3D Printed All-in-One Sample Introduction System for ICP-MS: Integrating Chip-Based Array Monolithic Microextraction, Microvalve Control, and Microflow Nebulizer

Three-dimensional printing (3DP) technology was applied to fabricate an all-in-one sample introduction system for inductively coupled plasma mass spectrometry (ICP-MS) analysis of ultratrace rare-earth elements (REEs) in cells. The developed 3DP all-in-one sample introduction system comprised a microfluidic chip integrating cell lysis and monolithic microextraction array, a microvalve control unit, and a microflow total consumption high-efficiency nebulizer (MTHEN). It made full use of the advantages of 3DP in preparing user-customized three-dimensional structures. On the one hand, an integrated chip consisting of a three-dimensional mixing zone and array monolithic columns with a skeleton structure of UiO-66 was printed directly, which are beneficial for mixing the cells with lysis buffer and extraction of target elements from the cell lysate, respectively, as well as improving the mass transfer. On the other hand, the 3DP-MTHEN with a customized interface was directly connected to an ICP torch, providing a high sample transport efficiency (81.1%) under a low flow rate of 6 μL min-1. The sensitivity of ICP-MS by using a 3DP-MTHEN for representative elements was 4.7-6.0 times higher than that obtained by using a commercial microflow Burgener SC175 nebulizer (detection limits of 0.7-13.3 vs 0.7-52.6 ng L-1). Besides, the 3DP-MTHEN exhibited a lower cost ($13 vs 1550). The proposed system has been applied to the determination of ultratrace REEs in MCF-7 cells. It exhibited simple operation, low cell consumption (500 cells), good precision (2.2-11.9%), low detection limit (1.3-8.6 ng L-1), and quantitative recovery (71.9%-119%). It merits application potential for ultratrace elemental analysis in samples with very limited volume, especially cells.

Hierarchically porous covalent organic framework doped monolithic column for on-line chip-based array microextraction of nonsteroidal anti-inflammatory drugs in microlitre volume of blood

BACKGROUND

Traditional blood drug analysis involves large blood consumption and complicated operations and a further reduction in blood consumption is urgently needed. Chip-based monolithic column microextraction is a good strategy for the pretreatment of small-volume samples, and new monolithic materials is the critical factor. Covalent organic frameworks (COFs) are good adsorbents due to large specific surface area and rich conjugated structure. However, the poor dispersion ability of COFs in prepolymer solution severely hinders the preparation of COFs doped monolithic columns. Herein, high internal phase emulsion with viscoelastic properties was adopted to fixed COF particles.

RESULTS

The COFs doped monolith exhibited a hierarchical porous structure and improved extraction efficiency for interest nonsteroidal anti-inflammatory drugs (NSAIDs) (68.2-77.3 vs 28.4-57.7 %). A chip-based monolithic column array was fabricated and coupled with high-performance liquid chromatography (HPLC)-ultraviolet detection for online determination of five NSAIDs in microlitre volume of blood. The throughput of the developed method was approximately 3 h-1, mainly determined by the separation time (22 min) of target NSAIDs in HPLC. Under the optimal conditions (200 μL sample solution, pH = 3 at a sampling folw rate of 5 μL min-1 and 20 μL of acetonitrile/10 mmol L-1 NaOH (9/1, v/v) as desorbent), the detection limit of 4.39-15.5 μg L-1 was obtained for target NSAIDs in blood with RSD of 7.8-15.3 % and R2 of 0.9943-0.9978. The method was applied to the analysis of human serum (20 μL) and dried blood spot, with recovery of 82.0-118 % for target NSAIDs.

SIGNIFICANCE

A method was proposed for the preparation of COF doped monolithic columns by emulsion polymerization, avoiding uneven distribution of COFs caused by their easy sedimentation in traditional free radical preparation of monolithic columns. Then a chip-based monolithic column array coupled with on-line HPLC-UV detection was established for the quantification of five NSAIDs in microlitre-blood samples. The developed method merits high automation and good anti-interference ability, with extremely low sample/reagents consumption.

Graphite Phase Carbon Nitride Nanosheets-Based Fluorescent Sensors for Analysis and Detection

Fluorescent sensors reflect information such as the concentration or content of the analysis by interacting with a specific recognition group to change the signal of the fluorophore. It has attracted much attention because of its advantages of high sensitivity, fast detection speed and low cost, and it has become an effective alternative to traditional detection methods. Graphitic phase carbon nitride nanosheets (g-CNNs) are a class of carbon-based fluorescent nanomaterials derived from bulk graphite phase carbon nitride (g-C3N4), which have attracted much attention from scholars because of their advantages of low cost, simple fabrication, high quantum yield, strong stability and nontoxicity. Functional modified g-CNNs can greatly improve the photocatalytic performance. At present, although there have been some researches on fluorescent sensors based on g-CNNs. Nevertheless, there are few reviews about the g-CNNs-based fluorescent sensors. Therefore, in addition to summarizing the sensing mechanism of fluorescent sensors (such as photoinduced electron transfer, fluorescence resonance energy transfer, and intramolecular charge transfer) and the advantages and disadvantages of common signal substances, this paper focused on the application progress of g-CNNs-based fluorescent sensors in the field of analysis and detection.

