Multisyringe Flow Injection Analysis System Research Articles

Multisyringe Flow Injection Analysis of Tropomyosin Allergens in Shellfish Samples.

This paper presents the development and the application of a multisyringe flow injection analysis system for the fluorimetric determination of the major heat-stable known allergen in shrimp, rPen a 1 (tropomyosin). This muscle protein, made up of 284 amino acids, is the main allergen in crustaceans and can be hydrolyzed by microwave in hydrochloric acid medium to produce glutamic acid, the major amino acid in the protein. Glutamic acid can then be quantified specifically by thermal conversion into pyroglutamic acid followed by chemical derivatization of the pyroglutamic acid formed by an analytical protocol based on an OPA-NAC reagent. Pyroglutamic acid can thus be quantified between 1 and 100 µM in less than 15 min with a detection limit of 1.3 µM. The method has been validated by measurements on real samples demonstrating that the response increases with the increase in the tropomyosin content or with the increase in the mass of the shrimp sample.

Determination of total and bioavailable As and Sb in children's paints using the MSFIA system coupled to HG-AFS.

In this study, the use of hydride generation atomic fluorescence spectrometry (HG-AFS) coupled with the multi-syringe flow injection analysis (MSFIA) has been proposed in the application of the Doehlert design to optimise the determination of As and Sb in gouache and tempera children's paints. The determination of the total and bioavailable As and Sb in paint samples from various brands and colours was also investigated. The limits of quantification (LOQ) obtained for the determination of As and Sb were 14.0 and 8.6 ng g-1, respectively. The accuracy and precision of the method were evaluated through recovery tests (by the analyte addition method) at three levels for both elements, and by the analysis of certified reference materials of clay (CRM 052, Loamy Clay 1) and river water (SLRS-4). Twenty paint samples, manufactured in China, Italy, Spain and Brazil, were analysed. The concentrations of As varied between below LOQ (<14 ng g-1) and 136.0 ± 1.1 ng g-1 (average value of 101.0 ng g-1, n = 10), and Sb between below LOQ (<8.6 ng g-1) and 74.0 ± 5.4 ng g-1 (average value of 21.7 ng g-1, n = 17). The children's paint samples presented As and Sb concentrations that were below the maximum values established by the National Institute of Metrology, Quality and Technology (INMETRO), as well as by the European legislation Directive 2009/48/EC. Based on the obtained results for the total As and Sb concentrations, eight samples were selected to evaluate the migration or bioavailability of As and Sb after solubilisation in HCl solution. The obtained results showed that for the eight analysed samples, the concentration of both elements after solubilisation in HCl solution were below the LOQ (<16.2 ng g-1 for As and <7.1 ng g-1 for Sb). These values correspond to the limits of analytical concentrations of As and Sb established by INMETRO and the Brazilian Association of Technical Standards (ABNT). The determined concentrations of As and Sb guarantee the safety (with regards to these elements) for children when using the analysed paint samples since they do not cause any health risk. The analytical method for the determination of the total and bioavailable As and Sb in children's paints was efficient, accurate and precise.

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.

Development of a MSFIA system for sequential determination of antimony, arsenic and selenium using hydride generation atomic fluorescence spectrometry

This paper proposed a multisyringe flow injection analysis (MSFIA) system for antimony, arsenic and selenium determination in peanut samples by hydride generation atomic fluorescence spectrometry (HG-AFS). The optimization step of the hydride generation was performed using a two-level full factorial design involving the parameters: hydrochloric acid, sodium tetrahydroborate and potassium iodide concentrations. So, using the chemical conditions optimized, this method allows the determination of these elements employing the external calibration technique using aqueous standards with limits of detection and quantification of 0.04 and 0.14µgL−1 for antimony, 0.04 and 0.14µgL−1 for arsenic and 0.14 and 0.37µgL−1 for selenium, respectively. Additionally, the effect of vanadium, chromium, cobalt, nickel, zinc, copper, iron and molybdenum on the generation of chemical vapour was also studied. The precision expressed as relative standard deviation varied from 1.2 to 3.6% for antimony, 1.8–3.9% for arsenic and 1.8–2% for selenium. The accuracy for arsenic and selenium was confirmed using the certified peach leaves reference material SRM 1547 produced by National Institute of Standard and Technology. The proposed method showed 45 injection throughput (h−1) using 1.6mL sample volume for each element, 0.8mL NaBH4 0.5% (w/v) containing NaOH 0.05% (w/v), 0.8mL HCl 5M and 0.4mL KI 14% (w/v) containing L-ascorbic acid 2.5% (w/v). The method was applied to the determination of antimony, arsenic and selenium in peanut samples, which were firstly lyophilized and afterward digested using microwave assisted radiation. Six samples were analyzed and the contents of the elements found were: 28.7–41.3µgkg−1 for arsenic, 86.4–480.1µgkg−1 for selenium and 32.6–52.4µgkg−1 for antimony. Addition/recovery tests were also performed to confirm the method accuracy for the three elements.

