CE-LIF System Research Articles

Electric load prediction based on a novel combined interval forecasting system

Under the trend of the global green and low-carbon transformation, accurate prediction of electric load is an urgent problem for all countries to maintain the normal operation of production and living activities. Currently, a large number of models based on single-point forecasting of electric load have emerged. However, these models are limited by the high randomness of electric load data, which restricts the further improvement of prediction accuracy. To fill this gap, a CElif (Combined Electric Load Interval Forecasting) system is proposed in this paper, which contains decomposition and denoising module, individual forecasting module, optimization module and evaluation module, aiming to tolerate uncertainty to provide policymakers with more information. Decomposition and denoising strategy is adopted to extract and reconstruct the inherent modes of the original sequence. In order to verify the superiority of the CElif system, the electric load data of 30-minute interval in Australia are used to test. The numerical results conclude the CElif system not only has excellent coverage performance in electric load interval prediction, controls the uncertainty to a great extent, but also provides a basis for power system dispatching management.

Capillary Electrophoresis with Laser-Induced Fluorescence Detection for the Diagnosis of Phenylketonuria: A Versatile Wet or Dry Laboratory Experiment in Upper-Level Undergraduate Analytical Chemistry

Capillary electrophoresis is a powerful separation tool with a wide range of analytes for diverse applications and is compatible with various detection methods. While some more established separation techniques like gas or liquid chromatography are utilized heavily in analytical chemistry laboratory courses, newer commercial capillary electrophoresis instrumentation remains underrepresented in undergraduate laboratories, with the concepts being largely in the realm of lecture alone in analytical chemistry curricula. Despite its proven power and wide application, an undergraduate laboratory experiment utilizing capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) has yet to be published. Here, we present an experiment for third- and fourth-year undergraduate analytical chemistry courses in which the students use CE-LIF to optimize system parameters, analyze the amino acid profile of a mock “patient sample”, and use calibration standards coupled with statistical analysis to provide a phenylketonuria (PKU) diagnosis. This experiment is easily adaptable to a dry lab, making this technique available to laboratories without the resources needed to acquire a CE-LIF system. We also demonstrate that the dry lab analysis can be accomplished in an online format, requiring no student presence in the laboratory, which is especially relevant due to recent events concerning the COVID-19 pandemic.

A novel, post-column micro-membrane reactor for fluorescent analysis of protein in capillary electrophoresis

Based on the semipermeability of hollow fiber membranes, a post-column membrane reactor was developed for capillary electrophoresis (CE)-laser induced fluorescence (LIF) analysis of proteins by using a hollow fiber membrane to connect the separation and detection capillaries. The membrane length between the separation and detection capillaries was 1 mm. Driven by the chemical potential difference between the separation buffer inside the membrane and the fluorescence derivatization solution outside the membrane, the derivatization reagent can be easily drawn into hollow fiber membrane to react with proteins. Also, the separation buffer can be adjusted by the derivatization solution to match the conditions of derivatization without sample loss. The effect of the separation buffer on the derivatization reaction was investigated and the results showed that even a strong acidic solution and multiple additives can be adopted in the separation buffer without destroying the post-column derivatization of proteins. Under the optimized conditions, the highly sensitive detection of BSA was achieved with a detection limit of 3.3 nmolL(-1) and a linear calibration range from 0.007 to 0.1 mgmL(-1). The proposed CE-LIF system with a post-column membrane reactor was also successfully applied to the separation and detection of proteins in rat liver and loach muscle.

Separation and determination of B vitamins and essential amino acids in health drinks by CE‐LIF with simultaneous derivatization

