of hydrogen as a carrier gas. The study emphasized the optimization of system parameters, testing various ion source temperatures, detector voltages, and injection volumes. Sensitivity assessments, based on the DG-SANTE criteria, indicated that the majority of compounds were identifiable at a concentration of 5 μg kg-1 (81% in tomato, 84% in pepper and 73% in zucchini). Detailed validation for reproducibility, matrix effects, and linearity across 150 pesticides unveiled generally favorable outcomes, with a notable majority of compounds displaying low matrix effects, satisfactory linearity ranges and good reproducibility with most compounds returning a relative standard deviation (RSD) below 10%. When applied to 15 real samples, the hydrogen-based system's performance was juxtaposed against a helium-based counterpart, revealing that results are very comparable between both systems. This comparative approach highlights hydrogen's potential as a reliable and efficient carrier gas in pesticide residue analysis for routine food control laboratories, overcoming difficulties resulting from the lack of helium supplies.

Validation of an HPLC-DAD Method for Quercetin Quantification in Nanoparticles.

The evaluation of the efficacy of incorporation of quercetin in nanoparticles is crucial, both for the development and quality control of pharmaceutical formulations. The validation of analytical methods for the precise quantification of quercetin is useful for the evaluation of various potential quercetin delivery systems and quercetin pharmacokinetics. This work aimed to validate a high-performance liquid chromatography with diode array detection (HPLC-DAD) method for quercetin detection and quantification in nanoparticles. Different mobile phase conditions and detection wavelengths (254 and 368 nm) were tested, and the major validation parameters were assessed (precision, accuracy, linearity, sensitivity, stability, and selectivity). The best peak resolution was obtained when quercetin was analyzed at 368 nm with a mobile phase of 1.5% acetic acid and a water/acetonitrile/methanol ratio of 55:40:5. Under these conditions, quercetin also eluted rapidly (retention time of 3.6 min). The method proved to be linear (R2 > 0.995), specific, and repeatable (variation coefficient between 2.4% and 6.7%) and presented intermediate precision (variation coefficient between 7.2% and 9.4%). The accuracy of the analysis ranged between 88.6% and 110.7%, and detection and quantification limits were 0.046 and 0.14 µg/mL, respectively. Quercetin solutions were more stable when stored at 4 °C than at room temperature or -20 °C. This validated method satisfied more parameters of bias assessment than most recent methods for quercetin determination and presented itself as more sensitive and efficient than general spectrophotometric methods. The method was successfully used for the analysis of quercetin incorporation in nanoparticles and will be evaluated in the future for its adequacy for the determination of quercetin in more complex matrices.

Analysis of DNA Origami Nanostructures Using Capillary Electrophoresis.

DNA origami nanostructures are engineered nanomaterials (ENMs) that possess significant customizability, biocompatibility, and tunable structural and functional properties, making them potentially useful materials in fields, such as medicine, biocomputing, biomedical engineering, and measurement science. Despite the potential of DNA origami as a functional nanomaterial, a major barrier to its applicability is the difficulty associated with obtaining pure, well-folded structures. Therefore, rapid methods of analysis to ensure purity are needed to support the rapid development of this class of nanomaterials. Here, we present the development of capillary electrophoresis (CE) as an analytical tool for DNA origami. CE was investigated under both capillary zone electrophoresis (CZE) and capillary transient isotachophoresis (ctITP) modes. Optimization of both systems yielded baseline resolved separations of folded DNA origami nanostructures from excess staple strands. The ctITP separation mode demonstrated superior performance in terms of peak resolution (Rs = 2.05 ± 0.3), peak efficiency (N = 12,200 ± 230), and peak symmetry (As = 1.29 ± 0.032). The SYBR family dyes (Gold, Green I, and Green II) were investigated as highly efficient, noncovalent fluorophores for on-column labeling of DNA origami and detection using laser-induced fluorescence. Finally, ctITP analysis conditions were also applied to DNA origami nanostructures with different shapes and for the differentiation of DNA origami aggregates.

Characterization of CO Adsorbed to Clean and Partially Oxidized Cu(211) and Cu(111).

