🌿 Determination of total nitrogen in soil by dry combustion (elemental analysis) — sample pretreated according to ISO 11464, fraction < 2 mm, heating in oxygen at at least 900 °C, conversion of all nitrogen forms into N2 and measurement with a thermal conductivity detector, calibration with a substance of known nitrogen content, conversion to dry matter according to ISO 11465, PN-ISO 13878

Environment PN-ISO 13878

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST ISO 13878:1999 (text of ISO 13878:1998, English): from the title page through the foreword and Clauses 1–9 (with Table 1) to Clause 10 (test report) on page 3 inclusive. Outside the sample remain only the informative Annexes A and B and the bibliography.

ACCORDING TO THE TEXT OF ISO 13878:1998. The standard was prepared by ISO/TC 190 “Soil quality”, subcommittee SC 3; first edition of 15.03.1998; Annexes A and B are informative. Scope (1): method for the determination of the total nitrogen of soil after dry combustion, for all types of soil; according to the note the method was developed originally as a manual method by Dumas, and its applicability is improved greatly by modern automated equipment. Normative references (2): ISO 11464:1994 (pretreatment of samples for physico-chemical analyses) and ISO 11465:1993 (dry matter and water content, gravimetric method). Principle (3): soil pretreated according to ISO 11464 is heated to at least 900 °C in the presence of oxygen; mineral and organic nitrogen compounds are oxidized and/or volatilized, the combustion products are nitrogen oxides (NOx) and molecular nitrogen (N2); after transforming all nitrogen forms into N2, total nitrogen is measured by thermal conductivity. Reagents (4): reagents of recognized analytical grade; combustion gas — oxygen (special requirements according to the apparatus manual); chemicals or catalysts for reduction, oxidation, removal or fixing of interfering combustion gases; calibration substances, e.g. acetanilide (C8H9NO), L-aspartic acid (C4H7NO4), amino acids of known composition or soils with certified nitrogen content — the nitrogen content of the calibration substance should be as similar as possible to that of the soil. Apparatus (5): analytical balance accurate to 0,1 mg or microbalance 0,01 mg; combustion apparatus operating at at least 900 °C with a detector for the nitrogen formed (according to the manufacturer’s manual); crucibles of various sizes, e.g. 10 ml or 20 ml. Laboratory sample (6): the soil is pretreated according to ISO 11464 and the fraction of particles < 2 mm is used; the same fraction is used to determine water according to ISO 11465; if less than 2 g of soil is required, a representative subsample is milled further to pass a sieve of the aperture given in the manufacturer’s manual, and sufficient milling is checked by comparing the results of multiple analyses (Clause 9); according to the note the appropriate particle size depends primarily on the homogeneity of distribution and composition of soil organic matter. Procedure (7): the apparatus is calibrated according to the manual with one of the substances of 4.3, with a nitrogen content similar to the sample; the sample mass depends on the expected nitrogen content and the apparatus, m1 g of the air-dried sample is weighed into a crucible and analysed according to the manual; the primary result is normally given in milligrams of nitrogen (X1) or as a mass fraction of nitrogen in percent (X2) referred to the mass of air-dry soil; according to the note soil pores are filled with air, and therefore nitrogen, and nitrogen can also enter the combustion cell during sample exchange — both can lead to overestimation, so sufficient purging with oxygen should be carried out before combustion. Calculation (8): nitrogen content wN in mg/g of oven-dry soil: wN = X1/m1 × (100 + w)/100 for a result in mg or wN = X2 × 10 × (100 + w)/100 for a result in percent, where w — water content in percent (mass fraction) on the basis of oven-dried soil according to ISO 11465; the result is rounded to two significant figures. Repeatability (9, Table 1): two separate consecutive measurements shall differ by not more than 10 % relative at a content ≤ 2,0 mg/g and 5 % relative at > 2,0 mg/g. Report (10): reference to the standard, sample identification, results in mg nitrogen per gram of sample, operations not specified or optional and factors affecting the result.

