3D-printed flow system for determination of lead in natural waters

Application of three-dimensional printing technology in environmental analysis: A review

The development of environmental analysis devices with high performance is essential to assess the potential risks of environmental pollutants. However, it is still challenging to develop environmental analysis equipment with miniaturization, portability, and high sensitivity based on traditional processing techniques. In recent years, the popularity of 3D printing technology (3DP) with high precision, low cost, and unlimited design freedom has provided opportunities to solve the existing challenges of environmental analysis. 3D printing has brought solutions to promote the high performance and versatility of environmental analysis equipment by optimizing printing materials, enhancing equipment structure, and integrating multidisciplinary technology. In this paper, we comprehensively review the latest progress in 3D printing in various aspects of environmental analysis procedures, including but not limited to sample collection, pretreatment, separation, and detection. We highlight their advantages and challenges in determining various environmental contaminants through passive sampling, solid-phase extraction, chromatographic separation, and mass spectrometry detection. The manufacturing of 3D-printed environmental analysis devices is also discussed. Finally, we look forward to their development prospects and challenges.

Simple Preparation of Metal-Impregnated FDM 3D-Printed Structures

Modifying the natural characteristics of PLA 3D-printed models is of interest in various research areas in which 3D-printing is applied. Thus, in this study, we describe the simple impregnation of FDM 3D-printed PLA samples with well-defined silver nanoparticles and an iron metal salt. Quasi-spherical and dodecahedra silver particles were strongly attached at the channels of 3D-printed milli-fluidic reactors to demonstrate their attachment and interaction with the flow, as an example. Furthermore, Fenton-like reactions were successfully developed by an iron catalyst impregnated in 3D-printed stirrer caps to induce the degradation of a dye and showed excellent reproducibility.

Analytical Chemistry: Tasks, Resolutions and Future Standpoints of the Quantitative Analyses of Environmental Complex Sample Matrices

Currently, the challenges that analytical chemistry has to face are ever greater and more complex both from the point of view of the selectivity of analytical methods and their sensitivity. This is especially true in quantitative analysis, where various methods must include the development and validation of new materials, strategies, and procedures to meet the growing need for rapid, sensitive, selective, and green methods. In this context, given the International Guidelines, which over time, are updated and which set up increasingly stringent “limits”, constant innovation is required both in the pre-treatment procedures and in the instrumental configurations to obtain reliable, accurate, and reproducible information. In addition, the environmental field certainly represents the greatest challenge, as analytes are often present at trace and ultra-trace levels. These samples containing analytes at ultra-low concentration levels, therefore, require very labor-intensive sample preparation procedures and involve the high consumption of organic solvents that may not be considered “green”. In the literature, in recent years, there has been a strong development of increasingly high-performing sample preparation techniques, often “solvent-free”, as well as the development of hyphenated instrumental configurations that allow for reaching previously unimaginable levels of sensitivity. This review aims to provide an update of the most recent developments currently in use in sample pre-treatment and instrument configurations in the environmental field, also evaluating the role and future developments of analytical chemistry in light of upcoming challenges and new goals yet to be achieved.

Microfluidic assisted recognition of miRNAs towards point-of-care diagnosis: Technical and analytical overview towards biosensing of short stranded single non-coding oligonucleotides

MiRNAs are short stranded single non-coding oligonucleotides that play an important role in regulating gene expression. MiRNAs are stable in RNase enriched environments such as human body fluids and their dysregulation or abnormal abundance in human body fluids as a diagnostic biomarker has been associated with several diseases. Due to the low concentration of miRNAs, it is difficult to detect using interactive methods (ideal detection limit is femtomolar range). However, clinicians lack sensitive and reliable methods for quantifying miRNA. Microfluidic devices integrated with electrochemical, optical (fluorometric, SERs, FRET, colorimetric), electrochemiluminescence and photoelectrochemical signal readout led to development innovative diagnostic device test, can probably overcome the limitations of the traditional methods. In the present review, microfluid methods for the sensitive and selective recognition of miRNA in various biological matrices are surveyed. Also, advantages and limitation of recognition methods on the performance and efficiency of microfluidic based biosensing of miRNAs are critically investigated. Finally, the future perspectives on the diagnosis of disease based on microfluidic analysis of miRNAs are provided.

