Stable Isotopes: Adding an “Invisible Barcode” to Molecules to Make Quantification, Tracing, and Source Attribution More Reliable (with Selection Guide and Product Tables 1–3)
Stable Isotopes: Adding an “Invisible Barcode” to Molecules to Make Quantification, Tracing, and Source Attribution More Reliable (with Selection Guide and Product Tables 1–3)
Stable isotopes can be understood as “different-weight versions” of the same element (different numbers of neutrons). They are non-radioactive and chemically very similar to the common (light) forms, but can be clearly distinguished by mass spectrometry or isotope-ratio instruments. Therefore, they are widely used as internal standards for accurate quantification and as tracers to follow where molecules go.
1) What is an isotope? What does “stable” mean?
1.1 Element, isotope, nuclide: what’s the difference?
(a) An element is defined by the number of protons in the atomic nucleus.
(b) Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons, so their atomic masses differ.
(c) Nuclide is a more precise term: it is defined jointly by the mass number, atomic number, etc. A nuclide can be stable or radioactive.
1.2 Stable isotopes vs radioactive isotopes
(a) Stable isotopes: do not emit radiation and do not undergo spontaneous decay like radioactive nuclides. The IAEA describes them as “non-radioactive forms of atoms.”
(b) Radioisotopes: have unstable nuclei, decay spontaneously, and release radiation.
This is one key reason stable isotopes are so popular in research and applications: they provide traceability without relying on radioactivity.
1.3 Notes
(a) From a radiation perspective: stable isotopes ≠ radioactive nuclides. Stable isotopes do not pose radiological risk in the radiation sense.
(b) From a chemical/operational perspective: hazards still depend on the compound itself (toxicity, corrosivity, flammability, asphyxiant gases, high-pressure cylinders, etc.). Handling must still follow SDS and gas safety regulations.
2) What is the “structural feature” of stable isotopes, and why are they useful as tools?
Think of an atom as “nucleus + electron cloud.”
2.1 Nuclear difference: different neutrons → different mass
The essential difference between isotopes lies in the nucleus: the number of protons is the same (so the element is unchanged), but the number of neutrons differs (so the mass changes). Therefore:
(a) In mass spectrometry (MS), isotopes show different m/z (mass differences).
(b) In isotope-ratio measurements (IRMS), isotopes show different abundances/ratios (often used to infer origin and process).
2.2 Nearly identical electronic structure → highly similar chemistry (but not completely identical)
Because the element does not change (same proton number), the electronic configuration is largely the same, so chemical reactivity is usually very similar. This makes stable isotopes ideal as labels that are chemically like the original but analytically distinguishable.
Boundary note: isotope substitution changes molecular vibrations and zero-point energy, so physical properties (e.g., boiling point, diffusion) and some reaction behaviors may show subtle differences.
2.3 Important to know: “isotope effects / fractionation” can occur
A mass change can alter some reaction rates or equilibria:
(a) Kinetic isotope effect (KIE): especially prominent for H/D systems; may cause slight changes in reaction rate, retention time, or response.
(b) Equilibrium isotope effect / fractionation: natural processes can produce measurable δ differences, which is a key basis for IRMS source attribution.
This is not necessarily a “disadvantage”—it is often leveraged in mechanistic studies. However, for quantification/tracing you should be aware it can introduce small biases and therefore requires method validation and proper controls.
2.4 Knowledge box | “Intuitive numbers” for natural abundance (why you see M+1 even without labeling)
Understanding M+1: in the isotopic pattern of a mass spectrum, M is the “lightest peak,” composed of the most abundant light isotopes. M+1 is the isotope peak about 1 mass unit heavier (≈ +1 Da) than M, usually because the molecule contains one naturally occurring heavy isotope (most commonly ¹³C replacing ¹²C). So even without labeling, you will still see an M+1 peak.
Isotope | Natural abundance (order of magnitude) | Intuitive takeaway |
¹³C | ~1.07% | The more carbons in a molecule, the stronger the M+1 background. |
¹⁵N | ~0.364% | Nitrogen-containing compounds also contribute to M+1 (usually smaller than ¹³C). |
²H (D) | ~0.0156% (VSMOW scale) | Hydrogen isotope composition is strongly influenced by environmental fractionation; values vary with source. |
¹⁸O | ~0.205% | Oxygen-rich molecules can show a visible M+2 contribution. |
Example: glucose has 6 carbons. Even if it is completely “unlabeled,” a meaningful fraction will fall into M+1 (from molecules that happen to contain exactly one ¹³C). That is why natural-abundance correction is often needed for tracing/flux analysis.
3) The three most essential values of stable isotopes
1. Distinguishability: “light/heavy” versions of the same molecule can be separated on instruments (mass differences in MS; ratio differences in IRMS; and ¹³C/¹⁵N labels are also easier to resolve in NMR).
