The dichromate method - Alternatives urgently needed

Potassium dichromate is also known as double potassium. It is used in the tannery, in certain printing processes and in the chemical analysis. For instance the chemical oxygen demand (COD) of water is determined by the definition of potassium dichromate method (dichromate method DIN 38409-41: 1980-12).

A few years ago it was only classified as irritant but today it is considered to be mutagenic, toxic for reproduction and dangerous for the environment as well as carcinogenic. The European Parliament and the Council called 'REACH' (Registration, Evaluation, Authorisation and Restriction of Chemicals) have adopt a ban in April 2013, which prohibits the use of this chemical. Manufacturer of COD tests, which employ Potassium dichromate, can apply for a special individual permission for re-use. The European Commission adopts a final decision about the exceptional authorizations.

Because of the dangerous dichromate method, the varying recovery rates, the known chloride interferences as well as the high demand of time of 2h alternative approaches are urgently required. A first step to use a constant sample matrix, is to adjust a correlation factor, according to the mixture of substances in water. Thus, the fast and reliable Online-TOC-Measurement technology can also be used for COD determination. An additional alternative is the direct measurement of the oxygen demand. With LAR's QuickCOD_ultra, the online analyser to determine the total oxygen demand, both alternatives are possible. The measuring system operates with the ultra-high temperature method at 1200 ° C and goes with no dangerous chemicals.

Due to the patented sampling system FlowSampler a blockage-free sampling is ensured. The QuickCOD determines reliably fluctuating loads and peak loads up to 200,000 mg / l and provides measurement results in a few minutes. The water sample is taken event dependently and without any pretreatment such as dilution, or other modifications by chemicals or additives. Only this way, the sample is reliably detected in its entirety, including all contained particles, and the true load is determined.

The sample is injected into the reactor by the proven XY- technology. The robotic horizontally and vertically moving needle takes an exact sample dose in the micro-liter range and injects it into the oven through the patented lock valve. It ensures that the oven stays 100% sealed from the ambient air at any time. This guarantees that all ingredients are oxidized, completely at 1200 ° C whether volatile or not. This process control reduces carryover effects, blockages and down times. With this smart sample feeding components such as flakes or solids do not disturb the measurement. They are rather recognized as an important part of the sample and also considered completely.

The COD measurement has become indispensable for a cost-effective process control and monitoring. A measuring instrument that provides reliable and fast results is not only inevitable in fact of that, but also to observe all guidelines and regulations. LAR's QuickCOD_ultra fulfills these requirements and, additionally, is an environmentally friendly and safe alternative to the dichromate method.