Sensitive Sequential Injection Research Articles

Simultaneous determination of rutin and ascorbic acid in a sequential injection lab-at-valve system

A green, simple, accurate and highly sensitive sequential injection lab-at-valve procedure has been developed for the simultaneous determination of ascorbic acid (Asc) and rutin using 18-molybdo-2-phosphate Wells-Dawson heteropoly anion (18-MPA). The method is based on the dependence of the reaction rate between 18-MPA and reducing agents on the solution pH. Only Asc is capable of interacting with 18-MPA at pH 4.7, while at pH 7.4 the reaction with both Asc and rutin proceeds simultaneously. In order to improve the precision and sensitivity of the analysis, to minimize reagent consumption and to remove the Schlieren effect, the manifold for the sequential injection analysis was supplemented with external reaction chamber, and the reaction mixture was segmented. By the reduction of 18-MPA with reducing agents one- and two-electron heteropoly blues are formed. The fraction of one-electron heteropoly blue increases at low concentrations of the reducer. Measurement of the absorbance at a wavelength corresponding to the isobestic point allows strictly linear calibration graphs to be obtained. The calibration curves were linear in the concentration ranges of 0.3–24mgL−1 and 0.2–14mgL−1 with detection limits of 0.13mgL−1 and 0.09mgL−1 for rutin and Asc, respectively. The determination of rutin was possible in the presence of up to a 20-fold molar excess of Asc. The method was applied to the determination of Asc and rutin in ascorutin tablets with acceptable accuracy and precision (1–2%).

Changes in the concentration of avenanthramides in response to salinity stress in CBF3 transgenic oat

Oat avenanthramides have long been known to possess potential nutraceutical and therapeutical properties. The change in avenanthramides 2p, 2c and 2f concentration in four salinity tolerant transgenic oat plants containing CBF3 gene and non-transgenic control exposed to different levels of salinity stress was investigated. Determination of oat avenanthramides at the nano-scale level was performed using a well-optimized and highly sensitive sequential injection chemiluminescence (SIA-CL) method enhanced by eco-friendly gold nanoparticles biosynthesized from oat biomass extract. Under the conditions of this study, the predominant avenanthramide, which also exhibited the strongest scavenging capacity, was 2c followed by 2p and 2f. At no stress, there was no significant (p ≤ 0.05) difference between the transgenic lines and control regarding the concentrations of the three determined avenanthramides. After exposure to 250 mmol L−1 NaCl, avenanthramide 2c dramatically increased by 170.9%, 580%, 353.6%, 457.6% and 229.1% in the control and the four transgenic lines, respectively. Among the transgenic lines, Agrogle-1 maintained the highest avenanthramides concentration under all salinity levels with maximum values of 71.5 mg kg−1 for 2p, 221.0 mg kg−1 for 2c and 62.0 mg kg−1 for 2f detected at 250 mmol L−1NaCl. The results of this study demonstrated that oat avenanthramides might have a potential role in enhancing abiotic stress tolerance in oats.

Eco-friendly synthesis of gelatin-capped bimetallic Au-Ag nanoparticles for chemiluminescence detection of anticancer raloxifene hydrochloride.

This study described the utility of green analytical chemistry in the synthesis of gelatin-capped silver, gold and bimetallic gold-silver nanoparticles (NPs). The preparation of nanoparticles was based on the reaction of silver nitrate or chlorauric acid with a 1.0wt% aqueous gelatin solution at 50°C. The gelatin-capped silver, gold and bimetallic NPs were characterized using transmission electron microscopy, UV-vis, X-ray diffraction and Fourier transform infrared spectroscopy, and were used to enhance a sensitive sequential injection chemiluminescence luminol-potassium ferricyanide system for determination of the anticancer drug raloxifene hydrochloride. The developed method is eco-friendly and sensitive for chemiluminescence detection of the selected drug in its bulk powder, pharmaceutical injections and biosamples. After optimizing the conditions, a linear relationship in the range of 1.0×10(-9) to 1.0×10(-1) mol/L was obtained with a limit of detection of 5.0×10(-10) mol/L and a limit of quantification of 1.0×10(-9) mol/L. Statistical treatment and method validation were performed based on ICH guidelines. Copyright © 2016 John Wiley & Sons, Ltd.

Application of silver nanoparticles to the chemiluminescence determination of cefditoren pivoxil using the luminol-ferricyanide system.

A new simple, accurate and sensitive sequential injection analysis chemiluminescence (CL) detection method for the determination of cefditoren pivoxil (CTP) has been developed. The developed method was based on the enhancement effect of silver nanoparticles on the CL signal arising from a luminol-potassium ferricyanide reaction in the presence of CTP. The optimum conditions relevant to the effect of luminol, potassium ferricyanide and silver nanoparticle concentrations were investigated. The proposed method showed linear relationships between relative CL intensity and the investigated drug concentration at the range 0.001-5000 ng/mL, (r = 0.9998, n = 12) with a detection limit of 0.5 pg/mL and quantification limit of 0.001 ng/mL. The relative standard deviation was 1.6%. The proposed method was employed for the determination of CTP in bulk drug, in its pharmaceutical dosage forms and biological fluids such as human serum and urine. The interference of some common additive compounds such as glucose, lactose, starch, talc and magnesium stearate was investigated. In addition, the interference of some related cephalosporins was tested. No interference was recorded. The obtained sequential injection analysis-CL results were statistically compared with those from a reported method and did not show any significant differences.

