Design and optimization of a fused-silica microfluidic device for separation of trivalent lanthanides by isotachophoresis

Elemental analysis of rare earth elements is essential in a variety of fields including environmental monitoring and nuclear safeguards; however, current techniques are often labor intensive, time consuming, and/or costly to perform. The difficulty arises in preparing samples, which requires separating the chemically and physically similar lanthanides. However, by transitioning these separations to the microscale, the speed, cost, and simplicity of sample preparation can be drastically improved. Here, all fourteen non-radioactive lanthanides (lanthanum through lutetium minus promethium) are separated by ITP for the first time in a serpentine fused-silica microchannel (70 µm wide × 70 µm tall × 33 cm long) in <10 min at voltages ≤8 kV with limits of detection on the order of picomoles. This time includes the 2 min electrokinetic injection time at 2 kV to load sample into the microchannel. The final leading electrolyte consisted of 10 mM ammonium acetate, 7 mM α-hydroxyisobutyric acid, 1% polyvinylpyrrolidone, and the final terminating electrolyte consisted of 10 mM acetic acid, 7 mM α-hydroxyisobutyric acid, and 1% polyvinylpyrrolidone. Electrophoretic electrodes are embedded in the microchip reservoirs so that voltages can be quickly applied and switched during operation. The limits of detection are quantified using a commercial capacitively coupled contactless conductivity detector (C⁴ D) to calculate ITP zone lengths in combination with ITP theory. Optimization of experimental procedures and reproducibility based on statistical analysis of subsequent experimental results are addressed. Percent error values in band length and conductivity are ≤8.1 and 0.37%, respectively.

Comparison of the renal cortex and the medulla for antibody mediated rejection

OBJECTIVES

The presence of the peritubular capillaritis and its extent are important for diagnosis of the antibody-mediated rejection in kidneys. However, it is recommended that peritubular capillaritis should only be scored in the cortex. This study aims to focus on peritubular capillaritis scoring both in the cortex and the medulla to understand the value of the medulla in the diagnosis of antibody-mediated rejection.

METHODS

Fifty-one allograft renal biopsy were re-evaluated for peritubular capillaritis, C4d and acute tubular injury, separately for the cortex and the medulla according to the Banff.

RESULTS

Seventeen cases (33.3%) had peritubular capillaritis both in the cortex and the medulla and three (5.9%) cases had peritubular capillaritis only in the cortex while five (9.8%) cases had only in the medulla. Eighteen (35%) of the cases had C4d staining both in the cortex and the medulla and 14 (27.5%) cases had C4d positivity only in the cortex and 18 (35.3%) cases only in the medulla. Twenty-three (45%) cases had acute tubular injury both in the cortex and the medulla and 31 (60.7%) cases had acute tubular injury only in the cortex and 23 (45.1%) cases had only in the medulla. The sensitivity, specificity, positive and negative predictive values of medullar peritubular capillaritis predicting cortical peritubular capillaritis were 85.7%, 86.7%, 81.8% and 89.7%, respectively.

CONCLUSION

In case of absence of the cortical tissue, medulla can be used as a reference for antibody-mediated rejection considering the morphological features, results of donor-specific antibody and renal function tests.

Determination of Inorganic Ion Profiles of Illicit Drugs by Capillary Electrophoresis

A portable capillary electrophoresis instrument with dual capacitively coupled contactless conductivity detection (C⁴ D) was used to determine the inorganic ionic profiles of three pharmaceutical samples and precursors of two illicit drugs (contemporary samples of methylone and para-methoxymethamphetamine). The LODs ranged from 0.10 μmol/L to 1.25 μmol/L for the 10 selected cations, and from 0.13 μmol/L to 1.03 μmol/L for the eight selected anions. All separations were performed in less than 6 min with migration times and peak area RSD values ranging from 2 to 7%. The results demonstrate the potential of the analysis of inorganic ionic species to aid in the identification and/or differentiation of unknown tablets, and real samples found in illicit drug manufacture scenarios. From the resulting ionic fingerprint, the unknown tablets and samples can be further classified.

In-plane alloy electrodes for capacitively coupled contactless conductivity detection in poly(methylmethacrylate) electrophoretic chips

A simple method for producing PMMA electrophoresis microchips with in-plane electrodes for capacitively coupled contactless conductivity detection is presented. One PMMA plate (channel plate) is embossed with the microfluidic and electrode channels and lamination bonded to a blank PMMA cover plate of equal dimensions. To incorporate the electrodes, the bonded chip is heated to 80 °C, above the melting point of the alloy (≈ 70 °C) and below the glass transition temperature of the PMMA (≈ 105 °C), and the molten alloy drawn into the electrode channels with a syringe before being allowed to cool and harden. A 0.5 mm diameter stainless steel pin is then inserted into the alloy filled reservoirs of the electrode channels to provide external connection to the capacitively coupled contactless conductivity detection detector electronics. This advance provides for a quick and simple manufacturing process and negates the need for integrating electrodes using costly and time-consuming thin film deposition methods. No additional detector cell mounting structures were required and connection to the external signal processing electronics was achieved by simply slipping commercially available shielded adaptors over the pins. With a non-optimised electrode arrangement consisting of a 1 mm detector gap and 100 μm insulating distance, rapid separations of ammonium, sodium and lithium (<22 s) yielded LODs of approximately 1.5-3.5 ppm.