🔬 UV Absorbance at 254 nm

Physicochemistry PN-EN ISO 7887

Overview

STATUS (as of 29.10.2026). PN-EN ISO 7887:2012 — Polish version, published on 06.02.2015, adopts EN ISO 7887:2011 [IDT] and ISO 7887:2011 [IDT]; it replaced PN-EN ISO 7887:2002; it has the national correction PN-EN ISO 7887:2012/Ap1:2015-06 (approved on 08.06.2015), which in Annex A (internal quality control), A.3.1, replaces “92 g of humic acid” with “92 mg of humic acid”. The standard is current — no withdrawal note. It is a standard on the COLOUR of water: four methods A–D — A: visual examination of the apparent colour of the sample in a bottle, B: true colour measured with optical instruments at 436 nm and at 525 nm and 620 nm, C: true colour at 410 nm compared with the hexachloroplatinate concentration, D: visual comparison with hexachloroplatinate standard solutions (clause 1). The standard does not describe the measurement at 254 nm — it only mentions, in a note to the definition of dissolved organic carbon (3.3), that the ratio of UV absorbance to dissolved organic carbon concentration (specific UV absorbance, SUVA) has proved useful for optimizing water treatment processes. The measurement procedure is given according to the methods that describe it: Standard Methods 5910 B and EPA 415.3 (in the summaries of the US method registry NEMI), the description of method 5910 B in the test catalogue of the Virginia state laboratory (DCLS) and the German standard DIN 38404-3:2005-07 (according to the publisher’s description).

WHAT THE MEASUREMENT MEASURES. Organic compounds absorbing UV radiation absorb it in proportion to their concentration; absorbance is measured at 253.7 nm after filtering the sample, which limits the effect of particles (SM 5910 B). The spectral absorption coefficient measured at 254 nm can be used for the summary determination of dissolved organic water constituents, especially when their qualitative composition does not change strongly; the measurement detects many organic compounds, but not, for example, short-chain aliphatic compounds, pure alcohols or pure sugars (DIN 38404-3, publisher’s description). It is a non-specific measurement — the minimum detectable concentration cannot be determined rigorously, because it depends on the relationship between UV absorbance and the characteristic of interest (e.g. trihalomethane formation potential or dissolved organic carbon) and on interfering substances (SM 5910 B).

INTERFERENCES. The main interferences are colloidal particles, UV-absorbing organic compounds other than those of interest and UV-absorbing inorganic compounds — notably iron(II), nitrate, nitrite and bromide; certain oxidants and reducing agents also absorb radiation at 253.7 nm: ozone, chlorate, chlorite, chloramines and thiosulfate (SM 5910 B). If the sample also contains undissolved substances, the measurement gives the spectral attenuation coefficient instead of the spectral absorption coefficient (DIN 38404-3, publisher’s description).

SUVA. The specific UV absorbance is calculated by dividing the UV absorbance at 254 nm by the dissolved organic carbon concentration and multiplying by a unit conversion factor (EPA 415.3, 12.2). Method EPA 415.3 covers total and dissolved organic carbon, UV absorbance at 254 nm and SUVA in source waters and in drinking water.

REGULATIONS. The regulation on the quality of water intended for human consumption sets no value for UV absorbance (Journal of Laws 2026, item 748, Annex 1).

WHAT WE DO NOT GIVE HERE. We did not have the full texts of Standard Methods 5910 B, EPA 415.3 or DIN 38404-3 — so we do not give the optical path length of the cell, the bandwidth, the requirements for standards and instrument checks, the numerical SUVA formula or the acceptance criteria for replicates.

Method principle

Ultraviolet radiation of wavelength 254 nm passes through a quartz cell containing a representative water sample (DCLS, SM 5910 B). Before measurement the sample is filtered through a 0.45 µm filter to limit the effect of particles (EPA 415.3, SM 5910 B). UV-absorbing organic compounds — many compounds, except among others short-chain aliphatic compounds, pure alcohols and sugars — attenuate the radiation in proportion to their concentration, so the absorbance at 254 nm is a summary, non-specific measure of dissolved organic matter (SM 5910 B, DIN 38404-3).

Applications

• Summary assessment of dissolved organic water constituents, especially with a qualitative composition that changes little (DIN 38404-3, publisher’s description)
• Source waters and drinking water — UV absorbance at 254 nm and SUVA together with total and dissolved organic carbon (EPA 415.3)
• Optimization of water treatment processes on the basis of SUVA (PN-EN ISO 7887, note to 3.3)
• Water and wastewater — UV-absorbing organic constituents (SM 5910 B)

Key parameters

Standard

Standard number

PN-EN ISO 7887:2012

Title (PL)

Jakość wody — Badanie i oznaczanie barwy

Title (EN)

Water quality — Examination and determination of colour

Step-by-step procedure

1. Sampling and transport

   Collect samples in glass bottles, ship them packed in ice or frozen gel packs (EPA 415.3); at DCLS — amber glass bottles, washed, rinsed with organic-free water and baked at 400 °C for 1 h.

2. pH (optional)

   For specific applications and correlations the pH may be adjusted with hydrochloric acid or NaOH, in poorly buffered samples with a non-UV-absorbing buffer, e.g. phosphate; after adjusting or measuring the pH, the sample is filtered (SM 5910 B). Samples for SUVA are not adjusted (DCLS).

3. Preparing the filter

   Wash the filter and the filtration assembly with at least 50 ml of organic-free water (SM 5910 B).

4. Filtration

   Filter the sample through a 0.45 µm filter (EPA 415.3, SM 5910 B); store the filtered sample below 6 °C, not acidified, and analyse within 48 h of collection (EPA 415.3).

5. Measurement

   Measure the absorbance of the filtered sample at 254 nm (253.7 nm) in a quartz cell (EPA 415.3, SM 5910 B, DCLS).

6. Replicates

   Measure at least two portions of filtered sample; analyse every tenth sample in duplicate to assess precision (SM 5910 B).

7. SUVA (optional)

   When the dissolved organic carbon of the same sample is known — SUVA = UV absorbance at 254 nm / dissolved organic carbon × unit conversion factor (EPA 415.3, 12.2). If interference is suspected (iron, nitrate, nitrite, bromide), flag the result (EPA 415.3).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Persons using the standard should be familiar with normal laboratory practice; the standard does not address all safety problems — establishing safety and health practices and compliance with national regulations is the responsibility of the user (warning of PN-EN ISO 7887)
• Tests should be carried out by suitably qualified staff (warning of PN-EN ISO 7887)

Frequently asked questions