2. Correction and accurate quantification: using a “heavy-labeled version” as an internal standard can significantly reduce errors from matrix effects, recovery fluctuations, etc. (especially IDMS in LC-MS/MS).
Additional key points: the internal standard should ideally share the same structure, undergo the same workflow, and co-elute as much as possible. ²H substitution may introduce chromatographic isotope effects, causing slight retention-time shifts between the analyte and the deuterated IS; if matrix suppression changes over time, this can amplify errors. When using ²H internal standards, watch for exchange and subtle isotope effects and validate accordingly.
3. Tracing capability: stable isotopes can be used as tracers to follow the migration and transformation of nutrients/metabolites/elements in a system (metabolic pathways, nitrogen cycling, carbon fixation, oxygen-source mechanisms, etc.).
4) How to “classify” stable isotopes
Four classification “rulers” and a selection guide:
Classification ruler | Question you should answer first | Common options/terms | Typical examples | Selection tips |
A. By element family (most intuitive) | Which “tool isotope” do I need? | ²H (D), ¹³C, ¹⁵N, ¹⁸O, ³⁴S, etc. | ²H: DMSO-d₆, CDCl₃, D₂O; ¹³C: ¹³C₆-glucose, ¹³C₃-lactate/pyruvate; ¹⁵N: ¹⁵NO₃⁻ / ¹⁵NH₄⁺ / ¹⁵N₂; ¹⁸O: ¹⁸O₂, ¹⁸O-water | For routine NMR, start with deuterated solvents/heavy water for lock and lower ¹H background. For structural labeling/metabolic analysis, ¹³C/¹⁵N-labeled substrates/amino acids are often key. For oxygen-source mechanisms or radiochemistry target materials, look first at ¹⁸O. For sulfur metabolism/source attribution, consider a ³⁴S system. |
B. By labeling pattern (determines interpretability) | Is the label on the whole molecule or at a specific position? | Uniform labeling (U-label); position-specific labeling; multi-label (e.g., ¹³C+¹⁵N) | U-¹³C₆-glucose; 3-¹³C sodium lactate; ¹³C₆¹⁵N₄-arginine / ¹³C₆¹⁵N₂-lysine | Pathway/flux studies often use U-label or key position-specific labels. Complex network analysis often uses multi-labeling (¹³C+¹⁵N). For quantitative internal standards, prioritize a labeled analog matching the target’s backbone and, ideally, labeling positions. |
C. By enrichment (atom%) (drives sensitivity and cost) | Do I need “strong tracing/quantification” or “cost-friendly/source attribution”? | High enrichment (often ≥98–99 atom%); partial enrichment (e.g., 5 atom%); natural abundance | ≥99 atom%: ¹³CO₂, ¹⁵N₂, U-¹³C₆-glucose, etc.; 5 atom%: ¹⁵N ammonium sulfate; natural abundance: common in IRMS source attribution/fractionation studies | LC-MS internal standards/metabolic tracing usually use high enrichment (less isotope overlap, clearer interpretation). Cost-sensitive tracing/teaching/ecological processes can use partial enrichment. IRMS often relies on natural abundance + reference materials (emphasizing δ values and traceable standards rather than atom%). |
D. By application platform (determines what “form” you buy) | Which instrument/research goal? Do I need solvents, substrates, salts, or gases? | IDMS quant (LC-MS/MS), metabolic tracing/flux, SILAC proteomics, NMR, IRMS, radionuclide target materials | IDMS: matched ¹³C/¹⁵N/²H internal standards; tracing: ¹³C glucose/lactate/acetate, ¹⁵N nitrogen sources; SILAC: heavy Arg/heavy Lys; NMR: deuterated solvents/heavy water + aqueous references TSP/DSS; IRMS: standards/reference materials; target materials: ¹⁸O water (for PET) | NMR solvents → see Table 1; aqueous qNMR references → see Table 2; metabolic tracing/SILAC/lipid internal standards → see Table 3; inorganic N salts/gases/¹⁸O systems and PET target materials → see Table 4. |
Summary: choose the element (A) → decide the labeling pattern (B) → check enrichment (C) → finally, decide “what form to buy / which table to use” based on the platform (D).
