Qubit Flex Fluorometer with assay kit, strip tubes, and reagent reservoir

Here you can find the most up-to-date technical resources for your Invitrogen Qubit 4 and Qubit Flex Fluorometers, including a variety of application and technical notes such as Qubit Quantitation Platform vs. the Thermo Scientific Nanodrop Spectrophotometer and Testing for Bias in the Qubit RNA Assay, and the Qubit Frequently Asked Questions (FAQs).

For Qubit 1.0, Qubit 2.0 and Qubit 3.0 Fluorometers owners, see resources for previous models of Qubit Fluorometers


Product literature

Connecting the Qubit 3.0 or 4 to a computer running Windows operating system

Connecting the Qubit 3.0 or 4 Fluorometer to a computer running Windows operating system requires installation of a driver. You can download both the driver and installation instructions below.


Below are some frequently asked questions and answers regarding the Qubit Fluorometer and Qubit Fluorometric Quantitation.

If you have a question that is not listed below or need additional information, please contact our Technical Support department

Q. I already have a Nanodrop instrument. Why should I use the Qubit Fluorometer?
The Nanodrop instrument uses UV absorbance, which cannot distinguish between DNA, RNA, free nucleotides, and other contaminants.The Qubit assays are more sensitive than the NanoDrop instrument. NanoDrop Spectrophotometer full-spectrum absorption readings can give peaks revealing the presence of contaminants. This may be useful information for downstream applications in which the contaminants might be detrimental. When used together, the Qubit Fluorometer can accurately measure low concentrations of sample and the Nanodrop spectrophotometer can measure contaminants.

Q. Why are my UV absorbance readings higher than the Qubit Fluorometer readings?
UV absorbance readings measure anything that absorbs at 260 nm, including DNA, RNA, protein, free nucleotides, and excess salt. Qubit Fluorometric Quantitation only measures the molecule you are interested in, so the number is almost always lower than the A260 reading.

Q. Can the Qubit Fluorometer give an indication of sample quality?
Yes. You can use one of the DNA quantitation kits to measure DNA concentration, one of the RNA kits to measure RNA concentration, and the protein kit to measure protein concentration. Use a combination of whichever kits you need for the biomolecule you are interested in and the contaminant of concern. Together, they give you accurate information about how much DNA, RNA, and protein you have in your sample.

Q. I already have a Qubit Fluorometer, is Qubit 4 Fluorometer any different?
The Qubit 4 Fluorometer employs a large, robust color touch screen for seamless workflow navigation and exports data via WiFi, to a USB drive, or directly to your computer via a USB cable for efficient data management. Also, the instrument can be personalized to show only the frequently used assays, to add new assays, including user-defined assays created with the MyQubit assay design tool, and to display in the language of your choice including English, French, Spanish, Italian, German, simplified Chinese, and Japanese.

Q. Can I use my old Quant-iT Kits labeled “for use with Qubit Fluorometer” with the Qubit 4 Fluorometer?
Yes, these kits will work with all Qubit Fluorometers.

Q. How many lines of data can the Qubit Fluorometers store?
The Qubit Flex Fluorometer can store up to 10,000 samples' worth of data in a .csv file.
The Qubit 4 and 3.0 Fluorometer can store up to 1,000 samples’ worth of data in a .csv file.
The Qubit 2.0 Fluorometer can store up to 200 lines of data in a .csv file.
The original Qubit Fluorometer can store up to 20 lines of data in a .csv file.

Q. Do I have to use new standards every time?
For each assay, you have the choice to run a new calibration or to use the values from the previous calibration. As you first use the instrument, you perform a new calibration each time. As you become familiar with the assays, the instrument, your pipetting accuracy, and significant temperature fluctuations within your laboratory, you can determine the level of comfort you have using the calibration data stored from the last time the instrument was calibrated. We do recommend running a new calibration curve every time you prepare a new working solution.

Q. How long can the diluted standards be saved and reused? What if there is evaporation over time (obvious or not obvious)?
The diluted standards can be used for up to three hours if using the same working solution for the samples.

Q. Can Qubit Fluorometric Quantitation quantify plasmids?
 Yes. Use the Qubit DNA BR assay for a typical plasmid miniprep with lots of DNA (over 50 ng/μL). Use the Qubit DNA HS assay for “plasmid rescue” or methods that yield only small amounts of DNA.

Q. Is there a difference in signal between supercoiled and relaxed DNA?
 Yes. For supercoiled DNA, we recommend nicking the DNA so it is not supercoiled, or using supercoiled DNA as Standard 2.

Q. Does the Qubit Protein Assay work well in the presence of detergents?
 It is compatible with very small amounts of detergent. See “Contaminants Tolerated by the Qubit Protein Assay,” Table 2 on page 6 of the Qubit Protein Assay Kit product manual for specific amounts.

Q. How long does the lamp last? How do I change the lamp?
There are two LED light sources in the Qubit 2.0, 3.0, 4, and Flex Fluorometers. They are expected to last at least 5 years.

Q. Can I repair my Qubit Fluorometer?
No. The warranty will be voided if the instrument is disassembled or a customer has attempted to repair the instrument.

Q. What if my Qubit Fluorometer fails under warranty?
We will replace your Invitrogen Qubit Fluorometer. Please contact Technical Support for details.

Q. What kind of tubes do I need to buy?
Use thin-wall, clear 0.5 mL PCR tubes such as Qubit assay tubes or Axygen PCR-05-C tubes for the Qubit 4 Fluorometer or prior single-sample models. For the Qubit Flex Fluorometer, use the Qubit Flex Assay tube strips, which come as 8 x 200-µL thin-walled polypropylene tubes with very low fluorescence.


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Featured Application

Qualifying DNA preparations for next-generation sequencing (NGS)
Prior to committing the effort and resources required for next-generation sequencing (NGS), it’s important for researchers to be able to quantify and assess the quality of the DNA starting material. In a 2013 publication, Simbolo et al. reported a reliable and cost-effective method to qualify various DNA preparations for NGS, including those derived from frozen tissue and FFPE samples. Of the instruments they tested, their data showed that DNA quantification results obtained using the Qubit Fluorometer were highly reproducible and were consistent with qPCR data for DNA quantity—even for partially degraded DNA from FFPE samples.

Read the PLoS ONE article

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