MARKES UNITY Operators Manual

Series 2

UNITY

Thermal desorber

A universal TD platform for tagged and
untagged tubes

Series 2

UNITY

Thermal Desorption – GC(MS)

Thermal desorption (TD) is a highly versatile, sensitive
and labour-saving sample preparation technique for the
measurement of volatile and semi-volatile organic
compounds (VOC and SVOC) in air and materials. It
provides the ultimate sample introduction technology
for GC/GCMS combining selective concentration
enhancement with direct extraction into the carrier gas
and efficient transfer/injection all in one fully
automated and labour saving package.

TD is applicable to GC-compatible organics ranging in
volatility from acetylene and freons to high boilers such
as n-C

40

, phthalate plasticisers and benzo-α-pyrene. It
also offers quantitative concentration for some
inorganic gases including; nitrous oxide, SF6, CS2and
H2S. Key applications include:

• Environmental and workplace air monitoring

• Civil defence and forensic analysis

• Materials and materials emissions testing

• Food, flavour and fragrance profiling

Many material samples, such as polymers, paints,
drugs, foods, textiles, etc. can be directly thermally
desorbed. Weighed samples are heated in a stream of
carrier gas allowing volatiles to be extracted into the
gas flow, refocused and injected into the GC(MS)
analyser as a discreet, concentrated band of vapour.

Alternatively, vapours in gas or air can be concentrated
on- or off-line onto sorbent traps/tubes before TD­GCMS analysis. Several hundred litres of air or gas can
be sampled and the vapours transferred/injected into
the analyser in as little as 200 µl of carrier gas.
Concentration factors as high as 10

6

can be obtained.

Thermal desorption is now recognised as the technique
of choice for air monitoring (workplace and
environmental) and is the subject of many
international standard methods. Key examples include:
EN ISO 16017, ISO 16000-6, EN 14662 (parts 1 & 4),
ASTM D6196, US EPA TO-15 (canisters) & TO-17
(tubes), NIOSH 2549, UK Environment Agency
guidance on landfill gas (LFGH 04) and US EPA
guidance for on-line ozone precursor monitoring.
Markes TD systems offer full compliance with all these
standards.

Thermal desorption offers significant advantages
versus solvent extraction (SE). Key benefits include:
Typically 1000-fold enhancement in sensitivity, greatly
enhanced recovery (>95% vs. 30-80 % with SE), re­usable sample tubes, no toxic solvent required and
reduced analytical interference.

UNITY 2 Main Features

• Provides a single platform for all TD applications - labile species, semi-volatiles (up to n-C40), ultra­volatiles (including C2H2and freons), trace levels (ppt) and high concentrations (ppm/%).

• R

epeat analysis

via SecureTD-Q

™:

Overcomes the one shot limitation of conventional TD systems.

• Cryogen-free operation: Electrically-cooled, sorbent trapping to -30°C eliminates ice plug formation and
reduces running costs.

• Compatible with 3.5-inch x ¼-inch OD sample tubes, with or without electronic tags. UNITY 2 allows an
individual TubeTAG™ to remain with a specific sample tube throughout its life, recording tube history and
facilitating sample tracking between field and laboratory.

• Fully method compliant including stringent leak testing without heat or gas flow applied.

• Fully upgradeable to multi-tube, multi-canister and/or on-line automation. Can also be coupled with
headspace for even greater sample flexibility.

• Time saving ov

erlap mode allows desorption of a subsequent sample to begin while GC analysis of a

previous sample continues.

• Plug-and-play TD: UNITY 2 adds to any commercial GC(MS) and is designed for easy maintenance.

utomated internal standard introduction onto

Thermal Desorption (TD)

• A
blank as well as sampled tubes.

Innovators

• Electrically-cooled sorbent trapping with uniquely-

For over a decade Markes International has pioneered
and commercialised enhancements to analytical
thermal desorption instrumentation and associated
sampling apparatus. The following examples of key
technical advances have all been introduced by Markes
since 1997 and now set the standard for TD
instrumentation:

• SecureTD-Q (quantitative re-collection of split
flow for repeat analysis), which overcomes the
historical one-shot limitation of TD methods and

1

simplifies method/data validation

• Electronic tube tagging (TubeTAG)

.

2

.

• Diffusion locking3(DiffLok™) for enhanced
sample integrity and robust (mechanically simple)
automation.

4

• Patented inert valving

for compatibility with
every TD application on a single analytical
platform – ultra-volatiles, semi-volatiles (up to
n-C40) plus reactive species - mercaptans, CS
gas, etc. – all on one TD system.

fast trap heating rates for splitless capillary GC
operation and optimum sensitivity without risk of
ice formation.

