Environmental applications of ICP-MS as a high sensitivity ... · Environmental applications of...

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?

armandodurazo@gmail.com