The development of flow-based techniques, including flow injection and sequential injection analysis, offers an excellent on-line alternative with respect to conventional wet chemical assays with the merits of promoted automation, reduced sample/reagent consumption, minimized sample contamination, improved accuracy and analysis throughput with programmable fluidic manipulations. The superb compatibility to external equipments, designable flow manifolds and enclosed analytical environment make flow-based technique a promising potential platform for the bioassays. In the present mini-review, the up-to-date applications of flow injection/sequential injection approaches in protein assays including automated quantification, on-line qualitative separation, adsorption and extraction, activity investigations and immobilization studies are summarized, and future perspectives are discussed.

View full abstract

In the article, various methods of flow injection and sequential injection analyses are considered. The relative advantages and disadvantages are investigated. The stepwise injection analysis is proposed as a new universal flow method of analysis which means maximum strict reproduction of all the analytical stages which are typical for automated stationary methods. The opportunities of the new method which can be applied to the sample analysis in any aggregative state are illustrated by the examples of phosphateions in urine, anionic surfactants and nitrate- and nitrite-ions in water, hydrogen sulfide in hydrocarbon gases, and phosphates in water-soluble mineral fertilizer.

View full abstract

Carbon paste and PVC electrodes were constructed and incorporated in the flow injection system for potentiometric determination of amantadine (AM), metformin (MF), ranitidine (RN) and trimetazidine (TRMZ). Wall-jet and continuous flow cells were designed where the wall-jet cell showed better performance regarding the sample dispersion and sensitivity to the change in flow rate. CPEs were more suitable for incorporation in the flow-injection systems due to its fast response, mechanical strength and lifetime. The proposed electrodes showed linear calibration graphs in the concentration range from 10^-5 to 10^-1 mol L^-1 with Nernstian slopes values of 61.4±1.7, 60.1±0.99, 65.5±2.0 and 30.9±1.1 mV decade^-1 for AM, MF, RN and TRMZ, respectively. The developed electrodes have been successfully applied for flow injection potentiometric determination of the investigated drugs in their pharmaceutical formulation with sample output of 120 samples h^-1 and the advantage of simplicity, accuracy and automation feasibility.

View full abstract

A new and fast sequential micro injection analysis (SIA) method for an accurate assay of chlorpheniramine maleate, based on its oxidation by acidified potassium permanganate was optimized. A 23 factorial design was applied for both surface plot and factor effect. The experimental conditions were fully optimized so that the method is suitable for industrial application. Some of the optimum parameters were found to be 35μl of 1×10^-3 mol l^-1 sulfuric acid, 30μl of 1×10^-3 mol l^-1 permanganate, and 30μl of chlorpheniramine maleate with a flow rate of 25μl s^-1. Beer, s law was obeyed in the concentration range of 20 – 150 ppm with regression calibration equation (R=0.0016C+0.0064) and correlation coefficient of 0.9998. Chlorpheniramine maleate assay showed an excellent mean recovery and R. S. D. of; ± 1.8% for synthetic sample, ± 1% for Allerfin injection and ± 1.1% for Anallerg tablets. The method was applied to tablet forms as well as injection forms and validated with the British Pharmacopoeia. The developed new SIA method is fully automated, rapid, sensitive, accurate and cost-effective, and therefore suitable for routine pharmaceutical analysis application. Accordingly, it is recommended and proposed to be used in pharmaceutical industries

View full abstract

The Non-Segmented Biphasic Flow System (NSBF) was applied in total phosphorous determination. The oxidation was performed in a reaction coil heated by electrical resistances. The high efficiency of heating in such system allows the simultaneous formation of liquid and vapor phases without segmentation. This unusual condition has reduced the hydrodynamic pressure and thus providing good work conditions. The system was based on the organic matter oxidation by persulfate in acid medium. The phosphomolybdic acid-green malachite ion-association was spectrophotometrically quantified in 650 nm. The analytical range was from 26.0 μgP.L^-1 to 320 μg P.L^-1 and a limit of detection of 9 μgP.L^-1 was obtained, with an analytical sensitivity of 0.27 L.mg^-1. The analytical frequency was 40 samples per hour with a repeatability of 4.7% (n = 10).

