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Capillary Electrophoresis Sensitivity Enhancement Based on Adaptive Moving Average Method
Abstract
In the present work we demonstrate the novel approach to improve the sensitivity of the “out of lab” portable capillary electrophoretic measurements. Nowadays, many enhancement methods are: (i) underused (non-optimal), (ii) overused (distorts the data), or (iii) inapplicable in field-portable instrumentation due to lack of computational power. Described innovative migration velocity-adaptive moving average method uses optimal averaging window size and can be easily implemented with microcontroller. The contactless conductivity detection was used as a model for the development of a signal processing method and the demonstration of its impact on the sensitivity. The frequency characteristics of the recorded electropherograms and peaks were clarified. Higher electrophoretic mobility analytes exhibit higher frequency peaks, while lower electrophoretic mobility analytes exhibit lower frequency peaks. Based on obtained data, a migration velocity-adaptive moving average algorithm was created, adapted and programmed into capillary electrophoresis data processing software. Employing the developed algorithm, each data point is processed depending on a certain migration time of the analyte. Because of the implemented migration velocity-adaptive moving average method the signal-to-noise ratio improved up to 11 times for sampling frequency of 4.6 Hz and up to 22 times for sampling frequency of 25 Hz. This paper could potentially be used as a methodological guideline for the development of new smoothing algorithms that require adaptive conditions in capillary electrophoresis, and other separation methods.
... 39,40 Sensitivity enhancement and baseline compensation algorithms were used. 19,41 Volatiles. We placed 9 cm 2 lter paper into a Petri dish in a box. ...
... 7,13 C4D detector signal was enhanced improving sensitivity several-fold using an adaptive moving average algorithm. 41 The full analytical cycle is composed of the following steps: (i) collection of the sample using a vacuum of À20 kPa applied to the sample vial for 480 s ( Fig. 2a and ESI Video S2 †), (ii) washing of separation capillary for 120 s from the BGE vial using vacuum applied to waste reservoir (Fig. 2b), (iii) washing of separation capillary for 60 s from the BGE reservoir bottle using pressure applied to BGE reservoir (Fig. 2c), (iv) injection of a sample using a vacuum of À20 kPa applied to waste reservoir for 10 s (Fig. 2b) and (V) separation using +4.0 kV voltage potential. ...
... † As described in previously published works, an equation indicated in method validation guidelines has been used for calculation of limits of quantication (ESI eqn (S1) †). [39][40][41] This suggests that all investigated substances can be separated, detected and quantied at concentration levels of micromolar concentrations: (i) K + 0.0006 mM, (ii) Ca 2+ 0.0002 mM, (iii) Na + 0.0003 mM, (iv) NH 4 + 0.0006 mM, (v) DEA 0.0003 mM, (vi) TEA 0.0002 mM, (vii) BSA 0.00001 mM, (viii) formic acid 0.0017 mM, (ix) acetic acid 0.0007 mM. Phosphonic acids were quantied at 0.0400 mM concentrations, as smaller levels were impossible to quantify at such conditions. ...
Hazardous remote places exist in the world. Why should health or life be risked sending a scientist to the investigation site, as the remote analytical instrumentation exists? Different scientific fields require instruments that could be used on-site (in situ), therefore the purpose of this work was to design a fully automated chemical analysis system small enough to be mountable on a drone. Here we show an autonomous analytical system with sampling capability on a drone. The system is suited for the remote and autonomous analysis of volatile and non-volatile chemicals in the air. The designed system weighs less than 800 g. Data are transmitted wirelessly. Collected substances are separated automatically without the intervention of the operator using the method of capillary zone electrophoresis. The analytes are detected using a miniaturized contactless conductivity detector quantifying them down to less than 1 μM. In this work, we demonstrated sampling and separation of volatile amines (triethylamine and diethylamine) and organic acids (acetic and formic acids), non-volatile inorganic cations (K⁺, Ca²⁺, Na⁺), and protein (bovine serum albumin) in the aerosol state. It was shown that the capillary electrophoretic analysis can be performed on a hovering drone. We anticipate our work to be a starting point for more sophisticated, autonomous complex sample analysis. We believe that our designed instrument will enable the investigation of hazardous places in different research fields.
... However, the defect of low CE sensitivity frequently creates unexpected detection challenges [23]. Many researchers have conducted in-depth research to improve the detection sensitivity of CE [24,25]. Wu et al. [26] used a large-volume sample stack to perform capillary an online enrichment of tetracycline antibiotics, which greatly improved the sensitivity of CE, and the detection limit reached 10 ppb. ...
A metal–organic framework UiO‐66 was prepared and used as a sorbent for dispersive solid‐phase extraction combined with high‐performance liquid chromatography (DSPE‐HPLC) for extracting and determining four pyrethroids in water samples for the first time. The as‐synthesized material was confirmed by Fourier transform infrared spectroscopy (FT‐IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and N 2 adsorption–desorption analysis. In addition, several important parameters affecting DSPE efficiency, including sorbent dosage, extraction time, salt concentration, pH, elution solvent, elution volume, and elution time, were optimized. Under the optimum conditions, the UiO‐66 based on the DSPE‐HPLC method displayed a wide linear range (10–1000 ng/ml), low limits of detection (2.8–3.5 ng/ml), and good precision (relative standard deviations [RSDs] < 3%) for the four pyrethroids. The recoveries at different spiked levels ranged from 89.3% to 107.7%. In addition, UiO‐66 featured good reusability and reproducibility. The results demonstrated that π–π stacking interactions, hydrophobic interactions, and van der Waals forces between UiO‐66 and the four pyrethroids played a crucial role in the adsorption process. Meanwhile, the maximum extraction capability could be obtained within 5 min. Thus, the DSPE coupled with the UiO‐66 sorbent can be successfully used in the analysis of four pyrethroids in environmental water samples.