An efficient and sensitive method for the separation and determination of three essential amino acids and three B vitamins by CE-LIF with a simultaneous derivatization procedure was developed. The conditions for derivatization and separation of these micronutrients were investigated. FITC was used as the reagent for fluorescence tagging of arginine (Arg), valine (Val), tryptophan (Trp), folic acid (FA), and niacinamide (NA). Riboflavin (RF) was detected without derivatization. Derivatization of analytes dissolved in borate solution was performed by successive introduction of fluorescence reagent and analytes followed by water bathing at 43°C. The molar ratio of sample/reagent (S/R), derivatization temperature, and incubation time significantly influenced the efficiency of derivatization. To maximize the fluorescence yield, a high S/R (≥20) was required. The nonderivatized RF and five derivatized analytes were separated in the optimized CE-LIF system with the application of 22 kV voltage and 25 mM borate buffer at pH 9.85. Validation of the method showed good linearity for the corrected peak areas versus standard concentrations for the six analytes. The RSDs (n = 3) of the migration time and the peak area obtained for the analytes ranged from 0.4 to 1.1% and from 1.9 to 4.4%, respectively. The developed method, with the lowest LOD of 0.5 nM, was successfully applied for the efficient derivatization and determination of B vitamins in four health drink samples.

Characterization of quantum dots using capillary zone electrophoresis

Commercially available quantum dots (QDs) were characterized using CE. The CE instruments were laboratory-built, each being capable of both electrokinetic and hydrodynamic injection. Modes of detection include UV absorption and LIF. The CE-LIF system was further modified to handle microliter sample volumes during injection. Sodium phosphate (5-25 mM, pH 7.5-11) was found to be a good buffer electrolyte. Sodium mercaptoproprionate CdTe/CdS (ADS620) QDs and carboxylic acid CdSe/ZnS (T2-Evitag) QDs yielded high separation efficiencies of N = 1.5x10(6) plates at t(M) = 10 min and N = 1.0x10(5) plates at t(M) = 3.8 min, respectively. Apparently the EDC/sulfo-NHS bioconjugation chemistry worked well with the neutral T2-Evitag QDs, but not so well with the negatively charged ADS620 QDs. This preliminary knowledge will serve as a basis for new CE immunoassay studies of QD-biomolecule conjugates and their immunocomplexes with target analytes.

Sensitive determination of erythrosine and other red food colorants using capillary electrophoresis with laser-induced fluorescence detection

Capillary electrophoresis with laser-induced fluorescence detection (CE–LIF) was applied to separation and sensitive determination of red food colorants. Diode pumped frequency-doubled Nd:YAG laser (532 nm) was used as an excitation source in a laboratory-built CE–LIF system. For highly fluorescent erythrosine B (E127), an extrapolated limit of detection (LOD) of 0.4 ng mL −1 (S/N = 3) was achieved. Extrapolated LODs of other tested red additives, such as carmoisine, E122 (0.5 μg mL −1); amaranth, E123 (0.2 μg mL −1); ponceau 4R, E124 (0.3 μg mL −1) and red 2G, E128 (0.3 μg mL −1) were about one-order lower compared to results obtained with CE with absorbance detection in UV/vis (CE–UV/vis). The main advantages of using CE–LIF for analysis of food samples are high selectivity and minimization of matrix effect. To our knowledge, this is the first use of CE–LIF for determination of red food colorants.

Trace level determination of substance P using capillary electrophoresis and laser-induced fluorescence

An analytical method was developed to determine the undecapetide substance P (SP) based on capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. SP was derivatized with the fluorogenic reagent 2,3-naphthalenedicarboxaldehyde (NDA) prior to injection into the CE-LIF system. The pre-column derivatization scheme combined with injection enhancement techniques extends the detectability of SP to the subnanomolar level. Limit of detection (LOD) of 100 pM was achieved without pre-concentrating the sample prior to injection. The reproducibility for six different preparations of a standard sample containing 5 nM of SP was 6.8% RSD and that of the CE migration time was 0.08% RSD. The method was used to determine SP in a saliva sample.

Handling and detection of 0.8 amol of a near-infrared cyanine dye by capillary electrophoresis with laser-induced fluorescence detection.

We are interested in the detection of DNA adducts and other trace analytes by labeling them with a fluorescent tag followed by use of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for high resolution and sensitivity. Towards this goal, here we report the following: (1) synthesis and handling properties of a near-IR, carboxyl-substituted heptamethine cyanine dye; (2) modification of an existing ball lens LIF detector to provide near-LIF detection with excitation at 785 nm for CE; and (3) corresponding handling and detection of as little as 0.8 amol of the dye by enrich-injection of 4.7 microl of 1 x 10(-13) mol/l dye in methanol from an 8-microl volume into a corresponding CE-LIF system. The electrolyte for the separation was methanol-40 mmol/l aqueous sodium borate (98:2, v/v). This finding encourages further exploration of the dye by functionalization of its carboxyl group for chemical labeling purposes.

