ABSTRACT
A chemosensor for on-site sensing of ammonia precursor in concrete to avoid a problem of ammonia emission into the indoor space of concrete buildings was designed and implemented. It was found that aqueous extracts of concrete samples containing antifreeze additives and excreting ammonia were colored in the presence of p-dimethylaminobenzaldehyde. This phenomenon was used for the fast visual sensing of main ammonia precursor (urea) in concrete for the first time. The developed sensor consisted of a sensing solid phase based on an adsorbent modified with p-dimethylaminobenzaldehyde. Various adsorbents were investigated for the immobilization of the reagent and it was established that silica adsorbent Silochrom C-120 provided effective retention of the reagent and Schiff's base formation during the sampling. Moreover, Silochrom C-120 modified with ascorbic acid was proposed to eliminate the oxidant interference. The sensor displayed excellent selectivity and sensitivity with the visual detection limit of 15 mg kg-1 in terms of urea. The chemosensor was successfully applied by builders on different construction sites. Sample preparation and sensing times were about 2 min and 1 min, respectively.
ABSTRACT
Sequential Injection Chromatography (SIC) evolved from fast and automated non-separation Sequential Injection Analysis (SIA) into chromatographic separation method for multi-element analysis. However, the speed of the measurement (sample throughput) is due to chromatography significantly reduced. In this paper, a sub-1min separation using medium polar cyano monolithic column (5mm×4.6mm) resulted in fast and green separation with sample throughput comparable with non-separation flow methods The separation of three synthetic water-soluble dyes (sunset yellow FCF, carmoisine and green S) was in a gradient elution mode (0.02% ammonium acetate, pH 6.7 - water) with flow rate of 3.0mLmin-1 corresponding with sample throughput of 30h-1. Spectrophotometric detection wavelengths were set to 480, 516 and 630nm and 10Hz data collection rate. The performance of the separation was described and discussed (peak capacities 3.48-7.67, peak symmetries 1.72-1.84 and resolutions 1.42-1.88). The method was represented by validation parameters: LODs of 0.15-0.35mgL-1, LOQs of 0.50-1.25mgL-1, calibration ranges 0.50-150.00mgL-1 (r>0.998) and repeatability at 10.0mgL-1 of RSD≤0.98% (n=6). The method was used for determination of the dyes in "forest berries" colored pharmaceutical cough-cold formulation. The sample matrix - pharmaceuticals and excipients were not interfering with vis determination because of no retention in the separation column and colorless nature. The results proved the concept of fast and green chromatography approach using very short medium polar monolithic column in SIC.
Subject(s)
Chemistry, Pharmaceutical/methods , Chromatography , Coloring Agents , Drug Compounding , WaterABSTRACT
A novel stepwise injection fluorometric method for the determination of epinephrine in human urine has been developed. In the current study, the stepwise injection analysis (SWIA) was successfully combined with on-line in-syringe cloud point extraction (CPE) and fluorometric detection. The procedure was based on the epinephrine derivatization in the presence of o-phenylenediamine followed by the preconcentration stage based on the CPE with the nonionic surfactant Triton X-114. After the phase separation into a syringe of the flow system, the micellar phase containing the epinephrine derivative was transported to a fluorometric detector. The excitation and emission wavelengths were set at 447 nm and 550 nm, respectively. The conditions of epinephrine derivatization and CPE have been studied. The calibration plot constructed using the developed procedure was linear in the range of 1·10(-11)-5·10(-7) mol L(-1). The limit of detection, calculated as 3 σ of a blank test (n = 10), was found to be 3·10(-12) mol L(-1). The proposed method was successfully applied for the determination of epinephrine in human urine samples.
