Environmental applications of ICP-MS as a high sensitivity, element-specific
detector for chromatography
Armando Durazo, Ph. D.
Department of Chemical and Environmental Engineering The University of Arizona
Principles of Operation
• ICP-MS is a mass spectrometer with an Inductively Coupled Argon Plasma as an ion source.
• The high temperature of the plasma converts analytes into singly charged atomic ions.
• Elemental quantitation is accomplished by evaluating the intensities of ions formed.
ICP-MS analysis has many benefits
• Multi-elemental analytical technique
• High sensitivity, ppq/ppt DLs for most elements
• Extremely linear with wide dynamic range
• Minimal number of spectral interferences
• Readily interfaced with chromatographic separations
• Tolerant of non-volatile buffers and detergents
• Elemental response is compound independent
Environmental Applications of ICP-MS
• Iodinated Contrast Media
• Bromide and Bromate
• Volatile Halogenated DBPs
Iodinated Contrast Media
• Administered to patients to improve tissue contrast by either X-ray or CT scans.
• Dosages are typically in the g/L concentration range and are excreted within hours.
Iopromide
• Hydrophilic and non-ionic
• Resistant to sewage treatment processes
• Persistent environmental contaminant
Iopromide Results
• The analysis of samples indicates clearly the presence of other iodinated species in these extracts.
• The iodine contents of these peaks has been quantitated using
compound-independent calibrations.
127I
127I
0.0 ppb
0.1 ppb
Experimental Details
For more details, please read:
“Determination of iopromide in environmental waters by ion chromatography-ICP-MS” (Agilent publications 5991-1044EN and 5991-1352EN)
Bromate
• Bromide is harmless, bromate is carcinogenic.
• Oxidative treatments can convert bromide to bromate.
• Once formed in water, removal of bromate is difficult.
Bromate Results
79Br
35Cl
bromate
chloride
No need for pre-concentration or pre-treatment of samples!
bromide
GC-ICP-MS
• Indeed, interfacing LC/IC with ICP-MS is readily accomplished.
• In addition, a GC can be interfaced with an ICP-MS to perform speciated analysis on volatile analytes.
Advantages of GC-ICP-MS
• No water present → little/no oxide interferences
• No evaporative cooling of plasma → lower RF forward power
• Lower RF power → less Ar-based ions (40Ar+, 38Ar40Ar+, 38Ar40ArH+, etc.)
Interference-free analysis without collision gas.
GC-ICP-MS interface
Heated Injector
GC Torch Plasma Column outflow (He)
Pre-heated Makeup gas (Ar)
Heated Transfer Line
Heated GC Oven
Halogenated DBPs
• Halides are activated under oxidizing conditions.
• Activated halides react with organics to form halogenated DBPs.
• Iodinated DBPs are more toxic than chloro- or bromo- analogues.
Analysis of Halogenated DBPs
• Typically examined by GC-ECD or GC-MS/MS.
• Limited by lack of element specificity (GC-ECD) or ionization & fragmentation issues (GC-MS/MS).
– CI source does not ionize all organics
– EI source can lead to excessive in-source fragmentation
– Incomplete fragmentation in MS/MS
GC-ICP-MS on volatile DBPs
• Element-specific and interference-free
• Wide linear calibration range
• Compound-independent elemental response
• Allows for quantitation of total organic halogens in a sample
Calibration Curves
127I
Effects of Chloramination
127I 81Br
After Chloramine Before Chloramine
S/N = 200!
Effects of Chloramination
Chloramination of these samples causes clear and profound changes to occur:
– Total (volatile) halogen levels increase
– Speciation of halogenated organics changes
Trend towards more volatile I-DBPs
Blank Extract Before ClNH2 After ClNH2
Bromine (ppb) 103 1134 98229
Iodine (ppb) 93 490 777
Experimental Details
For more details, please read:
“An Examination of the Presence, Formation, And Transformation of Volatile Halogenated Organic Species in Wastewater Extracts using GC-ICP-MS” (Application note, in press).
Conclusions
• A number of chromatographic separations are readily interfaced with ICP-MS.
• ICP-MS offers a wide analytical dynamic range and element-specificity.
• ICP-MS opens up new analytical capabilities that other forms of molecular analysis do not.
Acknowledgements
Prof. Shane A. Snyder
Amir Liba
Elizabeth McCarthy
Joe Weitzel
Questions?