Peak Tailing Research Articles

A fast, fully validated GC-MS method using a simplified pretreatment for the quantification of short and branched chain fatty acids in human stool.

The study of short (SCFAs) and branched chain fatty acids (BCFAs) in human stool related to gastrointestinal diseases, gut microbiota, metabolism, and diet has dramatically increased. As a result, a fast, reliable method with minimal pretreatment is needed for quantification of these metabolites (acetic, propionic, isobutyric, butyric, isovaleric, valeric, and caproic acid) in stool. Therefore, a GC-MS method meeting this criterion was developed. A bias sampling study showed no statistical difference (p>0.05) in analyte means when comparing 100 mg subsamples of homogenized to non-homogenized samples (n=6, p values 0.153-0.910). Stool samples were homogenized, diluted with 80:20 water:methanol (v/v), and adjusted to a pH of 1.5-2.5. Samples were vortexed, centrifuged, and directly injected into the GC-MS using pulsed splitless injection offering twofold-to-threefold signal enhancement over a 10:1 split injection. DB-FATWAX Ultra Inert Polyethylene Glycol (PEG) Column showed no peak tailing, reduced responses, or retention time shifts after 1,476 stool injections, while other columns failed before 361 injections. Intra- and inter-day accuracy for stool supernatant samples ranged from -10.21% to 8.88% and -13.25% to 9.91%, while intra- and inter-day precision ranged from 0.21% to 1.21% and 0.89% to 2.84% coefficient of variation (CV), respectively. This method demonstrates excellent linearity (0.9999-1.0000) and low limits of quantification (1.50-8.01 μM). Stool samples proved stable stored at -20°C up to 28 days, and recoveries ranged from 85.04% to 106.59%. Matrix effects in stool are non-significant determined by comparing standard and stool supernatant calibration curve slopes (p>0.05).

Comprehensive two-dimensional gas chromatography using direct flow modulation to extend the secondary dimension separation time

A simple direct flow modulator has been constructed and evaluated. This modulator employs a tee to connect the primary and secondary columns so that a negative pulsed flow can be introduced through the third leg of the connector into the joint between the columns. The modulation gas pressure can be adjusted to allow a longer recovery time for the primary column flow after the reversal initiated at the beginning of a modulation period, resulting in a longer secondary separation time. In this study, a 120 s secondary separation time has been achieved. That is long enough for use with a longer secondary column and secondary temperature ramping. Factors which affect the secondary peak width at base (2Wb), including modulation pulse width, modulation period, and inlet/modulation pressure differential, have also been investigated. Our results indicate that all three of these factors have a large impact on 2Wb, since they all affect the amount of primary effluent loaded onto the secondary dimension. Various sizes of tee connectors – 360 µm, 1/32″, and 1/16″ – have been investigated as well. Out of those three, the 360 µm tee gives the best performance in terms of less peak tailing and narrower 2Wb. The time needed to switch from one dimension GC to GC×GC for this method is discussed, and several methods to shorten the waiting time have been proposed. Applications of this method on gasoline and reference gas oil standard have been demonstrated.

Historical analysis (2001–2019) of low‐level wind shear at the Hong Kong International Airport

AbstractThis paper analyses over 10,000 quality‐controlled pilot reports of low‐level wind shear (‘wind shear’) at the Hong Kong International Airport (HKIA; ICAO code: VHHH) between 2001 and 2019. HKIA is well known for its susceptibility to wind shear, which is a potential hazard for aircraft during landing and take‐off. Wind shear at HKIA exhibits strong seasonality with double peaks in the middle of the spring and summer months. There is a strong diurnal cycle in report numbers, peaking towards the afternoon, as modulated by air traffic at HKIA. On average, there are 115 days per year with wind shear reported, with possible power law distribution in the number of days with different number of reports. By comparing the background wind distribution during those minutes with pilot reports against the climatological distribution, wind shear is observed to be, on average, favoured under higher wind speeds (≥6 m s−1) and reduced under lower speeds with shifted frequency peak and heavier tail, although statistical behaviour can differ significantly across individual runway corridors. Preferred background wind directions for wind shear occurrence highlight the role of terrain influence upstream of HKIA. While positive shear (65.6%) is more often reported than negative shear (34.4%), both types of wind shear events appear to follow an exponential distribution in shear magnitude, with similar rates of decay. This is by far the largest statistical study of low‐level wind shear at an airport. Results can serve as an important local reference in addition to being a useful example for airports around the world.

