ISO/PRF 25095-2

ISO/DISPRF 25095-2:2025(en)
ISO/TC 47
Secretariat: JISC
Date: 2025-122026-01-13
Propylene oxide for industrial use – —
Part 2:
Determination of aldehydes by liquid chromatography
PROOF
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ISO/DISPRF 25095-2:20252026(en)
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and materials . 2
6 Apparatus . 3
7 Sampling . 3
8 Procedure . 3
9 Calculation and expression of results . 4
10 Precision . 5
11 Test report . 5
Annex A (informative) Blank test and purification of 2, 4-dinitrophenylhydrazine (DNPH) . 7
Annex B (informative) Representative chromatogram for aldehyde derivatives . 8

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Foreword
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Field Code Changed
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DRAFT International Standard ISO/DIS 25095-2:2025(en)

Propylene oxide for industrial use – —
Part 2:
Determination of aldehydes by liquid chromatography
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all the safety problems, if any, associated with its use. It is the
responsibility of the user to establish appropriate safety and health practices.

1 Scope
This document specifies a test method for determination of aldehydes in propylene oxide by liquid
chromatography.
This document is applicable to the determination of aldehydes in propylene oxide for industrial use, including
formaldehyde, acetaldehyde, propionaldehyde and acrolein. The concentration for each aldehyde ranges from
0,5 mg/kg to 100 mg/kg.
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 edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3165:1976, Sampling of chemical products for industrial use — Safety in sampling
ISO 3170:2025, Hydrocarbon liquids—Liquids — Manual sampling
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353--2, Reagents for chemical analysis — Part 2: Specifications — First series
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
4 Principle
A certain volume of the sample is reacted with excessive 2, 4-dinitrophenylhydrazine (hereafter referred to
as DNPH) in acidic buffer solution at 40 °C, in which the aldehydes (such as formaldehyde, acetaldehyde,
propionaldehyde, acrolein, and so on) and ketones (such as acetone) are converted into the corresponding
aldehydes-DNPH or ketones-DNPH (such as formaldehyde-DNPH, acetaldehyde-DNPH, propionaldehyde-
DNPH, acrolein-DNPH, acetone-DNPH, and so on). The reacted sample solution is injected into liquid
chromatograph to separate each component, which is detected by ultraviolet detector or diode array detector
and quantified by external standard method.
5 Reagents and materials
Unless otherwise specified, use only reagents of recognized analytical grade.
The standard solutions, impurity standard solutions, preparations and products used in the test method shall
be prepared in accordance with ISO 6353-2 when no other requirements are specified.
5.1 5.1 Water, in accordance with grade I as defined in ISO 3696. Dissolved gas needs to be removed
by ultrasound before use.
11)
5.2 5.2 Acetonitrile, CAS No. 75-05-8, chromatographically pure.
5.3 5.3 DNPH, CAS No. 119-26-6, with mass fraction no less than 99 % and the concentration of each
aldehyde-DNPH is no more than 5 mg/kg (calculated as the correspondent aldehydes). Purify it according to
Annex AAnnex A if necessary. Store it in a cool environment.
5.4 5.4 Sodium citrate dihydrate, CAS No. 6132-04-3.
5.5 5.5 Anhydrous citric acid, CAS No. 77-92-9.
5.6 5.6 Hydrochloric acid, 5 mol/L.
5.7 5.7 Sodium hydroxide, 200 g/L.
5.8 5.8 DNPH solution, 0,6 g/L. Dissolve 0,6 g DNPH in 1 L acetonitrile.
5.9 5.9 Citrate buffer solution, dissolve 38,5 g citric acid and 14,8 g sodium citrate dihydrate in 1 L
water, and adjust the pH value to the range of 2,9 to 3,3 using hydrochloric acid or sodium hydroxide.
5.10 5.10 Aldehyde-DNPH standard solution(s), commercially available with known mass
concentrations (mg/L) of aldehydes or aldehydes-DNPH. It should include four aldehydes-DNPH standard
solution(s) (formaldehyde-DNPH, acetaldehyde-DNPH, propionaldehyde-DNPH and acrolein-DNPH), and
usually use acetonitrile as solvent. Seal tightly and store in cool.
It is better to clarify the mass concentration (mg/L) of aldehydes in the above solution(s). If the labelled
concentration is expressed as aldehyde-DNPH, then it should be converted to the concentration of the
correspondent aldehyde. The conversion factors of formaldehyde, acetaldehyde, propionaldehyde and
...