Moisture Analysis via Gas Chromatography/BID in Petroleum and Petroleum Products
Water, Water, Everywhere
Analyzing moisture, and how much of it, is critical to the performance of petroleum products, as well as infrastructure and product integrity. For example, moisture in petrochemical feedstock can cause pipelines and valves to freeze, as well as poison some catalysts. One popular method used to analyze for moisture is Karl Fischer Titration (KFT). KFT has a wide dynamic range but has difficulty in measuring relatively low amounts of moisture. In addition, there are the well-known problems of side reactions and known interferences.
An alternative method combines Shimadzu's proprietary Barrier Discharge Ionization Detector (BID) with MilliporeSigma's* moisture analysis column "Watercol". This combination separates and measures the moisture in a formulation of feedstock and provides sensitive and accurate results with measurements made down to a ppm level of moisture detection without any interference.
New Approach Using Gas Chromatography with the Novel BID
Unlike traditional wet chemistry methods, this new method uses Gas Chromatography (GC) with a newer detector - the Barrier Discharge Ionization Detector (BID). The BID is a highly sensitive device that creates ionization from a Helium-based, dielectric barrier discharge plasma. A 17.7eV plasma is generated by applying a high voltage to a quartz dielectric chamber, in the presence of helium at a relatively low temperature. Compounds that elute from the GC column are ionized by this He plasma energy and then detected by the collection electrode and processed as peaks.
The BID is more sensitive than both a Thermal Conductivity Detector (TCD) and a Flame Ionization Detector (FID) with the ability to analyze down to sub-ppm levels of water. Additionally the method uses MilliporeSigma's new, highly polar ionic liquid column, Watercol™, which provides excellent water retention, separation and peak shapes.
Because wet chemistry techniques are prone to interfering compounds, such as mercaptans and sulfides, this method uses a column separation technique to separate these and other compounds in the sample. Anyone with GC experience can quickly set up and run this method. Those without GC experience are easily trained by the Shimadzu Scientific Instruments service and tech support team.
Moisture Analysis by GC/BID offers the following advantages:
- Easily analyzes both liquid and gas samples
- Uses a variety of Watercol™ GC columns depending on your matrices
- Uses a simple, high sensitivity, and very stable low cost GC detector
The Barrier Discharge Ionization Detector (BID)
The BID achieves over 200 X's higher sensitivity for organic compounds over a TCD. In addition, conventional analytical techniques require a GC system configuration with multiple detection schemes to analyze for permanent gases and light hydrocarbons. The use of a methanizer and FID is often required to detect ppm levels of CO and CO2. However, the BID replaces all of this hardware and allows for the highly sensitive detection of mixtures of inorganic gases and light hydrocarbons.
New ASTM Work Item - Precursor to an ASTM Standard Method
A new test method work item (WK59649): A New Standard Test Method for the Determination of Water in Liquefied Petroleum Gas (LPG) using Gas Chromatography and Barrier Discharge Ionization Detection (BID) has been submitted by the ASTM D02 H00 committee. This method uses the new GC/BID/Liquid/gas sampling valve with the Watercol™ (MilliporeSigma*) GC column. Be on the lookout for the official method once it is approved by ASTM.
Moisture Analysis in Many Types of Petroleum Samples
a - Standard addition with Aerosol-OT dissolved in moisture
b - Standard addition is not feasible due to the samples high viscosity, complexity of samples and immiscibility with the added moisture standard
c - Moisture measured in a 0.5g sample utilizing headspace gas chromatography
Many different types of samples can benefit from analyzing moisture content via the GC/BID Watercol™. Excellent precision and accuracy are achieved using manual or automated systems. Depending on the types of samples, a liquid/gas sampling valve can be used to introduce the samples to the GC or the Shimadzu HS-20 Headspace Autosampler.
* MilliporeSigma, the life science business of Merck KGaA
Watercol is a trademark of MilliporeSigma.