Water Analysis via Gas Chromatography/BID in Petroleum and Petroleum Products

Oil Rig and Tanker

Water, Water, Everywhere

Water can have a deleterious effect on many petroleum products. Thus, measuring water content accurately and precisely is critical to the performance of products, as well as infrastructure and product integrity (i.e., pipelines).

Water in petrochemical feedstocks can cause pipelines and valves to freeze, as well as poison any catalysts used in the process of the petroleum feedstock. These problems cost the petrochemical industry millions of dollars per year. So analyzing for water and how much of it is critical.

One popular method used to analyze for water is Karl Fisher Titration (KFT), a very selective method to analyze for water. KFT has a wide dynamic range but has difficulty in measuring relatively low amounts of water. When calculating for "ball park" numbers, KFT is sufficient in many cases. However there are many disadvantages using this technique. Problems such as; high drift, side reactions (i.e., mercaptan/thiols compounds in Liquid Petroleum Gas [LPG]), poor accuracy, low solubility of samples in methanol, and technician-dependent data can cause erroneous answers.

New Approach Using Gas Chromatography with the Novel BID

Unlike traditional wet chemistry methods, this new method uses traditional 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 Thermal Conductivity Detector (TCD) and a Flame Ionization Detector (FID) and can analyze down to sub-ppm levels of water. Additionally the method uses the new, highly polar ionic liquid column, WatercolTM (Supleco) 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 out 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.

Water Analysis by GC/BID offers the following advantages:

  1. Easily analyzes both liquid and gas samples

  2. Uses a variety of WatercolTM GC columns depending on your matrices

  3. Uses a simple, high sensitivity, and very stable low cost GC detector

The Barrier Discharge Ionization Detector (BID)

Low temperature plasma from 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 WatercolTM (Supleco) GC column. Be on the lookout for the official method once it is approved by ASTM.

Water in LPG Standard via liquid sampling valve (2uL injection 1:5 split)
Water in LPG Standard via liquid sampling valve (2uL injection 1:5 split)

Water Analysis in Many Types of Petroleum Samples

Petroleum product samples analyzed for water via GC/BID
(Lillian A. Frink; Daniel W. Armstrong, 8194-8201; Anal. Chem. 2016, 88)

a - Standard addition with Aerosol-OT dissolved in water
b - Standard addition is not feasible due to the samples high viscosity, complexity of samples and immiscibility with the added water standard
c - Water measured in a 0.5g sample utilizing headspace gas chromatography

Many different types of samples can benefit from analyzing water content via the GC/BID WatercolTM. 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 HS20 Headspace Autosampler.

Click to contact a sales representative for a product quote

Analysis of Trace Water in Petroleum Products by GC