Application NoteRESIDUAL GAS ANALYSIS

Process Monitoring in Pharmaceutical Lyophilization
Freeze-drying is a manufacturing process that uses vacuum sublimation to stabilize food and pharmaceutical products prior
to long-term storage. In many cases, the shelf life of freeze-dried materials is extended from hours or days to several months
or years. Although highly effective, freeze-drying is slow and inefficient. Therefore, in the pharmaceutical domain, it is reservedfor only the most sensitive materials. In these applications, high standards of stability, purity, and integrity of end-products are
non-negotiable, making process development costly and time consuming. Residual gas analysis is a powerful tool that can beused to mitigate these pain points. Currently, many facilities rely on indirect measurement tools such as Pirani or capacitancemanometers to monitor the freeze-drying process. While these gauges provide some insight into the overall pressure within thechamber, they often fall short in offering a comprehensive understanding of the gas composition or detecting trace contaminants.
This lack of specificity can lead to undetected issues, potentially compromising product quality. The limitations of these traditional
methods underscore the need for more advanced and direct analytical techniques to ensure optimal process control and productintegrity. By continuously analyzing the composition of residual gases during freeze-drying, a residual gas analyzer (RGA) offers
real-time insights into key process variables, including leak detection, endpoint determination, monitoring contaminants andleaks (O2), sterilization/cleaning operations (H2O2), API/formulation decomposition and product meltback/collapse1. This in-depth
understanding aids in quality control, process optimization, and regulatory compliance.

Experimental
The Transpector CPM 3 compact process monitor isintegrated with a research and development freeze-dryer(REVO® by Millrock Technologies Inc.) to monitor the gas
composition inside of the process chamber during the freezedrying process. An image of the setup is shown in Figure 1.
Pressures during freeze-drying are typically on the order of
100 mTorr, several orders of magnitude above acceptablevalues for conventional RGAs. Transpector CPM 3 is ideallysuited for this application due to a specially designed orificedosing system with differential pumping that ensures proper
flow rate compatibility. In addition, INFICON offers single
pressure mass spectrometers, like Transpector SPS andTranspector APX, that are compatible with harsh chemistries.
®

Typical Process Pressure
Range for Freeze Drying

Transpector CPM 3Total Pressure Range

1e-2 Torr - 1 Torr

1e-8 Torr - 1.2 atm

Figure 1: INFICON Transpector CPM 3 installed on Millrock REVO
lyophilizer in the LyoHub Demonstration Facility at Purdue University.

reachus@inficon.com   |   inficon.com

Gas Composition Monitoring via Mass
Spectrometry in Monoclonal Antibody
Freeze-Drying
Monoclonal antibodies are proteins used to treat a variety
of disorders, infections, and conditions. They are generally
unstable in solution at room temperature and therefore
administered as a freeze-dried dosage form. The measured
gas composition during freeze-drying of a monoclonal
antibody formulation is shown in Figure 2. During primary
drying, water vapor (m/z=18) sublimes from the frozen
product and fills the process chamber. In this case, the wateraccounts for roughly 90% of the total composition. The freezedryer injects nitrogen (m/z=28) ballast to regulate the absolutechamber pressure around a target setpoint of 100 mTorr. Near
the beginning of the process where the sublimation rate is high,the nitrogen concentration is low. As the process continues, thesublimation rate decreases, and the freeze-dryer introduces
more nitrogen to compensate for the load reduction. At theend of the cycle, all ice has been sublimed and the water vapor
concentration decreases rapidly. According to Figure 2, argon(m/z=40) follows a similar trend to nitrogen. The nitrogen
supply is derived from a liquid source that, due to their similarboiling points, also contains argon in trace quantities. The CO2(m/z=44) and O2 (m/z=32) species trend with water vapor,suggesting they were dissolved in the water prior to freezing.

Figure 2: Residual gas analysis data for monoclonal antibody
formulations1. Please see Table 1 for m/z ratios.

