Exploiting an automated microfluidic hydrodynamic sequential injection system for determination of phosphate.

A microfluidic hydrodynamic sequential injection (µHSI) spectrophotometric system was designed and fabricated. The system was built by laser engraving a manifold pattern on an acrylic block and sealing with another flat acrylic plate to form a microfluidic channel platform. The platform was incorporated with small solenoid valves to obtain a portable setup for programmable control of the liquid flow into the channel according to the HSI principle. The system was demonstrated for the determination of phosphate using a molybdenum blue method. An ascorbic acid, standard or sample, and acidic molybdate solutions were sequentially aspirated to fill the channel forming a stack zone before flowing to the detector. Under the optimum condition, a linear calibration graph in the range of 0.1-6mg P L-1 was obtained. The detection limit was 0.1mgL-1. The system is compact (5.0mm thick, 80mm wide × 140mm long), durable, portable, cost-effective, and consumes little amount of chemicals (83µL each of molybdate and ascorbic acid, 133µL of the sample solution and 1.7mL of water carrier/run). It was applied for the determination of phosphate content in extracted soil samples. The percent recoveries of the analysis were obtained in the range of 91.2-107.3. The results obtained agreed well with those of the batch spectrophotometric method.

Sequential Injection Chromatography with an Ultra-short Monolithic Column for the Low-Pressure Separation of α-Tocopherol and γ-Oryzanol in Vegetable Oils and Nutrition Supplements.

A low-pressure separation procedure of α-tocopherol and γ-oryzanol was developed based on a sequential injection chromatography (SIC) system coupled with an ultra-short (5 mm) C-18 monolithic column, as a lower cost and more compact alternative to the HPLC system. A green sample preparation, dilution with a small amount of hexane followed by liquid-liquid extraction with 80% ethanol, was proposed. Very good separation resolution (Rs = 3.26), a satisfactory separation time (10 min) and a total run time including column equilibration (16 min) were achieved. The linear working range was found to be 0.4 - 40 µg with R2 being more than 0.99. The detection limits of both analytes were 0.28 µg with the repeatability within 5% RSD (n = 7). Quantitative analyses of the two analytes in vegetable oil and nutrition supplement samples, using the proposed SIC method, agree well with the results from HPLC.

Green analytical methodology using Indian almond (Terminalia catappa L.) leaf extract for determination of aluminum ion in waste water from ceramic factories.

The use of natural reagents from plant extracts for chemical analysis is one of the approaches in the development of low cost and environmentally friendly green analytical chemistry methodology. Here, crude extract from Indian Almond (Terminalia Catappa L.) leaves was used for colorimetric determination of aluminum by monitoring the absorbance of the Al(3+)-extract complex at 435 nm. Dry leaves and freeze-dried fresh leaf extract can be kept for extended use. A simple flow injection analysis (FIA) system was also employed for rapid analysis (approximately 180 injections/h). The linear working range up to 100 mg L(-1) was established with a detection limit (blank + 3SD) of 0.8 mg L(-1), a limit of quantitation (blank + 10SD) of 2.4 mg L(-1), and a relative standard deviation of 3-5%. This simple green analytical chemistry methodology was applied for the determination of Al(3+) in waste water samples from ceramic factories. The results agreed well with the results obtained from the ICP-OES technique.

Exploiting green analytical procedures for acidity and iron assays employing flow analysis with simple natural reagent extracts.

Green analytical methods employing flow analysis with simple natural reagent extracts have been exploited. Various formats of flow based analysis systems including a single line FIA, a simple lab on chip with webcam camera detector, and a newly developed simple lab on chip system with reflective absorption detection and the simple extracts from some available local plants including butterfly pea flower, orchid flower, and beet root were investigated and shown to be useful as alternative self indicator reagents for acidity assay. Various tea drinks were explored to be used for chromogenic reagents in iron determination. The benefit of a flow based system, which allows standards and samples to go through the analysis process in exactly the same conditions, makes it possible to employ simple natural extracts with minimal or no pretreatment or purification. The combinations of non-synthetic natural reagents with minimal processed extracts and the low volume requirement flow based systems create some unique green chemical analyses.

Flow injection determination of iron ions with green tea extracts as a natural chromogenic reagent.

