Wall-jet conductivity detector for microchip capillary electrophoresis

A new end-column ‘hybrid’ contactless conductivity detector for microchip capillary electrophoresis (CE) was developed. It is based on a “hybrid” arrangement where the receiving electrode is insulated by a thin layer of insulator and placed in the bulk solution of the detection reservoir of the chip, whereas the emitting electrode is in contact with the solution eluted from the channel outlet in a wall-jet arrangement. The favorable features of the new detector including the high sensitivity and low noise, can be attributed to both the direct contact of the ‘emitting’ electrode with the analyte solution as well as to the insulation of the detection electrode from the high DC currents in the electrophoretic circuit. Such arrangement provides a 10-fold sensitivity enhancement compared to currently used on-column contactless conductivity CE microchip detector as well as low values of noise and easy operation. The new design of the wall-jet conductivity detector was tested for separation of explosive-related methylammonium, ammonium, and sodium cations. The new detector design reconsiders the wall-jet arrangement for microchip conductivity detection in scope of improved peak symmetry, simplified study of inter-electrode distance, isolation of the electrodes, position of the wall-jet electrode to the separation channel, baseline stability and low limits of detection.     

实验室智能化管理的探讨

结合智能化一卡通网络管理系统在山东省计量科学研究院实验室管理中的应用情况,研讨实验室智能化管理的相关问题,重点介绍系统结构、系统特点、系统功能和系统应用。     

Capillary electrophoresis with capacitively coupled contactless conductivity detection method development and validation for the determination of azithromycin,clarithromycin, and clindamycin

A capillary electrophoresis with capacitively coupled contactless conductivity detection based method for the assay of azithromycin, clarithromycin and clindamycin was optimized and validated in this study. A buffer solution of 20 mM 2‐(N‐morpholino) ethane sulfonic acid, 40 mM l ‐histidine and 0.6 mM cetyltrimethylammonium bromide (pH 6.39) was used for the electrophoresis. An uncoated, bare‐fused silica capillary (total length 60 cm, effective length 32 cm, 75 μm id) was used at 25°C. The sample was injected hydrodynamically at 0.5 psi for 5 s. The electrophoresis was conducted at 30 kV in reverse polarity for 6 min with 3 and 2 min of in‐between sodium hydroxide (0.1 M) and background electrolyte rinsing, respectively. Ammonium acetate was used as internal standard. This simple and robust method showed reasonable limit of detection and limit of quantitation for azithromycin (0.0125/0.03 mg/mL), clarithromycin (0.017/0.03 mg/mL), and clindamycin (0.038/0.06 mg/mL), with good selectivity, precision both intraday (relative standard deviation ≤ 1.0%) and interday (relative standard deviation < 3.7%), linearity (R ² > 0.999) and recovery (99 – 101.7%). The method was successfully applied for the determination of azithromycin, clarithromycin and clindamycin in formulations.     

Implied Open-circuit Voltage Imaging via a Single Bandpass Filter Method—Its First Application in Perovskite Solar Cells

A novel, camera-based method for direct implied open-circuit voltage (iV_OC) imaging via the use of a single bandpass filter (s-BPF) is developed for large-area photovoltaic solar cells and precursors. The photoluminescence (PL) emission is imaged using a narrow BPF with centre energy inside the high-energy tail of the PL emission, utilising the close-to-unity and nearly constant absorptivity of typical photovoltaic devices in this energy range. As a result, the exact value of the sample's absorptivity within the BPF transmission band is not required. The use of an s-BPF enables a fully contactless approach to calibrate the absolute PL photon flux for spectrally integrated detectors, including cameras. The method eliminates the need for knowledge of the imaging system spectral response. Through an appropriate choice of the BPF centre energy, a range of absorber compositions or a single absorber with different surface morphologies, such as planar and textured, can be imaged, all without the need for additional detection optics. The feasibility of this s-BPF method is first validated. The relative error in iV_OC is determined to be ≤1.5%. The method is then demonstrated on device stacks with two different perovskite compositions commonly used in single-junction and monolithic tandem solar cells.     

Determination of nerve agent degradation products by capillary electrophoresis using field-amplified sample stacking injection with the electroosmotic flow pump and contactless conductivity detection

In the present study, field-amplified sample stacking injection using the electroosmotic flow pump (FAEP) was developed for the capillary electrophoretic separation of the four nerve agent degradation products methylphosphonic acid (MPA), ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA) and cyclohexyl methylphosphonic acid (CMPA). Coupled to contactless conductivity detection, direct quantification of these non-UV active compounds could be achieved. Sensitivity enhancement of up to 500 to 750-fold could be obtained. The newly established approach was applied to the determination of the analytes in river water and aqueous extracts of soil. Detection limits of 0.5, 0.7, 1.4 and 2.7 ng/mL were obtained for MPA, EMPA, IMPA and CMPA, respectively, in river water and 0.09, 0.14, 0.44 and 0.22 μg/g, respectively, in soil.     

