OT:RR:CTF:CPMMA H328353 CKG
Center Director
Pharmaceuticals, Health & Chemicals Center
U.S. Customs and Border Protection
ATTN: Import Specialist Cathy Sheridan
RE: Internal Advice; Classification of 15N-isotopic Ammonium Sulfate
Dear Center Director,
This is in regard to a request for internal advice, dated September 1, 2022, filed on behalf of Cambridge Isotope Laboratories, Inc. (CIL), regarding the classification under the Harmonized Tariff Schedule of the United States (HTSUS) of an ammonium sulfate isotope.
FACTS:
The product at issue is 10% 15N-isotopic ammonium sulfate, produced by the replacement of the standard Nitrogen isotope of nitrogen-14 with nitrogen-15.
The imported article is produced by the reaction of 10% 15N enriched ammonia gas and sulfuric acid. The two nitrogen isotopes are separated; and the 15N isotope, which is naturally 0.37%, is enriched to 10%, or to the desired level. The established method for enrichment of 15N nitrogen is the cryogenic distillation (rectification) of nitric oxide4. Once isotopically enriched, the nitric oxide is converted to enriched nitrogen and then to enriched ammonia. The enriched ammonia is then converted to enriched ammonium sulfate by a reaction with sulfuric acid.
CIL substitutes common atoms (e.g., 1H, 12C, 14N, 16O) with rare isotopes (e.g., 2H or D, 13C, 15N, 18O) so that the final product can be readily measured or traced using mass spectrometry (MS) or nuclear magnetic resonance (NMR). The imported article, 15N-ammonium sulfate, is one such stable, non-radioactive, isotopically labeled compound that is used in laboratories for quantifying the concentration of endogenous metabolites within a complex biological matrix utilizing mass spectrometry or nuclear magnetic resonance.
This product was classified by CIL in heading 2845, HTSUS, which provides for “Isotopes other than those of heading 2844; compounds, inorganic or organic, of such isotopes, whether or not chemically defined”. The entry was rate-advanced from heading 2845, HTSUS, to heading 3102, HTSUS, which provides for “Mineral or chemical fertilizers, nitrogenous.”
ISSUE:
Whether the instant ammonium sulfate isotope is classified in heading 2845, HTSUS, as an inorganic isotope compound, or in heading 3102, HTSUS, as a nitrogenous fertilizer.
LAW AND ANALYSIS:
Classification of goods under the HTSUS is governed by the General Rules of
Interpretation (GRI). GRI 1 provides that classification shall be determined according to the terms of the headings of the tariff schedule and any relative section or chapter notes. In the event that the goods cannot be classified solely on the basis of GRI 1, and if the headings and legal notes do not otherwise require, the remaining GRIs 2 through 6 may then be applied in order.
The HTSUS provisions under consideration are as follows:
2845: Isotopes other than those of heading 2844; compounds, inorganic or organic, of
such isotopes, whether or not chemically defined:
2845.90.0100: Other.
3102: Mineral or chemical fertilizers, nitrogenous
Note 1(a) to Section VI states:
(a) Goods (other than radioactive ores) answering to a description in heading
2844 or 2845 are to be classified in those headings and in no other heading of the tariff schedule.
The ENs to Section VI, Note 1 state:
Note 1.
Under the provisions of paragraph (A) of this Note…in the case of nonradioactive isotopes and their compounds, the Note provides that these (whether inorganic or organic, and whether or not chemically defined) are classified in heading 28.45 and not elsewhere in the Nomenclature. Thus, the isotope of carbon is classified under heading 28.45 and not under heading 28.03.
Note 2 to Chapter 31 provides, in pertinent part:
2. Heading 3102 applies only to the following goods, provided that they are not put
up in the forms or packages described in heading 3105:
(a) Goods which answer to one or other of the descriptions given below:
…(iv) Ammonium sulfate, whether or not pure;
The EN to heading 2845 provides, in pertinent part:
For the definition of the term “isotopes”, see Part (I) of Explanatory Note to heading 28.44.
