Page 126 - Inorganic Mass Spectrometry : Fundamentals and Applications

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be a problem. For analyte elements with masses less than about 40 U, chemical
matrix effects are noticeable for concentrations of concomitant species as low as
order
50 ppm. The signal suppression can be severe (more than an of magnitude) if
the sample contains high (1000 ppm) concentrations of heavy elements.
Detection Limits
When using a pneumatic nebulizer, an unheated spray chamber, and quadrupole
a
l part per trillion or less for 40 to
mass spectrometer, ICP-MS detection limits are
60 elements (Table 3.4) in "clean" solutions. Detection limits in the parts per
quadrillion range can be obtained for many elements with higher-efficiency
sample introduction systems andlor a magnetic sector mass spectrometer used in
low-resolution mode. Blank levels, spectral overlaps, and control of sample con-
tamination during preparation, storage, and analysis often prohibit attainment of
the ultimate detection limits.
Attainable detection limits depend on the amount of analyte that enters the
ICP per second, the efficiency of aerosol conversion into analyte ions in the ICP,
and the transmission efficiency of ions from the plasma to the MS detector. 'The
detection limits also depend the variation of the background and the integration
on
time. Typical pneumatic nebulizerlspray chamber systems operated at sample
uptake rates from 0.1 to 2.0 mL/min introduce an amount of analyte equivalent to
that in 10 to 30 pL/min of sample solution into the ICP. At a sample uptake rate of
1 mL/min, only 1% to 2% of the analyte enters the plasma; most of the sample is
lost in the spray chamber and exits through the drain. Concentration based
detection limits can be improved by approximately a factor of 10 by using a high-

Typical Detection Limits Using a Quadrupole Inductively
Coupled Plasma Mass Spectrometer (ICP-MS)a
Less than 1 ppt Less than 5 ppt Less than 50 ppt
Ag Eu Mg Re Th Be Mn Ca
A1 Gd MO Rh TI Cd Ni K
Au Hf Nb Sb Tm CO Rb Se
Ba Ho Nd Sm U Cu Sn
Bi In Pb Sr Y Ga Te
Ce Ir Pr Ta Yb Ge V
CS La Pt Tb W Hg Zn
Dy Lu Os Tc Zr Li
Er
"Parts per trillion (ppt), picograms per milliliter (pg/d).