🍎 Nitrates and nitrites in fruits, vegetables and their products — spectrophotometric method, PN-A-75112

Food chemistry PN-92/A-75112

Overview

WHAT THE STANDARD COVERS. The scope from the PKN catalogue card, quoted in full: "Two methods are discussed: one using direct reduction with cadmium and one using a cadmium column. The method using direct reduction with cadmium consists of a colour reaction with the Griess reagent after nitrates have been reduced to nitrites directly with powdered cadmium. The method of determination with a cadmium column consists of inducing a colour reaction with the Griess reagent after nitrates have been reduced to nitrites using a cadmium column. A drawing of the reduction column is given." Both methods therefore determine nitrates indirectly — as nitrites after reduction with cadmium — and nitrites by a colour reaction with the Griess reagent; they differ in the way of reduction.

STATUS (state of the card on 29 September 2026). The card carries the heading "Withdrawn" and the row "Date of withdrawal: 26-10-2012". There are no "Superseded by" and "Supersedes" fields. Edition: published 30-09-1992, 6 pages, PKN technical committee KT 38 (Fruit and Vegetable Products), ICS 67.080.01; "Introduces: ISO 6635:1984 [NEQ]" — the designation NEQ means that the standard is not equivalent to ISO 6635, only related to it. The PKN search for "PN-A-75112" shows only this standard (29 September 2026); a successor WE HAVE NOT ESTABLISHED.

REGULATION — MAXIMUM LEVELS OF NITRATES. Commission Regulation (EU) 2023/915 of 25 April 2023 on maximum levels for certain contaminants in food, Annex I, point 6.1 "Nitrates", in mg NO₃/kg: fresh spinach — 3500 (excluding spinach for processing transported in bulk directly from the field); preserved, deep-frozen or frozen spinach — 2000; fresh lettuce — from 3000 (grown in the open air, harvested from 1 April to 30 September) to 5000 (grown under cover, harvested from 1 October to 31 March); iceberg-type lettuce — 2000 or 2500 (under cover); rucola — 6000 (harvested from 1 April to 30 September) or 7000 (from 1 October to 31 March); baby food and processed cereal-based food for infants and young children — 200, for the product ready for consumption. The regulation was amended 13 times up to July 2026; none of the amending acts concerns nitrates (titles from CELLAR, and the only act with a general title — 2024/1756 — does not contain the word "nitrate"). The regulation does not specify a method of determination.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17 September 2026, read on 28 September 2026). All records of number 75112: 15 entries at 13 laboratories. Forms: "PN-92/A-75112" — 8 laboratories, "PN-A-75112:1992" — 5 (AB 343, AB 486, AB 519, AB 562, AB 601). The "Laboratories" tab searches for records BEGINNING with "PN-92/A-75112" and will show 8 laboratories — checked with the tab query on the labcoda.pl production server on 29 September 2026: 8; it will not show the five with the record "PN-A-75112:1992". Clauses: nine laboratories cite clause 3 alone, AB 515 excludes clauses 2.1, 2.5 and 2.6, AB 539 — the whole of clause 2, and AB 519 and AB 560 give no clauses. The card describes two methods of reduction (with powdered cadmium and on a cadmium column); the pattern of the records suggests that clauses 2 and 3 are these two methods and that almost all laboratories use one of them — which one, WE HAVE NOT ESTABLISHED. Technique: the spectrophotometric method — at all of them. Current scopes on the PCA website (read on 29 September 2026): all 15 entries stand in the valid issues, every numerical range from the copy appears in the current document and none is suspended.

WHAT THEY DETERMINE AND IN WHAT UNITS. Nitrates — all 13 laboratories; nitrites — 11 (all except AB 519 and AB 539; AB 343 in a separate entry). Object: fruits, vegetables and their products; food for children is named explicitly by AB 311 ("Przetwory dla dzieci: konserwy i soki dla dzieci" — products for children: canned goods and juices), AB 451 (separate entry "Produkty dla niemowląt i dzieci do lat trzech" — products for infants and children up to three years: nitrates 5.8–336.5 mg NO₃⁻/kg), AB 486 ("konserwy owocowo-warzywne dla dzieci" — canned fruit and vegetables for children), AB 537 and AB 552; AB 539 and AB 565 write "środki (spożywcze) specjalnego przeznaczenia żywieniowego" (foodstuffs for particular nutritional uses), without mentioning children. Units: AB 451 gives the nitrate range as NaNO₃ (8.0–461.0 mg/kg) or NO₃⁻, AB 601 — both (NaNO₃ 10.20–9233.8 and NO₃⁻ 7.43–8321.0 mg/kg); nitrites as NaNO₂ or NO₂⁻ are given by AB 451 and AB 601, and by AB 552 — only as NaNO₂. The EU limits are in mg NO₃/kg — a result expressed as NaNO₃ has to be converted before comparison (the mass of NO₃ is about 73 % of the mass of NaNO₃).