This heading covers stable isotopes, that is, non radioactive isotopes and their inorganic or organic compounds, whether or not chemically defined.
The EN to heading 2844 defines the term “isotope” as follows:
For the purposes of Note 6 to this Chapter and of headings 28.44
and 28.45, the term isotopes covers not only isotopes in their pure
state but also chemical elements whose natural isotopic
composition has been artificially modified by enriching the
elements in some of their isotopes (which is the same as depleting
them in some others), or by converting, through a nuclear
reaction, some isotopes into other, artificial isotopes. For example,
chlorine of atomic weight 35.30 obtained by enriching this element
to contain 85% of chlorine 35 (and consequently by depleting it to
contain 15% of chlorine 37) is considered as an isotope.
* * *
This heading covers only those isotopes which possess the
phenomenon of radioactivity (described below); stable isotopes, on
the other hand, are classified in heading 28.45.
The EN to heading 3102 provides, in pertinent part:
It should be noted that the mineral or chemical products described in the limitative list above are classified in this heading even when they are clearly not to be used as fertilisers.
* * * *
The variations of an atom with different amounts of neutrons in the nucleus are called isotopes. The most common isotope (99.6%) of nitrogen is nitrogen-14, which has 14 neutrons in the nucleus of the atom, with the remainder being nitrogen-15 (with 15 neutrons). Cambridge Isotope Laboratories has substituted the more common nitrogen-14 in an ammonium sulfate compound with the less common nitrogen-15. Such substitutions are typically made for isotope labeling; a rare isotope, possessing an unusual number of neutrons, is easier to detect and track through a chemical reaction, metabolic pathway, or cell.
The EN to heading 2844, defining the term “isotopes” for the purposes of headings 2844 and 2845, HTSUS, states that the term isotopes covers not only isotopes in their pure state but also chemical elements whose natural isotopic composition has been artificially modified by enriching the elements in some of their isotopes. The natural isotropic balance of the instant product has been modified by enriching the nitrogen-15 isotope from 0.37% to 10% of the total composition. The 15N-isotopic ammonium sulfate is therefore an isotope as defined in EN 28.45. As a stable, non-radioactive isotopic compound, the 15N-isotopic ammonium sulfate is described by heading 2845, HTSUS.
Ammonium sulfate, even if not used as a fertilizer, is also classifiable in heading 3102, HTSUS, per the EN to heading 31.02; however, Note 1(a) to Section VI and the General EN to Section VI state that non-radioactive isotopes or compounds of heading 2845 (whether inorganic or organic, and whether or not chemically defined) are classified in heading 2845 and not elsewhere in the Nomenclature. As the instant product is prima facie classifiable in heading 2845, HTSUS, it cannot be classified in heading 3102, HTSUS.
HOLDING:
By application of GRIs 1 and 6, the ammonium sulfate modified with the nitrogen-15 atom is classified in heading 2845, HTSUS, specifically subheading 2845.90.0100, HTSUSA, which provides for “Isotopes other than those of heading 2844; compounds, inorganic or organic, of such isotopes, whether or not chemically defined: Other.” The 2023 column one, general rate of duty is Free.
Duty rates are provided for the internal advice applicant’s convenience and are
subject to change. The text of the most recent HTSUS and the accompanying duty rates are provided online at https://hts.usitc.gov/current.
You are to mail this decision to the internal advice requester no later than 60 days from the date of the decision. At that time, the Office of Trade, Regulations and Rulings will make the decision available to CBP personnel, and to the public on the Customs Rulings Online Search System (CROSS) at https://rulings.cbp.gov/ which can be found on the U.S. Customs and Border Protection website at http://www.cbp.gov and other methods of public distribution.
Sincerely,
Yuliya A. Gulis, Director
Commercial and Trade Facilitation Division