Copper-based catalysts gain activity through the presence of poorly coordinated Cu atoms and incomplete oxidation at the surface. The catalytic mechanisms can in principle be observed by controlled dosing of reactants to single-crystal substrates. However, the interconnected influences of surface defects, partial oxidation, and adsorbate coverage present a large matrix of conditions that have not been fully explored in the literature. We recently characterized oxygen and carbon monoxide coadsorption on Cu(111), a nominally defect-free surface, and now extend our study to the stepped surface Cu(211). Temperature-programmed desorption of CO adsorbed to bare metal surfaces confirms that two sites dominate desorption from a saturated layer: atop terrace atoms of local (111) character and atop step edge atoms with CO bound more strongly to the latter. At low coverage, discrete CO resonances in reflection adsorption infrared spectra can be assigned to these sites: 2077 cm-1 for extended (111) terraces, 2093 cm-1 for step sites, and additional kink-adsorbed molecules at 2110 cm-1. With increasing coverage, in contrast to Cu(111), the infrared spectral features on Cu(211) evolve and shift as a consequence of dipole-dipole coupling between differentially occupied types of sites. Auger electron spectroscopy shows that exposure to background O2 oxidizes the (211) surface at a rate nearly 1 order of magnitude greater than (111); we argue that the resulting surface is stoichiometric Cu2O, as previously found for Cu(111). This oxide binds CO less strongly than the bare metal and the underlying crystal cut continues to influence the adsorption sites available to CO. On oxidized (111) terraces, broad absorption peaks at 2115-2120 cm-1; on oxidized Cu(211), CO adsorbed to step sites appears as a resolved secondary peak at 2144 cm-1. This suite of spectroscopic signatures, obtained under carefully controlled conditions, will help to determine the origin and fate of adsorbed species in future studies of reaction mechanisms on copper.

QbD-driven RP-HPLC method for novel chemo-herbal combination, in-silico, force degradation studies, and characterization of dual drug-loaded polymeric and lipidic nanocarriers

BackgroundIn cancer therapies, chemo-herbal combinations are receiving increased attention. A multiple tyrosine kinase inhibitor, lenvatinib (LTB) is beneficial in treating thyroid, lung, endometrial, and liver cancers. An isoflavone called biochanin A (BCA) is well known for its diverse biological properties that have been studied to potentiate the anti-cancer potential and lower the normal cell toxicities of other therapeutics. LTB and BCA can be combined for cancer treatment and may increase their therapeutic potential at lower doses. In brief, the quality by design (QbD)-driven RP-HPLC method was developed, validated, and utilized for applications employing the study of forced degradants and the successful development of LTB and BCA co-loaded nanocarriers.ResultsThe RP-HPLC method employed Box–Behnken design with peak resolution 6.70 ± 0.006, tailing factor 1.06 ± 0.05 for BCA and 1.17 ± 0.021 for LTB, and theoretical plates number > 2000. RP-HPLC applications utilized the investigation of a total of 41.17% and 70.58% degradants for LTB and BCA in contrast to in-silico predicted studies using Zeneth software. The poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) were formed with particle size 185.3 ± 12.3 nm, zeta potential − 13.3 ± 0.35 mV, and percentage entrapment efficiency (%EE) for the LTB and BCA 53.64 ± 4.81% and 61.29 ± 4.67%, respectively. However, the developed Cubosomes (CBs) exhibited 182.4 ± 16.3 nm aerodynamic particle size, − 10.8 ± 0.39 mV zeta potential, and % EE for LTB and BCA 55.62 ± 7.73% and 72.88 ± 5.52%, respectively. The percentage drug loading (%DL) of LTB and BCA from PLGA NPs was found to be 3.7 ± 0.46% and 4.63 ± 0.48%, whereas CBs exhibited higher % DL for BCA (5.42 ± 1.10%) and LTB (4.43 ± 0.77%).ConclusionThe RP-HPLC method was developed and validated according to ICH and USP guidelines. In-vitro and in-silico forced degradation studies are evident to quantify the type of degradant and its exact mechanism of degradation. In-silico toxicity assessment for LTB, BCA, and their degradants explains the necessity of conducting degradation studies during drug development. Finally, the applications of the developed RP-HPLC method explain the usefulness of analytical methods in the development of chemo-herbal drug nanocarriers (polymeric and lipidic).Graphical abstract

A global LC-MS2 -based methodology to identify and quantify anionic phospholipids in plant samples.

