It is well known that heavy metals are found naturally in the environment in rocks, soil and water and therefore exist in the manufacture of pigments and other raw materials in all industries including the cosmetics industry. Some of these metals have been used as cosmetic ingredients in the past. In some cases, measures have been implemented to reduce the amount of heavy metals to which users are exposed, including prohibiting their use in cosmetics. Lead,arsenic, cadmium, mercury, antimony and chromium are the main heavy metal ingredients prohibited in cosmetics in most countries. Cosmetic manufactures have the responsibility to ensure their products do not contain any of these metals.
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It is well known that heavy metals are found naturally in the environment in rocks, soil and water, and therefore exist in the manufacture of pigments and other raw materials in all industries including the cosmetics industry. Some of these metals have been used as cosmetic ingredients in the past. In some cases, measures have been implemented to reduce the amount of heavy metals to which users are exposed, including prohibiting their use in cosmetics. Lead, arsenic, cadmium, mercury, antimony and chromium are the main heavy metal ingredients prohibited in cosmetics in most countries. Cosmetic manufacturers have the responsibility to ensure their products do not contain any of these metals.
Metal determination in samples is often done by ICP or ICPMS and it requires the samples to be in dissolved form. Commonly, acid digestions are the method of choice but seeing as many samples contain an important amount of silica, alumina and magnesium, some aggressive acids, such as HF must be used to obtain full dissolution. Furthermore, the quickest microwave methods can take up to 3 hours.
Knowing the risks associated with the use of HF, many laboratories look for alternative methods for obtaining full dissolution of their samples while optimizing the uptime and productivity.
The proposed methods describe alternative ways to determine the concentration of elements of interest as well as confirm the absence of heavy metals contained in cosmetics using borate fusions and peroxide fusions for ICP-OES determination.
1.1 - Ashing
Due to their high organic and water content, each cosmetic sample and standard was submitted to an ashing procedure.
• Porcelain crucibles
• 550 °C until constant weight
• LOI is calculated for final analysis
1.2 - Borate fusion Method
Claisse® TheOx-DS® 6 position electric Fluxer
• Pt-Au (95 % / 5%) crucibles
• 34.83 / 64.67 / 0,5 (Li2B4O7 / LiBO2 / LiBr) flux
• 10 minutes of heating at 1050 °C
• 4 minutes of dissolution in 10 % HNO3 v / v
1.3 - Peroxide fusion Method
Claisse® TheOx-DS® 6 position electric Fluxer
• zirconium crucibles
• sodium peroxide flux
• 7 minutes of heating at 700 °C
• 4 minutes of cooling
• Dissolution in 20 % HNO3 / HCl v / v
2.1 – PerkinElmer® Optima 7300DV
Plasma flow rate (Ar) | 16.0 L/min |
Auxiliary gas flow rate | 0.4 L/min |
Nebulizer flow rate | 0.8 L/min |
Sample flow rate | 1.0 mL/min |
Rinse | 2.5 mL/min (2 min < 10 ppm;
add. 90 sec for > 10ppm) |
Shear gas pressure | 100 PSI |
RF Power | 1500 W |
Sample | Supplier | LOI (%) |
---|---|---|
DC60132 (Talc CRM) | NCS | 10 |
SDC-1 (Mica CRM) | USGS | 2 |
Sample 1 (647G-08-8008) | Cosmetic Industry | 63 |