• Off-line conditioning for multiple tubes without
the need to blank-off unused tube connections.

• On-line desorbers with twin, electrically-cooled,
reciprocally-operated focusing traps for truly
continuous air monitoring (TT24-7™).

• Specialist sorbent tubes: Certified reference
standards, SafeLok™ tubes

3

, Silcosteel™ tubes.

• A range of unique sampling tools, several of them

5

patented

, for measuring volatile and semi­volatile organics in challenging matrices:
liquids/solids/emulsions, breath, in-situ soil,
polymers, natural products, construction
products, etc.

1. Patent# GB 2395785 (Automated re-collection using a single TD autosampler), 2. Patent# US 6,446,515 B2, 3. Patent# GB 2337513 US 6,564656 B1

4. Patent# GB 2336649, 5. UK patent application reference 0501928.6 (µ-CTE)

Introducing the UNITY 2
Thermal Desorber

UNITY 2, Markes’ next generation thermal desorption
platform, harnesses this pedigree. It incorporates every
feature required for TD method compliance, every
system innovation of the last ten years and the field­proven reliability characteristic of all Markes TD
instrumentation. Its introduction to the market place
offers a state-of-the-art yet robust range of thermal
desorbers with systems available at prices to suit every
budget.

Building on the field-proven strengths of UNITY,
UNITY 2 combines tube desorption with cryogen-free
analyte re-focusing and efficient back-flush desorption
of the focusing trap. Trap desorption injects analytes
(split or splitless) into the GC capillary column in a
narrow, focused band of vapour and triggers the
GC(MS) run.

The patented, inert heated valve integrated into UNITY
2 facilitates the ambient temperature zero flow leak
testing specified by standard methods and allows
simultaneous analysis of volatile and semi-volatile
compounds. The short, narrow-bore sample flow path
is uniformly heated and optimizes analyte recovery.

SecureTD-Q™ (re-collection of tube and/or trap
desorption split flow) offers quantitative repeat analysis
and is available as standard on every UNITY 2.
SecureTD-Q overcomes the one-shot limitation of older
thermal desorbers.

UNITY 2 provides a method-compliant TD platform that
is ideally suited to meet the ever more stringent
demands of laboratory accreditation, data/method
validation and good laboratory practice. It is operated
using intuitive software loaded onto the same PC as
ChemStation™.

Chromatogram showing simultaneous analysis
of VOC and SVOC with Secure TD-Q repeat
analysis validating recovery across the range

Benzene

Toluene

Dimethyl phthalate

Diethyl phthalate

Hexadecane

Dibutyl phthalate

Diethyl-hexyl phthalate

Di-n-decyl phthalate

Sample

Re-collection &
repeat analysis

One TD platform...

Schematics depicting the flow path of gas during tube desorption (left) and focusing trap desorption (right)

UNITY 2

GC(MS)

UNITY 2

GC(MS)

Trap desorption

Tube desorption

Sample tube

Sample tube

Cold trap Cold trap

Optional split

Optional split

Bypass line

Universal TD platform for all
applications

UNITY is renowned for its application versatility and
UNITY 2 takes this flexibility to another level. With
extended electrical cooling of the entire 60 mm sorbent
bed, the UNITY 2 focusing trap offers quantitative,
cryogen-free retention of ultra volatiles such as freons
and acetylene from larger volumes of air/gas. Markes
offers a range of off-the-shelf pre-packed UNITY 2
traps, each containing up to 4 sorbents. Some of these
are almost universally applicable, others are optimized
for the retention of ultra-volatiles/volatiles (e.g. C
hydrocarbons/freons to n-C12) and still others offer
quantitative retention of target analytes with selective
purging of water or solvents prior to analysis.

2

Tube desorption is now possible at temperatures above
400ºC. Critical sections of the internal flow path have
also been optimized, both for enhanced recovery of
higher boiling ‘sticky’ compounds and quantitative
analysis of reactive components. Example analytes
include: 5/6-ring PAHs, phthalates, PCBs, hydrocarbons
to n-C40, mercaptans, explosives and chemical warfare
agents.

The patented heated valve built into UNITY 2 is
specifically designed for analytical TD. It can be
operated at the low temperatures that are required for
enhanced recovery of labile components and also
allows quantitative recovery of high boilers such as
n-C

.

