What is Slope Spectroscopy®?

A Unique and Patented Variable Pathlength Technology (VPT)

Providing a more efficient method for analyzing at-line and in-line processes, slope spectroscopy is a UV-based technology that serves as an alternative to the Beer-Lambert Law that focuses on pathlength as the variable that determines concentration.

How does Slope Spectroscopy® work?

Called Slope Spectroscopy® due to the slope this technique creates when there is a change in absorbance over a change in pathlength, this method leverages the power and flexibility of variable pathlength technology to create rapid and robust concentration measurements.

UV-based, this method analyzes samples at variable pathlengths using a precision linear stage to efficiently collect multiple absorbance data points to calculate a slope regression. Generating a slope value (absorbance over pathlength) allows you to quantify the concentration with higher accuracy, rather than relying on a single data point using absolute absorbance.  

Unlike traditional spectroscopy — where the concentration is the variable — our method uses the pathlength as the variable, allowing the concentration to remain constant. When the concentration remains constant, you are able to eliminate dilution and decrease the chances of contamination and that creates a more reliable end result and product.

Traditional UV

Traditional spectroscopy uses concentration as the variable and a single data point using absolute absorbance


Slope Spectroscopy Method

The Slope Spectroscopy® technique uses pathlengths as the variable and collects multiple absorbance data points to calculate a slope regression

The Slope Spectroscopy® Difference

A different approach to UV-Vis

Decrease Errors

Traditional UV-Vis spectroscopy relies on a fixed pathlength at a single absorbance data point. By locking in the pathlength the user is forced to “unlock” or change the concentration to an acceptable level which leads to an error-prone process.

Increase Accuracy

Slope Spectroscopy® provides multiple absorbance data points from different pathlengths offering greater insight into sample and measurement results. 

Save Time

The Slope Spectroscopy® method using our instruments and software can report concentration results in less than two minutes. The SoloVPE System works at-line, while the FlowVPX System works in-line. Our ViPER software automates your analysis, so you just focus on the sample preparation and the resulting report. The intuitive software detects change in absorbance, and auto adjusts pathlength accordingly.

Product Feature




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Data Collection In-line process monitoring
Inline UV-Measurement

System Suitability Testing Capability

Minimum 5-Second Cycle Acquisition Time

CE System Certification

ViPER™ Software Compatibility

21 CFR Part 11 & Annex 11 Compliance

Analog I/O

Automated Zeroing

Smart Cell Operation

Process Status Indicators

C1D2 Rating

IP Rating IP65
Concentration Range 0.1–300 mg/mL
Flow Cell Size Compatibility Increase scalability
Minimum Pathlength Step Size 1 µm
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