Application Note
Petrochemicals

High-Throughput Multi-Elemental
Analysis of Crude Oil
Accurate determination of Ni and V, using an Agilent
5110 VDV ICP-OES according to ASTM D5708-15
test method

AuthorIntroduction

Jenny Nelson
Sima Singha
Neli Drvodelic
Agilent Technologies, Inc.

Crude oil is one of the most actively traded commodities in the world. In North
America, the West Texas Intermediate (WTI) crude, which trades on the New York
Mercantile Exchange (NYMEX), is commonly used as a benchmark in oil pricing. In
Europe, Africa and the Middle East, the benchmark is North Sea Brent crude, which
trades on the Intercontinental Exchange (ICE). WTI is also known as Light Sweet
crude oil because of its relatively low sulfur (S) content of 0.42% or less by weight.
To ensure the quality of crude oil and acceptance of the oil into central storage hubs
ready for trading, NYMEX set out quality specifications relating to S content, specificgravity, basic sediment and water (BSW), and pour point. However, in January 2019(in collaboration with the industry), other quality standards were introduced relating tomicro carbon residue (MCR), total acid number (TAN), and maximum concentrationof nickel and vanadium content (1). Since both nickel and vanadium can de-activatecatalysts during oil processing, the specification for WTI
crude was set at less than 8 ppm by weight for nickel and lessthan 15 ppm by weight for vanadium.
ASTM Standard D5708-15 Test Method B relates to thequantitative determination of nickel, vanadium, and iron in
crude oils and residual fuels using inductively coupled plasma
atomic emission spectrometry (ICP-AES) (2). The method issuitable for the analysis of Ni and V in WTI crude,
in line with the latest quality standards. ICP-OES is a fast,multi-element technique that is widely used as a workhorsein the petroleum industry and many oil testing laboratories
will be familiar with ASTM ICP-OES methods.
In this study, a fast and robust method was developed using
the Agilent 5110 Vertical Dual View (VDV) ICP-OES fitted witha switching valve. The 5110 ICP-OES was used to quantify
23 elements, including Ni and V, in oil-related products
according to D5708-15. The method is suitable for theaccurate, high-throughput analysis of large numbers ofsamples over long runs.

Experimental
Instrumentation
The Agilent 5110 VDV ICP-OES fitted with the AVS 7 switchingvalve accessory and SPS 4 autosampler was used for the
cost-effective analysis of crude oil samples. The 5110 was
equipped with a Seaspray concentric glass nebulizer, a
1.4 mm i.d. organics torch, solvent resistant tubing, and adouble-pass glass cyclonic spray chamber. The Easy-fit torchaligns automatically, enabling reproducible performance
regardless of the operator. The vertical orientation of the torchand solid-state radio frequency (SSRF) system generate a robust,
stable plasma that is suitable for the measurement of complex
samples over extended periods (3). The system can rapidly
adjust to changes in the plasma conditions arising from thevarying composition of crude oils from different sources.
The plasma’s high tolerance to dissolved solids and organic
solvents mean that less time is spent cleaning the sample
introduction system and fewer replacement torches areneeded.
The 5110’s Vista Chip II CCD detector facilitates the analysis
of samples much faster than other ICP-OES instrumentation(4). The performance is due to the detector’s 1 MHz pixel
processing speed and ability to measure the full wavelength
range in a single exposure without the need for multiple
detectors or slits. The Vista Chip II can actively adapt using
integration times ranging from 1 to 100 s, providing a full eightorders of dynamic range.

