Peak Capacity Research Articles

A comprehensive investigation of the peak capacity for the reversed-phase gradient liquid-chromatographic analysis of intact proteins using a polymer-monolithic capillary column

The present study reports on the analysis of different factors affecting the magnitude of the peak capacity for intact protein separations conducted in gradient reversed-phase liquid chromatography. Experiments were conducted using a 200 µm i.d. capillary styrene-co-divinylbenzene monolithic column that was developed in-house and was characterized by a mode globule cluster size of 1.2 µm and a mode macropore size of 1.0 µm (based on scanning electron microscopy). The monolith yielded a minimum plate-height value of 13.3 µm for uracil. The use of trifluoroacetic acid instead of formic acid as ion-pairing agent generally led to better peak symmetry, narrower peak widths which effect is protein-dependent, and improved loadability characteristics. The peak capacity has been systematically assessed at different flow rates and gradient duration. The highest peak capacity of 247 was obtained at a flow rate of 1 µL min−1 and a gradient time of 120 min, which corresponds to an optimal tG/t0 ratio of ∼60. While the optimum van Deemter velocity for intact proteins was approximated to be 0.065 µL min−1, the highest peak capacity was achieved at approximately 20-fold higher flow rate, depending on the gradient duration applied and the molecular weight of the proteins. The optimum velocity increased with decreasing gradient time and is a compromise between the magnitude of the mass-transfer contribution (decreasing the peak capacity with velocity) affected by molecular diffusion, and the increase in peak capacity induced by the more favorable gradient-volume ratio.

Achieving a Peak Capacity of 1800 Using an 8 m Long Pillar Array Column.

In the present study, the peak capacity potential of ultralong porous cylindrical pillar array columns is investigated. Coupling 4 columns of 2 m long allows for working near the minimal separation impedance of small molecules under retained conditions at a maximal pressure load of 250 bar. Minimal plate heights of H = 5.0 μm, H = 6.3 μm, and H = 7.7 μm were obtained for uracil (unretained), butyrophenone (k = 0.85), and valerophenone (k = 1.94), respectively, corresponding to a number of theoretical plates of N = 1.6 × 106, N = 1.2 × 106, and N = 1.0 × 106. The optimal linear velocities were 0.60 mm/s for a retained compound and 0.74 mm/s for an unretained compound. Based on a mixture of 9 compounds, the peak capacity nc was determined as a function of gradient time (tG). Peak capacities (tG-based) of 1103 and 1815 were obtained when applying 650 min and 2050 min gradients (tG/t0 = 4.5 and 14, respectively, with tG as the gradient time and t0 as the void time). These values are much higher than earlier reported peak capacity values for small molecules.

Maximizing two-dimensional liquid chromatography peak capacity for the separation of complex industrial samples

We report on a study on the use of 2D-LC in industry wherein we maximized the peak capacity by serially coupling up to six 15 cm long columns in the 1st dimension. For the considered aromatic amine oligomer sample, the combination of reverse phase pentafluorophenyl column providing selectivity based on π–π interaction in the 1st and a more retaining reverse phase polymeric C18 column in the 2nd dimension proved to give the highest orthogonality, calculated to be 0.82. Whereas a 1D run on a single column revealed around 120 compounds, the optimized 2D-LC system revealed around 940 compounds. To achieve this, flow splitting to improve the peak capacity in the 1st dimension and shifting gradients in the 2nd dimension were used. The overall peak capacity of the system was calculated to be 11,000 with correction for orthogonality and undersampling. The total analysis time with the 6-column system was around 20 h.