Practitioner Points
Simultaneous determination of four pyrethroids using the developed UiO‐66‐based DSPE‐HPLC method in water samples.
The developed method had a short enrichment time, broad linear ranges, a low detection limit, and high enrichment factor.
It is showed that π–π stacking interaction, hydrophobic interaction, and van der Waals forces were the main mechanism.
... However, the defect of low CE sensitivity frequently creates unexpected detection challenges [23]. Many researchers have conducted in-depth research to improve the detection sensitivity of CE [24,25]. Wu et al. [26] used a large-volume sample stack to perform capillary an online enrichment of tetracycline antibiotics, which greatly improved the sensitivity of CE, and the detection limit reached 10 ppb. ...
For a long time, the detection of nitroimidazole antibiotics (NIABs) has been a research focus in environmental analytical chemistry. In this work, a novel technique for the analysis of nitroimidazoles was established based on capillary electrophoresis (CE). UiO‐66, synthesized using a solvothermal method, was utilized as an adsorbent in the dispersive solid‐phase extraction (DSPE) of five different NIABs. The separation and detection of NIABs in environmental water samples were accomplished using the CE diode array detection method. The optimal extraction conditions were obtained after systematically studying the effects of adsorption time, amount of extractant, and elution solvent on extraction efficiency. According to the results of the study, the LODs of the five NIABs were between 16 and 97 ng/mL, the RSDs were between 0.32% and 0.55%, and the spike recoveries were between 87.43% and 108.9%. This study presents a novel technique for measuring NIABs in complex water samples. This article is protected by copyright. All rights reserved
... If IACE were to be incorporated in sample preparation prior to sample introduction into the capillary or microchip, the entire system could be automated, reduce analysis time, and overcome limitations in poor detection sensitivity. We will emphasize the advantages for the determination of proteoforms when compared with other methods described to enhance the analytical sensitivity of analytes, such as field-amplified sample stacking, large-volume sample stacking, pH-mediated stacking, isotachophoreris (ITP), stacking techniques in micellar electrokinetic chromatography (MEKC), soli-phase extraction, and tagging target analytes with various chromophores and detecting the derivatized substances with sensitive detectors [123,151,152,[173][174][175][176][177][178][179][180][181][182][183][184][185][186][187][188][189][190]. In some instances, IACE can be used in combination with other methods to enhance analytical sensitivity even further. ...
Over the years, multiple biomarkers have been used to aid in disease screening, diagnosis, prognosis, and response to therapy. As of late, protein biomarkers are gaining strength in their role for early disease diagnosis and prognosis in part due to the advancements in identification and characterization of a distinct functional pool of proteins known as proteoforms. Proteoforms are defined as all of the different molecular forms of a protein derived from a single gene caused by genetic variations, alternative spliced RNA transcripts and post-translational modifications. Monitoring the structural changes of each proteoform of a particular protein is essential to elucidate the complex molecular mechanisms that guide the course of disease. Clinical proteomics therefore holds the potential to offer further insight into disease pathology, progression, and prevention. Nevertheless, more technologically advanced diagnostic methods are needed to improve the reliability and clinical applicability of proteomics in preventive medicine. In this manuscript, we review the use of immunoaffinity capillary electrophoresis (IACE) as an emerging powerful diagnostic tool to isolate, separate, detect and characterize proteoform biomarkers obtained from liquid biopsy. IACE is an affinity capture-separation technology capable of isolating, concentrating and analyzing a wide range of biomarkers present in biological fluids. Isolation and concentration of target analytes is accomplished through binding to one or more biorecognition affinity ligands immobilized to a solid support, while separation and analysis are achieved by high-resolution capillary electrophoresis (CE) coupled to one or more detectors. IACE has the potential to generate rapid results with significant accuracy, leading to reliability and reproducibility in diagnosing and monitoring disease. Additionally, IACE has the capability of monitoring the efficacy of therapeutic agents by quantifying companion and complementary protein biomarkers. With advancements in telemedicine and artificial intelligence, the implementation of proteoform biomarker detection and analysis may significantly improve our capacity to identify medical conditions early and intervene in ways that improve health outcomes for individuals and populations.
Capillary electrophoresis (CE) is a powerful technique continuously expanding into new application fields. One of these applications involves the study of enzymes, their catalytic activities and the alteration of this activity by specific ligands. In this review, two model enzymes, lipases and kinases, will be used since they differ substantially in their modes of action, reaction requirements and applications making them perfect subjects to demonstrate the advantages and limitations of CE-based enzymatic assays. Indeed, the ability to run CE in various operation modes and hyphenation to different detectors is essential for lipase-based studies. Additionally, the low sample consumption provided by CE promotes it as a promising technique to assay human and viral nucleoside kinases. Undeniably, these are rarely commercially available enzymes and must be frequently produced in the laboratory, a process which requires special sets of skills. CE-based lipase and kinase reactions can be performed outside the capillary (pre-capillary) where the reactants are mixed in a vial prior to their separation or, inside the capillary (in-capillary) where the reactants are mixed before the electrophoretic analysis. These enzyme-based applications of CE will be compared to those of liquid chromatography-based applications in terms of advantages and limitations. Binding assays based on affinity CE and the compelling microscale thermophoresis (MST) will be briefly presented as they allow a broad understanding of the molecular mechanism behind ligand binding and of the resulting modulation in activity.
The developments of analytical contactless conductivity measurements based on capacitive coupling over the two years from mid-2018 to mid-2020 are covered. This mostly concerns applications of the technique in zone electrophoresis employing conventional capillaries and to a lesser extent lab-on-chip devices. However, its use for the detection in several other flow-based analytical methods has also been reported. Detection of bubbles and measurements of flow rates in two-phase flows are also recurring themes. A few new applications in stagnant aqueous samples, e.g. endpoint detection in titrations and measurement on paper-based devices, have been reported. Some variations of the design of the measuring cells and their read-out electronics have also been described.
