🧪 Total arsenic in water and wastewater — spectrophotometry with DDTC-Ag

Physicochemistry PN-EN 26595

Overview

WHAT THIS STANDARD DESCRIBES. The scope from the PKN catalogue card, in full: "Opisano metodę oznaczania arsenu w wodzie i ściekach. Znajduje ona zastosowanie w granicach stężeń od 0,001 do 0,1 mg/l. W załączniku opisano metodę mineralizacji stosowaną w przypadku trudnorozkładalnych związków arsenu. Wyższe stężenia arsenu można oznaczać przy odpowiednim rozcieńczeniu próbki wodą wolną od arsenu" [A method for the determination of arsenic in water and wastewater is described. It is applicable in the concentration range from 0.001 to 0.1 mg/l. An annex describes a digestion method used for arsenic compounds that are difficult to decompose. Higher arsenic concentrations can be determined after appropriate dilution of the sample with arsenic-free water]. The Polish edition was published on 28 July 1999, has 8 pages and is maintained by KT 121 Water Quality — Chemical Testing — Inorganic Substances; it implements EN 26595:1992, ISO 6595:1982 and the corrigendum EN 26595:1992/AC:1992, and in the "Replaces" field it lists PN-C-04594-00:1975 and PN-C-04594-01:1988. The card gives a WITHDRAWAL DATE — 1 July 2016 — and has no "Replaced by" field (state of the card on 23.09.2026).

THE REGULATION LISTS A STANDARD WITHDRAWN THREE YEARS EARLIER. The regulation of the Minister of Maritime Economy and Inland Navigation of 12 July 2019 (Journal of Laws 2019 item 1311) lists in Annex No. 12, under item 5 "Arsen" [arsenic], four methodologies: atomic absorption spectroscopy with flameless atomisation (PN-EN ISO 15586), molecular absorption spectrophotometry — i.e. this standard (PN-EN 26595), inductively coupled plasma atomic emission spectrometry (PN-EN ISO 11885) and inductively coupled plasma mass spectrometry (PN-EN ISO 17294-2). The act was promulgated on 15 July 2019, and PN-EN 26595 was withdrawn on 1 July 2016 — three years and two weeks earlier. Explanatory note 2 to the annex says: "Jeżeli norma wskazana w załączniku zostanie zastąpiona i wycofana, za normę zalecaną należy uznać nową normę z Polskich Norm" [If a standard indicated in the annex is replaced and withdrawn, the new standard from the Polish Standards shall be regarded as the recommended standard]. For this standard the explanatory note indicates nothing: the card gives the withdrawal, but does not give a replacing standard. It is different for chlorides in the same annex, where the indicated PN-EN ISO 10304-2 was withdrawn and replaced, and the card names the successor.

WHAT THE MEASUREMENT SHOWS. Copy of the accreditation scopes, reading of 23.09.2026. All notations of the number in the reference-document field (neither a digit nor a letter may stand before the number, and no digit after it): PN-EN ISO 11885 — 86 laboratories and 261 entries, PN-EN ISO 15586 — 66 and 143, PN-EN ISO 17294-2 — 50 and 104, PN-EN 26595 — zero. We count the entries concerning arsenic in two ways. When arsenic stands in the TEST NAME: 84 laboratories, 156 entries; with them PN-EN ISO 11885 — 12 laboratories (19 entries), PN-EN ISO 15586 — 11 (11), PN-EN ISO 17294-2 — 7 (9). When arsenic stands in the test name OR in the list of parameters, also in group tests of the kind "Stężenie metali" [metal concentration]: 138 laboratories, 323 entries; with them PN-EN ISO 11885 — 42 laboratories (65 entries), PN-EN ISO 17294-2 — 35 (58), PN-EN ISO 15586 — 28 (33). PN-EN 26595 — zero under both measures. Explanatory note 4 to the annex calls the method of PN-EN ISO 11885 "szczególnie zalecaną w sytuacjach oznaczania w jednej próbce większej liczby pierwiastków" [particularly recommended where a larger number of elements are determined in one sample] and lists arsenic among them.

A STANDARD FOR THE HYDRIDE TECHNIQUE — WITHDRAWN ON THE SAME DAY, AND STILL CITED. Next to arsenic the scopes also contain PN-EN ISO 11969:1999 "Jakość wody — Oznaczanie arsenu — Metoda absorpcyjnej spektrometrii atomowej (technika wodorkowa)" [Water quality — Determination of arsenic — Atomic absorption spectrometric method (hydride technique)], which Annex No. 12 does not list. Its card gives a range from 1 µg/l to 10 µg/l in drinking water, groundwater and surface water and a withdrawal date of 1 July 2016 — the same as for PN-EN 26595. Under both measures it is cited by 12 laboratories in 14 entries: under the narrower measure by as many laboratories as PN-EN ISO 11885, under the wider one — by fewer than each of the three standards of item 5 that laboratories cite (PN-EN ISO 11885, 17294-2 and 15586). Two standards withdrawn on the same day: one is cited today by twelve laboratories, the other — by none. Withdrawal alone therefore does not explain the zero for PN-EN 26595.

WHAT WE DO NOT GIVE. We did not have the text of the standard (8 pages). The title gives the colour reagent, the card — the range, dilution with arsenic-free water and the digestion of arsenic compounds that are difficult to decompose, described in the annex. We do not give the course of the reaction, the way arsenic is converted into the form determined, the measurement wavelength or the apparatus.

Method principle

According to the title and the card of the standard: arsenic is determined spectrophotometrically with silver diethyldithiocarbamate, in the range from 0.001 to 0.1 mg/l. Arsenic compounds that are difficult to decompose are digested according to the annex of the standard, and higher concentrations are determined after dilution of the sample with arsenic-free water. WE DO NOT GIVE the course of the reaction, the way arsenic is converted into the form determined or the measurement wavelength — we did not have the text of the standard.

Applications

• Water and wastewater — scope of the standard according to the card
• Testing of wastewater for the purposes of Journal of Laws 2019 item 1311 — a methodology listed for arsenic (Annex No. 12, item 5), despite the withdrawal of the standard on 01-07-2016

Key parameters

Standard

Standard number

PN-EN 26595:1999

Title (PL)

Jakość wody — Oznaczanie arsenu ogólnego — Metoda spektrofotometryczna z dietyloditiokarbaminianem srebra

Title (EN)

Water quality — Determination of total arsenic — Silver diethyldithiocarbamate spectrophotometric method

Step-by-step procedure

1. Checking the status of the standard

   The standard has been withdrawn since 01-07-2016, and the card indicates no replacing standard (state of the card on 23.09.2026). The 2019 regulation nevertheless lists it for arsenic.

2. Digestion — where needed

   Arsenic compounds that are difficult to decompose are digested according to the annex of the standard (card); WE DO NOT GIVE the conditions.

3. Spectrophotometric determination

   WE DO NOT GIVE the course of the determination — we did not have the text of the standard.

4. Samples above the range

   Concentrations higher than 0.1 mg/l are determined after dilution of the sample with arsenic-free water (card).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• We do not describe the hazards associated with the reagents and the course of the reaction — we do not know the course, because we did not have the text of the standard; the safety data sheets of the reagents and arsenic standards used in the laboratory apply

Frequently asked questions