Analyzing Demand Response in a Dynamic Capacity Expansion Model for the European Power Market

One of the challenges in the transition towards a zero-emission power system in Europe will be to achieve an efficient and reliable operation with a high share of intermittent generation. The objective of this paper is to analyse the role that Demand Response (DR) potentially can play in a cost-efficient development until 2050. The benefits of DR consist of integrating renewable source generation and reducing peak load consumption, leading to a reduction in generation, transmission, and storage capacity investments. The capabilities of DR are implemented in the European Model for Power Investments with high shares of Renewable Energy (EMPIRE), which is an electricity sector model for long-term capacity and transmission expansion. The model uses a multi-horizon stochastic approach including operational uncertainty with hourly resolution and multiple investment periods in the long-term. DR is modelled through several classes of shiftable and curtailable loads in residential, commercial, and industrial sectors, including flexibility periods, operational costs, losses, and endogenous DR investments, for 31 European countries. Results of the case study shows that DR capacity partially substitutes flexible supply-side capacity from peak gas plants and battery storage, through enabling more solar PV generation. A European DR capacity at 91 GW in 2050 reduces the peak plant capacities by 11% and storage capacity by 86%.

Rapid breath analysis for acute respiratory distress syndrome diagnostics using a portable two-dimensional gas chromatography device.

Acute respiratory distress syndrome (ARDS) is the most severe form of acute lung injury, responsible for high mortality and long-term morbidity. As a dynamic syndrome with multiple etiologies, its timely diagnosis is difficult as is tracking the course of the syndrome. Therefore, there is a significant need for early, rapid detection and diagnosis as well as clinical trajectory monitoring of ARDS. Here, we report our work on using human breath to differentiate ARDS and non-ARDS causes of respiratory failure. A fully automated portable 2-dimensional gas chromatography device with high peak capacity (> 200 at the resolution of 1), high sensitivity (sub-ppb), and rapid analysis capability (~ 30min) was designed and made in-house for on-site analysis of patients' breath. A total of 85 breath samples from 48 ARDS patients and controls were collected. Ninety-seven elution peaks were separated and detected in 13min. An algorithm based on machine learning, principal component analysis (PCA), and linear discriminant analysis (LDA) was developed. As compared to the adjudications done by physicians based on the Berlin criteria, our device and algorithm achieved an overall accuracy of 87.1% with 94.1% positive predictive value and 82.4% negative predictive value. The high overall accuracy and high positive predicative value suggest that the breath analysis method can accurately diagnose ARDS. The ability to continuously and non-invasively monitor exhaled breath for early diagnosis, disease trajectory tracking, and outcome prediction monitoring of ARDS may have a significant impact on changing practice and improving patient outcomes. Graphical abstract.

Online Comprehensive High pH Reversed Phase × Low pH Reversed Phase Approach for Two-Dimensional Separations of Intact Proteins in Top-Down Proteomics.

A proof-of-concept study is presented on the use of comprehensive two-dimensional liquid chromatography mass spectrometry (LC × LC-MS) for the separation of intact protein mixtures using a different mobile phase pH in each dimension. This system utilizes mass spectrometry (MS) friendly pH modifiers for the online coupling of high pH reversed phase liquid chromatography (HPH-RPLC) in the first dimension (1D) followed by low pH reversed phase liquid chromatography (LPH-RPLC) in the second dimension (2D). Owing to the ionic nature of proteins, the use of a different mobile phase pH was successful to provide altered selectivity between the two dimensions, even for closely related protein variants, such as bovine cytochrome c and equine cytochrome c, which differ by only three amino acids. Subminute gradient separation of proteins in the second dimension was successful to minimize analysis time, while maintaining high peak capacity. Unlike peptides, the elution order of studied proteins did not follow their isoelectric points, where acidic proteins would be expected to be more retained at low pH (and basic proteins at high pH). The steep elution isotherms (on-off retention mechanism) of proteins and the very steep gradients utilized in the second-dimension column succeeded in overcoming pH and organic solvent content mismatch. The utility of the system was demonstrated with a mixture of protein standards and an Escherichia coli protein mixture.

Rapid Screening of Complex Matrices: Utilizing Kendrick Mass Defect To Enhance Knowledge-Based Group Type Evaluation of Multidimensional Gas Chromatography-High-Resolution Time-of-Flight Mass Spectrometry Data.