A green chemistry system that utilizes natural extract as an alternative reagent for determination of metal ions has been investigated. The extract of green tea, a common beverage, is used for quantification of iron. The green tea extract was prepared in acetate buffer pH 4.8 and could be used without further purification with a simple flow injection (FI) system. The intensity of iron-green tea extract complexes was monitored using a green LED photometer. The use of natural reagent combined with the simple FI-LED photometer set up offers an alternative low cost and rapid system for the determination of metal ions. Detection limit of 0.05 ppm of Fe(III) ion and sampling rate of 180 injections h(-1) were achieved. Application of this system to the analysis of iron in pharmaceutical samples was demonstrated, and the results agreed well with those from the AOAC method.

Sequential injection-cation exchange micro-column system for hemoglobin typing to differentiate HbE carriers.

A weak cation exchange micro-column was incorporated into a sequential injection (SI) system to perform automatic hemoglobin (Hb) typing as an alternative way to measure HbE. Separation of HbF, HbA and HbA(2)/HbE was performed using phosphate buffer solutions in the pH range of 6-7 to create pH gradient mobile phase. The resultant chromatogram showed relative amounts of HbE to other types of hemoglobins in more quantitative detail than the conventional techniques such as dichlorophenol indophenol precipitation and micro-column anion exchange. The system is more economical than a commercially available ion-exchange HPLC analyzer for hemoglobin testing, though analysis time per run is longer due to the aspiration operation of the syringe pump of the SI system. It has been demonstrated that the system can differentiate negative (normal) from positive (HbE carriers) subjects.

Webcam camera as a detector for a simple lab-on-chip time based approach.

A modification of a webcam camera for use as a small and low cost detector was demonstrated with a simple lab-on-chip reactor. Real time continuous monitoring of the reaction zone could be done. Acid-base neutralization with phenolphthalein indicator was used as a model reaction. The fading of pink color of the indicator when the acidic solution diffused into the basic solution zone was recorded as the change of red, blue and green colors (%RBG.) The change was related to acid concentration. A low cost portable semi-automation analysis system was achieved.

A stopped flow system with hydrodynamic injection for red blood cells osmotic fragility test: possibility for automatic screening of beta-thalassemia trait.

Simple instrumentation and procedure with stopped flow system coupled to hydrodynamic injection and spectrophotometric detection were developed for automatic osmotic fragility test (OFT). OFT is a test for abnormal red blood cells based on the kinetics of their rupturing in a hypotonic saline solution. A portion of red cells was merged on-line with a hypotonic saline solution. They were mixed while flowing into the detector and were stopped for a short period for continuously monitoring the change of turbidity based on a transmission signal. In this work, a possible application of the system for screening of beta-thalassemia trait is demonstrated. Descriptions of instrumentation development and parameter optimization are presented. The system offers advantages over the conventional batch-wise OFT in terms of automation, precision, analysis time and sample volume.

Online assay of bone specific alkaline phosphatase with a flow injection-bead injection system.

Alkaline phosphatase (ALP) has been used as one of the biomarkers for bone resorption and liver diseases. Normally, total alkaline phosphatase is quantified along with other symptoms to determine the releasing source of the alkaline phosphatase. A semi-automated flow injection-bead injection system was proposed to conveniently and selectively assay bone alkaline phosphatase (BALP) based on its specific binding to wheat germ coated beads. Amount of BALP in serum was determined from the intensity of the yellow product produced from bound BALP on the retained beads and its substrate pNPP. The used beads were discarded and the fresh ones were introduced for the next analysis. The reaction cell was designed to be opened and closed using a computer controlled solenoid valve for a precise incubation time. The performance of the proposed system was evaluated by using it to assay BALP in human serum. The results were compared to those obtained by using a commercial ELISA kit. The system is proposed to be an easy and cost effective system for quantification of BALP as an alternative to batch wise wheat germ specific binding technique.

Simple spectrophotometric flow injection system with an in-valve minicolumn for enhancement during the determination of chromium(III) using EDTA.

A simple spectrophotometric flow injection (FI) procedure for the determination of Cr(III) using ethylenediaminetetraacetic acid (EDTA) was developed. An FI system with a column packed with Amberlite IR-120(H) was employed for sample pretreatment. This leads to the possibility of a single standard calibration. A linear calibration in a range of 10-27 microg Cr(III) was obtained with a detection limit of 1 microg Cr(III) and RSD of 2% (18 microg Cr(III), n=12). The proposed procedure was applied for determination of Cr(III) in leachate and dietary supplement samples. The results agreed with those obtained by the standard methods.

