ac202834j_si_002.avi (582.12 kB)
Quantitative Analysis of Liquids from Aerosols and Microdrops Using Laser Induced Breakdown Spectroscopy
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posted on 2012-03-06, 00:00 authored by Erica
M. Cahoon, Jose R. AlmirallLaser induced breakdown spectroscopy (LIBS) is shown
to be capable
of low volume (90 pL) quantitative elemental analysis of picogram
amounts of dissolved metals in solutions. Single-pulse and collinear
double-pulse LIBS were investigated using a 532 nm dual head laser
coupled to a spectrometer with an intensified charge coupled device
(CCD) detector. Aerosols were produced using a micronebulizer, conditioned
inside a concentric spray chamber, and released through an injector
tube with a diameter of 1 mm such that a LIBS plasma could be formed
∼2 mm from the exit of the tube. The emissions from both the
aerosols and a single microdrop were then collected with a broadband
high resolution spectrometer. Multielement calibration solutions were
prepared, and continuing calibration verification (CCV) standards
were analyzed for both aerosol and microdrop systems to calculate
the precision, accuracy, and limits of detection for each system.
The calibration curves produced correlation coefficients with R2 values > 0.99 for both systems. The precision,
accuracy, and limit of detection (LOD) determined for aerosol LIBS
were averaged and determined for the emission lines of Sr II (421.55
nm), Mg II (279.80 nm), Ba II (493.41 nm), and Ca II (396.84 nm) to
be ∼3.8% RSD, 3.1% bias, 0.7 μg/mL, respectively. A microdrop
dispenser was used to deliver single drops containing 90 pL into the
space where a LIBS plasma was generated with a focused laser pulse.
In the single drop microdrop LIBS experiment, the analysis of a single
drop, containing a total mass of 45 pg, resulted in a precision of
13% RSD and a bias of 1% for the Al I (394.40 nm) emission line. The
absolute limits of detection of single drop microdrop LIBS for the
emission lines Al I (394.40 nm) and Sr II (421.5 nm) were approximately
1 pg, and Ba II (493.41 nm) produced an absolute detection limit of
approximately 3 pg. Overall, the precision, accuracy, and absolute
LOD determined for single microdrop LIBS resulted in a typical performance
of ∼14% RSD, 6% bias, and 1 pg for the elements Sr II (421.55
nm), Al I(394.40 nm), Mg II (279.80), and Ba II(493.41 nm).