A novel 3D printed device with conductive elements for electromembrane extraction combined with HPLC and UV detector

This paper is focused on proposing for a new design and setup for electromembrane extraction. A new cap was designed and conductive vials of different shape were fabricated using three-dimensional printing. The new cap holds three fibers to enhance electromembrane extraction recovery. Conductive vials can simultaneously perform as electrodes therefore, there is no need to include an electrode in sample solutions. Phenobarbital and phenytoin were used as model compounds to assess the setup performance. Under optimal conditions, these analytes were extracted from the sample solution at pH = 9 to the acceptor solution at pH = 13 with a voltage of 40 V for 20 min, while 1-octanol was employed as the supported-liquid-membrane. The influence of conductive vials geometry on the recovery was examined and effects of different shapes were studied by performing numerical simulation to establish electric potential distribution. Of the vials tested with circular, triangular and floral-like cross-sections the latter exhibited the best voltage distribution. The circular vial had the highest recovery attributed to its better hydrodynamic shape, which allows rapid fluid sample transport and therefore enhanced system recovery. The extraction recovery and RSD of circular vial with three fibers was 33.0 and 7.6 for phenobarbital and 42.2 and 10.4 for phenytoin. This article is protected by copyright. All rights reserved.

Flow-Injection Methods in Water Analysis-Recent Developments

Widespread demand for the analysis and control of water quality and supply for human activity and ecosystem sustainability has necessitated the continuous improvement of water analysis methods in terms of their reliability, efficiency, and costs. To satisfy these requirements, flow-injection analysis using different detection methods has successfully been developed in recent decades. This review, based on about 100 original research papers, presents the achievements in this field over the past ten years. Various methodologies for establishing flow-injection measurements are reviewed, together with microfluidics and portable systems. The developed applications mostly concern not only the determination of inorganic analytes but also the speciation analysis of different elements, and the determination of several total indices of water quality. Examples of the determination of organic residues (e.g., pesticides, phenolic compounds, and surfactants) in natural surface waters, seawater, groundwater, and drinking water have also been identified. Usually, changes in the format of manual procedures for flow-injection determination results in the improvement of various operational parameters, such as the limits of detection, the sampling rate, or selectivity in different matrices.

3D printing for the integration of porous materials into miniaturised fluidic devices: A review

Porous materials facilitate the efficient separation of chemicals and particulate matter by providing selectivity through structural and surface properties and are attractive as sorbent owing to their large surface area. This broad applicability of porous materials makes the integration of porous materials and microfluidic devices important in the development of more efficient, advanced separation platforms. Additive manufacturing approaches are fundamentally different to traditional manufacturing methods, providing unique opportunities in the fabrication of fluidic devices. The complementary 3D printing (3DP) methods are each accompanied by unique opportunities and limitations in terms of minimum channel size, scalability, functional integration and automation. This review focuses on the developments in the fabrication of 3DP miniaturised fluidic devices with integrated porous materials, focusing polymer-based methods including fused filament fabrication (FFF), inkjet 3D printing and digital light projection (DLP). The 3DP methods are compared based on resolution, scope for multimaterial printing and scalability for manufacturing. As opportunities for printing pores are limited by resolution, the focus is on approaches to incorporate materials with sub-micron pores to be used as membrane, sorbent or stationary phase in separation science using Post-Print, Print-Pause-Print and In-Print processes. Technical aspects analysing the efficiency of the fabrication process towards scalable manufacturing are combined with application aspects evaluating the separation and/or extraction performance. The review is concluded with an overview on achievements and opportunities for manufacturable 3D printed membrane/sorbent integrated fluidic devices.

