ELECTROPHORESIS最新文献

A novel DC-dielectrophoresis (DEP) method employing a tunable insulating microdroplet for the continuous sorting of microtargets is presented in this article. To induce the dielectrophoretic effect, a DC electric voltage is applied via the microdroplet through the microchannel to induce the gradient of the inhomogeneous electric field. When passing through the gap between the microdroplet and the channel where there is the strongest nonuniformity of the electric field, the microparticles experience the DEP effects, and their trajectories shift. The effects of the gap spacing and the applied voltage on the distribution of the electric field gradient and the effect of the flow rate on the particle trajectory were analyzed numerically. On the basis of theoretical analysis, a tunable microdroplet-based microfluidic chip was fabricated, and the experimental system platform centered on the tunable droplet chip was constructed. Experiments were conducted to demonstrate the sorting of 5 and 10 µm polystyrene microparticles by adjusting the joint gap distance, flow rate, and applied voltage. The experimental results were in good agreement with the numerical simulation, which proved the feasibility of using microdroplet to serve as tunable insulator for the manipulation and separation of microtargets.

In this study, ion chromatography (IC) methods were developed and validated for the determination of sodium, potassium, phosphate, and sorbitol in phosphate syrup. For the analysis of cations, an IonPac CS16 column was utilized, with a mobile phase of 50 mM methanesulfonic acid and a flow rate of 0.5 mL/min. For the analysis of phosphate and sorbitol, an IonPac AS19 column was employed, using a flow rate of 1.0 mL/min and mobile phases of 50 and 20 mM NaOH, respectively. In the validation tests, sensitivity was assessed on the basis of the signal-to-noise ratio, with the limit of detection for all analytes being below 0.001 mM. The linearity curves for all analytes exhibited determination coefficients greater than 0.999, indicating excellent linearity. The relative standard deviation (RSD%) for both inter-day and intra-day precision was not more than 1%. Accuracy, expressed as recovery (%), ranged from 98% to 101% for all ions. The validation of these methods demonstrated their reliability for the measurement of these four analytes. Furthermore, the stability of the syrup was evaluated over 6 months at room temperature (25°C). The results indicated that the phosphate syrup remained stable under these conditions, with the analyte contents staying close to 100%.

Siponimod fumarate (SIP), a potent selective S1P receptor modulator, has emerged as a critical therapeutic agent in the treatment of multiple sclerosis. Recognizing the increasing regulatory demands for robust impurity profiling and method reliability, this study reports the development and optimization of an HPLC method for the simultaneous determination of SIP and its related impurities in both bulk drug substance and tablet dosage forms. The method was developed within an Analytical Quality by Design (AQbD) framework, guided by ICH Q14 principles, ensuring a systematic and risk-based approach throughout the analytical lifecycle. Chromatographic separation necessary for resolving critical impurities was achieved on an XSelect HSS T3 column (150 mm × 4.6 mm, 3.5 µm) using a stepped gradient elution program with 0.1% perchloric acid in water and acetonitrile as the mobile phases. Optimal separation conditions, identified through the AQbD process to meet stringent performance criteria, were determined at a column temperature of 42.5°C, a flow rate of 1.4 mL min⁻¹, and UV detection at 212 nm. The method performance was rigorously evaluated through accuracy profiles, confirming both its precision and trueness across the targeted concentration range. In parallel, as part of a holistic method characterization, environmental sustainability was assessed using comprehensive greenness metrics, whereas its practical applicability was further substantiated using the Blue Applicability Grade Index (BAGI) and the Red–Green–Blue 12 (RGB12) algorithms. This approach not only bridges the gap created by the absence of an official pharmacopoeial monograph for SIP but also offers a robust, well-characterized, and sustainable platform for pharmaceutical quality control, aligning method development with both regulatory performance needs and environmental awareness.

This work focuses on the separation of oligonucleotides (ONs) in a free solution by capillary electrophoresis—mass spectrometry (CE-MS). Specifically, we evaluated a combination of separation in acidic background electrolytes (BGEs), nanospray ionization, and time-of-flight mass spectrometry in positive mode. A mixture of synthetic ONs, ranging in length from 15 to 78 nt, was employed as the test compounds. The key to a good separation selectivity of ONs lies in the different protonation of individual nucleobases. To this end, we assessed the acidity constant (pK_a) of the nucleobases in nucleotides experimentally as 3.3 for adenine, 4.4 for cytosine, 2.5 for guanine, and < 2 for thymine. From a set of separations in the 2–9 pH range, it was found that optimum peak shape and resolution are achieved in the interval of acidic pH 2–2.5. The BGE can be conveniently composed of either formic acid (FA) or a combination of ammonium hydroxide and FA. Nanospray ionization provided ions with charge numbers ranging from +4 to +8, proportional to the length of the ON. For short sequences, sheath liquid (SL) comprising 0.5%–1% (v/v) FA + 20% (v/v) methanol was sufficient in order to generate ions in positive mode MS, whereas a stronger SL of 5% (v/v) FA + 20% (v/v) methanol was required for longer ON sequences of approximately > 40 nt.

Substandard and falsified medicines pose a significant public health threat, particularly in low-income countries. Ensuring pharmaceutical quality is crucial to mitigate risks associated with ineffective and harmful medications. Among others, developing and implementing robust and cost-effective analytical methods is an important and quick strategy for ensuring the quality of medicines. This study aimed to develop a robust and cost-effective capillary zone electrophoresis method with UV detection for insulin analysis in active pharmaceutical ingredient and formulations. A multilayer capillary coated with polybrene and poly(sodium 4-styrenesulfonate) improved repeatability. The method was optimized by systematically evaluating running buffer composition, pH, ionic strength, and voltage, achieving optimal separation with a 60 mM phosphate buffer at pH 8.0. It demonstrated excellent precision, accuracy, linearity, and robustness. Application of the method to insulin commercial samples verified compliance with pharmacopoeial standards. The method could be a reliable and accessible alternative for quality control of insulin in resource-limited settings, supporting efforts to combat substandard pharmaceuticals and protect public health. Moreover, the method aligns with green chemistry principles, as it eliminates the need for organic solvents, either as solvent or as a component of the running buffer.

A novel microdroplet mixer is proposed by combining the asymmetric offset structure with tunable shrink in the microfluidic chip. The mixer consists of a coaxial flow region in the dispersed-phase channel and an asymmetrical offset aggregation region in the downstream channel, which shortens the mass transfer distance between the solutions to be mixed through the “sandwich” type of initial distribution, and utilizes the tunable shrink to reduce the shear force and break the symmetric vortex during the generation of the microdroplets, prolonging the pre-mixing time. Through finite element simulation, the effects of dispersed-phase flow velocity, continuous-phase flow velocity, the relative angles and offset distances between the continuous and dispersed-phases, and the necking width and length of the tunable shrink on the mixing efficiency inside the droplets were investigated. The internal mixing inside the microdroplet decrease with the dispersed-phase flow velocity, whereas the increase of the continuous-phase flow velocity favors the mixing enhancement. By optimizing the above-mentioned effects, the mixing efficiency achieves as high as approximately 97%, demonstrating the excellent mixing inside the microdroplets in the novel asymmetric micromixer. The proposed microdroplet mixer illustrates advantages of rapid mixing, simple patterned geometry, and easy to fabricate, demonstrating a promising technique for flexibly fluid mixing inside the microdroplet on a microfluidic chip.