Light Obscuration

Method Introduction

Light obscuration (LO) is listed in the pharmacopeias Ph. Eur. 2.9.19, USP <788>, USP <787> and USP<789>. During measurement, the sample is drawn into the system through a needle, and particles passing a laser beam block a certain amount of light and produce a “shadow” on a light-sensitive detector. The area of this shadow is then converted to an equivalent circular diameter of the particle based on a calibration curve generated with polystyrene standard beads.

LO allows the counting and sizing of subvisible particles in the size range from about 1 to 200 µm. The upper particle concentration limit is system-dependent, usually about 10^5 and 10^6 particles/mL. The pharmacopeias give specifications for particles >10 µm (less than 6,000 particles per container for low-volume parenterals of 100 mL or less) and particles >25 µm (less than 600 particles per container for low-volume parenterals of 100 mL or less). However, the quantification of smaller subvisible particles (>1 µm) is nowadays also expected by the regulatory authorities. At Coriolis, we have many years of experience using low-volume methods for the LO analysis of numerous biopharmaceutical products.

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Applications

The LO technique is used during all stages of development, from early research to batch release testing, to quantify subvisible particles. At Coriolis, LO can be offered in full GMP compliance.

The main advantages of light obscuration are the high sampling efficiency, as the whole sample volume can be analyzed during the measurement, and the short measurement and data handling times. However, the presence of air bubbles and the formation of Schlieren patterns can result in erroneously high particle levels in LO measurements. However, a well-established sample preparation procedure can avoid these issues. Like all light-based techniques, LO depends on a difference in refractive index between particle and solvent. The validity of LO results should thus be validated by using orthogonal methods.

Quality and Biosafety Level

We provide all our analytical services with the highest quality standards. Experienced scientists carry out each project, and a scientific reviewer comprehensively checks every report or data presentation.

We offer this technology with the following quality and biosafety levels:

Up to GMP Level

This method is available under GMP in dedicated labs with qualified equipment and full QA involvement.

Up to biosafety level 2

This method can be applied to nucleic acids, viruses, cells, viral vectors, including lentiviruses, and more.

Analytical Method Development, Qualification and Validation

For common sample types, we can often apply standardized methods with little setup effort. However, when needed, our experienced analytical experts create or optimize custom methods tailored to your active pharmaceutical ingredient, product type and development phase.

Method Development

Our method development approach tailors sample preparation, method settings and data analysis to the needs of your project and sample.

We include representative samples and, where available, suitable reference standards and stressed/degraded materials, allowing our analytical scientists to design a highly suitable, stability-indicating, robust and repeatable method. Upon request, we will compile a detailed description of the method for your records.

Method Qualification

Method qualification is the initial assessment of an analytical procedure’s performance to show its suitability for its intended purpose.

During method qualification, our analytical scientists perform documented testing demonstrating that the analytical procedure meets criteria in several categories. Criteria may include factors such as repeatability, specificity and robustness. We compile a qualification plan and report, including all relevant data.

Method Validation

Under GMP conditions, method validation confirms that an analytical procedure’s performance suits its intended purpose. Depending on the method’s scope, a broad range of method characteristics, such as specificity, accuracy, precision, limit of detection/limit of quantification (LOD/LOQ), linearity and range, is considered.

During method validation, our analytical scientists perform documented testing demonstrating that the analytical procedure consistently produces a result that meets the predetermined acceptance criteria. We compile a validation plan and report that includes all relevant data.

Depending on the development phase, a fit-for-purpose validation approach can be offered, adjusting the validation required efforts in a phase-appropriate way to meet the method’s needs.

Method Verification

Compendial method verification confirms that a compendial method (e.g., from Ph. Eur. or USP) is suitable and reliable for its intended purpose under the specific conditions of the laboratory.

Unlike full method validation, compendial method verification is often considered a partial validation since the method has already undergone extensive testing and validation during its inclusion in the compendium. The extent of method verification depends on the type of method.

During method verification, our analytical scientists perform documented testing demonstrating that the developed analytical method performs adequately for the specific product or matrix being tested and within the specific laboratory where the method will be employed.

Talk to Our Experts or Request a Quote

Our expert team is ready to answer your questions and guide you to the services best suited to your program’s modality, stage and challenge. If your needs are well-defined, we’ll begin the quotation process.

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