Determination of formaldehyde using a novel Pt-doped nano-sized sensitive material: Operating conditions optimization by response surface method.

High working temperature is the main obstacle in the design of chemiluminescence gas sensor. In this paper, a novel formaldehyde gas sensor based on chemiluminescence on nano-Pt/Mo4V6Ti10O47 at lower temperature than 200 °C was reported. Formaldehyde can be oxidized on the catalyst and emit chemiluminescence of specific wavelength. The relative standard deviation (RSD) of the chemiluminescence intensities within 600 h by continually introducing 20 mg/m3 formaldehyde is less than 3%. There is a good linear relationship between the chemiluminescence intensity and the concentration of formaldehyde in the range of 0.007-77.0 mg/m3. The limit of detection (3σ) is 0.002 mg/m3. The experimental operating conditions optimized by response surface method are analytical wavelength of 488.07 nm, working temperature of 138.13 °C and carrier gas velocity of 164.15 mL/min, respectively. The sensitivity of the method can be increased by 4.7% under the optimized working conditions, which is especially important for determination of trace substances. The optimization method is universal for most of multi parameter processes. The sensing properties and chemiluminescence mechanism of formaldehyde on nano-Pt/Mo4V6Ti10O47 were investigated.

Arbuscular mycorrhizal fungus-mediated amelioration of NO2-induced phytotoxicity in tomato.

Atmospheric nitrogen dioxide (NO2) negatively affects plant (crop) growth and development, as well the yield and quality in some regions or environments. Arbuscular mycorrhizal fungus (AMF)-mediated amelioration of NO2-induced plant damage has been reported, but the underlying mechanisms remained unclear. This study explored the beneficial effect of AMF symbiosis on tomato plant responses to NO2 at physiology, biochemistry, and gene expression, with an emphasis on nitrate metabolism, antioxidative defense, and photosynthetic performance. Pot-grown plants were used in the experiments, which were performed in laboratory from February to November 2019. NO2 fumigation with a dose of 10 ± 1 ppm was carried out after 50 d of plant growth, and data were collected following 8 h of fumigation. NO2 fumigation (+NO2) and AMF inoculation (+AMF), alone and especially in combination (NO2 + AMF), increased the gene expression of nitrate- and nitrite reductase, and their enzymatic activity in leaves, such as by 61%, 27%, and 126% for the activity of nitrate reductase, and by 95%, 37%, and 188% for nitrite reductase, respectively, in +NO2, +AMF, and AMF + NO2 plants relative the control (-NO2, -AMF) levels. Following NO2 exposure, +AMF leaves displayed stronger activities of superoxide dismutase, peroxidase and catalase, and higher content of glutathione and ratio of its reduced form to oxidized form, as compared with -AMF ones. Correspondingly, lesser oxidative damage was detected in +AMF than in -AMF plants, as indicated by the contents of H2O2 and malondialdehyde, electrolyte leakage, also by in situ visualization for the formation of H2O2, superoxide anion, and dead cells. The increased antioxidative capacity in +AMF plants was correlated with enhanced expression of antioxidation-related genes. Exposure to NO2 substantially impaired photosynthetic processes in both + AMF and -AMF plants, but an obvious mitigation was observed in the former than in the latter. For example, the total chlorophyll, net photosynthetic rate, stomatal conductance, and ribulose-1,5-bisphosphate carboxylase activity were 18%, 27%, 26%, and 40% higher, respectively, in +AMF than in -AMF plants under NO2 stress. The differential photosynthetic performance was also revealed by chlorophyll fluorescence imaging. We analyzed the expression patterns of some genes related to photosynthesis and carbon metabolisms, and found that all of them exclusively presented a higher expression level in +AMF plants relative to -AMF ones under NO2 stress. Taken together, this study provided evidence that AMF symbiosis played a positively regulatory role in host plant responses to NO2, probably by increasing leaf nitrate metabolism and antioxidative defense, and maintaining the photosynthetic efficiency to some extent, wherein the transcription regulation might be a main target.

Sensitive Carbon Monoxide Gas Sensor Based on Chemiluminescence on Nano-Au/Nd2O3-Ca3Nd2O6: Working Condition Optimization by Response Surface Methodology.

An Au/Nd2O3-Ca3Nd2O6 composite was synthesized by the sol-gel and impregnation method. The EDS spectrum and the transmission electron microscopy image showed that Au atoms are uniformly distributed on the surface of Nd2O3-Ca3Nd2O6 with a size of less than 50 nm. A sensitive carbon monoxide gas sensor based on chemiluminescence at a temperature lower than 200 °C was reported. There is a good linear relationship between the chemiluminescence intensity and the concentration of carbon monoxide in the range of 0.6-125 mg/m3. The detection limit (3σ) is 0.2 mg/m3. The working conditions optimized by the response surface methodology were an analytical wavelength of 620.90 nm, a reaction temperature of 131.63 °C, and a carrier-gas velocity of 105.46 mL/min. The sensitivity of the method can be increased by 4.5% under the optimized working conditions, which is especially important for the determination of trace substances. The carbon monoxide sensor demonstrated in this paper can be used for practical applications. The optimization method is universal for many multiparameter processes.

Determination of Progestin Residues in Fish by UPLC-Q-TOF/MS Coupled with QuEChERS.

A novel method was developed for simultaneous determination of 10 progestin residues in fish by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS) combined with a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. The homogenized samples were dispersed by water, extracted with acetonitrile, and then purified by QuEChERS reagent. The concentrated analytes were detected by UPLC-Q-TOF/MS. High linearities (R 2 > 0.995) and recoveries (85.71-117.08%) at three spiked levels (5, 10, and 20 ng/g) and low relative standard deviation values (<8.83%, n = 7) and limits of detection (0.23-0.66 ng/g) were obtained. This method is simple, rapid, reliable, sensitive, and efficient and can be used for monitoring of progestin residues in fish. This method provides a strong guarantee to deal with food emergencies for the laboratory, provides technical support for the screening and quantitative detection of progesterone in fish, and provides technical support for the food safety of aquatic products.