The development of the instrument which will significantly ease the in situ samplings of volatile compounds is described. The purpose of this work was to design an automated, portable, handheld sample collection device that operates with monolithic adsorbents. The sampler contains two lithium-ion batteries, collects samples into micro-liter range volume vials, is supplied with a changeable 100 µm inner diameter six cm long capillary with an in-tube monolithic solid-phase micro-extraction adsorbent. Modeling experiments with triethylamine and diethylamine demonstrated that instrument captured samples containing volatile substances in the range of 3.5 to 118 ppm concentration levels in the air. The substances have been analyzed using a dedicated capillary electrophoresis contactless conductivity detection system and determined amounts of volatile substances in the sample solutions ranged between 3.4 and 1010 µM. Only 0.44 mL of air was enough to adsorb substances on the adsorbent, collecting them into 50 µL of water and achieving a preconcentration effect. The developed instrument is expected to find it’s applications where sampled air or gas volume is in µL – mL range: (a) collection of volatile substances near single plant parts in vivo, (b) collection of beetle pheromones in vivo, (c) volume-restricted machinery and other related applications.
Since the advent of X-Ray fluorescence (XRF) spectrum analysis technology, with its wide range of elemental analysis, rapid, nondestructive analysis characteristics, and better detection accuracy, the workload of semi-quantitative analysis has taken half of the total analysis in contemporary research institutes and university laboratories engaged in material research. In addition, XRF has been widely and efficiently used in analytical chemistry, geological and mineral survey, ecological and environmental monitoring, food and drug detection, archeology and other fields. XRF spectrum processing technology is based on the application of mathematical principles, using reasonable algorithms to optimize the processing of spectrum data to contribute more accurate quantitative analysis of key elements. Over the years, XRF spectrum processing technology has formed a relatively complete set of processes, in each step of spectrum processing, plenty of research work and paper reports have been implemented and developed. This paper mainly reviews the representative algorithms and their progress in spectrum smoothing, background subtraction and overlapping peak decomposition of XRF spectrum analysis technology, analyzes their applications in related fields, summarizes and proposes the development direction of some potential algorithms.
The methodology described in this paper will significantly reduce the time required for understanding the relations between chromatographic data and bio-activity assays. The methodology is a hybrid of hypothesis based and data-driven scientific approaches. In this work, a novel chromatographic data segmentation method is proposed, which demonstrates the capability of finding what volatile substances are responsible for antiviral and cytotoxic effects in the medicinal plant extracts. Up to now the full potential of the separation methods has not been exploited in the life sciences. This was due to the lack of data ordering methods capable to adequately preparing the chromatographic information. Furthermore, the data analysis methods suffer of multidimensionality requiring a large number of investigated data points. A new method is described for processing any chromatographic information into a vector. The obtained vectors of highly complex and different origin samples can be compared mathematically. The proposed method, efficient with relatively small sized datasets, does not suffer of multidimensionality. In this novel analytical approach, the samples did not need fractionation and purification, what is typically used in hypothesis based scientific research. All investigations were performed using crude extracts possessing hundreds of phyto-substances. The antiviral properties of medicinal plant extracts were investigated using gas chromatography-mass spectrometry, antiviral tests and proposed data analysis method. The findings suggested that: (i) beta-cis-caryophyllene, linalool, eucalyptol possess antiviral activity, while (ii) thujone does not, and (iii) alpha-, beta-thujones, cis-p-menthan-3-one, estragole show cytotoxic effects.
Determination of natural preservatives using electrophoretic, or chromatographic techniques in fermented milk products is a complex task due to the following reasons: (i) the concentrations of the analytes can be below the detection limits, (ii) complex matrix and comigrating / coeluting compounds in the sample can interfere with the analytes of the interest, (iii) low recovery of the analytes and (iv) complex sample preparation is necessary. The aim of this study was to apply capillary zone electrophoresis coupled with contactless conductivity detection for the separation and determination of nisin in fermented milk products. In this work, separation and determination of natural preservative – nisin in fermented milk products is described. Optimized conditions using capillary zone electrophoresis coupled with capacitance‐to‐digital technology based contactless conductivity detector and data conditioning, which filters the noise of the electropherogram adaptively to the peak migration time allowed precise, accurate, sensitive (limit of quantification: 0.02 μg/ml) and most importantly – requiring very minute sample preparation, determination of nisin. Sample preparation includes following steps: (i) extraction / dilution and (ii) centrifugation. The method was applied for determination of nisin in real samples, i.e. fermented milk products. The values of different nisin forms were ranging from 0.056 ± 0.003 μg/ml to 9.307 ± 0.437 μg/g.
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One of the main problems of the remote complex sample analysis instrumentation is that such systems are susceptible to temperature fluctuations. Temperature regulation is energetically ineffective, and it is not used in most of the field portable analytical systems. Separations performed in a changing temperature environment provide electropherograms with considerable baseline fluctuations, resulting in significant errors in detection and integration of the peaks. This paper describes electropherogram baseline compensation that is suitable for the capillary electrophoresis ‐ contactless conductivity detection analytical method. The baseline compensation utilizes linear or polynomial data processing methods, and can be programmed in‐line using simple microcontroller, or on‐line and off‐line in data acquisition software. This method is targeted for field portable and autonomous analytical systems that are utilized in a fluctuating environment.
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The miniaturization and optimization of a white rot fungal bioremediation experiment is described in this paper. The optimized procedure allows determination of the degradation kinetics of anthracene. The miniaturized procedure requires only 2.5 ml of culture medium. The experiment is more precise, robust, and better controlled comparing it to classical tests in flasks. Using this technique, different parts, i.e., the culture medium, the fungi, and the cotton seal, can be analyzed. A simple sample preparation speeds up the analytical process. Experiments performed show degradation of anthracene up to approximately 60 % by Irpex lacteus and up to approximately 40 % by Pleurotus ostreatus in 25 days. Bioremediation of anthracene by the consortium of I. lacteus and P. ostreatus shows the biodegradation of anthracene up to approximately 56 % in 23 days. At the end of the experiment, the surface tension of culture medium decreased comparing it to the blank, indicating generation of surfactant compounds.
