Anyone have a virgin oil analysis on Mobil EAL Arctic 32 / 68 / 220 ? I am especially interessed in evt. Phosphorus and Calcium content?

If you can comment, please also add what kind of analysis (ICP/RDE).

Thanks.

No P or Ca present in the virgin Mobil POE lubes. I don't think the 220 comes from Mobil. I suspect you need to look at Castrol SW 220 for this product. Castrol SW 68 and SW 220 oils are used in Carrier chillers.

You have a steep learning curve to come up before you tackle a lot of refrigeration lubricant analyses. There are very few people who know this area well, even at the equipment manufacturers.

Good luck

I agree. That is the problem. We detect 49 ppm P and 26 ppm Ca in new unused EAL Arctic 32 straight from can. (No contamination).

We have trippelchecked, and our calibration is fine. Anyone have experiences with difference of RDE and ICP results? We run RDE.

You mentioned the sample came from a can. Is someone other than Mobil packaging the product for you? If so, there may be some additives coming from the packaging process. The Mobil label will identify who packages the product. You may also sample containers with different batch numbers, which also appear on the label. Contact your Mobil rep for more information.

Mr. Hughes, the Mobil EAL Arctic 32 POEs are additive free with the exception of antioxidant (the Arctic 22CC has additives present, but not P or Ca based). I would check for the presence of mineral oil as this is the likely base oil for the additives contaminating the POE. Refractive index is the standard methodolgy to check for mineral oil in POE, but you will need a clean sample of Arctic 32 to use as a reference. Construct a calibration curve of RI versus mineral oil content for each POE.

One other possibility is the contamination of the Arctic 32 with an aircraft engine POE. These normally contain TCP as a ferrous protection additive. I don't know the aircraft products well, but I suspect they do not use any Ca as they need very good high temperature properties and can't leave any ash behind.

I don't think the testing methodology matters between ICP and RDE unless you have sample carryover problems, which you should have eliminated with triple checking. We use ICP ourselves.

Thanks for your input. We are in contact with the supplier and have sent them both batch number and a oil sample.

Hopefully we wil get an answer to what has happend.

just wantet to put a final reply to this thread.

- We sent a sample to another lab, and got confirmation on the results. They used ICP
- Our instrument manufactorer in US tested three samples (from same can), and confirmed the precense of theese elements.
- Manufactorer reported 0 ppm in the same samples on their ICP analysis..

Just a couple of things. As long as standard and sample contain same basestock - ester - RDE and ICP will produce the same results. Problem occurs if standard diluted with hydrocarbon oil and esters (aircraft oils) are analyzed. Same elements still detected, a mutiplication factor 1.5 - 2 needed to get same answer.
Both are affected by easily ionizable elements (EIE) such as Na, Ca - again multiplication factor needed. For aqueous samples - ICP typically has better detection capabilities due to better stability - would expect the same for oils.
Were samples from other cans analyzed or just one can?
Could Ca, P be removed by fine filtration? Would pick up Zn if contaminated with over based ZDDP.

Bob, I want to make sure I am clear on what I think you said. I interpreted what you said as:

Esters analyzed by ICP will give higher counts than the hydrocarbon oil based standard for the same concentration of elements.

This effect is due to the different base oil being sent through the nebulizer of the ICP injection system? Is this a viscosity issue or a chemical issue?

Does this effect occur if the ester is diluted 1:5 with kerosene? (if the oil standard is also diluted with kerosene as well, would this make a the response between the two oils different?)

Are some elements more prone to changes in response than others?

Let me know if I have misunderstood what you meant.

Mr. Hughes - it seems you have a fundamental disagreement on analytical methodology. I don't normally see any significant levels P or Ca in the EAL Arctic products when tested by ICP unless they are contaminated.

If the manufacturer of the Mobil POE products (Hatco) didn't find any P of Ca in your samples, I would tend to believe them as they are capable of doing this testing well. You may need to investigate the choices of wavelenghts you are using to determine Ca and P. We use 317.933 nm for Ca and 178.221 nm for P, and don't see any interferences from elements normally found in samples.

Sorry for the confusion. RDE is affected by differences in sample and standard basestock compositions both chemical and viscosity.
For ICP a 1:5 dilution with kerosene is usually sufficient to minimize effects of viscosity on ICP.
One way to get different results on RDE and ICP is if particles are involved - most ICP nebulizers are designed to remove droplets, and consequently particles, larger than 6 microns - end up in drain - to produce stable plasma. RDE - as long as particles stay suspended during preheat cycle - the rotating disc will transport them to the arc/spark source for partial to complete analysis. For RDE, particle transport is controlled by particle density due to settling; 12 micron Al particles reach source but less than 6 micron steel particles get on disc for analysis. Reason why some labs offer oil filtration through porous discs to ensure all particles reach source. Acid dissolution techniques are also sometimes used.

quote:

Originally posted by Bob K.:
Acid dissolution techniques are also sometimes used.

It is shame that acid digestion is not used more often, or to become a standard in lube spectroscopy. All that guessing about particles size limitation is out of door. Any metal present in an oil sample, either in chunks or in metal complexes, is dissolved in nitric acid, and its full concentration is determined by ICP. There is absolutely no better and more reliable method for determination of total trace metals concentration. The accuracy and consistency of this method is based on regularly performed calibration, and on the fact that the viscosity of the original sample does not affect the uptake of the digested sample. However, other methods could be used on a complementary basis if you want to identify metallurgy of the individual or group of particles (e.g. microscopic ferrography).

Forgot to mention that for the tracking and trending purposes one need to do a baseline acid digest analysis. The principle is the same as for the other analyses.