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We proposed a specially designed sequential injection (SI) amperometric system coupling with a bioreactor for in-line glucose monitoring in cell culture. The system is composed of three main parts which are the bioreactor, SI system, and electrochemical detection unit. The bioreactor accommodates six individual cell culture units which can be operated separately under different conditions. The SI system enables automatic in-line sampling and in-line sample dilution, with a specially designed mixing unit; therefore, it has the benefits of fast analysis time and less contamination risk. The use of 3D-printed microfluidic components, a mixing channel, and a flow cell helped to reduce operational time and sample volume. A disposable screen-printed electrode (SPE), modified with glucose oxidase (GOD), carbon nanotube, and gold nanoparticle, was used for detection. The developed system provided a linear range up to 3.8 mM glucose in cell culture media. In order to work with cell culture in higher glucose media, the in-line sample dilution can be applied. The developed SI system was demonstrated with mouse fibroblast (L929) cell culture. The results show that glucose concentration obtained from the SI system is comparable with that obtained from the conventional colorimetric method. This work can be further developed and applied for in vitro cell-based experiments in biomedical research. [ABSTRACT FROM AUTHOR]

A precise, accurate, and reliable flow-batch spectrophotometric method for the determination of selenium (IV) was developed usingo-phenylenediamine as a reagent with a sequential injection monosegmented flow system incorporating a simple heating unit. The reaction zones of selenium(IV) ando-phenylenediamine were mixed and heated in a chamber at 62°C for 5 minutes. The piaselanol complexes were then detected at a maximum absorption wavelength of 335 nm. In-line single standard calibration and standard addition procedures were developed employing the monosegmented flow technique. Under the optimized conditions, a linear calibration graph in a range of 0.1–4.0 mg L−1selenium (IV) was obtained with limits of detection and quantitation of 0.01 and 0.1 mg L−1, respectively. Relative standard deviations were 2% [for both 0.1 and 0.5 mg L−1selenium (IV) (n = 11)]. A sample throughput of 2 h−1using four standard addition levels was achieved. The developed system was successfully applied to raw selenium-enriched yeast samples. The analyses performed by the developed method agreed well with those obtained from a standard inductively coupled plasma mass spectrometry method. [ABSTRACT FROM AUTHOR]

Abstract: A cost-effective sequential injection system incorporating with an in-line UV digestion for breakdown of organic matter prior to voltammetric determination of Zn(II), Cd(II), Pb(II) and Cu(II) by anodic stripping voltammetry (ASV) on a hanging mercury drop electrode (HMDE) of a small scale voltammetric cell was developed. A low-cost small scale voltammetric cell was fabricated from disposable pipet tip and microcentrifuge tube with volume of about 3mL for conveniently incorporated with the SI system. A home-made UV digestion unit was fabricated employing a small size and low wattage UV lamps and flow reactor made from PTFE tubing coiled around the UV lamp. An in-line single standard calibration or a standard addition procedure was developed employing a monosegmented flow technique. Performance of the proposed system was tested for in-line digestion of model water samples containing metal ions and some organic ligands such as strong organic ligand (EDTA) or intermediate organic ligand (humic acid). The wet acid digestion method (USEPA 3010a) was used as a standard digestion method for comparison. Under the optimum conditions, with deposition time of 180s, linear calibration graphs in range of 10–300μgL−1 Zn(II), 5–200μgL−1 Cd(II), 10–200μgL−1 Pb(II), 20–400μgL−1 Cu(II) were obtained with detection limit of 3.6, 0.1, 0.7 and 4.3μgL−1, respectively. Relative standard deviation were 4.2, 2.6, 3.1 and 4.7% for seven replicate analyses of 27μgL−1 Zn(II), 13μgL−1 Cd(II), 13μgL−1 Pb(II) and 27μgL−1 Cu(II), respectively. The system was validated by certified reference material of trace metals in natural water (SRM 1640 NIST). The developed system was successfully applied for speciation of Cd(II) Pb(II) and Cu(II) in ground water samples collected from nearby zinc mining area. [Copyright &y& Elsevier]

Blood studies for clinical screening/analysis are geared toward point of care testing. Flow based techniques have expanded their applications with unique approaches that may be adaptable for use as alternative disease screening/diagnosis. Many newly developed systems for solution based chemical analysis can be easily adapted for use with plasma and serum. However, cell and intracellular analyses are different. Blood cell analyses require a particular way of sample introduction and detection. This review emphasizes the applications of flow based techniques, especially those that were coupled with FI/SI, in clinical studies through analysis of red blood cells and their intracellular substances. [ABSTRACT FROM AUTHOR]