Process Monitoring in Pharamceutical Lyophilization |    Application Note

Real-Time Contamination Detection in
Pharmaceutical Lyophilization Using
Residual Gas Analysis

Mass Spectra of Species CommonlyFound in Freeze-Drying
m/z Ratio

RelativeAbundance

1817162814321640204428161245

10.2120.009
10.13810.21810.14610.098
0.096
0.087
0.01

17
16
1514
18

1
0.801
0.075
0.022
0.004

In the field of pharmaceutical lyophilization, contamination
detection is paramount for ensuring product quality andsafety. Silicone-based oils are frequently used as heattransfer or cooling fluids during the freezing phase of theprocess. However, leaks of these coolants into the freezedrying chamber pose a significant risk. Once a product is
contaminated, it is irrecoverable and must be discarded,leading to significant financial loss and delays. RGAs offer
an effective solution for this challenge by providing realtime detection capabilities. They can promptly identify thepresence of coolants like silicon-based oils, thereby alerting
operators to a contamination event as it occurs. See Figure 4
for an example of silicon oil spike detection. This allows for
immediate intervention and helps to maintain the integrity ofboth the ongoing process and the end product.

Compound
H2O
N2
O2
Ar

CO2

NH3

Table 1: Mass Spectra of Species Commonly Found in Freeze-Drying

Optimizing Freeze-Drying Cycles for
Organic Co-Solvents:
Insights from Transpector CPM 3

Figure 4: Silicon oil spikes3.

Organic co-solvents are sometimes required for compoundingor stabilizing complex freeze-dried systems. In many cases, theorganic component often has a high saturated vapor pressure
and low freezing point, making them difficult to freeze-dry using
conventional cycles. The ability to monitor the concentrationsof the individual systems is therefore highly desirable.
Transpector CPM 3 provides this capability, allowing highly
optimized cycles to be quickly and easily developed. Figure 3
contains the process data for a complex formulation ofD-Mannitol dissolved in a 2-Butanol (m/z=45) and water cosolvent system. In this case, the 2-butanol has a higher vapor
pressure than water and is completely removed prior to watervapor.

Conclusion
The integration of the INFICON Transpector CPM 3
RGA into pharmaceutical freeze-drying offers numerous
advantages for process development and optimization.
By enabling precise detection and quantification of various
volatile and non-volatile species, Transpector CPM 3
enhances process control, assures product quality, andconfirms chamber integrity. The adaptability of this tool tocomplex formulations positions it as an indispensable asset
in the modern pharmaceutical manufacturing landscape.
Moreover, the non-intrusive nature of Transpector CPM 3
ensures that the process environment remains undisturbed,
maintaining sterility—a paramount concern in pharmaceuticalapplications. Given these benefits, residual gas analysis
stands as a cornerstone technology for advancing the stateof-the-art in pharmaceutical lyophilization.
For more information    inficon.com
Connelly, J. P., & Welch, J. V. (1993). Monitor lyophilization with mass spectrometer gasanalysis. PDA Journal of Pharmaceutical Science and Technology, 47(2), 70-75.
1Liechty, E.T., Strongrich, A.D., Moussa, E.M. et al. In-Situ Molecular Vapor Composition
Measurements During Lyophilization. Pharm Res 35, 115 (2018). https://doi.org/10.1007/
s11095-018-2395-4.
Ganguly, A., Stewart, J., Rhoden, A., Volny, M., & Saad, N. (2018). Mass spectrometry
in freeze-drying: Motivations for using a bespoke PAT for laboratory and production
environment. European Journal of Pharmaceutics and Biopharmaceutics, 127, 298-308.
3Figure 3: Residual gas analysis data for D-Mannitol in 2-Butanol andwater2.

reachus@inficon.com   |   inficon.com

Due to our continuing program of product improvements, specifications are subject to change without notice.

aial42a1-a2