2

The detector allows access to multiple wavelengths perelement, so the user is not limited to wavelengths that may
be susceptible to interferences. This feature is especially
important for the analysis of samples with a complex matrix
such as crude oil, where spectral interferences can beproblematic. In addition, simple and complex backgroundstructures can be corrected by modeling the background toeach analyte peak. Corrections can be done automaticallyusing the Fitted Background Correction (FBC) technique
included in the Agilent ICP Expert software (5).
The high-speed Vista Chip II detector also enables
IntelliQuant—a fast, single scan screening mode used forthe rapid identification and semi-quantification of analytes
in a sample (6). IntelliQuant is also useful for method
development, such as identifying interferences or checking
the calibration range of elements present in a sample.
IntelliQuant results are presented visually using acolor-coded heat map of the periodic table. The
color-coding concentration levels are user-customizable,
allowing laboratories to set the high concentration limit as
the maximum regulated concentration for a specific element.
This set up ensures that any noncompliant samples will be
flagged automatically on the periodic table heat map.
The Agilent AVS 7 switching valve allows labs to improvetheir sample throughput and reduce argon consumption
by at least 50% per sample (7). The switching valve is fully
integrated with the 5110 ICP-OES hardware and software,
making it easy to set up and operate. It uses a high-speed
positive displacement pump to speed up the sample uptake
time. Argon bubble injection between sample and rinse
solution prevents mixing of the sample and rinse allowing alonger read time and minimal carry over. The fast, efficient
analysis provided with by AVS 7 also extends the lifetime of
consumables, further reducing operating costs.
If needed, operation of the 5110 ICP-OES can be simplified
using an ICP Expert Applet software—a limited-accessinterface that allows less-experienced users to run ananalysis without having access to method parameters. They
simply select the appropriate applet, enter sample details,
ignite the plasma, and click 'Start' (8). An example screenshotof the Applet software is shown in Figure 1.

Table 2. AVS 7 switching valve settings.
Parameter

Figure 1. ICP Expert Applet browser-based software interface that is suitable
for the routine operation of the 5110 ICP-OES.

The instrument and method parameters for the 5110 VDVICP-OES are given in Table 1 with the AVS 7 settings given
in Table 2.
Table 1. 5110 VDV ICP-OES instrument and method parameters.
Parameter

Setting

Viewing Mode

RadialRead Time (s)8Replicates3

Stabilization (s)15Rinse Time (s)0Pump Speed (rpm)12

RF Power (kW)

1.3

Aux Flow (L/min)

1.3

Ar/O2 Addition (%)

20

Plasma Flow (L/min)

12

Nebulizer Flow (L/min)

0.60

Viewing Height (mm)10Sample Pump Tubing

Black/black*

Internal Standard Tubing

Orange/green*

Waste Pump Tubing

Blue/blue*

Internal Standard

Yttrium*Solvent-resistant tubing.

Setting

Valve Uptake Delay (s)7.0

Pump Rate - Uptake (mL/min)

25.0

Pump Rate - Inject (mL/min)

6.0

Sample Loop Size (mL)

1.0Preemptive Rinse Time (s)1.8

Bubble Inject Time (s)1.8Standards and sample preparation
Calibration standards containing the following elements: Ag,
Al, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Si, Sn,
Ti, V, and Zn were prepared at 0.1, 1, 10, 25, and 50 mg/kg.
The S calibration standard was prepared at 200, 450, 1000,
and 2000 mg/kg using an Agilent single element standard(part number: 5190-8784). The other calibration standards
were prepared by weight by adding Agilent A21+K wear
metal standard (9, part number 5190-8713) into a
pre-prepared o-xylene diluent (Fisher Scientific). The o-xylene
diluent, which included a matrix modifier and yttrium internal
standard (ISTD) was added to the sample line before thenebulizer using a mixing tee-connector. The standards and aquality control (QC) sample prepared by ASI Standards (OakRidge North, Texas, USA) were matrix matched to a constantviscosity to give a total oil concentration of 10% (w/w) in eachsolution. A 5 ppm multi-element standard was used as aContinuing Calibration Verification (CCV) solution.
Crude oil samples covering a wide range of API gravity
and density were analyzed in this study. The samples wereprepared according to the ASTM D5708-19 method, which
is an expansion of ASTM D5708-15. The samples were all
diluted from 1:10 up to 1:20 in o-xylene by weight. The moreviscous samples that did not readily flow at room temperature
were heated in a hot block at 60 °C and shaken before being
weighed and diluted with o-xylene.
Two National Institute of Standards and Technology (NIST,
Gaithersburg, MD, USA) standard reference materials (SRMs)
were used to validate the method for the certified elements Ni
and V. NIST 1634c Trace Elements in Fuel Oil and NIST 8505
Vanadium in Oil SRMs were diluted approximately 1:60 in theo-xylene diluent before analysis.

