What Is Chromium VI?
Chromium VI analysis determines the amount of hexavalent chromium that can form in chrome-tanned leather through oxidation of trivalent chromium. The specimen is extracted with a buffer solution and measured either colorimetrically after colour development with diphenylcarbazide (ISO 17075-1) or by ion chromatography (ISO 17075-2).
Purpose of Chromium VI
The purpose is to determine whether chromium VI in skin-contact leather products exceeds the regulatory limit. Chromium VI is a skin sensitiser and is restricted under REACH.
Which Products Is Chromium VI Applied To?
- Chrome-tanned leathers
- Footwear upper and lining leathers
- Leather gloves and clothing
- Bags, belts and leather goods
- Upholstery leather
In Which Sectors Is Chromium VI Used?
Standards Related to Chromium VI
- TS EN ISO 17075-1 (colorimetric method)
- TS EN ISO 17075-2 (chromatographic method)
- TS EN ISO 4044 (sample preparation for chemical testing)
- TS EN ISO 2418 (sampling location)
Chromium VI Conditions
- Extraction
- With phosphate buffer, protected from light, for the time defined in the standard
- Measurement
- Colour development with diphenylcarbazide; spectrophotometer or ion chromatography
- Limit of quantification
- The method's limit of quantification must be below the 3 mg/kg limit
Equipment for Chromium VI
- UV/Vis spectrophotometer
- Ion chromatography system
- Shaker and pH meter
- Mill (specimen grinding)
Sample Requirements for Chromium VI
- Specimen ground per ISO 4044
- The specimen must be protected from air and light
- The interval between sampling and analysis must be kept short
- A separate specimen for each leather type and colour
Duration of Chromium VI
The extraction and measurement steps determine the analysis duration; results are typically available within one to two working days. Because holding the specimen can change the result, analysis is carried out without delay.
Chromium VI Procedure
- 1The specimen is ground per ISO 4044 and weighed.
- 2It is extracted with phosphate buffer, protected from light.
- 3The extract is filtered.
- 4Colour is developed with diphenylcarbazide.
- 5It is measured by spectrophotometer or ion chromatography.
- 6The result is calculated in mg/kg.
Chromium VI Acceptance Criteria
REACH Annex XVII Entry 47 sets a 3 mg/kg limit for chromium VI in skin-contact leather articles. A result above this limit is non-compliant and the product cannot be placed on the EU market.
Evaluation of Results
Chromium VI can form during storage: leather that is below the limit at the time of analysis can oxidise and exceed the limit when stored in warm, lit conditions. A single report therefore does not prove compliance for the product's shelf life; re-testing after ageing may be required.
Chromium VI Report
- Specimen identification and tanning type
- Part of the standard applied
- Result (mg/kg) and limit of quantification
- Sampling and analysis dates
- Regulatory limit compared against
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- (EC) 1907/2006 REACH Annex XVII Entry 47
Footwear and Leather Testing — What Does This Testing Field Cover?
The section below describes the field that the Chromium VI test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Footwear and leather testing assesses the physical durability and chemical safety of a product together. Footwear is a MULTI-COMPONENT product: the sole, upper, lining, insole, heel and bonding line are tested both individually and together. One component being good does not mean the product is good; failure usually appears where components join.
On the physical side, the most common field failure is SOLE-UPPER SEPARATION. Bond strength is therefore the most critical measurement in the field and is a direct indicator of the bonding process (surface preparation, adhesive selection, pressing conditions). Next come sole abrasion and flex resistance: a shoe is flexed hundreds of thousands of times over its life.
Slip resistance is the most important parameter for safety and its measurement depends on the surface: wet ceramic, oily steel and dry floor give different results. Slip resistance is therefore reported not as a single number but with the surface and the direction of slip stated.
A separate body of work applies to protective footwear, and this is the most commercially critical distinction. Toe protection (impact and compression), penetration resistance, antistatic behaviour, heat and cold insulation, electrical insulation and fuel resistance are assessed under personal protective equipment requirements. CE is mandatory for these products and the category must be chosen correctly; an ordinary footwear test report does not satisfy that file.
On the chemical side, CHROMIUM (VI) has a special place in leather. The chromium (III) used in tanning can oxidise into chromium (VI) during storage and ageing; that is, a leather that was compliant at production may exceed the limit months later. The time of measurement and the history of the sample therefore affect the result, and measurement after ageing may be required.
Other chemical items are aromatic amines from azo dyes, pentachlorophenol, short-chain chlorinated paraffins, dimethyl fumarate and phthalates. These items come from REACH restrictions and brand restricted substance lists.
There is NO CE marking on consumer footwear; the obligation runs through material composition labelling, compliance with chemical restrictions and general product safety. Labelling has a rule of its own: the type of material used for the upper, the lining and insole and the outer sole is shown by pictograms.
Comfort and functional claims (waterproofness, moisture management, breathability) are supported by separate tests, and these claims require evidence if used in marketing copy.
Method groups in this field
Bonding and strength
Sole-upper bond strength, seam strength, heel attachment strength, strap and buckle strength.
Abrasion and flexing
Sole abrasion, flex resistance (dry and at low temperature), insole abrasion.
Slip resistance
Forward and backward slip measurements on wet ceramic, oily steel and dry floor.
Protective properties
Toe impact and compression resistance, penetration resistance, antistatic behaviour, heat and cold insulation, fuel and chemical resistance.
Leather chemistry
Chromium (VI), azo dye amines, pentachlorophenol, short-chain chlorinated paraffins, pH and fat content.
Comfort and function
Waterproofness, water vapour permeability, moisture management, colour fastness and the effect of perspiration.
Commonly confused in this field
- Footwear claiming a protective function falls under PPE legislation and requires CE; a consumer footwear test report does not satisfy that file.
- A chromium (VI) result depends on the age of the sample and its storage conditions; leather compliant at production may exceed the limit later.
- Slip resistance is not a single number; it cannot be interpreted without stating the surface and the direction.
- A result obtained for one component does not cover the whole product; the joints are tested separately.
- Labelling rules run on material pictograms; an incorrect pictogram causes problems in customs and market surveillance.
- A waterproofness claim is not verifiable unless the test used and the number of flex cycles after which it was measured are stated.
Which decisions these results support
- Compliance with the brand restricted substance list
- The PPE category and CE file for protective footwear
- Supplier and lot-based acceptance control
- Root cause analysis of field complaints (bond opening, sole separation)
- Substantiation of functional claims
Related Tests
Frequently Asked Questions About Chromium VI
Can chromium VI be found in vegetable-tanned leather?
Not expected if chromium was not used. However, cross-contamination can occur if chrome tanning is also carried out at the same facility, and matrix interference can produce a false positive in some measurements. The claim should be backed by analysis.
The result came in just below the limit — are we in the clear?
A result close to the limit carries risk. Because chromium VI can increase with time and temperature, the limit can be exceeded during shipping and storage. Preventive measures against oxidation should be considered on the production side.