Organic compound characterization of highly complex matrices involves scientific challenges, such as the diversity of "true" unknowns, the concentration ranges of various compound classes, and limited available amounts of sample. Therefore, discovery-based multidimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC×GC-HRToFMS) is increasingly applied. Nevertheless, most studies focus on target analysis and tend to disregard important details of the sample composition. The increased peak or separation capacity of GC×GC-ToFMS allows for in-depth chemical analysis of the molecular composition. However, high amounts of data, containing several thousands of compounds per experiment, are generally acquired during such analyses. Coupling GC×GC to high-resolution mass spectrometry further increases the amount of data and therefore requires advanced data reduction and mining techniques. Commonly, the main approach for the evaluation of GC×GC-HRToFMS data sets either focuses on the chromatographic separation (e.g., group type analysis), or utilizes exact mass data applying Kendrick mass defect analysis or van Krevelen plots. The presented approach integrates the accurate mass data and the chromatographic information by combining Kendrick mass defect information and knowledge-based rules. This combination allows for fast, visual data screening as well as quantitative estimation of the sample's composition. Moreover, the resulting sample classification significantly reduces the number of variables, allowing distinct chemometric analysis in nontargeted studies, such as detailed hydrocarbon analyses and environmental and forensic investigations.

Online comprehensive hydrophilic interaction chromatography × reversed phase liquid chromatography coupled to mass spectrometry for in depth peptidomic profile of microalgae gastro-intestinal digests

In this study, a comprehensive hydrophilic interaction chromatography × reversed phase coupled to high resolution mass spectrometry was developed for the peptide profile of microalgae formulations subjected to gastro-intestinal digestion. A BEH Amide column was employed in the first dimension, while a BIOshell ES-C18 Peptide in the second. As modulation interface, two trapping columns, in house packed with 1.9 μm fully porous monodisperse C18 particles characterized by high retention and efficiency, were tested and compared with SecurityGuard C18 cartridges, together with a dilution flow, to reduce first dimension mobile phase strength. The platform was coupled to both diode array detector and Orbitrap mass spectrometry. The developed setup provided high peak capacity (nc: 957) in only 60 min and a good orthogonality (A0: 0.70). The employment of the custom made C18 traps resulted in improved sensitivity (signal enhancement = 4) and a higher number of peptides detected (+58) especially of short lenght (≤ 6 aminoacids), with respect to the setup based on the security guard C18 traps. 184 phycocyanin-derived peptides were detected in Klamath and Spirulina gastro-intestinal digests, whose sequence and protein origin has been elucidated in detail by mass spectrometry. The results show the potential of the developed HILIC × RP-MS platform for in depth peptide mapping of microalgae and its possible application to highlight the products of gastro-intestinal digestion of other microalgae species.

Experimentally Validating Open Tubular Liquid Chromatography for a Peak Capacity of 2000 in 3 h.

The advancements in life science research mandate effective tools capable of analyzing large numbers of samples with low quantities and high complexities. As an essential analytical tool for this research, liquid chromatography (LC) encounters an ever-increasing demand for enhanced resolving power, accelerated analysis speed, and reduced limit of detection. Although theoretical studies have indicated that open tubular (OT) columns can produce superior resolving power under comparable elution pressures and analysis times, ultrahigh-resolution and ultrahigh-speed open tubular liquid chromatography (OTLC) separations have never been reported. Here we present experimental results to demonstrate the predicted potential of this technique. We use a 2 μm i.d. × 75 cm long OT column coated with trimethoxy(octadecyl)silane for separating pepsin/trypsin digested E. coli lysates and routinely produce exceptionally high peak capacities (e.g., 1900-2000 in 3-5 h). We reduce the column length to 2.7 cm and exhibit the capability of OTLC for ultrafast separations. Under an elution pressure of 227.5 bar, we complete the separation of six amino acids in ∼800 ms and resolve these compounds within ∼400 ms. In addition, we show that OTLC has low attomole limits of detection (LOD) and each separation requires samples of only a few picoliters. Importantly, no ultrahigh elution pressures are required. With the ultrahigh resolution, ultrahigh speed, low LOD, and low sample volume requirement, OTLC can potentially be a powerful tool for biotech research, especially single cell analysis.

