Insights from industry

Analysis of Wear Metals in Oil Using ICP-OES with Factory Prepared Methods

In this interview, Olaf Schulz from SPECTRO talks to AZoM about the application of the SPECTRO GENESIS ICP-OES analyzer to determine the content of metal particulates in lubricants.

Could you please provide a brief introduction to Spectro Analytical Instruments and the markets you serve?

SPECTRO Analytical Instruments is a leading supplier of X-ray fluorescence (XRF), ICP-OES/AES, ICP-MS, and Arc/Spark-OES instruments for science and industry. SPECTRO’S benchtop, portable, and hand-held spectrometers are used for applications in elemental analysis, trace element analysis, and environmental analysis.

Founded in 1979 as a 3-man-enterprise, SPECTRO today employs over 400 employees around the world. Since our inception, over 30,000 instruments have been delivered globally.

SPECTRO is a member of the AMETEK Materials Analysis Division. AMETEK, Inc. is a leading global manufacturer of electronic instruments and electromechanical products with over 14,000 colleagues at more than 120 manufacturing and sales and service operations in the United States and nearly 30 other countries around the world.

Could you briefly explain the theory behind how ICP-OES works?

In ICP-OES, the excitation source is an electrically powered Inductively Coupled Plasma, into which a nebulized sample is introduced as an aerosol.

In the plasma, the sample is thermally atomized and partially ionized, and the atoms and ions are excited to emit element specific radiation. The emitted light is transferred into an optical system where it is diffracted; individual emission lines are separated and can be selected for measurement.

Modern ICP-OES use CCDs (Charge-Coupled Devices) to convert the light into an electric signal. The signal height of an element’s emission line is directly proportional to its concentration in the sample, so the elemental concentration can be calculated by means of an empirical calibration.

The GENESIS ICP-OES from SPECTRO comes with

Figure 1. The GENESIS ICP-OES from SPECTRO comes with "plug and analyze" analytical methods for wear metal determination in oils.

What makes ICP-OES so well suited for wear metal analysis in oils?

In normal conditions where wear is not too severe, the metallic particles entering the lubricant are usually very finely distributed (10 microns or less) and remain largely suspended in the oil without settling out. Oil samples like these can essentially be treated as solutions and analyzed accordingly.

Typical concentration levels for wear metals lie in the range from 1 to 500 ppm, and for additive elements up to several thousand ppm. These concentrations are well within the scope of spectroscopic techniques such as Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES), Atomic Absorption Spectrometry (AAS) and Energy Dispersive X-ray Fluorescence (EDXRF).

The requirement for speed and the need to measure many elements in each sample means that sequential techniques are usually considered too slow. Therefore, the high speed of simultaneous ICP-OES has made it the technique of choice, particularly as the sample preparation required is usually limited to a simple dilution with a solvent such as kerosene.

Why is oil analysis important to condition monitoring of engines?

Wear metal in oil analysis has been used to monitor the condition of engines and other machinery for many years. It can be viewed similarly to blood tests a physician performs to determine the condition of a patient. It can be applied to most lubricated mechanical systems.

One of the most powerful arguments for wear metal analysis is that it can trigger preventive maintenance before component wear leads to potentially catastrophic failure. Early detection can even prevent wear and costly repairs.

Stability test - oil diluted in kerosene 1:10, concentration 10 ppm. Examining only 16 elements, a typical FAAS instrument can sequentially analyze up to 180 samples in an 8-hour shift. In the same time, the affordable SPECTRO GENESIS can analyze up to 320 samples — independent of the number of elements to be analyzed. Plus, it enables safe automatic operation, uses no flammable gases, while analyzing elements such as silicon, aluminum, and phosphorous where FAAS analysis falls short.

Figure 2. Stability test - oil diluted in kerosene 1:10, concentration 10 ppm. Examining only 16 elements, a typical FAAS instrument can sequentially analyze up to 180 samples in an 8-hour shift. In the same time, the affordable SPECTRO GENESIS can analyze up to 320 samples — independent of the number of elements to be analyzed. Plus, it enables safe automatic operation, uses no flammable gases, while analyzing elements such as silicon, aluminum, and phosphorous where FAAS analysis falls short.

What are the main advantages of the SPECTRO GENESIS in this application, compared to other instruments?