Anionic phospholipids (PS, PA, PI, PIPs) are low-abundant phospholipids with impactful functions in cell signaling, membrane trafficking and cell differentiation processes. They can be quickly metabolized and can transiently accumulate at defined spots within the cell or an organ to respond to physiological or environmental stimuli. As even a small change in their composition profile will produce a significant effect on biological processes, it is crucial to develop a sensitive and optimized analytical method to accurately detect and quantify them. While thin-layer chromatography (TLC) separation coupled with gas chromatography (GC) detection methods already exist, they do not allow for precise, sensitive, and accurate quantification of all anionic phospholipid species. Here we developed a method based on high-performance liquid chromatography (HPLC) combined with two-dimensional mass spectrometry (MS2 ) by MRM mode to detect and quantify all molecular species and classes of anionic phospholipids in one shot. This method is based on a derivatization step by methylation that greatly enhances the ionization, the separation of each peak, the peak resolution as well as the limit of detection and quantification for each individual molecular species, and more particularly for PA and PS. Our method universally works in various plant samples. Remarkably, we identified that PS is enriched with very long chain fatty acids in the roots but not in aerial organs of Arabidopsis thaliana. Our work thus paves the way for new studies on how the composition of anionic lipids is finely tuned during plant development and environmental responses.

A high-efficiency integrated strategy for the targeted discovery of novel barrigenol-type triterpenoid saponins from the shell of Xanthoceras sorbifolium Bunge by offline two-dimensional chromatography-Orbitrap mass spectrometry, neutral loss data acquisition, and predicted natural product screening

Natural products are considered as potential sources of leading compounds and play an important role in drug discovery. The liquid chromatography-mass spectrometry (LC-MS) technique is a powerful tool for compound-guided isolation from natural products. In this study, a high-efficiency integrated strategy was adopted to improve the new leading compounds discovery, including offline two-dimensional (2D) LC to extend the peak capacities, target neutral loss (NL) data-dependent acquisition (DDA) for barrigenol-type triterpenoids saponins and automatic screening through predicted natural product screening (PNPS) in TraceFinder. To validate the integrated strategy, the shell of Xanthoceras sorbifolium Bunge (XSB) was taken as a case. An offline 2D-LC system was constructed with hydrophilic interaction chromatography (HILIC) and reversed phase (RP) C18 column, and orthogonality of 0.66 and peak capacity of 3494. The 2D-LC system improved chromatographic baseline separation and peak resolution. Full MS/all ion fragmentation (AIF)/NL dd-MS2 DDA was employed for the detection of the barrigenol saponins. PNPS strategy was adopted and markedly extended the screening coverage. The combined strategy showed about 5 times improvement in the screening capability. The PNPS screening process, using TraceFinder software, discovered a total of 752 barrigenol saponins from the shell of XSB, including 707 potentially new barrigenol saponins, accounting for 94.02%. The feasibility of the strategy was also confirmed by the isolation of two novel barrigenol saponins, the structures of which were unambiguously identified using nuclear magnetic resonance (NMR). Furthermore, this strategy could also be applied to rapidly discover new bioactive constituents from other herbal medicines or other natural sources, especially the barrigenol saponins constituents.

Chitosan derivatives as dynamic coatings for transferrin glycoform separation in capillary electrophoresis

Chitosan and its derivatives are interesting biopolymers for different field of analytical chemistry, especially in separation techniques. The present study was aimed at testing chitosan water soluble derivatives as dynamic coating agents for application to capillary electrophoresis. In particular, chitosan was modified following three different chemical reactions (nucleophilic substitution, reductive amination, and condensation) to introduce differences in charge and steric hindrance, and to assess the effect of these physico-chemical properties in capillary electrophoresis. The effects were tested on the capillary electrophoretic separation of the glycoforms of human transferrin, an important iron-transporting serum protein, one of which, namely disialo-transferrin (CDT), is a biomarker of alcohol abuse. Chitosan derivatives were characterized by using NMR and 1H NMR, HP-SEC-TDA, DLS, and rheology. The use of these compounds as dynamic coatings in the electrolyte running buffer in capillary electrophoresis was tested assessing the peak resolution of the main glycoforms of human transferrin and particularly of disialo-transferrin. The results showed distinct changes of the peak resolution produced by the different derivatives. The best results in terms of peak resolution were achieved using polyethylene glycol (PEG)-modified chitosan, which, in comparison to a reference analytical approach, provided an almost baseline resolution of disialo-transferrin from the adjacent peaks.

