Simultaneous determination of nine phenolic compounds in imitation wild Dendrobium officinale samples using ultrahigh-performance liquid chromatography–tandem mass spectrometry

Dendrobium officinale Kimura et Migo (D. officinale), one of the nine everlasting types of grass, has gained increasing attention owing to its important roles in alternative medicines and drug discovery. Due to its natural resources being in danger of being extinct, imitation wild planting is becoming increasingly common. To assess the product’s quality completely, an efficient ultrahigh performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QQQ-MS/MS) method was established to simultaneously quantify nine phenolic compounds in D. officinale samples. The extraction parameters, including solvent, solvent concentration, solid–liquid ratio, and extraction time, were systematically optimized with the single-factor test. The results demonstrated that extraction with a 1:200 solid-to-liquid ratio of 80% methanol for 1.5 h was the most efficient condition for the extraction of flavonoids. Satisfactory retention times and resolution of the nine analytes were acquired on the Thermo Scientific Hypersil GOLD column with multiple reaction monitoring in negative ion scanning mode. The method was validated to demonstrate its selectivity, linearity, precision, accuracy, and robustness. Thus, the verified UHPLC-QQQ-MS/MS method was successfully applied to the quantification of phenolic components present in D. officinale samples. The results indicated that the quantity and composition of phenolic components in D. officinale from various provenances were significantly different. This work provides a theoretical foundation for the cultivation and assessment of wild D. officinale quality

Identification on acidification damage of external anode system induced by impressed current cathodic protection for reinforced concrete

Impressed current cathodic protection (ICCP) was widely applied for the corrosion control of reinforced concrete. During the ICCP treatment, the anodic reactions happened on the primary anode surface may induce acidification and subsequently pH drop in the vicinity of the anode, leading to damage of the external anode mortar. In this study, the relationship between the applied current (simulating ICCP treatment) on the Ti mesh anode and pH alterations in simulated concrete pore (SCP) solution (with/without chlorides) was investigated. It was found that the applied current slightly reduced the corrosion resistance of Ti mesh; this negative effect was more pronounced in the presence of chlorides. The pH value of SCP solution near Ti mesh anode decreased when the external current was applied. The consumption rate of OH– ion was higher in the chloride-containing SCP solution. A mathematical model was proposed between the electric charge quantity (Q) and OH– concentration (cOH–) in SCP solution near Ti mesh anode. This model is a useful tool to quantitatively identify the acidification damage induced by impressed current from the perspective of pH alternation near Ti mesh anode

Feasibility of Kaolin Tailing Sand to Be As an Environmentally Friendly Alternative to River Sand in Construction Applications

Kaolin tailing sand (KTS) generated as a by-product from kaolin mining sorting, is usually disposed of by delivering to landfills. Effective utilization of KTS in concrete could be an attractive solution for the waste disposal with the value-added advantage of conservation of natural resources and as an eco-friendly alternative for natural river sand (NRS). This paper explored the potential feasibility of recycling KTS, as a substitute for NRS as a fine aggregate in producing cement mortar and concrete. Material characterization tests revealed that KTS possessed a high content of quartz and comparable physical properties to NRS. The fresh and hardened properties of mortars and concretes with varying KTS replacement combinations were determined. The experimental results revealed that the introduction of KTS reduced workability of the resulting mortar, attributed to the high water absorption of KTS particles. However, the introduction of KTS led to a reduction of expansion induced by alkaline silicic acid reaction (ASR) as well as an improvement in flexural strength and compressive strength of the resulting mortar, closely relating to the rough texture and angular nature of KTS. In the case of concrete test, KTS was superior to NRS in enhancing the compressive strength and splitting tensile strength, while decreasing the chloride ion penetration of concrete regardless of whether fly ash or slag was incorporated as a mineral admixture. It is noteworthy that for both mortars and concretes, specimens with 60% of KTS replacement by mass exerted the best mechanical performance. Beyond this ratio led to a slight reduction in mechanical strength, but still acceptable, mainly due to the relatively low inherent strength and depressed packing induced by the flaky shape of KTS particles

pH-Triggered Release Performance of Microcapsule-Based Inhibitor and Its Inhibition Effect on the Reinforcement Embedded in Mortar