Study on the effects of electrolytes and solvents in the determination of quaternary ammonium ions by nonaqueous capillary electrophoresis with contactless conductivity detection

A study on the separation of lipophilic quaternary ammonium cations in NACE coupled with contactless conductivity detection (NACE‐C⁴D) is presented. The suitability of different salts dissolved in various organic solvents as running electrolytes in NACE‐C⁴D was investigated. A solvent mixture of methanol/acetonitrile at a ratio of 90%:10% v/v showed the best results. Deoxycholic acid sodium salt as BGE was found to provide exceptional high stability with low baseline noise that leads to highest S/N ratios for the target analytes among all BGEs tested. Under the optimum conditions, capillaries with different internal diameters were examined and an id of 50 μm was found to give best detection sensitivity. The proposed method was validated and showed good linearity in the range from 2.5 to 200 μM, low limits of detection (0.1–0.7 μM) and acceptable reproducibility of peak area (intraday RSD 0.1–0.7%, n = 3; interday RSD 5.9–9.4%, n = 3).     

Direct analysis of formate in human plasma,serum and whole blood by in-line coupling of microdialysis to capillary electrophoresis for rapid diagnosis of methanol poisoning

A simple method using direct injection of human blood samples and quantitative analysis of formate was developed for rapid diagnosis of methanol poisoning. A sample pretreatment device including a 500 Da molecular weight cut-off dialysis membrane was in-line coupled to capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D). 50 μL of 1:9 diluted blood samples and 50 μL of DI water were filled into the donor and the acceptor chamber, respectively, and small ionic species in blood samples were electrokinetically injected across the dialysis membrane directly into the separation capillary. Matrix components, such as red blood cells, proteins, lipids and other high molecular weight compounds, were retained by the dialysis membrane and did not interfere with subsequent CE separation. Formate was separated from other small anions in an optimized background electrolyte solution consisting of 20 mM l-histidine and 25 mM l-glutamic acid at pH 4.8. The method showed excellent analytical parameters in terms of repeatability and linearity; RSD values for migration times and peak areas at a formate concentration typical for methanol poisoning were below 0.3% and 7.4%, respectively, and linear calibration curves with correlation coefficients better than 0.999 were obtained. Limit of detection and limit of quantification were 15 and 50 μM formate in original (undiluted) blood samples, respectively. The method was applied to determination of formate in serum samples of a patient diagnosed with acute methanol poisoning.     

新型非接触充电电源磁路结构的分析与仿真

在分析非接触充电电源用变压器磁路结构的基础上,选用了一种适用于电动汽车等设备非接触充电的HH型变压器磁芯结构,并利用Ansoft Maxwell有限元磁路分析软件对此结构与EE型、ETD型等几种其他常见的变压器磁芯结构进行了对比分析,通过实验对仿真结果进行验证。结果表明,该磁芯结构实测效率为93.3%,与仿真得到的效率97.8%接近,从而验证了HH型变压器磁芯结构的可行性与优越性。     

Separation of fluoroquinolones in acidic buffer by capillary electrophoresis with contactless conductivity detection

A method to determine five fluoroquinolones (FQs), namely, rufloxacin (RUF), ciprofloxacin (CIP), enrofloxacin (ENO), gatifloxacin (GAT) and moxifloxacin (MOX), in acidic buffer by capillary electrophoresis (CE)-capacitively coupled contactless conductivity detection (C⁴D) technique is presented. Separation was carried out in a fused-silica capillary (42 cm × 50 μm) using a buffer composed of 10 mM tartaric acid, 14 mM sodium acetate and 15% (v/v) methanol at pH 3.8. The RSDs of the migration times and peak areas were 0.65% and 12.3% (intraday), 1.28% and 8.8% (interday), respectively. CE-C⁴D in combination with liquid–liquid extraction (LLE) as clean-up and preconcentration procedure, allows detection of the FQs in fortified chicken muscle samples with detection limits of 6.8–11.7 ng/g. This method shows potential in rapid determination of FQs in samples with complex matrix.     

Determination of oxalate and citrate in urine by capillary electrophoresis using solid‐phase extraction and capacitively coupled contactless conductivity based on an improved mini‐cell

A new method for the rapid determination of the metabolites oxalate and citrate in urine samples was based on capillary electrophoresis and capacitively coupled contactless conductivity detection coupled with solid‐phase extraction. The detection cell for capacitively coupled contactless conductivity detection was improved with a smaller inner volume (1.5 nL), reduced noise (0.2∼0.5 mV) and better reproducibility and durability. Under optimal conditions, oxalate and citrate can achieve baseline separation within 4 min and the detection limits (S/N = 3) for oxalate and citrate are about 44 and 244 ng/mL, respectively. The overall recovery is between 80.0 and 89.2%. This method offers a better choice for quantitative analysis of strong anions such as oxalate and citrate in diagnostic testing associated with human diseases.