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ICPMS Metals Analysis

 

Introduction

ICPMS is a relatively new technique for the determination of trace elements in solution. It offers better sensitivity than graphite furnace AA with the multi-element speed of ICPOES. In comparison to ICPOES, the mass spectra are much simpler than the optical emission spectra (Figure 1). Most heavy elements exhibit hundreds of emission lines, but they have only 1-10 natural isotopes in the mass spectrum.

We offer Inductively Coupled Plasma - Mass Spectrometry (ICPMS) providing better sensitivity than graphite furnace AA (GFAA) with the multi-element speed of ICP-optical emission spectroscopy (ICPOES).

The Plasma

ICP-MS Plasma

Each analytical technique has its share of problems, interferences, and advantages. AA suffers from severe matrix effects requiring the addition of matrix modifiers and the use of the method of standard additions to quantitate some elements. ICPOES suffers from many overlapping spectral interferences from other elements and a very high background emission from the plasma itself, limiting detection limits. While interferences are common in ICPMS, they are generally easy to detect and handle. All elements except indium have at least one isotope with a unique mass.  Molecular species which are produced in the plasma are usually a bigger problem than elemental interferences. These can be controlled in three ways: (1) keeping the solution concentration of the problem species low, (2) properly adjusting the instrument to minimize the creation of the molecular species in the plasma, and (3) using collision and reaction cell technology to minimize the interferences. In addition, signals can be either enhanced or suppressed by high solution concentrations. Internal standards are used to monitor these conditions and correct for minor instrument response drifts.

ICPMS Operation

In a typical application, metals are placed in solution by acid digestion. The solution is sprayed into flowing argon and passed into a torch which is inductively heated to approximately 10,000oC. At this temperature, the gas and almost everything in it is atomized and ionized, forming a plasma which provides a rich source of both excited and ionized atoms. In ICPMS,  positive ions in the plasma are focused down a quadrapole mass spectrometer. By acquiring the mass spectrum of the plasma, data can be obtained for almost the entire periodic table in just minutes with detection limits below 0.1 ug/L for most elements. The figure below is a photo of our new Agilent 7500cx.  For other photos and more information, take the Photo Tour.

Reaction and Collision Cells

Our instruments are equipped with the latest in reaction cell and collision cell technology.  The Agilent 7500cx systems are equipped with dual reaction/collision cells.  The schematic below shows the reaction cell in action.  Collision of the reaction gas with polyatomic ions from the plasma neutralizes the interference.

Using He as a collision gas is almost a panacea.  This allows the broadest range of elements to be analyzed with the least amount of interference.

For more information click on ICPMS-Cells or Cr by ICPMS-Cell.

 

Agilent 7500cx ICPMS

Agilent ICPMS

Reaction/Collision Cell

Applications of ICPMS

There are many routine applications which parallel AA and ICPOES applications, but because of the characteristics of ICP-MS, it has many unique applications. Because of its superior sensitivity, ICP-MS should be the method of choice for most determinations of trace elements. Many applications have been reported in the medical and safety fields. Pharmaceutical manufacturers have used it to test for trace elements in very expensive drugs as ICP-MS requires little sample to reach the levels of traditional methods.

 

Due to the simplicity of data, the entire mass spectrum of the plasma can be recorded from mass 6 to mass 250 in a single analysis. This can be used to quantitate practically the entire periodic table except the gaseous elements and carbon. For health and safety professionals, unknown or unexpected elements can be identified and quantitated. For manufacturers of reagents, almost all trace metallic impurities can be determined. Exotic elements can be determined without additional equipment. Click here for more information on screening samples for trace metals contamination.

More than 60 Elements

Sample: Acid Leachate

Metals Screen Report

Inductively Coupled Plasma - Mass Spectrometry

ppb

Detection Limit

ppb

Detection Limit

Aluminum

1660

0.7

Molybdenum 

ND

0.1

Antimony

0.9

0.1

Neodymium

2

0.1

Arsenic

ND

0.1

Nickel

ND

0.3

Barium

19

0.1

Niobium

0.5

0.1

Beryllium

0.2

0.1

Osmium

ND

0.1

Bismuth

ND

0.1

Palladium

ND

0.1

Boron

ND

3

Phosphorus ND

5

Bromine

ND

50

Platinum

ND

0.1

Cadmium

ND

0.1

Potassium ND

10

Calcium

9100

100

Praseodymium

0.4

0.1

Cerium

3

0.1

Rhenium

ND

0.1

Cesium

ND

0.1

Rhodium

ND

0.1

Chromium

ND

1

Rubidium

0.8

0.1

Cobalt

ND

0.1

Ruthenium

ND

0.1

Copper

0.8

0.2

Samarium

0.3

0.1

Dysprosium

0.3

0.1

Selenium

ND

1

Erbium

ND

0.1

Silver

ND

0.1

Europium

ND

0.1

Sodium

230

3

Gadolinium

0.3

0.1

Strontium

18

0.1

Gallium

0.6

0.1

Tantalum

ND

0.1

Germanium

ND

0.1

Tellurium

ND

0.1

Gold

ND

0.1

Thallium

0.8

0.1

Hafnium

ND

0.1

Thorium

ND

0.1

Holmium

ND

0.1

Thulium

ND

0.1

Iodine

ND

0.1

Tin

ND

0.4

Iridium

ND

0.1

Titanium

6

0.2

Iron

ND

50

Tungsten

ND

0.1

Lanthanum

2

0.1

Uranium

0.3

0.1

Lead

1

0.1

Vanadium

0.9

0.2

Lithium

1

0.1

Ytterbium

ND

0.1

Lutetium

ND

2

Yttrium

2

0.1

Magnesium

1400

0.4

Zinc

10

0.2

Manganese

120

0.1

Zirconium

3

0.1

Mercury

ND

0.1

     

Date Analyzed: 2-18-97
Elements Not Analyzed: All Gasses, C, S, Si, Sc, In, Tb

>40 of the more common elements fully quantitated (elements in blue)

others estimated +50% but can also be quantitated on request

Detection Limits will depend on sample preparation

Detection Limits based on blanks

 

Includes Uncommon Elements

Isotope dilution techniques for lead provide very accurate results

 

 

Elements not included: Sc, In, Tb used as internal standards

In the environmental field,  it can perform routine analysis of water, soil, air, etc. (EPA Methods 200.8 & 6020).  By adding known amounts of isotopically enriched standards, some elements can be quantitated by isotope dilution, one of the most accurate methods.

For a quotation......

Additional ICPMS publications by WCAS:

ICPMS vs.GFAA, ICPMS Metals Screens, Lead (Pb) by Isotope Dilution ICPMS, and "Environmental Analysis Using ICP-MS", Environmental Laboratory, August/September 1993, pg. 44-49. "ICP-MS for the Analysis of Metals on Membrane Filters", American Industrial Hygiene Association Journal, 48(2), pg. 977-979, (1987).

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