STATUS (as of 03.10.2026). The PKN search (term “PN-ISO 13878”, 03.10.2026) shows PN-ISO 13878:2002 (Polish version, “Introduces: ISO 13878:1998 [IDT]”) without a withdrawal note; the other results are PN-EN 13878 on caravan vehicles — a different document with the same number. In the iTeh catalogue (read on 03.10.2026) ISO 13878:1998 has the status “Published”, stage 90.93 (standard confirmed) since 05.03.2026. Kjeldahl nitrogen is described in a separate entry on PN-ISO 11261, organic and total carbon after dry combustion in the entry on PN-ISO 10694, dry matter and water in the entry on PN-ISO 11465.

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 13878 appears in 5 records at 5 laboratories: AB 339, AB 696, AB 740, AB 945, AB 1656. In the current PCA documents (read on 03.10.2026, issues from 19.08.2024 to 22.07.2026) the number appears in 5 rows — one at each; in each of the five 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). Everywhere the form “PN-ISO 13878:2002”. None of these items is suspended; the AB 339 document has a footnote on suspension of part of the scope marked in bold italics, but the row with PN-ISO 13878 is not so marked. The “Laboratories” tab (term “PN-ISO 13878”) 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). Soil (AB 696, AB 740, AB 945, AB 1656), mineral soils (AB 339). Characteristic: total nitrogen content (AB 945, AB 1656; at AB 696 “after dry combustion”), general nitrogen (AB 740), nitrogen (AB 339). Technique: high-temperature combustion with TCD detection (AB 740, AB 945) or TC (AB 339, AB 1656), thermal conductivity method TCD (AB 696). Ranges: (0,01–1,0) % (AB 696), (0,02–4,00) % (AB 945), (0,100–1,400) % (AB 1656), (0,10–5,00) % (AB 339), (0,1–30,0) g/kg (AB 740). The standard expresses the result in mg/g; the laboratories give percent or g/kg.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the sample: fraction < 2 mm according to ISO 11464; with a portion below 2 g — further milling and checking by replicate results (6). With nitrogen from air: soil pores and opening the cell introduce N2 and overestimate the result — the system should be purged with oxygen before combustion (7.2, note). With calibration: a calibration substance with nitrogen content close to the sample (4.3, 7.1). With conversion: the primary result refers to air-dry soil, the final one to dry matter with water according to ISO 11465 (8). With rounding: two significant figures (8). With replicates: permitted difference 10 % relative up to 2,0 mg/g and 5 % above (9). With searching: not to be confused with PN-EN 13878 (caravan vehicles).

WHAT WE DO NOT GIVE. We did not read the informative Annexes A and B. We do not give parameters of particular analysers (temperatures, catalysts, purging times) — the standard refers to the manufacturer’s manual.

Method principle

A portion of air-dried soil (fraction < 2 mm) is burned in a stream of oxygen at at least 900 °C; nitrogen compounds are oxidized or volatilized, nitrogen oxides are converted into N2, and its amount is measured by a thermal conductivity detector. The apparatus is calibrated with a substance of known, similar nitrogen content, the system is purged with oxygen before combustion, and the result is converted to dry matter from the water content according to ISO 11465 and reported in mg/g to two significant figures.

Applications

• Soils of all types — total nitrogen (1)
• Replacing the manual Dumas method by automatic elemental analysers (1, note)
• Soil and mineral soils — total and general nitrogen in the accreditation scopes of 5 laboratories in PCA

Key parameters

Standard

Standard number

PN-ISO 13878:2002

Title (PL)

Jakość gleby — Oznaczanie zawartości azotu całkowitego po suchym spalaniu („analiza elementarna”)

Title (EN)

Soil quality — Determination of total nitrogen content by dry combustion (“elemental analysis”)

Step-by-step procedure

1. Sample preparation

   According to ISO 11464, fraction < 2 mm; the same fraction for water according to ISO 11465 (6). PN-ISO 13878:2002 without a withdrawal note (03.10.2026).

2. Calibration

   With a calibration substance of nitrogen content close to the sample, according to the apparatus manual (7.1).

3. Test portion

   m1 g of air-dried sample into a crucible, mass chosen for the expected nitrogen content (7.2).

4. Combustion and measurement

   Purging with oxygen before combustion; combustion at ≥ 900 °C, measurement of N2 by thermal conductivity (3, 7.2).

5. Result

   wN in mg/g dry matter with correction for water w; two significant figures; replicates according to Table 1 (8, 9).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Oxygen under pressure and furnace at ≥ 900 °C — fire and burn risk
• Soil dust during milling — respiratory protection

Frequently asked questions