GAS CHROMATOGRAPHY
RESOURCE GUIDE
Streamline Your Gas
Chromatography Workflows
for Peak Performance
Optimize sampling, calibration, and troubleshooting
for seamless end-to-end results
AUTOMATING GC CALIBRATION CHOOSING
Sample Preparation and Quality Control A Chromatography
Data System (CDS)
Table of Contents
3 Improving Gas Chromatography Workflows From Sample
Prep to Data Analysis
5 Automation for Gas Chromatography Sample Prep
7 Monitoring Environmental Pollutants with Gas
Chromatography Techniques
11 The Importance of Calibration and Quality Control in Gas
Chromatography
13 Gas Chromatography Detectors
15 Ensuring Effective Maintenance with a Chromatography
Data System
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o Improving Gas
r Chromatography
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I Prep to Data Analysis
Practical strategies to enhance the efficiency, accuracy, and
reproducibility of your GC processes
Gas chromatography (GC) is a widely used technique in analytical laboratories, valued for its
precision and versatility across many fields in industries—from environmental monitoring to
pharmaceuticals and food safety. Optimizing GC instruments and workflows enables labs to
unlock the full potential of this technique.
In high-throughput labs, automation is crucial to support higher volume and more complex
analyses. Automating GC sample preparation can considerably enhance throughput, reduce
human error, and improve reproducibility. With options ranging from robotic systems to
advanced autosamplers capable of running dilutions and derivatizations, automated sample
prep is transforming how labs operate. It reduces manual labor and ensures more consistent,
high-quality results.
Equally important is calibration and quality control. Regular calibration ensures that your
GC system delivers accurate, reliable results while ongoing quality control measures main-
tain the integrity of your data.
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o Advancements in chromatography data systems (CDS) are enabling better management of
i large datasets, ensuring that data acquisition, analysis, and reporting are more efficient and
compliant with regulatory standards. By incorporating a robust CDS, labs can also improve
t preventive maintenance, identifying issues before they cause costly downtime.
c
This resource guide outlines strategies to optimize end-to-end GC
workflows, covering automation of sample preparation, effective sampling
u for environmental pollutants, and selecting the right detector for your lab’s
applications. It also offers guidance on calibration, quality control, and
choosing a chromatography data system for maintenance, along with a
d troubleshooting checklist.
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Automation for Gas
Chromatography
Sample Prep
Automating sample prep can be crucial for labs running
GC at higher throughputs
by Mike May, PhD
To separate the components in a sample with gas chroma- as part of AGAGE’s mission to study changes in chemicals
tography (GC), proper sample preparation is important. The and climate around the world. This platform could capture
sample may be cleaned up in various ways to improve the a two-liter sample of air, concentrate desired samples with
selectivity of the separation, and it must be volatilized prior an adsorbent-filled trap kept at about -55°C, and analyze the
to injection into a GC platform. The preparation can be chemical components down to concentrations of 0.2 parts
manual or automated, depending on the application and the per trillion.
required throughput.
In some cases, automating GC sample preparation just
doesn’t make sense in terms of time or financial cost. Labs “Some robots can automatically
that prepare a few samples at a time probably won’t see
much benefit from automation. However, labs that run more prepare samples, and several GC
GC and at higher throughputs should consider automating
preparation. autosamplers are capable of running
Commercial options dilutions, derivitizations, and more.”
There are several options for GC sample preparation
automation on the market. Some robots can automatically
prepare samples, and several GC autosamplers are capable
of running dilutions, derivitizations, and more. There are That system triggered even more advanced technology. For
several features and capabilities to consider when choosing instance, at the University of California, San Diego/Scripps
automation technology, including: Institution of Oceanography, Jens Mühle notes that AGAGE
uses “our most advanced GC-MS systems—the ‘Medusa’ au-
• Programmable workflows tomated gas chromatographic systems with mass spectromet-
ric detection—for ultra-low-level, high-precision, long-term
• Barcode scanning reproducible measurements of ozone-depleting substances
and synthetic greenhouse gases.” This system uses two traps,
• Compatibility with sample types which are filled with polymer absorbents to automatically
concentrate specific analytes. These traps are kept at a colder
• Integration with GC systems temperature, about -165°C, to allow the capture of a wid-
er range of chemicals, especially more volatile ones. With
• Vial sizes and formats dual traps, it uses fractional distillation to purify analytes
of interfering compounds, refocusing from a large trap to a
• Throughput smaller one. Consequently, this automatic sample prepara-
tion produces reproducible injections for GC-MS.
