The Automation Technique Lab-In-Syringe: A Practical Guide

A continuous flow polyurethane foam solid phase microextraction lab-in-syringe platform for the automatic determination of toxic metals

A novel fully automatic continuous flow polyurethane foam solid phase microextraction lab-in-syringe system for on-line sample preconcentration/separation has been developed as a front-end to flame atomic absorption spectrometry. For the first time lab-in-syringe in continuous flow has been adopted for the determination of toxic metals. The microextraction procedure was performed after on-line metal complexation with ammonium pyrrolidine dithiocarbamate, while the elution was conducted by 400 μL of methyl isobutyl ketone. The main chemical and hydrodynamic factors that affected the performance of the method were optimized using Cd and Pb as model analytes. For 90 s preconcentration time, the limits of the detection were 0.20 and 1.7 μg L-1 for Cd and Pb, respectively, while the enhancement factors were 79 for Cd and 150 for Pb. The relative standard deviation% values were lower than 2.8 % for all analytes. As a proof-of-concept the proposed system was used for environmental water analysis, providing relative recoveries within the range of 94.0 and 104.4 %. The Green Analytical Procedure Index and Blue Applicability Grade Index proved reduced environmental impact and high practicality for the proposed method.

A flow-batch lab-in-syringe foam microextraction platform for the simultaneous preconcentration and in situ membraneless gas-liquid separation of mercury prior to cold vapor atomic absorption spectrometry

Herein, the proof-of-concept of a novel lab-in-syringe (LIS) foam microextraction platform is presented as a front-end to cold vapor atomic absorption spectrometry (CVAAS) for the simultaneous preconcentration and membraneless gas-liquid separation (GLS) of inorganic mercury in biological samples. The proposed method is based on the on-line formation of the ammonium pyrrolidine dithiocarbamate complex with mercury that was retained in the pores of polyurethane foam immobilized on the piston of the LIS system. Metal complex elution and in situ mercury vapor generation are accomplished inside the microsyringe in a flow-batch format, while the separation of vapor species is achieved via the membraneless GLS found at the top of the syringe's barrel. Under optimized operation conditions, for 90 s preconcentration time, the limit of detection was 0.02 μg L-1 and the repeatability (RSD) was 3.8% (at the 0.5 μg L-1 concentration level), within a working range extending up to 4.0 μg L-1. The practicality of the novel manifold was demonstrated using the Blue Applicability Grade Index, while the accuracy of the method was evaluated using certified reference materials and spiked samples.

An integrated automatic lab-in-syringe sol-gel coated foam microextraction platform as a front-end to high performance liquid chromatography for the migration studies of bisphenol A

The proof-of-concept of an integrated automatic foam microextraction lab-in-syringe (FME-LIS) platform coupled to high performance liquid chromatography is presented. Three different sol-gel coated foams were synthesized, characterized, and conveniently packed inside the glass barrel of the LIS syringe pump, as an alternative approach for sample preparation, preconcentration and separation. The proposed system efficiently combines the inherent benefits of lab-in-syringe technique, the good features of sol-gel sorbents, the versatile nature of foams/sponges, as well as the advantages of automatic systems. Bisphenol A (BPA) was used as model analyte, due to the increasing concern for the migration of this compound from household containers. The main parameters that affect the extraction performance of the system were optimized and the proposed method was validated. The limit of detection for BPA were 0.5 and 2.9 μg L^-1, for a sample volume of 50 mL and 10 mL, respectively. The intra-day precision was <4.7% and the inter-day precision was <5.1% in all cases. The performance of the proposed methodology was evaluated for the migration studies of BPA using different food simulants, as well as for the analysis of drinking water. Good method applicability was observed based on the relative recovery studies (93-103%).

Lab-in-syringe automated protein precipitation and salting-out homogenous liquid-liquid extraction coupled online to UHPLC-MS/MS for the determination of beta-blockers in serum

A sample preparation method involving tandem implementation of protein precipitation and salting-out homogenous liquid-liquid extraction was developed for the determination of beta-blockers in serum. The entire procedure was automated using a computer-controlled syringe pump following the Lab-In-Syringe approach. It is based on the denaturation of serum proteins with acetonitrile followed by salt-induced phase separation upon which the proteins accumulate as a compact layer at the interphase of the solutions. The extract is then separated and diluted in-syringe before being submitted to online coupled UHPLC-MS/MS. A 1 mL glass syringe containing a small stir bar for solution mixing at up to 3000 rpm, was used to deal with sample volumes as small as 100 μL. A sample throughput of 7 h^-1 was achieved by performing the chromatographic run and sample preparation procedure in parallel. Linear working ranges were obtained for all analytes between 5 and 100 ng mL^-1, with LOD values ranging from 0.4 to 1.5 ng mL^-1. Accuracy values in the range of 88.2-106% and high precision of <11% RSD suggest applicability for routine analysis that can be further improved using deuterated standards.