Decaffeinated coffee accounts for 10 percent of coffee sales in the world; it is preferred by consumers that do not wish or are sensitive to caffeine effects. This article presents an analytical comparison of capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) methods for residual caffeine quantification in decaffeinated coffee in terms of validation parameters, costs, analysis time, composition and treatment of the residues generated, and caffeine quantification in 20 commercial samples. Both methods showed suitable validation parameters. Caffeine content did not differ statistically in the two different methods of analysis. The main advantage of the high performance liquid chromatography (HPLC) method was the 42-fold lower detection limit. Nevertheless, the capillary electrophoresis (CE) detection limit was 115-fold lower than the allowable limit by the Brazilian law. The capillary electrophoresis (CE) analyses were 30% faster, the reagent costs were 76.5-fold, and the volume of the residues generated was 33-fold lower. Therefore, the capillary electrophoresis (CE) method proved to be a valuable analytical tool for this type of analysis.
Recently, various approaches have been addressed to improve chromatographic performance in terms of sensitivity or selectivity, from the development of novel on-line (or off-line) enrichment methodologies, to the improvement of stationary-phase type and multi-dimensional chromatography, to novel and more performing detectors such as tandem mass spectrometry (MS/MS), Nuclear Magnetic Resonance (NMR), and Infrared Spectrometry (IR). For the analysis of complex matrices (e.g., biological fluids, plant extracts, food, and environmental samples), coupling chromatographic instrumentation with these detectors provides a powerful analytical device that can be applied in many fields, such as analysis of pharmaceutical and natural products (and medicinal plant), quality control, environmental trace analysis.This review describes major advances in the HPLC field in terms of enrichment techniques, chromatographic separation and especially in terms of detector improvement for a complete identification and quantification of targeted analytes. The possibility of high-throughputs analyses, as a consequence of sensitivity and selectivity enhancement in drug and metabolites profile and multi-residue assays for natural compounds and/or products containing natural species, is also highlighted. Finally, it is shown how multivariate analysis may enhance analytical performance in terms of useful analytical information that can be extracted from experimental data and in terms of methods for exploring and modelling data. Chemometrics provides tools for making the most of analytical signal, once selectivity and sensitivity have been improved from the chemical point of view.
Basic operation principles of a lightweight, low power, low cost, portable ion chromatograph utilizing open tubular ion chromatography in capillary columns coated with multi-layer polymeric stationary phases are demonstrated. A minimalistic configuration of a portable IC instrument was developed that does not require any chromatographic eluent delivery system, nor sample injection device as it uses gravity-based eluent flow and hydrodynamic sample injection adopted from capillary electrophoresis. As a detection device, an inexpensive commercially available capacitance sensor is used that has been shown to be a suitable substitute for contactless conductivity detection in capillary separation systems. The built-in temperature sensor allows for baseline drift correction typically encountered in conductivity/capacitance measurements without thermostating device. The whole instrument does not require any power supply for its operation, except the detection and data acquisition part that is provided by a USB port of a Netbook computer. It is extremely lightweight, its total weight including the Netbook computer is less than 2.5 kg and it can be continuously operated for more than 8 h. Several parameters of the instrument, such as detection cell design, eluent delivery systems and data treatment were optimized as well as the composition of eluent for non-suppressed ion chromatographic analysis of common inorganic cations (Na+, NH4+, K+, Cs+, Ca2+, Mg2+, transition metals). Low conductivity eluents based on weakly complexing organic acids such as tartaric, oxalic or pyridine-2,6-dicarboxylic acids were used with contactless capacitance detection for simultaneous separation of mono- and divalent cations. Separation of Na+ and NH4+ cations was optimized by addition of 18-crown-6 to the eluent. The best separation of 6 metal cations commonly present in various environmental samples was accomplished in less than 30 min using a 1.75 mM pyridine-2,6-dicarboxylic acid and 3 mM 18-crown-6 eluent with excellent repeatability (below 2%) and detection limits in the low micromolar range. The analysis of field samples is demonstrated; the concentrations of common inorganic cations in river water, mineral water and snow samples were determined.
An equation analogous to the Van Deemter equation in chromatography is developed to account for peak broadening in capillary zone electrophoresis (CZE). This equation applies to conditions wher the peaks are symmetrical (sample zone concentration much less than background electrolyte concentration). To identify and to quantitate the effects of different contributions to the peak width in CZE, it is first necessary to put all peak profiles on the same footing by correcting them for the velocities fo different zones and for the finite length of the detector zone compared to the sample zone. Three major contributors to the peak width are identified: (1) the injection length of the sample; (2) longtudinal diffusion that takes place during the migration time between injection and detection; and (3) analyte-wall interactions. Temperature is shown not to be a major factor in peak broadening under typical experimental conditions. The predictions of our model agree well with experimentally determined peak profiles for different analytes under a variety of conditions. New expressions for theoretical plate number and resolution in CZE are presented. It is concluded that in almost all previously reported CZE separations the peak profiles were dominated by the sample injection length. This explains why the observed peak widths in CZE have been broader than anticipated.
Today, data evaluation has become a bottleneck in chromatographic science. Analytical instruments equipped with automated samplers yield large amounts of measurement data, which needs to be verified and analyzed. Since nearly every GC/MS instrument vendor offers its own data format and software tools, the consequences are problems with data exchange and a lack of comparability between the analytical results. To challenge this situation a number of either commercial or non-profit software applications have been developed. These applications provide functionalities to import and analyze several data formats but have shortcomings in terms of the transparency of the implemented analytical algorithms and/or are restricted to a specific computer platform.