Sequential injection was introduced to perform a multi-step immunoassay. Modified low cost hematocrit glass capillary was employed as the immobilization surface for a competitive immunoassay of chondroitin sulfate (CS), a potential biomarker for cancer. Glass capillary is low cost and adapts well to the flow system without causing back pressure. The analysis time per sample run with automation of the multi-step immunoassay is improved as compared to the conventional batch-wise micro-plate format. The performance of the sequential injection capillary immunoassay (SI-CI) system for CS was evaluated with spiked human serum samples. [ABSTRACT FROM AUTHOR]

This paper reviews some recent developments on cost-effective flow-based analysis. They include the newly developed Lab-at-Valve (LAV), concepts in using the stopped-flow injection approach, on-line sample pretreatment systems, including bead injection–flow injection and flow injection–ion-chromatography, systems for size-based speciation, and cost-effective reagents. Applications and advantages of such techniques are discussed. [Copyright &y& Elsevier]

Abstract Simple simultaneous determination of iron and manganese by sequential injection spectrophotometry using astilbin extracted from Smilax china L. root is proposed. It is based on the kinetic difference of the complexation of the ions and astilbin. With a simple sequential injection system, the simultaneous determination can be performed at pH 10 and can be followed at a wavelength of 440 nm. A throughput of 12 samples per hour was obtained with detection limits (3σ) of 0.05 mg L−1 iron(III) and 0.20 mg L−1 manganese(II), respectively. Application of the proposed system to real ground water sample was demonstrated. The results agreed with that of the atomic absorption spectrophotometric reference method. Graphical abstract fx1 Highlights • A simple SI spectrophotometric system was developed for the simultaneous determination of Fe and Mn in groundwater. • The system employs astilbin extracted from the plant as a single chromogenic reagent for determination of both Fe and Mn. • The system demonstrates green chemical analysis concept. [ABSTRACT FROM AUTHOR]

Abstract: A sequential injection-Lab-at-valve (SI-LAV) segmented flow system for kinetic study of an enzyme was developed. Air segments were introduced for separation of enzyme and substrate zones and separation of the stacked zones from the carrier solution which ensure the measurement of the initial rate and minimize the dilution/dispersion effect. The open- ended mixing chamber makes it possible to use air segments in the flow system without the need for additional air segment discarding steps. The enzyme horseradish peroxidase (HRP) kinetic parameters based on initial rate was used as a model study. The operation of the system is virtually the same as that of the conventional batch-wise process. The kinetic parameters (i.e. K m and V max) of HRP obtained using the proposed system agree well with those obtained using the batch-wise process as well. The proposed system offers additional benefits of volume down scaling, improved rapidity and automatic features that does not require a skillful operator. [Copyright &y& Elsevier]

Abstract: A cost-effective sequential injection monosegmented flow analysis (SI-MSFA) with anodic stripping voltammetric (ASV) detection has been developed for determination of Cd(II) and Pb(II). The bismuth film working electrode (BiFE) was employed for accumulative preconcentration of the metals by applying a fixed potential of −1.10V versus Ag/AgCl electrode for 90s. The SI-MSFA provides a convenient means for preparation of a homogeneous solution zone containing sample in an acetate buffer electrolyte solution and Bi(III) solution for in situ plating of BiFE, ready for ASV measurement at a flow through thin layer electrochemical cell. Under the optimum conditions, linear calibration graphs in range of 10–100μgL−1 of both Cd(II) and Pb(II) were obtained with detection limits of 1.4 and 6.9μgL−1 of Cd(II) and Pb(II), respectively. Relative standard deviations were 2.7 and 3.1%, for 11 replicate analyses of 25μgL−1 Cd(II) and 25μgL−1 Pb(II), respectively. A sample throughput of 12h−1 was achieved with low consumption of reagent and sample solutions. The system was successfully applied for analysis of water samples collected from a draining pond of zinc mining, validating by inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. [Copyright &y& Elsevier]

