Relative Standard Detection Research Articles

Simultaneous Determination of Daidzein, Genistein and Formononetin in Coffee by Capillary Zone Electrophoresis

Coffee is a favorite and beverage in Western countries that is consumed daily. In the present study, capillary zone electrophoresis (CE) was applied for the separation and quantification of three isoflavones including daidzein, genistein and formononetin in coffee. Extraction of isoflavones from the coffee sample was carried out by extraction and purification process using ether after the acid hydrolysis with the antioxidant butylated hydroxy-toluene (BHT). The experimental conditions of the CE separation method were: 20 mmol/L Na2HPO4 buffer solution, 25 kV applied voltage, 3 s hydrodynamic injection at 30 mbar, and UV detection at 254 nm. The results show that the three compounds can be tested within 10 min with a linearity of 0.5–50 µg/mL for all three compounds. The limits of detection were 0.0642, 0.134, and 0.0825 µg/mL for daidzein, formononetin and genistein, respectively. The corresponding average recovery was 99.39% (Relative Standard Detection (RSD) = 1.76%), 98.71% (RSD = 2.11%) and 97.37% (RSD = 3.74%).

Determination of Salicylic Acid in Human Serum and Urine Samples by High-Performance Liquid Chromatography with Post-column Ru(bipy)32+-Ce(SO4)2 Chemiluminescence Detection

A sensitive, novel and rapid chemiluminescence (CL) method combined with high-performance liquid chromatography (HPLC) separation for the determination of salicylic acid (SA) is described in this work. The method was based on the fact that SA could significantly enhance the CL of the reaction of cerium sulfate and the tris(2,2-bipyridyl) ruthenium(II) CL system in the presence of acid. Under the optimal conditions, the CL intensity was linear over concentrations of SA in the range of 0.02-10 × 10(-6) g/mL, with a detection limit of 8 × 10(-9) g/mL (S/N = 3). Also, the relative standard detection was 2.2% for 1.0 × 10(-7) g/mL (n = 11). The proposed method has been successfully applied to the analysis of SA in human serum samples and urine samples with satisfactory results.

Design and construct of a new detector for gas chromatography based on continuous negative corona discharge

In this work, a new detector was designed and constructed based on negative corona discharge. This detector can be used separately or as a detector in gas chromatography. The detector and chromatographic variables including cell temperature, gas flow rates, voltage between the two electrodes, and column temperature were optimized. Chloroform was used as a test compound to evaluate the performance of the detector. The detection limit of chloroform was obtained 0.78 ng∕ml and its dynamic range was over the range of 2-840 ng∕ml. The relative standard detection was about 6% for the limit of quantification. This detector is able to be used as an alternative for analysis of compounds containing electronegative elements.