Lead Assays with Smartphone Detection Using a Monolithic Rod with 4-(2-Pyridylazo) Resorcinol

A monolithic rod of polyurethane foam-[4-(2-pyridylazo) resorcinol] (PUF-PAR) as a simple chemical sensor for lead assays with smartphone detection and image processing was developed. With readily available simple apparatus such as a plastic cup and a stirrer rod, the monolithic PUF rod was synthesized in a glass tube. The monolithic PUF-PAR rod could be directly loaded by standard/sample solution without sample preparation. A one-shot image in G/B value from a profile plot in ImageJ for a sample with triplicate results via a single standard calibration approach was obtained. A linear single standard calibration was: [G/B value] = -0.038[µg Pb2+] + 2.827, R2 = 0.95 for 10-30 µg Pb2+ with a limit of quantitation (LOQ) of 33 µg L-1. The precision was lower than 15% RSD. The proposed method was tested by an assay for Pb2+ contents in drinking water samples from Bangkok. The results obtained by the proposed method agree with those of ICP-OES and with 100-120% recovery, demonstrating that the method is useful for screening on-site water monitoring.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Flow-based System: A Highly Efficient Tool Speeds Up Data Production and Improves Analytical Performance

In this review, we cite references from the period between 2015 and 2020 related to the use of a flow-based system as a tool to obtain a modern analytical system for speeding up data production and improving performance. Based on a great deal of concepts for automatic systems, there are several research groups introduced in the development of flow-based systems to increase sample throughput while retaining the reproducibility and repeatability as well as to propose new platforms of flow-based systems, such as microfluidic chip and paper-based devices. Additionally, to apply a developed system for on-site analysis is one of the key features for development. We believe that this review will be very interested and useful for readers because of its impact on developing novel analytical systems. The content of the review is categorized following their applications including quality control and food safety, clinical diagnostics, environmental monitoring and miscellaneous.

3D printing in analytical chemistry: current state and future

The rapid development of additive technologies in recent years is accompanied by their intensive introduction into various fields of science and related technologies, including analytical chemistry. The use of 3D printing in analytical instrumentation, in particular, for making prototypes of new equipment and manufacturing parts having complex internal spatial configuration, has been proved as exceptionally effective. Additional opportunities for the widespread introduction of 3D printing technologies are associated with the development of new optically transparent, current- and thermo-conductive materials, various composite materials with desired properties, as well as possibilities for printing with the simultaneous combination of several materials in one product. This review will focus on the application of 3D printing for production of new advanced analytical devices, such as compact chromatographic columns for high performance liquid chromatography, flow reactors and flow cells for detectors, devices for passive concentration of toxic compounds and various integrated devices that allow significant improvements in chemical analysis. A special attention is paid to the complexity and functionality of 3D-printed devices.

3D-Printed Column with Porous Monolithic Packing for Online Solid-Phase Extraction of Multiple Trace Metals in Environmental Water Samples

In this study, we used a multimaterial three-dimensional printing (3DP) technology and porous composite filaments (Lay-Fomm, Gel-Lay, and Lay-Felt) to fabricate solid phase extraction (SPE) columns for the enhanced extraction of multiple metal ions. When employed as sample pretreatment devices in an automatic flow injection analysis/inductively coupled plasma mass spectrometry (ICP-MS) system, these 3D-printed SPE columns performed the near-complete extractions of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from natural water samples prior to ICP-MS determination. After optimizing the column fabrication, the extraction conditions, and the automatic analysis system, the column packed with the porous composite Lay-Fomm 40 was found to provide the highest extraction performance-the extraction efficiencies of the listed metal ions were all greater than 99.2%, and the detection limits of the method ranged from 0.3 to 6.7 ng L^-1. The detection of these metal ions in several reference materials (CASS-4, SLEW-3, 1640a, and 1643f) validated the reliability of this method; spike analyses of collected water samples (groundwater, river water, and seawater) demonstrated the applicability of the method. The nature of the printing materials enhanced the analytical performance of 3D-printed sample pretreatment devices. Such approaches will be useful to diversify the range of sample preparation schemes and analytical methods enabled by 3DP technologies.

