3D-Printed Microflow Injection Analysis Platform for Online Magnetic Nanoparticle Sorptive Extraction of Antimicrobials in Biological Specimens as a Front End to Liquid Chromatographic Assays

Technological Advancement and Trend in Selective Bioanalytical Sample Extraction through State of the Art 3-D Printing Techniques Aiming 'Sorbent Customization as per need'

The inherent complexity of biological matrices and presence of several interfering substances in biological samples make them unsuitable for direct analysis. An effective sample preparation technique assists in analyte enrichment, improving selectivity and sensitivity of bioanalytical method. Because of several key benefits of employing 3D printed sorbent in sample extraction, it has recently gained popularity across a variety of industries. Applications for 3D printing in the field of bioanalytical research have grown recently, particularly in the areas of miniaturization, (bio)sensing, sample preparation, and separation sciences. Due to the high expense of the solid phase microextraction cartridge, researcher approaches in-lab production of sorbent material for the extraction of analyte from biological samples. Owing to its distinct advantages such as low costs, automation capabilities, capacity to produce products in a variety of shapes, and reduction of tedious steps of sample preparation, 3D printed sorbents are gaining increased attention in the field of bioanalysis. It is also reported to offer high selectivity and assist in achieving a much lower limit of detection. In this review, we have discussed current advancements in different types of 3D printed sorbents, production methods, and their applications in the field of bioanalytical sample preparation.

Solvent-activated 3D-printed electrodes and their electroanalytical potential

This work is a comprehensive study describing the optimization of the solvent-activated carbon-based 3D printed electrodes. Three different conductive filaments were used for the preparation of 3D-printed electrodes. Electrodes treatment with organic solvents, electrochemical characterization, and finally electroanalytical application was performed in a dedicated polyamide-based cell also created using 3D printing. We have investigated the effect of the used solvent (acetone, dichloromethane, dichloroethane, acetonitrile, and tetrahydrofuran), time of activation (from immersion up to 3600 s), and the type of commercially available filament (three different options were studied, each being a formulation of a polylactic acid and conductive carbon material). We have obtained and analysed a significant amount of collected data which cover the solvent-activated carbon-based electrodes surface wettability, microscopic insights into the surface topography analysed with scanning electron microscopy and atomic force microscopy, and finally voltammetric evaluation of the obtained carbon electrodes electrochemical response. All data are tabulated, discussed, and compared to finally provide the superior activation procedure. The electroanalytical performance of the chosen electrode is discussed based on the voltammetric detection of ferrocenemethanol.

3D printed stir bar sorptive extraction coupled with high performance liquid chromatography for trace estrogens analysis in environmental water samples

BACKGROUND

Any imaginary shape with good preparation reproducibility can be made by 3D printing technology, and it has been applied in various fields. Comparatively, its applications in sample pre-treatment are relatively less, most of which involves making extraction sorbents and producing non-functionalized devices for support assistance. 3D printing has not been applied to fabricate stir bars in stir bar sorptive extraction, mainly due to the lacking of suitable printing feedstocks. This work aimed to fabricate stir bars by 3D printing, reducing the manufacturing cost and steps and improving preparation reproducibility. (90) RESULTS: By using fused deposition modeling technique and porous filament printing feedstock, stir bars were fabricated without any modifications. Adsorption performance of 3D printed stir bars were investigated for substances with different structures and polarities. Five estrogens with adsorption efficiencies of over 80 % were selected as the representatives. The 3D printed stir bars exhibited good preparation reproducibility (2.9-4.4 %) and higher extraction recoveries (73-81 %) for five estrogens than commercial polydimethylsiloxane coated stir bars (13-69 %) in a shorter time (90 vs 120 min). They showed long lifespan (160 times) with good mechanical properties and merited reduced manufacturing cost (0.064 $ per bar) and manual operation. A method of stir bar sorptive extraction coupled with high performance liquid chromatography was proposed for trace analysis of estrogens in environmental water. Under the optimized conditions, the linear ranges for estrogens were 0.5-200 μg/L with LODs of 0.13-0.17 μg/L. (136) SIGNIFICANCE: The feasibility of fused deposition modeling in stir bar fabrication was demonstrated, along with the potential of porous filament printing feedstock as the sorbent for substances with medium polarity. 3D printed stir bars were featured with excellent preparation reproducibility, long lifespan, and good mechanical properties. The stir bar fabrication method can be used for mass production with minimal differences in products performance. (62).