FINANCIAL TIME SERIES USING NONLINEAR DIFFERENTIAL EQUATION OF GAUSSIAN DISTRIBUTION PROBABILITY DENSITY

To further explore the research of financial time series prediction and broaden the application scope of Gaussian distribution probability density equation, based on the nonlinear differential equation of Gaussian distribution probability density, the semi-supervised Gaussian process model is taken as the research object to discuss the application of semi-supervised Gaussian process model in the stock market. Shanghai 180 Index, Shanghai (Securities) Composite Index and the yield of three stocks are studied in detail. The specific results are as follows. The prediction accuracy of Shanghai 180 Index is 83%, and the prediction accuracy of Shanghai (Securities) Composite Index is 78%. The stock yield series curves of the three stocks have the characteristics of peak and thick tail, which do not obey the normal distribution. Among the three models of semi-supervised Gaussian process model, initial Gaussian process model and SVM algorithm model, the prediction accuracy of semi-supervised Gaussian process model is the best, and the prediction accuracy of the yield of three stocks is 82.45%, 85.03% and 84.53%, respectively. The research results can fully prove that the semi-supervised Gaussian process model has good application effect in stock time series prediction. The research content can provide scientific and sufficient reference for the follow-up research of financial time series, and also has important significance for the research of Gaussian process model.

Ultra-High-Performance Micellar Liquid Chromatography Comparing Tween 20 and Tween 40 for the Determination of Hydroxycinnamic Acids

A simple and green ultra-high-performance micellar liquid chromatography (MLC) method was developed here, comparing Tween 20 and Tween 40 for the first time as the only mobile phase modifiers with a C18 column. Its application to the separation of nine hydroxycinnamic acid (HCA) derivatives (cinnamic, caffeic, ferulic, sinapic, o-, m-, p-coumaric, 3,4-dihydroxyhydrocinnamic, and chlorogenic acids) was made, due to their importance as antioxidants in a variety of natural beverages such as wine and coffee. The optimal conditions of 45 °C temperature (T), 1% surfactant in the mobile phase, and pH control with 2.5 mM sulfuric acid were determined and used to elucidate the analytical figures of merit. Although the effect of these conditions was insignificant between the two surfactants, the nine-component HCA mixture was separated faster—in about 15 min—and with less peak tailing using Tween 20 than with Tween 40. The linearity of the Van’t Hoff (lnk versus 1/T) plots was evident for Tween 20, indicating a single retention mechanism—but less so for Tween 40. The equilibrium constants of the analytes with the micelles and the stationary phase were calculated. The developed method was successfully used to analyze organic red wine, spiked organic red wine, and green coffee diet pills. The percent recoveries of the nine HCA compounds spiked in the organic red wine ranged from 90% to 107%. The green coffee extract diet pills showed the presence of a significant amount of chlorogenic acid.

