PHARMACEUTICAL & BIOTECHNOLOGY
APPLICATIONS
ROCKY MOUNTAIN INSTRUMENTAL
LABORATORIES
Mass spectrometry, especially
HPLC/MS/MS, is an important and quite useful technique for the detection,
identification, quantitation and analysis of small pharmaceutical molecules,
peptides, proteins, and oligonucleotides and their metabolites and degradants.
With our SciEx triple quadrupole instruments with ElectroSpray and
NanoSpray ionization, we can be especially effective in the analysis of
small quantities of proteins and protein digests. We also offer APCI
(Atmospheric Pressure Chemical Ionization) as this technique sometimes
gives better sensitivity than does ESI, especially for small or
non-polar molecules. In addition to conventional tandem triple quadrupole
instruments, we also have a SciEx API-4000 Q Trap, which combines the great
sensitivity and quantitative accuracy of the other SciEx triple quads with
a Linear Ion Trap (LIT) capability. This allows for both greater
sensitivity and the ability to perform MS3.
This enables better and faster degradant identification and
peptide sequencing.
There are several common
modes of obtaining mass spectra. These include: Time-of-flight (TOF), quadrupole,
ion trap, magnetic sector, and combinations of these. Ionization techniques
commonly used in biotechnology and pharmaceutical analysis for non-volatile
samples include Matrix-Assisted Laser Desorption/Ionization (MALDI), Electrospray
Ionization (ESI), Atmospheric Pressure Chemical Ionization (APCI) and Fast
Atom Bombardment (FAB). Each technique has its own set of advantages and
disadvantages. That is, no one technique will solve all problems.
We will be happy to assist you in the choice of technique most appropriate to
your needs.
Tandem quadrupole mass spectrometry
(MS/MS) is especially useful for the analysis of pharmaceuticals in biological
samples because it allows for a very large improvement in the signal to
noise ratio (S/N) by effectively excluding interfering substances from
the analysis. Similarly, the use of both CI (chemical ionization)
and EI (electron ionization) can increase specificity and sensitivity.
This is why we are able to quantitate many molecules down to the 10pg/mL
level in plasma and solid tissues.
We
offer both HPLC/MS/MS and GC/MS/MS. We have established even smaller
LOD and LOQ for certain molecules.
One of our specialties is the analysis of
anti-proliferative drugs, including paclitaxel (Taxol), rapamycin, tacrolimus,
mycophenolic acid, and doxorubicin in both formulated materials and in clinical
biosamples, including solid tissues.
Proteins,
peptides, and oligonucleotides may be analyzed by the use of Electrospray
Ionization (ESI) of effluents from a
liquid chromatograph
or capillary electrophoresis system. This is because it is possible to
generate an envelope of multiply charged species whose m/z is within the
mass range of the spectrometer (generally up to 3000 amu). Deamidation,
iso-aspartate formation, and other post-translational modifications and
the polymer sequence can be identified in proteins and peptides with relative
ease and excellent mass accuracy (1, 2).
Oligonucleotide
molecular weight determination and sequence confirmation is performed by
very similar means, except that the sample preparation is a bit different
and negative ion mode is used (3). Because we use quadrupole MS/MS, we
are able to perform parent ion scans, which often improves S/N significantly
(5).
Our newest acquisitions is
a SciEx 4000Q system. This affords greater sensitivity for both small
and large molecules, and adds to our metabolite characterization capability.
Mercedes will join Maude and Mathilde in our happy LC/MS family.
There now are several instrument
manufacturers who sell combination quadrupole - TOF mass spectrometers
for use with HPLC. They can be enormously useful in some cases, but
tend to make conventional triple quadrupoles seem to be inexpensive.
REFERENCES:
1. D. R. Marshak (ed.) "Techniques
in Protein Chemistry" This is a series of excellent books which contain
papers presented at the Protein Society Symposia. Published by Academic
Press. Very inexpensive, remarkably so for the high quality of information
provided. The earlier volumes have information which is especially useful
to anyone just starting in modern protein and peptide analysis. See
volumes V and VI, particularly. (800)-782-4479
2. D. W. Aswad "Deamidation
and Isoaspartate Formation in Peptides and Proteins" CRC Press (1995).
3. J. Stults and J. Marsters
"Improved Electrospray Ionization of Synthetic Oligonucleotides" Rapid
Comm. in Mass Spec. 5, 359-363 (1991).
4. G. Suizdak "Mass Spectrometry
for Biotechnology" Academic Press (1996). This is an excellent introduction
to mass spectrometry, in general, and to the biotechnology applications,
in particular, and is quite inexpensive. 800-782-4479.
5. G. Neubauer and M. Mann
"Parent Ion Scans of Large Molecules" J. Mass Spectrometry 32
94-98 (1997).
6. R. K. Lantz and P. L.
Sulik, "Liquid Chromatography - Mass Spectrometry: A Users Perspective"
European Pharmaceutical Contractor, October, 1998.
7. R. B. Cole, ed.
"Electrospray Ionization Mass Spectrometry: Fundamentals, Instrumentation,
and Applications" Wiley (1997). Superb text for both the novice
and the expert.
For additional information:
970-266-8108 303-530-1169
Rocky Mountain Instrumental
Laboratories, Inc.
108 Coronado Ct.
Ft. Collins, CO 80525
LAST UPDATE:
17 APRIL 2012