Optimization of a rapid and sensitive identification system for Salmonella enteritidis by capillary electrophoresis with laser-induced fluorescence.

A system coupling capillary electrophoresis (CE) with a laser-induced fluorescence (LIF) system for the identification of Salmonella enteritidis was developed. Addition of an appropriate amount of sodium alginate and NaCl to the running buffer made it possible to obtain a reproducible sharp peak. Two fluorescent staining methods using a cell-permeable nucleic acid stain and a salmonellae-specific polyclonal antibody were adapted to the system. The CE-LIF successfully detected as few as three cells per injection from a pure culture of S. enteritidis. The CE-LIF system can be conveniently used for rapid and highly sensitive identification of S. enteritidis.

Electrophoretic profiling of both RNA and protein from a single 250-pL sample.

A novel approach is described that uses capillary electrophoresis (CE) to electrophoretically sample and separate both protein and RNA from a single injected plug of cell lysate. A 250-pL sample of lysate from Chinese hamster ovary cells (9.6 x 10(7) cells/mL) was hydrodynamically injected into a capillary containing a Tris-based aqueous buffer. This was followed by selective electrokinetic ejection of RNA from the lysate into water, yielding an effective cell concentration of RNA of 3000 cells/mL. The cellular components (e.g., proteins) retained in the capillary were separated and then detected with laser-induced fluorescence (LIF) using 275-nm excitation. The ejected/diluted sample was subsequently injected into a separate CE-LIF system, which utilized an entangled polymer sieving matrix and 543-nm excitation for the detection of ethidium bromide-labeled nucleic acids (i.e., RNA). Virtually no sample preparation is required other than simple washing and lysing of the cells isolated from culture. This combined approach can be easily modified for the detection of any analyte through adjustment of CE-HF conditions. In addition, it provides an effective method for desalting cellular RNA samples having complex matrixes, which results in improved RNA injection efficiency and a 7600-fold effective signal enhancement over total lysate injection.

Automated DNA mutation analysis by single-strand conformation polymorphism using capillary electrophoresis with laser-induced fluorescence detection.

Automation is essential for rapid genetic-based mutation analysis in clinical laboratory to screen a large number of DNA samples. We propose in this report an automatic process using Beckman Coulter P/ACE capillary electrophoresis (CE) with laser-induced fluorescence (LIF) system to detect a single-point mutation in the codon 12 of human K-ras gene. Polymerase chain reaction (PCR) using a fluorescently labeled reverse primer and a plain forward primer to specifically amplify a selected 50 bp DNA fragment in human K-ras gene. The amplified DNA is placed on the sample tray of the CE system with a pre-programmed step for single-strand conformation polymorphism (SSCP) analysis. Sample injection and denaturation processes are performed online along with separation and real-time data analysis. The concept of automation for rapid DNA mutation analysis using CE-LIF system for SSCP is presented.

ChemInform Abstract: Development of Analytical Technologies for Human Genomic DNA Using Capillary Electrophoresis and Their Applications

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Double coupling Edman chemistry for high-sensitivity automated protein sequencing.

Capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) is a promising new method for the analysis of protein sequencing products. It gives 10 zmol (1 zmol = 10(-21) mol) limits of detection (3 sigma) for fluorescein thiohydantoin (FTH) amino acids. We have developed a separation for the (FTH)-amino acid products generated from 18 of the 20 coded amino acids. The extremely low volume requirement associated with CE-LIF makes it incompatible with commercial sequencers. For this reason, we have also been developing a miniaturized sequencer that can be more easily coupled to our detection system. Both the CE-LIF system and the miniaturized sequencer are described.