Application of hybrid surface technology for improving sensitivity and peak shape of phosphorylated lipids such as phosphatidic acid and phosphatidylserine

The use of hybrid surface technology (HST), applied to the metal surfaces of an ACQUITY™ UPLC™ system and column, designed to mitigate the chelation, poor peak shape and analyte loss seen with acidic phospholipids was investigated. Compared to a conventional system significant improvements in both sensitivity, recovery and peak shape were obtained following UPLC on a CSH C18 column when the HST was used for the analysis of lysophosphatidic acid (LPA), phosphatidic acid (PA), lysophosphatidylserine (LPS), phosphatidylserine (PS), phosphatidylinositol-monophosphates (PIP), ceramide phosphate (CerP) and sphingoid base phosphate (SPBP). The benefits in chromatographic performance provided by the HST were seen particularly at low concentrations of these analytes. The HST system and column reduced peak tailing by 65–80% and peak width by 70–86% for LPA and PA. Moreover, increased signal intensities of up to 12.7 times were observed for LPA with the HST approach compared to the equivalent untreated LC system and column. The application of this methodology to the analysis of chicken egg PA and brain porcine PS extracts were accompanied by similar improvements in data quality.

Development and Validation of a Novel RP-HPLC Method for the Determination of Cetrimide and Chlorhexidine Gluconate in Antiseptic Solution

Cetrimide (CE) is a quaternary ammonium compound and a cationic surfactant, which can be used as an antiseptic and preservative in various formulations. Antiseptic solutions of Cetrimide are available in combination with Chlorhexidine Gluconate (CHG) for external use. Chlorhexidine is a biguanide with high microbicidal activity and is widely known as a skin disinfectant. The present work displays the development and validation of an RP-HPLC isocratic method for the simultaneous determination of CE and CHG. The method consists of a Hypersil® SAS C1 (4.6 × 250 mm) 5 μm column, with a mobile phase of 85%/15% v/v MeOH-NaH2PO4·H2O, aqueous solution. In addition, 0.2% of triethylamine (Et3N) was added to the buffer for the confrontation of peak tailing, and then the pH was adjusted to 3.0 with ortho-phosphoric acid (H3PO4). The flow rate was set at 1 mL/min, and adequate detection was achieved with a diode array detector (PDA) at 205 nm. The method was successfully validated according to ICH guidelines for specificity, linearity, accuracy, precision and stability for sample and standard solutions. In addition, the robustness of the method was evaluated through statistical and graphical analysis, using a fractional factorial experimental design.

Biological Effects of Monoenergetic Carbon Ions and Their Associated Secondary Particles.

DNA double-strand breaks (DSBs) are the main factor behind carbon-ion radiation therapy (CIRT)-induced cell death. Nuclear interactions along the beam path between the primary carbon ions and targets result in nuclear fragmentation of carbon ions and recoiled particles. These secondary particles travel further distances past the Bragg peak to the tail region, leading to unwanted biological effects that may result in cytotoxicity in critical organs and secondary induced tumors following CIRT. Here, we confirmed that the density of the DSB distributions increases as the cell survival decreases at the Bragg peak and demonstrated that by visualizing DSBs, the various LET fragmentation ions and recoiled particles produced differences in their biological effects in the post-Bragg peak tail regions. This suggests that the density of the DSBs within the high-LET track structures, rather than only their presence, is important for inducing cell death. These results are essential for CIRT treatment planning to limit the amount of healthy cell damage and reducing both the late effect and the secondary tumor-associated risk.

A Validated Reverse-Phase High Performance Liquid Chromatography (RP-HPLC) Method for the Quantification of Gamma- Tocotrienol in Tocotrienol Rich Fractions of Crude Palm Oil

Background: Palm oil and its constituents have wide applications in food, cosmetics and pharmaceutical industries. The tocotrienol-rich fractions of crude palm oil have drawn greater research interest in recent years due to their potent health benefits. Therefore, reliable and validated analytical methods are essential for the quantification of tocotrienols. Objective: This study aimed to develop a simple and economical RP-HPLC method for the quantification of gamma-tocotrienol in tocotrienol-rich fractions of crude palm oil. Methods: An Agilent HPLC system supplied with a Diode Array detector and an auto-injector system was used for the method development, and the wavelength was set 295 nm. A reversedphase C18 column maintained at 30 °C using a mobile phase composition of methanol: water (95:05) at a flow rate of 1 mL/min was used for the analysis. The developed method was validated according to ICH guidelines. Results and Discussion: A symmetrical peak of gamma-tocotrienol was observed at 8.7 minutes with minimal peak tailing (between 0.76 and 0.78), and an acceptable resolution above 2.0. Excellent linearity was evident with R2 values 0.9996 and 0.9991 for intra-day and interday, respectively. The method demonstrated a high precision (%RSD values ≤ 5.8%) and accuracy (%RE<9.6%). The LOD and LOQ of gamma-tocotrienol were determined as 1.4 μg/mL and 4.2 μg/mL, respectively. The system suitability studies indicate that the chromatographic parameters are well within the acceptable limit. Conclusion: In conclusion, the developed RP-HPLC method is rapid, precise, stable and economical for the quantification of gamma-tocotrienol.

