Frequently Asked Questions | Analytics


It all comes down to time savings and reliability. With variable pathlength technology, the time previously spent sending samples out for analysis for preparation and dilution is removed because dilution is not necessary. VPT Systems dial down quantitation into its most essential steps— measuring and reporting—while reading ten data points for each measurement in less time than it takes other UV instruments to take one.


This depends on a number of factors, for example, the size of the molecule and the associated extinction coefficient. Using variable pathlength technology, however, sample absorbances that could never be seen on a standard 1 cm cuvette can be analyzed and worked with – we’ve recorded cases of measurements being possible up to 300 mg/mL completely undiluted for monoclonal antibodies and 200 mg/mL for DNA plasmids, with a lower limit of 0.01 mg/mL. But as mentioned previously, these limits can differ significantly from sample to sample, so Repligen Analytical Representative are happy to work with our customers to develop the optimal method for a particular sample.


Yes. However, unlike other UV systems, buffer or baseline correction is often unnecessary. Because Slope Spectroscopy® relies on the change in absorbance associated with changes in pathlength, the absolute absorbance level does not matter. What does matter is the rate of change—the slope.

In instances where the buffer notably contributes to the sample concentration (typically, seen at lower concentrations), baseline correction can be easily toggled on and off in our software.


Yes, the CTech™ SoloVPE® System and CTech™ FlowVPX® System are designed for full GMP compliance, supplemented by our comprehensive SecureVPE software. SecureVPE is our in-house, security-focused application that has become commonplace for those in regulatory environments—we’ve been integrated into those environments for more than 10 years, providing users the ability to create records and audit trails.

To help qualify your system, our dedicated bioanalytics team will work with companies to design a plan for validation for that software as a platform within the company. We offer a range of services to cover exactly what you’re looking for—whether it be working with the IT group to answer basic questions, providing a protocol or computer system validation manual for the IT group to run, or, over the course of a few days, coming in on-site ourselves to execute a full validation protocol that covers the entire validation of the software. Throughout the entire process, you are supported by our team.


Yes! We work with each company’s laboratory and IT team to help define the method for the instrument in question, develop the documentation associated with it (including standard operating procedures and validation protocols), and to validate the software. We can even come in and validate the platform for you. Get in touch with a Repligen Analytics Representative to discuss your plan or schedule a visit.


We know how important it is for your process to be up and running, so the installation and qualification of a VPT System takes less than a day to complete. Our protocol covers repeatability, filter tests, transmission optimization, hardware checks, and testing standards on the System. We also offer complementary training from one of our Repligen Analytics Representative to help familiarize your technicians and scientists with the System and all its functions.

After installation, one of our Repligen Analytics Representative will reach out to you to help plan validation on your schedule. We realize you might have time constraints and different resource demands for each project, so we work with you to determine how much time you can spend within your time frame.


Our VPT Systems are designed specifically to use with a Cary 60 spectrophotometer as a light source—we work with Agilent Technologies to supply a Cary 60 with each System, and use and maintenance of the Cary for your process is handled by our support group.


There is no manual calibration needed. It is recommended that the light source, the Cary 60 spectrophotometer, be shut off and turned back on once a week. During this reinitialization, the Cary 60 self-calibrates. For the SoloVPE System, we recommend that it be requalified once or twice a year by one of our Repligen Analytics Representatives.


Yes. Typically, the most common area where our Systems are mobile is in manufacturing suites, where they are installed and qualified on a transportable cart to the areas of the process for subsequent analysis.


Absolutely! To plan a demonstration, contact us here and a member of our bioanalytics team will reach out to discuss the details of our visit.