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Test methods and reagents Instrument nitrite need to use, what needs attention
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Test methods and reagents Instrument nitrite need to use, what needs attention

Source:www.weikeqi-biotech.com   Classification:Industry News Release:2016-05-24 11:33:05   Read:(1287)
Nitrite (preservative, color fixative) for meat products as a coloring agent, the use of meat and red nitrite, nitrite is a preservative, which inhibit the proliferation of microorganisms. 1967 Poli Ge et al found that: When only sodium nitrite, 100 mg / kg in order to Clostridium botulinum bacteria inhibited, and if at the same time with sodium nitrite and heated only 3.5 mg / kg It can be suppressed. Nitrate with 2,4-xylenol or a role in the formation of phenol disulfonic acid yellow compound, nitrate can be formed nitrobenzene nitration of benzene, and the like; after Nitrite can diazo oxidative coupling of color; and Asia nitrate and nitrate can be by oxidation, reduction, converted into each other. These properties can be carried out utilizing a nitrate or nitrite colorimetric assay or by gas chromatography and the like. Now widely used in the determination of trace is diazo coupling (Griess reagent) colorimetric method.
1. After the samples were principle to fat, protein after treatment under weakly acidic conditions nitrite and amino acid diazotization, forming purple dye and N-1-naphthyl ethylenediamine coupling, according to the depth and standard dye colors colorimetric quantification.
2. ① spectrophotometer instrument. ② small mincer.
3. Reagents ① potassium ferrocyanide solution: Weigh 10.6 g of potassium ferrocyanide [K4Fe (CN) 6 · 3H2O], dissolved in water and diluted to 100 mL. ② zinc acetate solution: Weigh 21.9 g zinc acetate [Zn (CH3COO) 2 · 2H2O] was dissolved in a small amount of water, adding 3 mL of glacial acetic acid, diluted with water to 100 mL. ③ saturated borax solution: Weigh 5 g of sodium borate (Na2 B4O7 · 10H2O), was dissolved in 100 mL of hot water, cooling backup. ④ benzene amino acid solution (4 g · L-1): Weigh 0.4 g of the amino acid, dissolved in 100 mL (1 + 4) hydrochloric acid, and stored. ⑤ naphthylethylenediamine hydrochloride solution (2 g · L-1): Weigh 0.2 g of hydrochloric acid naphthylethylenediamine, dissolved in 100 mL of water stored. ⑥ sodium nitrite standard stock solution: Precision Weigh 0.1000 g of sodium nitrite (silica gel drier 24 h), add water to dissolve transferred to 500 mL volumetric flask and dilute to the mark. Per milliliter of solution equivalent to 200? G of sodium nitrite. ⑦ sodium nitrite standard solution: before use, to learn the stock standard solution of sodium nitrite 5.00 mL. Placed 200 mL volumetric flask, diluted with water to the mark. This solution per milliliter is equivalent to 5? G of sodium nitrite.
4. Sample Preparation ① meat (except braised category): learn stirring said mixed sample of 5 g in 50 mL beaker, the addition of a saturated solution of borax 12.5 mL, mix with a glass rod, followed by about 70 ℃ distilled water about 300 mL, 500 mL people wash their volumetric flask, placed in boiling water bath for 15 min, removed, while rotating the one hand dropping 2.5 mL zinc acetate solution to precipitate proteins. Cooled to room temperature, distilled water to volume, shake, place a moment, skim the upper layer of fat, clear liquid with filter paper, the filtrate must be clear, reserved for nitrite and nitrate. ② braised categories: the front part of the procedure and the same meat. Whichever filtrate 60 mL to 100 mL volumetric flask, aluminum hydroxide emulsion to the mark, filtered and the filtrate should be colorless and transparent. ③ fruits and vegetables: samples of tissue masher beating. Weigh the amount of slurry (depending on the nitrate content of the sample may be, such as green beans take 10 g, peach, pineapple take 30 g), placed in 500 mL volumetric flask. Add 200 mL of water, shake, fruit and vegetable extract plus 1.0 mL agents (such as white filtrate suspended solids, can be reduced appropriately). Shaken for 1 h, added 2.5 mol·L -1 sodium hydroxide solution, 40 mL, constant volume with distilled water and immediately filtered. Then take 60 mL filtrate to 100 mL volumetric flask, aluminum hydroxide solution to the mark. Filtered with filter paper, the filtrate should be colorless and transparent.
5. ① Determination of sodium nitrite standard curve drawing: draw precise pipette standard solution of sodium nitrite (5 g / mL?) 0.0,0.2,0.4,0.6,0.8, l. 0,1.5,2.0,2.5,3.0,4.0 and 5.0 mL (each containing 0,1,2,3,4,5,7.5,10,12.5 20 and 25? g of sodium nitrite) were added to a 50 mL volumetric flask. Each plus 2 mL0.4% amino acid solution, shake. Stand for 3 ~ 5 min after the addition of 1 mL0.2% naphthyl ethylene diamino hydrochloride solution and distilled water with a heavy volume to 50 mL, shake and let stand for 15 min at 2cm cuvette with spectroscopic photometer absorbance at 540 nm wavelength. The standard curve.
② Determination of nitrite: After taking 40 mL filtrate in 50 mL volumetric flask, add 2 mL0.4% amino acid solution was allowed to stand for 3 ~ 5 min, added 1 mL0.2% hydrochloric acid two naphthyl amino vinyl solution, and set the volume with distilled water, shake and let stand 15 min. Absorbance is measured from the standard curve to give the corresponding sodium concentration (? G / mL), the sample to calculate the content of nitrite (sodium nitrite basis).
6. Calculation ① X = A / {m * [40 / (500 * 50)]} where:? X-- nitrite content of meat products ,, g · g -1; A-- measured absorbance in the standard ? on the curve corresponding to the concentration of sodium nitrite, g · mL -1; m-- sample mass, g.
② X = A / {m * (60/500} * [40 / (500 * 50)]} where: X-- class braised octopus and fruits and vegetables in salt content, g · g-1A-- measured? suction first degree obtained on a standard curve the corresponding concentration of sodium nitrite are multiple, g · mL-1;? m-- sample mass, g.
Determination of nitrate Abstract: make cadmium nitrate solution through the column, the reduction of nitrate to nitrite and nitrate determination by the measurement method. Measured nitrate, cadmium Gui filtrate into the front should be subject to 25 mL (1: 9) with dilute ammonia flow wash buffer, flow rate can be controlled at 3 ~ 5 mL / min (former Simple column cadmium control in 2 ~ 3 mL / min). When the ammonia flow is complete, draw 20 mL sample filtrate was placed in a 50 mL beaker, add 5 friends ammonia buffer solution, after mixing, injection reservoir funnel flowing through cadmium column reduction, the original beaker collect effluent. When the reservoir after the funnel-like flow, followed by 5 mL of water retained in the column replacement of the sample solution. As all collected fluid to cadmium column reduction once again: Battlement secondary effluent was collected in a 100 mL volumetric flask, followed by distilled water cadmium column was washed three times, each time 20 mL. Together with the washing liquid collected in the same volumetric flask with distilled water to the mark. Shake well, remove 10 ~ 40 mL (depending on the filtrate containing nitrite salt may be) in 50 mL volumetric flask; and as before for color measurement, the sample can be obtained after the total content of nitrite reduction, reduction in addition to the original content of nitrite, multiplied by the conversion from nitrate to nitrite factor, you have to play in the nitrate content of the sample.
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