Theoretical modeling and machine learning-based data processing workflows in comprehensive two-dimensional gas chromatography—A review

In recent years, comprehensive two-dimensional gas chromatography (GC × GC) has been gradually gaining prominence as a preferred method for the analysis of complex samples due to its higher peak capacity and resolution power compared to conventional gas chromatography (GC). Nonetheless, to fully benefit from the capabilities of GC × GC, a holistic approach to method development and data processing is essential for a successful and informative analysis. Method development enables the fine-tuning of the chromatographic separation, resulting in high-quality data. While generating such data is pivotal, it does not necessarily guarantee that meaningful information will be extracted from it. To this end, the first part of this manuscript reviews the importance of theoretical modeling in achieving good optimization of the separation conditions, ultimately improving the quality of the chromatographic separation. Multiple theoretical modeling approaches are discussed, with a special focus on thermodynamic-based modeling. The second part of this review highlights the importance of establishing robust data processing workflows, with a special emphasis on the use of advanced data processing tools such as, Machine Learning (ML) algorithms. Three widely used ML algorithms are discussed: Random Forest (RF), Support Vector Machine (SVM), and Partial Least Square–Discriminate Analysis (PLS-DA), highlighting their role in discovery-based analysis.

Detection of Precious Trace Metallic Elements in Charnockite Composition by PIXE Technique

The geochemical analysis of the middle Z precious metallic trace elements of the charnockite mineral composition was obtained by using proton induced X-ray emission at 3 MeV with a Si (Li) detector. Compared with other experimental nuclear analytical techniques like EPMA, XRF, and NAA, proton induced X-ray emission is used to detect with good accuracy and precision in the case of trace precious metals like Mo, Nb, Ru, Rh, and Ag, etc., in charnockite mineral composition due to the cross-sections with 3 MeV protons and good agreement. But peak resolution problems of K-X-rays of low Z and L-X-rays of the above elements which were presented in charnockite analysis must be solved and also change the detector parameters to obtain exact values in traces of the above elements in parts per million.

Chromatographic method development for simultaneous determination of serotonin, melatonin, and L‐tryptophan: Mass transfer modeling, chromatographic separation factors, and method prediction by artificial neural network

AbstractThis work endeavored to develop a high performance liquid chromatography (HPLC) method for simultaneous quantification of three important biotherapeutic molecules namely, L‐tryptophan, serotonin, and melatonin, present in low amounts in agro‐commodities. In the first approach, using pure chemical standards of the same in a mixture, chromatogram separation parameters such as peak sharpness, peak shouldering, and peak separation were judged by a human panel and biasness‐cum‐decision uncertainties were averted using fuzzy logic analysis. In the second approach, the separation parameters such as peak resolution and separation factors were evaluated to obtain a well‐resolved chromatogram. The parameters of the said separation process were successfully modeled by dimensionless numbers of mass transfer of the analytes in the column; and post‐fitting of mass transfer equations, high R2 was obtained suggesting successful development of the chromatographic process. Euclidean distances between the values of each chromatographic separation parameter and their respective ideal values; the defuzzified scores; findings of mass transfer study; and separation factors concomitantly established that the mobile phase of composition 1% acetic acid in HPLC water (A)–HPLC grade methanol (B) in gradient elution conditions (90% A–10% B) at a flow rate of 1 mL/min could simultaneously quantify the three molecules (μg) in button mushrooms with good resolution. The presence of the said biomolecules in the extract of button mushrooms was also confirmed by electrospray ionization (ESI)‐mass spectrometer (MS). An artificial neural network model (high R2) was also developed for chromatographic users, which would allow accurate prediction of the chromatographic parameters by varying mobile phase composition and flow rates.

