tation wavelengths used in Raman spectroscopy has had a
significant impact on the extent to which material analysis
is affected by fluorescence.
Raman devices traditionally use visible excitation
wavelengths such as 532nm and 785nm. Although these
shorter excitation wavelengths have a strong Raman scattering, they are also affected by fluorescence interference
which increases background intensity. Strong fluorescence
decreases the dynamic range of the detector, limiting the
signal-to-noise ratio and consequently the identification
ability of the device.
Due to the fact that fewer materials fluoresce at longer
excitation wavelengths, wavelengths like 1064nm allow
for a more comprehensive range of materials to be analyzed, particularly within biopharm applications. A new
generation in handheld Raman spectrometers that utilize
a 1064nm excitation laser (such as the Progeny™ from
Rigaku) will enable more valuable and colored materials,
such as cell culture media, to be identified.
Cell Culture Analysis with 1064
Small changes in the composition of cell culture media
can have a dramatic effect on the health and validity of
cell lines so it is therefore crucial that it undergoes accurate, precise analysis. The advantages of using a 1064nm
analyzer for cell culture media analysis, compared to a
785nm analyzer can be clearly demonstrated, as seen in
The spectra shown in Figure 1 are from a Minimum
Essential Medium formulated by Harry Eagle, which is one
of the most commonly used synthetic cell culture media.
The Raman spectra collected at 785nm and 1064nm excitation are also shown in Figure 1. The 785nm spectrum is
dominated by fluorescence making it impossible to obtain
reliable and specific information about the sample. In contrast, the 1064nm spectra show clear Raman peaks that can
be used to reliably identify the media.
Figure 2 shows the Raman spectra using a 1064nm laser
from two cell culture media, both of which are versions of
a minimum essential medium developed by Harry Eagle,
that have only small differences in their components. Clear
differences can be seen in these Raman spectra and when a
correlation analysis was performed these two media could
be accurately and reliably distinguished.
Spectra affected by fluorescence do not reveal detailed
Advances in Raman Spectroscopy
information about specific compositional differences or
Another important consideration in biopharmaceutical
production is the requirement for 100 percent inspec-
tion of incoming raw materials in most countries by the
Pharmaceutical Inspection Convention and Pharmaceutical
Inspection Co-Operation Scheme. Handheld Raman can
help to optimize the raw material identification process
(RMID) to ensure quality control and compliance with
these industry regulations.
Raman spectroscopy is a popular analytical technique for
RMID in pharmaceutical applications due to its sensitivity,
specificity and ease of use. Raman spectroscopy focuses a
laser on a sample. The light scattered from the sample is
measured to provide highly detailed chemical information.
The specificity of Raman comes from the fact that it is a
vibrational technique and measures any chemical or physical changes that will affect molecular vibrations and alter
the Raman spectrum.
Smaller and more reliable spectrometers have been
developed through improvements in components such as
the laser, detector and electronics. These spectrometers
are enabling fast sample analysis at the point of need,
eliminating the need for expensive and time consuming lab
Recognized by the United States Pharmacopeia (USP)
and the European Pharmacopoeia (EP) as a viable technique for compendial identification, Raman spectroscopy
is a non-destructive, reliable, efficient and cost effective
method for the analysis of complex cell culture media.
Some biopharmaceutical materials, such as cell culture
media, are susceptible to fluorescence when being analyzed which can make it impossible to obtain reliable and
Cell Culture Media Identification
Handheld Raman devices help speed quality and efficiency in biopharm products
n By Claire Dentinger, Ph. D., Sr. Applications Scientist, Rigaku Raman Technologies