oils analysis by icp-oes using next generation svs-2 ps-ds · analysis by icp-oes using next...

Application forEnergy and Fuels

Improved Throughput for Oils Analysis by ICP-OES Using Next Generation Sample Introduction Technology

Patrick Simmons, Doug Shrader& Phil Lowenstern

Agilent Technologies

1

Application Considerations

Applications

• Biodiesel

• Petroleum diesel and coolant analysis

• Naptha

• Wear metals – High Throughput Analysis

Conclusions

Overview

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The challenge:• High vapour pressure from solvents

– Plasma instability– Extinguished plasma

• Carbon build up on injector– Poor precision and drift– Down time - injector requires regular cleaning

• Nebulizer blockage– Poor precision– Down time - nebulizer needs cleaning

Application Considerations

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The solution:• Carbon build up

– Use radially viewed vertically oriented plasma• Minimizes carbon build-up

– Exhaust positioned directly above plasma, efficiently extracts carbon by-products

– Use oxygen addition into auxiliary gas flow to facilitate removal of carbon and reduce background• Mandatory with axial ICP

• Nebulizer blockage– Use nebulizer with large ID to reduce blockage from particulates

• e.g. SeaSpray, Slurry or V-groove nebulizer– Use new OneNeb nebulizer– Filter samples or allow to settle and sample from the top

• Conikal nebulizer produces finer aerosol

Application Considerations

4

Radial ICP Torches

• Designed specially for organic solvents

• Annealed for greater durability

• Choice of 0.8 and 1.4mm ID. injector– 1.4 mm ID suitable for organic solvents of low to

moderate volatility– 0.8 mm ID suitable for highly volatile organic solvents

One Piece Torches

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Nebulizers

• Sample particulates may block standard concentric nebulizers – Dependent on sample composition

e.g. wear metal particulates– Poor precision– Down time - nebulizer needs cleaning

• Quartz nebulizer– Conikal, Seaspray and Slurry– Faster washout

• V-groove nebulizer– Made of PEEK polymer– Minimizes particulate blockage

V-groove nebulizer

Quartz nebulizer

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For Challenging Applications – OneNeb Nebulizer• Robust PFA and PEEK construction

– Inert - resistant to strong acids such as HF– Resistant to breakage– Molded plastic design provides improved

nebulizer to nebulizer reproducibility• Constant diameter narrow bore tubing

through to nebulizer tip– Ideal for high solids/particulates– Improved tolerance to high TDS samples

• Narrow aerosol size distribution provides improved precision

• Handles a wide flow range from 0.1 to 2 mL/min.– No sensitivity loss at low flow rates

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Tip geometry dimensioned to allow carrier gas to mix with the sample

Turbulent mixing of liquid and gas occurs

• Produces aerosol with a narrow size distribution range

Droplets mixed into gas flow

No area of low pressure

Unique Flow Blurring action increases nebulization efficiency• Greater efficiency than conventional

concentric nebulizer• Improved sensitivity

Principle of Operation – Inert OneNeb Nebulizer

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0

2

4

6

8

10

12

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0 20 40 60 80 100Droplet Size (m)

Prop

ortio

n of

Tot

al

Inert OneNeb nebulizer

Conventional concentric nebulizer

Spray Chambers

• Double-pass glass cyclonic spray chamber – Double pass design– Reduces solvent load– Increased sensitivity– Fast washout– Suitable for low vapour organic solvents

• Cooled spray chamber– Externally jacketed or Peltier cooled designs– Can cool sample to -10 oC or lower– Reduces solvent load– Made of quartz– Excellent for highly volatile organic solvents

e.g. naphtha

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Solvent PVC Viton PVC Solva

Kerosene

Gasoline

Fuel

Coolant N/A

Compatibility of Pump TubingPump Tubing

= unsatisfactory, = satisfactory, N/A = no data available

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The challenge:• Various elements of interest

– May need to calibrate for 30 to 60 different elements

• Unknown concentration of analytes in samples– Down time – to perform multiple dilutions for the same sample

• Difficult interferences to overcome– Poor accuracy

Application Considerations

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Measuring Petroleum Products Successfully