A Novel Approach to AQbD-Assisted Green and Robust UPLC Method for the Determination of Selected Aminoquinoline Antimalarial Drugs: Assessment of Green Method

Greening analytical procedures have gained popularity in the area of pharmaceutical industries in order to safeguard the environment. In this study, an innovative methodology by integrating analytical quality-by-design (AQbD) along with Green Chemistry concepts with a systematic approach has been used to develop an environmentally-friendly and more robust ultra performance liquid chromatography (UPLC) method for the determination of three selected aminoquinoline antimalarial drugs namely amodiaquine hydrochloride (AMD), chloroquine phosphate (CHQ) and piperaquine phosphate (PPQ). An environmentally benign solvent ethanol has been chosen as an alternative to the commonly used acetonitrile and methanol, which are widely used. Based on the comprehensive risk analysis, the critical method parameters (CMP’s) that affect the critical method attributes (CMA’s) have been identified and the final method parameters were further optimized with the help of a full factorial design and the design of experiments (DOE), established the “design space”(DS) and identified the “method-operable-design-region (MODR) for the developed method. Achieved the separation with the use of an Acquity- UPLC BEH Shield RP-18 (100 mm × 2.1 mm), 1.7 μm column by using an isocratic elution of mobile phase containing 0.1% trifluoroacetic acid in water, ethanol in a mixture of 90:10% v/v and maintained a flow rate of 0.2 mL min-1 and the column oven temperature was 40 ºC and the UV detection wavelength of 225 nm was employed. A statistical tool Analysis of Variance (ANNOVA) has been used to assess the model’s statistical significance and found that the model’s p-values is < 0.00005 and its lack of fi is > 0.05 respectively, which demonstrates that the selected model is the most appropriate predictive tool for the analyzed responses R1 & R2 (i.e. peak resolutions R1 & R2). The proposed method’s linearity, accuracy & precision studies has been successfully validated in compliance with USP <1225> and ICH Q2 (R1) guidelines. Further assessed the proposed method’s greenness using various green evaluation tools such as: “complex green analytical procedure index”-cGAPI, “analytical greenness”-AGREE, “analytical method green score”-AMGS and found acceptable results. This novel AQbD-assisted eco-friendly analytical method for the quantification of AMD, CHQ & PPQ in bulk drugs (APIs) or finished dosage forms is simple, rapid, precise and accurate, robust and environmentally benign.

Micro gas chromatography column coated with ionic liquid/metal–organic framework composites as the stationary phase

In this paper, the μGC-IL/MOF and the μGC-IL were prepared using [P66614][NTf2]/ZIF-8 and [P66614][NTf2] as the stationary phase, respectively. [P66614][NTf2]/ZIF-8 composite stationary phase material has high specific surface area and porous structure, which increases the diffusion of gas molecules in the column. Compared to μGC-IL, μGC-IL/MOF can separate n-alkanes mixture (C5–C12) and lung cancer biomarkers (pentane, isoprene, acetone, benzene, 2-pentanone) with higher resolution, and the resolution (R) of pentane and isoprene was increased by 257.00% in particular. The μGC-IL/MOF can separate lung cancer biomarkers in about 5 min with optimal carrier gas velocity and column temperature. The retention times of pentane, isoprene, acetone, benzene, and 2-pentanone were 0.884 min, 1.246 min, 1.634 min, 2.204 min, and 3.049 min, respectively. The resolutions of adjacent peaks were 1.785, 1.525, 2.521, and 3.514, respectively. Which meets the requirements of quantitative analysis (R > 1.5). Therefore, the μGC-IL/MOF is expected to be integrated into portable devices for environmental monitoring and medical diagnosis in the future.

