Nephelometry / Turbidity


Nephelometry / turbidity is a quick and non-invasive technique for the detection of relative changes in aggregate and particle content in a liquid sample.

A laser light passes through the sample and either the scattered light is detected, e.g., at an angle of 90° to the laser source (= nephelometry) or the transmitted light is detected at an angle of 180° to the laser source (= turbidity). Typically, a laser wavelength in the range of 320–800 nm is used in order not to be absorbed by formulation components, such as proteins, peptides, DNA/RNA, formulation excipients (e.g., amino acids), and water. In both cases, the clarity and degree of opalescence of samples is measured according to a setup described in current pharmacopoeias (Ph. Eur. 2.2.1 and USP <855>) and assigned based on comparative measurements against reference formazin suspensions.

Nephelometry / turbidity measurements are nonspecific, but highly useful for a relative comparison of samples, e.g., for rapid screening of protein aggregation during formulation development.

The technique requires limited sample preparation and is non-destructive. Although nephelometry / turbidimetry does not provide information about size, concentration, or nature of protein aggregates or particles, the technique is often used to detect relative changes in the aggregation status. Because of its high sensitivity, nephelometry / turbidity is capable of detecting the formation of particles in liquid samples very early during forced-degradation or stability studies. It should be noted, however, that turbidity can also originate from other factors, such as high protein concentration, and does not necessarily reflect the presence of aggregates or particles.

Quality & biosafety level of this method

We provide all our analytical services with the highest quality standards. Each project is carried out by experienced scientists and every report or data presentation is comprehensively checked by a scientific reviewer. We offer this technology with the following quality and biosafety level:

Standardized methods or dedicated method development

For common sample types, we can often apply standardized methods with little setup effort. On top of this, our experienced analytical scientists perform in-depth method development or method optimization tailored to your drug substance, product type and development phase. Under GMP, we also offer full method validation or compendial method verification.


Method development

During method development, we tailor sample preparation, method settings, and data analysis to the needs of your project and sample.

For this purpose, we include a representative sample and, where available, suitable reference standards and stressed/degraded materials. This way, our analytical scientists can design a method that is highly suitable for your needs, stability indicating, as well as robust and repeatable. Upon request, we compile a detailed method description for your records.


Method qualification

A method qualification is the initial assessment of the performance of an analytical procedure to show that it is suitable for the intended purpose.

During method qualification, our analytical scientists perform a documented testing that demonstrates that the analytical procedure meets certain acceptance criteria in several categories. These may include repeatability, linearity, intermediate precision, robustness and more. We compile a qualification plan and a qualification report including all relevant data.


Method validation

A method validation is the confirmation under highly controlled conditions that the performance of an analytical procedure is suitable for the intended purpose.

During method validation, our analytical scientists perform a documented testing, which demonstrates that the analytical procedure consistently produces a result that meets the pre-determined acceptance criteria. We compile a validation plan and a validation report including all relevant data.

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