July 8, 2014

1

Fred Fryer

Agilent Technologies

Use of an ICP-MS for direct analysis of multiple elements in a sample matrix > 0.4% dissolved solids using uHMI

Challenges of measuring samples

Weakly acidified water is our ideal and difference in response

compared to the ideal is undesirable or needs to be

compensated for.

Differences observed are:

Element signal suppression or enhancement (per sample)

Longer term upward or downward change in signal (drift).

The change is seen once the dissolved solid content of a

sample excedes 0.2% w/v and can have a few causes.

July 8, 2014

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Effects of the sample matrix

Sample density, surface tension, viscosity affects nebulisation

Intractable material deposits on the cooler interface and changes the performance of the vacuum interface (cones) and is seen as drift.

The major element composition in the plasma affects degree of ionisation eg: sodium suppresses, carbon enhances, at about 0.5% or more.

The composition of the ion beam affects mass balance due to space charge.

Nebulization Desolvation Vaporization, Atomization, Ionization

cones

The Sample Matrix – typical seawater

Element Atomic Weight 1st Ionization

Potential

Concentration

(mg/L)

Sodium (Na) 22.9898 5.138 10,800

Chlorine (Cl) 35.453 13.01 19,400

Magnesuim (Mg) 24.312 7.644 1,290

Sulfur(S) 32.064 10.357 904

Potassium (K) 39.102 4.339 392

Calcium (Ca) 40.08 6.111 411

Bromine (Br) 79.909 11.84 67.3

Agilent and ICP-MS

August 2007

Causes Ionization suppression

Forms polyatomic interferences

False response due to polyatomic molecules are greater

with heavier matrix.

Seawater

Agilent and ICP-MS

August 2007

0

20

40

60

80

100

120

140

Cal Blank

Cal Blank

0..25 /

25

5 / 500

100 / 10000

Blank

1000 ppm

Na C

heck

ICSAB

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

CCBCCB

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppbCCV

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

CCBCCB

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppbCCV

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

CCBCCB

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppbCCV

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

SeaWate

r 10:1

CCBCCB

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppb

SeaWate

r 10:1

+ 1

ppbCCV

CCBCCB

Li / 6 [#3]

Sc / 45 [#1]

Sc / 45 [#2]

Sc / 45 [#3]

Ge / 72 [#1]

Ge / 72 [#2]

Ge / 72 [#3]

In / 115 [#3]

Tb / 159 [#3]

Bi / 209 [#3]

1/10 Seawater replicates (n=10)

Initial calibration

CCVs and CCBs

Approximately 10% upward drift in sensitivity over 14 hours of continuous analysis of 1/10 seawater

The suppression and drift

is caused by the amount

of sample matrix –

dilution puts less sample

matrix into the ICP-MS,

giving tolerance

Undiluted

Seawater

Many challenges- How can these be

addressed?

Robustness > Design the sample introduction such that the sample

change doesn’t have such an impact

High solids nebuliser, low flow sample introduction system, wide torch

injector diammeter, High RF power, long residence time in the plasma.

Use a collision cell capable of dealing with the polatomic molecules

Helium collision for single quad or QqQ reaction

Dilution > Reduce the matrix back to the ideal (< 0.2% tds)

Challenges of Measuring High TDS samples

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Dilution

Offline

• LOR is increased by dilution factor

Online

• Solution based dilution online has a few limitations

• Slow

• Varies with varying matrix, if using peripumps the dilution ratio changes

over time

Aerosol dilution

The nebuliser aerosol is reduced but the total gas flow to

the plasma is maintained - aerosol is diluted into argon

High Matrix Introduction system

Aerosol dilution

Normal sample uptake rate ~0.4 mL min-1

Sample aerosol is diluted by addition of gas after the spray chamber

August 2007

Agilent and ICP-MS

Makeup (Dilution) gas in

to torch

to drain

Carrier gas in

Carrier gas – 0.23 L min-1

Makeup gas – 0.72 L min-1

Total gas flow = 0.95 L min-1

Combining aerosol suppression and ion diffusion -highly robust conditions -excellent stability for undiluted seawater

long-term stability for undiluted seawater (50ppb/5ppm spiked)

(repeated measurements of seawater for 15 hours)

0.5

0.7

0.9

1.1

1.3

1.5

0 50 100 150

measurement #

raw

co

un

ts (

no

rmali

zed

)

9 Be (He) 25Mg (He) 27Al (He)

39K (He) 43Ca (H2) 44Ca (H2)

51V (He) 52Cr (He) 55Mn (H2)

56Fe (H2) 58Ni (He) 59Co (He)

60Ni (He) 63Cu (He) 65Cu (He)

66Zn (He) 75As (He) 78Se(H2)

88Sr (He) 88Sr (H2) 95Mo (He)

107Ag (He) 111Cd (He) 114Cd (114)

121Sb (He) 137Ba (He) 208Pb (He)

232Th (He) 238U (He)