40

...every application

Quantitative recovery of high boilers (e.g. PCBs, phthalates and PAHs)

Dimethyl phthalate

Diethyl phthalate

Hexadecane

Dibutyl phthalate

Diethyl-hexyl phthalate

Di-n-decyl phthalate

Sample

Re-collection &
repeat analysis

Benzo(a)anthracene

Chrysene

Benzo(b)fluoranthracene

Benzo(k)fluoranthracene

Benzo(a)pyrene

Indeno(1,2,3-cd)pyrene

Dibenzo(a,h)anthracene

Benzo(g,h,i)perylene

Sample

Re-collection &
repeat analysis

Sample

Re-collection &
repeat analysis

PCB standard mixture

(Aroclor 1260)

Phthalate standard mixture

with internal standard

PAH standard mixture

“60 mm sorbent trap length, combined with -30°C cooling, uniquely fast trap

heating and patented TD valving ensure UNITY 2 offers optimum performance

for the widest possible TD application range”

Sample tube desorption

Easy-change focusing trap

Split filter/re-collection tube

Enhanced user accessibility

Simplifying routine maintenance operations has been a
key focus during UNITY 2 development. Changing the
focusing trap, for example, is a simple user-enabled
process. No tightening or loosening of fittings is
required and a new easy-grip collar at the non­sampling end of each trap makes it very easy to
withdraw and replace. Other relevant features include
simple user access to split filters and transfer line
connections. Sealing o-rings have also been selected
both for extended life (typically at least 12 months)
and negligible artifact formation.

Compatible with labile analytes (e.g. explosives,
mercaptans)

DNT

TNT

PETN

RDX

R2 = 0.9997

R

2

= 0.9991

R

2

= 0.9996

R

2

= 0.9769

Ethyl

mercaptan

Benzene

Toluene

Xylene

Mixture of four explosives

Recovery of ethyl mercaptan with flow path at
80°C, re-collection and subsequent re-analysis

Cryogen-free retention of ultra-volatile analytes from

large volumes of air/gas

Sample Volume (mL)

Acetylene Peak Area

y = 0.2953x + 5.2249

R

2 = 0.9999

Sample tracking with

(1) Tag permanently attached to tube &

programmed with tube-related
information using TAG

SCRIBE

(2) Tagged tube sent to field. Sample

start & end information written
to tag via TAG

SCRIBE

(3) Tagged tube returned to lab & data

retrieved using TAG

SCRIBE

. Tagged tube

desorbed using UNITY 2

(4) Tagged tube

ready for re-use

TubeTAG

Error-free tube and sample
tracking

Electronic tube tagging and tracking allows individual
TD sample tubes to be tracked from laboratory to field
and within a laboratory. RFID tags can be programmed
with tube- and sample-specific data such as tube ID
number, type and date of packing, number of thermal
cycles, sampling times/flows and customer reference
number. (More information is given in the TubeTAG
brochure.)

TubeTAG is being heralded as a future standard
requirement for large scale environmental monitoring
projects, industrial hygiene applications, civil defence,
etc. and is particularly important whenever monitoring
data is being linked to human health/comfort or public
safety. UNITY 2 can be used to analyse tagged tubes
(tags do not have to be removed) thus simplifying the
process of tracking tube history and performance.
With TubeTAG compatibility as standard, UNITY 2
ensures a future-proof analytical platform.

UNITY 2 configured for both tube and

Fully upgradeable...fully flexible

Unattended operation for
extended periods

Featuring cryogen-free operation and lower
consumption of supply gases than other brands of TD,
UNITY 2 offers long-term unattended operation. It
needs only 40 ml/min dry gas flow, which equates to
>4 months continuous operation on a standard
cylinder, making it ideal for continuous field
monitoring, for example at remote environmental
stations.

Fully upgradeable: Tubes,
canisters & on-line gas streams

The UNITY 2 series TD range now includes options for
automated sequencing of up to 100 tubes and up to 8
on-line air/gas streams or canister/bags. A single
UNITY 2 platform desorber can be simultaneously
configured for both on-line/canister sequencing and
ULTRA 2 automation for up to 100 sample tubes.

UNITY 2 upgrade options include:

• The Universal Heated Inlet for interfacing
headspace vapours from custom sample
vessels directly to the UNITY 2 focusing trap.

• On-line/canister sequencing. Including 3- or

8-channel options for compliance with key
methods such as continuous monitoring of trace­level ozone precursors (C

2-C10

hy

drocarbons) and

US EPA Method TO-14/15 “Air Toxics”.

• Series 2 U

LTRA 100-tube automation. The

ULTRA is available with built in options for
everything from internal standard addition to
automated sample re-collection.

• Headspace (HS)-TD: connection kits are now
available for connecting UNITY 2 to the Agilent
G1888 automated HS sampler. Combined systems
offer automated HS-trap, full functionality TD
and conventional equilibrium headspace all on
one analytical system.