Development of an At-Column Dilution Modulator for Flexible and Precise Control of Dilution Factors to Overcome Mobile Phase Incompatibility in Comprehensive Two-Dimensional Liquid Chromatography.

With the combination of different mechanisms, two-dimensional liquid chromatography has brought revolutionary changes compared to the traditional one-dimensional separation, which dramatically improve the peak capacity in separation and meet the ever-increasing demand for the analysis of complex samples in different research fields, such as chemistry, medicine, etc. However, the incompatibilities between two columns due to the transport of the large sample volume and the solvent effect always limit the wide use of two-dimensional liquid chromatography. In order to resolve this problem an at-column dilution (ACD) modulator was established to overcome the solvent incompatibility in the orthogonal combination within the comprehensive two-dimensional liquid chromatography. This interface is modified from normal two-dimensional interfaces by an additional transfer pump, which realize the at-column dilution without a flow split during the transportation. Moreover, with the control of the transfer flow and the second-dimensional gradient flow, it is able to precisely regulate the at-column dilution factor and conveniently optimize the separation conditions in both dimensions. In this work, a systematic research has been done between the setups with/without the at-column interface in the combination of reversed-phase liquid chromatography and hydrophilic interaction chromatography (RPLC × HILIC) and HILIC × RPLC, which proved that the at-column interface is able to resolve the solvent conflict problem very well. Furthermore, red ginseng was chosen as a real sample to investigate the applicability of the at-column dilution modulator for comprehensive two-dimensional chromatography with high orthogonality.

Predicted Economic Efficiency of Combining NPPS with an Autonomous Hydrogen Energy Complex

Currently, the Unified Energy System of Russia has a tendency to increase the deficit of peak and semi-peak capacities with a simultaneous increase in the number of NPP which requires the participation of NPPs in a variable part of the schedule electrical loads. In addition to the economic need to maintain the installed capacity utilization rate at a high level, there are technological limitations for maneuvering characteristics for NPPs. The authors have developed an approach to solving this problem based on combining with an environmentally friendly energy source – an autonomous hydrogen complex which includes heat accumulators and an additional multifunctional low-power steam turbine installation. The developed power complex can also provide reliable redundancy of power supply of NPP own needs in the event of a total station blackout. The paper carries out the evaluation of the technical and economic parameters of the main equipment of the autonomous hydrogen complex required for combination with a two-unit NPP with a VVER-1000. Based on the assessment of inflation indicators of the Russian economy over the past 11 years, three options have been identified for fuel cost and tariff rates for electricity (capacity), as well as the size of operating costs, including depreciation in the main equipment, taking into account current pricing principles. As a result, the values of accumulated net present value were obtained depending on the ratio of the cost of semi-peak and non-peak electricity tariffs at different inflation rates. We have taken into account the positive economic effect of reducing the risk of damage to the reactor core, replacing the construction of gas turbines as a maneuverable source of electricity in the power system, and increasing the income of the federal budget of the Russian Federation from saving natural gas. The economic conditions of competitiveness of the proposed approach to improving the maneuverability and safety of NPP are determined. The highest economic efficiency is achieved with the maximum projected inflation which is associated with the maximum discount rate and high rate of growth of electricity tariffs. Reducing the risk of damage to the core allows us to provide the competitiveness of the proposed approach in all considered variants of inflation and the ratio of electricity tariffs.

Shear performance of reinforced concrete beams incorporating stiff slender elements

The present work investigates the shear performance of concrete beams reinforced longitudinally with steel rebars incorporating randomly distributed stiff elements known as “needles”. Compared to commonly used fibers, needles function differently in concrete members that carry increasing internal stresses. To measure the effect of needles on the mechanical performance of concrete, 32 longitudinally reinforced concrete (RC) beams and 96 non-reinforced concrete prisms were tested. Among numerous possibilities, the dimensions of the needles used in the present study were selected based on a number of practical considerations. The results showed that the needles increased the peak and residual shear capacity of the reinforced beams significantly. However, the improvements were not greater than those achieved by using the same volumetric content of fibers made of the same material as that the needles were produced from. Based on the measured results and the observation of cracking patterns, guidance for optimizing the geometry of needles and test specimens are provided for future research.