The smart release of healing agents is a key factor determining the inhibition efficiency of microcapsules-based corrosion inhibitors for reinforced concrete. In this study, the release behavior of benzotriazole (BTA) in microcapsule-based inhibitors was investigated in mortar sample to clarify the influence of different hydration products on the release process. The results indicated that under high pH environment (pH > 12.4), only about 5% reserved BTA was released from the mortar sample. pH drop resulted in the increased release of BTA from mortar sample. Most BTA in the microcapsule-based inhibitors was released from mortar sample in low pH environment, which was closely related to morphology/composition alterations of hydration products caused by pH drop of the environment. The smart release of BTA dramatically delayed corrosion initiation of reinforced mortar and halted corrosion product accumulation on the steel surface. Therefore, the corrosion resistance of the reinforced mortar was improved after corrosion initiation

Characterization of the passive film formed on the reinforcement surface in alkali activated fly ash: surface analysis and electrochemical evaluation

Due to different ion types and concentration in pore solution, the passive film on the steel surface possesses different characteristics in alkali-activated fly ash (AAFA). In this study, the passive film formed in simulated AAFA pore solution was investigated by surface analysis and electrochemical measurements. The passive film possessed bilayer structure with FeOOH-rich outer layer and FeO-rich inner layer in simulated AAFA pore solution. Further, a firmly adsorbed zeolite-like layer (200 nm) formed on the steel surface. The formation of more protective passive film and adsorbed layer resulted in higher corrosion resistance of the reinforcement in simulated AAFS pore solution

Relationship between microstructure of AgCl film and electrochemical behavior of Ag|AgCl electrode for chloride detection

The electrochemical behavior of Ag|AgCl electrode for chloride detection is closely related to the microstructure of AgCl film on the electrode surface. In this study, the surface properties and electrochemical behavior of Ag|AgCl electrode prepared with different current density were investigated. With a higher current density, the distance for ions diffusion through the boundaries of AgCl grains was reduced, due to the tended growth of AgCl at crystal plane (111) and formation of more spherical AgCl grains and porous AgCl film. As a result, both the electrical resistivity of AgCl film and Rct of Ag|AgCl electrode decreased

The influence of lightweight functional aggregates on the acidification damage in the external anode mortar during cathodic protection for reinforced concrete

Impressed current cathodic protection (ICCP) is an effective corrosion protection and prevention technique for reinforced concrete structures served in chloride-contaminated environment. The acidification damage in the external anode mortar caused by the anodic reactions significantly influences the efficiency of ICCP for reinforced concrete. Therefore, improving the acidification resistance of the external anode mortar is of great importance for the successful application of ICCP treatment. In this study, a novel type of lightweight functional aggregates was proposed to mitigate the acidification damage in the external anode mortar. The influence of the prepared lightweight functional aggregates both on the electrochemical performance of the primary anode and morphology, mineral compositions and microstructure of the secondary mortar were investigated. The results indicated that the lightweight aggregates efficiently mitigated the damage of MMO coating on the primary anode surface, thus maintaining the high stability and catalytic activity of the primary anode. Severe acidification damage happened in the mortar matrix within a distance of 300 μm from the primary anode; beyond this region, the acidification damage was mainly propagated along the interfacial transition zone around the aggregates. Because the lightweight functional aggregates maintained the high alkalinity in the secondary mortar, the acidification damage both in the vicinity of the primary anode and ITZ around aggregates was significantly halted. Therefore, the prepared lightweight functional aggregates can be potentially used for preparing the high performance external anode mortar, further improving the stability and efficiency of ICCP treatment and durability of reinforced concrete structures

Surface characteristics and electrochemical behaviors of passive reinforcing steel in alkali-activated slag

In alkali-activated slag (AAS), the passive film significantly influences the corrosion behavior of the reinforcing steel. The relationship between the surface characteristics and electrochemical performance of the passive reinforcing steel was investigated in simulated alkali-activated slag pore (SSP) solution in this paper. An adsorption aluminate/silicate layer (60 nm) generated on the reinforcing steel surface. Further, due to the influence of S2−, less compact passive film (containing FeS in the inner film) formed, leading to lower passive film resistance. However, the reinforcement still presented slightly higher charge transfer resistance due to the barrier effect of the adsorption layer in SSP solution