LMS Issue 6; 2013 | Página 24

24?

LMS? Issue 6 | 2013

Pollution Monitoring

Selected Ion Recording with PerkinElmer

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aboratories monitoring trace-level
pesticides and herbicides by gas
chromatography/mass spectrometry
(GC/MS) frequently utilise selected ion
recording (SIR) techniques to maximise
analytical sensitivity for quantification.
With analytical standards, precision is

limited, only by the autosampler and other
instrumental effects.
However, real-world samples pose
a greater challenge. In this latter case,
matrix effects have a detrimental effect on
both sensitivity and precision. Often, such
analyses are carried out using on-column

Figure 1. SIR chromatogram of herbicides in water.

injection. The practical disadvantages
of on-column injection usually manifest
themselves in the form of degraded separation and peak tailing, as the retention
gap rapidly becomes contaminated with
matrix components. Chromatographic
performance may be restored by cleaning
or replacement of the retention gap, but
this is time consuming. In programmed
splitless injection, the sample is introduced into a cool injector liner packed
with quartz or silanised glass wool. The
packed liner has a much greater sample
capacity than the retention gap used in
on-column injection methods. After
injection, the temperature of the injector
is rapidly heated to transfer the analytes
to the head of the chromatographic
column. This approach exposes the sample
to substantially milder conditions than
the flash vaporisation used in classical
splitless injection. It eliminates possible
decomposition caused by contact of the
analytes with a heated metal syringe.

The same experimental setup may also
be used for large-volume injection with
solvent purging.
In the following example, a spiked
(50ppb) river water extract has been
analysed 12 times using programmable
splitless injection. A typical SIR chromatogram is shown in Figure 1. These
12 replicate injections were made after
some 40-50 previous injections into the
same liner. Some of these earlier injections involved large-volume injection
techniques. Despite this, the precision
data show no trends and the quality of the
chromatographic separation is unchanged
throughout the test. ?

• DIN 38406, Part 16: Determination of
zinc, cadmium, lead, copper, thallium,
nickel and cobalt by voltammetry
• DIN 38406, Part 17: Determination
of uranium using adsorptive stripping

voltammetry in surface water, raw
water and drinking water.
UV digestion is suitable for transparent
samples with low-to-medium organic
contamination. UV digestion is used
in the processing of all types of water
samples, for example surface waters or
wastewaters. Liquid biological samples
or foods can also be digested using an
adapted procedure. ?

PerkinElmer
Contact: Chris de Jager
Tel: [phone]
Email: [e-mail]

Get Rid of Organic Matter Fast

M

etrohm presents the 909 UV
Digester, a new digestion unit for
sample preparation by UV photolysis. The
909 UV Digester enables simultaneous
digestion of up to 12 samples and excels
by its robust design and short digestion
times. It is recommended for analysis
where organic matter present in samples
interferes with the determination of heavy
metal analytes.
Digestion of samples in the 909 UV
is fully automatic. The centerpiece of this
device is a UV lamp that provides the
necessary UV radiation. The heat generated by the lamp is dissipated via an aircooling system. To ensure that digestion
takes place under controlled conditions,
a Pt1000 temperature sensor is used to
measure the digestion temperature in a

reference sample. An integral microprocessor controls the digestion temperature
and the digestion time.
Standards that recommend sample
preparation by UV photolysis include:

Metrohm SA
Contact: Ravi Issari
Tel: [phone]
Email: [e-mail]

Lighthouse Handheld Particle Counters

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ighthouse Worldwide Solutions,
a leading supplier of real-time
contamination monitoring systems and
airborne particle counters, offers a range
of advanced handheld particle counters.
These are easy to use with either-single
button or touchscreen operations.
The ergonomically designed and
lightweight Lighthouse handheld particle counters offer six channels of
simultaneous particle counting, ranging
from 0.2-25?m particle size. Their size

and portability make them an ideal tool
for indoor air quality investigations and
environmental monitoring. In addition,
handheld particle counters are useful
for clean room monitoring and testing.
Featuring Mass Concentration Mode
that approximates density in ?g/m3 for
PM2.5 and PM10 testing, the units
display both cumulative and differential
particle count data as well as temperature/relative humidity data on its fast
and easy-to-read colour touchscreen.

Removable
batteries and
optional charger
help to maximise
their portability
and uptime.
Data is easily
downloaded
using t he
Lighthouse
Data Transfer
software.

The units also monitor particulate
levels accurately and reliably, even
in hard-to-reach areas where twohanded operation is unsafe. ?

Microsep
Contact: Frances Renwick
Tel: 011-553?2300
Email: [e-mail]