Pre-radiotherapy daily exercise training in non-small cell lung cancer: A feasibility study.

To examine the feasibility of an individual, supervised, structured moderate-to-high intensity cycle ergometer exercise training immediately before radiotherapy in patients undergoing concomitant chemoradiotherapy for locally advanced non-small cell lung cancer (NSCLC). Lung cancer is the most common form of cancer. Despite significant advancements in therapy and supportive care it is still the leading cause of cancer-related death worldwide. Randomized controlled study design; patients with NSCLC receiving concomitant chemoradiotherapy were recruited and randomly assigned to either the exercise (EXE) or the control (CON) group. Exercise training consisted of 20min moderate-to-high intensity aerobic interval training 5 times per week (Mon-Fri) prior to radiotherapy. Secondary outcomes were assessed at baseline and after 7 weeks: peak oxygen consumption (VO2peak), functional capacity (6MWD), pulmonary function (FEV1), psychosocial parameters (quality of life (FACT-L), anxiety and depression (HADS)) and cancer-related side effects (reported daily). Fifteen patients were included. All patients completed a baseline test, while 13 patients were eligible for a posttest. The recruiting rate was 44.1% and the overall attendance rate to exercise was 90.0% with an adherence rate to full exercise participation of 88.1%. No adverse events or any unexpected reactions were observed during the exercise sessions. No significant differences were observed within or between groups from baseline to post intervention in any of the secondary outcomes. This study demonstrated 'proof of principle' that daily moderate-to-high intensity cycle ergometer exercise was feasible, safe and well tolerated among newly diagnosed patients with locally advanced NSCLC undergoing concomitant chemoradiotherapy. Larger randomized controlled trials are warranted.

A high-efficiency strategy integrating offline two-dimensional separation and data post-processing with dereplication: Characterization of bufadienolides in Venenum Bufonis as a case study

Comprehensive analysis and identification of chemical components are very important to evaluate the efficacy and safety of traditional Chinese medicine (TCM). Meanwhile, the discovery of new natural compounds is of great significance for drug exploitation and development. Although two-dimensional liquid chromatography (2D LC) systems expand the peak capacity and improve selectivity and resolution, interpreting the post-processing data is tedious and time-consuming. In this study, an off-line two-dimensional liquid chromatography/ultra-high performance supercritical fluid chromatography tandem quadrupole time-of-flight mass spectrometry (2D LC/UHPSFC-Q-TOF/MS) system was established for systematic chromatographic separation and identification of bufadienolides. Subsequently, the Global Natural Product Social Molecular Networking (GNPS) was applied for dereplication of chemical components of adjacent fractions with high efficiency and accuracy. The key parameters which affected separation and detection with respect to chromatographic conditions and mass spectrometry conditions were optimized. The extract of Venenum Bufonis was fractionated into forty fractions by first-dimensional reversed phase high-performance liquid chromatography (HPLC), which were further analyzed by the second-dimensional UHPSFC-Q-TOF/MS in positive ion mode. The data of forty fractions was imported into GNPS and processed automatically within about five hours. Furthermore, the chemical components with similar featured fragments were classified into the same cluster, which was helpful for components identification. A total of 229 bufadienolides were characterized and two subclasses of compounds (bufogenins conjugated with carboxylic acid and N-heterocyclic bufogenins) were found in Venenum Bufonis for the first time. In addition, UHPSFC exhibited powerful separation ability of isomers in Venenum Bufonis. In this analysis, two new compounds were isolated and fully characterized by NMR verifying the feasibility of this combined analytical strategy. This integrated strategy can improve the efficiency in the detection of new compounds and offer greater observation of isomers from medicinal herbs and other natural sources.