RANGES AGAINST THE LIMITS. Lower limits for nitrates: from 2 mg/kg (AB 519) to 45.0 mg/kg (AB 486) — all below 200 mg/kg, the limit for food for children. Upper: from 4000 mg/kg (AB 343) and 5120 mg/kg (AB 562) to 16 000 mg/kg (AB 537). At AB 343, AB 562 and AB 451 (6740 mg/kg) the range ends below 7000 mg/kg — the limit for rucola harvested from 1 October to 31 March — and at AB 311, AB 486, AB 560 and AB 565 exactly at 7000 mg/kg; at these seven laboratories a result exceeding this limit lies outside the accreditation range.

ALONGSIDE THIS STANDARD. For nitrates in fruits, vegetables and their products — counting entries that name fruits or vegetables, including those intended for children — the copy has 21 laboratories. Apart from this standard their scopes cite: PN-EN 12014-2:2018-01 — four laboratories (AB 103, AB 379, AB 381, AB 444; AB 444 writes "PN-EN 12014-2" without a year), with ion chromatography or high-performance liquid chromatography; PN-EN 12014-4:2006 — AB 452, in an entry shared with ready meals and meat (high-performance liquid chromatography with spectrophotometric detection, HPLC-UV; nitrates as NaNO₃, 10–5000 mg/kg, nitrites as NaNO₂, 1.0–500 mg/kg); in-house procedures — AB 079 (PB-602, continuous flow analysis CFA), AB 313 (PB-PAZ/FS-22, in an entry shared with meat, ready meals, foods for particular nutritional uses and milk) and AB 532 (PB-26, and for food with meat and vegetables for infants and young children — PB-07). Entries that name neither fruits nor vegetables stay outside this count: AB 515 — procedure PB/HŻ/C/18 for "Środki spożywcze uzupełniające dla dzieci i niemowląt" (complementary foods for children and infants); "Materiał roślinny" (plant material) with PN-EN 12014-7:2001 and continuous flow analysis — AB 312, AB 317, AB 333; flexible food entries (e.g. "Żywność E") with the general record "Normy" (standards) (AB 079, AB 509, AB 704, AB 1408), with "PN-EN 12014" without a part number (AB 438) or with procedures (AB 079, AB 400, AB 462, AB 509, AB 704, AB 1095, AB 1688); milk and milk products according to PN-EN ISO 14673-1 — for products for children seven laboratories (AB 311, AB 343, AB 451, AB 518, AB 519, AB 537, AB 552).

WHAT WE DO NOT GIVE. We did not have the text of the standard — PKN sells it. We do not give the sample preparation and extraction, the conditions of reduction on cadmium, the design of the column, the composition of the Griess reagent, the wavelength, the calibration curve, the formula or the precision.

Method principle

According to the card of the standard, nitrates are reduced with cadmium to nitrites — directly with powdered cadmium or on a cadmium column — and nitrites are determined by a colour reaction with the Griess reagent, measured spectrophotometrically. The nitrate result is compared with the maximum levels of Regulation (EU) 2023/915, in mg NO₃/kg. We DO NOT GIVE the sample mass, extraction, reduction conditions or wavelength — we did not have the text of the standard.

Applications

• Nitrates in leafy vegetables and food for children — assessment against the maximum levels of Regulation (EU) 2023/915, Annex I, point 6.1
• Fruits, vegetables and their products — in the accreditation scopes of 13 laboratories, all with the spectrophotometric method

Key parameters

Standard

Standard number

PN-A-75112:1992 (wersja polska)

Title (PL)

Owoce, warzywa i ich przetwory — Oznaczanie zawartości azotynów i azotanów

Title (EN)

Fruits, vegetables and their products — Determination of nitrite and nitrate content

Step-by-step procedure

1. Status and clause of the standard

   PKN card: standard withdrawn on 26-10-2012, no successor indicated (state of the card on 29 September 2026). The clause of the standard in the scope indicates the method of reduction — nine laboratories cite clause 3.

2. Sample preparation

   Comminution and extraction; details NOT GIVEN.

3. Determination

   Spectrophotometric method (at all laboratories in the scopes). Reagents and conditions NOT GIVEN.

4. Result

   Content in mg/kg; record whether as NO₃⁻ (NO₂⁻) or NaNO₃ (NaNO₂).

5. Assessment

   Nitrates are compared with the limit of Regulation (EU) 2023/915 for the given product and harvest period — in mg NO₃/kg; for food for children — the product ready for consumption.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Both methods use cadmium (powdered or in a column) — cadmium is toxic, and waste containing cadmium requires separate handling
• SUBSTANTIVE NOTE: a result as NaNO₃ compared directly with a limit in mg NO₃/kg overstates the content by about 37 %

Frequently asked questions