5) Typical application scenarios: starting from real experimental questions
Problem you encounter (scenario) | The real pain point you want to solve | Common platforms/methods | How stable isotopes are used (core approach) | What “form” of product you typically buy |
Scenario 1: I want to quantify a compound more accurately — isotope internal standard & IDMS | Matrix effects, recovery fluctuations, ion-suppression causing unstable quantification | LC-MS/MS, GC-MS (clinical/PK/metabolomics) | Add a stable-isotope internal standard that matches the target structure as closely as possible; process it through the same workflow; quantify via peak-area ratios (IDMS / isotope dilution concept) | ²H/¹³C/¹⁵N (and sometimes ¹⁸O) labeled internal standards for the target analyte (prefer stable labeling sites and reliable isotopic purity; note: ¹³C/¹⁵N are often more robust than ²H when feasible) |
Scenario 2: I want to know “where the molecule went” — stable-isotope tracing (tracer) | Track element/metabolite flow and distribution rather than only endpoint concentration | Metabolic tracing (LC-MS/GC-MS/NMR), ecology/agriculture tracing | A “tracer” is a labeled substance added so its distribution and location can be followed; enriched stable isotopes are commonly used as a safe tracing method | Network-entering labeled substrates (e.g., ¹³C-glucose/lactate/pyruvate/acetate; ¹⁵N ammonium/nitrate; ¹⁵N₂), selected by the “element and pathway node” you want to track |
Scenario 3: I want to compare protein differences between two cell conditions — SILAC | More reliable relative proteomics quantification; better between-batch stability | Proteomics LC-MS | Culture cells with “light/heavy” amino acids so newly synthesized proteins incorporate stable isotopes; quantify by light/heavy peak ratios in MS; SILAC was systematically proposed by Ong et al. in 2002 | Heavy lysine / heavy arginine (¹³C/¹⁵N labeled), plus matched media systems (chosen per experimental design) |
Scenario 4: I want food/environment source attribution — isotope ratios (IRMS) | Distinguish sources, processes, and fractionation (δ¹³C/δ¹⁵N/δ¹⁸O, etc.) | IRMS (EA-IRMS, GC-C-IRMS, etc.) | Use isotope fractionation/differences produced by natural processes; the key is calibration/traceability with standards/reference materials, not buying high atom% tracers | Reference materials/standards for the relevant system (and standard gases/standard waters as required by the method) |
Scenario 5: I want structural ID / quantitative NMR — deuterated solvents & aqueous references | Reduce solvent ¹H interference, lock, unify chemical shift / quantitation | NMR (¹H/¹³C…), metabolomics NMR | Use deuterated solvents/heavy water for lock and lower background; aqueous systems often use TSP/DSS as a 0 ppm reference and quantitative internal standard | Deuterated solvents (CDCl₃, DMSO-d₆, CD₂Cl₂, C₆D₆, DMF-d₇, THF-d₈, D₂O, etc.) + aqueous references (TSP-d₄, DSS-d₆) |
Scenario 6: I’m doing PET or probing “where oxygen comes from” — ¹⁸O systems | PET target material preparation, or oxygen-source assignment (O₂ vs H₂O) | PET radiochemistry / mechanistic studies | PET commonly uses enriched ¹⁸O water as target material; mechanistic studies may use ¹⁸O₂ / H₂¹⁸O to trace oxygen sources | ¹⁸O-water (for PET); ¹⁸O₂ oxygen gas; and related inorganic systems |
Scenario 4 add-on: IRMS usually reports isotope ratios as δ values relative to international scales (e.g., carbon VPDB; hydrogen/oxygen VSMOW–SLAP). Therefore, the key is reference-material calibration, normalization, and traceability—rather than purchasing high atom% tracers.
6) Selection Notes
Before purchasing stable-isotope products, it is recommended to self-check these five questions:
1. Are you trying to solve a “quantification” problem, a “tracing/flux” problem, or “source attribution by isotope ratios (IRMS)”?
→ This determines whether you should buy an isotope-labeled internal standard (IDMS), a tracer substrate, or IRMS reference materials/standards (for calibration and traceability).
2. Which labeling element should you choose (²H/¹³C/¹⁵N/¹⁸O …)?
(a) LC-MS internal standards: commonly ²H, ¹³C, ¹⁵N (and sometimes ¹⁸O). Prefer structurally identical internal standards with stable labeling sites and reliable isotopic purity.
(b) Tracing: ¹³C/¹⁵N are used more often (easier to interpret metabolic networks and element fate).
(c) NMR: prioritize deuterated solvents/heavy water (D₂O) (field lock and reduced ¹H background).
3. Uniform labeling or position-specific labeling? How high should the enrichment be?
→ The more complex the tracing and the higher the background, the more you need a clear labeling design (U-label / position-specific / multi-label).
→ High enrichment (often ≥98–99 atom%) is better suited for internal standards and clean tracing. Partial enrichment (e.g., 5 atom%) can be used for cost-sensitive process tracing/teaching or ecological process studies.
4. Could exchange or isotope effects occur?
(a) Certain H/D sites may undergo exchange in solution, during sample prep, or in metabolism. H/D isotope effects are relatively more pronounced and may cause slight retention-time/response differences—method validation is needed.
(b) For LC/GC-MS quantification: when feasible, ¹³C/¹⁵N are often more robust than ²H. If using a ²H internal standard, choose labeling sites that are less prone to exchange and confirm with appropriate controls.
