Tape-Based H₂S and Total Sulfur Analysis

How does tape-based measurement work?

In the tape method, sample gas passes over a chemically impregnated tape. Hydrogen sulfide reacts with the reagent on the tape and forms a dark stain. Lead acetate-impregnated tapes are typically used for H₂S. An optical detector measures the density of the stain; the rate of color change is proportional to the H₂S concentration in the sample.

After a set time, the tape advances one step and the measurement is repeated. For total sulfur measurement, the sample is first converted to H₂S with hydrogen in a reaction assembly and then measured on the same tape system.

What tape-based measurement measures and where it is used

The method is suitable for monitoring H₂S and total sulfur at low levels. Typical areas of use:

• Natural gas lines, LPG and refinery gas streams
• Outlet quality control of desulfurization units
• Catalyst protection and product specification monitoring
• Gas processing plants

Where tape-based measurement works well and where it struggles

The tape method offers high sensitivity for H₂S and can measure in the sub-ppm range. Thanks to optical reading and a simple mechanical design, it has long been used in process applications. Because it uses a selective reagent, it avoids interference from many hydrocarbons.

Limitations: the tape is a consumable and must be replaced at set intervals. The sample may need humidifying for the reagent to work; the carrier air and humidifier assembly need periodic maintenance. Measurement is not continuous but runs in cycles. The method is not directly suitable at high H₂S concentrations; in that case, sample dilution or another method (UV fluorescence, TDLAS) is preferred.

Choosing an instrument for tape-based measurement

The component to be measured (H₂S or total sulfur), number of streams, hazardous area certification and sample system requirements are the deciding factors. Tape consumption and maintenance interval should be included in operational planning. During commissioning, Tetra also configures the connection of the sample system, calibration valve and alarm outputs to the process control system, and supports basic maintenance training for the user's personnel.

Tetra and tape-based analyzers

In Türkiye, Tetra provides the supply, installation, commissioning and calibration of tape-based H₂S and total sulfur analyzers, along with spare parts such as tape, motors and detector blocks, and service support. The product range includes the Galvanic ProTech 903 (H₂S and total sulfur, ATEX/IECEx Zone 1) and the Keco 205P tape-based H₂S analyzer.