New generation of sequential injection chromatography: Great enhancement of capabilities of separation using flow analysis

Since its inception, sequential injection chromatography (SIC) has evolved through several stages. Key moments including introduction of the novel technique combining sequential injection analysis and monolithic column, the first generation of commercial SIC system employing robust pump, the utilization of columns packed with fused-core particles, the on-line hyphenation of extraction and separation steps in SIC, are now followed by the second generation of commercial SIC system employing stainless steel syringe pump and parts optimized for chromatographic separation. The key developments always mean acceleration of the evolution by opening new avenues and reduction of compromises in automated analytical methods based on the flow analysis. The updates, new features, and prospects of the novel instrument are described and discussed on perspective of the method developed for extraction and separation of selected phenolic acids (gallic, protocatechuic, caffeic, p-coumaric and ferulic). The method hyphenates miniaturized on-line solid phase extraction using strong anion exchange sorbent in commercial cartridge for HPLC (20 × 1 mm) and liquid chromatography using chromatographic column (C18 50 × 4.6 mm, 5 μm particles) packed with fused-core particles in the SIC manifold. The separation in gradient mode used acetonitrile: aqueous formic acid pH 2.0 mobile phase and spectrophotometric detection at 270, 300, and 320 nm. Injected sample volumes were 200 and 500 μL. The performance of the extraction step was characterized by the recovery 94.0–107.8%, enrichment factors about 20 or 50, and the separation by peak capacities 13–34, peak symmetries 1.17–1.64, and resolutions 0.82–3.75). While using a sample volume of 200 μL, our method was characterized by the following validation parameters: LODs of 0.0075–0.03 mg L−1, LOQs of 0.025–0.10 mg L−1, calibration ranges 0.025–2.50 mg L−1 (r > 0.999), repeatability of signal at 0.50 mg L−1of RSD ≤ 1.46% (n = 6), and overall time of analysis 7.1 min. The results including pilot analysis of white and red wines demonstrated the capability of novel SIC instrument to enable fast, selective, and sensitive analysis.

The Development and Validation of a Functional Capacity Test for Dancers

A peak functional capacity test that is incremental in nature, varying in intensity, and includes movements familiar to dancers is a necessary and important addition to the dance specific fitness tests in the current literature. PURPOSE: To design and validate a peak functional capacity test that is appropriate in time, intensity, and movement specificity to the dancer. METHODS: The Seifert Assessment of Functional Capacity for Dancers (SAFD) was developed using previous valid and reliable functional capacity protocols, published research in dance specific fitness tests, and consult with content experts. Final test parameters included 3 min. stages of increasing intensity utilizing both speed and difficultly of movements, continued until exhaustion. Following pilot testing, a survey of content experts supported the validity of the SAFD. Female dancers (N = 13) completed a total of four separate sessions, a familiarization trial of the SAFD, SAFD trial 1, a peak treadmill test, and SAFD trial 2. Each test measured time to exhaustion, peak oxygen consumption (VO2peak), respiratory exchange ratio (RER), heart rate (HR), blood lactate (BLa-), and rate of perceived exertion (RPE). Tests were terminated upon volitional exhaustion or a total of three cues regarding poor movement quality or inability to keep pace with the metronome. Interclass Correlation Coefficients were used to assess reliability, while validity was analyzed using Pearson Product Moment Correlations. RESULTS: Strong correlations (≥.7) were found between time to exhaustion, VO2peak, HR and RPE between SAFD trials. No significant (p > .05) differences existed in any of the physiological variables between the SAFD trials. Significant (p < .05) relationships were found between time to exhaustion, VO2peak, HR, BLa-, and RPE between the SAFD and the treadmill test. CONCLUSION: The strength of key physiological correlations of time to exhaustion, VO2peak, HR, and RPE provide strong evidence for the SAFD being both reliable and valid. Although the threshold value for correlation was not met in neither RER nor BLa-, results do present a particularly meaningful set of values to the physiology practitioner and thus, further support the conclusion that the SAFD is both a reliable and valid method of assessing peak functional capacity in the dance population.

Biventricular contractility during exercise in adults with small, unrepaired atrial septal defects.