• Reproducibility
From the comfort of a lab to some distant testing site, auto-
• Additional handling options (pipetting, heating, cooling, mating parts of GC sample preparation can come in handy
mixing, and agitation) in some cases and be indispensable in others. It all depends
on the lab and the application.
• Scalability with add-on modules
Refined research methods
Sample prep automation began decades ago. In 1994, scien-
tists working on MIT’s NASA-sponsored Advanced Global
Atmospheric Gases Experiment (AGAGE) installed an
automated GC-mass spectrometry (MS) system in Ireland
6 Lab Manager Gas Chromatography
Monitoring Environmental Pollutants
with Gas Chromatography
Techniques
Sampling technique is the foundation for reliable monitoring of environmental
pollutants via GC
By Brandoch Cook, PhD
Before the Industrial Revolution, life was often harsh and contaminants, highlighted by infamous moments like the
short. As society progressed, people found ways to thrive, Cuyahoga River catching fire, polluted by industrial waste,
but this came at a cost—living amid harmful factory waste and flowing into Lake Erie. This event came between two
and polluted air. Prosperity brought greater exposure to other environmental wake-up calls: the publication of Silent
7 Lab Manager Gas Chromatography
Spring, exposing how the pesticide DDT built up in living environmental pollutants and, coupled with mass spec-
tissues, and the disaster at Love Canal, where toxic waste troscopy, their identification and quantification. Moreover,
from the Hooker Chemical Company led to the creation of the regulatory mandate requires the identification of as
the Superfund program. many compounds as possible under constraints of time and
expenditure, which is optimal for single capillary GC in-
Fortunately, increased environmental concern evident jections that can be replicated and judged against standards
in legislation such as the Clean Water Act and the estab- to make pragmatic decisions about what we can drive, eat,
lishment of the Environmental Protection Agency (EPA) breathe, or throw away.
coincided with the development and availability of gas
chromatography (GC) techniques and instrumentation Principles and methods of sampling
pioneered by James and Martin. The high resolution of and extraction
GC, combined with its accuracy and dynamic concentra-
tion range, make it supremely adaptable to the separation of Raoult’s and Henry’s laws determine the efficiency with
which VOCs can be extracted after sampling. The vapor
pressure of a volatile compound in solution is proportional to
its molarity, and by extension, the amount of a gas dissolved
in liquid is proportional to its partial pressure above that
Environmental Pollutants liquid. Headspace sampling is the preferred method for
extraction of VOCs for GC injection, either in a static format
Three broad categories of environmental pollutants or, more commonly, via purge and trap (P&T).
are analyzed by GC under EPA guidelines, and
the accuracy and fidelity of their measurement is In static headspace measurements, VOCs in a closed sample
dependent on proper sampling and extraction: vial migrate into the upper vapor phase over time to reach an
equilibrium. One then injects a portion of this “headspace”
1. Volatile organic compounds (VOCs) into the GC apparatus.
aromatic hydrocarbons such as BTEX (benzene,
toluene, ethylbenzene, and xylene) largely
found in petroleum derivatives; halocarbons like “The high resolution of GC,
trichloroethane from industrial solvents; freons
used in refrigeration; and alcohols often used as combined with its accuracy and
oxygenating agents in gasoline. dynamic concentration range,
2. Semi-volatile organic compounds (SVOCs) make it supremely adaptable to
acid-extractable phenols and base-extractable
anilines and amines (including nitrosamines); the separation of environmental
and polycyclic aromatic hydrocarbons, putative
carcinogens in petroleum emissions. pollutants.”
3. Pesticides and polychlorinated biphenyls (PCBs)
PCBs and organochloride pesticides such Headspace constituents can also be extracted dynamically,
as DDT are highly persistent and resistant to greatly increasing efficiency, using P&T devices. In P&T, an
breakdown, while phosphorous- and nitrogen- inert gas (often helium) purges the sample to extract VOCs,
based pesticides are more acutely toxic but move which are retained in an adsorbent trap. Heating the trap
releases VOCs in a plug, which is injected into the GC port by
through ecosystems more quickly.