This work describes a native approach to handle chromatographic data files. The approach can be extended in its functionality such as facilities to detect baselines, to detect, integrate and identify peaks and to compare mass spectra, as well as the ability to internationalize the application. Additionally, filters can be applied on the chromatographic data to enhance its quality, for example to remove background and noise. Extended operations like do, undo and redo are supported.
OpenChrom is a software application to edit and analyze mass spectrometric chromatographic data. It is extensible in many different ways, depending on the demands of the users or the analytical procedures and algorithms. It offers a customizable graphical user interface. The software is independent of the operating system, due to the fact that the Rich Client Platform is written in Java. OpenChrom is released under the Eclipse Public License 1.0 (EPL). There are no license constraints regarding extensions. They can be published using open source as well as proprietary licenses. OpenChrom is available free of charge at http://www.openchrom.net.
The Environmental Protection Act has created a growing need for
the measurement and assessment of trace emissions to the environment. This encompasses three main areas of ground, water and the atmosphere. The need to achieve lower emissions has placed a large burden on analytical techniques, particularly in the areas of trace analysis to ppb and ppt levels. Chromatographic techniques are widely used for assessment and measurement of emissions in all three areas. Enhanced detectors using mass spectrometry principles are available to lower detection limits, but these are expensive. Standard chromatography detectors can be used for trace analysis,
but this often leads to extensive sample preparation stages to achieve low detection limits. This paper describes the techniques developed by Thomas Swan & Company to introduce a cost effective way of lowering detection limits. The approach taken
meets both BATNEEC and BPEO constraints.
One of the main problems of the remote complex sample analysis instrumentation is that such systems are susceptible to temperature fluctuations. Temperature regulation is energetically ineffective, and it is not used in most of the field portable analytical systems. Separations performed in a changing temperature environment provide electropherograms with considerable baseline fluctuations, resulting in significant errors in detection and integration of the peaks. This paper describes electropherogram baseline compensation that is suitable for the capillary electrophoresis ‐ contactless conductivity detection analytical method. The baseline compensation utilizes linear or polynomial data processing methods, and can be programmed in‐line using simple microcontroller, or on‐line and off‐line in data acquisition software. This method is targeted for field portable and autonomous analytical systems that are utilized in a fluctuating environment.
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Because capillary electrophoresis (CE) is driving the automation of manual and semi-manual techniques, conserves precious samples, and minimizes the use of hazardous organic chemicals, it constitutes a powerful new methodology for the clinical laboratory. In Clinical and Forensic Applications of Capillary Electrophoresis, John R. Petersen and Amin A. Mohammad, along with a panel of leading basic and clinical investigators, review those CE methods that are now replacing many routine serum and blood tests in clinical and forensic laboratories. Major areas reviewed include the coating of columns; the analysis of serum, urine, and CSF proteins and paraproteins; abnormal hemoglobins and hemoglobin Alc; peptides, amino and organic acids; therapeutic drugs; drugs of abuse; viral load; and short tandem repeats (STR). The methods discussed include capillary zone, micellar, electrokinetic, capillary gel, and nonaqueous electrophoresis. The authors show how a variety of detection methods (UV-visible, fluorescence, and MS) can be used in conjunction with CE to detect a broad array of analytes, ranging from serum proteins to PCR products to drugs of forensic importance.
Innovative and highly practical, Clinical and Forensic Applications of Capillary Electrophoresis demonstrates the power and versatility of CE-not only to develop new assays, but also to markedly simplify today's clinical and forensic laboratory methodology.
The development of capacitively coupled contactless conductivity detection for the two-year period from mid-2014 to mid-2016 is covered in this review. This includes a survey of fundamental studies and further developments of the measuring technique reported as well as a discussion of new applications. These mostly concern capillary electrophoresis carried out in conventional capillaries as well as on microchip electrophoresis devices. The main focus is on determination of small non-UV-absorbing organic ions and inorganic ions in different types of samples of clinical, nutritional or environmental interest. Outside of electrophoresis contactless conductivity detection is finding uses in detection in column chromatography, flow-injection analysis and industrial applications. This article is protected by copyright. All rights reserved
Capillary electrophoresis with Laser-Induced Fluorescence (CE-LIF) detection is being applied to new analytical problems which challenge both the power of CE separation and the sensitivity of LIF detection. On-capillary LIF detection is much more practical than post-capillary detection in a sheath-flow cell. Therefore, commercial CE instruments utilize solely on-capillary CE-LIF detection with a Limit of Detection (LOD) in the nM range, while there are multiple applications of CE-LIF that require pM or lower LODs. This tutorial analyzes all aspects of on-capillary LIF detection in CE in an attempt to identify means for improving LOD of CE-LIF with on-capillary detection. We consider principles of signal enhancement and noise reduction, as well as relevant areas of fluorophore photochemistry and fluorescent microscopy.
Capillary electrophoresis (CE) is a special case of using an electrical field to separate the components of a mixture. Electrophoresis in a capillary is differentiated from other forms of electrophoresis in that it is carried out within the confines of a narrow tube. To understand the behavior of molecules under the influence of an electrical field inside a capillary it is essential to understand the phenomena that result from the geometry of a capillary.
We present here a critical review covering conventional analytical tools of recombinant drug analysis and discuss their evolution towards miniaturized systems foreseeing a possible unique recombinant drug-on-a-chip device. Recombinant protein drugs and/or pro-drug analysis require sensitive and reproducible analytical techniques for quality control to ensure safety and efficacy of drugs according to regulatory agencies. The versatility of miniaturized systems combined with their low-cost could become a major trend in recombinant drugs and bioprocess analysis. Miniaturized systems are capable of performing conventional analytical and proteomic tasks, allowing for interfaces with other powerful techniques, such as mass spectrometry. Microdevices can be applied during the different stages of recombinant drug processing, such as gene isolation, DNA amplification, cell culture, protein expression, protein separation, and analysis. In addition, organs-on-chips have appeared as a viable alternative to testing biodrug pharmacokinetics and pharmacodynamics, demonstrating the capabilities of the miniaturized systems. The integration of individual established microfluidic operations and analytical tools in a single device is a challenge to be overcome to achieve a unique recombinant drug-on-a-chip device.