Simple connectivity

100-tube ULTRA and multi-channel canister/on-line
options are now even easier to connect and disconnect
from UNITY 2 as requirements change; UNITY 2
provides plug-and-play TD.

Please see relevant brochures for further information
on all of these upgrade options.

canister/on-line automation

Productivity & flexibilty

Retention time locking for GC(MS)

Accurate automatic control over split and desorb flows

with MFC options

Rapid cooling of UNITY 2 trap

Time (mins)

Temperature °C

Enhanced electronic control of
gas flows

Optimised productivity

UNITY 2 trap cooling times have been reduced to

minimize cycle times and complement the system’s
expanded automation capabilities. This feature coupled
with overlap mode (whereby a subsequent sample tube
is desorbed while GC analysis of the previous sample is
still ongoing) make UNITY 2 highly time efficient
thereby optimising productivity.

UNITY 2 is compatible with the back pressure regulated
electronic pneumatic control (EPC™) of Agilent
GCs. EPC offers precise control of carrier gas
flow/pressure through the entire TD-GC(MS) system as
part of the GC(MS) programme. This stabilizes
retention times independent of TD analytical conditions
(split flows, sorbents, desorption temperatures, etc.)
ultimately aiding analyte identification. EPC also allows
accurate monitoring and closed-loop control of the
column head pressure, whatever the stage of thermal
desorption operation and whatever the required flow.

Multiple splitting options

Building on UNITY’s compatibility with analyte levels
from sub-ppt to percent, every UNITY 2 offers
unsurpassed split versatility. Users can select from
splitless operation, single split (split open during either
tube or trap desorption) or double split (split open
during both tube and trap desorption.)

Every UNITY 2 features SecureTD-Q quantitative re­collection of all split flow, for repeat analysis and
method/data validation (see overleaf and separate
brochure.)

C

14

C

16

C

18

C

20

C

24

C

28

C

32

C

36

C

40

99% recovery of C40validated using SecureTD-Q

Negligible carry-over (0.03%)

following analysis of 1.3 mg toluene

Automatic control over split flows

Standard UNITY 2 systems feature the full range of
split options (splitless, single split and double split),
but with manually controlled flow rates. Electronic
control of split and desorb flows is offered by 1 or 2
optional mass flow controllers (MFC) integrated
into UNITY 2. These provide versatile electronic
control of both split and desorption flows, featuring
flexible split flow rate selection combined with precise
control at low flows. The UNITY 2 MFC modules also
facilitate flow rate recall during an automated sequence
with multiple TD methods.

Negligible carryover

With less than 0.01% carryover, UNITY 2 facilitates
automated multi-method analysis. High level samples,
such as stack gases or residual solvents, can be
included in the same automated sequence as sub-ppb
environmental air monitoring samples if required.

Building on the strengths of
UNITY

In addition to the enhancements described above,
UNITY 2 has drawn key strengths from its eminent
predecessor. Key features pioneered on UNITY and now
available on UNITY 2 include:

SecureTD-Q

• Repeat analysis: SecureTD-Q (i.e. quantitative

re-collection of any and all split flow during both
tube and trap desorption) was pioneered by
Markes International in 1998. Each sample is re­collected on a conditioned tube (tagged or
untagged) and may be used for repeat analysis,

method/data validation or archiving of
critical samples. SecureTD-Q is available as

standard on every UNITY 2 and overcomes the

one-shot limitation of traditional TD systems

and methods. (For more information see separate
brochure.) No other single tube desorber offers
quantitative recovery of all split flow for repeat
analysis.

Example of splitless desorption of indoor air contaminated with low levels of toluene and benzene

Insert showing good shape for toluene peak

Repeat analysis as standard

Benzene

Toluene

7.2 7.3

GC column: HP5 MS (30m,

0.25mm diameter, 250 µm phase)

Peerless analytical performance

• UNITY 2 provides a universal TD platform for very

volatile, high boiling and reactive compounds at
high and low concentrations.

• Unsurpassed trap heating rates (100°C/sec) and
unique trap heater design offer optimum
desorption efficiency even under low flow (<2
ml/min) splitless conditions. This ensures best

possible detection limits for trace level
compounds.

• Pre-purge of air to vent and flexible water

management options prevent risk of
sorbent/analyte oxidation and minimise

analytical interference.

Ease of use

• Cryogen-free operation for minimal running

costs, optimum up-time and no risk of ice
formation blocking the flow path during
desorption of humid samples.

• Small footprint. At only 16 cm (6-inches) wide,
UNITY 2 occupies minimal bench space.

• Intuitive user interface. Every TD method
parameter is displayed on one easy-to­understand screen minimizing the operator
learning curve.