5. Have you considered calibration and traceability?
(a) In high-accuracy quantification and certified reference material systems, IDMS is often used to improve quantification reliability; whereas IRMS relies more on reference materials/standard systems to achieve calibration and traceability (not simply “buying high atom% products”).
7) Navigation Table | Stable-Isotope Product Selection & Table Guide (Tables 1–4)
Typical scenario / need | Which table to check first | Why this table is the best fit | Common keywords / examples |
Routine NMR (¹H/¹³C/¹⁹F, etc.): need deuterated solvents for lock and reduced solvent ¹H background | Table 1 (Deuterated solvents / deuterated reagents) | Covers the most commonly used deuterated solvents (CDCl₃, DMSO-d₆, CD₂Cl₂, C₆D₆, DMF-d₇, THF-d₈, etc.) and common deuterated acid additives (e.g., TFA-d, AcOD). This is the entry point for “choose solvent first for NMR.” | “NMR solvent” “lock” “solvent peak” “CDCl₃ / DMSO-d₆ / C₆D₆ / DMF-d₇” “deuterated acetic acid / deuterated TFA” |
Aqueous NMR / metabolomics NMR quantitation: need unified chemical shift reference and quantitative internal standard | Table 2 (Aqueous NMR references / internal standards) | Dedicated to commonly used aqueous NMR references/internal standards (TSP-d₄, DSS-d₆) for 0 ppm calibration, peak-area quantitation, and batch consistency in metabolomics NMR. | “TSP” “DSS” “0 ppm” “quantitative NMR” “metabolomics NMR” |
Cellular metabolic tracing / ¹³C metabolic flux analysis (MFA): glycolysis, TCA, PPP pathway tracing | Table 3 (Organic isotope tracer substrates) | A “metabolic substrate library”: U-¹³C₆ glucose, ¹³C lactate/pyruvate/acetate, ¹³C/¹⁵N amino acids, etc., suitable for LC-MS/GC-MS tracing of isotope distributions and pathway/flux interpretation. | “U-¹³C₆ glucose” “¹³C lactate” “¹³C₃ pyruvate” “¹³C₂ acetate” “flux / isotopic pattern” |
SILAC quantitative proteomics (cell culture “heavy labeling”) | Table 3 (Organic isotope tracer substrates) | Key SILAC “heavy amino acids” are concentrated here (¹³C₆¹⁵N₄-Arg, ¹³C₆¹⁵N₂-Lys, etc.), used for whole-proteome quantitation and comparative proteomics. | “SILAC” “Heavy Lys/Arg” “cell culture heavy labeling” “quantitative proteomics” |
Lipidomics / lipid metabolism tracing & quantitation: fatty-acid uptake, β-oxidation, lipid synthesis; need MS internal-standard correction | Table 3 (Organic isotope tracer substrates) | Includes typical lipid/fatty-acid internal standards and tracer substrates such as cholesterol-d7, palmitate-d31, stearate-d35, palmitate-¹³C₁₆—useful for recovery/matrix-effect correction and metabolic tracing. | “lipidomics internal standard” “cholesterol-d7” “palmitate-d31 / ¹³C₁₆” “β-oxidation” |
Nitrogen cycle / ecology & environmental tracing: nitrification, denitrification, fertilizer use efficiency, N₂ fixation | Table 4 (Inorganic isotope raw materials) | Concentrates ¹⁵N inorganic nitrogen sources and gases: ¹⁵NO₃⁻ (nitrate), ¹⁵NH₄⁺ (ammonium/ammonia), ¹⁵NO₂⁻ (nitrite), ¹⁵N₂ (gold standard for N fixation), etc. | “¹⁵NO₃⁻” “¹⁵NH₄⁺” “¹⁵NO₂⁻” “¹⁵N₂ nitrogen fixation” “denitrification” |
Oxygen-source / oxidation mechanism studies: determine whether oxygen comes from O₂ or water/substrate | Table 4 (Inorganic isotope raw materials) | ¹⁸O₂ and ¹⁸O water (“oxygen-source labels”) are concentrated here, suitable for mechanistic studies, oxygen exchange, enzymatic oxidation/material oxidation, etc. | “¹⁸O₂” “oxygen-source tracing” “oxidation mechanism” “oxygen exchange” |
Carbon cycle / inorganic carbon tracing: photosynthesis/carbon fixation/respiration isotope experiments; or need labeled bicarbonate/CO₂ | Table 4 (Inorganic isotope raw materials) | ¹³CO₂ and ¹³C sodium bicarbonate provide standard inorganic carbon sources for carbon fixation, inorganic carbon transport, and IRMS/online analysis calibration. | “¹³CO₂” “H¹³CO₃⁻ / NaH¹³CO₃” “carbon fixation” “IRMS” |