Sample 2 (6LX5-11-8001) | Cosmetic Industry | 88 |
Sample 3 (6MPY-01-8001) | Cosmetic Industry | 24 |
Sample 4 (6MNY-18-8001) | Cosmetic Industry | 78 |
Sample 5 (9995-12-2921) | Cosmetic Industry | 55 |
Peroxide Fusion Method | Borate Fusion Method | |||
---|---|---|---|---|
Element | Wavelength
(nm) | Viewing mode | MDL (mg/L) | MDL (mg/L) |
Al | 394.401 | Axial | 0.2 | 0.2 |
Ba | 413.065 | Axial | 0.1
| 0.1 |
Ca | 315.887 | Axial | 3 | 0.1 |
Cd | 214.440 | Axial | 0.003 | 0.002 |
Co | 230.786 | Axial | 0.002 | 0.01 |
Cr | 267.716 | Axial | 0.002 | 0.03 |
Fe | 238.204 | Radial | 0.8 | 0.8
|
K | 766.490 | Axial | 3 | 0.5 |
Mg | 279.077 | Axial | 0.2
| 0.3 |
Mn | 257.610
| Axial | 0.3 | 0.3 |
Mo | 204.597 | Axial | 0.05 | 0.05 |
Na | 589.592 | Axial | ND* | 0.4 |
Ni | 231.604 | Axial | 0.001 | 0.008 |
P | 213.617 | Axial | 0.2
| 0.2 |
Pb | 220.353 | Axial | 0.07
| 0.03 |
Si | 251.611
| Axial | 3 | 3 |
Sr | 460.733 | Axial | 0.04 | 0.005
|
Ti | 334.940 | Radial | 0.5 | 0.5 |
Zn | 206.200 | Radial | 0.3 | 0.3 |
Element | Wavelength (nm) | Average
experimental values (%) n = 10 | Certified
values (%) | Accuracy
(%) | Precision
(%) |
---|---|---|---|---|---|
Al | 394.401 | 7.9 | 8.3622 | 95 | 2 |
Ca | 315.887 | BQL | 1.0006 | (104) | (12) |
Fe | 238.204
| 4.6 | 4.4204 | 105 | 3 |
K | 766.490 | 2.6 | 2.7229 | 96 | 3 |
Mg | 279.077 | 0.99 | 1.0191 | 96 | 1 |
Mn | 257.610 | BQL | 0.0880 | (90) | (1) |
P | 213.617 | BQL | 0.0698 | (92) | (3) |
Si | 251.611 | 34 | 30.7572 | 109 | 2 |
Ti | 334.940 | 0.61 | 0.6055 | 100 | 3 |
Element | Wavelength
(nm) | Average
experimental values (%) n = 10 | Certified
values (%) | Accuracy
(%) | Precision
(%) |
---|---|---|---|---|---|
Al | 394.401 | 4.0 | 4.0329 | 99 | 3 |
Ca | 315.887 | BQL | 1.7081 | (104) | (6) |
Fe | 238.204 | 1.7
| 1.8465 | 94 | 2 |
K | 238.204 | BQL | 0.0108 | - | - |
Mg | 279.077 | 17 | 17.7896 | 96 | 2 |
Mn | 257.610 | BQL | 0.0183 | (82) | (1) |
P | 213.617 | BQL | 0.048 | (110) | (7) |
Si | 251.611
| 25 | 22.3013 | 114 | 1 |
Ti | 334.940 | 0.32 | 0.3117 | 103 | 4 |
Element | Wavelength
(nm) | Sample
1 (%) | Sample
2 (%) | Sample
3 (%) | Sample
4 (%) | Sample
5 (%) | DC60132
(%) | SDC-1
(%) |
---|---|---|---|---|---|---|---|---|
Ba | 413.065 | 108 | 102 | 107 | 106 | 104 | 110 | 87 |
Cd | 214.440 | 108 | 103 | 95 | 97 | 102 | 100 | 98 |
Co | 230.786 | 94 | 91 | 97 | 96 | 98 | 100 | 97 |
Cr | 267.716 | 95 | 110 | 111 | 111 | 114 | 115 | 106 |
Mo | 204.597 | 85 | 105 | 101 | 104 | 107 | 102 | 86 |
Ni | 231.604 | 99 | 86 | 99 | 100 | 102 | 101
| 84 |
Pb | 220.353 | 89 | 86 | 97 | 97 | 100 | 93 | 85 |
Sr | 460.733 | 100 | 96 | 104 | 105 | 112 | 94 | 86 |
Zn | 206.200 | 103 | 101 | 112 | 92 | 110 | 97 | 91 |
Element | Wavelength
(nm) | Average experimental values (%) n = 10 | Certified values (%) | Certified values (%) | Precision
(%) |
---|---|---|---|---|---|
Al | 394.401 | 8.3 | 8.322 | 100 | 2 |
Ca | 315.887 | 1.1 | 1.0006 | 105 | 3 |
Fe | 238.204
| 4.6 | 4.4204 | 103 | 3 |
K | 766.490 | 2.6 | 2.7229 | 94 | 2 |
Mg | 279.077 | 1.0
| 1.0191 | 101 | 2 |
Mn | 257.610 | BQL | 0.088 | (84)
| (2) |
Na | 589.592 | 1.1 | 1.5208 | 75 | 3 |
P | 213.617 | BQL | 0.0698 | (75) | (5) |
Si | 251.611 | 31 | 0.0698 | 101 | 2 |
Ti | 334.940 | 0.6 | 0.6055 | 98 | 3 |
Element | Wavelength
(nm) | Average experimental
values (%) n = 10 | Certified values (%) | Accuracy
(%) | Precision
(%) |
---|---|---|---|---|---|
Al | 394.401 | 4.3
