🔥 Determination of sulfur content in liquid, homogeneous automotive fuels (diesel with FAME up to about 30 %, gasoline with ethanol up to about 10 %, HVO and GTL) by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) — measurement of the count rates of the S K-L2,3 line and background, calibration curve x = a + b R0 + c R0² from solutions of dibutylsulfide or dibutyldisulfide in white oil (for pure FAME — in methyl oleate), ranges 5–60 and 60–500 mg/kg, polychromatic or monochromatic excitation, PN-EN ISO 20884

Petrochemistry PN-EN ISO 20884

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in two iTeh samples: SIST EN ISO 20884:2019 (title page) and ISO 20884:2019 (English text) — from the title page through the contents, foreword and Clauses 1–9 to 10.2 (measurement of calibration solutions, Formulae 1–3) on page 5 inclusive. Outside the sample remain checking of the calibration (10.3–10.4), the procedure for the ranges 5–60 and 60–500 mg/kg (11), expression of results (12), precision (13), test report (14) and Annex A (good practices). We did not read amendment A1:2021; according to the iTeh card it adds the SSD detector in the monochromatic excitation part of Table 1.

ACCORDING TO THE TEXT OF ISO 20884:2019 (foreword, Clauses 1–10.2). The standard was prepared by ISO/TC 28 “Petroleum and related products, fuels”; the third edition replaced ISO 20884:2011; main changes: extension of the scope to hydrotreated vegetable oil (HVO) and the synthetic fuel GTL (“gas to liquid”) and procedural steps for instruments with monochromatic excitation. Scope (1): WDXRF method for sulfur in liquid, homogeneous automotive fuels from 5 mg/kg to 500 mg/kg, with a maximum oxygen content of 3,7 % (m/m): diesel fuels with up to about 30 % (V/V) FAME, gasolines with up to about 10 % (V/V) ethanol, synthetic fuels HVO and GTL with sulfur contents of 5–45 mg/kg; products with higher oxygen content show significant matrix effects, e.g. pure FAME, which can nevertheless be analysed when the corresponding procedures are followed (5.3); other products can be analysed, but precision has not been established for them; contents above 500 mg/kg can be determined after dilution, without established precision. Normative references (2): ISO 3170 and ISO 3171 (manual and automatic sampling of petroleum liquids). No terms are defined (3). Principle (4): the sample in a cell is exposed to the primary radiation of an X-ray tube, the count rates of the S K-L2,3 X-ray fluorescence and, where required, of the background radiation are measured, and the sulfur content is determined from the calibration curve for the relevant range; the standard uses the IUPAC notation (S K-L2,3) instead of the Siegbahn notation (S Kα) being phased out. Reagents (5): dibutylsulfide of nominal sulfur content 21,92 % (m/m) or dibutyldisulfide 35,95 % (m/m) as calibrating substance — care should be taken due to volatility; certified reference materials according to ISO 17034 are suitable alternatives; white oil (paraffinum perliquidum) as blank solution with sulfur below 1 mg/kg, checked in the spectrometer before use — a sulfur signal shall not be detectable; methyl oleate as blank solution for pure FAME (sulfur < 1 mg/kg, intensity below that equivalent to 1 mg/kg); other oxygen-containing, sulfur-free blank solutions, e.g. octanol, can also be used. Apparatus (6, Table 1): WDXRF spectrometer measuring the count rates of S K-L2,3 and background; with monochromatic excitation the background is inherently low and its measurement is not mandatory; minimum requirements — rhodium, scandium or chromium anode (monochromatic also titanium), voltage not less than 30 kV, current not less than 50 mA (polychromatic) or 0,1 mA (monochromatic), lower-power polychromatic systems being permitted if validated to the precision of Clause 13; coarse collimator or monochromator; germanium, pentaerythrite or graphite analysing crystal; optical path in vacuum or helium (in vacuum the sample separated by a secondary window); sample cup window of polyester film of at most 4 µm — polycarbonate may dissolve in very aromatic samples, and some films contain traces of silicon, calcium and sulfur, so samples, standards and blanks are measured with the same batch of film; proportional counter with pulse-height analyser (polychromatic) or with single channel analyser (monochromatic); wavelengths — S K-L2,3 0,537 3 nm, background 0,545 nm; analytical balance to the nearest 0,1 mg. Sampling (7): according to ISO 3170 or ISO 3171, unless otherwise specified. Calibration solutions (8): blank — white oil, for pure FAME the solution of 5.3 to minimize matrix effects; stock solution — calibrating substance weighed to 0,1 mg and diluted with blank solution at room temperature to about 1 000 mg/kg sulfur known to the nearest 1 mg/kg; calibration solutions by weighing the stock solution and diluting, contents rounded to 0,1 mg/kg — low range (Table 2): 0; 5,0; 10,0; 25,0; 50,0 mg/kg, high range (Table 3): 0; 50,0; 100,0; 200,0; 350,0; 500,0 mg/kg; Table 2 solutions have limited stability and shall be used on the day of preparation, Table 3 solutions are stable for no more than one week in a cool place (refrigerator). Settings (9): parameters according to Table 1; the spectrometer is optimized according to the manufacturer’s specifications for the best signal-to-noise ratio, the 50 mg/kg solution being recommended; for polychromatic excitation the counting time is set so that the total net count from the 50 mg/kg solution is at least 40 000, and the same time is used for calibration and measurement; before a series, and at least once daily, the spectrometer is checked according to the manufacturer’s specifications. Calibration (10.1–10.2): separate calibrations for 5–60 and 60–500 mg/kg; all solutions of the range are measured consecutively in ascending order; count rates IS at 0,537 3 nm and IB at 0,545 nm are measured consecutively (with monochromatic excitation background is not required); the minimum sample volume is determined by starting with 1 ml and adding liquid until the net count rate stops increasing — too little sample gives a low result or evaporation effects, too much causes sagging of the window, especially with aromatic samples; typically 5 g in a 28 mm cup or 10 g in 40 mm (polychromatic), 0,8 g in 20 mm or 4 g in 42,9 mm (monochromatic); R0 = IS − IB when background is measured or R0 = IS for monochromatic excitation without background; curve x = a + b R0 + c R0², and parameter c can be zero where the curve has been shown to be linear.