PET radiochemistry (¹⁸F production): need enriched ¹⁸O water as target material | Table 4 (Inorganic isotope raw materials) | ¹⁸O-water is the key starting material for PET ¹⁸F production and is a very clear “special-purpose entry point.” | “¹⁸O water” “for PET” “¹⁸F production” |
Method development / quantitative calibration: need stable isotopes for internal standards, calibration, recovery and matrix-effect correction | Depends on the system: aqueous NMR → Table 2; organic/metabolic MS → Table 3; inorganic gases/salts → Table 4; NMR solvents → Table 1 | Internal-standard choice is typically platform- and matrix-dependent: NMR references (TSP/DSS), LC-MS/GC-MS internal standards (lipids/metabolites), and gas/inorganic salt calibration each has its own entry. | “internal standard” “calibration” “recovery” “matrix effect” “qNMR/LC-MS/GC-MS” |
Table 1 | Deuterated Solvents / Deuterated Reagents (Common NMR Solvents, Deuterated Acids, and Common Deuterated Organic Solvents)
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Key features & applications |
Deuterated solvent (strongly polar, common for NMR) | 2206-27-1 | Dimethyl sulfoxide-d₆ | Anhydrous grade, ≥99.9 atom% D | Classic high-boiling deuterated solvent; used for NMR lock and reduced ¹H background; dissolves polar/poorly soluble samples (including polysaccharides, peptides, small-molecule salts, etc.). | |
Deuterated solvent (polar aprotic, NMR/LC-MS) | 2206-26-0 | Acetonitrile-d₃ | Anhydrous grade, ≥99.8 atom% D | Deuterated acetonitrile: polar aprotic solvent for NMR; also used for method controls/solvent-effect studies. | |
Deuterated solvent (small-molecule alcohol) | 811-98-3 | Methanol-d₄ | Anhydrous grade, ≥99.8 atom% D | Deuterated methanol: common NMR solvent; suitable for alcohol-soluble/moderately polar samples; reduces solvent ¹H peak interference. | |
Deuterated solvent (halogenated, classic for NMR) | 865-49-6 | Deuterated chloroform-d | 100%, 99.96 atom% D | CDCl₃: one of the most widely used NMR solvents; dissolves hydrophobic small molecules, natural products, polymers, etc.; used for lock and reduced solvent ¹H background. | |
Deuterated solvent (halogenated, NMR) | 1665-00-5 | D102267 | Dichloromethane-d₂ | ≥99.96 atom% D2 | CD₂Cl₂: low-boiling deuterated solvent; suitable for halogenated-solvent systems, low-temperature NMR, and solvent-effect controls. |
Deuterated solvent (ketone, NMR) | 666-52-4 | Acetone-d₆ | ≥99.96 atom% D, contains 0.03% (v/v) TMS | Common NMR solvent (with TMS as chemical-shift reference); suitable for moderately polar samples and fast-evaporating systems. | |
Deuterated solvent (aromatic, NMR) | 1076-43-3 | Benzene-d₆ | ≥99.96 atom% D, contains 0.03% (v/v) TMS | C₆D₆: suitable for hydrophobic/aromatic compounds; may improve line shape/shift dispersion for some samples; contains TMS for calibration. | |
Deuterated solvent (aromatic, NMR) | 2037-26-5 | Toluene-d₈ | ≥99.94 atom% D | C₇D₈: more hydrophobic aromatic deuterated solvent; used for hydrophobic samples and polymer/materials NMR. | |
Deuterated solvent (strong polar aprotic, NMR) | 4472-41-7 | N,N-Dimethylformamide-d₇ | ≥99.5 atom% D, contains 0.03% (v/v) TMS | DMF-d₇: strongly polar solvent for NMR of polar/high-boiling systems; contains TMS for chemical-shift referencing. | |
Deuterated solvent (basic heteroaromatic, NMR) | 7291-22-7 | Pyridine-d₅ | ≥99.5 atom% D, contains 0.05% (v/v) TMS | Pyridine-d₅: often advantageous for acidic/coordination-capable samples; used for NMR and coordination/hydrogen-bonding studies. | |
Deuterated solvent (ether, NMR) | 1693-74-9 | Tetrahydrofuran-d₈ | ≥99.5 atom% D, contains 0.03% (v/v) TMS | THF-d₈: common in NMR for organic synthesis/coordination chemistry samples; contains TMS for calibration. | |
Deuterated solvent (alcohol, NMR) | 1516-08-1 | Ethanol-d | Anhydrous grade, ≥99 atom% D | Ethanol-d: used in NMR and solvent-effect studies; suitable for alcohol-soluble samples and deuterated-system controls. | |
