Colorimetric assay based on peroxidase-like activity of dodecyl trimethylammonium bromide-tetramethyl zinc (4-pyridinyl) porphyrin for detection of organophosphorus pesticides.

A simple and sensitive colorimetric assay for detecting organophosphorus pesticides (OPs) was developed based on 3,3',5,5'-tetramethylbenzidine (TMB)/hydrogen peroxide (H2O2)/dodecyl trimethylammonium bromide (DTAB)-tetramethyl zinc (4-pyridinyl) porphyrin (ZnTPyP). In this system, based on the peroxidase-like activity of DTAB-ZnTPyP, H2O2 decomposes to produce hydroxyl radicals, which oxidize TMB, resulting in blue oxidation products. The OPs (trichlorfon, dichlorvos, and thimet) were first combined with DTAB-ZnTPyP through electrostatic interactions. The OPs caused a decrease in the peroxidase-like activity of DTAB-ZnTPyP due to spatial site blocking. At the same time, π-interactions occurred between them, and these interactions also inhibited the oxidation of TMB (652 nm), thus making the detection of OPs possible. The limits of detection for trichlorfon, dichlorvos, and thimet were 0.25, 1.02, and 0.66 µg/L, respectively, and the corresponding linear ranges were 1-35, 5-45, and 1-40 µg/L, respectively. Moreover, the assay was successfully used to determine OPs in cabbage, apple, soil, and traditional Chinese medicine samples (the recovery ratios were 91.8-109.8%), showing a great promising potential for detecting OPs also in other complex samples.

[Research progress on common pesticide residues in Chinese medicinal materials].

Chinese medicinal materials are the precious resources of China and favored by patients at home and abroad because of their natural sources and curative effects. Pesticides are often used to prevent and control diseases and insect pests and regulate the growth of Chinese medicinal plants, so as to improve the yield and quality of Chinese medicinal materials. Most of the pesticides can play a role in pest control through systemic action, stomach toxicity, contact, fumigation and other ways, especially the systemic pesticides can kill hidden pests by entering the Chinese medicinal plants. Despite the good pest control effect, it is difficult to remove the systemic pesticides by simple cleaning, which poses a great risk to the safety of Chinese medicinal materials. At the same time, excessive or non-standard use of pesticides leads to serious pesticide residues in Chinese medicinal materials, which affects not only the quality and efficacy of the materials and harm human health but also the international development of Chinese medicinal materials industry. Pesticide residues have become a bottleneck affecting the industry development and hindering the export of Chinese medicinal materials. Therefore, it is of great significance to study how to quickly, sensitively, and accurately detect and remove pesticide residues in Chinese medicinal materials. We reviewed the common pesticide residues in Chinese medicinal materials in recent years in terms of characteristics, harm, and detection and removal techniques, and discussed the future development of the detection and removal deve-lopment. With this review, we aimed to provide a reference for the quality control of Chinese medicinal materials and promote the healthy development of Chinese medicine industry.

Visual paper-based sensor for the highly sensitive detection of caffeine in food and biological matrix based on CdTe-nano ZnTPyP combined with chemometrics.

Caffeine naturally occurs in tea and cocoa, which is also used as an additive in beverages and has pharmacological effects such as refreshing, antidepressant, and digestion promotion, but excessive caffeine can cause harm to the human body. In this work, based on the specific response between nano zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H-23H-porphine (nano ZnTPyP)-CdTe quantum dots (QDs) and caffeine, combined with chemometrics, a visual paper-based sensor was constructed for rapid and on-site detection of caffeine. The fluorescence of QDs can be quenched by nano ZnTPyP. When caffeine is added to the system, it can pull nano ZnTPyP off the surface of the QDs to achieve fluorescence recovery through electrostatic attraction and nitrogen/zinc coordination. The detection range is 5 × 10-11~3 × 10-9 mol L-1, and the detection limit is 1.53 × 10-11 mol L-1 (R2 = 0.9990) (S/N = 3). The paper-based sensor constructed exhibits good results in real samples, such as tea water, cell culture fluid, newborn bovine serum, and human plasma. Therefore, the sensor is expected to be applied to the rapid instrument-free detection of caffeine in food and biological samples.Graphical abstract.