UV-1100 spectrophotometric sodium benzoate detection - Database & Sql Blog Articles

Determination of sodium benzoate by spectrophotometry

Spectrophotometric method for the detection of sodium benzoate. Key words: spectrophotometry; food additive; analysis instrument ; UV-1300 I. Introduction of sodium benzoate: sodium benzoate (chemical formula: C6H5CO2Na), is benzoic acid Sodium salt. Sodium benzoate is a very common food preservative. It has the effect of preventing deterioration and acidity and prolonging the shelf life. It is widely used in countries all over the world. However, concerns about its toxicity in recent years have limited its application, and some countries such as Japan have stopped producing sodium benzoate and restricted its use. Sodium benzoate is mostly white granules, odorless or micro-belt benzoin smell, slightly sweet, astringent; soluble in water (normal temperature) 53.0g/100ml, PH is around 8; sodium benzoate is also an acidic preservative, in alkali There is no bactericidal or bacteriostatic effect in the medium; the best pH for anti-corrosion is 2.5-4.0, and the bactericidal effect of 5% solution at pH 5.0 is not very good. Sodium benzoate is more lipophilic, easily penetrates into the cell membrane, interferes with the permeability of the cell membrane, inhibits the absorption of amino acids by the cell membrane, enters the alkali storage in the ionized acidified cells of the cell, and inhibits the activity of the respiratory enzyme of the cell. The acetyl-CoA condensation reaction is prevented, thereby serving the purpose of food preservation. Melting point: 300 ° C. Boiling point: 249.3 ° C at 760 mmHg Molecular weight: 144 Properties: white particles or crystalline powder. Odorless, sweet and astringent. Uses: 1 Mainly used as food preservatives, also used in the manufacture of drugs, dyes, etc. 2 For pharmaceutical industry and plant genetic research, also used as dye intermediates, fungicides and preservatives. 3 preservatives; antimicrobial agents. 4 Sodium benzoate liquid chamber is an important acid type preservative. Converted to an effective form of benzoic acid when used. See benzoic acid for the range of use and amount of use. In addition, it can also be used as a preservative for food. 5 sodium benzoate is also an important acid type food preservative. Converted to an effective form of benzoic acid when used. See benzoic acid for the range of use and amount of use. In addition, it can also be used as a preservative for feed. 6 This product is used as a food additive (preservative), a fungicide for the pharmaceutical industry, a mordant for the dye industry, a plasticizer for the plastics industry, and an intermediate for organic synthesis such as perfumes. 7 used as a cosolvent for serum bilirubin test, food additive (preservative), bactericide for the pharmaceutical industry, mordant for the dye industry, plasticizer for the plastics industry, and also as an intermediate for organic synthesis such as perfume. 2. Determination of sodium benzoate Determination of sodium benzoate by acid-base titration This experiment uses biphasic titration to determine the content of sodium benzoate in carbonated beverages. In this experiment, UV-visible spectrophotometry was used to determine the content of sodium benzoate in carbonated beverages. The results were compared with biphasic titration. The determination of sodium benzoate can be titrated with HCl, but the solubility of benzoic acid formed at room temperature is very small. Almost insoluble in water, resulting in a pH spike at the end of the titration is not obvious enough, and the free benzoic acid attached to the container and liquid surface will affect the observation of the titration results, and to some extent adsorb a small amount of indicator, which is not conducive to the end point judgment . Benzoic acid is hardly soluble in water (0.34g/100ml) at room temperature, slightly volatile in air, hygroscopic, soluble in hot water, and soluble in organic solvents such as ethanol and chloroform. Sodium benzoate is readily soluble in water at room temperature (53.0 g / 100 ml, pH ≈ 8). Considered comprehensively, in this experiment, the free benzoic acid in the aqueous phase is absorbed, the benzoic acid is extracted into the ethanol solution, and then the carbonated beverage sample is titrated with the 0.01 mol/L standard NaOH solution in the ethanol solution using PP as an indicator. To the pink color, the content of sodium benzoate in the carbonated beverage is calculated according to the volume of the NaOH standard solution consumed by the titration. 1 Note: Some of the relevant contents are listed below. [Experimental instrument]: 50ml acid burette, 50ml basic burette, 250ml conical flask × 3,500ml separatory funnel, 1000ml beaker, 250ml volumetric flask × n, 25ml pipette, 10ml graduated cylinder, 100ml graduated cylinder, glass rod, Surface dish, bottle with rubber stopper × 2, 50ml with stopper cylinder × 2, 2ml pipette, 10ml pipette. Electronic analytical balance (0.0001g), UV-visible spectrophotometer UV-1300, electric thermostatic water bath (room temperature +5 ° C ~ 99 ° C). [Experimental reagent]: HCl solution (1+1), 40% NaOH solution, oxalic acid/hydrogen potassium phthalate reference reagent, benzoic acid reference reagent, PP, anhydrous sodium sulfate (analytical grade), (analytical grade), NaCl (analytical grade), ethanol (analytical grade). One bottle of Sprite carbonated drink (reserved sample: one bottle of merida carbonated drink). [Experimental content]: (1) Experimental preparation: 1. Prepare deionized water to remove CO2: Add 800 ml of deionized water to a 1000 ml beaker and heat to boiling, boil for 3 to 5 minutes, and cool to room temperature for use. Note that during the heating process, the surface dish is capped before the deionized water is boiled to reduce the heat loss and shorten the heating time. The water droplets condensed on the outside of the beaker at the beginning of the heating should be wiped off with the filter paper in time to avoid the heat uneven beaker bursting. When heating to near boiling, be careful to prevent bumping. Gently stir the glass rod from the tip of the beaker. 