| 4.0329 | 105 | 2 |
Ca | 315.887 | 1.9
| 1.7081 | 114 | 3 |
Fe | 238.204 | 1.8 | 1.8465 | 96 | 3 |
K | 766.490 | BDL
| 0.0108 | - | - |
Mg | 279.077 | 18 | 17.7896 | 103 | 2 |
Mn | 257.610 | BDL | 0.0183 | (76)
| (2) |
Na | 589.592 | BDL | 0.0182 | - | - |
P | 213.617 | BDL | 0.0480 | (92) | (3) |
Si | 251.611 | 24 | 22.3013 | 108 | 2 |
Ti | 334.940 | 0.36 | 0.3117 | 102 | 2 |
Element | Wavelength
(nm) | Sample
1 (%) | Sample
2 (%) | Sample
3 (%) | Sample
4 (%) | Sample
5 (%) | DC60132
(%) | SDC-1
(%) |
---|---|---|---|---|---|---|---|---|
Ba | 413.065 | 99 | 92 | 101 | 102 | 100 | 95 | 99 |
Cd | 214.440 | 87 | 88 | 98 | 87 | 114 | 113 | 87 |
Co | 230.786 | 100 | 105 | 100 | 105 | 101 | 101 | 101 |
Cr | 267.716 | 108 | 111 | 102 | 94 | 111 | 108 | 110 |
Mo | 204.597 | 102 | 106 | 104 | 106 | 104 | 103 | 98 |
Ni | 231.604 | 98 | 104 | 99 | 101 | 104 | 100 | 101 |
Pb | 220.353
| 86 | 87 | 91 | 85 | 93 | 86 | 77 |
Sr | 460.733 | 95 | 98 | 86 | 96
| 87 | 91 | 84 |
Zn | 460.733 | 100 | 94 | 102 | 102 | 108
| 113 | 111 |
The following criteria were taken into consideration in selecting the elemental wavelengths:
(a) the freedom from spectral interferences
(b) the different sensitivities and expected concentration in the samples.
The most sensitive line was not always used in order to avoid spectral interferences and to remain in the linear range. Observed interferences were compensated for by modifying the processing parameters (e.g. adjusting the background correction points, applying multicomponent spectral fittings (MSF) or inter-elemental corrections (IEC)). To compensate for instrumental signal variations, Ge (209.419) was added to every solution as an internal standard.
Since some elements were present as majors and others were present at trace levels, it was decided that the method validations would be done following two (2) avenues. For both dissolution methods, the accuracy and precision were evaluated on the high-concentration elements whereas spike recoveries were performed on the samples and the CRMs (Tables 4.3 and 5.3) to monitor the low concentration elements. The accuracy was determined by calculating the elemental recovery of certified reference materials (CRMs). The precision was determined by preparing and measuring 10 replicates of various CRMs. The results for each CRM are presented in Tables 4.1, 4.2, 5.1 and 5.2. The accuracy, precision and recovery results obtained demonstrate that the developed methods both perform very well.
Peroxide fusions and borate fusions combined with the simultaneous ICP-OES (Optima 7300 DV) have the analytical capabilities to perform the analysis of many high and low concentration elements in cosmetics following a controlled ashing procedure. Metal components were measured in a variety of cosmetic samples and reference materials, demonstrating good accuracy, precision and recovery. The dual dissolution capabilities of TheOx® allowed us to validate two dissolution methods and find that both peroxide fusions and borate fusions can be used for metal determination in cosmetic products. The results obtained show that borate fusions have a slight advantage due to the lower MDLs for the majority of the elements. Finally, both methods confirm the absence of heavy metals in the cosmetic samples.
Acknowledgments: Sylvain Roy, Lab technician | Claisse and Aaron Hineman, Product Specialist | PerkinElmer®