3

Table 3. Wavelength and working calibration range.
Element andWavelength (nm)Table 3. Wavelength and working calibration range.

Background
Correction

Correlation
Coefficient

Calibration
Fit

Calibration
Range, mg/kg

Ag 328.068

Fitted0.9999Linear

0.1–50Ag 338.289

Fitted0.9999LinearAl 237.312

Fitted0.9999Al 396.152

FittedB 249.678

FittedB 249.772

Element andWavelength (nm)Background
Correction

Correlation
Coefficient

Calibration
Fit

Calibration
Range, mg/kg

Sn 189.925

Fitted0.9999Linear

0.1–500.1–50Sn 283.998

Fitted0.9999Linear

0.1–50Linear

0.1–50Ti 334.941

Fitted1

Linear

0.1–500.9999Linear

0.1–50Ti 336.122

Fitted0.9999Linear

0.1–500.999

Linear

0.1–50V 292.401

Fitted0.9999Linear

0.1–50Fitted0.999

Linear

0.1–50V 309.310

Fitted0.9999Linear

0.1–50Ba 455.403

Fitted0.9999Linear

0.1–50

Zn 206.200

Fitted0.9999Linear

0.1–50Ba 493.408

Fitted1

Linear

0.1–50

Zn 213.857

Fitted0.9999Linear

0.1–50Ca 315.887

Fitted0.9999Linear

0.1–50Ca 422.673

Fitted0.9999Linear

0.1–50

Cd 214.439

Fitted0.9999Linear

0.1–50

Cd 226.502

Fitted0.9999Linear

0.1–50Detection limits

Cr 205.560

Fitted1

Linear

0.1–50Cr 267.716

Fitted1

Linear

0.1–50

Cu 324.754

Fitted0.9999Linear

0.1–50

Cu 327.395

Fitted0.9999Linear

0.1–50Fe 234.350

Fitted1

Linear

0.1–50The Method Detection Limits (MDLs) shown in Table 4
are based on three sigma measurements of 10 replicate
measurements of blank o-xylene solutions taken during theanalytical run. The results were multiplied by 10 (the sample
dilution factor) to give the MDL in the original sample.

Fe 238.204

Fitted1

Linear

0.1–50K 766.491

Fitted0.9999Linear

0.1–50

K 769.897

Fitted0.9999Linear

0.1–50Element andWavelength (nm)

MDL,
mg/kg

Element andWavelength (nm)

MDL,
mg/kg

Mg 279.553

Fitted0.999

Linear

0.1–50Ag 328.068

0.0170

Mo 202.032

0.3424

Mg 285.213

Fitted0.9999Linear

0.1–50Al 396.152

0.2725

Na 588.995

1.1116

Mn 257.610

Fitted1

Linear

0.1–50B 249.772

0.0202

Ni 216.555

0.2641

Mn 259.372

Fitted1

Linear

0.1–50Ba 455.403

0.0084

P 213.618

0.77400.0499Pb 220.353

1.4314

Results and discussion

Table 4. MDLs based on the sample weight (1 g in 10 g) per the ASTM method.

