the Auto integration feature, integration times were manually set to 2
seconds for each analyte wavelength in order to maintainconsistency
for all sample introduction systems tested. A multielement test
solution containing 0.5ppm Cu and Mn, and 1ppm As, Se, Mg, Na
and K was used. Each sample introduction system was evaluated
based on the measured sensitivity, signal-to-root background ratio
(SRBR), and precision. For sensitivity and SRBR calculations, net
signal counts per ppm was used. Precision of the net signals were
estimated by analyzing the multielement test solution 10 times as
samples and calculating the average % RSD.
The Glass Expansion inert sample introduction system consisted of
the DuraMist DC nebulizer and PTFE Twister cyclonic spray chamber.
The Glass Expansion sample introduction system was compared
to a CrossFlow nebulizer paired with a PPS Scott-type spray
chamber and a NCPN paired with a PPS Scott-type spray chamber.
The NCPN was operated at the recommend liquid flow rate of 1.4mL/
min, whereas the DuraMist and CrossFlow nebulizers where run at
0.7mL/min. Although a range of nebulizer gas flows were examined,
in order to simplify the data comparison, the results presented were
collected at a nebulizer gas flow rate of 0.7 /min.
Figure 5 depicts the sensitivity obtained with the NCPN paired with
the PPS Scott-type and CrossFlow paired with the Scott-type, relative
to the sensitivity of the DuraMist DC nebulizer paired with the PTFE
Twister. The combination of the DuraMist and PTFE Twister provides
an increase in sensitivity by 50% or more for all elements examined.
Figure 5. Sensitivity of NCPN with Scott-type and CrossFlow with Scott-type relative to DuraMist and
PTFE Twister (relative sensitivity = 1)
Relative sensitivity 0
NCPN Scott CrossFlow Scott
The best indicator of analytical detectability for ICP-OES using a
solid-state detector , is determined by measuring the SRBR. Similar
to what was observed when comparing sensitivity, the DuraMist DC
nebulizer and PTFE Twister spray chamber provided close to a 50%
improvement in SRBR when compared to the other two inert sample
introduction systems, as shown in Figure 6 (Next page).
The final merit of performance examined was short-term analytical
precision. The precision results (Figure 7 Next page) also indicate
that the DuraMist DC nebulizer and PTFE Twister provide superior
%RSD, well below 1.0%.
The DuraMist nebulizer (Figure 4), released by Glass Expansion in
2011,3 is a concentric, self-aspirating inert nebulizer that consists of a
PEEK body and PEEK capillary insert. At the time of its release, the
DuraMist was compared to Glass Expansion’s SeaSpray, OpalMist,
and a non-Glass Expansion NCPN. Characteristics studied included
sensitivity, precision, stability, robustness and tolerance to high TDS
(total dissolved solids).3 In this report the DuraMist nebulizer had
only slightly lower sensitivity than the SeaSpray and outperformed
the NCPN in both precision and sensitivity.
Figure 4. DuraMist DC nebulizer with PerkinElmer Avio gas fitting
The goal of this new study is to examine the performance of Glass
Expansion’s PTFE Twister cyclonic spray chamber and DuraMist
concentric nebulizer for those ICP laboratories that require the
utmost sensitivity and precision in an inert sample introduction kit.
A Perkin Elmer Avio 200 sequential ICP-OES was used for this work;
the experimental conditions are listed in Table 1. Without relying on
Table 1. Experimental conditions
Experimental Parameter Setting
RF power 1.2 kW
Nebulizer gas flow rate 0.7 L/min
Plasma gas flow rate 12.0 L/min
Auxiliary gas flow rate 1.0 L/min
Read time 2 sec
Viewing mode Axial
Pump speed 0.7mL/min & 1.4mL/min
Pump tubing Black-Black, 0.76 mm ID
Torch Fully ceramic D-Torch
www.geicp.com Glass Expansion Newsletter | Issue 46 3