Photostability of vitamin C in industrialized fruit juices and isomers determination by HPLC-DAD

L-ascorbic acid (LAA) and D-isoascorbic acid (DIAA) are two of the most important antioxidants in industrialized fruit products as mixed fruit juices, fruit concentrates, and jams, in which they are added as antioxidants and as a nutrient. Despite that, LAA may undergo oxidative- and photo-degradation during storage, compromising its concentration and activities in these food products. In this work we aimed to optimize a method for the identification and quantification of LAA and DIAA by high performance liquid chromatography with diode-array detection (HPLC-DAD) using a NH2 column and a pre-heated mobile phase. A further aim was to investigate if food packing actually protects fruit juices against LAA photodegradation. For the UV photostability test, samples were UV-irradiated at 1416 μW cm−2, at 28 ± °C, and with a radiation energy above 200 W h m−2. The optimized HPLC method provided complete peak resolution of vitamin C isomers in less than nine min run-time. At the end of photostability tests with fruit juices and jellies packaged in polyethylene terephthalate and glass bottles or flasks, L-ascorbic acid was undetectable, suggesting that the packages did not provide effective protection against vitamin C photodegradation. To the best of our knowledge, vitamin C photostability in fruit products was previously unreported.

In-situ monitoring of thiazine molecular aggregation in various solvents via a free-standing acoustic levitator

In this work, we explored the in-situ reaction modeling of the molecular self-aggregation of methylene blue (MB), which is a cationic thiazine dye, in different solvents via a container-less acoustic levitator by floating of a single droplet. Our in-situ spectroscopic study revealed that the dimer essentially has a sandwich structural geometry with a deviation from parallel stacking and horizontal arrangements in the molecular planes. The real time conversion of the monomer in MB into a dimer and their dynamics in water and ethanol media were monitored using a free-standing acoustic levitator droplet system. The absorption spectra revealed changes in the two resolved peaks (monomer and dimer) and orderliness when water and ethanol were used as the media. Interestingly, the enhancement in the dimerization of MB could be attributed to droplet evaporation, which is difficult to observe in typical reactor containers. Moreover, acidic protonation resulted in a change in the aggregation orientation direction of the MB molecules, forming an unusual J-aggregation. Theoretical DFT calculations revealed that MB underwent typical H-aggregation and J-aggregation in the different solvent environments, and their orientations well matched the spectroscopic data.

Unlocking ultimate precision of intensity and area ratio measurements in Raman spectroscopy: Insights from simulation, experimentation, and theory and implications for isotope ratio analysis

AbstractThe intensity ratio (αI) and area ratio (αA) obtained using Raman spectroscopy are used widely to characterize the physical properties of gases, fluids, and solids, but the underlying parameters which affect their precision ( and ) have not been elucidated. We use simulations, experiments, and theoretical analyses to investigate the effects of instrumental performance, analytical conditions, and sample size on and . We identified the parameters which strongly influence : (1) the weaker peak intensity Iw; (2) the ratio of the bandwidth to pixel resolution of the weaker peak Γw/Δxw; (3) the degree of detector saturation; (4) with readout noise σR, dark noise σD, and shot noise σS; (5) drift; and (6) sample size. Theoretical and simulation results show that, when Γw/Δxw ≪ (Γs/Δxs)/αI, increasing Iw or Γw/Δxw by n times can improve by a factor of . Results showed that is a measure of how much the achievable in the experiment differs from that under ideal analytical conditions (i.e., ). When is not the case (i.e., when Iw is low), reducing σD or σR by decreasing the readout speed, setting a lower charge coupled device (CCD) sensitivity, reducing number of readouts, or narrowing vertical binning width can improve . We demonstrated that evaluations of or based on small sample sizes can engender physically unattainable precision. When the sample size is n = 5, 10, or 20, the average uncertainties of and correspond, respectively, to approximately 30%, 20%, and 15%. Giving an accurate and comparable assessment for and necessitates the reporting of intensity (in units of electrons), bandwidth, Δx, and the sample size.

A Versatile and Efficient Method to Isolate DNA-Polymer Conjugates.

We present a facile and adaptable method to purify and isolate DNA-polymer conjugates from different uncharged homo, random, or block copolymer families. Anion exchange chromatography is used to separate the reaction solution and retrieve the excess unreacted polymer and oligonucleotide. The stationary phase has a high efficiency (25 nmol of DNA per run), facilitating the purification of large batches without compromising the peak shape and resolution. To demonstrate the versatility of this method, different types of polymers, including acrylates, methacrylates, and acrylamides containing hydrophilic and hydrophobic blocks, were purified with high yields. Additionally, DNA-polymer conjugates with various DNA block lengths were also successfully purified, further highlighting the broad applicability of this method.