Lab-in-Syringe, a Useful Technique for the Analysis and Detection of Pollutants of Emerging Concern in Environmental and Food Samples

Lab-in-syringe is a new approach for the integration of various analytical extraction steps inside a syringe. Fully automated dispersive liquid-liquid microextraction is carried out in-syringe using a very simple instrumental setup. Dispersion is achieved by aspiration of the organic phase and then the watery phase into the syringe as rapidly as possible. After aggregation of the solvent droplets, the organic phase is pushed towards the detector allowing a highly sensitive spectrophotometric or fluorimetric detection. This technique is very useful not only for the preconcentration of analyte, but also for the elimination of their interferences. In this work, its application is described using solvents that are lighter and denser than water. The magnetically assisted variant and its coupling to different instruments has been also described with the aim of increasing the resolution of complex samples, especially useful for the determination of emerging contaminants.

Dual Lab-in-Syringe Flow-Batch Platform for Automatic Fabric Disk Sorptive Extraction/Back-extraction as a Front End to Inductively Coupled Plasma Atomic Emission Spectrometry

A novel dual lab-in-syringe flow-batch (D-LIS-FB) platform for automatic fabric-disk-in-syringe sorptive extraction followed by oxidative back-extraction as a front end to inductively coupled plasma atomic emission spectrometry (ICP-AES) is presented for the first time. Sol-gel poly(caprolactone)-poly(dimethylsiloxane)-poly(caprolactone)-coated polyester fabric disks were packed at the top of the glass barrel of a microsyringe pump as an alternative to column preconcentration. Herein lie multiple significant advantages including effectiveness, compactness, lower back-pressure, and lower time of analysis. Copper, lead, and cadmium were used as model analytes for the exploration of the capabilities of the developed platform. The online retained metal-diethyldithiophosphate complexes were eluted using diisopropyl ketone prior to atomization. Undesirable incompatibility of organic solvents for direct injection into the ICP-AES system was overcome ingeniously in a flow manner by oxidative back-extraction of the analytes utilizing a second lab-in-syringe setup. Following its optimization, the D-LIS-FB platform showed excellent linearity, in combination with good method precision (i.e., RSD < 3.4%) and trueness. Moreover, the limits of detection were 0.25 μg L^-1 for Cd(II), 0.13 μg L^-1 for Cu(II), and 0.37 μg L^-1 for Pb(II), confirming the applicability of the proposed system for metal analysis at trace levels. As a proof-of-concept, the developed versatile system was utilized for the analysis of different environmental, food, and biological samples.

Nanofibrous Online Solid-Phase Extraction Coupled with Liquid Chromatography for the Determination of Neonicotinoid Pesticides in River Waters

Polymeric nano- and microfibers were tested as potential sorbents for the extraction of five neonicotinoids from natural waters. Nanofibrous mats were prepared from polycaprolactone, polyvinylidene fluoride, polystyrene, polyamide 6, polyacrylonitrile, and polyimide, as well as microfibers of polyethylene, a polycaprolactone nano- and microfiber conjugate, and polycaprolactone microfibers combined with polyvinylidene fluoride nanofibers. Polyimide nanofibers were selected as the most suitable sorbent for these analytes and the matrix. A Lab-In-Syringe system enabled automated preconcentration via online SPE of large sample volumes at low pressure with analyte separation by HPLC. Several mat layers were housed in a solvent filter holder integrated into the injection loop of an HPLC system. After loading 2 mL sample on the sorbent, the mobile phase eluted the retained analytes onto the chromatographic column. Extraction efficiencies of 68.8–83.4% were achieved. Large preconcentration factors ranging from 70 to 82 allowed reaching LOD and LOQ values of 0.4 to 1.7 and 1.2 to 5.5 µg·L⁻¹, respectively. Analyte recoveries from spiked river waters ranged from 53.8% to 113.3% at the 5 µg·L⁻¹ level and from 62.8% to 119.8% at the 20 µg·L⁻¹ level. The developed methodology proved suitable for the determination of thiamethoxam, clothianidin, imidacloprid, and thiacloprid, whereas matrix peak overlapping inhibited quantification of acetamiprid.

