search.noResults

search.searching

saml.title
dataCollection.invalidEmail
note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
Lube-Tech


Figure 4: NaPhenolate absorption response to addition of acidity in the form of Oleic Acid to develop a predictive relationship to determine AN.


Performance


The manual AN methods’ unique capabilities are summarised by the analytical results presented in Figure 5. Here an oxidised mineral oil containing both weak and strong acids was serially diluted with an acid-free ester-based oil with AN analysed for and tracked as a function of dilution. ANTOTAL and ANCOOH each track linearly even as the spectral signature of the oil continuously varies as a result of blending the two oils. Any instrument relying on a chemometric calibration would fail this test as it would not be able to account for the spectral variations induced by dilution of one oil type with another that is spectrally different. This artificial process mimics topping-up with the wrong oil or selecting the wrong oil-type on a direct read instrument, occurrences that are not that unusual but can significantly confound analytical predictions. The manual AN method succeeds because each sample serves as its own reference and all oil matrix changes are accounted for and ratioed out, thus correctly tracking the expected changes. The corollary is that any oil-type (e.g., mineral, ester, hydraulic, etc.) can be analysed for AN in any sequence without having to rely on restrictive correlational chemometric models, proper oil selection or mis-predictions due to the analysis of non-representative samples.


28 LUBE MAGAZINE NO.163 JUNE 2021


PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE


No.134 page 5


Relevance and Conclusion The standard ASTM titrimetric AN and BN methods are slow, expensive, and environmentally problematic, with no reliable, viable deterministic alternatives available. Current FTIR/IR PLS-based direct read AN methods are of questionable value for critical deterministic purposes, their accuracy being reliant on the manufacturers’ claims rather than objective measures or performance validations. The generic stoichiometric AN method developed provides for a robust FTIR-based primary calibration, an objective means of validation, the ability to differentiate between weak and strong acids as well as providing a means for wider implementation via SpectraGryph and Excel®


. Even at ~20 samples/h its performance characteristics should be attractive to most CM and on-site FTIR users wishing to obtain deterministic AN data in lieu of titration. Given that a generic approach is available for implementation, this approach may be more readily adopted by standards associations like the ISO and ASTM for interlaboratory assessments and performance evaluations and open the door to related methods (e.g., BN and H2


O) which have been developed along similar lines.


Figure 5: Serial dilution of mineral oil spiked with oleic acid and p-toluene sulfonic acid diluted with a neutral ester-based oil. AN tracks linearly even as spectral characteristics of the oil change with dilution.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53