Automated and semi-automated packed sorbent solid phase (micro) extraction methods for extraction of organic and inorganic pollutants

In this study, the packed sorbent solid phase (micro) extraction methods from manual to automated modes are reviewed. The automatic methods have several remarkable advantages such as high sample throughput, reproducibility, sensitivity, and extraction efficiency. These methods include solid-phase extraction, pipette tip micro-solid phase extraction, microextraction by packed sorbent, in-tip solid phase microextraction, in-tube solid phase microextraction, lab-on-a-chip, and lab-on-a-valve. The recent application of these methods for the extraction of organic and inorganic compounds are discussed. Also, the combination of novel technologies (3D printing and robotic platforms) with the (semi)automated methods are investigated as the future trend.

Effect of CuO/ZnO/FTO electrode properties on the performance of a photo-microbial fuel cell sensor for the detection of heavy metals

The development of sustainable, low-cost and responsive technology for heavy metals detection in wastewater is crucial. In this study, by combining CuO/ZnO photocathode with microbial anode, a novel photo-microbial fuel cell (PMFC) sensor was developed. The self-powered PMFC was performed under light and dark condition for heavy metals detection. Compared with MFC sensor, PMFC sensor showed a wider detection range (0.1-4 mg L^-1 of Cd²⁺ and 10-80 mg L^-1 of Cu²⁺). The improved performance in sensing limit and sensitivity was mainly attributed to the intimate P-N heterojunctions formed in CuO/ZnO, which accelerated the electron transport between the photocathode and the microbial anode. Besides, the toxicity of five heavy metals tested in PMFC was shown as Cd²⁺>Cr⁶⁺>Zn²⁺>Hg²⁺>Cu²⁺. This study has taken advantage of the characteristics of PMFC and facilitated its application in heavy metals detection, which provides a new approach for the development of biosensors.

Multifunctional microfluidic chips for the single particle inductively coupled plasma mass spectrometry analysis of inorganic nanoparticles

This study aimed at exploiting the so far unexploited potential of carrying out on-line sample pretreatment steps on microfluidic chips for single particle inductively coupled plasma mass spectrometry (spICP-MS) measurements, and demonstrating their ability to practically facilitate most of the simpler tasks involved in the spICP-MS analysis of nanoparticles. For this purpose, polydimethylsiloxane microfluidic chips, capable of high-range dilution and sample injection were made by casting, using high-precision, 3D-printed molds. Optimization of their geometry and functions was done by running several hydrodynamic simulations and by gravimetric, fluorescence enhanced microscope imaging and solution-based ICP-MS experiments. On the optimized microfluidic chips, several experiments were done, demonstrating the benefits of the approach and these devices, such as the determination of nanoparticle concentration using only a few tens of microliters of sample, elimination of solute interferences by dilution, solution-based size calibration and characterisation of binary nanoparticles. Due to the unique design of the chips, they can be linked together to extend the dilution range of the system by more than a magnitude per chip. This feature was also demonstrated in applications requiring multiple-magnitude dilution rates, when two chips were sequentially coupled.

226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps

Achieving precise and accurate quantification of radium (²²⁶Ra) and cesium (¹³⁷Cs) by inductively coupled plasma mass spectrometry (ICP-MS) is of particular interest in the field of radiological monitoring and more widely in environmental and biological sciences. However, the accuracy and sensitivity of the quantification depend on the analytical strategy implemented. Eliminating interferences during the sample handling step and/or during the analysis step is critical since presence of matrix elements can lead to spectral and non-spectral interferences in ICP-MS. Consequently, before the ICP-MS analysis, multiple sample preparation approaches have been applied to purify and/or pre-concentrate environmental and biological samples containing radium and cesium through years, such as (co)-precipitation, solid phase extraction (SPE) or dispersive SPE (dSPE). Separation steps using liquid chromatography and capillary electrophoresis can also be useful in complement with the abovementioned sample preparation techniques. The most attractive sample handling technique remains SPE but efficiency of the extraction procedures is currently limited by sorbent specificity. Indeed, with the recent advances in ICP-MS instrumentation, it becomes indispensable to eliminate residual interferences and improve sensitivity. It is in this direction that it will be possible to meet analytical challenges, e.g. analyzing radium and cesium at concentrations below the pg L^-1 range in complex matrices of small volumes, as they are found for instance in pore waters or in biological samples. Development of new innovative sorbents based for example on hybrid and nanostructured materials has been reported with the aim of enhancing sorbent specificity and/or capacity. In the present review, the performances of the different analytical approaches are discussed, followed by an overview of applications.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.