GB/T 42955-2023Determination of total nitrogen content for fertilizers—Dumas combustion method (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

1 Scope

This document describes the Dumas combustion method for the determination of total nitrogen content in fertilizers.

This document applies to the determination of total nitrogen content in fertilizers.

This document does not apply to the determination of total nitrogen in ammonium bicarbonate.

Note: When the sample amount is 100 mg, the detection limit of this document is 0.02%.

2 Normative reference documents

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, the dated quotations For undated referenced documents, only the version corresponding to that date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to this document.

GB/T 8170 Numerical rounding rules and representation and determination of limit values

NY/T 887 Determination of density of liquid fertilizer

3 Terms and definitions

There are no terms or definitions to be defined in this document.

4 Principles

In an oxygen-rich environment, after the sample is heated and burned in the combustion tube, the nitrogen-containing substances are converted into NOx, and the resulting interference components are absorbed The NOx is removed by the reducing agent, and NOx is quantitatively converted into molecular nitrogen under the action of the reducing agent. After being detected by the thermal conductivity detector, the total nitrogen content of the sample is obtained.

5 Reagents or materials

Unless otherwise stated, the reagents used in this document are nitrogen-free, analytically pure reagents.

5.1 Helium (He). purity not less than 99.99%.

5.2 Carbon dioxide (CO2). purity not less than 99.99%.

5.3 Oxygen (O2). purity not less than 99.99%.

5.4 Standard material. glycine (CAS number. 56-40-6) or aspartic acid (CAS number. 56-84-8) or nicotinamide (CAS number. 98-92-0) or niacin (CAS number. 59-67-6) or ethylenediaminetetraacetic acid (CAS number. 60-00-4), with a purity of not less than 99%.

5.5 Combustion aid. sucrose, cellulose and other nitrogen-free sugar reagents.

5.6 Reducing agent. copper or tungsten.

5.7 Adsorbent. aluminum trioxide, phosphorus pentoxide, magnesium perchlorate, sodium carbonate.

5.8 Water absorbing agent. magnesium oxide.

6 Instruments and Equipment

6.1 Dumas nitrogen analyzer. equipped with a thermal conductivity detector.