High Throughput UHPLC-MS-Based Lipidomics Using Vacuum Jacketed Columns.

Reversed-phase UHPLC-MS is extensively employed for both the profiling of biological fluids and tissues to characterize lipid dysregulation in disease and toxicological studies. With conventional LC-MS systems the chromatographic performance and throughput are limited due to dispersion from the fluidic connections as well as radial and longitudinal thermal gradients in the LC column. In this study vacuum jacketed columns (VJC), positioned at the source of the mass spectrometer, were applied to the lipidomic analysis of plasma extracts. Compared to conventional UHPLC, the VJC-based methods offered greater resolution, faster analysis, and improved peak intensity. For a 5 min VJC analysis, the peak capacity increased by 66%, peak tailing reduced by up to 34%, and the number of lipids detected increased by 30% compared to conventional UHPLC. The narrower peaks, and thus increased resolution, compared to the conventional system resulted in a 2-fold increase in peak intensity as well a significant improvement in MS and MS/MS spectral quality resulting in a 22% increase in the number of lipids identified. When applied to mouse plasma samples, reproducibility of the lipid intensities in the pooled QC ranged from 1.8-12%, with no related drift in tR observed.

On-line Sequencing of CRISPR Guide RNAs and Their Impurities via the Use of Immobilized Ribonuclease Cartridges Attached to a 2D/3D-LC-MS System.

In this study, for the first time, the automated digestion and sequencing of an RNA molecule via the use of immobilized RNase cartridges attached to a multidimensional liquid chromatography (LC)-mass spectrometry (MS) system are presented. We first developed an on-line digestion-HILIC two-dimensional (2D)-LC-MS method in order to sequence CRISPR guide RNAs for gene editing. Three RNases (T1, A, and U2) were immobilized on polyetheretherketone cartridges, and their performance was evaluated. Ultrafast digestions were performed within 2.3 min with the on-line approach versus 30 min via the conventional off-line approach. The higher sequence coverage was achieved by the RNase T1 (71%), which is the same as the off-line mode. A 20-fold reduction in the gRNA sample amount was achieved with the on-line digestion approach (6.5 μg) in comparison to that with the off-line approach (130 μg). In the second step, a three-dimensional (3D)-LC-MS method was developed for the sequencing of fractions collected on-line across the main peak and the partially separated tail by the reference ion-pairing RPLC method. Additional insights were gained in order to better understand the cause of the main peak tailing.

Influence of metals in the column or instrument on performance in hydrophilic interaction liquid chromatography

A method is proposed for measuring the relative contribution of extracolumn and column effects to the detrimental interactions which occur between metal-sensitive solutes and the complete HPLC system. The method involves the substitution of a length of narrow bore silica tubing for the column and measuring the extracolumn contribution, which is subtracted from the total bandspreading measured with a column in place to yield the column contribution. The investigation focussed on HILIC separations, which have been relatively little studied compared with similar effects in RPLC. Metal-solute interactions can lead to tailing peaks and reduced sensitivity or even irreversible adsorption of particularly challenging solutes such as mono-, di- and triphosphorylated nucleotides, which show strong interactions between their phosphate groups and metals. A deactivated HILIC column, treated by a vapour deposition procedure gave generally good results when using high pH (pH 9.0) mobile phases, which suppress the effects of metals. The addition of metal complexing agents such as citrate at low millimolar concentration gave further improvements in peak shape at high pH, and even micromolar concentrations of citrate or medronic acid showed good results. These lower concentrations are more favourable for LC-MS. Addition of the higher concentration of citrate gave acceptable results for the nucleotides even at low pH (pH 3.0). With the standard UHPLC instrument used, loss of efficiency due to metal solute interactions was 25% or less, with most losses due to interactions with the column, although this result will depend on the condition and design of the instrument, which is easily assessed by the proposed procedure.