Sensitive kinetic-catalytic spectrophotometric method for cobalt determination using a chip coupled to a multisyringe flow injection analysis system

The development of an automated kinetic-catalytic spectrophotometric method for cobalt determination is presented. The method is based on the catalytic effect of Co in the oxidation of hydroxybenzoic acid by H2O2 in basic media. The method has been automated using a multisyringe flow injection system coupled to a monolithic flow conduit called chip (chip-MSFIA). All reagents and sample are simultaneously propelled into the chip to achieve an efficient mixing. The reaction product is monitored at 482nm. The reaction takes place very fast at room temperature, thus the fixed-time method is applied to quantify Co concentration in samples. Variables such as, reagents concentration, pH, flow rate and reaction time have been optimized to improve the selectivity and sensitivity of the proposed system. Under optimal conditions, Co may be determined in the range 0.02–10.00μgL−1 achieving a limit of detection of 0.02μgL−1 and an injection throughput of 68h−1. Relative standard deviations are below 3%. The method has been successfully applied to water samples and a pharmaceutical formulation. The accuracy of the method has been validated by add-recovery tests and satisfactory recoveries from 91% to 97% were obtained.

Titanium determination by multisyringe flow injection analysis system and a liquid waveguide capillary cell in solid and liquid environmental samples

A multisyringe flow injection analysis system using a liquid waveguide capillary cell (MSFIA-LWCC) has been used for the spectrophotometric determination of titanium (Ti) in marine environmental samples. Samples were previous digested using potassium peroxodisulfate (K2S2O8). The method showed to be linear over a range up to 1μM with a detection limit of 9.2nM. The analysis consumes little reagent (250μL) and sample (600μL). It had an adequate accuracy with high repeatability (RSD of 1.8%) for all marine samples. The proposed method was used to evaluate the concentration of Ti in natural samples collected in the coastal area of the Majorca Island (Western Mediterranean Sea). We report average concentrations of Ti in coastal surface microlayer of 510.7±267.2nM, in surface sediments of 2.72±1.84μmol/g, and in rhizomes and leaves of Posidonia oceanica of 310±295nmol/g and 157±132nmol/g, respectively.

Cadmium determination in natural water samples with an automatic multisyringe flow injection system coupled to a flow-through screen printed electrode

Heavy metals, as cadmium, attract a rising attention in environmental studies due to their increasing release by human activities and acute toxicity. In situ analytical methods are needed to minimize current uncertainties caused by the transport and conservation of samples. Here, we present the completely automatic determination of Cd in natural waters using a newly developed screen printed electrode sensor (SPE), inserted in a homemade purpose-built flow cell coupled to a Multi-Syringe Flow Injection Analysis system (MSFIA). The working electrode of SPEs was constituted by a carbon film modified with Nafion. Cd was plated on an in situ bismuth film and determined using Square Wave Anodic Stripping Voltammetry. Different chemical conditions of deposition and stripping were studied. A sample/acetic buffer mixture was found to be a well suited medium to form the Bi film and perform the analysis. Cd was quantified via calibration by on line standard additions. The limit of detection was found to be 0.79μgL−1, well below the limit stipulated by the European directive (5μgL−1). Good sample throughput (14h−1) and low consumption of reagent and sample (1.3mL) were also obtained in line with previous works in Cd flow analysis.

Spectrophotometric determination of zinc and copper in a multi-syringe flow injection analysis system using a liquid waveguide capillary cell: Application to natural waters

This work exploits a multi-syringe injection analysis (MSFIA) system coupled with a long liquid waveguide capillary cell for the spectrophotometric determination of zinc and copper in waters. A liquid waveguide capillary cell (1.0m pathlength, 550μm i.d. and 250μL internal volume) was used to enhance the sensitivity of the detection. The determination for both ions is based on a colorimetric reaction with zincon at different pH values. The developed methodology compares favourably with other previously described procedures, as it allows to reach low detection limits for both cations (LODs of 0.1 and 2μgL−1, for copper and zinc, respectively), without the need for any pre-concentration step. The system also provided a linear response up to 100μgL−1 with a high throughput (43h−1) and low reagent consumption and effluent production. The developed work was applied to natural waters and three certified reference water samples.