With increasingly efficient columns, eluite peaks are increasingly narrower. To take full advantage of this, choice of the detector response time and the data acquisition rate a.k.a. detector sampling frequency, have become increasingly important. In this work, we revisit the concept of data sampling from the theorem variously attributed to Whittaker, Nyquist, Kotelnikov, and Shannon. Focusing on time scales relevant to the current practice of high performance liquid chromatography (HPLC) and optical absorbance detection (the most commonly used method), even for very narrow simulated peaks Fourier transformation shows that theoretical minimum sampling frequency is still relatively low (<10 Hz). However, this consideration alone may not be adequate for real chromatograms when an appreciable amount of noise is present. Further, depending on the instrument, the manufacturer's choice of a particular data bunching/integration/response time condition may be integrally coupled to the sampling frequency. In any case, the exact nature of signal filtration often occurs in a manner neither transparent to nor controllable by the user. Using fast chromatography on a state-of-the-art column (38,000 plates), we evaluate the responses produced by different present generation instruments, each with their unique black box digital filters. We show that the common wisdom of sampling 20 points per peak can be inadequate for high efficiency columns and that the sampling frequency and response choices do affect the peak shape. If the sampling frequency is too low or response time is too large, the observed peak shapes will not remain as narrow as they really are – this is especially true for high efficiency and high speed separations. It is shown that both sampling frequency and digital filtering affect the retention time, noise amplitude, peak shape and width in a complex fashion. We show how a square-wave driven light emitting diode source can reveal the nature of the embedded filter. We discuss time uncertainties related to the choice of sampling frequency. Finally, we suggest steps to obtain optimum results from a given system.
In this work lab-made poly(dimethylsiloxane) (PDMS) microfluidic chips were matched to a capacitively coupled contactless conductivity detector (C(4) D) having external in-plane electrodes (eDAQ, Australia). The advantages of this type of C(4) D are the choice to reversibly place or remove the microchip onto/from the detector and to freely variate the position of the detection (separation length) on the microchip. The thickness of the bottom layer of the PDMS chip was optimized to achieve sensitive detection during the electrophoretic separation. PDMS chips with 100 μm bottom layer used with the C(4) D platform were tested by CZE of a mixture of seven anions and different types of real samples. Using split-flow pressure sample injection and effective length of 6.5 cm, the numbers of theoretical plates were in the range of 4 000-6 000 (63 000/m - 93 000/m) and the LODs amounted to 3.66 μmol/L-14.7 μmol/L (0.13-2.26 μg/mL) for the studied anions. This article is protected by copyright. All rights reserved.
In this work, the concept of a field-portable analyzer is proposed that operates with milliliter amounts of solvents and samples. The need to develop such an analyzer is not only driven by specific extraterrestrial analysis but also, for example, by forensics applications where the amount of liquid that can be taken to the field is severely limited. The prototype of the proposed analyzer consists of a solid-liquid extractor, the output of which is connected to the micropump, which delivers droplets of extracts to digital microfluidic platform (DMFP). In this way, world-to-chip interfacing is established. Further, the sample droplets are transported to CE capillary inlet port, separated and detected via a contactless conductivity detector. Working buffers and other solvents needed to perform CE analysis are also delivered as droplets to the DMFP and transported through the CE capillary. The performance of the analyzer is demonstrated by analysis of amino acids in sand matrices. The recovery of the spiked amino acids from the inert sand sample was from 34 to 51% with analysis LOD from 0.2 to 0.6 ppm and migration time RSD from 0.2 to 6.0%.
The purpose of this article is to underline the miniaturized LC instrumental system and describe the evolution of commercially available systems by discussing their advantages and drawbacks. Nowadays, there are already many miniaturized LC systems available with a great variety of pump design, interface and detectors as well as efficient columns technologies and reduced connections devices. The solvent delivery systems are able to drive the mobile phase without flow splitters and promote gradient elution using either dual piston reciprocating or syringe-type pumps. The mass spectrometry as detection system is the most widely used detection system; among many alternative ionization sources direct-EI LC–MS is a promising alternative to APCI. In addition, capillary columns are now available showing many possibilities of stationary phases, inner diameters and hardware materials. This review provides a discussion about miniaturized LC demonstrating fundamentals and instrumentals' aspects of the commercially available miniaturized LC instrumental system mainly nano and micro LC formats. This review also covers the recent developments and trends in instrumentation, capillary and nano columns, and several applications of this very important and promising field.
Over the last four decades, liquid chromatography (LC) has experienced an evolution to smaller columns and particles, new stationary phases and low-flow-rate instrumentation. However, the development of person-portable LC has not followed, mainly due to difficulties encountered in miniaturizing pumps and detectors, and in reducing solvent consumption. The recent introduction of small, non-splitting pumping systems and UV-absorption detectors for use with capillary columns has finally provided miniaturized instrumentation suitable for high-performance hand-portable LC. Fully-integrated microfabricated LC still remains a significant challenge. Ion chromatography (IC) is amenable to miniaturization as detection is simple and it does not require high-pressure pumps; however, applications are mostly limited to inorganic and small organic ions. This review covers advancements that make portable LC instruments possible today.
Concern about the environment is increasing and so is the search for analytical methods that make continuous monitoring possible. Microfluidic devices such as lab-on-a-chip emerge as an alternative to the laboratory-based conventional techniques, making possible the development of unmanned monitoring tools. This review covers the last five years on the application of autonomous microfluidic devices for continuous environmental monitoring and addresses the existing demands in this field.
