What is pH and why is it important?

pH describes the acid-base character of an aqueous solution (scale 0–14). It directly influences chemical reactions, product quality, corrosion and biological processes — making it one of the most measured process variables.

Which pH sensors are available for process use?

Potentiometric glass electrodes, ISFET sensors (semiconductor-based) and combined pH/ORP single-rod assemblies are common. For hygienic applications, aseptic versions per DIN 11864 are available.

How often do pH sensors need calibration?

Typically every 2–4 weeks under normal conditions, more frequently in aggressive media or high GMP environments. MEMOSENS sensors allow pre-calibration in the lab and fast in-situ exchange.

What is glass corrosion and how to prevent it?

At high pH (>12) or in HF-containing media, the glass membrane can be attacked. Special high-alkali glass, ISFET sensors or coated membranes are the remedy — depending on process conditions.

Measurement Principles

InlineOnlineAt-line

pH Measurement

pH measurement determines the acid-base content of a solution and is one of the most widely used inline measurements in Process Analytical Technology (PAT).

Installation Types

Inline

Sensor directly in the process stream — no sampling, continuous real-time measurement.

Online

Automatic sampling via bypass loop — short analysis times, close to the process.

At-line

Sample analysed next to the line — flexible location, manual or automatic sampling.

Relevant Industries

Pharma & Bioprocess

Inline control of API synthesis using NIR spectroscopy

Environmental Monitoring

Continuous water body monitoring per EU Water Framework Directive

Energy & Water Supply

Steam/water circuit monitoring in power plants (pH, conductivity)

Food & Agriculture

NIR moisture, protein and fat determination on conveyor belts

Standards & Regulations

DIN 38404-5ISO 10523USP <791>DIN 11864

FAQ

Dusko Kadijevic | Publisher Analytic Journal | analyticjournal.com

Written March 2026. All content formulated in our own words, created with AI assistance.

© 2026 Analytic Journal / Dusko Kadijevic. Short excerpts with attribution and a link to analyticjournal.com are permitted. Full or substantial reproduction, including by AI systems or automated processes, requires written permission. Enquiries: info@analyticjournal.de