To establish a method for the determination of 7 kinds of organic solvent residues in tea polyphenols by headspace-gas chromatography (HS-GC), and conduct risk analysis.

A method for simultaneous determination of 7 kinds of organic solvent residues (n-hexane, methanol, dichloromethane, acetone,ethanol, trichloromethane and ethyl acetate) in tea polyphenols was established using a 50% N,N-dimethylacetamide solution as the matrix, separated by a DB-23 capillary column (60 m×0.32 mm, 0.25 μm), and detected by a flame ionization detector (FID).

HS-GC could effectively separate 7 kinds of solvents to be tested, with good intra day and inter day precision. The standard curve showed a good linear relationship within the concentration range under investigation, with limit of detection of 0.03–1.71 μg/g and limit of quantitation of 0.12–5.77 μg/g. At the same time, residue testing and risk analysis were conducted on 27 batches of tea polyphenol samples in the market.According to the regulations of Chinese Pharmacopoeia, methanol, ethyl acetate, n-hexane and ethanol were detected in some tea polyphenol samples. Among them, 33.33% of the samples had n-hexane and 14.81% of the samples had ethanol exceeding the standard. However, through the analysis of permissible daily exposure (PDE), the health risks caused by n-hexane and ethanol were relatively low.

This research method is simple, accurate, and suitable for the determination of 7 kinds of residual organic solvents in tea polyphenols.

To establish a method for detecting DNA in highly pigmented food samples by membrane-based improved cetyltrimethylammonium bromide (CTAB) combined with real-time fluorescence polymerase chain reaction (PCR).

Black sesame, tea seed meal and rapeseed meal were selected as samples. The optimized protocol employed 0.7 μm glass fiber membrane with 70% ethanol as the rinsing solution and 3 rounds of tris(hydroxymethyl)aminomethane ethylenediaminetetraacetic acid (TE) buffer elution. Pigment removal was achieved through membrane-specific adsorption and selective permeability. The extraction efficiency of the modified CTAB method was compared with that of the traditional CTAB method, and DNA purity and amplification efficiency were evaluated via real-time fluorescence PCR targeting endogenous genes.

The modified method demonstrated significantly superior DNA decolorization effects compared to the traditional CTAB method.Endogenous genes were successfully detected in all 3 kinds of samples, with DNA mass concentrations exceeding 100 ng/μL and cycle threshold (Ct) values ranging between 20 and 25. In contrast, the traditional CTAB method failed to achieve real-time fluorescence PCR amplification due to pigment residue.

The membrane-optimized CTAB method simplifies purification steps, enhances decolorization efficiency, and significantly improves the extraction and detection success rate of DNA from highly pigmented foods. This approach provides a reliable and efficient technical solution for food safety testing.

To investigate process factors affecting the stability of rapid testing methods for mycotoxins in Triticum aestivum L. and Zea mays L..

To used Triticum aestivum L. and Zea mays L. as primary grain samples, a systematic evaluation was conducted on: Screening rates (99%, 97%, 95%, 93%, 91%)mixing methods (manual, mechanical single/double mixing), sample sizes (300, 400, 500, 600, 700 g), and 3 kinds of commercially available rapid testers (SinoTech, FlyingTest, Charm) on detection results for aflatoxin B₁, zearalenone and deoxynivalenol.

Toxin detection levels in raw grain correlated positively with sieving rate, reached a maximum of 667.61 μg/kg. However, variation among the 3 kinds of toxins differed significantly, likely due to their distinct distribution characteristics. Mechanical bidirectional mixed ensured thorough toxin dispersion, reduced detection error to 8.1%. Increasing sample mass enhanced result stability but complicated mixing procedures. Furthermore, all 3 kinds of rapid testing instruments (SinoTech, FlyingTest and Charm) exhibited measurement errors during toxin detection,potentially attributable to operational procedures and system calibration.

Optimising sample handling protocols effectively enhances the accuracy of rapid mycotoxin detection in grain, providing a theoretical basis for ensuring food safety and testing efficiency.

To explore the performance differences of various maize seed tissues in genome extraction and nucleic acid testing to clarify the optimal choice and its impact on clustered regularly interspaced short palindromic repeats/associated protein 12a (CRISPR/Cas12a)-based detection system.

In this study, the genome extraction efficiencies of maize seed embryo, endosperm and whole kernel were compared. Through the conventional polymerase chain reaction (PCR) cascade CRISPR/Cas12a system, the extracted products from each part were amplified and identified, and the impact of the extracted genome on subsequent nucleic acid detection was evaluated. By comparing the DNA extraction efficiency, amplification effect and fluorescence signal intensity, the adaptability of samples from various parts in the test was verified.