The solution:• Linear dynamic range

– Use wavelength flexibility to extend the upper limit

– Still achieve best detection limits

• Structured backgrounds– Radial ICP-OES– Use patented Fast Automated Curve-

fitting Technique (FACT)

• Speed of analysis– 725 simultaneous CCD system– Fastest possible read out speed

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700 Series Optical DesignEchelle Optical Design

Full wavelength coverage– Maximum flexibility for extended linear working range– Elimination of spectral interferences

All wavelengths captured in one reading– Maximum speed and productivity

Fewer optical components– Excellent signal-to-noise– Lowest detection limits

Thermostatted to 35oC– Excellent long term stability

– Fast start-up, increasing sample throughput

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World’s Most Innovative Detector

• 725 Patented custom-designed CCD• Continuous Wavelength coverage

• 167 – 785 nm• Simultaneous measurement• Very high Quantum Efficiency• Excellent resolution• Lower detection limits• Dual mode anti-blooming capabilities

• Eliminates blooming in both the X and Y direction

• Peltier cooled for lowest noise and best detection limits

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Structured BackgroundIntroduction of organic solvents into the ICP can result in spectral interferences from molecular emission by species such as C2 and CN• Na 589nm in engine oil and diluted in white spirit

Standard – 10 mg/kg NaBlank – 0 mg/kg Na

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Structured Background from Na 589 nm in Oil - Diluted in white spirit

Blank – 0 mg/kg Na

- No Background Correction

Blank – 0 mg/kg Na

– Fitted Background Correction

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Structured Background from Na 589nm in Oil - Diluted in white spirit FACT Corrected

Standard – 10 mg/kgBlank – 0 mg/kg Na

BackgroundSample SpectrumAnalyte

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Structured Background from Na 589nm in Oil - Diluted in white spirit FACT Corrected

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Sample and Standard Preparation

Sample Preparation• Up to 1 in 10 dilution on a weight per

volume basis• Use suitable organic solvent

e.g. xylene, kerosene, Shellsol

Standard Preparation• Multi-element organometallic standard

(e.g. Conostan S-21)• Select dilution ratio to achieve required

concentration• Add extra neutral base oil (No. 75) to

ensure consistent viscosity

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Typical Instrument ConditionsPlasma power 1.3 - 1.5kW

Plasma gas flow 15 – 18 L/min

Auxiliary gas flow 0.75 – 2.25 L/min

(axial – radial)

Nebulizer gas flow (axial) Optimize

(0.5 – 0.8 L/min)

Nebulizer gas flow (radial) Set bullet to top of torch

(0.5 – 0.8 L/min)

AGM-1 setting 2 - 6

Stabilization delay Optimize via time scan

Pump speed 5 - 10 rpm

Uptake Rate < 1 mL/min

Fast Pump Yes or No?

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Important Parameters

Parameters:

• Power 1.3 - 1.5 kW

• Nebulizer flow: optimize using bullet of the plasma

• Viewing height: optimized for SBR

Each can be automatically optimized using AutoMax

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Power = 1.2 kWNebulizer flow = 1.00L/minViewing height = 10mm

Power = 1.5 kWNebulizer flow = 1.70L/minViewing height = 5mm

Why Optimize?

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Performance Test – Linear RangeRadial, S21 Conostan Oil Standards in Kerosene

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SPS-3 = Autosampler for automated sample presentation

AGM-1 =Addition of oxygen to plasma

VGA-77P = for hydride determinations of As, Se & Hg (ppb levels)

ASA = Increases the water vapor in the nebulizer gas

SVS-2 = Increased productivity and more efficient washout

ICP-OES Accessories Overview

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Direct Biodiesel Fuel Analysis

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Why Use Biodiesel?

