18
LMS Issue 3 | 2014
Chromatography & HPLC
Break Free from Routine Sample Prep
T
he Samplicity® filtration system is
an innovative new technology that
provides a convenient, high throughput
alternative to syringe-tip filters when
preparing samples for chromatography.
This is the f irst vacuum-driven
system designed with the f lexibility
to filter one to eight samples directly
into standard HPLC vials. Just attach
a vacuum pump, load samples with a
standard pipette and flip the lever to
recover particulate-free samples - even
those with high viscosity or particulates
- in seconds.
In addition, the system has a low
hold-up volume, which allows processing of samples as small as 300µl.
The overall trend in chromatography
is to do more with less. More samples,
more complex analyses, more analysis
per sample with less volume, lower
concentrations, in less time, with fast
analytical techniques such as ultrahigh pressure liquid chromatography
(UHPLC).
Even though efficient, high quality
sample preparation is crucial in obtaining reliable data from these ultrasensitive techniques, there have been few
recent advances in sample preparation
technology. As a result, it is often
sample preparation, not analysis that
is the rate-limiting bottleneck in
chromatography.
Applications include sample preparation for dissolution testing, HPLC,
UHPLC, UPLC® and liquid chromatography - mass spectrometry. It
is currently available with 0.2µm or
0.45µm PTFE and PVDF philic Millex
Samplicity filters. The Samplicity® filtration system includes a base, lid, vial
tray, waste tray and tubing. ⚛
A High Performing
UPLC System
W
aters’ Acquity UPLC® I-Class
system is one of the highest
performing UPLC systems, taking
UltraPerformance LC® separations
technolog y to the next level. The
Acquity UPLC I-Class features the
low system dispersion and carr yover. Low dispersion maximises peak
c
apacity, thereby advancing chromatog raphic separations and
optimising the
p e r f o r m a n c e
of any mass
spectrometer.
The I-Class
s y stem e xcels
when analysing
a ny comple x ,
sample-limited
compounds.
These samples
ca n represent
complex separation challenges
requiring an
LC system that
ca n ma x im ise
the benef its of
sub-2µ for faster
throughput and
optimised MS performance.
Minimal system volume is a new key
feature of the UPLC I-Class. Reduced
system volume significantly decreases
dispersion rates for reproducibly higher
resolution and superior peak capacity,
which extends the sensitivity of any
mass spectrometer. Additionally, a
low dispersion footprint allows users
to reduce their separation cycle times
without impact to the separation as
the resolution is maintained even for
ballistic gradients lasting less than
one minute.
It also features flexibility and precise
sampling capabilities. Depending
on their application needs, users can
choose eit her t he
highest precision and
lowest dispersion
fixed-loop sample
manager or the
world’s first low
dispersion variable
volume sa mple
ma n a g er, w it h
a f low-through
needle design
t h a t d el i v e r s
h i gh-p re c i sion
injections,
excellent sample
recovery and low
sample ca r r yover optimising
the performance
for even the most
sensit ive mass
detectors. ⚛
Microsep
Contact: Louis van Huyssteen
Tel: 011-553‑2300
Email: [email protected]
Merck Millipore
Field Marketing Manager: Adele Heath
Tel: 011-372-5129
Email: [email protected]
Cr(III) or Cr(VI)?
T
he determination of chromium in
complex matrices is a notorious
challenge, as interconversions between
species may occur during sample preparation making quantif ication ver y
difficult.
In a recent study, Rahman et al performed speciated isotope dilution mass
spectrometry (SIDMS), as described
in EPA Method 6800 (update V), to
determine chromium species in dietary
supplements. EPA Method 6800 was
implemented with a Metrohm ion chromatograph coupled to an Agilent mass
spectrometer with inductively coupled
plasma (IC-ICP-MS).
Although Cr(III) and Cr(VI) are
chemical forms of the same element,
the effects of the two species on human
health could not be more different.
While Cr(III) is considered an essential
trace metal found in many foods, Cr(VI)
is a known carcinogenic with very strict
limits applying to its presence in foods.
The authors of the study point to the
potential risk to consumers resulting
from the fact that manufacturers of
dietary supplements may not be aware
of or even neglect the effects of possible
interconversions of chromium species on
the quality of the final products.
The authors continue to present in
detail the sample preparation/extraction methods required (EPA Method
3060A, EPA Method 3052) to make
sure that subsequent determination of
chromium species in solid samples is
both accurate and reliable. The conclusion from the study is that ‘SIDMS
[as per EPA Method 6800] facilitates
simultaneous accounting of both Cr
species concentrations and correction
for transformations by enabling isotopic
tagging for the oxidation of Cr(III) and
the reduction of Cr(VI) during analysis
in aqueous samples. The combined
extraction/SIDMS procedure is capable
of correcting for bidirectional species
transformations that may occur during
analyses of Cr(VI) in solid samples. ⚛