STATUS (as of 03.10.2026). The PKN search (term “PN-EN ISO 20884”, 03.10.2026) shows PN-EN ISO 20884:2020-03 in the Polish and English version (“Introduces: EN ISO 20884:2019 [IDT], ISO 20884:2019 [IDT]”) without a withdrawal note, the additional element PN-EN ISO 20884:2020-03/A1:2022-03 in the Polish and English version (“Introduces: EN ISO 20884:2019/A1:2021”) and the withdrawn editions 2012, 2011, 2006 and 2005. In the iTeh catalogue (read on 03.10.2026) ISO 20884:2019 has the status “Published” and amendment Amd 1:2021 (“Addition of the SSD detector to the Monochromatic excitation part of Table 1”); SIST EN ISO 20884:2019 is linked to Directive 98/70/EC on fuel quality. Sulfur by ultraviolet fluorescence is described in a separate entry on PN-EN ISO 20846, and by energy-dispersive X-ray spectrometry in the entry on PN-EN ISO 8754.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 03.10.2026). The number 20884 appears in 5 records at 5 laboratories: AB 297, AB 391, AB 474, AB 484, AB 1278. In the current PCA documents (read on 03.10.2026, issues from 22.01.2026 to 30.07.2026) the number appears in 4 items (AB 297, AB 391, AB 484, AB 1278, one each; 5 text lines, because at AB 391 the standard and amendment A1 are on separate lines); the BIP page of AB 474 has no link to a scope document, so AB 474 is described only from the database copy. In each of the four documents the number of page markers equals the number of PDF pages, without repetitions; a search of all 1291 PCA documents downloaded from BIP on 03.10.2026 found no laboratories outside the database copy (17 laboratories on the list have no link to a scope document on BIP). The form “PN-EN ISO 20884:2020-03 +A1:2022-03” (AB 484; at AB 297 “z wyłączeniem punktu 7” — excluding point 7, sampling), “PN-EN ISO 20884:2020-03” and “PN-EN ISO 20884:2020-03/A1:2022-03” (AB 391), “PN-EN ISO 20884:2020 +A1:2022-03” (AB 474 in the database copy) and “PN-EN ISO 20884” without year (AB 1278, flexible scope “E”). None of these items is suspended; the AB 484 document has a footnote on suspension of part of the scope marked in bold italics, but the row with PN-EN ISO 20884 is not so marked. The “Laboratories” tab (term “PN-EN ISO 20884”) shows all 5 laboratories — checked with a tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA and in the database copy). Liquid fuels: unleaded gasolines, diesel fuels, light heating oil (AB 297, AB 391, AB 474, AB 484, AB 1278), and also aviation gasoline, kerosene, aviation turbine fuel, marine fuel, FAME biofuels (at some laboratories); other petroleum products — gasoline components, fractions boiling at 30–350 °C (AB 484), petroleum distillates (AB 474, AB 1278), paraffins and slack wax, as well as lubricants — base oils, engine, industrial and used oils (AB 474). Characteristic: sulfur content, wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF). Ranges: (5,0–500) mg/kg (AB 297, AB 474, AB 1278), (5,0–50,0) mg/kg (AB 391), (20,0–500) mg/kg (AB 484). Lubricating oils, paraffins and distillates are outside the scope of the standard (automotive fuels); the standard allows other products to be analysed, but without established precision.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the matrix: oxygen above 3,7 % (m/m) gives matrix effects — pure FAME is analysed with a methyl oleate blank (1, 5.3, 8.1). With the film: at most 4 µm, polyester instead of polycarbonate for aromatic samples, and samples, standards and blanks on film of the same batch (Table 1, footnote c). With standards: low range used on the day of preparation, high range at most one week in the refrigerator (8.4); the calibrating substance is volatile (5.1). With volume: too little sample lowers the result, too much makes the window sag — determine the minimum volume (10.2). With ranges: separate curves for 5–60 and 60–500 mg/kg (10.1). With counts: ≥ 40 000 net counts from the 50 mg/kg solution for polychromatic excitation, the same time for standards and samples (9.2). With dilution: above 500 mg/kg dilution is possible, but without established precision (1, Note 1).