Unlocking the potential of 3D printed microfluidics for mass spectrometry analysis using liquid infused surfaces

Combining microfluidics with mass spectrometry (MS) analysis has great potential for enabling new analytical applications and simplifying existing MS workflows. The rapid development of 3D printing technology has enabled direct fabrication of microfluidic channels using consumer grade 3D printers, which holds great promise to facilitate the adoption of microfluidic devices by the MS community. However, photo polymerization-based 3D printed devices have an issue with chemical leeching, which can introduce contaminant molecules that may present as isobaric ions and/or severely suppress the ionization of target analytes when combined with MS analysis. Although extra cure and washing steps have alleviated the leeching issue, many such contaminant peaks can still show up in mass spectra. In this work, we report a simple surface modification strategy to isolate the chemical leachates from the channel solution thereby eliminating the contaminant peaks for MS analysis. The channel was prepared by fabricating a layer of polydimethylsiloxane graft followed by wetting the graft using silicone oil. The resulting liquid infused surface (LIS) showed significant reduction in contaminant peaks and improvement in the signal intensity of target analytes. The coating showed good stability after long-term usage (7 days) and long-term storage (∼6 months). Finally, the utility of the coating strategy was demonstrated by printing herringbone microfluidic mixers for studying fast reaction kinetics, which obtained comparable reaction rates to literature values. The effectiveness, simplicity, and stability of the present method will promote the adoption of 3D printed microdevices by the MS community.

3D-printed chemiluminescence flow cells with customized cross-section geometry for enhanced analytical performance

Low force stereolithography is exploited for the first time for one-step facile fabrication of chemiluminescence (CL) flow-through cells that bear unrivalled features as compared to those available through milling or blowing procedures or alternative 3D printing technologies. A variety of bespoke cross-section geometries with polyhedral features (namely, triangular, square, and five-side polygon) as well as semicircular cross-section are herein critically evaluated in terms of analytical performance against the standardcircular cross-section in a flat spirally-shape format. The idea behind is to maximize capture of elicited light by the new designs while leveraging 3D printing further for fabrication of (i) customized gaskets that enable reliable attaching of the active mixing zone of the CL cell to the detection window, (ii) in-line 3D-printed serpentine reactors, and (iii) flow confluences with tailorable shapes for enhancing mixing of samples with CL reagents. Up to twenty transparent functional cells were simultaneously fabricated without inner supports following post-curing and surface treatment protocols lasting less than 5 h. In fact, previous attempts to print spirally-shaped cells in one-step by resorting to less cost effective photopolymer inkjet printing technologies were unsuccessful because of the requirement of lengthy procedures (>15 days) for quantitative removal of the support material. By exploiting the phthalazinedione-hydrogen peroxide chemistry as a model reaction, the five-side irregular pentagon cell exhibited superior analytical figures of merit in terms of LOD, dynamic range and intermediate precision as compared to alternative designs. Computational fluid dynamic simulations for mapping velocities at the entry region of the spiral cell corroborated the fact that the 5-side polygon cross-section flow-cell with Y-type confluence permitted the most efficient mixing of reagents and sample while enabling larger flow velocities near the inlet that contribute to a more efficient capture of the photons from the flash-type reaction. The applicability of the 3D-printed 5-side polygon CL cell for automatic determination of hydrogen peroxide using a computerized hybrid flow system was demonstrated for the analysis of high matrix samples, viz., seawater and saliva, with relative recoveries ranging from 83 to 103%.

Flexible material formulations for 3D printing of ordered porous beds with applications in bioprocess engineering

BACKGROUND

3D printing is revolutioning many industrial sectors and has the potential to enhance also the biotechnology and bioprocessing fields. Here, we propose a new flexible material formulation to 3D print support matrices with complex, perfectly ordered morphology and with tuneable properties to suit a range of applications in bioprocess engineering.

FINDINGS

Supports were fabricated using functional monomers as the key ingredients, enabling matrices with bespoke chemistry, such as charged groups, chemical moieties for further functionalization, and hydrophobic/hydrophilic groups. Other ingredients, e.g. crosslinkers and porogens, can be employed to fabricate supports with diverse characteristics of their porous network, providing an opportunity to further regulate the mechanical and mass transfer properties of the supports. Through this approach, we fabricated and demonstrated the operation of Schoen gyroid columns with (I) positive and negative charges for ion exchange chromatography, (II) enzyme bioreactors with immobilized trypsin to catalyse hydrolysis, and (III) bacterial biofilm bioreactors for fuel desulphurization.

CONCLUSIONS

This study demonstrates a simple, cost-effective, and flexible fabrication of customized 3D printed supports for different biotechnology and bioengineering applications.