3D Printing in analytical sample preparation

In the last 5 years, additive manufacturing (three-dimensional printing) has emerged as a highly valuable technology to advance the field of analytical sample preparation. Three-dimensional printing enabled the cost-effective and rapid fabrication of devices for sample preparation, especially in flow-based mode, opening new possibilities for the development of automated analytical methods. Recent advances involve membrane-based three-dimensional printed separation devices fabricated by print-pause-print and multi-material three-dimensional printing, or improved three-dimensional printed holders for solid-phase extraction containing sorbent bead packings, extraction disks, fibers, and magnetic particles. Other recent developments rely on the direct three-dimensional printing of extraction sorbents, the functionalization of commercial three-dimensional printable resins, or the coating of three-dimensional printed devices with functional micro/nanomaterials. In addition, improved devices for liquid-liquid extraction such as extraction chambers, or phase separators are opening new possibilities for analytical method development combined with high-performance liquid chromatography. The present review outlines the current state-of-the-art of three-dimensional printing in analytical sample preparation.

Modified 3D-printed device for mercury determination in waters

3D printing technology is increasingly used in flow analysis, to develop low cost and tailor-made devices. The possibility of grafting specific molecules onto 3D printed parts offers new perspectives for the development of flow systems. In this study, a MPFS system including a dicarboxylate 1,5-diphenyl-3-thiocarbazone grafted 3D-printed device has been developed for mercury determination. For this purpose, the surface of 3D-printed cuboids was first modified with amine functional groups and then grafted with dicarboxylate 1,5-diphenyl-3-thiocarbazone. This new grafted device resulted in selective mercury preconcentration with extraction and elution yields higher than 90% even at high sampling flow rates. The detection can then be carried out in two ways: a direct detection of mercury extracted onto 3D-printed grafted cuboids by atomic absorption spectrophotometry after amalgam on gold or a detection of mercury in solution after elution with l-cysteine by spectrophotometry or cold vapour atomic absorption spectrometry.

One-step 3D printed flow cells using single transparent material for flow injection spectrophotometry

A very simple approach to fabricate flow-through cells for flow injection spectrophotometry is proposed. Flow cells are completely fused deposition modelling 3D printed by using coloured-transparent polylactic acid filament. Channels with 1.0 mm i.d. circular cross section and optical windows of 0.3-1.0 mm thickness are fabricated. Thin layers of the transparent material allow light transmitting with low attenuation, but coloured cell body can prevent stray light transmitting through. Transparent 3D printing filaments of different colours are compared and Grey-transparent (Grey-T) provides highest sensitivity for the determination of nitrite via Griess reaction. Flow cells of 10-50 mm pathlength have been fabricated by using the Grey-T filament. Effective pathlengths are estimated to be 83.9-96.2% of the physical pathlengths. The printing fabricated cells are used for flow injection analysis of nitrite, and linear correlation (R² = 0.9991-0.9999) and limits of detection of 0.27, 0.087 and 0.045 μM for 10, 30 and 50 mm cells, are obtained. The 3D printed flow cells have acceptable chemical compatibility and signal stability.