Mo 202.032

Fitted1

Linear

0.1–50Ca 422.673

Mo 204.598

Fitted1

Linear

0.1–50

Cd 226.502

0.0145

S 181.972

1.4170Na 588.995

Fitted0.9999Linear

0.1–50Cr 267.716

0.0158Si 288.158

0.0491

Na 589.592

Fitted0.9999Linear

0.1–50

Cu 324.754

0.0126

Sn 189.925

2.9423

Ni 216.555

Fitted0.9999Linear

0.1–50Fe 238.204

0.0359Ti 334.188

0.0424

Ni 231.604

Fitted0.9999Linear

0.1–50K 766.491

0.3968V 292.401

0.0425

P 178.222

Fitted0.9999Linear

0.1–50

Mg 279.553

0.0059Zn 213.857

0.0580

P 213.618

Fitted0.9999Linear

0.1–50

Mn 257.610

0.0049Pb 182.143

Fitted0.9999Linear

0.1–50

Pb 220.353

Fitted0.9999Linear

0.1–50

S 181.972

Fitted0.9999Linear

200–2000

S 182.562

Fitted0.9999Linear

200–2000

Si 251.611

Fitted0.9999Linear

0.1–50Si 288.158

Fitted1

Linear

0.1–504

SRM analysis

Table 6. Results from the analysis of a crude oil QC solution, n=10.

To validate the method for the analysis of Ni and V (and S) in
oil, both elements were determined in duplicate samples of
the NIST 1634c fuel oil SRM. V was also measured 10 times
in duplicate samples of NIST 8505 SRM. The recoveries of Ni
and V (and S) were all within ±10% of the certified values, as
shown in Table 5. There was good agreement between theconcentration measurements for multiple wavelengths of thesame element (within ±10%).
Table 5. Analysis of Ni, V, and S in oil SRMs.
NIST 1634c (n=10)
Element
andWavelength(nm)

MeasuredValue(mg/kg)NIST 8505 (n=10)

Certified Recovery
Value
(%)
(mg/kg)MeasuredValue(mg/kg)

Certified Recovery
Value
(%)
(mg/kg)Ni 216.555 17.67 ± 0.26

17.54

101

V 292.401

27.39 ± 0.38

28.19

97

363.07 ± 7.34 390.00

93

V 309.310

28.18 ± 0.37

28.19

100

375.97 ± 7.64 390.00

96

V 311.837

26.79 ± 0.35

28.19

95

355.93 ± 6.79 390.00

91

S 181.972

20465 ± 290

20000IV

S 182.562

20613 + 302

20000IV

Element andWavelength (nm)Measured
Value (mg/kg)

SD

Reference
Value (mg/kg)

Recovery(%)

Ca 315.887

5.01

0.09

5.00

100

Ca 396.847

5.05

0.09

5.00

101

Ca 422.673

5.08

0.08

5.00

102

K 766.491

4.77

0.24

5.00

95

K 769.897

5.00

0.31

5.00

100

Na 588.995

5.25

0.23

5.00

105

Ni 216.555

5.07

0.25

5.00

101

Ni 231.604

4.71

0.30

5.00

94

V 292.401

5.33

0.26

5.00

107

V 309.310

5.49

0.27

5.00

110

V 311.837

5.34

0.26

5.00

107

Table 7. Averaged measured concentrations of multiple elements inrepresentative crude oil samples, n=10.

102

Element andWavelength(nm)

Sample 1
Measured Conc
(mg/kg)Sample 2
Measured Conc
(mg/kg)Sample 3
Measured Conc
(mg/kg)103

Ag 328.068

<LOQ

<LOQ

<LOQ

Al 396.152<LOQ

0.60 ± 0.03

0.40 ± 0.05

IV = Information value.

B 249.772

5.34 ± 0.02

7.10 ± 0.32

6.64 ± 0.02

Ba 455.403

0.02 ± 0.01

0.03 ± 0.01

<LOQ

QC solution

Ca 422.673

0.44 ± 0.01

46.97 ± 0.72

8.84 ± 0.94

Since the range of elements in crude oil RMs is limited, asolution from ASI Standards containing known concentrationsof Ca, K, Na, Ni, and V was used as a QC test solution.

