Formazin

Formazin is a polymeric suspension used to prepare standardized turbidimetric reference solutions for water quality testing. It serves as the primary reference turbidity standard for nephelometric instruments, allowing laboratories to calibrate meters and validate methods. Turbidity values for Formazin standards are reported in Formazin Turbidity Units (FTU) and in modern practice also in Nephelometric Turbidity Units (NTU). The two units are related, with NTU being the international standard, and, at low turbidities, roughly equivalent to FTU.

Formazin standards are produced by dispersing a Formazin polymer in deionized water to form colloidal suspensions with known turbidity. These standards cover a range of turbidities, typically from a few NTU to tens of NTU, and are used to generate calibration data for turbidity meters. Stock solutions should be prepared and stored under recommended conditions, protected from light to minimize changes over time.

Safety and handling: Formazin preparations may involve hazardous materials; appropriate laboratory safety practices are required, including the use of gloves, eye protection, and proper waste handling per regulations. Containers and stock solutions should be labeled with hazard information.

Limitations and context: Formazin standards provide continuity with historical turbidity data, but the formulation can degrade over time, and stability depends on storage conditions. Some laboratories use alternative standards or instrument-specific calibration routines, especially as newer reference materials become available.