Adult patients with a small, unrepaired atrial septal defect (ASD) have higher mortality and increased risk of several comorbidities compared to general population. Further, reduced submaximal and peak exercise capacity was recently demonstrated in these patients. The mechanisms behind these findings remain unexplained and, therefore, biventricular contractility during exercise was assessed by evaluating the force-frequency relationship in the same group of patients. Adults patients with a small, unrepaired ASD and healthy age- and gender-matched controls were examined using echocardiography during supine bicycle exercise. Continuous tissue velocity Doppler was used to evaluate isovolumetric acceleration (IVA) and systolic velocities during an incremental workload protocol. All data were analyzed post hoc in a blinded fashion. We included 30 patients previously diagnosed with a small, unrepaired ASD (mean age 35years, 63% female) and 25 controls (mean age 34years, 64% female). Patients had similar values of IVA and systolic velocities at rest when compared with the healthy controls. Further, no differences in IVA was found at peak heart rate for neither the left ventricle (90±39 vs 129±68cm/s2 , P=0.1547) nor the right ventricle (128±56 vs 154±56cm/s2 , 0.5691). There were no correlations between peak velocities and the lower exercise capacity previously reported in these patients. Adult patients with a small, unrepaired ASD have normal biventricular contractility at rest and during exercise when compared with healthy peers. Consequently, the pathophysiological mechanisms behind the impaired exercise capacity previously demonstrated in these patients remains unknown and will be a target for future work.

Development of Ultrafast Separations Using Negative Pulse Partial Modulation To Enable New Directions in Gas Chromatography.

Partial modulation via a pulse flow valve operated in the negative pulse mode is developed for high-speed one-dimensional gas chromatography (1D-GC), comprehensive two-dimensional (2D) gas chromatography (GC × GC), and comprehensive three-dimensional gas chromatography (GC3). The pulse flow valve readily provides very short modulation periods, PM, demonstrated herein at 100, 200, and 300 ms, and holds significant promise to increase the scope and applicability of GC instrumentation. The negative pulse mode creates an extremely narrow, local analyte concentration pulse. The reproducibility of the negative pulse mode is validated in a 1D-GC mode, where a pseudosteady-state analyte stream is modulated, and 8 analytes are baseline resolved (resolution, Rs ≥ 1.5) in a 200 ms window, providing a peak capacity, nc, of 14 at unit resolution ( Rs = 1.0). Additionally, the pulse width, pw, of the pulse flow valve "injection" relationship to peak width-at-base, wb, resolution between peaks and detection sensitivity are studied. To demonstrate the applicability to GC × GC, a high-speed separation of a 20-component test mixture of similar, volatile analytes is shown. Analytes were separated on the second-dimension column, 2D, with 2 wb ranging from 7 to 12 ms, providing an exceptional 2D peak capacity, 2 nc, of ∼12 using a modulation period ( PM) of 100 ms. Next, a 12 min separation of a diesel sample using a PM of 300 ms is presented. The 1 wb is ∼4 s, resulting in a 1 nc of ∼180, and 2 wb is ∼18 ms, resulting in a 2 nc of ∼17, thus achieving a nc,2D of ∼3000 in this rapid GC × GC diesel separation. Finally, GC3 with time-of-flight mass spectrometry (TOFMS) detection using a PM of 100 ms applied between the 2D and 3D columns is reported. Narrow third dimension, 3D, peaks with 3 wb of ∼15 ms were obtained, resulting in a GC3 peak capacity, nc,3D, of ∼35 000 in a 45 min separation.

Recent Advances on Drug Analyses Using Ultra Performance Liquid Chromatographic Techniques and their Application to the Biological Samples