Lab-In-Syringe automation of deep eutectic solvent-based direct immersion single drop microextraction coupled online to high-performance liquid chromatography for the determination of fluoroquinolones

Lab-In-Syringe direct immersion single drop microextraction is proposed as an automated sample pretreatment methodology and coupled online to HPLC with fluorescence detection for the determination of fluoroquinolones in environmental waters. For the first time, a drop of a natural deep eutectic solvent (NADES), synthesized from hexanoic acid and thymol, has been used as an extractant in automated single-drop microextraction. The extraction procedure was carried out within the 5 mL void of an automatic syringe pump. A 9-position head valve served the aspiration of all required solutions, air, waste disposal, and hyphenation with the HPLC instrument. Sample mixing during extraction was done by a magnetic stirring bar placed inside the syringe. Only 60 μL of NADES were required omitting toxic classical solvents and improving the greenness of the proposed methodology. By direct injection, linear working ranges between 0.1 and 5 μg L^-1 were achieved for all fluoroquinolones. The limit of quantification values and enrichment factors ranged from 20 ng L^-1 to 30 ng L^-1 and 35 to 45, respectively. Accuracies obtained from the analysis of spiked surface water and wastewater treatment plant effluent analysis at two concentration levels (0.5 and 4 μg L^-1) ranged from 84.6% to 119.7%, with RSD values typically <3%.

Chemical Derivatization in Flow Analysis

Chemical derivatization for improving selectivity and/or sensitivity is a common practice in analytical chemistry. It is particularly attractive in flow analysis in view of its highly reproducible reagent addition(s) and controlled timing. Then, measurements without attaining the steady state, kinetic discrimination, exploitation of unstable reagents and/or products, as well as strategies compliant with Green Analytical Chemistry, have been efficiently exploited. Flow-based chemical derivatization has been accomplished by different approaches, most involving flow and manifold programming. Solid-phase reagents, novel strategies for sample insertion and reagent addition, as well as to increase sample residence time have been also exploited. However, the required alterations in flow rates and/or manifold geometry may lead to spurious signals (e.g., Schlieren effect) resulting in distorted peaks and a noisy/drifty baseline. These anomalies can be circumvented by a proper flow system design. In this review, these aspects are critically discussed mostly in relation to spectrophotometric and luminometric detection.

Data-Centric Architecture for Self-Driving Laboratories with Autonomous Discovery of New Nanomaterials

Artificial intelligence (AI) approaches continue to spread in almost every research and technology branch. However, a simple adaptation of AI methods and algorithms successfully exploited in one area to another field may face unexpected problems. Accelerating the discovery of new functional materials in chemical self-driving laboratories has an essential dependence on previous experimenters' experience. Self-driving laboratories help automate and intellectualize processes involved in discovering nanomaterials with required parameters that are difficult to transfer to AI-driven systems straightforwardly. It is not easy to find a suitable design method for self-driving laboratory implementation. In this case, the most appropriate way to implement is by creating and customizing a specific adaptive digital-centric automated laboratory with a data fusion approach that can reproduce a real experimenter's behavior. This paper analyzes the workflow of autonomous experimentation in the self-driving laboratory and distinguishes the core structure of such a laboratory, including sensing technologies. We propose a novel data-centric research strategy and multilevel data flow architecture for self-driving laboratories with the autonomous discovery of new functional nanomaterials.

Lab-In-Syringe with Bead Injection Coupled Online to High-Performance Liquid Chromatography as Versatile Tool for Determination of Nonsteroidal Anti-Inflammatory Drugs in Surface Waters

We report on the hyphenation of the modern flow techniques Lab-In-Syringe and Lab-On-Valve for automated sample preparation coupled online with high-performance liquid chromatography. Adopting the bead injection concept on the Lab-On-Valve platform, the on-demand, renewable, solid-phase extraction of five nonsteroidal anti-inflammatory drugs, namely ketoprofen, naproxen, flurbiprofen, diclofenac, and ibuprofen, was carried out as a proof-of-concept. In-syringe mixing of the sample with buffer and standards allowed straightforward pre-load sample modification for the preconcentration of large sample volumes. Packing of ca. 4.4 mg microSPE columns from Oasis HLB^® sorbent slurry was performed for each sample analysis using a simple microcolumn adapted to the Lab-On-Valve manifold to achieve low backpressure during loading. Eluted analytes were injected into online coupled HPLC with subsequent separation on a Symmetry C18 column in isocratic mode. The optimized method was highly reproducible, with RSD values of 3.2% to 7.6% on 20 µg L^-1 level. Linearity was confirmed up to 200 µg L^-1 and LOD values were between 0.06 and 1.98 µg L^-1. Recovery factors between 91 and 109% were obtained in the analysis of spiked surface water samples.