WHAT WE DO NOT GIVE. We did not read the checking of the curve, the measurement procedure for samples, the calculation of the result, repeatability and reproducibility, the report form or the good practices of Annex A (10.3–14). We do not know the content of amendment A1:2021 beyond the description on the iTeh card. Nor do we give sulfur requirements from product standards.

Method principle

The fuel sample in a cup with polyester film is irradiated by an X-ray tube; a wavelength-dispersive spectrometer measures the count rate of the S K-L2,3 line at 0,537 3 nm and of the background at 0,545 nm (with monochromatic excitation the background can be omitted). The net count rate R0 is converted to sulfur content from the curve x = a + b R0 + c R0², prepared separately for 5–60 and 60–500 mg/kg from solutions of dibutylsulfide or dibutyldisulfide in white oil.

Applications

• Diesel fuels with FAME up to about 30 % (V/V), gasolines with ethanol up to about 10 % (V/V), HVO and GTL — sulfur 5–500 mg/kg (1)
• Pure FAME — with a methyl oleate blank solution (1, 5.3)
• Liquid fuels, petroleum products and lubricants — WD-XRF sulfur content in the accreditation scopes of 5 laboratories

Key parameters

Standard

Standard number

PN-EN ISO 20884:2020-03

Title (PL)

Przetwory naftowe — Oznaczanie zawartości siarki w paliwach do pojazdów samochodowych — Rentgenowska spektrometria fluorescencyjna z dyspersją fali

Title (EN)

Petroleum products — Determination of sulfur content of automotive fuels — Wavelength-dispersive X-ray fluorescence spectrometry

Step-by-step procedure

1. Calibration solutions

   Stock solution about 1 000 mg/kg, dilutions according to Table 2 or 3; low range on the same day (8). PN-EN ISO 20884:2020-03 without a withdrawal note (03.10.2026).

2. Optimization and check

   Spectrometer according to the manufacturer, ≥ 40 000 net counts from 50 mg/kg (polychr.); check before a series, at least once daily (9).

3. Sample volume

   From 1 ml, adding to constant net count rate; volume above the flattening point (10.2).

4. Calibration

   Separately 5–60 and 60–500 mg/kg; measurement in ascending order of IS and IB; R0 and regression x = a + b R0 + c R0² (10.1, 10.2).

5. Measuring samples

   According to Clause 11 for the relevant range; calculation and precision according to Clauses 12–13 (not read).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• X-radiation — operate only with the instrument shielding closed
• Fuels and volatile sulfur compounds — flammable, work in a fume hood

Frequently asked questions