Multisyringe flow injection analysis system for automation of standard addition calibration method

In the present work, the multi-channel features of multisyringe flow injection analysis (MSFIA) were exploited for the first time to implement calibration based on standard addition method (SAM). For this, standard solutions containing different concentrations of target analyte were placed in each syringe of the multisyringe and connected to a flow network where in-line mixing of sample and standard through a merging zone approach was established prior to detection of analyte. Using this strategy, artifacts reported before in SAM using flow injection analysis were avoided as the concentration of the analyte in the resulting mixture was related to the dilution of sample and added standard within the system, and the concentration of all matrix components was kept constant during all measurements. The feasibility of the proposed MSFIA system was assessed through application to potentiometric determination of chloride ion in electroplating bath and milk samples. Results obtained for samples ( n = 15) were not statistically different from those provided by titrimetric procedures, with an excellent throughput (20–31 samples h − 1 ), comprising four-level addition of chloride ion.

MSFIA system for mercury determination by cold vapour technique with atomic fluorescence detection

A new multisyringe flow injection analysis system for mercury determination using cold vapour technique assembling with atomic fluorescence spectrometry is proposed. The system consists of a multisyringe module as liquid driver, a gas–liquid separator, a gas dryer device and an atomic fluorescence detector. As reducing agent, 1% tin chloride solution is used. Standard solutions and carrier are prepared in 1% hydrochloric acid. An argon stream is employed as carrier gas for cold vapour technique. The development of the smart analytical system is feasible due to the four internal gains of the atomic detector and the versatility of software used. According to the signal obtained, the software is able to choose the most suitable internal gain for sample analysis. Four linear calibration curves (i.e. one for each internal gain) were obtained. The smart system developed allows to determine a wide concentration range from 120 to 0.006 μg L −1 Hg. The detection limit (3 σ/ S) achieved is 0.002 μg L −1. The relative standard deviation is inferior to 2% for each calibration curve. This system was validated by means of a solid reference material and it was applied to environmental samples successfully.

An environmental friendly method for the automatic determination of hypochlorite in commercial products using multisyringe flow injection analysis

A multisyringe flow injection analysis system was used for the determination of hypochlorite in cleaning agents, by measurement of the native absorbance of hypochlorite at 292 nm. The methodology was based on the selective decomposition of hypochlorite by a cobalt oxide catalyst giving chloride and oxygen. The difference of the absorbance of the sample before and after its pass through a cobalt oxide column was selected as analytical signal. As no further reagent was required this work can be considered as a contribution to environmental friendly analytical chemistry. The entire analytical procedure, including in-line sample dilution in three steps was automated by first, dilution in a stirred miniature vessel, second by dispersion and third by in-line addition of water using multisyringe flow injection technique. The dynamic concentration range was 0.04–0.78 g L −1 (relative standard deviation lower than 3%), where the extension of the hypochlorite decomposition was of 90 ± 4%. The proposed method was successfully applied to the analysis of commercial cleaning products. The accuracy of the method was established by iodometric titration.

Improving the chemiluminescence-based determination of sulphide in complex environmental samples by using a new, automated multi-syringe flow injection analysis system coupled to a gas diffusion unit

A new, completely automated multi-syringe flow injection analysis (MSFIA) system coupled to a gas diffusion unit (GDU) was used for the chemiluminescence (CL)-based determination of sulphide ion in various types of environmental matrices with a high sensitivity and selectivity, and the need for no manual sample pretreatment. Sulphide ions are transferred as H 2S from the donor channel of the GDU to its acceptor channel (AC) through a hydrophobic membrane inserted between the two streams. The solution held in AC replaces the initial sample matrix, which may contain a wide variety of interferents, with one suitable for the CL determination of the analyte. Once sulphide ions have been isolated from the sample matrix, they are determined by their catalytic action on the luminol/H 2O 2 chemiluminescent reaction system. The influence of various chemical and hydrodynamic variables is discussed and the performance of the proposed system compared with that of existing flow systems for the same purpose. Under the operating conditions used, the proposed method features a linear working range of 0.02–2 mg L −1, a limit of detection (3 σ blank) of 0.003 mg L −1, a throughput of 20 samples h −1 and a coefficient of variation of 2.4% ( n = 10) for a 1 mg L −1 sulphide concentration. The method was used to determine sulphide in leachates and various types of water samples.

Multisyringe Flow Injection Analysis: State-of-the-Art and Perspectives

In the present paper, the characteristics (apparatus, manifold design, and operation mode) of multi-syringe flow injection analysis systems are discussed and critically compared to those of flow injection analysis and sequential injection systems. Furthermore, a survey of applications proposed until the present moment is presented, with special emphasis on implementation of in-line sample treatment.