• Reduced dependence on imported oil products– Direct replacement for conventional

petroleum based diesel fuel– Important alternative fuel source

• Biodiesel is a green fuel– Produced from domestic, renewable

resources– Biodegradable and non-toxic– Reduction in pollutants such as

sulfur and aromatics– 78 % reduction in CO2 emissions

compared with petroleum

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Analytical Results – ASTM D6751 Specified Elements in Biodiesel

Element P S Na K Ca MgWavelength (nm) 213.618 181.972 589.592 766.491 393.366 279.553B‐100a ppm < IDL 1.695 0.162 0.507 0.013 0.011B‐100b ppm < IDL 1.710 0.130 0.469 0.012 0.012B‐100+1.0 ppm (%R) 105 103 104 107 105 104B‐100+2.5 ppm (%R) 102 106 102 104 103 101IDL (ppb) 19.9 76.5 4.1 21.8 0.1 0.1Bkgd Correction Fitted Fitted FACT FACT Fitted Fitted

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Direct Measurement of Petroleum Diesel and Coolant Samples

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Detection Limits – Petroleum Diesel

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Stability – Petroleum Diesel

0

0.2

0.4

0.6

0.8

1

1.2

18:56

:3919

:13:42

19:30

:4419

:47:47

20:04

:5220

:21:56

20:39

:0020

:56:05

21:13

:1021

:30:14

21:47

:2022

:04:25

22:21

:3222

:38:38

22:55

:45

Ag 328.068Al 396.152B 249.772Ba 455.403Ca 396.847Cd 214.439Cr 267.716Cu 327.395Fe 238.204Mg 279.553Mn 257.610Mo 202.032Ni 231.604P 213.618Pb 220.353S 180.669S 181.972S 182.562

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Plasma Stability

Eight hour stability run for elements in oil/kerosene - Conostan S21

0

1

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5

6

7

8

9

10

0:00 1:12 2:24 3:36 4:48 6:00 7:12

Co

nce

ntr

atio

n (p

pm)

Time (Hrs:Min)

8 Hour Stability Run - NO Int. Std.Worksheet S21Stab7.vws

Ag 328.068Al 396.152Ba 455.403Ca 396.847Cd 214.439Cr 267.716Cu 327.395Fe 238.204Mg 279.553Mn 257.610Mo 202.032Na 588.995Na 589.592Ni 231.604P 213.618Pb 220.353Si 251.611Sn 189.927Ti 336.122V 292.401Zn 213.85790 % Limit110 % Limit

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Determination of Trace Elements in Naphtha

Michelle Morin, Natural Resources Canada

Wayne Blonski, Agilent Technologies, Mississauga, Ontario, Canada

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Why Determine Trace Elements in Naphtha?

Naphtha is a liquid intermediate between the light gases in the crude oil and the heavier liquid kerosene and are:• Volatile• Flammable, and• Have a low specific gravity of about 0.7

The presence of trace metals in hydrocarbon samples can:

• Severely hamper the catalytic reforming process

• Poison the catalysts usede.g. S and N compounds candeactivate catalysts Catalysts used in catalytic cracking or reforming

Photo courtesy Phillips Petroleum Company

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Performance Test - Plasma Stability

Short term stability over 30 mins. for Naphtha

3

3.5

4

4.5

5

5.5

6

6.5

7

1 : 1 1 : 2 1 : 3 1 : 4 1 : 5 1 : 6 1 : 7 1 : 8 1 : 9 1 :10

1 :11

1 :12

1 :13

1 :14

1 :15

1 :16

1 :17

1 :18

1 :19

1 :20

No. Samples Measured

Con

cent

ratio

n

Ni 231.604Ni 216.555Mg 279.553V 309.310V 292.401Mg 280.270Al 396.152Ca 396.847Ca 422.673Cd 214.439Cd 226.502Cd 228.802Cr 267.716Cu 324.754Cu 327.395Fe 238.204Fe 259.940Mn 257.610Na 588.995Na 589.592

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Detection Limit Performance (mg/L)

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Wear Metals AnalysisA High Throughput Application

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Elements & Wavelength

(nm)

Results (ppm)

CRM 1084a (ppm)

% Recovery

Ag 328.068 96.3 101.4 95 Al 167.019 105.6 104 102* Cr 267.716 96.9 98.3 99 Cu 327.395 99.1 100 99 Fe 238.204 100.6 98.9 102 Mg 279.553 100.6 99.5 101 Mo 202.032 96.6 100.3 96 Ni 231.604 99.5 99.7 100 Pb 220.353 107.7 101.1 107 S 181.972 2022 1700 119** Si 251.611 100.7 103 98* Sn 189.927 91.5 97.2 94 Ti 336.122 101.3 100.4 101 V 292.401 101.3 100.4 101