back-flushing the trap with carrier gas—helium, hydrogen, or
8 Lab Manager Gas Chromatography
nitrogen. Traps are commonly composed of layers of differ- lower thresholds are usually allowed based on a combination
ent adsorbent materials to optimize extraction in a gradient of 1) adverse effect testing in animals and 2) natural rates
of relative volatility that can be desorbed in reverse order of decay. This condition, therefore, requires GC detectors
to avoid trapping and desorbing water, which can confound with greater sensitivities. An electron capture device detects
GC analysis. organochlorines in the range of parts per billion, and a ni-
trogen-phosphorous detector functions similarly for organo-
SVOC extraction is intrinsically more complicated because phosphorus and nitrogenous pesticides. Although PCBs have
their higher boiling points preclude gas-phase extraction been banned in the United States since 1979, they are highly
techniques. Therefore, investigators use liquid-liquid and stable and cycle between water and soil; at least 30 percent
solid phase extractions, in addition to Soxhlet extraction, of Superfund sites on the National Priorities List still have
all of which commonly use methylene chloride and acetone confirmed PCB contamination.
as solvents. Soxhlet extraction applies a drying agent to
samples, which are placed in a thimble between opposing It is also possible to investigate pollutants in the field, either
layers of glass wool, with a collection flask from which sol- for quality-control purposes or to identify potential stress-
vent cycles in a loop, purifying analytes to be subsequently ors on regulated resources or impacted sites. Regardless of
applied to GC. the field, GC remains a powerful and versatile method of
environmental monitoring and measurement, and proper
Pesticides and PCBs can be extracted from various matrices sampling is its foundation.
in analogous manners. However, because of their greater
propensities to be ingested directly as residues on food,
9 Lab Manager Gas Chromatography
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The Importance of Calibration
and Quality Control in Gas
Chromatography
Protecting the integrity of research
By Nathan Roman
Precision and accuracy are both critical in the field of ana- adhere to regulatory standards. Due to the sensitive nature
lytical chemistry, especially in techniques like gas chroma- of GC, it is vital that researchers subject their GC systems to
tography (GC). It is through diligent calibration and quality stringent calibration and QC measures to ensure the preci-
control (QC) that these factors are maintained, serving as sion and accuracy of their work.
the framework for robust systems that safeguard results and
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The calibration essentials From concept to reality: overcoming
challenges
When it comes to GC, calibration is an important process
that aligns the measurements obtained from the GC with Calibration and QC in gas chromatography demand preci-
known standards, establishing a reliable basis for accurate sion, awareness, and careful preparation. Awareness involves
analysis. This is fundamental because GC is employed across monitoring for performance shifts, sample behavior vari-
a spectrum of critical applications, from identifying pollut- ations, regulatory standards updates, and environmental
ants in environmental monitoring to determining the purity changes. Preparation encompasses selecting and preparing
of pharmaceutical products. Without precise calibration, the calibration standards, ensuring the GC system is clean,
integrity of these analyses could be compromised, leading setting operational parameters, and preparing control sam-
to inaccurate data and potentially severe consequences in ples. These steps underscore the interconnected nature of
terms of health, safety, and compliance. Calibration ensures calibration and quality control in maintaining the scientific
that the GC system can accurately translate sample con- integrity of GC analysis.
centrations into meaningful data points, which is essential
for making informed decisions based on the analysis. By
ensuring the GC system is properly calibrated, researchers
and professionals can trust the data it generates. “Calibration ensures that the GC
Regular recalibration is crucial for accurate gas chromatog- system can accurately translate
raphy analysis. Industry best practices recommend recal- sample concentrations into
ibrating equipment every six months or more frequently,
depending on usage intensity and analysis complexity. meaningful data points, which
Recalibration should also be performed after major changes
or when accuracy drifts due to wear and tear. Environmental is essential for making informed
factors, such as notable shifts in temperature or humidity,
can also warrant recalibration. decisions based on the analysis.”
Quality control: the champion behind
the scenes
Embracing calibration and QC in gas chromatography is a
After calibration—the first critical step in the QC pro- commitment—a promise to strive for accuracy, dependabil-
cess—the focus shifts to QC, which encompasses a broader ity, and repeatability. It’s about protecting the integrity of
set of procedures (such as tracking performance parameters, scientific research and ensuring the safety and effectiveness
preventive maintenance, and documentation) designed to of products across industries.
maintain and verify the accuracy of the GC system over
time. During analytical runs, QC is manifested through
the systematic use of control samples alongside the samples
being analyzed. Control samples—not to be confused with
calibrators—typically mirror the composition of test samples
but with concentrations of analytes that are already known
and verified. These controls may be sourced externally or
prepared separately from the calibration process, serving as
independent validations of the GC system’s performance.
