sample analysis
Preparation
1. Place potassium hydrogen phthalate into a weighing bottle, dry in a 105 ℃ oven for 4 hours, cool and store in a dryer;
2. Prepare 0.05 mol/L NaOH.

Calibration of NaOH concentration
1. Blank determination: Measure 100 mL of ultrapure water, use MET U mode to start titration, and conduct parallel testing twice;
2. NaOH calibration: Weigh the dried and cooled potassium hydrogen phthalate, add 100 mL of ultrapure water, dissolve it, and use DET U mode to start titration. Conduct parallel testing three times.

Electrode calibration
Use Metrohm pH 7.0, 4.0, and 9.0 buffer solutions to calibrate the 262 pH aqueous electrode.

Determination of Sodium Glutamate Content
1. Blank determination: Add 85 mL of ultrapure water to a beaker, use SET pH mode to titrate with NaOH to pH=8.2, add 10 mL of formaldehyde solution, continue titration to pH=9.6, and conduct parallel testing three times;
2. Sample testing: Accurately weigh the chicken essence and monosodium glutamate samples, dissolve them separately, and make up to a volume of 250 milliliters in a volumetric flask. Take 25 mL of each test into a beaker, add 85 mL of ultrapure water, and use SET pH mode to titrate with NaOH until pH=8.2. Then add 10 mL of formaldehyde solution and continue titrating until pH=9.6. Conduct parallel testing three times.

Results and discussion
1. Due to the large blank value of formaldehyde, it has a significant impact on the measured value of the sample. Using a pipette to extract 10mL of formaldehyde greatly improves the precision; two If approximately 2 grams of the sample is weighed and dissolved in 100 mL according to customer requirements, 10 mL is taken for each test. However, it was found that the chicken essence sample solution is viscous and prone to sticking to the wall when taken with a pipette. Therefore, 2 grams are weighed and dissolved in 250 mL, and 25 mL is taken with a pipette for each test, effectively improving precision.