Ash Content in Petroleum Products

Ash Content in Petroleum Products

ASTM D482-13, ASTM D2584, ASTM D5630, ISO 6245:2001, ISO 3451

Ashing of organic-rich samples in a traditional muffle furnace requires long durations, often lasting well into the night or even overnight. The extended time so required for ashing is typically caused by a dearth of oxygen for oxidation of samples. QAsh 1800 Microwave Ashing System from Questron speeds up the ashing process for organic-rich samples by a factor of up to tenfold.

Furthermore, a high wattage QAsh 1800 microwave oven, in conjunction with our high microwave-coupling heating plates, promotes rapid sample heating to the desired temperature. The system is driven by user-made methods that control the entire process, including an air valve that introduces fresh air into the heating chamber, thereby supplying the needed oxygen to ash the samples and, at the same time, pushing out by-product gases produced during ashing. If you are ashing oils, grease, wax, paraffin, polymers or other similar
samples, QAsh will help you deliver better results faster.

Trace Metal s and Wear Metal s Analysis in Petroleum Products

Direct introduction of a petroleum product in an ICP Analysis plasma requires a methodical approach to minimize matrix effects. Different sample introduction modes are used, based on elements of interest and the matrix in question. Whether the choice of instrument is ICP-OES or ICP-MS, dilution of oils before its introduction into the instrument is an essential step.

Introducing QPrep from Questron — an automated, offline dilution workstation, with a built-in dual-syringe, and a robust liquid dispensing module for most reagents and solvents. Working with user-created methods in a PC Windows environment, the system effortlessly generates diluted sample aliquots from original sample tubes into tubes located in different rack types — precisely, efficiently, and automatically. QPrep Liquid Transfer System saves laboratory time and labour, doing repetitive liquid handling tasks. It is a definite synergistic ICP partner. HEPA filtered model also available.

Let us know if you need to digest samples

We manufacture systems to perform both close vessel and open vessel digestions. Please ask us about our QLabPro microwave digestion system, for digestion of some of the toughest samples, retaining trace volatile elements of interests. 12-Vessel set of eVHP vessels or 30 vessel set of LVHT tubes available.

As an alternative to microwave digestion, the QBlock series of Teflon-coated graphite or anodized-aluminum heating blocks are available to accommodate many standard and non-standard sample vials, covering a wide range of temperatures from 180 deg. C to up to 400 deg. C.

Ashing of Petroleum Samples – Microwave and other current techniques

References :
• ASTM D482-13: Standard Test Method for Ash from Petroleum products.
• ASTM D874-92: Standard Test Method for Sulfated Ash for Lubricating Oils and Additives
• ASTM D5630: Standard Test Method for Ash Content in Thermoplastics
• ISO 6245:2001: Petroleum products — Determination of ash
• ISO 3451: 2008: Plastics—Determination of Ash

Ash is the inorganic residue remaining after the water and organic matter have been removed by heating in the presence of oxidizing agents, which provides a measure of the total amount of minerals within an organic sample. Analytical techniques for providing information about the total mineral content are based on the fact that the analyte can be distinguished from the matrix in some measurable way. The four main types of analytical procedures used to determine the ash content of Petroleum samples are based on the principle that minerals are not destroyed by heating and that they have sufficiently low volatility. All these procedures require proper homogenizing of the sample, i.e. samples must be carefully mixed to facilitate the choice of a representative aliquot. The samples may also need to be dried at low heat to avoid spattering during ashing.

These four analytical procedures are as follows:

• Dry Ashing: The sample is ashed in a high-temperature muffle furnace. Most minerals are converted to oxides,
sulfates, phosphates, chlorides or silicates. Although most metals have fairly low volatility at the high temperatures,
some, such as Fe, Hg, and Pb may be partially lost.

• Wet Ashing: The sample is reacted with fuming sulfuric to promote charring, followed by ashing in a muffle furnace. This technique breaks down and removes the organic matrix surrounding the minerals so that they are left in an aqueous solution, before being dry ashed in a muffle furnace.

• Microwave Ashing: The sample is placed into the microwave muffle furnace and the temperature is ramped up,
evaporating the sample, followed by ashing by achieving ashing temperatures. This technique is superior to dry or wet ashing because the time required is drastically decreased, metal losses are less pronounced, and the process is
automated by temperature ramps through user-specified method files. Another advantage is the ability to ash larger
samples for more accurate results.

• Low-temperature plasma dry ashing: A sample is placed into a glass chamber which is evacuated using a vacuum pump. A small amount of oxygen is pumped into the chanber and broken down to nascent oxygen, i.e. O2 2O by an electromagnetic RF field. The organic matter in the sample is rapidly oxidized by the nascent oxygen and the moisture evaporated. The relatively cool temperature of this procedure causes less loss of volatiles but the equipment is relatively expensive.

There are a number of different types of crucibles available for ashing, including quartz, Pyrex, porcelain, steel, and platinum. The selection of an appropriate crucible depends on the sample being analyzed and the furnace temperature used. The most widely used crucibles are made from porcelain because they are relatively inexpensive to purchase, can be used up to 1200 deg. C, and are easy to clean. Although porcelain crucibles are resistant to acids, they can be corroded by alkaline samples and are also prone to cracking. For these reasons, other types of crucible materials are also in use.

In Dry ashing, including microwave ashing, the sample is weighed before and after ashing to determine the concentration of ash present. The ash content can then be expressed as Loss on Ignition (LOI) % = Mash /Msamp X 100. I

In addition to measuring the mineral content of organic samples by ashing, the samples may also be prepared using the digestion process. Generally, ashing results in the minerals being converted to oxides, sulfates, phosphates, chlorides or silicates, whereas digestions result in aqueous solutions of mineral salts. The digestion process is carried out by employing a suitable mix of acids in non-contaminating vessels (usually made of Teflon or similar materials) in a microwave oven or in a block heater. Although sample digestions are very effective and accurate, with wide application, the technique involves an expensive initial investment, followed by ongoing significant expenditure on consumables.