ASTM D5453
ASTM D5453 is a standard test method for determining total sulfur content in
liquid hydrocarbons, including light hydrocarbons, spark ignition engine fuels,
diesel engine fuels, and engine oils, using ultraviolet fluorescence (UVF)
detection. Accurate sulfur quantification is essential for quality control,
regulatory compliance, and environmental protection, as sulfur compounds
can lead to catalyst poisoning, affect product quality, and contribute to
pollution.
Scope and Applicability
This method applies to liquid hydrocarbons with boiling points between
approximately 25 °C and 400 °C and viscosities ranging from about 0.2 to
20 cSt at room temperature. It is suitable for samples containing total sulfur
concentrations from 1.0 mg/kg to 8,000 mg/kg. Applicable sample types
include naphthas, distillates, engine oils, ethanol, fatty acid methyl esters
(FAME), and various engine fuels such as gasoline (including ethanol blends
like E-85), diesel, biodiesel, diesel/biodiesel blends, and jet fuel.
Principle of Operation
In this method, a liquid hydrocarbon sample is introduced into a high-
temperature combustion furnace, where sulfur compounds are oxidized to
sulfur dioxide (SO₂). The combustion gases are then exposed to ultraviolet
(UV) light, causing the SO₂ to fluoresce. The intensity of this fluorescence is
directly proportional to the sulfur content in the sample and is measured by a
photomultiplier tube. This response is quantified and compared against
calibration standards to determine the total sulfur concentration.
Apparatus and Materials
1. Ultraviolet Fluorescence Analyzer: An instrument equipped with a
combustion furnace, UV excitation source, and fluorescence detector.
2. Sample Introduction System: Typically includes an automated liquid
sampler for precise injection of the sample into the combustion furnace.
3. Combustion Furnace: Operates at high temperatures (around 1,050 °C) to
ensure complete oxidation of sulfur compounds to SO₂.
4. Carrier Gas Supply: Inert gases such as helium or argon are used to
transport combustion products to the detector.
5. Calibration Standards: Certified reference materials with known sulfur
concentrations, prepared in a matrix similar to the samples being analyzed.
Sample Preparation
Homogenization: Ensure the sample is well-mixed to achieve uniform sulfur
distribution.
Sample Volume: Accurately measure the sample volume or mass to be
introduced into the analyzer, typically using a syringe or automated sampler.
Avoiding Contamination: Use clean equipment and containers to prevent
contamination that could affect sulfur measurements.
Calibration
Preparation of Calibration Standards: Prepare a series of calibration
standards with sulfur concentrations that bracket the expected sample
concentrations.
Calibration Curve: Analyze the calibration standards to establish a calibration
curve, plotting fluorescence intensity against sulfur concentration.
Verification: Regularly verify the calibration using quality control samples to
ensure accuracy over time.
Measurement Procedure
1. Instrument Setup: Configure the analyzer according to the manufacturer's
instructions, ensuring proper temperature settings and gas flows.
2. Sample Introduction: Introduce the prepared sample into the combustion
furnace using the sample introduction system.
3. Combustion and Detection: Allow the sample to combust, and measure the
resulting SO₂ fluorescence intensity.
4. Data Analysis: Calculate the sulfur concentration by comparing the
measured intensity to the calibration curve.
Uncertainty and Tolerance Limits
Limit of Detection (LOD): The method can detect sulfur concentrations as low
as 1.0 mg/kg.
Limit of Quantification (LOQ): Estimates of the pooled limit of quantification
(PLOQ) for the precision studies ranged between less than 1.0 mg/kg and less
than 5.0 mg/kg.
Precision: The method demonstrates good repeatability and reproducibility
across a wide range of sulfur concentrations. Specific precision data should
be referenced from the standard's precision and bias section.
Interference and Matrix Effects
Halogens: Samples containing less than 0.35% (m/m) halogens are suitable
for this method. Higher halogen content can interfere with the analysis.
Matrix Matching: Ensure calibration standards closely match the sample
matrix to minimize matrix effects and improve accuracy.
Quality Control and Maintenance
Routine Checks: Perform regular analyses of quality control samples to
monitor instrument performance and accuracy.
Maintenance: Regularly inspect and maintain the combustion furnace,
detectors, and sample introduction system to ensure optimal performance.
Software Updates: Keep the instrument's software updated to incorporate
the latest improvements in data processing and interference correction
algorithms.
Safety Considerations
High Temperatures: Exercise caution when working with the high-
temperature combustion furnace to prevent burns or fires.
Gas Handling: Ensure proper ventilation and handling procedures for carrier
and combustion gases to prevent asphyxiation or other hazards.
By adhering to the ASTM D5453 standard method, laboratories can achieve
accurate and reliable measurements of total sulfur in various liquid
hydrocarbons, supporting quality control and regulatory compliance efforts.