* Uncertified results

** Uncertified results, result was high because of kerosene contamination

AccuracyCRM Analysis 1084a Wear metals in lubricating oil

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Plasma Stability

Eight hour stability run for elements in oil/kerosene - Conostan S21

0

1

2

3

4

5

6

7

8

9

10

0:00 1:12 2:24 3:36 4:48 6:00 7:12

Co

nce

ntr

atio

n (p

pm)

Time (Hrs:Min)

8 Hour Stability Run - NO Int. Std.Worksheet S21Stab7.vws

Ag 328.068Al 396.152Ba 455.403Ca 396.847Cd 214.439Cr 267.716Cu 327.395Fe 238.204Mg 279.553Mn 257.610Mo 202.032Na 588.995Na 589.592Ni 231.604P 213.618Pb 220.353Si 251.611Sn 189.927Ti 336.122V 292.401Zn 213.85790 % Limit110 % Limit

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Introduction

In order to predict when equipment maintenance may be required or to prevent having to perform maintenance, lubricating oils in equipment are regularly analyzed to monitor changes in levels of wear-metals, and additive and contaminant elements. The analyst is mainly interested in trending changes over time, not exact values. So high sample throughput could be considered more important than accuracy, precision, long-term stability and repeatability/reproducibility.

In this work, an Agilent 725 Series ICP-OES inductively coupled plasma optical emission spectrometer with Agilent SPS 3 Sample Preparation System and Agilent SVS 2 Switching Valve System was used. The SVS 2 improves efficiency by greatly reducing sample uptake and washout times. The typical ICP-OES sample analysis cycle time was halved (to 33 seconds per sample), significantly reducing operating costs, without compromising accuracy, precision, long-term stability and repeatability/reproducibility.

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Measurement challenge

ChallengeWhile long-term stability and repeatability/reproducibility are important in wear-metal analysis, since analytical results are used only for trend analysis, accuracy becomes a less important factor and sample throughput is often the most critical consideration.

SolutionUsing the Agilent SVS 2 Switching Valve System with an Agilent 725 Series radially-viewed ICP-OES and Agilent SPS 3 Sample Preparation System more than halves the sample analysis cycle time of about 90 seconds without the SVS 2, to about 33 seconds per sample using the SVS 2, without compromising accuracy, precision or stability.

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ExperimentalInstrumentation

• Instrument: Agilent 725 Series simultaneous ICP-OES with radially-viewed plasma.

• Accessories: Agilent SPS 3 Sample Preparation System; Agilent SVS 2 Switching Valve System.

725 ICP-OES

Switching Valve System 2Increase Productivity

• Higher sample throughput

• Decreased wear and tear on nebulizer/spraychamber/torch

• Lower operating cost through reduced argon use

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SVS Productivity Packages How does it work?

Comparison of the sample uptake, measurement and rinse profiles of 100 mg/L manganese without a SVS and the SVS 2. The data shows a dramatic increase in productivity while

maintaining consistent data quality.

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SVS 2 in Sample Inject PositionSVS 2 in Sample Load Position

SVS 2 Switching Valve SystemSecond Generation Switching Valve

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Load Analyze

ExperimentalInstrumentationAgilent 725 Series ICP-OES instrument operating parameters

Note: An all-glass sample introduction system (part number 9910117900) was used.

Condition SettingPower 1.35 kWPlasma gas flow rate 15 L/minAuxiliary gas flow rate 2.25 L/minSpray chamber Glass cyclonic double-pass (Twister)Torch One-piece quartz radial (1.5 mm id injector)Transfer tube GlassNebulizer Glass concentric (SeaSpray)Nebulizer flow rate 0.55 L/minViewing height 9 mmPump tubing Rinse/instrument: Gray/gray SolventFlex (1.30 mm id)

Waste: Purple/black SolventFlex (2.29 mm id)Pump speed 12 rpmTotal sample usage 2 mLReplicate read time 2 sNumber of replicates 3Sample uptake delay 0 sStabilization time 12 sRinse time 0 sFast pump OffBackground correction Fitted

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ExperimentalInstrumentation

Agilent SVS 2 Switching Valve System operating parameters

Note: The internal standard/diluent channel was not used.