Deuterated solvent (alcohol, NMR) | 22739-76-0 | 2-Propanol-d₈ | ≥99.5 atom% D | Isopropanol-d₈: used for NMR, isotope-effect/exchange studies, and reducing solvent-peak interference. | |
Deuterated solvent (halogenated, NMR) | 17060-07-0 | 1,2-Dichloroethane (d₄) | ≥99 atom% D | 1,2-DCE-d₄: used for NMR and halogenated-solvent system studies; suitable for hydrophobic/moderately polar samples and solvent-effect controls. | |
Deuterated solvent (ether, NMR) | 17647-74-4 | 1,4-Dioxane-d₈ | ≥99 atom% D | 1,4-Dioxane-d₈: used for polymer/materials and organic synthesis-related NMR; high solvency with low ¹H background. | |
Deuterated solvent (aromatic chlorinated, NMR) | 3114-55-4 | Chlorobenzene-d₅ | ≥98 atom% D, ≥97% | Chlorobenzene-d₅: suitable for highly hydrophobic/aromatic samples and materials NMR; used for solvent-effect studies and polymer dissolution systems. | |
Deuterated reagent (acid / exchange) | 1186-52-3 | Acetic acid-d | ≥99.9 atom% D | Common deuterated acidic medium/proton-exchange reagent; used for NMR sample acidification, H/D exchange studies, and mechanistic controls. | |
Deuterated reagent (strong acid, NMR additive) | 599-00-8 | Trifluoroacetic acid-d | ≥99.5 atom% D, contains 0.03% (v/v) TMS, for NMR | TFA-d: used in NMR to protonate amines/basic compounds (salt formation), improve solubility and line shape; reduces introduction of ¹H acid-peak interference. | |
Heavy water (deuterium source / solvent) | 7789-20-0 | Deuterium oxide | ≥99.9 atom% D | D₂O: aqueous NMR solvent and lock medium; also used for kinetic isotope effects, H/D exchange, and contrast experiments in neutron scattering for proteins/polymers, etc. |
Table 2 | Aqueous NMR References / Internal Standards (Common for Metabolomics / Quantitative NMR)
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Key features & applications |
Deuterated NMR reference / internal standard (TSP) | 24493-21-8 | 3-(Trimethylsilyl)propionic acid-d4 sodium salt | ≥98 atom% D, ≥98% | TSP-d₄ (sodium salt): common 0 ppm chemical-shift reference and quantitative internal standard for aqueous ¹H NMR; used in metabolomics NMR. | |
Deuterated NMR reference / internal standard (DSS) | 284664-85-3 | 3-(Trimethylsilyl)-1-propanesulfonic acid-d₆ sodium salt | ≥98 atom% D | DSS-d₆ (sodium salt): aqueous NMR reference/internal standard at 0 ppm; generally more tolerant to acid/base and more compatible with protein-containing systems; widely used in metabolomics. |
Table 3 | Organic Isotope Tracer Substrates (¹³C/¹⁵N Metabolic Substrates, Amino Acids/Sugars/Organic Acids/Urea) + Lipid/Fatty-Acid Internal Standards
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Key features & applications |
¹³C-labeled amino acid / cellular metabolic substrate | 184161-19-1 | L-Glutamine-¹³C₅ | Moligand™, ≥98 atom% 13C, ≥95% | Common tracer for metabolic studies: feeds into TCA and nitrogen metabolism networks; used for ¹³C MFA, isotope-tracing culture experiments, and LC-MS/GC-MS pathway analysis. | |
¹³C/¹⁵N dual-labeled amino acid (SILAC/proteomics) | 202468-25-5 | L-Arginine-¹³C₆,¹⁵N₄ hydrochloride | ≥99 atom% 15N, ≥99 atom% 13C, ≥95% | Core SILAC “heavy arginine”: used in cell-culture quantitative proteomics; also used for metabolism/transport tracing and LC-MS quantitation. | |
¹³C/¹⁵N dual-labeled amino acid (SILAC/proteomics) | 1200447-00-2 | L-Lysine-¹³C₆,¹⁵N₂ hydrochloride | ≥99 atom% 15N, ≥99 atom% 13C, ≥95% | Core SILAC “heavy lysine”: paired with heavy Arg for whole-proteome quantitation; also commonly used as an internal standard/calibration material. | |
¹³C/¹⁵N dual-labeled amino acid (metabolism / internal standard) | 211057-02-2 | Glycine-¹³C₂,¹⁵N | ≥99 atom% 13C, ≥98 atom% 15N | Dual-labeled glycine: commonly used in one-carbon and amino-acid metabolism tracing; also suitable as an LC-MS internal standard and for recovery correction. | |
¹³C-labeled sugar (ribose / nucleic-acid related substrate) | 202114-47-4 | D-Ribose (U-¹³C₅) | ≥99% | Labeled ribose substrate for nucleoside/nucleic-acid synthesis and metabolic tracing; used for carbon-flow tracing and quantitative method development (MS/NMR). | |