In attempting to analyze, on digital computers, data from basically continuous physical experiments, numerical methods of performing familiar operations must be developed. The operations of differentiation and filtering are especially important both as an end in themselves, and as a prelude to further treatment of the data. Numerical counterparts of analog devices that perform these operations, such as RC filters, are often considered. However, the method of least squares may be used without additional computational complexity and with considerable improvement in the information obtained. The least squares calculations may be carried out in the computer by convolution of the data points with properly chosen sets of integers. These sets of integers and their normalizing factors are described and their use is illustrated in spectroscopic applications. The computer programs required are relatively simple. Two examples are presented as subroutines in the FORTRAN language.
We describe an open tubular ion chromatograph (OTIC) that uses anion exchange latex coated 5 μm radius silica and 9.8 μm radius poly(methyl methacrylate) tubes and automated time/pressure based hydrodynamic injection for pL-nL scale injections. It is routinely possible to generate 50 000 plates or more (up to 150 000 plates/m, columns between 0.3 and 0.8 m have been used), and as such, fast separations are possible, comparable to or in some cases better than the current practice of IC. With an optimized admittance detector, nonsuppressed detection permits LODs of submicromolar to double digit micromolar for a variety of analytes. However, large volume injections are possible and can significantly improve on this. A variety of eluents, the use of organic modifiers, and variations of eluent pH can be used to tailor a given separation. The approach is discussed in the context of extraterrestrial exploration, especially Mars, where the existence of large amounts of perchlorate in the soil needs to be confirmed. These columns can survive drying and freezing, and small footprint, low power consumption, and simplicity make OTIC a good candidate for such a mission.
Separation science in harsh environments emerges as a new exciting field of research.•Emphasis should be put on a holistic approach for portable and in situ CE instrumentation design.•Influence of extreme temperatures on separation instruments/protocols have been understood, as well as ways of tackling extreme temperatures.•Gaps in the literature point out that attention to the influence of shock/vibration and extreme ambient pressures on instrument performance is required.•In general, the methods of dealing with the shocks and vibrations are known theoretically but it is not well known how those measures block the vibration and shock influence in reality.
The capacitance-to-digital single chip detector was upgraded. The paper discusses hardware issues and benefits of the designed/ upgraded detector. The device can be operated from rechargeable lithium-ion battery as stand-alone, portable system and is capable of transmitting real-time data wirelessly. The detector and additional modules (battery, battery holder, microcontroller board, wireless module) weight is less than 85 g. Electrophoretic separation in low conductivity 20 mm MES/ L-His buffer, pH 6.1, was performed in order to evaluate detection parameters. The system is capable of quantification of potassium ions down to 0.31 μM. Investigation of differential signal acquisition configuration showed improved performance regarding external noise and temperature fluctuations. The system can be a solution for stand-alone, field-portable capillary format separation detector.This article is protected by copyright. All rights reserved
Contenido: 1. Eventos y sus probabilidades. 2. Variables aleatorias y sus distribuciones. 3. Variables aleatorias discretas. 4. Variables aleatorias continuas. 5. Generar funciones y sus aplicaciones. 6. Cadenas de Markov. 7. Convergencia y variables aleatorias. 8. Procesos aleatorios. 9. Procesos estacionarios. 10. Renovaciones. 11. Filas. 12. Martingalas y 13. Procedimientos de difusión.
A capacitance-to-digital converter integrated circuit was implemented in an automated capillary electrophoresis device as a single chip detector. In this paper, design and hardware issues related to the fabrication and application of a miniature detector for contactless measurement of complex impedance are discussed. The capacitance-to-digital converter integrated circuit was used as the whole detector. The advantage of this setup is that the single integrated circuit provides digital data and neither additional signal conditioning nor analog-to-digital converter is required. Different separation conditions were used to evaluate the detection characteristics of the constructed detection unit. A 1 μM limit of detection for sodium and a 1.6 μM limit of detection for potassium ions were revealed for the detector. The detection system designed is competitive with miniaturized contactless conductivity detectors or UV absorbance detectors with respect to overall parameters (sensitivity, resolution, power consumption properties and size). The obtained separation and detection results show that such detection technique can be used as an extremely low power consuming and space saving solution for capillary electrophoresis detection with potential applications in environmental monitoring, process control and various analytical measurements. This article is protected by copyright. All rights reserved
Tokamak experiment requires high-speed data acquisition and processing systems. In traditional data acquisition system, the sampling rate, channel numbers and processing speed are limited by bus throughput and CPU speed. This paper presents a data acquisition and processing system based on FPGA. The data can be processed in real-time before it is passed to the CPU. It provides processing ability for more channels with higher sampling rates than the traditional data acquisition system while ensuring deterministic real-time performance. A working prototype is developed for the newly built polarimeter–interferometer diagnostic system on the Joint Texas Experimental Tokamak (J-TEXT). It provides 16 channels with 120 MHz maximum sampling rate and 16 bit resolution. The onboard FPGA is able to calculate the plasma electron density and Faraday rotation angel. A RAID 5 storage device is adopted providing 700 MB/s read–write speed to buffer the data to the hard disk continuously for better performance.
Sm- and d#ferentlatkn of large data sets by plecewlse least-squares polynomlal fffllng are now wklely used tech- nlques. The calculation speed Is very greatly enhanced H a convolution formalism is used to perform the calcuiatlons. Prevlously tables of convolution weights for the center-pdnt least-squares evaluatlon of 2m + 1 points have been pres- ented. A major drawback of the technique Is that the end polnts of the data sets are kot (2m pohts for a 2m + 1 point fllter). Convdutlon weights have also been presented In the speclal case of Inltlai-point values. In this paper a sknple general procedure for calculatlng the convolution weights at all podtlons, for all polynomial orders, all fitter lengths, and any derlvatlve Is presented. The method, based on the re- cursive properties of Gram polynomials, enables the convo- lutlon technique to be extended to cover all points In the spectrum.
