Excellims
Innovation for Excellence in Detection Technology
Evaluation of using ESI-HPIMS for Surfactants Analysis
HPIMS Systems
Fig. 1 Excellims
GA2100 ESI-HPIMS
with DirectsprayTM
Source.
Excellims’ electrospray ionization high performance ion
mobility spectrometer (ESI-HPIMS) was used to analyze
surfactants with a variety of molecular weights, structures,
and functional groups. In general, surfactant analysis often
poses a challenge for chromatography based separation
systems. HPIMS separates and identifies the surfactants
based on their gas phase ion mobilities and so no
chromatography column and mobile phase are needed.
HPIMS offers outstanding separation efficiency that is
comparable to modern UPLC system, with the added
advantage of separation speed in the millisecond range. The
compounds analyzed in this study were Triton X-100,
Sodium Dodecyl Sulfate (SDS), Linear Alkylbenzenesulfonate
(LAS), and Sodium Lauryl Ether Sulfate (SLES). The rapid
analysis time, low RSD and limits of detection, in-situ
analysis capability, and low operation cost make ESI-HPIMS
an attractive “green” analysis method for many types of
analyses.
Electrospray Ionization High-Performance Ion Mobility
Spectrometry (ESI-HPIMS) is an analytical technique that
separates molecules based on their size and shape.
Molecules in the gas phase are ionized and introduced into
a drift tube with an applied electric field, causing them to
travel through the tube while colliding with neutral drift gas
molecules. At the end of the drift tube the ions are
detected by a faraday cup, and an ion mobility spectrum is
generated that allows for the detection and quantification
of compounds. The entire analysis is completed in a
milliseconds-to-seconds time frame.
Since ESI-HPIMS can complete a single analysis
within milliseconds to seconds and is effective for a
variety of compounds not easily separable by HPLC, it is a
promising technology for many applications. ESI-HPIMS
has demonstrated superior performance to both HPLC
and thermal desorption IMS for isomer separation and
for
the
analysis
of
molecules
that
are
chromatographically sensitive, lack a UV chromophore,
are non-volatile, or are thermally labile. It has been used
to detect traces of illicit drugs and explosive
compounds1,2, in which case portability and rapidity of
the detection are essential factors in choosing an
analytical method. ESI-HPIMS is a green technology that
uses minimal solvent, which makes it both convenient
and cost-effective for analyses in the field. This method
has showed promise for many chemical and
pharmaceutical applications including raw material
identification, content uniformity, dissolution testing,
and cleaning verification/validation. These applications
require a method that is fast, cost effective, sensitive,
and precise.
Sodium Lauryl Ether Sulfate
Fig. 2 Surfactants tested with ESI-HPIMS.
Excellims Corporation, 20 Main Street, Acton MA 01720
Application Note: IMS-2012-01
www.excellims.com
T.978.264.1980
Copyright © 2012 All rights reserved
Excellims
Innovation for Excellence in Detection Technology
Surfactants Study
This research was conducted using Excellims
Corporation’s ESI-HPIMS systems, GA2100 as shown in
Figure 1 and RA4100 (not shown). The system allows liquid
phase samples to be continuously infused into the HPIMS
using an ambient pressure electrospray ionization source,
with minimal or no sample preparation. Methanol, water,
and acetic acid (purchased from Sigma-Aldrich, Haverhill
MA) are HPLC grade solvents used for sample preparation.
The drift gas supply used in these experiments was air,
which was cleaned of contaminants by passing through a
13X molecular sieve (Fluka) trap before entering the IMS
drift tube. The flow rate of the drift gas was approximately
1-3 L/min.
The RA4100 IMS-MS with electrospray ionization was
tuned to provide system resolution in 80-90 range. The
samples were weighed out to make 1 mg/ml stock solutions
and then diluted to 25 ppb to 100 ppm solutions which
were tested in both positive and negative mode. The
instrument conditions were: 8kV, drift tube at 200°C, &
compressed air. The measurements were taken over 30
seconds as the sample was injected at a rate of 3 μl/min.
Surfactants: Triton X-100, Sodium Dodecyl Sulfate (SDS),
Linear Alkylbenzenesulfonate (LAS), Sodium Lauryl Ether
Sulfate (SLES) were chosen as examples for this study
(Chemical structures are shown if Fig. 2). Fig. 3 shows the
ion mobility spectra of surfactant SDS from 25ppb to 25
ppm. Fig. 4 shows the ion mobility spectrum of Triton X-100
at 10 ppm, where baseline separation of the oligomer series
was achieved.
Polymer quantification tools in Excellims VisionTM
software package: In order to quantify each component
in the sample mixture, Vision offers a novel software tool
for extracting and calculating the ratio of each of the
components in the sample mixture. The algorithm
provides indicators that could be used to illustrate the
changes of component ratios. The Fig. 5 spectra show the
overlaid peaks: (A) 1:1 mixture as generated by the
HPIMS and the processed software version(B) LAS HPIMS
generated and software processed(C) SLES IMS
generated and software processed. Note: these spectra
were offset intentionally to enhance the comparison of
the spectra.
Summary
One of the primary advantages for the HPIMS
method is the speed of the HPIMS (in seconds) versus (50
minutes) for the currently used UPLC method for the
same surfactants. In addition to a speed advantage the
HPIMS with Directspray is simple; it can avoid cross
contamination when disposable syringe is used for each
analysis. The technology is greener compared to HPLC,
whereby the method development is minimal and waste
generation is very low since there are no liquid mobile
phases. The analysis speed and low operational cost
make it attractive first method of choice among other
analytical methods. Finally, a novel software tool was
developed to show the potential of being able to identify
the amounts of the surfactants in a mixture.
SDS
Background ions
25 ppm
250 ppb
25 ppb
Fig. 3 Directspray HPIMS analysis of surfactant SDS in
the range of 25ppb to 25 ppm range.
Excellims Corporation, 20 Main Street, Acton MA 01720
Application Note: IMS-2012-01
Fig. 4 Directspray HPIMS analysis of surfactant Triton X100 at 10 ppm.
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Excellims
Innovation for Excellence in Detection Technology
(A)
(B)
(C)
Fig. 5 Directspray HPIMS analysis of surfactant SLES and LAS mixture shown in (A) (B) and (C) shows ion mobility spectra
of LAS and SLES that are analyzed individually (orange) and ion mobility spectra generated by the Vision software (blue)
extracted from mixture spectrum (A) (orange).
References
1
H. H. Hill, Jr., Talanta, 50(6), 1291-1298, 2000.
M. Tam and H. H. Hill, Jr., Anal. Chem., 76 (10) 27412747 2004.
2
Excellims Corporation, 20 Main Street, Acton MA 01720
Application Note: IMS-2012-01
www.excellims.com
T.978.264.1980
Copyright © 2012 All rights reserved