Direct photoimmobilization of extraction disks on "green state" 3D printed devices

Post-curing is essential to improve the mechanical properties of 3D printed parts fabricated by stereolithography (SLA), since right after 3D printing they remain in a "green state". It means that the 3D printed parts have reached their final shape, but the polymerization reaction has not been yet completed. Herein, we take advantage of the tacky partially polymerized surface of "green state" SLA 3D printed parts to immobilize extraction disks and miniature magnets, which after UV post-curing, become permanently attached to the 3D printed part resulting in a rotating-disk sorptive extraction device (RDSE). The developed "stick & cure" procedure is reagent-free and does not require any additional preparation time, specialized skills, or instrumentation. As proof of concept, 3D printed RDSE devices with immobilized chelating disks have been applied to the simultaneous extraction of 14 trace metals prior to ICP-OES determination, featuring LODs between 0.03 and 1.27 μg L^-1, and an excellent device-to-device reproducibility (n = 5, RSD = 2.7-8.3%). The developed method was validated using certified wastewater and soil reference samples, and satisfactory spiking recoveries were obtained in the analysis of highly polluted solid waste treatment plant leachates (89-110%). In addition, exploiting the versatility of 3D printing, nine RDSE devices with different shapes were fabricated. Their performance was evaluated and compared for the fast extraction of the highly toxic Cr (VI) as its 1,5-diphenylcarbazide complex in reversed-phase mode, showing different extraction performance on depending on the shape of the 3D printed RDSE device.

Advances in Optical Sensing and Bioanalysis Enabled by 3D Printing

The recent explosion of 3D printing applications in scientific literature has expanded the speed and effectiveness of analytical technological development. 3D printing allows for manufacture that is simply designed in software and printed in-house with nearly no constraints on geometry, and analytical methodologies can thus be prototyped and optimized with little difficulty. The versatility of methods and materials available allows the analytical chemist or biologist to fine-tune both the structural and functional portions of their apparatus. This flexibility has more recently been extended to optical-based bioanalysis, with higher resolution techniques and new printing materials opening the door for a wider variety of optical components, plasmonic surfaces, optical interfaces, and biomimetic systems that can be made in the laboratory. There have been discussions and reviews of various aspects of 3D printing technologies in analytical chemistry; this Review highlights recent literature and trends in their applications to optical sensing and bioanalysis.

Automated dispersive liquid-liquid microextraction based on the solidification of the organic phase

In this work, the dispersive liquid-liquid microextraction technique based on the solidification of the organic phase (DLLME-SFO) has been automated for the first time. DLLME-SFO is automated by hyphenating a sequential injection analysis (SIA) system with a custom-made robotic phase separator. Automated in-syringe DLLME is followed by phase separation in a 3D printed device integrating a Peltier cell set, mounted on a multi-axis robotic arm. The combined action of the flow system and the robotic arm is controlled by a single software package, enabling the solidification/melting and collection of the organic phase for further analyte quantification. As proof-of-concept, automated DLLME-SFO was applied to the extraction of parabens followed by separation using liquid chromatography, obtaining LODs between 0.3 and 1.3 µg L^-1 (4 mL of sample extracted in 1 mL of 1-dodecanol: MeOH, 15:85, v-v). The method showed a high reproducibility, obtaining intraday RSDs between 4.6% and 5.8% (n = 6), and interday RSDs between 5.6% and 8.6% (n = 6). The developed method was evaluated for the determination of parabens in water, urine, saliva, and personal care products.

In-line carbon nanofiber reinforced hollow fiber-mediated liquid phase microextraction using a 3D printed extraction platform as a front end to liquid chromatography for automatic sample preparation and analysis: A proof of concept study