Micro total analysis (μTAS), also called "lab-on-a-chip (LOC)" technology, promises solutions for high throughput and highly specific analysis for chemistry, biology and medicine, while consuming only tiny amounts of samples, reactants and space. This article reports selected contributions of LOC, which represent clear practical approaches for routine work, or presenting potentiality to be transferred to routine analytical laboratories. Taking into account the present LOC state-of-the-art, we identify various reasons for its scarce implementation in routine analytical laboratories despite its high analytical potential, as well as the probably main "niche" for successfully practical developments is suggested.
The operation of advanced chromatographic systems, namely comprehensive two-dimensional (2D) chromatography coupled to multidimensional detectors, allows achieving a great deal of data that need special care to be processed in order to characterize and quantify as much as possible the analytes under study. The aim of this review is to identify the main trends, research needs and gaps on the techniques for data processing of multidimensional data sets obtained from comprehensive 2D chromatography. The following topics have been identified as the most promising for new developments in the near future: data acquisition and handling, peak detection and quantification, measurement of overlapping of 2D peaks, and data analysis software for 2D chromatography. The rational supporting most of the data processing techniques is based on the generalization of one-dimensional (1D) chromatography although algorithms, such as the inverted watershed algorithm, use the 2D chromatographic data as such. However, for processing more complex N-way data there is a need for using more sophisticated techniques. Apart from using other concepts from 1D chromatography, which have not been tested for 2D chromatography, there is still room for new improvements and developments in algorithms and software for dealing with 2D comprehensive chromatographic data.
Single-molecule spectroscopy and detection are powerful techniques for the study of single fluorescent particles and their interaction with their environment. We present a low-cost system for simultaneous real-time acquisition, storage of inter-photon arrival times and the calculation and display of the fluorescence time trace, autocorrelation function and distribution of delays histogram for single-molecule experiments. From a hardware perspective, in addition to a multi-core computer, only a standard low-cost counting board is required as processing is software-based. Software is written in a parallel programming environment with time crucial operations coded in ANSI-C. Crucial to system performance is a simple and efficient real-time autocorrelation algorithm (acf) optimized for the count rates (approximately 10(4) cps) encountered in single-molecule experiments. The algorithm's time complexity is independent of temporal resolution, which is maintained at all time delays. The system and algorithm's performance was validated by duplicating the signal from the photon detector and sending it to both the ordinary counter board and a commercial correlator simultaneously. The data acquisition system's robustness under typical single-molecule experimental conditions was tested by observing the diffusion of Rhodamine 6G molecules in deionized water.
Contactless conductivity detection is universal for CE in that all charged species can be quantified, and it is particularly attractive for those inorganic and organic ions that are not directly accessible by optical means. It is not necessary to make precise alignments or to create an optical window into the capillary. Commercial detectors that can be retrofitted to existing instruments are available at a cost that is lower than that of any other electrophoresis detector. The approach is also suited for lab-on-chip devices. It is attempted in this review to summarize some of the expertise accumulated since the introduction of the axial contactless conductivity detector to CE 10 years ago.
Capillary electrophoresis (CE) is a useful method to quantify drugs in biological fluids. However, especially for blood or plasma samples, the sensitivity is not sufficient to quantify drugs and their metabolites as they often need to be quantified in the lower microg/L range. To overcome this limitation and to increase the sensitivity, two strategies are applied: first, to increase the amount of analyte added to the capillary and, second, to increase the sensitivity on the detector site. To improve the sensitivity on the detector site, alternative detection techniques to UV detection, e.g., laser-induced fluorescence detection (LIF) or mass spectroscopy (MS), can be applied. However, LIF detection can only be used for fluorescent analytes and the current equipment for CE-MS coupling provides only small improvements in sensitivity compared to UV detection. The detection window for UV detection can be enhanced using capillaries with an extended light path (bubble cell) or Z-shaped capillaries. Sensitivity improvements up to a factor of 10 have been reported. Increasing the amount of analyte in the capillary can be done either by chromatographic or by electrokinetic methods. Chromatographic methods such as on-capillary membrane preconcentration have been used for several analytes. However, no validated application has been reported to date. In contrast, several validated examples can be found in which electrokinetic techniques like sample stacking have been applied to achieve limits of quantification in the lower microg/L range. In conclusion, to date, electrokinetic techniques such as field-amplified sample injection offer the most promising results in achieving a sufficient sensitivity to quantify drugs in biological fluids.
The first step in the separation of adenine nucleotides from different types of tissues or cells is deproteinization. Several sample preparation methods successfully used for a number of tissues or cells failed to work with erythrocytes. Use of strong acids or bases for deproteinization resulted in a low yield due to the hydrolysis of adenine nucleotides. Moreover, the neutralization of these acids or bases increased the ionic strength, resulting in broad and overlapping peaks. In neutral salt precipitation methods, saturated salts caused clogging of the capillaries. A new deproteinization procedure method was developed. The samples were deproteinized by heating of erythrocytes in boiling distilled water at 95 degrees C for 5 min. The denatured proteins were removed by centrifugation and membrane filtration. The adenine nucleotides were then separated using a polyacrylamide coated capillary. Depending on the type, diameter, length of the capillary and the voltage applied, an average of 16.50 min was sufficient for the separation of adenine nucleotides. All adenine nucleotides were clearly resolved and gave very sharp peaks. The amount of each adenine nucleotide was calculated from the areas under the peaks and AEC values were calculated using the integrator software. The AEC value of 0.91+/-0.04 (n=10) obtained for healthy persons was in good agreement with the literature value of 0.85-0.95. These reported method for sample preparation and capillary electrophoresis is simple, fast and inexpensive compared to the previously reported sample preparation, HPLC and enzymatic methods for the determination of AEC.
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