There were differences in the efficiency of DNA extraction from different tissues of corn seeds. The genome concentration in the embryo was the highest,followed by the whole kernel, and the endosperm was relatively low, which was in line with the biological structural characteristics of corn seeds. The genomes in each part could be successfully amplified, and the cascade CRISPR/Cas12a system produced a clear positive signal. The qualitative detection limit of the method constructed in this study was 0.1 wt%, which met the detection requirements of genetically modified ingredients in most countries and regions.

Differences in extraction efficiency are found among maize seed tissues, but all parts supports effective nucleic acid amplification and CRISPR/Cas12a detection. In practical applications, tissue separation is not required; efficient and specific detection can be achieved using whole seeds or randomly selected samples. The method developed in this study does not require large-scale instrumentation and is suitable for on-site detection of genetically modified maize seeds, demonstrating potential for application in the safety screening of genetically modified food.

To establish a method for the rapid determination of malathion drug residues in Lonicera japonica by colloidal gold immunochromatography.

The residual malathion in honeysuckle can bind to the colloidal gold-labeled monoclonal antibody, inhibiting the binding of the antibody to the antigen on the nitrocellulose membrane (T line) and resulting in a color change on the T line, this study analyzed the effects of various factors, such as pH, antibody addition amount, antigen coating amount, type of freeze-drying protective agent, and Tween 20 addition amount on the test results.

The optimal conditions determined were as follows: The optimal pH for preparing the malathion monoclonal antibody (mAb) and goat anti-mouse immunoglobulin (lgG) gold-labeled antibody was 9.0; the optimal amount of Tween 20 added was 50 μL; and the optimal lyophilization protectant for the gold-labeled antibody was a mixture of 1.0 g sucrose, 0.5 g bovine serum albumin and 0.5 g mannitol. The optimized method achieved a limit of detection was 50 μg/kg for malathion in Lonicera japonica. Furthermore, the method exhibited high specificity for malathion; no cross-reactivity was observed with isocarbophos, profenofos, phoxim or fenthion at concentrations ranging from 200 to 1000 μg/kg.Method validation using negative and positive samples showed a false-positive rate of 1% and a false-negative rate of 0.5%, achieving consistency with the results from existing standard methods. The test strips produced based on this method could be stored for one year at room temperature under sealed and dry conditions.

The method established in this study is simple to operate, highly specific, sensitive and accurate. It requires a short detection time and demonstrates good stability, making it suitable for the rapid screening of malathion residues in large batches of Lonicera japonica samples.

To establish a method for the rapid determination of the content of 9 kinds of aconitum alkaloids in homemade Radix aconiti Kusnezoffii medicinal wine by ultra performance liquid chromatography-tandem mass spectrometry.

The wild Radix aconiti Kusnezoffii in Yunnan was used as the main raw material. It was made into 5 kinds of different shapes (whole, peeled, flake, block, powder), and 250 g was soaked in 900 mL of 52-degree corn to brew liquor, and the soaking time was about 1.5 years. Took 1 mL sample of medicinal liquor, added 30% methanol water solution (3:7, V:V) to 100 mL, and filtered it with 0.22 μm filter membrane, ready for testing. C₁₈ column and mobile phase of acetonitrile-0.1% formic acid water were used for gradient elution separation, multi-reaction monitoring mode detection, and quantification was carried out by matrix working curve external standard method.

The linear relationship of 9 kinds of aconitum alkaloids was good in the range of 1–100 μg/L, the correlation coefficients were all greater than 0.999, the limits of detection were 0.63–0.98 μg/L, the limit of quantitation were 2.11–3.26 μg/L, and the recovery rates were 81.14%–116.01% at low,medium and high concentrations, the relative standard deviations were 0.97%–11.26% (n=6). According to the analysis of actual samples, the content of diester alkaloids of 9 kinds of aconitum alkaloids in medicinal liquor was high, among which aconitine had the most content and strong toxicity.

This method is simple in pretreatment, high in sensitivity, good in accuracy and high in detection efficiency. It is suitable for rapid screening of 9 kinds of aconitum alkaloids in Radix aconiti Kusnezoffii homemade medicinal liquor in health emergency poisoning events, and provides strong technical support for rapid diagnosis of medical treatment and corresponding emergency treatment measures.