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Detection of Cr(VI) in toys by IC-ICPMS

2022-03-03 08:001391

Latent crisis in toys 

Chromium is a multivalent metal, the most common of which are Cr (III) and Cr (VI). Among them, the toxicity of Cr (VI) is more than 100 times of that of Cr (III), which has a very large toxic effect on human beings, animals and aquatic organisms. It is listed as a class I carcinogen by the international agency for cancer research (IARC). But many people don't know that there is a crisis of excessive Cr (VI) in children's toys!

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Cr (VI) is very easy to be absorbed by human body. It can invade human body through digestion, respiratory tract, skin and mucous membrane. It has been reported that when people breathe air containing different concentrations of  Cr (VI), they will have varying degrees of hoarseness, atrophy of nasal mucosa, and even perforation of nasal septum and bronchiectasis. It can cause vomiting and abdominal pain. Dermatitis and eczema can occur through skin invasion. The most harmful is long-term or short-term exposure or inhalation of carcinogenic risk.

In April 2019, the European Committee for Standardization(CEN)issued the toy safety standard EN71 Part 3: migration of specific elements (2019 version). Among them, the revised content for Cr(VI)detection is:

● the limit value of Cr (VI) of the third kind of material, changed from 0.2mg/kg to 0.053mg/kg, effective on November 18, 2019.

● the test method of Cr (VI) has been revised, and the revised method can already contain the limit of all categories of materials. Test method changed from LC-ICPMS to IC-ICPMS.


SHINE professional solutions

According to EN71-3:2019 standard of European Union, the separation and detection of Cr (III) and Cr (VI) in toys can be realized by using SINE CIC-D120 ion chromatograph and NCS plasma MS 300 inductively coupled plasma mass spectrometer. The detection time is within 120 seconds, and the linear relationship is good. Under the condition of injection of Cr (III) and Cr (VI), the detection limits are 5ng / L and 6ng / L respectively, and the sensitivity meets the standard detection limit requirements.


1. Instrument configuration

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SHINE CIC-D120 ion chromatograph + NCS plasma MS300 ICP-MS


2.Detection conditions

Ion chromatograph condition

Mobile phase: 70 mM NH4NO3, 0.6 mM EDTA(2Na), pH 71  ,  Elution mode: Isometric elution

Flow rate (mL / min): 1.0

Injection volume (µL):200

Column: AG 7


ICP-MS condition

RF power (W) :1380

Carrier gas (L/min) :0.97

Analysis mass number:52C  

Multiplier voltage (V) :2860  

Duration (s) :150

 

3 .Reagents and standard solutions

  • Cr (III) and Cr (VI) standard solution: commercially available certified standard solution

  • Concentrated ammonia: superior pure

  • Concentrated nitric acid: superior purity

  • EDTA-2Na: superior purity

  • Ultra pure water: resistivity ≥ 18.25 m Ω· cm (25 ℃).

  • Preparation of Cr(VI) working curve: dilute Cr(VI) standard solution with ultra pure water to the required concentration step by step.

  • Preparation of Cr (III) and Cr (VI) mixed solution working curve: take a certain amount of Cr (III) and Cr (VI) standard solution, add 10mL of 40mM EDTA-2Na into a 50mL volumetric flask, adjust the pH value to about 7.1, heat it in a water bath at 70 ℃ for 15min, fix the volume, and make the standard mixed solution with the required concentration by the same method.


4.Detection result

In accordance with the recommended experimental method of EN71-3, Cr (III) was complexed with  EDTA-2Na, and Cr(III) and Cr(VI) were effectively separated. The chromatogram of the sample after three repetitions showed that the reproducibility was good, and the relative standard deviation (RSD) of peak area was less than 3%.The detection limit was determined by the concentration of S/N>3. The detection limit was 6ng/L.

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Injection separation chromatogram of Cr (III) - EDTA and Cr(VI) mixed solution

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Chromatogram overlay of three injection tests of 0.1ug/L Cr (III)-EDTA and Cr(VI) mixed solution(Stability of 0.1ppbCr (III) + Cr (VI) sample)

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0.005-1.000 ug/L Cr (III) calibration curve(Peak area linearity)

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0.005-1.000 ug/L Cr (VI) calibration curve(Peak height linearity)


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