A carbonylative coupling approach to alkyl stationary phases with variable embedded carbamate groups for high-performance liquid chromatography

A highly efficient carbonylative coupling method for the preparation of alkyl stationary phases with variable numbers of carbamate groups was established. The effectiveness of such method was verified through elemental analysis, X-ray photoelectron spectroscopy and solid-state 13C nuclear magnetic resonance spectroscopy of three as-synthesized stationary phases bearing different alkyl chains and different numbers of carbamate groups (octadecyl/one carbamate group, C18C; docosyl/three carbamate groups, C22C3; triacontyl/two carbamate groups, C30C2). The comparative evaluation of these stationary phases using a great variety of analytes, including three sets of isomers of alkylbenzenes, two sets of standard mixtures of polycyclic aromatic hydrocarbons (SRM 1647e and 869b), nine polychlorinated biphenyls, fiveteen N-substituted ureas, ten sulfonylureas, five xanthines and some other phytonutrients, revealed their remarkable applicability in reversed-phase liquid chromatography. Notably, the intercalated carbamate groups rendered the resultant stationary phases compatible with 100% aqueous mobile phase. The suppression of silanol activity was positively related to the number of polar groups embedded in the bonded selector, and the smallest peak tailing factor (1.14) for amitriptyline was obtained by C22C3. The molecular shape-related selectivity was found to be more closely related to the length of the selector's aliphatic chain, as supported by the lowest αTBN/BaP value (0.31) by C30C2. These carbamate-embedded alkyl stationary phases constituted another class of polar-embedded stationary phases possessing a single type of functional ligand.

Design of experiment-based LC-MS/MS method development for simultaneous estimation of nateglinide and metformin hydrochloride in rat plasma.

This research aims to develop and validate a bioanalytical method for simultaneous estimation of an antidiabetic combination using LC-MS/MS in rat plasma. Nateglinide and metformin hydrochloride are commonly used combination for clinical management of Type 2 diabetes. Hence, simultaneous determination in plasma is essential for the rapid analysis of samples from the pharmacokinetic studies. Statistical optimization was carried out for liquid chromatography (LC) parameters and mass spectroscopic (MS) parameters by design of experiment (DoE) (Design Expert Version 11, Stat Ease Inc., USA) approach. A 33 full factorial design was used for optimization of LC parameters; %methanol, %formic acid, and flow rate were selected as independent variables, whereas peak area and tailing factor were considered as dependent variables for both drugs. Box-Behnken design was used to optimize MS parameters including drying gas flow rate, nebulizing gas flow rate, DL temperature, heat block temperature, and positive voltage as independent factors, and responses selected were [M + H]+ intensity of nateglinide and metformin hydrochloride. The [M + H]+ intensity of the optimized method for nateglinide and metformin hydrochloride were 2,462,838 and 11,873,826, respectively. The model was found significant for optimizing LC and MS parameters with p < 0.05 for both nateglinide and metformin hydrochloride. The optimized method was validated as per the ICH-M10 guideline, which was accurate, precise, and selective. The method was cost-effective and capable of quantitating concentrations in picogram levels for nateglinide and metformin hydrochloride simultaneously.

Low-energy electron ionization optimization for steroidomics analysis using high-resolution mass spectrometry.