View full abstract

A simple flow injection chemiluminescence method was proposed for the determination of neomycin in commercial pharmaceutical formulations. The chemiluminescence reaction is based on the enhancing effect of neomycin on the chemiluminescence reaction between luminol-hydrogen peroxide catalysed by potassium ferrocyanide in the Triton X-100 alkaline media. Neomycin solution was injected into a water carrier stream and then mixed with hydrogen peroxide in the presence of Triton X-100 solutions. The reaction mixture was then merged at a Y-piece with a reagent stream consisting of potassium ferrocyanide and luminol in alkaline solution. The elicited chemiluminescence intensity was measured by a photomultiplier tube operated at a voltage of 880 V. The linear detection range was found to be 0.1–14 μg mL^-1. The relative standard deviation for 12 replicates was found to be 2.90% at 4 μg mL^-1 of neomycin standard solution with the detection limit of 0.01 μg mL^-1, whilst the sample throughput of 152 h^-1. The proposed FI-CL method was successfully applied for the determination of neomycin in pharmaceutical formulations. The method validation has been compared versus spectrophotometric method.

View full abstract

This paper reports the development of a reversed FIA system for the spectrophotometric determination of cetylpyridinium chloride (CPC) in pharmaceutical products. The method is based on the reaction between CPC and Eriochrome Black T (EBT) with the formation of a product with strong absorption at 645 nm. At optimized conditions the reversed FIA system was able to process 40 samples per hour with a detection limit of 0.24 μg mL^-1 and a quantification limit of 0.80 μg mL^-1. Recovery rates between 92 and 107% were obtained in the analysis of pharmaceutical products using the proposed methodology.

View full abstract

The method developed in this study utilizes the SIA technique with spectrophotometric detection. Potassium permanganate is used as an oxidant in slightly acidic medium of 6.0 x 10^-6 mol L^-1 sulfuric acid and the oxidized form of the drug is monitored spectrophotometrically at a wavelength of 450 nm for quantitative determination. The method has been validated and successfully applied to the assay of the compound formulated in pharmaceutical preparations. The calibration curve was linear within a range of 30 – 135 μg mL^-1 with correlation coefficients of 0.998 and limits of detection (LOD) and limits of quantification (LOQ) of about 0.24 μg mL^-1 and 0.7 μg mL^-1 respectively. The method proved to be of high precision with a relative standard deviation (RSD) of about 1.5 %. Furthermore, the SIA method gave results for real samples (tablets) containing 50 μg mL^-1 diclofenac sodium in good agreement with those obtained by the standard BP method. No statistical differences at the 95 % confidence level on applying the t-test were observed between the values obtained by the two methods. Thus, the proposed SIA method is reliable, faster than the standard BP potentiometric method and lends itself to automation. The advantages of the SIA technique and the newly adopted method over other conventional techniques and the reported existing standard methods such as rapidity, economy, and automation have been documented. The overall benefit of the SIA technique has also been highlighted.

View full abstract

A simple water extract of a flower was exploited as a natural reagent for acidity assay. The natural reagent from Gomphrena globosa was obtained by simple extraction and introduced into a simple lab-on-chip (LOC). The natural reagent adjusted to pH 9 was loaded into the vertical channel of the LOC, and then acetic acid standard/sample was injected into the horizonal channel of the LOC. The injected acetic acid solution migrated downward and merged with the natural reagent. The absorbance spectrum was monitored at the detection point. A liner calibration curve for acetic acid was obtained in the range of 3–7 % (w/w). The proposed method was applied to the determination of acetic acid in vinegar samples.

View full abstract