On the potential use of two-photon polymerization to 3D print chromatographic packed bed supports

The continuous quest for chromatographic supports offering kinetic performance properties superior to that of the packed bed of spheres has pushed the field to consider alternative formats such as for example monolithic and pillar array columns. This quest seems bound to culminate in the use of 3D printing technology, as this intrinsically offers the possibility to produce supports with a perfect uniformity and with a size and shape that is fully optimized for the chromatographic separation process. However, to be competitive with the current state-of-the-art, structures with sub-micron feature sizes are required. The present contribution therefore investigates the use of the 3D printing technology with the highest possible resolution available today, i.e., two-photon polymerization (2PP). It is shown that 2PP printing is capable of achieving the required ≤ 1 µm printing resolution. Depending on the laser scan speed, the lower limit through-pore size for a tetrahedral skeleton monolith with a theoretical 80% external porosity was found to be at 800 nm, when printing at a scan speed of 50 mm/s with a laser power of 10%. For a scan speed of 10 mm/s, the minimal through-pore size dropped to 500 nm. However, this very high resolution comes at the cost of excessively long printing times. The total printing time for a column volume equivalent to that of a typical nano-LC column (75 µm i.d. cylindrical tube with length L = 15 cm) has been determined to correspond to 330 and 470 h for the 50 mm/s and the 10 mm/s scan speed respectively. Other issues remaining to be solved are the need to clad the printed skeleton with a suitable mesoporous layer for chromatographic retention and the need to add a top-wall to the printed channels after the removal of the non-polymerized resin. It is therefore concluded that 2PP printing is not ready yet to replace the existing column fabrication methods.

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.

3D printing in biotechnology-An insight into miniaturized and microfluidic systems for applications from cell culture to bioanalytics

Since its invention in the 1980s, 3D printing has evolved into a versatile technique for the additive manufacturing of diverse objects and tools, using various materials. The relative flexibility, straightforwardness, and ability to enable rapid prototyping are tremendous advantages offered by this technique compared to conventional methods for miniaturized and microfluidic systems fabrication (such as soft lithography). The development of 3D printers exhibiting high printer resolution has enabled the fabrication of accurate miniaturized and microfluidic systems-which have, in turn, substantially reduced both device sizes and required sample volumes. Moreover, the continuing development of translucent, heat resistant, and biocompatible materials will make 3D printing more and more useful for applications in biotechnology in the coming years. Today, a wide variety of 3D-printed objects in biotechnology-ranging from miniaturized cultivation chambers to microfluidic lab-on-a-chip devices for diagnostics-are already being deployed in labs across the world. This review explains the 3D printing technologies that are currently used to fabricate such miniaturized microfluidic devices, and also seeks to offer some insight into recent developments demonstrating the use of these tools for biotechnological applications such as cell culture, separation techniques, and biosensors.

PolyJet printed high aspect ratio three-dimensional bifurcating microfluidic flow distributor and its application in solid-phase extraction

Microfluidic distributors that can uniformly distribute fluid from a single channel to multiple channels and into, or across, 3D spaces and vice versa has always represented a challenge. Recently, significant interest has been observed in 3D printing three-dimensional flow distributors. However, they either lack their use at low flow rates or in high aspect ratio environments, which are usually encountered in various applications, such as generating organs-on-a-chip, chromatographic columns, solid-phase extractors, etc. Hence, herein, a three-dimensional bifurcating microfluidic distributor that can be used in both low flow rate and high aspect ratio environments has been designed and developed using PolyJet printing. A 1:4 aspect ratio distributor has been developed with 64 exit channels (array of 16 X 4), however, it can be easily customised to modulate both the aspect ratio and the number of exit channels (in the order of 2). Computational fluid dynamic (CFD) simulation of 0.2 and 0.1 mL min^-1 flow through the distributor recorded a maldistribution factor of only 2.29% and 1.72%, respectively. The distributor has resulted in low-dispersion divergence and convergence of flow to and from 64 parallel channels while operating at flow rates ranging from 0.25 mL min^-1 to 2 mL min^-1. It has been further used to develop a high-performance online solid-phase extractor. The extractor was designed with the three-dimensional bifurcating distributor based inlet and outlet and a packed bed of 15 × 20 × 8 mm (length × breadth × height), which resulted in extraction efficiency of 88.8% ± 0.3. In comparison, the extraction efficiency of 81.1% ± 1.1 and 70.4% ± 0.8 was obtained with its two-dimensional distributor and single-channel inlet and outlet based counterparts, respectively.

