McFarland (Cell Suspension Density, Turbidity Solutions)

The McFarland Method | Implen OD600® & McFarland App | McFarland Calibration Curves

The McFarland Method

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The McFarland method is a widely recognized technique for estimating the concentration of bacterial suspensions by comparing the turbidity of the sample to a set of predefined standards. These standards, known as McFarland standards, are based on the light scattering properties of solutions with known bacterial concentrations. This approach provides a simple yet effective means of ensuring consistency and accuracy in microbiological experiments.
McFarland standards are crucial for various applications, including antimicrobial susceptibility testing, where precise bacterial concentrations are necessary to determine the efficacy of antibiotics. They are also used in the preparation of inocula for culture inoculation and other microbiological assays, ensuring that bacterial suspensions have a consistent and reproducible density.
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Typically, McFarland standards range from 0.5 to 10, with each standard representing a specific bacterial concentration. For example, a 0.5 McFarland standard corresponds to approximately 1.5 x 108 CFU/mL (colony-forming units per milliliter). By visually or instrumentally comparing the turbidity of a bacterial suspension to these standards, researchers can accurately estimate the concentration of bacteria in their samples.
The simplicity and reliability of the McFarland method make it an essential tool in clinical laboratories, research facilities, and industrial settings, where precise bacterial quantification is critical for experimental success.

Implen OD600® and McFarland App

Unparalleled Accuracy and Convenience
in McFarland Measurements

Our Implen OD600® device, paired with the advanced McFarland App, delivers unparalleled accuracy and convenience for McFarland standard measurements. This integration ensures precise turbidity measurements and streamlines the process for researchers.

The Implen device is highly adaptable, supporting various cuvettes and test tubes without the need for adapters, including DiluCells, 10mm macro and semi-micro cuvettes, and 10, 12, 16, and 18 mm glass/falcon tubes. This versatility allows seamless operation across different sample types and experimental setups.

McFarland Calibration Curves

Using the McFarland App, the absorbance (Abs) values of samples are measured and converted to McFarland Units (MFU) via a calibration curve. The process begins with generating a calibration curve by measuring Abs values of individual samples with known MFU levels and increasing turbidity. These values are plotted, creating a curve that forms the basis for determining the MFU of unknown samples.

One of the standout features of the McFarland App is its ability to save and recall calibration curves. Users can store calibration data for each specific tube or container type, ensuring that calibration values remain intact even after the device is switched off. If recalibration is needed, the App provides a specialized standard curve function that guides users through the process, ensuring ongoing accuracy and reliability.

The McFarland App offers an intuitive user interface, making it easy to follow prompts and instructions throughout the measurement and calibration process. Calibration values are securely stored within the system, allowing users to easily recall or update them as necessary.

By leveraging the combined power of the Implen OD600® device and the McFarland App, scientists can achieve consistent and accurate McFarland standard measurements, significantly enhancing the reliability of their microbial research and experiments.

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