Highly sensitive sequential injection determination of p-aminophenol in paracetamol formulations with 18-molybdodiphosphate heteropoly anion based on elimination of Schlieren effect

A highly sensitive, precise and automated method using sequential injection analysis to assay quantitatively low levels of the p-aminophenol (PAP) in paracetamol formulations has been developed. A solution containing PAP and paracetamol is injected into an acetate buffer carrier stream and merged on-line with 18-molybdodiphosphate heteropoly complex reagent to form a specific blue derivative that is subsequently detected spectrophotometrically at 820nm. The procedure has been optimized mainly with respect to measurement sensitivity. It is based on the leveling off of the refraction indices of the liquids mixed in the flow system by the careful matching of the refractive index of the reagent solution with that of the carrier and sample solutions. Amount as low as 0.5μmolL−1 of PAP, which corresponds to the 0.001% of PAP in paracetamol tablets, can be reliably determined using the proposed method, which is clearly below the specification limits recommended for PAP determination in paracetamol drug and tablet formulations (50ppm or 0.005% (w/w)). The developed method was successfully applied to the analysis of paracetamol formulations spiked with PAP and determination of PAP content in Rapidol tablets past their expiration date both by proposed SIA and reference HPLC methods.

Simple sequential injection analysis system for rapid determination of microalbuminuria

A simple, specific and sensitive sequential injection analysis (SIA) system based on non-immunoassay fluorescent detection has been developed for the determination of urinary albumin. The specific binding of the dye Albumin Blue 580 (AB 580) to albumin in urine generated high emission fluorescent signals. The excitation and emission wavelengths were set at 590 and 610 nm, respectively. The analytical range was obtained from 1 to 100 mg L −1, with a detection limit of 0.3 mg L −1 (S/N = 3). The SIA system gave high precision with relative standard deviations (R.S.D.s) of 0.9% and 1.4% when evaluated with 15 and 100 mg L −1 albumin ( n = 15), respectively. The method exhibited good reproducibility, as assessed by performing four analytical curves on different days, and intra-run CVs (2.3–3.3%) and inter-run CVs (3.8%) were obtained. Rapid operation was achieved with a sample throughput of 37 h −1. This method was successfully applied to the determination of urinary albumin, and the method was highly correlated with the immunoturbidimetric method ( r 2 = 0.965; n = 72).

A Spectrofluorimetric Sequential Injection Method for the Determination of Penicillamine Using Fluorescamine in the Presence of β-cyclodextrins

A simple, robust and sensitive sequential injection spectrofluorimetric method for the determination of penicillamine (PA) in pharmaceutical formulations is developed. The method is based on the formation of a highly fluorescent derivative when penicillamine is reacted with fluorescamine (FL) in borate buffer of pH 9.3. The derivative produced is monitored at an emission wavelength of 495 nm using an excitation wavelength of 355 nm. The optimum conditions for the determination of PA with FL were: 3 mM FL, pH 9.3, 5 mM methyl-beta-cyclodextrin, sample volume of 75 microL and reagent volume of 75 microL. Furthermore, the effect of various media on the fluorescence intensity of the PA-FL derivative was studied and methyl-beta-cyclodextrin was found to give the largest enhancement. A linear dynamic range for the determination of PA of 5-80 ppm was obtained with a sampling frequency of 50 h(-1) and a relative standard deviation of less than 2.5%. The method was applied to the determination of PA in pharmaceutical formulations with reasonable recoveries ranging from 101.0-103.1%, indicating that no interference is observed from concomitants usually present in dosage forms.

Development of a non-invasive biomonitoring approach to determine exposure to the organophosphorus insecticide chlorpyrifos in rat saliva

Non-invasive biomonitoring approaches are being developed using reliable portable analytical systems to quantify dosimetry utilizing readily obtainable body fluids, such as saliva. In the current study, rats were given single oral gavage doses (1, 10, or 50 mg/kg) of the insecticide chlorpyrifos (CPF). Saliva and blood were then collected from groups of animals (4/time-point) at 3, 6, and 12 h post-dosing, and were analyzed for the CPF metabolite trichloropyridinol (TCP). Trichloropyridinol was detected in both blood and saliva at all doses and the TCP concentration in blood exceeded saliva, although the kinetics in blood and saliva were comparable. A physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) model for CPF incorporated a compartment model to describe the time-course of TCP in blood and saliva. The model adequately simulated the experimental results over the dose ranges evaluated. A rapid and sensitive sequential injection (SI) electrochemical immunoassay was developed to monitor TCP, and the reported detection limit for TCP was 6 ng/L (in water). Computer model simulation in the range of the Allowable Daily Intake (ADI) or Reference Dose (RfD) for CPF (0.01-0.003 mg/kg/day) suggests that the electrochemical immunoassay has adequate sensitivity to detect and quantify TCP in saliva at these low exposure levels. However, to validate this approach, further studies are needed to more fully understand the pharmacokinetics of CPF and TCP excretion in saliva. These initial findings suggest that the utilization of saliva as a biomonitoring matrix, coupled to real-time quantitation and PBPK/PD modeling represents a novel approach with broad application for evaluating both occupational and environmental exposures to CPF.