4D-Printed Temperature-Controlled Flow-Actuated Solid-Phase Extraction Devices

Four-dimensional printing (4DP) technologies can extend the functionality and applicability of manufactured analytical devices through employing stimuli-responsive materials. In this study, we used a photocurable resin of stimuli-responsive shape-memory polymers and digital light processing three-dimensional printing (3DP) to fabricate a smart sample pretreatment device featuring a solid-phase extraction (SPE) column and a temperature-controlled flow-actuated valve. Through manipulation of the temperatures and flow rates of the sample, eluent, and rinsing streams, we used this 4D-printed SPE device to extract Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from high-salt content samples and remove the sample matrix prior to their determination by inductively coupled plasma mass spectrometry. After optimizing the valve design and operation and the analytical scheme, this device displayed competitive analytical performance-the method detection limits (MDLs) ranged from 0.7 to 22.1 ng L^-1 for these metal ions (the MDLs ranged from 0.5 to 18.8 ng L^-1 when validating the same printed SPE column using an online automatic system equipped with electric switching valves). Furthermore, we performed analyses of these metal ions in three reference materials (CASS-4, 1643f, and 2670a) and spike analyses of collected samples (seawater, ground water, river water, and human urine) to confirm the reliability and applicability of this analytical method. For the first time, 4DP has been used to fabricate a multi-functional, stimuli-responsive sample pretreatment device displaying analytical performance equal to that of a commercial apparatus. This novel approach builds upon the functionality and diversity of 3DP-enabling devices with the goal of developing more efficient analytical schemes.

Determination of anabolic androgenic steroids in dietary supplements and external drugs by magnetic solid-phase extraction combined with high-performance liquid chromatography-tandem mass spectrometry

The widespread abuse of anabolic androgenic steroids by healthy people leads to the risk of major mood disorders and heart failure; thus, the determination of anabolic androgenic steroids is vital. In this study, 17 anabolic androgenic steroids in dietary supplements and external drugs were identified, and their concentration was determined. For this purpose, polyaniline-coated magnetic nanoparticles were prepared and then subjected to magnetic solid-phase extraction combined with high-performance liquid chromatography-tandem mass spectrometry. The experimental parameters of magnetic solid-phase extraction were studied in detail, and the optimal conditions were established. Under the optimal conditions, the limits of detection were in the range of 0.001-0.02 μg/L, with relative standard deviations of 5.52-11.6% (n = 7) for all the steroids, and the enrichment factors were in the range of 20.0-24.8. The developed method was then successfully applied for the determination of 17 anabolic androgenic steroids in real samples, and dehydroepiandrosterone (prasterone) was detected in a commercially available external drug.

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.

Digital Manufacturing for Microfluidics

The microfluidics field is at a critical crossroads. The vast majority of microfluidic devices are presently manufactured using micromolding processes that work very well for a reduced set of biocompatible materials, but the time, cost, and design constraints of micromolding hinder the commercialization of many devices. As a result, the dissemination of microfluidic technology-and its impact on society-is in jeopardy. Digital manufacturing (DM) refers to a family of computer-centered processes that integrate digital three-dimensional (3D) designs, automated (additive or subtractive) fabrication, and device testing in order to increase fabrication efficiency. Importantly, DM enables the inexpensive realization of 3D designs that are impossible or very difficult to mold. The adoption of DM by microfluidic engineers has been slow, likely due to concerns over the resolution of the printers and the biocompatibility of the resins. In this article, we review and discuss the various printer types, resolution, biocompatibility issues, DM microfluidic designs, and the bright future ahead for this promising, fertile field.

Use of Nanomaterial-Based (Micro)Extraction Techniques for the Determination of Cosmetic-Related Compounds

The high consumer demand for cosmetic products has caused the authorities and the industry to require rigorous analytical controls to assure their safety and efficacy. Thus, the determination of prohibited compounds that could be present at trace level due to unintended causes is increasingly important. Furthermore, some cosmetic ingredients can be percutaneously absorbed, further metabolized and eventually excreted or bioaccumulated. Either the parent compound and/or their metabolites can cause adverse health effects even at trace level. Moreover, due to the increasing use of cosmetics, some of their ingredients have reached the environment, where they are accumulated causing harmful effects in the flora and fauna at trace levels. To this regard, the development of sensitive analytical methods to determine these cosmetic-related compounds either for cosmetic control, for percutaneous absorption studies or for environmental surveillance monitoring is of high interest. In this sense, (micro)extraction techniques based on nanomaterials as extraction phase have attracted attention during the last years, since they allow to reach the desired selectivity. The aim of this review is to provide a compilation of those nanomaterial-based (micro)extraction techniques for the determination of cosmetic-related compounds in cosmetic, biological and/or environmental samples spanning from the first attempt in 2010 to the present.