Introduction: Ultra-Performance Liquid Chromatographic (UPLC) method enables analyst to establish an analysis at higher pressure than High Performance Liquid Chromatographic (HPLC) method towards liquid chromatographic methods. UPLC method provides the opportunity to study a higher pressure compared to HPLC, and therefore smaller column in terms of particle size and internal diameter are generally used in drug analysis. The UPLC method has attracted gradually due to its advantages such as short analysis time, the small amount of waste reagents and the significant savings in the cost of their destruction process. In this review, the recent selected studies related to the UPLC method and its method validation are summarized. The drug analyses and the results of the studies which were investigated by UPLC method, with certain parameters from literature are presented. Background: Quantitative determination of drug active substances by High-Performance Liquid Chromatography (HPLC) from Liquid Chromatography (LC) methods has been carried out since the 1970's with the use of standard analytical LC methods. In today's conditions, rapid and very fast even ultra-fast, flow rates are achieved compared to conventional HPLC due to shortening analysis times, increasing method efficiency and resolution, reducing sample volume (and hence injection volume), reducing waste mobile phase. Using smaller particles, the speed and peak capacity are expanding to new limit and this technology is named as Ultra Performance Liquid Chromatography. In recent years, as a general trend in liquid chromatography, ultra-performance liquid chromatography has taken the place of HPLC methods. The time of analysis was for several minutes, now with a total analysis time of around 1-2 minutes. The benefits of transferring HPLC to UPLC are much better understood when considering the thousands of analyzes performed for each active substance, in order to reduce the cost of analytical laboratories where relevant analysis of drug active substances are performed without lowering the cost of research and development activities. Methods: The German Chemist Friedrich Ferdinand Runge, proposed the use of reactive impregnated filter paper for the identification of dyestuffs in 1855 and at that time the first chromatographic method in which a liquid mobile phase was used, was reviewed. Christian Friedrich Chönbein, who reported that the substances were dragged at different speeds in the filter paper due to capillary effect, was followed by the Russian botanist Mikhail S. Tswet, who planted studies on color pigment in 1906. Tswet observes the color separations of many plant pigments, such as chlorophyll and xanthophyll when he passes the plant pigment extract isolated from plant through the powder CaCO3 that he filled in the glass column. This method based on color separation gives the name of "chromatographie" chromatography by using the words "chroma" meaning "Latin" and "graphein" meaning writing. Results and Conclusion: Because the UPLC method can be run smoothly at higher pressures than the HPLC method, it offers the possibility of analyzing using much smaller column sizes and column diameters. Moreover, UPLC method has advantages, such as short analysis time, the small amount of waste reagents and the significant savings in the cost of their destruction process. The use of the UPLC method especially analyses in biological samples such as human plasma, brain sample, rat plasma, etc. increasingly time-consuming due to the fact that the analysis time is very short compared to the HPLC, because of the small amount of waste analytes and the considerable savings in their cost.

Study on the combined operation of a hydro-thermal-wind hybrid power system based on hydro-wind power compensating principles

The high randomness, intermittency and uncontrollability of wind power make large-scale wind power generation present large challenges for integration into a power grid. In this paper, the principles of hydro-wind compensating operation are explored, aiming at improving the power quality of wind power and promoting the integration of wind power into the power grid. Based on the principles of hydro-wind compensating operation, the calculation method of the hydropower compensation capacity for wind power is derived. Then, an optimizing operation model of a hydro-thermal-wind hybrid power system based on the hydro-wind power compensating principle is proposed to minimize the carbon dioxide emissions and obtain optimal operation scheduling of the hybrid power system by taking advantage of hydro-wind compensation and the peak regulation capacity of hydropower. In this model, the baseload and nonbaseload output emission rates are adopted to estimate the carbon dioxide emissions of different power output processes and the emission reduction benefits. Moreover, three scenarios of the operation mode are proposed to demonstrate the applicability of the hydro-wind power compensating principle in practice. The Northwest Power Grid in China is selected as a case study to verify the effectiveness of the proposed model compared to historical operating data. The results indicate that the hydro-wind power compensating principle plays a crucial role in hydro-thermal-wind combined optimal operation. Additionally, the proposed model can improve the wind power generation and reduce the carbon dioxide emissions of the power grid. In particular, the carbon dioxide emissions can be reduced by approximately 1696*104 t each year in the Northwest Power Grid. This study provides an approach to schedule optimal operation plans for power grids with large-scale wind power and provides a valuable reference for the large-scale utilization of other kinds of renewable energy worldwide.