Food – Changior Instrument

Determination of 3-Methanethiol in Sesame-Flavor Liquor

changior — Sat, 26 Mar 2022 02:26:13 +0000

3-methylthiopropyl alcohol, also known as pineapple alcohol, has a strong onion taste, dilution will appear soy sauce smell, mainly used for sauce seasoning, belongs to the edible spices allowed to use by the state. 3-methylthiopropyl alcohol was identified as the characteristic flavor substance of sesame-flavor liquor, and the appropriate detection method of 3-methylthiopropyl alcohol was very important to improve the quality of sesame-flavor liquor.

According to the national standard requirements of GB/T 20824-2007 sesame flavor liquor, the content of 3-methanethiol should be detected. In this experiment, the instrument we used was GC7900 gas chromatograph with flame photometric detector. All the gas path of the instrument is fully EPC control, all operations can be operated on the computer, simple operation, multi-point correction, correlation coefficient of 0.999 or more, in line with the national standard requirements.

1. Detection components:

3-methylthiol propyl alcohol

2.instrument configuration:

Gas chromatograph: Flame photometric detector
Chromatographic column: HT-930 30m*0.32mm*0.5μm
Standard liquid: 3-methylthiyl propyl alcohol standard liquid
Carrier gas cylinder gas: nitrogen, hydrogen, air

3. Experimental conditions

Detector: 220℃
Injector: 200℃
Column temperature: 100℃ (2min) 10℃/min to 180℃ (10min)

4. Configuration scheme

Testing protocol for aflatoxin in food

changior — Sat, 26 Mar 2022 01:56:13 +0000

Recently on the network hot topic “earth pit sauerkraut” make the uproar, people can see the processing and production links can be so people sigh, and those who can not be naked eye identification of food safety hazards and how to identify it?

【 Aflatoxin 】

Aflatoxin (AFT) is a class of compounds with similar chemical structure, which are derivatives of dihydrofuran coumarin. Aflatoxins are secondary metabolites mainly produced by Aspergillus flavus and A. parasiticus, including B1, B2, G1, G2 and two other metabolites M1 and M2, among which M1 and M2 are isolated from milk. B1 is the most toxic and carcinogenic substance. The incidence of aflatoxin in food and feed is highest in hot and humid areas. They exist in soil, plants and animals, all kinds of nuts, especially easy to pollute peanut, corn, rice, soybean, wheat and other grain and oil products, mycotoxin is the most toxic mycotoxin, the harm to human health is very prominent.

[Preparation of sample solution]

The sample is ground to a fine size (less than 2mm) and accurately weighed 25g in a 250 mL corkscrew conical flask (vegetable oil: Weigh 10g, dissolve with n-hexane, and then dissolve with methanol water for extraction), add 5g sodium chloride and methanol-water (7+3) to 100mL, stir with homogenizer at high speed for 2min, centrifugal for 5min (speed 6000r/min). 15mL of supernatant was accurately removed, and the filtrate was placed in a 50ml measuring flask, diluted to scale with water, shaken well, filtered with microporous membrane (0.45um), and 20ml of filtrate was measured. The filtrate was eluted with 20ml of water through the immunoaffinity column at a flow rate of 3ml/min. The eluent was discarded to allow air to enter the column, and the water was extruded out of the column, and eluted with appropriate amount of methanol. Collect all the eluent, place it in a 2ml flask, dilute it to scale with methanol, shake well, and serve.

[Chromatographic conditions]

Chromatographic conditions of iodine derivative method:
Detector: fluorescence detector
Iodine derived mobile phase: methanol – acetonitrile – water
Flow rate: 1.0 mL/min
Column temperature 35 ℃
Injection volume: 20uL

Chromatographic conditions of photochemical derivation:

Detector: fluorescence detector
Photochemical derivatization: 254nm uv light derivatization
Mobile phase :(methanol – acetonitrile) – water
Flow rate: 1.0 mL/min
Column temperature 35 ℃
Injection volume: 20uL

How to detect vitamin C content in fruit juice by HPLC

changior — Mon, 21 Mar 2022 03:00:37 +0000

Vitamin C, also known as ascorbic acid, is water-soluble vitamin, not only can beauty, but also anti-oxidation, cell protection, and even effective anti-cancer, is the most famous nutrient. In this paper, high performance liquid chromatograph was used to detect the content of vitamin C in fruit juice. The analysis results were rapid and accurate. Vitamin C in fruit juice can be separated on ODS column, and vitamin C can be absorbed at the wavelength of 206nm.

1. Determination of vitamin C content in fruit juice by HPLC

1.1 High performance liquid chromatography: unit pump, variable wavelength UV detector, data analysis system.
1.2 Chromatographic column: 150mm×4.6mm, 5µL particles bonded ODS column.
1.3 Injector: 25µL microinjection needle.

2. Analysis conditions of vitamin C content in fruit juice by HPLC

2.1 Mobile phase: 0.01mol/L HCl solution.
2.2 Flow rate: 1.0ml /min.
2.3 Column temperature: 40.
2.4 Detection wavelength: 206nm.
2.5 Retention time: 3.2min.

3.Determination steps of vitamin C content in fruit juice by HPLC

3.1 Sample preparation: 4.0g of concentrated juice sample was weighed, accurate to 0.01g, dissolved in 50mL volumetric bottle with mobile phase, and the volume was fixed to scale, shaken well, and the sample was filtered into the sample bottle with 0.45µm water filter membrane as sample solution.
3.2 Under the above operating conditions, wait for the stable operation of the testing instrument, and cross test according to the sequence of standard solution and sample solution.