3D printed fluidic platform with in-situ covalently immobilized polymer monolithic column for automatic solid-phase extraction

In this work, 3D stereolithographic printing is proposed for the first time for the fabrication of fluidic devices aimed at in-situ covalent immobilization of polymer monolithic columns. Integration in advanced flow injection systems capitalized upon programmable flow was realized for fully automatic solid-phase extraction (SPE) and clean-up procedures as a 'front-end' to on-line liquid chromatography. The as-fabricated 3D-printed extraction column devices were designed to tolerate the pressure drop of forward-flow fluidic systems when handling large sample volumes as demonstrated by the determination of anti-microbial agents, plastic additives and monomers as models of emerging contaminants (4-hydroxybenzoic acid, methylparaben, phenylparaben, bisphenol A and triclosan). Decoration of the monolithic phase with gold nanoparticles (AuNPs) was proven most appropriate for the enrichment of phenolic-type target compounds. In particular, the absolute recoveries for the tested analytes ranged from 73 to 92% both in water and saliva samples. The 3D printed composite monolith showed remarkable analytical features in terms of loading capacity (2 mg g-1), breakthrough volume (10 mL), satisfactory batch-to-batch reproducibility (<9% RSD), and easy on-line coupling of the SPE device to HPLC systems. The fully automatic 3D-printed SPE-HPLC hyphenated system was also exploited for the on-line extraction, matrix clean-up and determination of triclosan in 200 μL of real saliva samples.

Electrode modified with graphene quantum dots supported in chitosan for electrochemical methods and non-linear deconvolution of spectra for spectrometric methods: approaches for simultaneous determination of triclosan and methylparaben

Two analytical methods were developed using electrochemical and spectrometric techniques for the simultaneous determination of endocrine disruptors triclosan and methylparaben in the monitoring of personal care products. For the electroanalytical analyses, a sensitive electrode based on graphene quantum dots supported in chitosan was employed. Under optimized conditions and a working potential of typically + 0.60 V for triclosan and + 0.81 V (vs. Ag/AgCl) for methylparaben, the calibration plots obtained by differential pulse voltammetry were linear in the range 0.10 to 10.0 μmol L^-1. The detection limits were 0.03 and 0.04 μmol L^-1 for triclosan and methylparaben, respectively. For the spectrometric method, UV/VIS spectrometry was used with a mathematical processing of non-linear deconvolution. This processing was used to solve the problem of overlapping absorption bands of triclosan (282 nm) and methylparaben (257 nm), which enabled simultaneous determination. The calibration plots by UV/VIS spectrometry were linear in the range 1.0 to 14.0 μmol L^-1 with detection limits of 0.42 and 0.37 μmol L^-1, respectively, for triclosan and methylparaben. Similar results obtained from the calibration plots of individual analytes suggest that the methods can be applied for individual or simultaneous determination of these species. Both methods were employed in the analysis of five samples of personal care products: toothpaste, antiseptic soap, antiseptic deodorant, shampoo, and a bath kit (soap and shampoo). The statistical tests indicated that there were no significant differences regarding the accuracy and precision of the data provided by the two methods described herein. Graphical abstract Schematic representation for simultaneous determination of triclosan and methylparaben: electrochemical method employing an electrode modified with graphene quantum dots supported in chitosan and spectrometric method applying a non-linear deconvolution of spectrum.

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.

Microextraction approaches for bioanalytical applications: An overview

Biological samples are usually complex matrices due to the presence of proteins, salts and a variety of organic compounds with chemical properties similar to those of the target analytes. Therefore, sample preparation is often mandatory in order to isolate the analytes from troublesome matrices before instrumental analysis. Because the number of samples in drug development, doping analysis, forensic science, toxicological analysis, and preclinical and clinical assays is steadily increasing, novel high throughput sample preparation approaches are calling for. The key factors in this development are the miniaturization and the automation of the sample preparation approaches so as to cope with most of the twelve principles of green chemistry. In this review, recent trends in sample preparation and novel strategies will be discussed in detail with particular focus on sorptive and liquid-phase microextraction in bioanalysis. The actual applicability of selective sorbents is also considered. Additionally, the role of 3D printing in microextraction for bioanalytical methods will be pinpointed.

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.

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.