GB/T 42333-2023Soil and stream sediment - Determination of iodine content - Pressurized ammonia extraction inductively coupled plasma mass spectrometry (English PDF)

Foreword

This document was issued on 17 March 2023 by the State Administration for Market Regulation; Standardization Administration of the PRC and takes effect on 1 July 2023.

It is a GB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

1 Scope

GB/T 42333-2023 describes the determination of iodine in soil and stream sediment by extraction with ammonia in a sealed vessel followed by inductively coupled plasma mass spectrometry. The sample is heated with dilute ammonia in a closed dissolver, which takes the iodine into solution, and the solution is then measured on an ICP-MS with iodine-127 as the measured isotope. The clauses run through the principle, the ambient and instrument conditions, the reagents and the grade of water, the instruments and equipment, sample preparation to a particle size below 74 µm after air drying, the test steps including duplicate blanks, the calculation of the result as a mass fraction in micrograms per gram, precision, accuracy, and the quality assurance and control that has to accompany a batch. The sealed alkaline route is the whole point of the method: iodine is volatile, an open acid digestion loses part of it before the sample ever reaches the instrument, and the result then comes out low without anything in the run showing that it has. An informative annex reports the statistics of the inter-laboratory trial. Written for geochemical survey and soil laboratories, and for the environmental and agricultural work in which soil iodine is mapped.

This document describes a method for the determination of iodine content in soil and

stream sediment by pressurized ammonia extraction inductively coupled plasma mass

spectrometry.

This document is applicable to the determination of iodine content in soil and steam

sediment with the method detection limit and measurement range as follows:

-- method detection limit 0.07 ug/g;

-- measurement range 0.23 ug/g ~ 100 ug/g.

2 Normative references

The following documents are referred to in the text in such a way that some or all of

their content constitutes requirements of this document. For dated references, only the

version corresponding to that date is applicable to this document; for undated references,

the latest version (including all amendments) is applicable to this document.

GB/T 6041, General rules for mass spectrometric analysis

GB/T 6379.2, Accuracy (trueness and precision) of measurement methods and

results - Part 2: Basic method for the determination of repeatability and

reproducibility of a standard measurement method

GB/T 6379.4, Accuracy (trueness and precision) of measurement methods and

results - Part 4: Basic methods for the determination of the trueness of a standard

measurement method

GB/T 6682, Water for analytical laboratory use - Specification and test methods

GB/T 14505-2010, Method for chemical analysis of rocks and ores - General rules

and regulations

GB/T 14506.1, Methods for chemical analysis of silicate rocks - Part 1:

Determination of hygroscopic water content

GB/T 33087, Ultra pure water for instrumental analysis specification and test

methods

JJF 1159, Calibration specification for quadrupole inductively coupled plasma mass

spectrometers

3 Terms and definitions

No terms and definitions need to be defined in this document.

4 Principle

The sample is heated with dilute ammonia in a sealed sample dissolver to extract iodine.

The sample solution is measured using an inductively coupled plasma mass

spectrometer and qualitatively determined by the iodine isotope 127I. Within a certain

concentration range, the iodine element mass spectrum count value is proportional to

the mass concentration of the iodine element. The iodine content in the sample is

calculated by measuring the iodine element mass spectrum count value.

5 Test conditions

The test conditions such as temperature, humidity, voltage and frequency during

inductively coupled plasma mass spectrometer detection shall comply with the relevant

requirements of GB/T 6041 and JJF 1159.

6 Reagents or materials

Unless otherwise stated, the reagents used in the analysis are analytical reagents, and

the water is grade-1 water specified in GB/T 6682 or high-purity water for instrumental

analysis specified in GB/T 33087.

6.1 Ammonia [omega(NH3) = 25% ~ 28%].

6.2 Ammonia solution (1+9).

6.3 Ammonia solution (1+99).

7.4 Centrifuge: the maximum speed is 10 000 r/min.

7.5 Sealed sample dissolver: stainless steel outer sleeve, polytetrafluoroethylene inner

tank, volume 15 mL.

7.6 Graduated test tube: 10 mL.