SPOTLIGHT FEATURE Sample Preparation & Processing


From analysis to action: Process reliability and environmental protection through fast, automated H₂S measurement technology


Dr Dorit Wilke, Dr Michael Hahn, ECH Elektrochemie Halle GmbH, Germany


Hydrogen sulphide (H₂S) is a widespread but dangerous by-product in wastewater treatment as well as in crude oil and natural gas processing. In wastewater treatment plants, it is produced during anaerobic digestion processes, while in the petroleum industry it is a component of many ‘sour’ crude oils and gases. In both cases, H₂S poses a serious threat to humans, materials, and the environment - it is corrosive, toxic, harmful to the climate and has a strong odour.


Modern, automated H₂S measurement technology not only enables the precise detection of critical concentrations in real time, but also provides the basis for targeted countermeasures, whether for odour control, plant safety, or compliance with legal limits.


The article shows how current measurement technologies can be used in wastewater and petrochemical processes to implement the necessary treatment measures in a targeted and cost-effective manner.


Hydrogen sulphide (H2 S) plays a significant role in


wastewater treatment and the petroleum industry, as it can occur in various stages of the processes and poses a complex challenge. The main problems associated with H₂S in industrial applications are:


1. Corrosion risk for steel and other metals used in refineries and pipelines, as well as for concrete components, which play an essential role in sewage systems. In Germany alone, an estimated €475 million worth of calcium nitrate and €54 million worth of iron(II) chloride chemical additives must be used annually to prevent odours and corrosion [1].


2. Safety risk, as hydrogen sulphide is a colourless, highly flammable gas that is toxic in high concentrations. Even low concentrations (from around 100 ppm) can cause serious health problems, and concentrations above 700 ppm can be fatal within a very short time. The industry must therefore implement rigorous safety measures and monitoring systems to protect workers and facilities from possible exposure.


3. Quality impairment of crude oil and natural gas: ‘sour’ oils require additional processing steps during refining, such as hydrodesulphurisation (desulphurisation), in order to reduce the sulphur content and comply with environmental regulations. Hydrogen sulphide is removed from petroleum and natural gas using various processes, such as gas scrubbing or the Claus process, in which hydrogen sulphide is converted into elemental sulphur. The sulphur is either used as a by-product or disposed of safely. According to USGS Mineral Commodity Summaries 2025, global sulphur production (mostly from Claus plants) is approximately 79–80 million tons per year (as elemental sulphur). Of this, >90 % comes from the desulphurisation of natural gas and petroleum [2].


One advantage of the headspace technique is that the vials used are disposable materials that do not require extensive cleaning


4. Environmental impact and regulations: Since hydrogen sulphide can release sulphur dioxide (SO₂) during combustion, leading to acid rain and other environmental problems, the petroleum industry is heavily regulated to limit emissions of sulphur compounds. The costs (OPEX) of complying with the older Euro standards for diesel (50 ppm) are usually in the range of $0.3–0.8/bbl., while for 10 ppm sulphur (ultra-low sulphur diesel, EU/ USA) this cost is $0.8–2.0/bbl. With global production of approximately 28,342 kbbl./d of diesel products in 2024, this represents enormous additional costs [3].


In order to act effectively, the most important prerequisite is the reliable determination of sulphur contamination in the process. There are only a few specific measurement


methods for detecting corrosive hydrogen sulphide. Some of these are very time-consuming or costly. This is due, on the one hand, to the very low levels that need to be determined and, on the other hand, to the difficult matrix that needs to be analysed: highly viscous petroleum oils, particulate-laden wastewater, heavily coloured samples and sludge, and solids with inclusions.


Sulphide determination in water and wastewater The new method for determining sulphide/H2


S in


aqueous solutions is carried out in accordance with the new ASTM D8536-25 and DIN 38405-27:2017 standards by combining highly efficient gas extraction with a selective electrochemical detection method. After dosing, the sample is acidified in the H2 which expels H2


an amperometric sensor that detects H2


S analyser,


S gas from the solutions. The gas enters S with high


sensitivity. The precision and accuracy are higher than with the determination methods commonly used to date. The measurement time is between 5 and 15 minutes. The analysis of the sample without any sample pretreatment has a particularly beneficial effect on reproducibility. Matrix components of the sample are effectively separated due to the indirect determination method, so that cross-sensitivities hardly occur.


The sample volume to be dosed can be selected within a wide range (10 µl to 50 mL). This allows a linear measuring range from 0.01 mg/L to 1 g/L to be recorded without having to dilute the sample. The sample can be transferred directly from the sampling vessel to the analyser. This prevents oxidation losses. By selecting the pH value of the acidification, it is possible to distinguish between easily extractable sulphides and the total sulphide content. With the aid of phthalate buffer pH 4, it is thus possible to determine the non-firmly bound alkali sulphides in aqueous samples, which are also considered an immediate danger to humans, the environment, and corrosive plant components. With the addition of 8 % phosphoric acid, the sulphides bound to iron and other metals are also released and detected. This provides an excellent opportunity to monitor and control scrubber solutions or treatment strategies, for example by avoiding an excess of iron precipitants or detecting an underdose of treatment agents. The capacity of amine scrubber solutions for gases can also be monitored easily and in a very short time.


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INTERNATIONAL LABMATE - FEBRUARY 2026


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