¹³C-labeled sugar (glucose / metabolic tracing) | 110187-42-3 | D-Glucose-¹³C₆ | ≥99 atom% 13C, ≥98% | U-¹³C₆ glucose: one of the most widely used MFA substrates; used to trace glycolysis/TCA/PPP pathways and study cellular metabolism. | |
¹³C-labeled organic acid salt (lactate / metabolic tracing) | 201595-70-2 | Sodium L-lactate-3-¹³C solution | ≥99 atom% 13C, ≥98%, ≥98% (Chiral purity, HPLC), 45–55% (w/w) in H₂O | Position-labeled lactate (3-¹³C): used for glycolysis/lactate metabolism and exchange-pathway analysis; aqueous solution facilitates direct media preparation and MS quantitation. | |
¹³C-labeled organic acid (lactate / metabolic tracing) | 87684-87-5 | L-Lactic acid-¹³C₃ | ≥99 atom% 13C, ≥98%, ≥98% (Chiral purity, HPLC) | Uniformly ¹³C-labeled lactate for MFA, lactate shuttle and energy-metabolism tracing; also used for standards/internal-standard strategy design. | |
¹³C-labeled central metabolite (pyruvate) | 142014-11-7 | Sodium pyruvate-¹³C₃ | ≥99 atom% 13C | ¹³C₃ pyruvate: key node linking glycolysis and TCA; used for mitochondrial metabolism and metabolic flux studies. | |
¹³C-labeled small molecule (acetate / acetyl-CoA precursor) | 56374-56-2 | Sodium acetate-¹³C₂ | ≥99 atom% 13C | ¹³C₂ acetate: used to trace acetyl-CoA sources and fatty-acid/cholesterol biosynthesis; also used in metabolism and microbial fermentation studies. | |
¹³C-labeled organic acid (formic acid / internal standard) | 1633-56-3 | Formic acid-¹³C | ≥99 atom% 13C, <5% H₂O | ¹³C formic acid: often used as an LC-MS additive/method control and quantitative internal standard; also used for C1 metabolism and mechanistic tracing. | |
¹³C-labeled organic salt (formate / calibration) | 23102-86-5 | Sodium formate-¹³C | ≥99 atom% 13C | ¹³C sodium formate: used for NMR/IRMS/LC-MS quantitative calibration and tracing; convenient in aqueous systems. | |
¹⁵N-labeled small molecule (urea) | 2067-80-3 | Urea-¹⁵N₂ | ≥99 atom%, ≥98.5% | Double-¹⁵N urea: used for urea metabolism and nitrogen-cycle tracing; also a precursor for synthesizing other ¹⁵N-labeled compounds. | |
¹³C-labeled small molecule (urea / internal standard) | 58069-82-2 | Urea-¹³C | ≥99 atom% 13C, ≥98% | ¹³C urea: used in urea-cycle/nitrogen-metabolism studies; also commonly used as an internal standard or quantitative calibrant in clinical/biochemical assay method development. | |
Deuterated lipid/sterol internal standard (MS/lipidomics) | 83199-47-7 | Cholesterol-d7 | ≥99%, ≥99 atom% D | Typical lipidomics internal standard for LC-MS/GC-MS cholesterol quantitation, recovery correction, and matrix-effect correction. | |
Deuterated fatty acid (lipid internal standard / metabolic tracing) | 17660-51-4 | Stearic acid-d35 | ≥98% | d35 stearic acid: common lipidomics internal standard/recovery correction; used for β-oxidation and fatty-acid metabolism tracing, and MS method development. | |
Uniformly ¹³C-labeled fatty acid (lipid metabolism tracing) | 56599-85-0 | Palmitic acid-¹³C₁₆ | ≥98 atom% 13C, ≥98% | U-¹³C₁₆ palmitate: used for tracing fatty-acid uptake/elongation/β-oxidation and lipid synthesis; also used as a lipidomics standard and for flux analysis. | |
Deuterated fatty acid (lipid internal standard / metabolic tracing) | 39756-30-4 | Palmitic acid-d31 | ≥95 atom% D, ≥98% | d31 palmitate: common lipidomics internal standard; used for LC-MS quantitation correction and fatty-acid metabolic tracing. |
Table 4 | Inorganic Isotope Raw Materials (Gases / Inorganic Nitrogen Salts / Inorganic Acids / Inorganic Carbonates) + PET Target Material
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Key features & applications |
¹⁵N-labeled inorganic nitrogen source (low enrichment) | 43086-58-4 | Ammonium sulfate-¹⁵N₂ | 5 atom% 15N | Low-enrichment ¹⁵N nitrogen source: suitable for “light tracing/cost-sensitive” experiments; used for soil/plant nitrogen cycling and microbial isotope labeling. | |
