Hexavalent Chromium Test

1. Introduction to Hexavalent Chromium

Hexavalent chromium is an ingestible poison and highly toxic inhalant. It exists in the form of oxyanions, Cr⁶⁺. In acidic solutions, it primarily appears as orange Cr₂O₇^2-, while in alkaline solutions, it is mainly yellow CrO₄^2-.

2. Hazards

Hexavalent chromium is an ingestible poison and highly toxic inhalant. Skin contact may cause allergies; it is more likely to cause hereditary genetic defects, inhalation may lead to cancer, and it poses a persistent danger to the environment. However, these are characteristics of hexavalent chromium; chromium metal, trivalent, or tetravalent chromium do not possess these toxicities.

Hexavalent chromium is easily absorbed by the human body and can enter through the digestive tract, respiratory system, skin, and mucous membranes. Inhalation of air containing varying concentrations of chromium trioxide can cause hoarseness and atrophy of the nasal mucosa, and in severe cases, perforation of the nasal septum and bronchiectasis. Ingestion can lead to vomiting and abdominal pain. Skin contact can cause dermatitis and eczema. The greatest hazard is the risk of cancer from long-term or short-term exposure or inhalation.

Hexavalent chromium compounds are carcinogenic in the body and can cause many other health issues, such as runny nose, sneezing, itching, nosebleeds, ulcers, and perforation of the nasal septum when inhaling certain high concentrations. Short-term, high-dose exposure can cause adverse effects at the site of contact, including ulcers, nasal mucosa irritation, and nasal septum perforation. Ingestion of extremely high doses of chromium can lead to kidney and liver damage, nausea, gastrointestinal irritation, stomach ulcers, convulsions, and even death. Skin contact can cause ulcers or allergic reactions (hexavalent chromium is one of the metals most likely to cause allergies, second only to nickel). Experimental studies have shown that high-dose feeding of hexavalent chromium to mice affects reproduction, reducing the number of pups per litter and decreasing fetal weight. The greatest hazard is the risk of cancer from long-term or short-term exposure or inhalation.

Excessive hexavalent chromium (above 10 ppm) is lethal to aquatic life. Experiments show that hexavalent chromium in contaminated drinking water can cause cancer. Hexavalent chromium compounds are commonly used in electroplating and other industries. When animals drink water containing hexavalent chromium, it is absorbed by cells in many tissues and organs.

Residual hexavalent chromium in leather can be absorbed through the skin and respiratory tract, causing damage to the gastrointestinal tract, liver, and kidneys. It may also harm the eyes, leading to retinal bleeding and optic nerve atrophy.

3. Main Uses of Hexavalent Chromium

Uses in electronic products: Hexavalent chromium is often used as chromic acid in the electrochemical industry. It is also used as a coloring agent in pigments (i.e., lead chromate) and as a corrosion inhibitor in cooling water circulation systems, such as in heat absorption pumps, industrial freezers, and refrigerator heat exchangers.

Uses in the galvanized steel industry: Hexavalent chromium is used for post-plating passivation treatment of galvanized sheets to enhance their corrosion resistance and durability.

4. Hexavalent Chromium Testing Standards and Regulations

China National ROHS Hexavalent Chromium Limit Requirements
GB/Z 21275 Test Method for Restricted Substance Hexavalent Chromium in Electrical and Electronic Products
GB/T 15555.4 Determination of Hexavalent Chromium in Solid Waste—Diphenylcarbazide Spectrophotometry
QC/T 942 Test Method for Hexavalent Chromium in Automotive Materials
EU ROHS Hexavalent Chromium Limit Requirements
IEC 62321-7 Standard for Determination of Hexavalent Chromium in Metal Coatings by Colorimetry
ISO 17075-1 Determination of Hexavalent Chromium in Leather by Colorimetry
ISO 17075-2 Determination of Hexavalent Chromium in Leather by Chromatography

GN 7467 Determination of Hexavalent Chromium in Water Quality—Diphenylcarbazide Spectrophotometry