Systematic electron ionization fragmentation studies of steroids have been performed to elucidate and trace their characteristic fragmentation patterns. However, the electron ionization source setting at 70 eV electron energy is much higher than the ionization potential (7-15 eV) of most organic compounds, leading to extensive fragmentation. We present a multifactorial study on optimizing a low-energy electron ionization source to maximize molecular ion formation while minimizing the extent of fragmentation to improve the analytical sensitivity of steroids, especially the more thermolabile ones, while preserving the information that can be extracted from the data. Twenty-seven steroid reference materials, chosen to cover four main classes of urinary steroids, were considered; gas chromatography/quadrupole time-of-flight (GC/qTOF) analyses were carried out using an Agilent Technologies model 8890 gas chromatograph coupled to an Agilent Technologies model 7250 accurate-mass quadrupole time-of-flight (GC/qTOF) instrument. The effects of electron energy, emission current, and source temperature, as well as their potential interactions on steroid fragmentation pathways, have been assessed in full factorial experimental designs. Three parameters were specifically evaluated to improve the chromatographic/spectrometric response of the selected steroids: (i) degree of fragmentation; (ii) relative abundance of the molecular ion; and (iii) peak width. The first two were evaluated by screening designs that highlighted collision energy and source temperature as the most influential factors on the analytical responses of the considered steroids, while emission current always showed a non-significant influence. Then, an optimization design was performed to select the final source setting by searching for the combination of factors that minimize peak tailing. The proposed analytical approach permits a faster selection of optimal experimental conditions for steroidomics analysis using low-energy electron ionization and high-resolution mass spectrometry. The development of these designs of experiments (DoE) in full factorial design (FFD) allowed multiple inputs to be monitored at the same time, highlighting the possible interactions and estimating the effects of a factor in the different levels of the other factors considered.

Cosine Willow Tree Structure under Lévy Processes with Application to Pricing Variance Derivatives

Lévy process models can capture the large price changes on sudden exogenous events and can better demonstrate the high peak and heavy tail characteristics of financial data. The Fourier transformation method is famous for pricing derivatives under the Lévy processes beause of its efficiency, how it separates models from payoff function, and how it handles models with characteristic functions, but it is criticized for its restriction on path dependency. In this article, we propose a unified cosine willow tree method, which inherits the merits of the transformation method but overcomes its shortcomings. Moreover, the hedging Greeks can be obtained as a by-product from the tree structure with minor extra cost. Some popular variance derivatives are also discussed to demonstrate the flexibility of the proposed method in handling path dependency. Finally, the theoretical convergence is analyzed for various Lévy process models.

Particle movement characteristics in a gas–solid vertical single helical ribbon agitated reactor

The gas–solid vertical single helical ribbon agitated reactor (G-S-VSAR) is a gas–solid dense-phase agitated reactor, in which the interaction between the agitator and the dense granules dominates the flow field and transfer behavior. The particle movement characteristics are essential for determining the reactor space–time yield and product quality. In this work, the particle residence time distribution (RTD) was measured through magnetic-particles pulse experiment to investigate the overall movement and mixing characteristics of a G-S-VSAR, with the effects of rotation speed and gas velocity studied. The RTD curves were featured by time lag, bypass peak and exponential tail, and thus a model of ‘PFR + double parallel CSTRs’ was established. Results showed that the increase in rotation speed could eliminate the bypass, but only reduce the lag time. The lag time adversely influenced the mixing. Photography was applied to characterize the local particle movements near the reactor wall. It was found that the particles spiraled upwardly along the wall in laminar-like flow and the fully mixed state reached after one circulation. During the spiraled process, the undulating displacement in the vertical direction was induced by agitation in the ribbon-wall gap, which inhibited the radial mixing. Therefore, a narrow gap was recommended for reducing such undulating movements and promoting radial mixing.