Sequential injection/electrochemical immunoassay for quantifying the pesticide metabolite 3,5,6-trichloro-2-pyridinol

An automated and sensitive sequential injection electrochemical immunoassay was developed to monitor a potential insecticide biomarker, 3,5,6-trichloro-2-pyridinol. The current method involved a sequential injection analysis (SIA) system equipped with a thin-layer electrochemical flow cell and permanent magnet, which was used to fix 3,5,6-trichloro-2-pyridinol (TCP) antibody coated magnetic beads (TCP-Ab-MBs) in the reaction zone. After competitive immunoreactions among TCP-Ab-MBs, TCP analyte, and horseradish peroxidase (HRP) labeled TCP, a 3,3′,5,5′-tetramethylbenzidine dihydrochloride and hydrogen peroxide (TMB-H 2O 2) substrate solution was injected to produce an electroactive enzymatic product. The activity of HRP tracers was monitored by a square wave voltammetric scanning electroactive enzymatic product in the thin-layer flow cell. The voltammetric characteristics of the substrate and the enzymatic product were investigated under batch conditions, and the parameters of the immunoassay were optimized in the SIA system. Under the optimal conditions, the system was used to measure as low as 6 ng L −1(ppt) TCP, which is around 50-fold lower than the value indicated by the manufacturer of the TCP RaPID Assay ® kit (0.25 μg/L, colorimetric detection). The performance of the developed immunoassay system was successfully evaluated on tap water and river water samples spiked with TCP. This technique could be readily used for detecting other environmental contaminants by developing specific antibodies against contaminants and is expected to open new opportunities for environmental and biological monitoring.

Sensitive sequential injection determination of naproxen based on interaction with β-cyclodextrin

A sensitive sequential injection analysis (SIA) methodology for the fluorimetric determination of naproxen is proposed. The developed automatic analytical procedure is based on the complexation of naproxen with β-cyclodextrin (β-CD) yielding an enhanced fluorimetric signal ( λ ex = 280 nm, λ em = 356 nm). Linear calibration plots were obtained for naproxen concentrations up to 1 × 10 −5 mol l −1. The developed methodology exhibited a good precision, with a R.S.D. < 2.1% ( n = 15). The detection limit of the determination was 1.9 × 10 −7 mol l −1 with a sampling rate of about 70 h −1. The automatic method was applied to the determination of naproxen in pharmaceutical formulations. The obtained results were compared with those furnished by the reference procedure and the relative deviations were lower than 3.6%. No interference was found from the excipients usually used in solid pharmaceutical formulations.

Sequential injection spectrophotometric determination of trace amounts of iodide by its catalytic effect on the 4,4′-methylenebis( N,N-dimethylaniline)-chloramine-T reaction

A simple and sensitive sequential injection spectrophotometric procedure is proposed for the determination of trace amounts of iodide in pharmaceutical preparations. The method is based on the catalytic effect of iodide on the (tetra base) 4,4′-methylenebis( N,N-dimethylaniline)-chloramine-T reaction in acidic solution. The method involves a sequential aspiration of 255 μl sample/standard followed by 170 μl tetra base and then 128 μl chloramine-T solutions into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil towards a detector. The resulting colored compound is measured at 600 nm using an UV/Vis-spectrophotometer. All the parameters that affect the reaction were evaluated and the calibration curve is linear over a range of 0.1–6.0 μg l −1 of iodide concentration with detection limit of 0.05 μg l −1. A sample throughput of 80 samples per hour and relative standard deviation of less than 2.0% was achieved. The method is successfully applied for the determination of iodide in three different samples (tablets).

A sequential injection spectrophotometric method for the determination of penicillamine in pharmaceutical products by complexation with iron(III) in acidic media

A simple, robust and sensitive sequential injection spectrophotometric method for the assay of penicillamine (PA) in pharmaceutical formulations is developed. The method was based on the complex formation when PA is reacted with iron(III) solution in hydrochloric acid media. The deep blue colored PA–iron(III) complex produced is monitored at a maximum wavelength of 600 nm. A five level orthogonal array design coupled to genetic algorithm was employed to obtain the optimum experimental conditions for the determination of PA using peak absorbance as the measure of the system's performance criterion. A linear dynamic range for the determination of PA of 25–300 ppm was obtained with a sampling frequency of 50 h −1 and a relative standard deviation of less than 0.98%. The method was successfully applied to the determination of PA in pharmaceutical formulations.