Simple bead injection-flow injection system for the determination of copper.

We demonstrate the extended application of a simple bead injection-flow injection system with a modified simple colorimetric detection unit for the determination of low amount of Cu2+ in samples of different matrices (water and supplement tablet samples) with minimal sample pretreatment by employing ammonium pyrrolidinedithiocarbamate (APDC) reagent.

Exploiting sequential injection analysis with lab-at-valve (LAV) approach for on-line liquid-liquid micro-extraction spectrophotometry.

Sequential injection analysis (SIA) with lab-at-valve (LAV) approach for on-line liquid-liquid micro-extraction has been exploited. Sample, reagent and organic solvent were sequentially aspirated into a coil attached to a central port of a conventional multiposition selection valve, where the extraction process was performed. The aqueous and organic phases were separated in a conical separating chamber LAV unit attached at one port of the valve. The organic phase containing extracted product was then monitored spectrophotometrically. The system offers a novel alternative on-line automated extraction in a micro-scale and has been successfully demonstrated for the assays of diphenhydramine hydrochloride (DPHH) in pharmaceutical preparations and anionic surfactant in water samples.

Flow-injection and sequential-injection determinations of paracetamol in pharmaceutical preparations using nitrosation reaction.

A simple FI and two different SI systems have been investigated for the determination of paracetamol by employing a simple reagent for a nitrosation reaction. It is based on the on-line nitrosation of paracetamol with sodium nitrite in an acidic medium. The formed nitroso derivative species reacts further with sodium hydroxide to convert it to a more stable compound. The yellow product is continuously monitored at 430 nm. The FI system is very simple and cost effective for fast manual operation (60 injections/h; y = 0.268x + 44.314, r2 = 0.9910 for 400 - 1000 mg/l and y = 0.1687x + 145.72, r2 = 0.9970 for 1000 - 2500 mg/l). The two SI systems with different components and configurations are automated and optimized for the conditions for which no extra dilution is to be required for sample handling: one with a syringe pump and two selection valves (60 samples/h; y = 0.1488x - 4.7297, r2 = 0.9946 for 400 - 1000 mg/l and y = 0.0858x + 63.933, r2 = 0.9849 for 1000 - 2500 mg/l); the other is simpler and more cost-effective, with an autoburette and only one selection valve (15 samples/h; y = 0.0072x + 1.1467, r2 = 0.9977 for 200 - 1000 mg/l and y = 0.0028x + 5.4699, r2 = 0.9879 for 1000 - 2500 mg/l). They have all been applied to assay paracetamol in pharmaceutical preparations. The obtained results agree with those by the US Pharmacopeia method.

Flow injection in-valve-mini-column pretreatment combined with ion chromatography for cadmium, lead and zinc determination.

A flow injection (FI) in-valve-mini-column packed with Chelex-100 resin is proposed for on-line sample pretreatment for some metal ions, namely, Cd(II), Pb(II) and Zn(II), prior to simultaneous determination using ion chromatography (IC). A solution containing a mixture of the cations was first passed through the in-valve-mini-column, followed by on-line elution. The eluate was then flowed further to an injection valve and was injected into an ion chromatograph. Conditions of the system were optimized. A single standard calibration was possible. The recoveries of cations were found to be in the range of 95-105%. The developed method was applied to the accurate analysis of zinc ore samples.

Determination of diphenhydramine hydrochloride in some single tertiary alkylamine pharmaceutical preparations by flow injection spectrophotometry.

A simple and rapid spectrophotometric method with flow injection is proposed for determination of diphenhydramine hydrochloride in some single tertiary alkylamine pharmaceutical preparations (capsule and syrup). It is based on ion pair formation with bromocresol green in a pH 3 buffer which a yellow ion pair compound is extracted into chloroform layer. An aqueous layer containing excess bromocresol green is injected into a carrier stream of 0.01 M borax solution and absorbance of the stream is continuously monitored at 610 nm. Diminution of the bromocresol green is related to an amount of diphenhydramine hydrochloride that can be evaluated from a calibration graph established by a plot of diphenhydramine hydrochloride concentration (micro gm l(-1)) and peak height (mV). Optimization will be discussed. The calibration graph is linear over the concentration ranges of 5-21 and 75-188 micro gm l(-1). A throughput of 100 injections h(-1) can be obtained. Application to assay for capsule and syrup samples has been demonstrated. The method is validated by comparing the results with HPLC analyses.