2. Prepare a 4% NaCl solution: Add 4.0 g of NaCl solids in 100 ml of deionized water, dissolve and shake. 3. Prepare HCl solution (1+1): Mix 25 ml of concentrated hydrochloric acid and 25 ml of deionized water in a ratio of 1:1 by volume and shake well. (2) Preparation and calibration of sodium hydroxide standard solution 1. Configure NaOH standard solution: Measure 2.5ml saturated sodium hydroxide solution (20mol/L) in a 10ml measuring cylinder, dilute with 500ml water, and place in rubber stopper bottle Shake well by shaking, use a 25 ml pipette to measure the above solution in a 250 ml volumetric flask, dilute to the mark with water, shake well, and transfer to a fine-mouthed bottle with a rubber stopper for use. 1. Configure potassium hydrogen phthalate standard solution: accurately weigh 0.20±0.01g of potassium hydrogen phthalate reference reagent in a 100ml beaker, add about 30ml of the above deionized water to remove CO2, and transfer to 100ml capacity. In the bottle, wash 3 times, transfer the washing liquid into the volumetric flask, shake the volumetric flask gently when it is close to two-thirds, and continue to add 100 ml of deionized water with CO2. 2. Calibration NaOH standard solution: use 2 ml of 25.00 ml of potassium hydrogen phthalate standard solution in a 250 ml Erlenmeyer flask, respectively, using a 25 ml pipette, and titrate to pale pink (PP discoloration) using the above-prepared NaOH standard solution. Point PH = 9.0), recording the volume of the sodium hydroxide standard solution consumed. Calculate the concentration of the NaOH standard solution corresponding to each reagent, and use the average value as the concentration of the NaOH standard solution. (III) Pretreatment and sample preparation of carbonated beverage samples 1. CO2 in carbonated beverages: 200g of carbonated beverage samples were accurately weighed in a 500ml beaker, heated to boiling, boiled for 5-8 minutes, and cooled for use as a crude sample. 2. Sample preparation for analysis: 80 g of NaCl was added to the crude sample prepared above, stirred until no longer dissolved, 40 ml of HCL (1+1) was added, stirred, decanted into a 500 ml separatory funnel, and the inner wall of the beaker was washed with mother liquor and insoluble. The material was poured 3 times and the washing liquid was decanted back into the separatory funnel. Add 30ml and 20ml respectively and extract once, shake well, let stand, discard the waste liquid and combine the ether layer, wash the ether layer 3 times with 4% sodium chloride aqueous solution, let stand for more than 15min each time, discard the water layer, add 15g Anhydrous sodium sulfate, shaken, filtered into a 100ml beaker, evaporated to dryness in a 40 ° C water bath, add 20 ml of ethanol to dissolve the residue, transfer 50 ml of deionized water to remove CO2 into a 250 ml Erlenmeyer flask, add 2 to 3 drops of PP indication Agent. (IV) Titration analysis of sodium benzoate in the sample 1. Using the above prepared NaOH standard solution, the sample was titrated to pale pink (PP discoloration point PH=9.0) with PP as an indicator, and the volume of the NaOH standard solution was recorded. 2. Repeat the above operation to obtain 3 sets of data, calculate the sodium benzoate content corresponding to each set of data, and use the average value as the final result of sodium benzoate content. (V) Results Calculation UV spectrophotometric determination of sodium benzoate UV-13001 reagent and instrument sodium benzoate standard solution: 0.0052mg / ml, hydrochloric acid (1:1); (AR), saturated NaCl solution, the above reagents are analytically pure, water For heavy distillation of water. UV-1300 UV spectrophotometer. 2 Experimental method Take a certain amount of experimental solution in a separatory funnel, add 20ml of saturated NaCl solution, then add 10ml of hydrochloric acid (1:1) and 25ml, shake well for 5min, then let go to leave the inorganic phase, take the reagent blank as a reference Measure the absorbance. The experimental result is the content of benzoic acid, multiplied by the corresponding molecular weight ratio to obtain the content of sodium benzoate. (The minimum detection limit of sodium benzoate is Cdl=0.0014g/L) The standard curve is drawn: take another 0.0052mg/ml sodium benzoate standard solution 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0ml in 125ml separatory funnel In the experiment, the absorbance was measured at 223 nm and the AC curve was drawn. Sample determination: take 5-10ml of a fruit juice beverage sample, and measure the sodium benzoate content in the orange juice beverage according to the standard curve operation. Key words: spectrophotometry; food additive; aesthetic instrument ; UV-1300