Nucleic acid aptamer based thermally oxidized porous silicon/zinc oxide microarray chip for detection of ochratoxin A in cereals.

A nucleic acid aptamer based thermally oxidized porous silicon/zinc oxide microarray chip was constructed for the detection of ochratoxin A. The hybrid chains formed by aptamer and complementary chains labeled with fluorescent groups and fluorescent burst groups were used as recognition molecules, and the detection of toxins was accomplished on the chip by the principle of fluorescence signal burst and recovery. The modified QuEChERS method was used for sample pretreatment and the performance of the method was evaluated. The results showed that the linear range was 0.02 âˆ¼ 200 ng/kg with the detection limit of 0.0196 ng/kg under the optimal detection conditions. The method was applied to different cereals with the recoveries of 90.30 âˆ¼ 111.69 %. The developed microarray chip has the advantages of being cost-effective, easy to prepare, sensitive and specific, and can provide a new method for the detection of other toxins.

A smartphone-assisted colorimetric aptasensor based on aptamer and gold nanoparticles for visual, fast and sensitive detection of ZEN in maize.

A simple, fast, low cost, sensitive, intuitive, visual, label-free, and smartphone-assisted aptamer sensor based on colorimetric assay for the measurement of zearalenone was constructed. The nucleic acid aptamer of zearalenone was used as the recognition element and gold nanoparticles were used as the indicator. Several factors that could influence sensitivity, including the concentration of aptamer and NaCl, and incubation time, and specificity, have been investigated. The results showed that under the optimal conditions, the signal had a good linear relationship when zearalenone concentration is 5-300 ng/mL. A linear regression equation is Y = 0.0003X + 0.5128 (R2 = 0.9989) and a limit of detection is 5 ng/mL. The specificity of the sensor was good. Zearalenone in maize samples were successfully measured. The recoveries of Zearalenone are 81.3 %-96.4 %. The whole process takes only 15 min to complete. The smartphone assisted colorimetric aptamer sensor can be used for the detection of zearalenone in maize.

AFB1 colorimetric aptamer sensor for the detection of AFB1 in ten different kinds of miscellaneous beans based on gold nanoparticles and smartphone imaging.

A simple, rapid, low-cost, sensitive, intuitive, visual, label-free, colorimetric smartphone-assisted assay was developed for the measurement of aflatoxin B1 in miscellaneous beans. Ten different kinds of miscellaneous beans were treated and measured by modified QuEChERS(Quick、Easy、Cheap、Effective、Rugged、Safe) method with aflatoxin B1 nucleic acid aptamer as a recognition element and gold nanoparticles as indicators. Several factors influencing its sensitivity were investigated, including consumes and NaCl concentrations, as well as incubation time and specificity. The results showed a good linear relationship between concentrations of 0.2-8.0 ng/g under optimal conditions. With a detection limit of 0.08 ng/g, the linear regression equation was Y = 0.024X + 0.4615 (R = 0.9989). Sensor specificity is good. The content of aflatoxin B1 in bean samples was determined successfully. The recovery of aflatoxin B1 ranged from 87.18% to 110.24%. The whole thing took 15 min. This smartphone-assisted colorimetric aptamer sensor can be used to detect aflatoxin B1 in beans.

Rapid and sensitive detection of methyl parathion in rice based on carbon quantum dots nano-fluorescence probe and inner filter effect.

A highly sensitive fluorescent sensing system of novel carbon quantum dots nano-fluorescent probe based on corn stalks was established for the determination of methyl parathion by alkaline catalytic hydrolysis and inner filter effect mechanism. The carbon quantum dots nano-fluorescent probe was prepared from corn stalks using an optimized one-step hydrothermal method. The detection mechanism of methyl parathion was revealed. The reaction conditions were optimized. The linear range, sensitivity and selectivity of the method were evaluated. Under the optimal conditions, the carbon quantum dots nano-fluorescent probe exhibited high selectivity and sensitivity to methyl parathion, achieving a linear range of 0.005-14 µg/mL. The fluorescence sensing platform was applied to the detection of methyl parathion in rice samples, and the results showed that the recoveries range from 91.64 to 104.28 %, and the relative standard deviations were less than 4.17 %. The detection limit for methyl parathion in rice samples was 1.22 µg/kg, and the limit of quantitation (LOQ) was 4.07 µg/kg, which was very satisfactory.

Ionic liquid-based cloud point extraction five organophosphorus pesticides in coarse cereals.

Organophosphorus pesticides will not only affect human health, but will also have serious impacts on the ecological environment. A simple, economical, safe, efficient, green and pollution-free and highly sensitive method was successfully established to analyze organophosphorus pesticides in different coarse cereals' samples. Under the optimal experimental conditions, the method was linear, the correlation coefficient are higher than 0.9639. The detection limits of trichlorfon, chlorpyrifos, phoxim, fenthion, and diazinon were 2.6, 2.0, 4.3, 2.0, and 2.8 µg/kg. The recoveries ranged from 92.8 to 105.2%, the relative standard deviation is less than 5.2%. The results obtained show that the proposed method has the advantages of economy, safety, green and pollution-free, high recovery efficiency, simple use of the instrument, simple operation, and can be used with many subsequent instruments.

Analysis of metabolites and metabolic pathways in three maize (Zea mays L.) varieties from the same origin using GC-MS.