¹⁵N-labeled gas / inorganic nitrogen source | 13767-16-3 | A466177 | Ammonia-¹⁵N | ≥99%, ≥10 atom% 15N | ¹⁵NH₃: used for nitrogen metabolism/assimilation tracing, reaction mechanisms (amination/catalysis), and as a raw material for isotope-labeled synthesis. |
¹⁵N-labeled inorganic nitrogen salt (nitrate) | 57654-83-8 | Potassium nitrate-¹⁵N | ≥99 atom%, ≥99% | Classic ¹⁵NO₃⁻ source: used for plant nutrition, soil nitrification/denitrification, ecological nitrogen-cycle tracing, and fertilizer use-efficiency studies. | |
¹⁵N-labeled inorganic nitrogen salt (ammonium) | 39466-62-1 | Ammonium chloride-¹⁵N | ≥99 atom%, ≥98% | ¹⁵NH₄⁺ source: widely used for microbial culture, nitrification tracing, and nitrogen transformation studies in soils/waters. | |
¹⁵N-labeled inorganic nitrogen salt (nitrate) | 31432-45-8 | S110170 | Sodium nitrate-¹⁵N | ≥99 atom% 15N, ≥98.5% | ¹⁵NO₃⁻ sodium salt: convenient for aqueous systems/microbial culture; used in nitrate uptake, denitrification, and environmental tracing. |
¹⁵N-labeled inorganic nitrogen salt (nitrite) | 68378-96-1 | S117725 | Sodium nitrite-¹⁵N | ≥99 atom%, ≥98.5% | ¹⁵NO₂⁻ tracer: used for tracking intermediates in nitrification/denitrification, NOx-related environmental processes, and microbial metabolism studies. |
¹⁵N-labeled inorganic nitrogen salt (ammonium nitrate) | 43086-60-8 | Ammonium nitrate-¹⁵N₂ | ≥99 atom%, ≥98.5% | Double-¹⁵N ammonium nitrate: supplies both ¹⁵NH₄⁺ and ¹⁵NO₃⁻; suitable for full-chain nitrogen transformation tracing and fertilizer/environment studies. | |
¹⁵N-labeled inorganic acid (nitric acid) | 43625-06-5 | Nitric acid-¹⁵N solution | ~10N in H₂O, 98 atom% ¹⁵N | ¹⁵N nitric acid: high-enrichment ¹⁵NO₃⁻ source for mechanism studies, nitrogen-source tracing, and labeled synthesis (solution form enables direct use). | |
¹⁵N-labeled inorganic nitrogen salt (nitrite) | 92937-66-1 | Potassium nitrite-¹⁵N | — | ¹⁵NO₂⁻ potassium salt: used for nitrogen-cycle/NOx pathway tracing, mechanistic studies, and quantitative method development; offers alternative counter-ion conditions vs sodium salt. | |
¹⁵N-labeled gas (nitrogen) | 29817-79-6 | N117731 | Nitrogen-¹⁵N₂ | ≥99 atom% 15N, ≥98.5% | ¹⁵N₂ is the gold-standard tracer gas for biological nitrogen fixation and nitrogen-cycle studies; also used in mechanism studies and isotope labeling. |
¹³C-labeled gas (inorganic carbon source) | 1111-72-4 | C462992 | Carbon dioxide-¹³C | ≥99 atom% 13C, ≥99% | ¹³CO₂ for photosynthesis/carbon-fixation tracing, isotope respiration experiments, IRMS/online isotope analysis calibration, and method development. |
¹³C-labeled gas (carbon source / environmental tracing) | 6532-48-5 | M473945 | Methane-¹³C | ≥99 atom% 13C, ≥99% | ¹³CH₄ for tracing methane oxidation/production processes, environmental geochemistry, and microbial metabolism; also usable as an instrument calibration gas. |
¹³C-labeled inorganic carbonate (bicarbonate) | 87081-58-1 | Sodium bicarbonate-(¹³C) | ≥99 atom% 13C, ≥98% | ¹³C bicarbonate: used in buffer systems and inorganic-carbon-source tracing, bicarbonate transport studies; also used for NMR/IRMS-related calibration. | |
¹⁸O-labeled gas (oxygen) | 32767-18-3 | Oxygen-¹⁸O₂ | ≥99 atom% 18O, ≥99% | ¹⁸O₂ for oxygen-source tracing and oxidation mechanism assignment (oxidation reactions, enzymatic oxidation, material oxygen exchange, etc.); also used for isotope-labeled synthesis. | |
¹⁸O-labeled water (PET radiochemistry) | 14314-42-2 | Water-¹⁸O | ≥98 atom% 18O, for PET | Key PET target material: enriched water for cyclotron production of ¹⁸F ([¹⁸F]F⁻); essential for radiopharmaceutical synthesis and PET tracers. |
Note: The above are representative Aladdin products. For more specifications, please refer to the full product list at the end of the article, or search the Aladdin website by product name/CAS.
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