Open Port Interface for Coupling Capillary Electrophoresis and Mass Spectrometry: Performance Evaluation for Capillary Isoelectric Focusing.

Capillary electrophoresis (CE) combined with mass spectrometry (MS) is a powerful analytical technique that utilizes the resolving power of CE and the mass-detection capabilities of MS. In many cases, CE is coupled to MS via a sheath-flow interface (SFI). This interface has a simple design and can be easily constructed; however, it often suffers from issues such as MS signal suppression, interference of MS and CE electrical circuits, and the inability to set an optical point of detection close to the capillary end due to the specific design of the coupling union. In this paper, we describe a novel coupling of CE and MS based upon the open port interface (OPI). The OPI differs from classical sheath flow interfaces by operating at flow rates at least 1 order of magnitude higher. In addition to the flow rate difference, the OPI provides more efficient mixing of the capillary eluates with the transport fluid and thus minimizes MS signal suppression. In this work, we compared the performance of OPI and SFI in a series of capillary isoelectric focusing (cIEF) experiments with 5 pI markers, carbonic anhydrase II and NIST antibody. The evaluation criteria for the comparison of the OPI and SFI were analytical sensitivity, reproducibility, and pI marker linearity. Given the extent of sample dilution in the OPI, we also compared the peak resolution determined using an upstream UV detector to those determined by the downstream mass spectrometer. The results suggested that the OPI configuration reduced signal suppression, with no adverse effect on peak resolution. In addition, the OPI provided better decoupling of the CE and MS potentials as well as reduced signal dependence upon the sheath liquid composition. While these results are preliminary, they suggest that the OPI is a viable approach for CE-MS coupling.

Analytical studies on some pesticides with antifungal effects: Simultaneous determination by HPLC, investigation of interactions with DNA and DNA damages

A simple, and fast method was developed for the simultaneous determination of five fungicides, namely thiram (THR), epoxiconazole (EPO), hexaconazole (HEX), tebuconazole (TEB), and diethofencarb (DIE), in different matrices by HPLC-UV. Parameters influencing the peak shape and resolution, such as the composition of mobile phase, pH and concentration of buffer solution, and column temperature, were examined and optimized. The proposed method was validated in terms of linearity, sensitivity, precision, and accuracy. Forced degradation studies were carried out for all analytes to demonstrate the specificity of the method and to evaluate the stability of analytes under different conditions. DNA interaction and DNA damage studies were conducted by HPLC and comet assay, respectively. All fungicides were found to bind DNA, except for DIE. While the binding coefficients for EPO, HEX, and TEB were of the order of 104, THR was found to interact more strongly with DNA with a binding coefficient of higher than 106. DIE did not induce DNA damage at any concentration tested. On the other hand, TEB, HEX, and EPO induced DNA damage up to 30 µg/mL. THR showed cytotoxic effects at 20 and 30 µg/mL and caused significant DNA damage at lower concentrations.

High-performance microchip electrophoresis separations of preterm birth biomarkers using 3D printed microfluidic devices

We employed digital light processing-stereolithography 3D printing to create microfluidic devices with different designs for microchip electrophoresis (µCE). Short or long straight channel, and two- or four-turn serpentine channel microfluidic devices with separation channel lengths of 1.3, 3.1, 3.0, and 4.7 cm, respectively, all with a cross injector design, were fabricated. We measured current as a function of time and voltage to determine a separation time window and conditions for the onset of Joule heating in these designs. Separations in these devices were evaluated by performing µCE and measuring theoretical plate counts for electric field strengths near and above the onset of Joule heating, with fluorescently labeled glycine and phenylalanine as model analytes. We further demonstrated µCE of peptides and proteins related to preterm birth risk, showing increased peak capacity and resolution compared to previous results with 3D printed microdevices. These results mark an important step forward in the use of 3D printed microfluidic devices for rapid bioanalysis by µCE.