Condition SettingLoop uptake delay 7 sUptake pump speed — refill 500 rpmUptake pump speed — inject 150 rpmSample loop size 0.5 mLTime in sample 6 sBubble inject time 6.9 s

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ExperimentalStandard and sample preparation

Calibration solutions of 0, 5, 10, 25 and 50 mg/L were prepared from Conostan S-21 + K certified standard, which contains 22 elements (Ag, Al, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Si, Sn, Ti, V and Zn) at 500 mg/kg in oil. These calibration solutions were viscosity matched using Conostan Element Blank Oil (75 cSt) and diluted with kerosene to give a total oil concentration of 10 % (w/v) in each solution.

Duplicate 0.5 g portions of NIST SRM 1084a (Wear-Metals in Lubricating Oil) and 2 g of Element Base Oil were accurately weighed into 25 mL volumetric flasks and made up to volume with kerosene. A third 0.5 g portion was similarly prepared, spiked with S-21 + K standard.

Duplicate 0.5 g portions of NIST SRM 1085b (Wear-Metals in Lubricating Oil) and 4.5 g of Element Base Oil were accurately weighed into 50 mL volumetric flasks and made up to volume with kerosene.

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Experimental3σ method detection limits (MDLs) & linearity correlation coefficients

Element &wavelength MDL (mg/L)Ag 328.068 0.003Al 308.215 0.018B 249.678 0.011Ba 493.408 0.002Ca 422.673 0.008Cd 228.802 0.005Cr 205.560 0.010Cu 327.395 0.007Fe 259.940 0.004K 766.491 0.081Mg 285.213 0.006Mn 260.568 0.004Mo 204.598 0.015Na 588.995 0.062Ni 230.299 0.018P 177.434 0.069Pb 283.305 0.031Si 251.611 0.101Sn 283.998 0.128Ti 334.941 0.002V 292.401 0.003Zn 213.857 0.015

Element &wavelength r2

Ag 328.068 0.9998Al 308.215 0.9998B 249.678 0.9998Ba 493.408 0.9996Ca 422.673 0.9996Cd 228.802 0.9999Cr 205.560 0.9999Cu 327.395 0.9997Fe 259.940 0.9999K 766.491 0.9996Mg 285.213 0.9998Mn 260.568 0.9998Mo 204.598 0.9999Na 588.995 0.9999Ni 230.299 0.9999P 177.434 0.9999Pb 283.305 0.9997Si 251.611 0.9999Sn 283.998 0.9999Ti 334.941 0.9997V 292.401 0.9999Zn 213.857 0.9999

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ResultsNIST SRM 1084a

Element &wavelength

Certified(mg/kg)

Found(mg/kg)

Duplicate(mg/kg)

Recovery(%)

RPD dup.(%)

Spike level(mg/L)

Recovered(mg/L)

Recovery(%)

Ag 328.068 101.4 100.3 101.1 98.9 0.9 2.17 2.27 104.6Al 308.215 (104) 99.7 100.4 95.9 0.7 2.17 2.27 104.3Cr 205.560 98.3 104.3 105.5 106.1 1.2 2.17 2.27 104.3Cu 327.395 100.0 102.7 103.6 102.7 0.8 2.17 2.27 104.5Fe 259.940 98.9 105.2 105.4 106.4 0.2 2.17 2.25 103.5Mg 285.213 99.5 102.5 102.9 103.0 0.4 2.17 2.28 104.9Mo 204.598 100.3 106.2 106.3 105.9 0.1 2.17 2.28 104.9Ni 230.299 99.7 106.2 107.0 106.5 0.7 2.17 2.28 104.9Pb 283.305 101.1 103.1 105.7 102.0 2.5 2.17 2.30 105.9Si 251.611 (103) 100.2 100.4 97.3 0.2 2.17 2.31 106.1Sn 283.998 97.2 105.8 105.6 108.8 0.2 2.17 2.31 106.3Ti 334.941 100.4 105.2 105.2 104.8 0.0 2.17 2.27 104.5V 292.401 95.9 105.4 105.9 109.9 0.4 2.17 2.30 106.0

Wear-metals in lubricating oil – sample source NIST US Department of Commerce.Note: Values in parentheses “()” not certified (information only).