It is crucial to understand the difference between calibrators
and controls. Calibrators set benchmarks for measurements.
Meanwhile, controls act as checkpoints to track progress
along the path set by the calibrators.
12 Lab Manager Gas Chromatography
Gas
Chromatography
Detectors
Selecting the best detector for your samples and
applications
by Mike May, PhD
Gas chromatography (GC) is useful for numerous applica- It’s not all about the concentration, though, because selec-
tions ranging from pharmaceuticals to food and beverage, tivity might also matter. A universal detector such as a TCD
materials science, forensics, and many more. Once GC sepa- or a barrier discharge ionization detector has pros and cons.
rates a sample into its component parts, a detector is used to You’ll see everything coming through the GC, but that can
identify them. also be problematic. Consequently, this approach typically
requires some higher resolution chromatography, such as a
There are two general categories of detectors: universal multidimensional technique, or cleanup steps at some point
detectors that detect all (or most) compounds that elute, and to partition some of the components. Otherwise, co-elution
selective detectors that detect only compounds with specific would render the data useless.
properties. Thermal conductivity detectors (TCD), helium
ionization detectors, barrier ionization detectors, and even
mass spectrometry (MS) are universal detectors.
“There are two general categories of
A universal GC detector, such as a flame-ionization detec-
tor (FID), provides a collection of benefits. Overall, these detectors: universal detectors that
detectors are easy to use and inexpensive and look for many detect all (or most) compounds that
compounds. FID is known for its linearity and dynamic
range capabilities. elute, and selective detectors that
Although MS is also universal, it comes in a variety of forms. detect only compounds with
For instance, a single quadrupole MS uses one filter to
separate ions based on the mass-to-charge ratio. These types specific properties.”
of MS systems enable users to quantitate known lists of com-
pounds as well as information about unknown compounds.
Scientists turn to specific GC detectors when looking for a Some of this can be resolved with triple-quadrupole MS,
needle in a haystack. In these cases, the application doesn’t which consists of two mass filters with a collision cell be-
need to identify every compound in a sample, just certain tween them. Only the ions of interest get through the first
ones. This category includes electron-capture and sul- mass filter, then the collision cell dissociates the components,
fur-specific detectors. and then the second mass filter measures the partitioned
pieces. This technology provides the best low-level detection
Making your selection of a known list of compounds in a matrix, but it is not ideal to
determine whether there are other compounds in the sample
The required detection level often determines the best de- that aren’t on the known list.
tector for a specific application. For example, maybe some-
one needs to measure a gas, but not at a very low concen- Not every application fits an available option. In those cases,
tration. That probably calls for GC/TCD, which provides a researchers need extra help to build the right GC/detector
sensitivity down to high parts per million. system, and that often means turning to a vendor for advice.
Getting the system performing properly probably requires
For applications that need higher sensitivity, scientists need some back and forth with a vendor. In the end, most scien-
more sophisticated technology. For example, a pulsed dis- tists will make some compromises, but the range of options
charge helium ionization detector can pick out components improves the odds of finding an affordable and effective
at concentrations in the high parts per billion. system.
For trace analysis of target analytes, scientists turn to GC-
MS, which can “see” down in the low parts per billion range.
Along with sensitivity, GC-MS has the added benefit of posi-
tive compound identification via library spectral matching.
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Ensuring Effective Maintenance
with a Chromatography
Data System
CDS programs can play a vital role in ensuring consistency and efficiency in
your chromatography research
By Roger Reeve
Chromatography data systems (CDS) play a crucial role The improved resolution and advances in detector technology
in the lab, generating accurate and reliable data in various have led to higher sensitivities, which in turn have increased
scientific fields. They deliver productivity gains, ensure data the volume of data generated by chromatography systems.
integrity, and fully support Good Manufacturing Practice When combined with the continuous drive to improve, en-
compliance. sure, and demonstrate data quality, as well as the need to effi-
15 Lab Manager Gas Chromatography
ciently manage large equipment fleets, it’s easy to see why the up to 10 times the cost. Timely maintenance also reduces the
automation of chromatographic analysis (including instrument chances of unexpected breakdowns or interruptions that can
control, data acquisition, integration, and reporting of results) disrupt lab operations. Being proactive with maintenance
undertaken by a CDS can be highly beneficial. doesn’t just mean less downtime, it also saves labs from costly
emergency repairs, resulting in long-term cost savings.
