An automatic potentiometric setting dynamic pH titration method for the determination of sodium bicarbonate in compositions of smoke-type fireworks was developed. After wetting the sample with 0.1 mL ethanol, added 60 mL of deionized water for dissolution, ultrasound for 10 min, filtered and removed the insoluble matter, and then used a potentiometric titrator to drop 0.1 mol/L of hydrochloric acid. The experimental results showed that the limit of quantitation was 0.1%, the recoveries were 96.1–104.8% and the relative standard deviation was 0.56–3.11% when the sample weigh 0.2 g. The automatic potentiometric setting dynamic pH titration method is simple to operate and can accurately and quickly determine the content of sodium bicarbonate in compositions of smoke-type fireworks.
Ping Yan,Keke Zhang,Lingyu Wang,Wenjun Tong,David D. Y. Chen
Dynamic pH junction is an online focusing method in CE based on the electrophoretic mobility difference of analytes in the sample matrix and the background electrolyte. An advantage of this method over the conventional CE is that the sensitivity can be significantly improved. By injecting a long sample plug in the capillary and focusing the analytes at the pH boundary between the background electrolyte and sample matrix, the LOD can be improved by 10–100 folds. The dynamic pH junction method can be easily coupled with ESI-MS. In this work, we used this method for the analysis of microcystins (MCs). The detection limits and dynamic ranges were studied. The separation was optimized by adjusting the injection time, and concentrations and pH values of the background electrolyte. The optimization of analyte focusing leads to enhanced detection response compared to conventional injections, achieving 200–400 fold higher averaged peak heights for four microcystin (MC) variants. More importantly, this method was successfully used for the quantitative analysis of microcystins (MCs) in crude algae samples from natural water bodies, making it promising for practical applications.
Haize Jin,Chenxi Qiu,Yansong Li,Junyi Liu,Dabo Zhang,Qiao Chen,Xuefeng Lu,Cuixia Li,Qikun Wang
The crux to practical application of geopolymer adsorbents for antibiotics that are easily protonated and deprotonated is to clarify the dynamic adsorption mechanism of geopolymer with intrinsic alkaline release. The adsorption properties, adsorption mechanism, adsorption-desorption cycle and waste adsorbent regeneration based on the geopolymer adsorbent for adsorbing tetracycline under the spontaneous dynamic pH conditions were systematically investigated by experiment, characterization and density functional theory. The results confirmed that the structures of tetracycline depended on dynamic pHs of adsorption systems changed by geopolymer adsorbent. The electrostatic interaction assisted by hydrogen-bonding and n-π interaction dominated the adsorption process when the dynamic pHs were less than 7. And the hydrogen-bonding and n-π interaction provided the possibility of weak adsorption effect in highly alkaline environments. The geopolymer powder exhibited outstanding adsorption efficiency (∼95.62%, 30 min) due to the strong electrostatic adsorption between electronegative skeleton of geopolymer and zwitterions species tetracycline under dynamic pH range of 4–6.3 and fitted the pseudo-second-order model. The outstanding competitive adsorption properties in NaCl solution, adsorption (4 times)-desorption (3 times) cycle properties and regenerative property of waste adsorbent were exhibited. The mechanism study based on the dynamic pHs which is closer to actual conditions can provide important reference for practical application of easy preparation and low cost geopolymer adsorbents.
危险品化学品经营许可证（带存储）