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ResultsNIST SRM 1085b

Element & wavelength Certified (mg/kg) Found (mg/kg) Duplicate (mg/kg) Recovery (%) RPD dup. (%)Ag 328.068 304.6 307.0 315.9 100.8 2.9Al 308.215 {300.4} 300.8 306.6 100.1 1.9B 249.678 (300) 312.4 327.8 104.1 4.9Ba 493.408 (314) 331.3 339.1 105.5 2.4Ca 422.673 (298) 292.7 300.6 98.2 2.7Cd 228.802 302.9 305.1 310.8 100.7 1.8Cr 205.560 302.9 324.1 329.7 107.0 1.7Cu 327.395 295.6 303.0 311.1 102.5 2.7Fe 259.940 {301.2} 310.7 316.9 103.1 2.0Mg 285.213 297.3 303.6 309.8 102.1 2.1Mn 260.568 (289) 291.3 296.8 100.8 1.9Mo 204.598 (296) 312.7 317.8 105.6 1.6Na 588.995 305.2 299.4 309.7 98.1 3.5Ni 230.299 295.9 315.5 319.7 106.6 1.3P 177.434 {299.9} 317.0 317.4 105.7 0.1Pb 283.305 297.7 308.7 313.2 103.7 1.5Si 251.611 {300.2} 315.1 314.8 105.0 0.1Sn 283.998 (294) 317.2 322.7 107.9 1.7Ti 334.941 {301.1} 311.5 317.2 103.5 1.8V 292.401 297.8 309.1 314.5 103.8 1.8Zn 213.857 296.8 308.8 314.9 104.1 2.0

Wear-metals in lubricating oil — sample source NIST US Department of Commerce.Note: Values in parentheses “()” not certified (information only), values in brackets “{}” not certified (reference only).

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ResultsSystem stability

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ExperimentalWashout / carryover & speed of analysis

Blank measurement Carryover (% of standard concentration)Ba 493.408 Ca 422.673 Fe 259.940 Cu 327.395 Mg 285.213 Zn 213.857

1 0.039 0.047 0.035 0.043 0.045 0.0272 0.039 0.032 0.032 0.046 0.057 0.0263 0.052 0.034 0.035 0.039 0.058 0.0374 0.050 0.034 0.038 0.040 0.047 0.037

Washout/carryover

Speed of analysis

Tube-to-tube analysis time averaged 33 seconds, equating to > 100 samples/hour.

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SVS 2 Results Summary

• Were able cut the sample analysis cycle time from about 90 seconds to about 33 seconds per sample using the SVS 2, without compromising accuracy, precision or stability.

• “Dead time” is eliminated (sample uptake, stabilization and washout times)

• SVS 2 utilizes stacked switching valves, sample loop and high speed, positive displacement motor

• Constant solution flow improves plasma stability

• Sample never contacts pump tubing, inert sample path reduces sample carryover

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Application PapersAvailable on the Agilent Technologies Web site

(http://www.agilent.com)• SI-A-1413 Determination of metals in oils by ICP-OES• SI-A-1417 Determination of V, Ni and Fe in crude oils and bitumen with Sc

as an internal standard• SI-A-1420 Determination of wear metals in lubricating oil with Axial ICP• SI-A-1422 Determination of Pb in Unleaded Gasoline with Axial ICP• SI-A-1423 Determination of trace elements in a xylene solution of oil by

ICP-AES with ultrasonic nebulization and membrane desolvation• SI-A-1427 Multi-element analysis of fuel and lubricating oils by

simultaneous ICP-OES• SI-A-1431 Improving Throughput for Oils Analysis by ICP-OES

PLUS: SI-A-1202, SI-A-1415 and SI-A-1418

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Questions?

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