The Proteasome Inhibitor Bortezomib Induces Apoptosis and Activation in Gel-Filtered Human Platelets

Bortezomib (BTZ) has demonstrated its efficacy in several hematological disorders and has been associated with thrombocytopenia. There is controversy about the effect of BTZ on human platelets, so we set out to determine its effect on various types of platelet samples. Human platelets were investigated in platelet-rich plasma (PRP) and as gel-filtered platelets (GFPs). Mitochondrial inner membrane potential depolarization and phosphatidylserine (PS) and P-selectin expression levels were studied by flow cytometry, while thrombin generation was measured by a fluorescent method. In PRP, BTZ caused negligible PS expression after 60 min of treatment. However, in GFPs, PS expression was dose- and time-dependently increased in the BTZ-treated groups, as was P-selectin. The percentage of depolarized cells was also higher after BTZ pretreatment at both time points. Peak thrombin and velocity index increased significantly even with the lowest BTZ concentration (p = 0.0019; p = 0.0032) whereas time to peak and start tail parameters decreased (p = 0.0007; p = 0.0034). The difference between PRP and GFP results can be attributed to the presence of plasma proteins in PRP, as the PS-stimulating effect of BTZ could be attenuated by supplementing GFPs with purified human albumin. Overall, BTZ induces a procoagulant platelet phenotype in an experimental setting devoid of plasma proteins.

High-Throughput UHPLC/MS/MS-Based Metabolic Profiling Using a Vacuum Jacketed Column.

In UHPLC, frictional heating from the eluent flowing through the column at pressures of ca. 10-15 Kpsi causes radial diffusion via temperature differences between the center of the column and its walls. Longitudinal dispersion also occurs due to temperature gradients between the inlet and outlet. These effects cause band broadening but can be mitigated via a combination of vacuum jacketed stainless steel tubing, reduced column end nut mass, and a constant temperature in the column from heating the inlet fitting. Here, vacuum jacketed column (VJC) technology, employing a novel column housing located on the source of the mass spectrometer and minimized tubing from the column outlet to the electrospray probe, was applied to profiling metabolites in urine. For a 75 s reversed-phase gradient separation, the average peak widths for endogenous compounds in urine were 1.2 and 0.6 s for conventional LC/MS and VJC systems, respectively. The peak tailing factor was reduced from 1.25 to 1.13 when using the VJC system compared to conventional UHPLC, and the peak capacity increased from 65 to 120, with a 25% increase in features detected in urine. The increased resolving power of the VJC system reduced co-elution, simplifying MS and MS/MS spectra, providing a more confident metabolite identification. The increased LC performance also gave more intense MS peaks, with a 10-120% increase in response, improving the quality of the MS data and detection limits. Reducing the LC gradient duration to 37 s gave peak widths of ca. 0.4 s and a peak capacity of 84.

Applying Log-Normal Peak Fitting to Parallel Reaction Monitoring Data Analysis.

Chromatographic separation is often an important part of mass-spectrometry-based proteomic analysis. It reduces the complexity of the initial samples before they are introduced to mass-spectrometric detection and chromatographic characteristics (such as retention time) add analytical features to the analyte. The acquisition and analysis of chromatographic data are thus of great importance, and specialized software is used for the extraction of quantitative information in an efficient and optimized manner. However, occasionally, automatic peak picking and correct peak boundary setting is challenged by, for instance, aberration of peak shape, peak truncation, and peak tailing, and a manual review of a large number of peaks is frequently required. To support this part of the analysis, we present here a software tool, Peakfit, that fits acquired chromatographic data to the log-normal peak equation and reports the calculated peak parameters. The program is written in R and can easily be integrated into Skyline, a popular software packages that is frequently used for proteomic parallel reaction monitoring applications. The program is capable of processing large data sets (>10 000 peaks) and detecting sporadic outliers in peak boundary selection performed, for instance, in Skyline. In an example data set, available via ProteomeXchange with identifier PXD026875, we demonstrated the capability of the program to characterize chromatographic peaks and showed an example of its ability to objectively and reproducibly detect and solve problematic peak-picking situations.