Innovative Optical Density Measurement System Protects Product from Contamination

A pharmaceutical manufacturer in Argentina faced the challenge of measuring the optical density of a sterile solution in-line without the possibility of product contamination. METTLER TOLEDO developed a reliable solution that ensured sterility was not compromised, and which also reduced product loss.

Production of injectable corticoidsteroid

Química Montpellier S.A. is a pharmaceutical laboratory with production facilities in Buenos Aires, Argentina. In recent years, facilities and equipment at its manufacturing plant have been extensively refurbished, positioning it among the most modern pharmaceutical laboratories in South America. The company produces betamethasone injections, a corticoidsteroid used in the treatment of allergic reaction symptoms. For increased efficacy, the vials of betamethasone combine soluble and insoluble forms of the active drug.

Optical density determines active principle concentration

The concentration and uniformity of the insoluble form (acetate or dipropionate) is determined by measuring samples in the lab. This is a time-consuming operation and does not confirm uniformity throughout a batch. Química Montpellier technicians wanted a method of measuring the concentration of the insoluble form at the filling line in a continuous way to ensure dose uniformity, without any risk of product contamination.

As the only insoluble component of the formulation is the insoluble form of the active pharmaceutical ingredient (API), the optical density (OD) of the medium is proportional to the concentration of the API.

OD measurement through glass

METTLER TOLEDO, through its representative in Argentina, HITEC S.R.L realized that the betamethasone could be measured through glass by an OD sensor before entering the vials, therefore eliminating contact between the sensor and the solution. To achieve this would require redirecting the flow of betamethasone through a glass tube placed inside a specially developed housing.

After some research at HITEC's facility, a housing was developed that would hold a METTLER TOLEDO optical density sensor at the optimal angle and encase the glass tube to prevent unwanted light ingress that would affect measurement results. The system was installed and a test phase initiated. Results showed a very precise correlation between measurements from the new system and those obtained by the off-line method.

API concentration ensured

Benefits of this system are numerous: continuous real-time data, assurance of betamethasone uniformity in every finished vial, instant detection of out-of-spec bulk suspension (eliminating incorrectly filled vials, reducing product loss and increasing the overall yield per batch), PAT initiative compliance through enhancement of process understanding, and time and cost savings from reduced lab measurements.

Química Montpellier is more than satisfied with the OD system's performance. As well as the above benefits, technicians note that system maintenance is very low; the sensor rarely requires cleaning since coating and fouling do not occur.

For more details:

Contact details:

Mettler-Toledo International Inc.

Im Langacher,  Zip Code 8606

Greifensee, Switzerland


Phone: +41-44-9443385


About METTLER TOLEDO Process Analytics

METTLER TOLEDO's Process Analytics division develops and manufactures instrumentation and sensors used for process measurement and control, offering measurements of pH, dissolved and gaseous oxygen, dissolved ozone, turbidity, oxygen reduction potential, resistivity/conductivity, total organic carbon and flow.

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