Metabolites of the Jinyu 88, Huanong 18, and Demeiya 9 maize varieties from the same origin were isolated and identified by GC-MS, and the specific metabolites and metabolic mechanisms of these three varieties of maize were preliminarily analysed and discussed. The metabolites were extracted with 80% methanol and derived with N,O-bis(trimethylsilyl)trifluoroacetamide. A total of 59 metabolites were identified. The specific metabolites of these three varieties of maize were identified. Four possible unknown-structure metabolites were hypothesized. The results showed that the specific metabolites of JY88 were only involved in fatty acid metabolism. The specific metabolites of HN18 were determined to be involved in fatty acid metabolism, glucose metabolism, and phytosterol metabolism. The specific metabolites of DM9 were observed to participate in glucose metabolism and fatty acid metabolism. The disease resistance of HN18 was higher than that of DM9, and its grain bulk density was higher than that of DM9. JY88 was determined to be significantly different from the other two varieties, and its appearance and disease resistance were worse than those of the other two varieties. The variety with the highest nutritional value was determined to be HN18, and the variety with the lowest nutritional value was JY88. This finding indicated that different maize varieties from the same origin had different metabolites and different metabolic mechanisms, which caused the three maize varieties to exhibit different characteristics and qualities.

Extraction of acetanilide herbicides in naked oat (Avena nuda L.) by using ionic-liquid-based matrix solid-phase dispersion-foam flotation solid-phase extraction.

The herbicides in naked oat (Avena nuda L.) samples were extracted, separated, and determined by using ionic-liquid-based matrix solid-phase dispersion-solvent flotation coupled with high-performance liquid chromatography. The experimental parameters were optimized and evaluated by a univariate method and orthogonal experiment. A good linear relationship was obtained in the range of 5-5000 µg/kg, and the linear correlation coefficient are between 0.9989∼0.9993. The quantification limits for alachlor, metazachlor, propanil, acetochlor, pretilachlor, metolachlor, and butachlor are 5.03, 2.62, 2.73, 4.58, 7.28, 5.05, 5.78 µg/kg, respectively. The average recoveries of the acetanilide herbicides at spiked concentrations of 10, 100, and 500 µg/kg ranged from 92.1 to 104.7%, and relative standard deviations were equal to or lower than 2.9%.

Extraction and separation of acetanilide herbicides in beans based on metal-organic framework MIL-101 (Zn) as sorbent.

An extraction method based on metal-organic framework has been developed and applied to acetanilide herbicides, including metazachlor, propanil, pretilachlor, and butachlor, in black beans, red beans, and kidney beans. The acetanilide herbicides are extracted with a mixture of ethyl acetate and n-hexane. The extract solution is absorbed and purified with metal-organic framework MIL-101 (Zn). The separation and determination of four acetanilide herbicides were implemented by high-performance liquid chromatography. The experimental parameters were evaluated by a univariate method and orthogonal experiments. The presented method can obtain effective extraction and purification. The detection limits for metazachlor, propanil, pretilachlor, and butachlor were 0.58, 0.90, 1.78 and 1.18 µg/kg, respectively. The average recoveries of the acetanilide herbicides at spiked concentrations of 10, 50, and 100 µg/kg ranged from 86.9% to 119.0%, and relative standard deviations were equal to or lower than 2.80%.

Separation and concentration of sulfonylurea herbicides in milk by ionic-liquid-based foam flotation solid-phase extraction.

The ultrasound-assisted ionic liquid foam flotation solid-phase extraction of sulfonylurea herbicides in milk was developed and validated. The proteins and lipids were isolated from the sample matrix by adding salt and adjusting the pH value. The target analytes eluted from the solid-phase extraction cartridge were determined by high-performance liquid chromatography. Some experimental parameters, including the pH value of sample solution, amount of NaCl, ionic liquid type, extraction time, flow rate of carrier gas, flotation time, and solid-phase extraction cartridge type were investigated and optimized. Under the optimized experimental conditions, the limits of detection for metsulfuron, pyrazosulfuron, chlorimuron-ethyl, and nicosulfuron were 1.3, 0.6, 0.7, and 1.1 µg/L, respectively. When the present method was applied to the analysis of milk samples the recoveries of the analytes ranged from 84.3 to 105.2% and relative standard deviations were >5.7%.

Determination of triazine herbicides in vegetables by ionic liquid foam floatation solid phase extraction high performance liquid chromatography.

The ionic liquid foam floatation solid phase extraction was established and applied to the extraction of six triazine herbicides, including desmetryn, secbumeton, terbumeton, terbuthylazine, dimethametryn and dipropetryn, in vegetable samples. To obtain the optimized experimental parameters, the effects of pH value of sample solution, the type and concentration of ionic liquid, the flow rate of carrier gas, foam floatation time, the type of solid phase extraction cartridge, the type and volume of elution solvent on the recoveries of the analytes were examined. The high performance liquid chromatography was applied to the determination of the analytes. Under the optimized experimental conditions, the linearities for determining the analytes were satisfactory and the limits of detection for desmetryn, secbumeton, terbumeton, terbuthylazine, dimethametryn and dipropetryn were 2.50, 1.75, 2.76, 1.87, 1.36 and 1.44µgkg(-1), respectively. The recoveries of the analytes ranged from 78.64% to 104.37% and the relative standard deviations ranged from 1.44 to 6.45%. The real samples were analyzed and the results were satisfactory.