A sensitive, precise and reliable flow-batch method for the determination of aluminium (Al) was developed using a sequential injection-monosegmented flow system incorporating a mixing chamber unit. Eriochrome cyanine R (ECR) was used as a chromogenic reagent in the presence of N , N -dodecyltrimethylammonium bromide (DTAB). The Al-ECR complex at pH 6 gave a maximum absorption at 584 nm. In-line single standard calibration and a standard addition procedure were developed employing the monosegmented flow technique. Under the optimum conditions, a linear calibration graph in the range of 0.0075–0.625 mg L −1 Al was obtained with limits of detection and quantitation of 0.0020 and 0.0070 mg L −1 , respectively. Relative standard deviations were 0.8 and 1.3% for 0.010 and 0.025 mg L −1 Al ( n = 11), respectively. A sample throughput of 24 h −1 using an in-line standard calibration approach and 6 h −1 using four standard addition levels was achieved. The developed system was successfully applied to water samples and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 85 and 104% were obtained. [ABSTRACT FROM AUTHOR]

Abstract: An automatic immunoassay system for an assay of sialoglycoconjugates was developed based on the sequential injection technique. A cost effective plain glass capillary tube was used as a solid surface for immobilization of biomolecules via a simple physical adsorption which is adequate to tolerate the force of solution flowing through the capillary during the multi-steps immunoassay process. Immunoassay could be performed with many improvements—rapidity per sample as compared to the conventional micro-plate format (40min vs. 5–8h); lower cost and simpler as compared to fused silica capillary with covalent immobilization; and without problem of back pressure as compared to flow injection-bead based immunoassay. Performance of the sequential injection-capillary immunoassay was demonstrated by assay of sialoglycoconjugates level in human serum to differentiate cancer patients from healthy people. [Copyright &y& Elsevier]

Abstract: A new sequential injection (SI) system with spectrophotometric detections has been developed for successive determination of protein and glucose. The protein assay is based on ion-association of protein with tetrabromophenolphthalein ethyl ester (TBPE) in the presence of Triton X-100 at pH 3.2. The blue product is monitored for absorbance at 607nm. For glucose, hydrogen peroxide, generated by the oxidation of glucose in the presence of glucose oxidase immobilized on glass beads packed in a minicolumn, is monitored using iron-catalyzed oxidation reaction of p-anisidine to form a red colored product (520nm). The SI procedure takes advantage in performing the protein assay during the incubation period for glucose oxidation. Linear ranges were up to 10mgdL−1 human serum albumin (HSA) with a limit of detection (LOD) (3σ) of 0.3mgdL−1, and up to 12.5mgdL−1 glucose with LOD of 0.08mgdL−1. R.S.D.s (n =11) were 2.7% and 2.5% (for 1mgdL−1 and 5mgdL−1 HSA) and 1.4% (9mgdL−1 glucose). Sample throughput for the whole assay of both protein and glucose is 6h−1. The automated system has been demonstrated for the successive assay of protein and glucose in urine samples taken from diabetic disease patients, with good agreement with the other methods. This developed SI system is an alternative automation for screening for diabetic diagnosis. [Copyright &y& Elsevier]

Abstract: A sequential injection (SI) method in a lab-on-valve (LOV) format for simultaneous spectrophotometric determination of copper and iron has been devised. The detection chemistry is based on the complex formation of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]aniline (5-Br-PSAA) with copper(II) and/or iron(II) at pH 4.6. Copper(II) reacts with 5-Br-PSAA to form the complex which has an absorption maximum at 580nm but iron(III) does not react. In the presence of a reducing agent only iron(II)–5-Br-PSAA complex is formed and detected at 558nm. Under the optimum experimental conditions, the determinable ranges are 0.1–2mgl−1 for copper and 0.1–5mgl−1 for iron, respectively, with a sampling rate of 18h−1. The limits of detection are 50μgl−1 for copper and 25μgl−1 for iron. The relative standard deviations (n =15) are 2% for 0.5mgl−1 copper and 1.8% for 0.5mgl−1 iron when determined in standard solutions. The recoveries range between 96 and 105% when determining 0.25–2mgl−1 of copper and 0.2–5mgl−1 of iron in artificial mixtures at copper/iron ratios of 1:10 to 5:1. The proposed SI-LOV method is successfully applied to the simultaneous determination of copper and iron in multi-element standard solution and in industrial wastewater samples. [Copyright &y& Elsevier]