August 2007

Agilent and ICP-MS

New revision HMI = uHMI (Ultra HMI) • Increased dilution range to x100 – even higher

matrix capability

• Less matrix loading to interface, so better long-term

stability

• uHMI maintains high carrier gas flow through spray

chamber, so faster gas replacement and washout

Carrier gas flow

(L/min)

Total

gas flow

7700

HMI

7900

UHMI

HMI-4

(HMI-L)

0.6 0.8 0.95

HMI-8

(HMI-M)

0.35 0.68 0.95

HMI-25

(HMI-H)

0.23 0.5 0.95

HMI-50 N.A. 0.4 0.95

HMI-100 N.A. 0.33 0.95

UHMI

Dilution

Port

Other sample introduction considerations

Agilent Ar gas humidifier

• Assists when measuring high salt

solutions

• Uses a hollow fiber membrane tubing

to “wet” the aerosol

• Helps to reduce salt build-up in the

interface and at the nebuliser tip.

• 2 channels in one body for Carrier gas

and Dilution gas

Brine Analysis: Chemicals and Samples

Actual samples of nearly saturated salt water are not easy to

obtain.

In this experiment, artificial salt water was prepared from

commercial table salts. 30g of pure sodium chloride (Kanto

Chemicals, Japan) dissolved in 100g of UPW was used for

preliminary experiment (23%).

Calibration standards were prepared by spiking to this solution.

Samples for analysis were purchased in Japan and USA

Brine Analysis: Results and Discussion

The recovery rates were calculated by spiking to the actual salt

water with various concentration. Very good recoveries could

be obtained over a wide (20-250 ppb) concentration range.

Fig 2: Spiked concentrations Fig. 3. Recovery rates

Detection limits

• Detection limits were calculated from 3

standard deviations of calibration

blank counts from the mean. (3 sigma

DL)

• Internal standard was added online so

the counts are normalised to internal

standard signal.

7Li 0.064 65Cu 0.02 111Cd 0.015 26Mg 0.22 66Zn 0.033 118Sn 0.014

27Al 0.056 69Ga 0.003 121Sb 0.0052 34S 1020 75As 0.019 125Te 0.053 39K 1.9 78Se 0.034 127I 0.054

44Ca 0.73 79Br 5.6 133Cs 0.0017

48Ti 0.019 85Rb 0.012 138Ba 0.0016

51V 0.0065 88Sr 0.013 182W 0.0031

52Cr 0.027 90Zr 0.0048 197Au 0.0066

55Mn 0.013 95Mo 0.0043 202Hg 0.023

56Fe 0.064 107Ag 0.097 208Pb 0.0026

Table 3. Detection Limits in ppb (ug/L)

Long term stability test

• The long term stability of analyte concentration was examined by using

one of the salt sample solutions

• The stability graphs show that ISTD works very well.

• There was no need to clean the lenses after analysis

60%

70%

80%

90%

100%

110%

120%

130%

140%

0:00:00 1:00:00 2:00:00 3:00:00 4:00:00 5:00:01

No

rmal

ize

d c

on

cen

trat

ion

of

anal

yte

Elapsed time

7Li/6Li Nogas 26Mg/45Sc H239K/45Sc H2 44Ca/45Sc H248Ti/45Sc HEHe 55Mn/45Sc H265Cu/45Sc He 79Br/115In H279Br/115In HEHe 85Rb/103Rh He88Sr/103Rh HEHe 133Cs/159Tb Nogas138Ba/159Tb HEHe 208Pb/209Bi He

Fig. 4: 5 hours stability

Analysis of various type of table salts

• Salt samples #1-15: Sea or Rock salt from Japan, Mexico, Germany, South Africa, USA,

Pakistan, Mongolia

• Covers concentration range from <0.01 ppb to >1,000 ppm in Brine.

Mg Ca K

Ga Cs W

Zr

S

Excellent detection capability with He collision

Spectral interference from the major component (Cl) of salt

water was almost completely eliminated by He mode.

51V (ClO interference) and 75As (ArCl interference) were

detected at low concentrations in 23% NaCl.

V

BEC: 0.06 ppb

As

BEC: 0.2 ppb

Other productivity tools for the 7900 Integrated Sample Introduction System (ISIS 3)

• Increase the sample thru-put, and

save on Ar costs

• Close-coupled valve – very short

tube length so minimal

stabilization/rinse delay

• Easier tubing setup by color coding

• Piston pump for faster sample

uptake

• 3-way valve to switch between on-

line ISTD or tune solution

ISIS is compatible with Startup auto-

optimization functions and full

autotune

7 port valve

(incl. online

ISTD port)

Piston

pump

3-way

valve

January 2014

NPT SAPK, Agilent Restricted

21

Summary

7900 ICP-MS with UHMI makes it possible to analyze even

saturated salt water.

• Good stability

• Low detection limit

• Wide measurement range from ppt to >1,000 ppm

• Expands ICP-MS into fields where only AAS, ICP-OES or XRF have

previously been available.

• Low sample preparation