The SPECTRO GENESIS uses the latest detector technology and provides full-spectrum analysis to cover the entire elemental range needed for additive, wear, and trace analysis of lubricating oils.

In particular, it offers excellent sensitivity for critical light elements such as Na, Mg, Al, and Si, while offering high sensitivity for wear and trace elements.

The SPECTRO GENESIS measures the entire spectrum simultaneously. It therefore provides extreme speed, and achieves rapid sample cycle times of 90 seconds or less. Up to 320 samples can be analyzed per shift — independent of how many elements are analyzed.

What practical benefits will users see with the SPECTRO GENESIS, particularly in real high-throughput labs?

The main practical benefit of the SPECTRO GENESIS is it's “plug and analyze” capability. The instrument is available with method packages for wear metals and additives in lube oil, diesel fuel, crude oil and biodiesel, included out of the box. This means that the instrument can be used for wear analysis straight away, without having to develop analytical methods first.

The sample introduction system is included, and for higher sample loads a range of autosamplers are available.

All methods have been developed based on the relevant ASTM and EN methods and standards using custom blended “Conostan” standards. Where possible, methods were combined to increase efficiency.

To operate, the methods will only need to be installed from a CD and calibrated using the “Conostan” custom standards. A detailed standard operating procedure (SOP) describes the complete work flow from sample preparation to method validation.

Table 1. Recoveries of NIST SRM 1084a diluted in Kerosene (1:10). Values in brackets are Indicative.

Element Certified Conc. [mg/kg] Measured Conc. [mg]kg] Recovery [%]
Al (104) 102 98.1
Ag 101.4 ± 1.5 100.5 99.1
Cr 98.3 ± 0.8 101.1 102.8
Cu 100 ± 1.9 103.8 103.8
Fe 98.9 ± 1.4 106.5 107.7
Mg 99.5 ± 1.7 97.7 98.1
Mo 100.3 ± 1.4 103.3 103
Ni 99.7 ± 1.6 105.7 106
Pb 101.1 ± 1.3 103 101.9
Sn 97.2 ± 2.6 100.7 103.6
Ti 100.4 ± 3.8 104.3 103.9
V 95.9 ± 9.4 102.4 106.8
S (1700) 1570 92.4
Si (103) 106.9 103.8

Have you had any feedback from customers about the SPECTRO GENESIS?

Even before the introduction of the petrochem package, the SPECTRO GENESIS has been used for the analysis of petrochemical products for many years. For wear metal in oil analysis in particular, the GENESIS has become a standard instrument for many laboratories.

The instrument is valued for its outstanding long term stability, proven technology and its reliable design, which makes it ideal for routine use. Low operational and investment costs are viewed as additional advantages.

Are there any further improvements or additional capabilities you plan to add to the instrument in future versions?

We continuously monitor analytical requirements for petrochemical applications by keeping in close contact with our customers. New requirements will automatically result in improvements, amendments or new instrumentation.

What are the major developments you foresee in this industry in the next few years, and what role do SPECTRO plan to play in this?

Olaf SchulzTotal automation is a trend which is becoming more and more visible. While today, samples are often still separately prepared and then manually transferred to the instrument, larger laboratory firms demand a fully automated solution.

With the ACAROS, a heavy duty, autodilutor and robotic system, such a solution has recently been introduced. Our plan is to be a competent partner for such requirements, providing customers with routine proven solutions.

About Olaf Schulz

Olaf Schulz has gained his experience and knowledge in optical emission spectroscopy over the last 29 years working in the automobile industry and since 1989 at SPECTRO Analytical Instruments, with several assignments and positions in application, sales and marketing.

Today, Olaf Schulz works as the Product Manager for SPECTRO’s ICP-OES product line.

Disclaimer: The views expressed here are those of the interviewee and do not necessarily represent the views of AZoM.com Limited (T/A) AZoNetwork, the owner and operator of this website. This disclaimer forms part of the Terms and Conditions of use of this website.

Will Soutter

Written by

Will Soutter

Will has a B.Sc. in Chemistry from the University of Durham, and a M.Sc. in Green Chemistry from the University of York. Naturally, Will is our resident Chemistry expert but, a love of science and the internet makes Will the all-rounder of the team. In his spare time Will likes to play the drums, cook and brew cider.

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