Abstract: An automated sequential injection (SI) method for the determination of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in freshwaters is presented. For DIC measurement on-line sample acidification (sulphuric acid, pH<2), converted DIC to CO2 which subsequently diffused through a PTFE membrane into a basic, cresol red acceptor stream. The CO2 increased the concentration of the acidic form of the cresol red indicator, with a resultant decrease in absorbance at 570nm being directly proportional to DIC concentration. DIC+DOC was determined after on-line sample irradiation (15W low power UV lamp) coupled with acid–peroxydisulfate digestion, with the subsequent detection of CO2 as described above. DOC was determined by subtraction of DIC from (DIC+DOC). Analytical figures of merit were linear ranges of 0.05–5.0mgCL−1 for both DIC and DIC+DOC, with typical R.S.D.s of less than 7% (0.05mgCL−1–5.3% for DIC and 6.6% for DIC+DOC; 4.0mgCL−1–2.6% for DIC and 2.4% for DIC+DOC, n =3) and an LOD (blank+3S.D.) of 0.05mgCL−1. Sample throughput for the automated system was 8h−1 for DIC and DOC with low reagent consumption (acid/peroxydisulfate 200μL per DIC+DOC analysis). A range of model carbon compounds and Tamar River (Plymouth, UK) samples were analysed for DIC and DOC and the results showed good agreement with a high temperature catalytic oxidation (HTCO) reference method (t-test, P =0.05). [Copyright &y& Elsevier]

Abstract: Sequential injection with “Lab-at-Valve (LAV)” approach is demonstrated for potentiometric determination of chloride. The LAV flow-through electrode system consists of two Ag/AgCl electrodes: one as a reference electrode, silver chloride activated surface-silver wire soaked in a constant-concentration chloride ion solution in a small tube covered with a polymer-membrane, another as a working electrode (a similar silver chloride activated surface-silver wire) placed in a flow channel. The electrode system is attached at one port of a 10 port multiposition valve. A modified autoburette was used as a propelling device. Using SI operation via a program written in-house, based on LabVIEW®, a standard/sample is inserted, via the selection valve, in potassium nitrate as an electrolyte and water is used as a carrier. The zones are transported from the holding coil to the flow cell to monitor the difference in potential due to concentration cell behavior. The potential difference is then recorded as a peak. Peak height is proportional to logarithm of chloride concentration. The SI-LAV for chloride determination is very simple, fast, precise, accurate, automatic and economical. Applications to mineral drinking water and surface water have been made. The results agree with those of IC and titrimetric methods. [Copyright &y& Elsevier]

Sequential injection (SI) with bead injection (BI) and lab-on-valve (L-O-V) was exploited for determination of trace lead using electrothermal atomic absorption spectrometry (ETAAS). A renewable microcolumn incorporated within the L-O-V system was investigated by using Sephadex G-25 impregnated by dithizone. Lead solution was passed through the impregnated beads. The beads were directly propelled into a graphite tube where they were pyrolyzed and lead ions were subsequently atomized. Conditions of the ETAAS measurement were studied including chemical modifiers (palladium, molybdenum and tartaric acid). The SI system for trapping of lead on the beads in the L-O-V could be operated in parallel to the ETAAS operation. [Copyright &y& Elsevier]

Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric detection have been exploited for simultaneous determination of some metals. A pre-plated mercury film on a glassy carbon disc electrode was used as a working electrode in both systems. The same film can be repeatedly applied for at least 50 analysis cycles, thus reducing the mercury consumption and waste. A single line FI voltammetric system using an acetate buffer as a carrier and an electrolyte solution was employed. An injected standard/sample zone was mixed with the buffer in a mixing coil before entering a flow cell. Metal ions were deposited on the working electrode by applying a potential of −1.1 V vs Ag/AgCl reference electrode. The stripping was performed by anodically scanning potential of working electrode to +0.25 V, resulting a voltammogram. Effects of acetate buffer concentration, flow rate and sample volume were investigated. Under the selected condition, detection limits of 1 μg l−1 for Cd(II), 18 μg l−1 for Cu(II), 2 μg l−1 for Pb(II) and 17 μg l−1 for Zn(II) with precisions of 2–5% (n=11) were obtained. The SI voltammetric system was similar to the FI system and using an acetate buffer as a carrier solution. The SI system was operated by a PC via in-house written software and employing an autotitrator as a syringe pump. Standard/sample was aspirated and the zone was then sent to a flow cell for measurement. Detection limits for Cd(II), Cu(II), Pb(II) and Zn(II) were 6, 3, 10 and 470 μg l−1, respectively. Applications to water samples were demonstrated. A homemade UV-digester was used for removing organic matters in the wastewater samples prior to analysis by the proposed voltammetric systems. [Copyright &y& Elsevier]

Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l−1 was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l−1 ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid–base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2–8% w v−1 of acetic acid with a relative standard deviation of 4.8% (5.0% w v−1 acetic acid, n=11) was obtained. Sample throughputs of 60 h−1 were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively. [Copyright &y& Elsevier]