Determination of Potassium, Sodium, and Total Alkalies in Portland Cement, Fly Ash, Admixtures, and Water of Concrete by a Simple Flow Injection Flame Photometric System

A simple flow injection with flame photometric detection has been developed for determination of sodium, potassium, and total alkalies in portland cement, fly ash, admixtures, and water of concrete. A liquid sample or a digest of solid sample was injected into a water carrier stream which flowed to a flame photometer. A change in emission intensity at a selected wavelength was recorded as a peak. An amplifier circuit was fabricated, which helped improve sensitivity of the flame photometer. Calibration graphs in the range of 0.05–1.0 mg L−1 and 1.0–20.0 mg L−1 were obtained with a detection limit of 0.02 mg L−1, for both potassium and sodium determination. Relative standard deviations for 11 replicates of injecting of 10 mg L−1 potassium and sodium solutions were 1.69 and 1.79%, respectively. Sample throughput of 120 h−1 was achieved. The proposed method was successfully applied to portland cement, fly ash, admixtures, and water samples validated by the ASTM standard method and certified reference materials of portland cement

A new portable toluidine blue/aptamer complex-on-polyethyleneimine-coated gold nanoparticles-based sensor for label-free electrochemical detection of alpha-fetoprotein

The quantification of alpha-fetoprotein (AFP) as a potential liver cancer biomarker which is generally found in ultratrace level is of significance in biomedical diagnostics. Therefore, it is challenging to find a strategy to fabricate a highly sensitive electrochemical device towards AFP detection through electrode modification for signal generation and amplification. This work shows the construction of a simple, reliable, highly sensitive, and label-free aptasensor based on polyethyleneimine-coated gold nanoparticles (PEI-AuNPs). A disposable ItalSens screen-printed electrode (SPE) is employed for fabricating the sensor by successive modifying with PEI-AuNPs, aptamer, bovine serum albumin (BSA), and toluidine blue (TB), respectively. The AFP assay is easily performed when the electrode is inserted into a small Sensit/Smart potentiostat connected to a smartphone. The readout signal of the aptasensor derives from the electrochemical response of TB intercalating into the aptamer-modified electrode after binding with the target. The decrease in current response of the proposed sensor is proportional to the AFP concentration due to the restriction of the electron transfer pathway of TB by a number of insulating AFP/aptamer complexes on the electrode surface. PEI-AuNPs improve SPE’s reactivity and provide a large surface area for aptamer immobilization whereas aptamer provides selectivity to the target AFP. Consequently, this electrochemical biosensor is highly sensitive and selective for AFP analysis. The developed assay reveals a linear range of detection from 10 to 50000 pg mL−1 with R2 = 0.9977 and provided a limit of detection (LOD) of 9.5 pg mL−1 in human serum. With its simplicity and robustness, it is anticipated that this electrochemical-based aptasensor will be a benefit for the clinical diagnosis of liver cancer and further developed for other biomarkers analysis

Determination of chloride in admixtures and aggregates for cement by a simple flow injection potentiometric system

a b s t r a c t A simple flow injection system using three 3-way solenoid valves as an electric control injection valve and with a simple home-made chloride ion selective electrode based on Ag/AgCl wire as a sensor for determination of water soluble chloride in admixtures and aggregates for cement has been developed. A liquid sample or an extract was injected into a water carrier stream which was then merged with 0.1 M KNO 3 stream and flowed through a flow cell where the solution will be in contact with the sensor, producing a potential change recorded as a peak. A calibration graph in range of 10-100 mg L −1 was obtained with a detection limit of 2 mg L −1 . Relative standard deviations for 7 replicates injecting of 20, 60 and 90 mg L −1 chloride solutions were 1.0, 1.2 and 0.6%, respectively. Sample throughput of 60 h was achieved with the consumption of 1 mL each of electrolyte solution and water carrier. The developed method was validated by the British Standard methods

Stopped-flow injection method for determination of phosphate in soils and fertilisers

A stopped-flow injection system for the determination of phosphate has been developed. It involves the phosphate-molybdate-ascorbic acid reactions in the molybdenum blue method. The system is controlled by a semi-automatic stopped-FI analyser with a light emitting diode (LED)-colorimeter for monitoring the absorbance change relating to the concentration of a reaction product formed during the stopping period while the injected zone of a standard or sample is being in the flow cell. The slope of the FIAgram obtained is linearly proportional to the reaction rate, which depends on the phosphate concentration. Effects of concentration of reagents, viz. sodium molybdate, ascorbic acid and nitric acid, on the slope of the FIAgram were studied. The suitable concentration is 0.02 M, 0.25 %w/v and 0.15 M, respectively. A linear calibration graph in the range of 0.3-6.0 mg P L-1 was employed for the determination of phosphate in soil and fertiliser samples. The results obtained agree well with those from a standard spectrophotometric method

Stopped-flow injection spectrophotometric method for determination of chlorate in soil

A stopped-flow injection (FI) spectrophotometric procedure based on iodometric reaction for the determination of chlorate has been developed. Standard/sample was injected into a stream of potassium iodide solution and then merged with a stream of hydrochloric acid solution to produce triiodide. By stopping the flow while the sample zone is being in a mixing coil, a slow reaction of chlorate with iodide in acidic medium was promoted to proceed with minimal dispersion of the triiodide product zone. When the flow started again, a concentrated product zone was pushed into a flow cell and a signal profile due to light absorption of the product was recorded. Employing a lab-built semi-automatic stopped-FI analyser, the analysis can be performed with higher degree of automation and low chemical consumption. Linear calibration graph in the range of 5-50 mg ClO3- L-1 was obtained, with detection limit of 1.4 mg ClO3- L-1. Relative standard deviation of 2.2% (30 mg ClO3- L-1, n=10) and sample throughput of about 20 h-1 were achieved. The system was applied to soil samples and validated by batch spectrophotometric and standard titrimetric methods

Antioxidant and Moisturizing Effect of Camellia assamica Seed Oil and Its Development into Microemulsion

The present study aimed to investigate the fatty acid content, and antioxidant and moisturizing effect of Camellia assamica seed oil (CA). Additionally, microemulsions containing CA were also developed for topical use. The antioxidant activity of CA and two commercial Camellia oleifera seed oils were investigated by means of 1,1-diphenyl-2-picrylhydrazy radical (DPPH) assay and lipid peroxidation by ferric thiocyanate method. Moreover, the in vitro skin moisturizing effect was investigated on stillborn piglet skin by using a Corneometer®. CA microemulsions were developed and characterized by photon correlation spectroscopy, rheometer, and heating-cooling stability tests. The results revealed that the major fatty acid components of CA were cis-9-oleic acid, cis-9,12-linoleic acid, and palmitic acid. CA had a significantly higher lipid peroxidation inhibition and DPPH scavenging capacity compared to the commercial oils (p < 0.05). Lipid peroxidation inhibition of CA was 39.2% ± 0.6% at 37.5 mg/mL and the IC50 value of DPPH assay was 70.8 ± 27.1 mg/mL. The skin moisture content after applying CA, commercial oils, and tocopheryl acetate were significantly higher than untreated skin (p < 0.05) and the moisturizing efficacy increased with time. Interestingly, radical scavenging and antioxidant effect of CA microemulsions were significantly higher than the native oil even after the stability test (p < 0.05). In conclusion, incorporating CA into microemulsion increased its antioxidant activity indicating that it would be beneficial as a cosmeceutical application for anti-aging