This article mainly introduces how to use ion chromatography to detect borate in cosmetics
Boric acid is used as a preservative in cosmetics and also as a pH adjuster to increase product viscosity and stabilize formulations. External use of boric acid is generally not very toxic, but its oral toxicity is strong. It can be quickly absorbed from the gastrointestinal tract and damaged skin. The lethal dose is 15-20g for adults and 3-6g for children. Boric acid and borate are slowly excreted in the human body, and long-term intake can cause accumulation and cause chronic poisoning.
1 Ion chromatography experiment
Ion Chromatograph: IC6600
Chromatography pump: P6600
Detector: DC6600, equipped with conductivity detector
|Column||Chromatographic column for borate 9x250mm|
|Mobile phase||3 mmol/L methanesulfonic acid+60 mmol/L mannitol|
|Regenerated liquid||25mmol/L Tetramethylammonium Hydroxide+15mmol/L Mannitol|
|Mobile phase flow rate||1.0mL/min||Regenerated liquid flow rate||1.0mL/min|
|Column temperature||30℃||Conductivity cell temperature||35℃|
▶ Determination of soluble borate
(1) Weigh 1.0 g of sample (accurate to 0.0001 g) into a 10 mL plastic colorimetric tube with stopper,
(2) Add 7 mL methanol solution and vortex for 1 min,
(3) Dilute the volume to 10 mL with methanol solution, shake well, and centrifuge at 10000 rpm for 5 min.
(4) Take 1 mL of the supernatant, put it in a 10 mL plastic volumetric flask, dilute to the mark with water, shake well,
(5) Pass the RP column, discard the first 3 mL effluent, and collect the subsequent effluent as the solution to be tested.
▶ Total boric acid and borate
(1) Weigh 1.0 g of the sample (accurate to 0.0001 g) in a 30 mL porcelain evaporating dish,
(2) Add 10 mL of sodium carbonate solution (3.9) and evaporate to dryness on a water bath.
(3) Transfer to the electric furnace for carbonization,
(4) Move into a high-temperature furnace and ash at 500 ℃ for 5 hours,
(5) After cooling, add 20 mL of hydrochloric acid solution to the ash to dissolve,
(6) Transfer to a 100 mL plastic volumetric flask, dilute to the mark with water, shake well,
(7) Pass through the Ag column and H column in sequence, discard the first 3 mL effluent, and collect the subsequent effluent as the solution to be tested.
4 Standard curve test
|Standard curve series concentration gradient table（mg/L)|
5 Sample test
Note: There is no borate interference in the sample blank.
|Name||Number||Weighing amount (g)||Constant volume (mL)||Dilution times||Determine the concentration (mg/L)||content(%)||Average content (%)|
|Boric acid||Sample 1-Parallel Sample 1||1.0248||10||10||40.556||0.396||0.402|
|Sample 1-Parallel Sample 2||1.0392||42.443||0.408|
Note: The absolute difference of the parallel determination results of the parallel samples does not exceed 10% deviation of the arithmetic mean, which meets the standard requirements.
6,Sample addition test
|Name||Number||Weighing amount (g)||Constant volume (mL)||Dilution times||Standard addition (mg)||Concentration after standard addition (mg/L)||Recovery rate(%)|
|Boric acid||Sample 1-Parallel Sample 1||10||10||4.0||80.248||96.9|
|Sample 1-Parallel Sample 2||80.62||97.5|
Note: The recovery rates of standard addition in this test are 96.9% and 97.5%, which meet the standard requirements.
Using ion chromatography to detect borate in cosmetics, the pre-treatment is simple, and the target peak is peaked within ten minutes without other interference.