Automated liquid-liquid microextraction and determination of sulfonamides in urine samples based on Schiff bases formation in natural deep eutectic solvent media

In this work, an automated liquid-liquid microextraction procedure for the determination of sulfonamides (sulfamethoxazole, sulfamethazine and sulfapyridine) in urine samples using natural deep eutectic solvent is presented for the first time. The mechanism for extraction of sulfonamides was based on the formation of colored Schiff bases in the presence of vanillin, which acted as a derivatization reagent and precursor of natural deep eutectic solvent (an extractant). In this procedure, thymol was used as both media for Schiff bases formation and as a second precursor of the natural deep eutectic solvent. The formation of the Schiff bases was confirmed by mass spectrometry. A Lab-In-Syringe concept was applied for the automation of the microextraction procedure. The procedure involved mixing the sample and natural deep eutectic solvent into a syringe of a flow system, formation and microextraction of colored Schiff base followed by UV-Vis detection. Under optimal automated conditions the limits of detection, calculated from a blank test based on 3s (sigma) were 0.06, 0.1, and 0.06 mg L^-1 for sulfapyridine, sulfamethoxazole and sulfamethazine. The proposed automated procedure permitted the routine determination of one drug (sulfamethoxazole, sulfamethazine or sulfapyridine) in urine samples to be achieved in less than 10 min.

The emerging role of 3D-printing in ion mobility spectrometry and mass spectrometry

3D-printing is revolutionizing the rapid prototyping in analytical chemistry. In the last few years, we observed the development of 3D-printed components for ion studies, such as ion sources, ion transfer and ion mobility spectrometry (IMS) devices. Often, 3D-printed gadgets add functions to existing mass spectrometry (MS) systems. Custom adapters improve the sensibility for coupling with ambient ionization and upstream chromatography methods, and sample preparation units optimize the following MS analyses. Besides, 3D-printer parts are suitable for constructing custom analytical robots and mass imaging systems. Some of those assemblies implement new concepts and are commercially not available. An essential aspect of using 3D-printing is the fast turnover of design improvements, which is motivated by permissive licenses. The easy reproducibility and exchange of ideas lead to a community-driven development, which is accompanied by economic advantages for public research and education.

Selective neutrophil activation via a programmable stopped-flow injection approach: Multiple evidences of priming state of salivary polymorphonuclear neutrophils compared to circulatory polymorphonuclear neutrophils

Activated polymorphonuclear neutrophils play an important role in host defense system against invading pathogens via releasing reactive oxygen species through respiratory bursts. Nowadays, neutrophil activation process has been found to be modeled as a two-stages continuum from dormant to primed, and to fully activated. Although the differences of salivary and circulatory neutrophils have been investigated in various experimental designs, priming state of salivary polymorphonuclear neutrophils with respiratory burst has not been comprehensively studied. Here, for the first time so far, a programmable flow injection analysis based on Stop in Flow Cell operation mode has been applied to batch analyzing comparative study of neutrophil activation. The high-sensitivity luminol-dependent chemiluminescence assay has been employed with just 330 μL of cell suspension consumption per sample, and the process has been conducted rapidly and efficiently within 15 min to keep the neutrophils viability. ROS from either unstimulated or substimulated or stimulated salivary polymorphonuclear neutrophils, in comparison with those from autologous circulatory polymorphonuclear neutrophils, have been determined, together with further monitoring the impact of extracellular and intracellular calcium ion (Ca²⁺) on neutrophils ROS generation. Conclusively, the priming state of salivary polymorphonuclear neutrophils during activation has been testified from multiple aspects.

Automatic multicommuted flow systems applied in sample treatment for radionuclide determination in biological and environmental analysis

The presence of artificial and natural radioactivity in the environment is currently a topic of great relevance and ecological interest, even in human health issue, due to the increase of different anthropogenic activities. The use of multicommuted flow analysis techniques (e.g. Multi-Syringe Flow Injection Analysis - MSFIA, Lab-On-Valve - LOV and Lab-In-Syringe - LIS) has allowed the automation of radiochemical procedures to separate and preconcentrate radionuclides in environmental and biological samples. In comparison with the manual approach commonly used in routine analysis for radioactivity monitoring, the automation has enabled the development of highly reproducible methodologies with a great analysis frequency. Moreover, during the analytical procedure, the intervention of the analyst is drastically reduced, minimizing the radiological risk. The automation also offers significant advantages such as minimum consumption of time and reagents, reducing the cost and the generation of waste, contributing to the green chemistry. In this review, several multicommuted flow analysis techniques (MSFIA, LOV and LIS) reported in the last decade applied for the development of automatic sample treatment methodologies, used to separate, preconcentrate and quantify ⁹⁰Sr, ⁹⁹Tc, natural U and ²²⁶Ra in biological and environmental samples are described and critically compared.

Modern Flow Analysis

A brief overview of articles published in this Special Issue of Molecules titled “Modern Flow Analysis” is provided. In addition to cross-sectional and methodological works, there are some reports on new technical and instrumental achievements. It has been shown that all these papers create a good picture of contemporary flow analysis, revealing the most current trends and problems in this branch of flow chemistry.