<3 secs at
half height

Method compliance and system
validation

• Full compliance with key international
standard methods such as EN ISO 16017, ISO

16000-6, ASTM D6196-03, US EPA Method TO­17, NIOSH 2549 and other similar standards.

• Stringent no-flow, ambient temperature leak test
to ensure data integrity. Failed tubes are

preserved intact for operator intervention. Fully
interlinked ready/start signals ensure that trap
desorption only occurs when the rest of the
analytical system is ready for analysis.

UNITY 2 leak test and logged as a sample failure.
In the case of tagged tubes, back-pressure can
be manually recorded on the tag and stored as
part of tube history if required.

Productivity and versatility

• UNITY 2 can be upgraded to automatic tube

desorption and/or automated canister/on-line
analysis and/or headspace-trap.

• Time saving overlap mode: When one sample
is being analysed via GC(MS) another can be leak
tested and desorbed.

• Validation of desorption efficiency/analyte
recovery is simplified using SecureTD-Q (see

above). Use of repeat analysis for TD
method/data validation is described in standard
TD methods such as ASTM D6196.

• Continuous monitoring of carrier gas pressure,
downstream of the sorbent tube and focusing
trap. This pressure reading may be logged for
every sample and for all stages of TD operation

allowing tubes with anomalously high back
pressures to be identified. Moreover, if a tube

is completely blocked this is detected by the

Example international standard methods for

thermal desorption

US EPA Method TO-17: Pumped monitoring of ambient air

EN ISO 16017: Pumped or diffusive sampling of ambient,

indoor and workplace air, plus materials emissions

ASTM D6196: Pumped or diffusive sampling of ambient,

indoor and workplace air plus materials emissions

ISO 16000-6: TD-GCMS/FID analysis of materials emissions

collected using emission test cells or chambers

ASTM F1982: TD-GCMS analysis of compounds of interest for

semi-conductor applications

EN 14662: Benzene in ambient air

Various occupational hygiene-related national standards,

including NIOSH 2549 (US) and MDHS 72/80 (UK)

• System versatility. UNITY 2 is compatible with
any commercial GC(MS). The selective
concentration offered by UNITY 2 allows target
analytes to be quantitatively retained while
unwanted interferents (water, solvents,

etc.) are

purged to vent.

Automated TD requirements for compliance with

standard methods

No flow, ambient temperature leak test

Dry purge/internal standard addition in sampling direction

Pre-purge of air to vent to prevent interference

Inert flow path for compatibility with reactive compounds

like mercaptans

Cryogen-free focusing trap desorbed rapidly in backflush

mode for simultaneous compatibility with very volatile and

semi-volatile analytes

Tubes sealed throughout autosampler operation

Quantitative repeat analysis for method and data

validation (ASTM D6196-03)

Markes International...

Calibration accessory for

TD tubes

Bio-VOC sampler for

collecting alveolar breath

samples & transferring
them to sorbent tubes

TC-20 multi-tube

conditioning/dry purge unit

for up to 20 tubes

Micro-Chamber/Thermal

Extractor (µ-CTE) for measuring

emissions from materials &

consumer products

MTS-32 sequential pumped

sampling onto multiple

tubes

Canisters and related

accessories

Wide range of empty and

prepacked TD sample tubes

TubeTAG RFID tag system

for sorbent tube informatics

VOC-Mole soil probes for

in situ monitoring of

contaminated land

Markes International: Everything for thermal
desorption

UNITY 2 is complemented by the comprehensive portfolio of thermal desorption
instrumentation and associated sampling equipment provided by Markes International.
Many of the innovative and labour-saving accessories available are unique to Markes
including specialist low flow sample tubes, multi-sample test equipment for materials
emissions screening, calibration accessories, breath samplers, soil probes, etc.

TD application guides

A series of TD application guides is available from
Markes International. Titles include:

• Environmental Air Monitoring and Occupational
Health & Safety

• Residual Volatiles & Materials Emissions Testing

• Defence and Forensic

• Food, Flavour, Fragrance & Odour Profiling

Each 16-32 page guide features example TD
applications with key analytical conditions.

Trademarks

SafeLok, DiffLok, TT24-7, SecureTD-Q and TubeTAG are
all trademarks of Markes International Ltd.

EPC and ChemStation are all trademarks of Agilent
Technologies.

Silcosteel is a trademark of Restek Inc., USA

...experts in thermal desorption

Markes International Ltd.

Gwaun Elai Medi Science Campus

T: [phone] F: [phone]

E: [e-mail] W: www.markes.com

Llantrisant

RCT

CF72 8XL

United Kingdom