Two key drivers for CDS implementation are data compli-
ance—especially for extensive equipment networks—and By utilizing the features of the CDS to inform targeted
process workflow optimization. Integrating a CDS can be a maintenance, labs can maintain the efficiency, precision, and
step toward establishing a broader electronic documentation reliability of their chromatography systems.
workflow. This improves process efficiencies by reducing
wait times for signatures and consolidating documentation
sources. It also provides a comprehensive electronic audit
trail. Additionally, process bottlenecks can be easily iden- How to Choose a Chromatography
tified, and updates can be consistently applied across the Data System (CDS)
entire equipment fleet in a networked system. The basic purpose of a CDS is still to acquire analog
However, one often overlooked area that can be informed detector voltages and convert them to quantifiable
by the CDS is preventative maintenance. Regular mainte- digital signals. A modern CDS must serve two parallel
nance plays a vital role in maximizing equipment efficiency, directives: First, for the laboratory, predicated on
productivity, and preventing downtime. Because the CDS maximizing productivity, minimizing training and
continuously monitors equipment usage, the data can be user error, and ensuring end-to-end compliance and
used to target maintenance needs based on usage, identifying
consistency. Second, it must satisfy IT concerns, which
key components for replacement before they fail.
are dependent on stability, scalability, and security.
Better performance and reliability
There are three types of CDSs:
Prioritizing maintenance optimization on your CDS can
• Standalone programs that control one
have a positive impact on productivity. Over time, system
components can wear out, leading to reduced efficiency or chromatograph
even system failure. By implementing a targeted mainte-
• Programs that can oversee two or more
nance program, faulty components can be promptly identi-
fied and replaced, preventing unexpected system downtime chromatographs
and reducing the risk of data loss.
• Networked platforms providing control and com-
Data accuracy and compliance munication among multiple instruments across linked
sites, with up to thousands of users and subscribers
By performing annual maintenance, closely monitoring
system performance, and verifying that the system operates Features to look for in a networked CDS:
according to original manufacturer specifications, you can
ensure maximum productivity for your system. Accurate • Data acquisition from the start of sample injection
and reliable data is crucial, especially in regulated industries
like pharmaceuticals or environmental analysis. Annual • Automated and customizable data processing,
maintenance not only ensures data reliability but also helps including peak integration, identification,
maintain the validity and traceability of analytical results. calibration, report generation, and data archiving
Long-term cost savings • End-to-end instrument control
It is important to consider that the cost of repairing a failed • Contemporary regulatory compliance with audit trail
piece of equipment can be much higher, potentially reaching
16 Lab Manager Gas Chromatography
GAS CHROMATOGRAPHY
TROUBLESHOOTING
TIPS FOR QUICKLY RETURNING TO NORMAL OPERATION
While the theory of gas chromatography (GC) is often learned in classes, users generally learn about opera-
tion and troubleshooting through hands-on experience. Below are some tips for troubleshooting GC.
01 GENERAL STRATEGY RULES FOR TROUBLESHOOTING
GC METHODOLOGY
{ Change only one thing at a time
{ Carefully document all maintenance and troubleshooting activity
{ Check the most obvious and routine things first: maintenance logs, cables and
connections, check for leaks, etc.
{ Isolate system components and steps: confirm proper sample prep, perform a
blank run, connect an alternate injector or detector, and install a different column
GENERAL AND DETECTOR ISSUES 02
During a single GC analysis, a multiple-injection sequence, or an analysis of
longer duration, problems may arise. Check the following:
{ Ran out of carrier or detector gases, or solvent in autosampler wash vials
{ Failure to draw sample due to syringe bending or other problem
{ Leaking septa
{ Inlet liner contamination
{ Flame ionization detector (FID) jet plugging
{ Thermal conductivity detector (TCD) signal noise or spikes due to ambient
pressure fluctuations
03 DIAGNOSING DETECTOR ISSUES
Detector problems are rare, but they can be diagnosed using the following steps:
{ Run a no-injection system blank, solvent blank, or QC check standard
{ Execute a method-detection limit test
{ Perform a signal-to-noise check
{ Conduct a sample breakdown check
{ Execute a system precision test
{ Recalibrate the method
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