Name: Trimethylamine Detection in Animal-Derived Medicine by Headspace GC-MS
Uploaded: 2023-03-10T13:30:00
Description: Watch this Scientific Journal Video about Trimethylamine Detection in Animal-Derived Medicine by Headspace GC-MS at JoVE.com

The video outlines a laboratory procedure for extracting and measuring trimethylamine levels in medicinal materials: Pheretima, Periplaneta americana, and Hirudo. It details grinding, homogenization, centrifugation, and gas chromatography-mass spectrometry (GCMS) techniques used to assess recovery rates and trimethylamine concentration in the samples.

trimethylamine detection in animal-derived medicine by headspace gc-ms

Trimethylamine Detection in Animal-Derived Medicine by Headspace GC-MS

Treating human diseases by utilizing products derived from animal parts and/or their by-products (referred to here as animal-derived medicines) is receiving increased attention. They play an important role in treating cancer, cardiovascular disease, liver cirrhosis, mastitis, and other diseases, with the advantages of a strong effect, small dosage, and significant and specific clinical efficacy. However, animal-derived medicines generally have a prominent fishy odor, which greatly affects patients&#39; compliance, and are especially unfavorable for children1,2. The fishy odor mainly comes from the proteins, amino acids, fats, and other substances contained in the medicine, which are decomposed through fatty acid oxidation, amino acid degradation, and other ways to produce a variety of substances with a fishy odor2,3,4. Among them, trimethylamine (TMA) is a volatile gas with a fishy odor that widely exists in rotting or rotten animal-derived foods5.
Until now, gas chromatography (GC), liquid chromatography (LC), ion chromatography, spectrophotometry, liquid chromatography-mass spectrometry (LC-MS), and sensor methods have commonly been used to detect TMA in the environment, food, and urine6,7,8,9. In view of the low contamination of the GC column and injection system, as well as the high sensitivity, reproducibility, and low detection limit (0.1-1 mg/kg), the headspace gas chromatography-mass spectrometry (HS-GC-MS) method was preferred for food and biological analysis8. At present, only China has established a national standard for TMA in food, and HS-GC-MS is the first method in the GB5009.179-2016 standard10. Therefore, the above HS-GC-MS method was selected to detect TMA in animal-derived medicine. In the early stage, our research group found that the HS-GC-MS detection standard for TMA in food could detect the fishy odor in several animal-derived medicines. Combined with the results of the studies11,12, it could be proved that TMA is the common key substance of fishy odor in animal-derived medicines. However, it was found that the reproducibility of the experimental results was poor, and there were problems such as TMA escape and poor stability, which could not be verified by the methodology. This could be due to the fact that the lye was injected into the headspace vial and the rapid acid-base reaction led to increased pressure in the vial, thus TMA escaped from the injection pore, preventing the stable and accurate detection of TMA. Therefore, this study proposed an improved headspace gas chromatography-tandem quadrupole mass spectrometry (HS-GC-MS/MS) detection method to address these problems.
The protocol improves the sample pretreatment by separating the acid-base reactants in the pretreatment with the help of solid paraffin, a good solid-liquid phase change material. As the paraffin slowly liquefied with the temperature rise of the thermostatic furnace, TMA was also slowly released in the sealed headspace vial, avoiding the pressure increase caused by the violent and rapid acid-base reaction and ensuring stable and accurate TMA detection. Further, the headspace injection combined with multiple reaction monitoring (MRM) modes) in GC-MS/MS effectively suppressed matrix chemical interference and ensured the reliability of the results. The results of the methodological validation proved that the linearity, precision test, and recovery rate of the improved detection method could meet the requirements, with good reproducibility and high sensitivity.

Author Spotlight: An Improved Technique for Trimethylamine Detection in Animal-Derived Medicine by Headspace Gas Chromatography-Tandem Quadrupole Mass Spectrometry  

An Improved Technique for Trimethylamine Detection in Animal-Derived Medicine by Headspace Gas Chromatography-Tandem Quadrupole Mass Spectrometry

The scope of our research is a material basis in the variation of fish odor in animal medicine. This protocol provides a simple pretreatment method and accurate detection of trimethylamine in animal medicines. The simple pretreatment methods and the programmed parameters of HS-GC mass/mass of this protocol, need to be further optimized, and we still have a lot of work to do.Our protocol adopts the multi-direction monitoring mode of GC mass/mass, combined with a unique, simple pretreatment, which is not only the first pretreatment for trimethylamine analysis, but also the first analytical mode to be used.

Watch this Scientific Journal Video about Trimethylamine Detection in Animal-Derived Medicine by Headspace GC-MS at JoVE.com

Trimethylamine Detection in Animal-Derived Medicine by Headspace GC-MS  

To begin, crush the medicinal materials Pheretima, Periplaneta americana, and Hirudo with an herbal grinder. Sift the medicinal powder through standard drug sieves of number two and number four. Collect the powder between the two sieves to obtain the required sample powder.Take one gram of the powder in a 50 milliliter plastic centrifuge tube. Add 20 milliliters of 5%trichloroacetic acid solution and homogenize at 1, 000 RPM for one minute with a high speed dispersion homogenizer. After homogenization, centrifuge the homogenate at 1, 717 G for five minutes at room temperature and filter the supernatant through an absorbent cotton-dipped glass funnel into a 50 milliliter volumetric flask.After repeating the extraction process twice with 15 and 10 milliliters of 5%trichloroacetic acid solution, combine the filtrates and make up the volume to 50 milliliters with 5%trichloroacetic acid solution. Next, accurately add two milliliters of sodium hydroxide solution and 0.5 grams of solid paraffin in 20 milliliter headspace vials. Then place them in an oven at 70 degrees Celsius for about 30 minutes.Take the vials out and let them cool down to room temperature so that the paraffin solidifies. To process the sample headspace, add two milliliters of each sample extraction solution to the solidified paraffin containing vials. Press the cap and seal the vial.Put the sealed headspace vials on the GCMS for measurement. To obtain the standard curve, aspirate a series of two milliliters of trimethylamine standard solution on top of the solidified paraffin layer. Put the sealed headspace vials on the machine for trimethylamine measurement.To perform the precision test, aspirate two milliliters of 0.1 micrograms per milliliter trimethylamine standard solution on top of the solidified paraffin layer. Carry out six parallel tests in the machine following the manufacturer's instructions. For the recovery rate experiment, bake several batches of the sample powder in an oven until no triethylamine is detected in GCMS as demonstrated previously.Next, take each one gram of oven baked and fineable powder into separate 50 milliliter plastic centrifuge tubes. Add 50 microliters of trimethylamine standard solution to all the tubes and extract with 5%trichloroacetic acid solution as demonstrated previously. The retention time of trimethylamine was found to be 2.3 minutes with a sharp peak and no interference from other impurities.Pheretima, Periplaneta americana, and Hirudo samples subjected to spiked recovery tests by drying to reduce triethylamine in the herbs showed average recovery rates of 84.49, 94.66, and 85.67%respectively. Triethylamine was detected in nine batches of herbs with concentrations ranging from 13.23 to 271.63 milligrams per kilogram.

Research

JoVE Journal

Chemistry

Animal-derived medicines have distinctive characteristics and significant curative effects, but most of them have an obvious fishy odor, resulting in the ...