Semicontinuous determination of anions, cations, and heavy metals
in aerosols using PILS-IC-VA

SummarySample preparation

Semicontinuous aerosol monitoring

The collection of representative aerosol samples and the therewith associatedanalysis are still the most challenging parts in air monitoring. This poster presents
an approach that couples a Particle-Into-Liquid-Sampler (PILS) to a dual-channel
ion chromatograph (IC) for measurement of aerosol anions and cations and avoltammetric measuring stand (VA) to determine the heavy metals. Feasibility ofthe PILS-IC-VA online system was demonstrated by collecting aerosol samples in
Herisau Switzerland, at defined time intervals; air pollution events were simulated
by burning lead- and cadmium-coated sparklers.

The captured air particles, which are sampled through a cyclone that controls thesize of the entering particles applying a size threshold of 10 µm (PM10), enter thecondensation growth chamber, where they are mixed with injected supersaturated
steam. Rapid adiabatic mixing allows the aerosol particles to grow into dropletslarge enough to be collected by an impactor. Afterwards, the solution with thediluted aerosol particles is split into three streams and analyzed by dual-channel
ion chromatography and voltammetry. Since ambient air in Herisau was almost
contaminant-free, sparklers, previously immersed in a 200 g/L lead nitrate and
1 g/L cadmium nitrate solution, were burned near the aspiration tube of the PILS.

To capture the short-term impacts of air pollution, near real-time determination of
the aerosol composition is necessary. After burning a sparkler, time series ofaerosol water-soluble ionic components such as anions, cations, and heavy metalswere determined at a 60 min time resolution during one week.

The PILS-IC-VA setup is straightforward and allows semicontinuous measurementsof water-soluble aerosol ionic components at 60 min intervals. PILS-IC-VA is anindispensable tool to monitor rapid changes in aerosol particle ionic composition,
caused, for example, by brief smoke plume impacts, that would be impossible todetect with filter methods. PILS-IC-VA is an invaluable contribution forinvestigating the composition, transport, and evolution of atmospheric aerosols.
The system is highly suited for long-term unattended field use in remote regions.

Instrumentation
 ADI 2081 Particle-Into-Liquid-Sampler (PILS)
 940 Professional IC Vario TWO/SeS/PP für Anionen- und Kationenbestimmung
 797 VA Computrace

Introduction
Airborne particulate matter has strong impacts on public health and the climate.
Although common filter-based measurements can provide daily particle contributions, they suffer from their poor temporal resolution and their labor-intensive
offline character. Acute exposures that appear only for a very short time get lost in
the long averaging times of the filter.

Aerosol monitoring – single sample
The aerosol sample was collected on 6 February 2011 at 11 a.m.

a) Ion chromatography
Column:Metrosep A Supp 5 - 150/4.0
Column temp.: 30 ˚C
Eluent:
3.2 mmol/L sodium carbonate
1.0 mmol/L sodium hydrogen carbonate
Flow:
0.7 mL/min
Loop:
250 µLPILS air flow: 16.7 L/min ( = 1 m3/h)
Flowsample stream: 0.23 mL/min
Vsample stream:
1.94 mL

Column:Metrosep C 4 - 150/4.0
Column temp.: 30 ˚C
Eluent:
2.0 mmol/L nitric acid
0.7 mmol/L dipicolinic acidFlow:
0.9 mL/min
Loop:
250 µLPILS air flow: 16.7 L/min ( = 1 m3/h)
Flowsample stream: 0.23 mL/min
Vsample stream:
1.94 mLb) Voltammetry
Zinc, cadmium, lead, and copper are determined using anodic stripping
voltammetry (ASV). The metals first undergo cathodic enrichment at the electrodeand are then anodically stripped during the detection phase. Since the oxidation ofthe four metals occur at different potentials, they are determined in a single run.

The automated Particle-into-Liquid-Sampler (PILS), however, offers enhanced timeresolved data by permanently collecting airborne particulate matter. It allows
capturing the particles in an air flow and dissolving the soluble constituents in asteam jet for subsequent analysis. Whilst the hyphenation of PILS with an ion
chromatograph (IC) allows the parallel determination of standard anions andcations, the coupling to a voltammetric measuring stand facilitates detection ofheavy metals.
In this poster, the PILS-IC-VA system is evaluated with respect to its capacity toprovide accurate high-resolution measurements of ambient aerosol samples.
Download a copy of this poster from http://www.metrohm.com/com/Applications (search for 8.000.6086EN).

The time series of the major ionic species determined by PILS-IC-VA clearly show
the impact from sparkler burning and highlight the extraordinary responsiveness of
the analytical unit. The highest spikes belong to nitrate, ammonium, and lead.
Chloride, sulfate, sodium, and potassium still show distinct spikes, while nitrite,calcium, and magnesium as well as the heavy metals, copper and cadmium, werefound at concentrations below 0.3 µg/m3. PILS-IC-VA offers heavy metal detection
limits in the ng/m3 range and thus copes with the specifications stipulated in theEU directive 2004/107/EG.

References(1) R.J. Weber, D.A. Orsini, Y. Daun, Y.-N. Lee, P.J. Klotz, and F. Brechtel, A Particle-Into-LiquidCollector for rapid measurement of aerosol bulk chemical composition, Aerosol Sci.
Technol. 35, 718-727 (2001).
(2) C. Emmenegger, R. Jansen, and M. Laeubli, Determination of anions and cations in aerosols,Pittcon 2008, http://www.metrohm.com/com/Applications (search for 8.000.6014EN).
(3) J. Gandhi and P. Jones, Analysis of airborne particulate matter by PILC-IC, Pittcon 2010,
http://www.metrohm.com/com/Applications (search for 8.000.6058EN).
1Deutsche Metrohm GmbH & Co. KG, D-70794 Filderstadt/Germany, g.bogenschuetz@metrohm.de2Metrohm International Headquarters, CH-9101 Herisau/Switzerland

Ion Chromatography

Voltammetry

G. Bogenschütz1, C. Emmenegger2, and M. Kalcher2