Improvements in drug purity determination by capillary electrophoresis using UV-absorption and LIF-detection with a UV-laser

In drug purity determinations by capillary electrophoresis using UV-detection generally a relative high concentration of the main compound has to be injected. Principles how to handle overloading effects are described. NXX-066 is a drug with a native fluorescence which made it possible to use of CE system equipped with a LIF-detection unit. Monitoring drug purity determination with LIF detection results in an improved limit of quantification of the impurities and/or opens a possibility to avoid an overloaded main peak. A frequency doubled (FRED) argon ion laser set at 244 nm was used as excitation source in drug purity determination with the LIF-detection unit and the chemicals used were therefore carefully chosen in order to minimize the background noise level, which easily is enhanced when fluorescence detection is performed in the UV-range. The separation of the fluorescent NXX-066 analogues proved to be a difficult task, but an adequate resolution was obtained when β- and γ-cyclodextrins was added as structural selectors and the separation window was expanded by the use of a repressed/reversed electroosmotic flow. A comparison of the separation capability for the UV-detection system and the laser induced fluorescence detection system was performed, showing that the overloading effects of the main peak can be removed using the CE-LIF system and thereby obtain a substantially improved resolution of the analogues. A comparison of LC-UV and CE-UV for drug purity determination of a crude product from, synthesis of NXX-066 is also included in this paper where a good correlation of the results were obtained.

Development of analytical technologies for human genomic DNA using capillary electrophoresis and their applications

Capillary electrophoretic systems equipped with a multi-color detectable laser-induced fluorescent DNA detector (CE-LIF) were developed. We examined the efficiency and the performance of the CE-LIF systems for the high-speed DNA sequencing and DNA diagnosis for human diseases. The effect of the gel composition, electric field strength, and capillary length on the separation of DNA sequencing reaction product was investigated in order to achieve high-speed DNA sequencing for large-scale sequencing in the Human Genome Project. The CE-LIF system is successfully applied to ultrafast cDNA sequencing for human and yeast genomes. Under optimum separation conditions, only 10 min is required to sequence 300 base DNA. A polymer solution of cellulose derivative was utilized as a sieving medium for the CE-LIF system and gave excellent resolution of polymerase chain reaction (PCR) amplified polymorphic loci on the human genome. The CE-LIF system is successfully applied to the DNA diagnosis for cancers through CA repeat analysis of human D8S 1218 locus, heart diseases through VNTR (variable number of tandem repeat) analysis of human apolipoprotein B gene and Alzheimer's disease through RFLP (restriction fragment length polymorphism) analysis of human apolipoprotein E gene with high-speed and high resolution. Capillary affinity gel electrophoresis was developed as a new technique for the recognition of the specific DNA base and/or sequence. This technology is also applicable to the characterization of binding properties of DNA based drugs. The principle, the theory, and the methods of capillary affinity gel electrophoresis are presented. This technique is applied to the determination of association constants between an affinity ligand and oligonucleotides. The great potential of capillary affinity gel electrophoresis for the detection of the mutation on DNA is illustrated.

Continuous in Vivo Monitoring of Amino Acid Neurotransmitters by Microdialysis Sampling with Online Derivatization and Capillary Electrophoresis Separation

A separation-based biosensor has been developed that is capable of near-real-time analysis of aspartate and glutamate with a temporal resolution of less than 2 min in anesthetized or awake, freely moving animals. The instrument consists of a microdialysis sampling system, an on-line reactor, an injection interface, and a CE-LIF system. Primary amine analytes are derivatized with NDA/CN following microdialysis sampling using an on-line reactor to produce fluorescent CBI derivatives. The reaction takes approximately 1 min. The derivatized sample then travels to a microinjection valve which alternately sends CE running buffer and reacted microdialysis sample to the CE column via an injection interface. The interface allows a controllable volume of 10-20 nL to be injected onto the CE separation capillary. Separation of aspartate and glutamate from the other amino acids present in the microdialysis sample was achieved within 70 s. Detection limits for glutamate and aspartate using laser-induced fluorescence detection were 0.1 microM. The linear dynamic range was acceptable for the determination of aspartate and glutamate in dialysate samples where the levels are between 1 and 10 microM. Full automation of the system was achieved by computer control of the valve, the interface, and the data collection system. The performance of this system was demonstrated in an anesthetized rat by monitoring ECF levels of aspartate and glutamate released in brain after stimulation with high concentrations of K+.