Cd 226.502

0.10 ± 0.01

0.08 ± 0.01

0.08 ± 0.00

Cr 267.716

0.02 ± 0.01

0.04 ± 0.01

0.08 ± 0.01

Cu 324.754

0.04 ± 0.01

0.03 ± 0.01

0.03 ± 0.01

The measured concentrations obtained by the 5110 VDVICP-OES and the reference values are given in Table 6.
Recoveries of Ca, K, Na, Ni, and V were within 10% of the
expected values, with good agreement between the different
wavelengths of the same element (Table 6).

Fe 238.204

0.64 ± 0.00

21.91 ± 0.07

21.71 ± 0.30

K 766.491

0.55 ± 0.11

46.34 ± 2.12

1.97 ± 0.81

Mg 279.553

0.03 ± 0.00

0.51 ± 0.10

0.12 ± 0.01

Mn 257.610

0.01 ± 0.00

0.06 ± 0.03

0.01 ± 0.01

Mo 202.032

0.16 ± 0.29

0.09 ± 0.02

0.81 ± 0.04

Na 588.995

1.45 ± 0.24

48.54 ± 0.84

76.09 ± 2.91

Ni 216.555

0.42 ± 0.24

5.05 ± 0.05

21.56 ± 0.24

P 213.618

0.15 ± 0.55

<LOQ

47.53 ± 0.25

Pb 220.353

1.29 ± 0.63

0.06 ± 0.18

<LOQ

Quantitative results
Quantitative results for 23 elements in 20 crude oil samples
were acquired using the 5110 VDV ICP-OES. The results inTable 7 show the results for three representative samples. The
results show that most elements were present in the crude
oil samples at low concentrations (< 1 ppm). There was somevariation in the concentrations of Ca, Fe, K, Na, Ni, S, and V in
the representative samples. Two of the three samples met theWTI crude oil specifications for Ni (8 ppm) and V (15 ppm).
Overall, nine of the 20 samples analyzed in this study met the
WTI specifications for Ni and V (not all data is shown).

S 181.972

1146.39 ± 12.94

883.38 ± 4.39

19825.10 ± 317.60

Si 288.158

0.79 ± 0.01

0.55 ± 0.02

0.84 ± 0.03

Sn 189.925

4.55 ± 0.75

<LOQ

<LOQ

Ti 334.188

0.04 ± 0.01

0.05 ± 0.01

0.04 ± 0.01

V 292.401

1.17 ± 0.03

4.98 ± 0.03

100.39 ± 0.72

Zn 213.857

0.29 ± 0.02

0.16 ± 0.02

0.18 ± 0.00

5Long-term stability
To demonstrate the robustness and precision of the 5110
VDV ICP OES over an extended period, approximately 400
crude oil samples were analyzed over six hours (Figure 2).
QC solutions were measured every 10 samples. The results
for all elements show recoveries within ±10% and %RSD lessthan 3%.

Elements present at low concentrations are shown in yellow,
medium concentrations are shown in orange, and highconcentrations are shown in red. The concentration ranges
are user adjustable.

The robust plasma generated using the SSRF system andthe vertically orientated torch ensure that the 5110 delivers
excellent repeatable performance, even for complex crude oilsamples.

Figure 3. Heat map generated by a rapid IntelliQuant analysis of a crude
oil sample.

Conclusion
Figure 2. Long-term stability test results. Recovery of QC sample analyzed every
10 samples over approximately six hours. Boron was only measured for partof the six-hour run before a problem occurred, so no results for B have been
included in the graph.

Sample analysis timeAll 23 elements in each sample were determined in
52 seconds using the 5110 VDV ICP-OES fitted with the
AVS 7. The fast analysis time was due to the high-speed
Vista Chip II detector and integrated sampling valve. Totalargon consumption per sample was 17.0 L.

