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 compact flow-batch analyzer equipped with mini piezoelectric pumps and image-based volume control

Flow-batch analyzers demand meticulous volume control for successful application in quantitative determinations, with the incorporation of high-efficiency pumps and valves recommended for their construction. However, routine recalibrations are frequently needed to uphold the accuracy of manipulated volumes, highlighting the value of exploring new alternatives for volume control and measurement, with less sophisticated apparatus. In this work a compact Flow-Batch (FB) analyzer with piezoelectric micropumps was developed to perform standard addition calibration, incorporating image-based detection to perform volume control. The instrument was evaluated by quantitatively determining Cr(VI), NO2-, and Fe(II) in water samples, combining RGB-based colorimetry with established spectrophotometric methods. The results demonstrate that a comprehensive analysis with five standard additions can be completed in approximately 10 minutes, maintaining a suitable linear correlation (R2 > 0.99) and precision (0.4 ≤ RSD ≤ 12.1%). Recoveries between 90% and 105% for analyte levels below Brazilian regulatory limits underscore the accuracy of the proposed approach. The study confirms that digital image monitoring provides an elegant alternative for controlling solution volumes in FB systems, eliminating the need for more robust pumps with precisely controlled flow rates.

Automated liquid-liquid deep eutectic solvents based microextraction procedure for determination of acrylamide in foodstuffs by high-performance liquid chromatography with ultraviolet detection

For the rapid and efficient determination of acrylamide in food products by HPLC-UV, an environmentally friendly analytical approach has been developed, including liquid-phase extraction and subsequent liquid-liquid microextraction using a deep eutectic solvent. To automate the procedure, the flow-through "lab in a syringe" method was used. Acrylamide is considered a potential endocrine disrupting chemical and its main source is fried foods, which are widely consumed by both children and adults. To extract and concentrate acrylamide, hydrophobic deep-eutectic solvents based on various carboxylic acids and natural terpenoids were studied for the first time. It was found that benzoic acid, as a precursor of the extraction solvent, promotes the transfer of hydrophilic acrylamide from the aqueous phase of the sample due to the interaction of carboxyl and amide groups. The procedure has been validated and used effectively to estimate acrylamide content in beetroot and corn chips. Under optimal conditions, the detection limit was 0.01 mg/kg. Unlike existing methods, the proposed method is fully automated, does not require hazardous organic solvents and additional derivatization stages, and at the same time allows the determination of acrylamide at a level below established standards.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05999-x.

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.

Aggregation-induced enhancement of peroxidase-mimetic activity of DNAzyme-gold nanoparticles for ultrasensitive detection of lead ions

Lead ion (Pb2+) detection is critically important in environmental protection and health management. In this work, we developed a simple signal-enhanced colorimetric sensor for the detection of Pb2+ based on the peroxidase-mimetic property of gold nanoparticles (AuNPs). When a certain concentration of Pb2+ was added to a solution of DNAzyme-modified AuNPs, aggregation was triggered, and the result was an enhancement of the peroxidase-mimetic activity of AuNPs. Then, the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) by the catalyst of AuNPs was used for the sensitive UV-Vis and colorimetric detection of Pb2+. When a higher concentration of Pb2+ was added, the greater amount of aggregation of AuNPs resulted in the enhancement of the UV-Vis adsorption of the solution at 652 nm, with a deepening of the blue color of the solution. After optimization of the experimental conditions, a linear relationship between the absorbance of oxidized TMB at 652 nm and the logarithm of Pb2+ concentration was obtained, which had been divided into two parts (25 pM to 2.5 μM, and 2.5 μM to 250 μM). The detection limit was as low as 10 pM. The satisfactory specificity and rapid response of the sensor showed that it has promising application for the detection of Pb2+ in real 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%).

A review of bioanalytical applications of microextraction techniques combined with derivatization

Microextraction techniques have attracted the attention of many researchers working in the field of bioanalysis due to their unique advantages, mainly in downsizing the scale of sample preparation steps. In parallel, analytical derivatization offers a powerful combination in terms of additional sensitivity, selectivity and compatibility with modern separation techniques. The aim of this review is to discuss the most recent advances in bioanalytical sample preparation based on the combination of microextraction and analytical derivatization. Both innovative fundamental reports and analyte-targeted applications are included and discussed. Dispersive liquid-liquid extraction and solid-phase microextraction are the most common techniques that typically combined with derivatization, while the development of novel and greener protocols is receiving substantial consideration in the field of analytical chemistry.

Deep eutectic solvents with low viscosity for automation of liquid-phase microextraction based on lab-in-syringe system: Separation of Sudan dyes

In the work limitations of deep eutectic solvents in the flow-based analysis are discussed. Deep eutectic solvents based on terpenes and fatty acids with low viscosity were studied as extraction solvents for liquid-liquid microextraction into a lab-in-syringe system for the first time. As a result an automated deep eutectic solvent-based microextraction approach was proposed. The procedure involved aspiration of deep eutectic solvent (based on terpene and fatty acid) and aqueous sample solution followed by phases mixing by a magnetic stirrer inside a syringe of flow system. After phase separation the extract phase was transferred from the syringe into a vial followed by analysis by a high-performance liquid chromatography with diode-array detection. The determination of Sudan I, Sudan II and Sudan III in chili-based sauces was considered as an analytical task. The mass-transfer intensification performed by the magnetic stirring inside the syringe allowed to perform fast (2 min) and efficient (extraction recoveries 87-95%) extraction. The limits of detection, calculated from a blank test based on 3σ, were from 0.003 to 0.005 mg kg^-1, RSD was <9%. The microextraction procedure did not involve the use of hazardous organic solvents, only 100 μL of natural deep eutectic solvent was required for dyes preconcentration.