Sample introduction in multi-syringe flow injection systems: comparison between time-based and volume-based strategies

In multi-syringe flow injection analysis (MSFIA), devices as selection, injection or commutation valves must be incorporated to the manifold to provide access to sample and standard solutions. Therefore, the definition of sample amount can be either volume or time-based. In the present work, four configurations for sample introduction (two for each approach) were tested in order to establish if the different strategies affect the analytical signal in MSFIA systems. The mean absorbance value from ten consecutive injections of a bromothymol blue solution obtained for the time-based strategy was lower than that provided by the volume-based approach as the exact volume delivered by each configuration was different from the “theoretical” volume. For time-based configurations, the exact volume delivered is 2–5% lower than the theoretical value while for volume-based configurations, the volume delivered was between 6 and 46% larger than the theoretical volume. Moreover, for time-based sampling, the order of steps in the analytical cycle was of utmost importance since any alteration in the flow direction affected the volume delivered in the subsequent step in the analytical cycle. The influence of the two sampling approaches was also evaluated in the MSFIA systems for the spectrophotometric determination of phenolic compounds and the potentiometric determination of chloride. There was no evidence that the use of either volume or time-based sampling would improve the analytical features of these determinations when real samples were tested.

In-line membrane separation method for sulfide monitoring in wastewaters exploiting multisyringe flow injection analysis

A fully automated multisyringe flow injection analysis (MSFIA) system coupled to gas-diffusion (GD) separation is proposed for the spectrophotometric determination of sulfide in urban wastewaters containing suspended solids. No preliminary batch sample treatment is required. The method carried out in a multicommutated system is based on analyte release as hydrogen sulfide from the donor channel of the GD module into a stagnant recipient solution composed of N, N-dimethyl- p-phenylene diamine (DMPD) and Fe(III). The methylene blue dye generated in-line via oxidative coupling is subsequently delivered downstream to a miniaturized flow-through light-emitting diode (LED)-based optical fiber plug-in spectrophotometer. The effect of various experimental variables on gas transfer across the membrane and concentration enhancement in the receiver solution via iterative flow reversals are discussed. Under the optimized chemical and hydrodynamic variables, the GD–MSFIA method features coefficients of variation better than 0.8% ( n=10) at the 10 mg l −1 level, a linear working range of 0.5–20 mg l −1 sulfide, a 3 σ blank-detection limit of 0.03 mg l −1 and an injection throughput of 13 h −1 for a sample volume of 700 μl and a forward flow mode. The analytical performance of the proposed GD–MSFIA system is also critically compared with that of in-line dialysis separation schemes using passive semi-permeable hydrophilic membranes. Accuracy was assessed by using the batch APHA–AWWA–WPFC standard method as an external reference.

Flow-through solid-phase based optical sensor for the multisyringe flow injection trace determination of orthophosphate in waters with chemiluminescence detection

In this work, a novel flow-through solid-phase based chemiluminescence (CL) optical sensor is described for the trace determination of orthophosphate in waters exploiting the multisyringe flow injection analysis (MSFIA) concept with multicommutation. The proposed time-based injection flow system relies upon the in-line derivatisation of the analyte with ammonium molybdate in the presence of vanadate, and the transient immobilisation of the resulting heteropolyacid in a N-vinylpyrrolidone/divinylbenzene copolymer packed spiral shape flow-through cell located in front of the window of a photomultiplier tube. The simultaneous injection of well-defined slugs of luminol in alkaline medium and methanol solution towards the packed reactor is afterwards performed by proper switching of the solenoid valves. Then, the light emission from the luminol oxidation by the oxidant species retained onto the sorbent material is readily detected. At the same time, the generated molybdenum-blue compound is eluted by the minute amount of injected methanol, rendering the system prepared for a new measuring cycle. Therefore, the devised sensor enables the integration of the solid-phase CL reaction with elution and detection of the emitted light without the typical drawbacks of the molybdenum-blue based spectrophotometric procedures regarding the excess of molybdate anion, which causes high background signals due to its self-reduction. The noteworthy features of the developed CL–MSFIA system are the feasibility to accommodate reactions with different pH requirements and the ability to determine trace levels of orthophosphate in high silicate content samples (Si/P ratios up to 500). Under the optimised conditions, a dynamic linear range from 5 to 50 μg P l −1 for a 1.8 ml sample, repeatability better than 3.0% and a quantification limit of 4 μg P l −1 were attained. The flowing stream system handles 11 analysis h −1 and has been successfully applied to the determination of trace levels of orthophosphate in environmental samples such as mineral, ground, tap and pond waters as well as samples from a water-steam cycle of an incineration plant. The t-test comparison of the means for the developed optical sensor and the molybdenum-blue spectrophotometric APHA/AWWA/WPCF reference method revealed that there is no evidence of significant differences between the obtained results at the 95% confidence level.