Full spectrum scan using IntelliQuant
An IntelliQuant scan was performed during the routine
analytical run to provide additional information on thesamples. IntelliQuant rapidly scans for up to 70 elements
in less than 15 seconds—an efficient way to identify andsemiquantify elements that are not present in the calibration
standards. The results for one of the crude oil samples areshown in Figure 3. The heat map shows that 23 elements
were detected in the scan, as well as their approximate
concentration (ppm). For the crude oil sample, the scan
provided additional elemental information for Be, Se, Nb,
Gd, and Rh.

6

The Agilent 5110 VDV ICP-OES fitted with an AVS 7 switchingvalve was used for the analysis of 23 elements in crude oils
following dilution in o-xylene. All elements were quantified ina 52 s run, requiring only 17 L of argon per sample.
The 5110 ICP-OES includes advanced hardware and softwarefeatures to simplify operation and method development for
the analysis of crude oil samples. The Vista Chip II detector
allows analysis across a wide dynamic range eliminating
the need for multiple dilutions. It also allows access tomultiple wavelengths per element, so the user is not limited
to wavelengths that may be susceptible to interferences.
Within the ICP Expert software, fitted background correction
automatically corrects the background without the analyst
needing to intervene. Using these features, the method wasshown to deliver excellent accuracy for the measurement of
Ni and V in two NIST oil SRMs and good recoveries for Ca,
K, Na, Ni, and V in a QC reference material. The robustnessof the solid-state RF plasma system and the vertical torchorientation of the 5110 VDV ICP-OES provided excellent longterm stability during the analysis of organic oil samples overapproximately six hours.
For the routine analysis of samples, including testing for Ni

and V in accordance with the latest specifications for WTI
crude oil, the powerful ICP Expert software includes:

4.

CCD and CID solid-state detectors, Agilent publication,
5991-4842EN•

ICP Applet mode – a simplified user interface thatenables operators of all skill levels to carry out routine
analysis of complex samples.

5.

Fitted Background Correction (FBC)—fast, accurate
and fully automated background correction, Agilent
publication, 5991-4836EN•

IntelliQuant semiquantitative scan mode—a usefulextra source of information for method development byidentifying interferences and checking the calibration
range. IntelliQuant also identifies and provides anestimation of the concentration of over 70 elementsin the sample in less than 15 seconds, providing extra
confidence in the analysis.

6.

Reduce costs and boost productivity with the Advanced
Valve System (AVS) 6 or 7 port switching valve system,
Agilent publication, 5991-6863EN

7.

Rapid Sample Assessment and Simplified Method
Development with IntelliQuant, Agilent publication, 59916876EN

8.

ICP Expert Software, Agilent publication, 5991-7720EN

9.

Agilent A21 wear metal standard certificate of analysis,
accessed October 2019, https://www.agilent.com/cs/
library/certificateofanalysis/5190-8706_0017141914.pdf•

Data reporting options—Report Designer enables users
to configure reports to include only the data that isrequired, and to customize sample report templates witha company logo.

References
1.

CME Group, NYMEX Physically-Delivered Light Sweet
Crude Oil Futures, 2017 (accessed October 2019) https://www.cmegroup.com/trading/energy/nymexs-physicallydelivered-light-sweet-crude-oil-futures-faq.html

2.

ASTM D5708-15, Standard Test Methods for
Determination of Nickel, Vanadium, and Iron in Crude Oils
and Residual Fuels by Inductively Coupled Plasma (ICP)
Atomic Emission Spectrometry, ASTM International,West Conshohocken, PA, 2015, www.astm.org

3.

Benefits of a vertically oriented torch—fast, accurate
results, even for your toughest sample, Agilent
publication, 5991-4854EN

www.agilent.com/chem

This information is subject to change without notice.
© Agilent Technologies, Inc. 2019
Printed in the USA, December 17, 20195994-1583EN