A novel concept for automation of nanostructured hollow-fiber supported microextraction, combining the principles of liquid-phase microextraction (LPME) and sorbent microextraction synergically, using mesofluidic platforms is proposed herein for the first time, and demonstrated with the determination of acidic drugs (namely, ketoprofen, ibuprofen, diclofenac and naproxen) in urine as a proof-of-concept applicability. Dispersed carbon nanofibers (CNF) are immobilized in the pores of a single-stranded polypropylene hollow fiber (CNF@HF) membrane, which is thereafter accommodated in a stereolithographic 3D-printed extraction chamber without glued components for ease of assembly. The analytical method involves continuous-flow extraction of the acidic drugs from a flowing stream donor (pH 1.7) into an alkaline stagnant acceptor (20 mmol L^-1 NaOH) containing 10% MeOH (v/v) across a dihexyl ether impregnated CNF@HF membrane. The flow setup features entire automation of the microextraction process including regeneration of the organic film and on-line injection of the analyte-laden acceptor phase after downstream neutralization into a liquid chromatograph (LC) for reversed-phase core-shell column-based separation. Using a 12-cm long CNF@HF and a sample volume of 6.4 mL, linear dynamic ranges of ketoprofen, naproxen, diclofenac and ibuprofen, taken as models of non-steroidal anti-inflammatory drugs, spanned from ca. 5-15 µg L^-1 to 500 µg L^-1 with enhancement factors of 43-97 (against a direct injection of 10 µL standards into LC), and limits of detection from 1.6 to 4.3 µg L^-1. Relative recoveries in real urine samples ranged from 97% to 105%, thus demonstrating the reliability of the automatic CNF@HF-LPME method for in-line matrix clean-up and determination of drugs in urine at therapeutically relevant concentrations.

3D printed device for the automated preconcentration and determination of chromium (VI)

A 3D printed device for the fully automated disk-based solid-phase extraction (SPE) of Cr (VI) from water samples has been fabricated. The compatibility of the use of organic solvents for analyte elution with 3D printed flow devices based on polymers fabricated using stereolithograph​y has been evaluated. The developed methodology comprises the complexation of Cr (VI) with 1, 5-diphenylcarbazide (DPC) in acidic medium and the subsequent retention of the complex in a SBD-RPS disk contained within the 3D printed device. A multisyringe flow injection analysis system with online spectrophotometric detection has been used for the automation of the method. The fabricated 3D printed device integrates the different components of the flow analysis manifold, including connectors and mixers, being a powerful approach towards the reproducible construction of highly integrated flow-based manifolds. The extracted Cr (VI)-DPC complex is eluted with a mixture of methanol- sulfuric acid and quantified at 540 nm. The effect on the analytical signal and the optimization of variables were evaluated using multivariate and univariate techniques. A detection limit of 1 ng Cr (VI) and a linear working range of 3.2-600 ng Cr (VI) were obtained using a sample volume of 2 ml. The intra-day and inter-day RSDs were 4.8% (10 µg L^-1, n = 12) and 3.4% (n = 5, different day with a different disk), respectively. The applicability of the fabricated 3D printed device has been proved by the determination of Cr (VI) in groundwater, surface water and leachates.

3D printed device including disk-based solid-phase extraction for the automated speciation of iron using the multisyringe flow injection analysis technique

The development of advanced manufacturing techniques is crucial for the design of novel analytical tools with unprecedented features. Advanced manufacturing, also known as 3D printing, has been explored for the first time to fabricate modular devices with integrated features for disk-based automated solid-phase extraction (SPE). A modular device integrating analyte oxidation, disk-based SPE and analyte complexation has been fabricated using stereolithographic 3D printing. The 3D printed device is directly connected to flow-based analytical instrumentation, replacing typical flow networks based on discrete elements. As proof of concept, the 3D printed device was implemented in a multisyringe flow injection analysis (MSFIA) system, and applied to the fully automated speciation, SPE and spectrophotometric quantification of Fe in water samples. The obtained limit of detection for total Fe determination was 7ng, with a dynamic linear range from 22ng to 2400ng Fe (3mL sample). An intra-day RSD of 4% (n = 12) and an inter-day RSD of 4.3% (n = 5, 3mL sample, different day with a different disk), were obtained. Incorporation of integrated 3D printed devices with automated flow-based techniques showed improved sensitivity (85% increase on the measured peak height for the determination of total Fe) in comparison with analogous flow manifolds built from conventional tubing and connectors. Our work represents a step forward towards the improved reproducibility in the fabrication of manifolds for flow-based automated methods of analysis, which is especially relevant in the implementation of interlaboratory analysis.