Quantitative NMR (qNMR) ServicesRush Available
Quantitative NMR (qNMR) accurately measures purity and quantifies organic compounds without reference materials.
qNMR is a primary analytical method recognized by regulatory agencies for purity determination. Unlike HPLC-UV or other methods, qNMR requires no calibration curves or traceable reference compound, making it ideal for pharmaceutical purity analysis, quality control, and research applications. A internal standard is still needed but unlike HPLC, the standard does not have to be the same compound. Quantitative NMR is primarily used with H-1 but can be also usedd for F-19 and P-31 NMR.
What is Quantitative NMR?
Quantitative NMR (qNMR) uses the inherent quantitative nature of NMR spectroscopy to determine the purity and concentration of compounds with high accuracy and precision.
Why qNMR is a Primary Analytical Method
NMR is considered a primary method of analysis because:
- Universal detector - All hydrogen atoms respond equally regardless of chemical structure
- No calibration needed - Direct relationship between signal and quantity
- Traceable to SI units - Based on fundamental physical constants
- Matrix independent - Impurities don't affect quantification (if resolved)
- Absolute quantification - Unlike UV/HPLC which require external standards
How Quantitative NMR Works
The qNMR Principle
qNMR works by comparing the integrated signal from your compound to a known internal standard added to the same sample:
- Weigh your sample - Known mass of analyte
- Add internal standard - Known mass of certified reference material
- Dissolve in deuterated solvent - Prepare NMR sample
- Acquire NMR spectrum - With careful acquisition parameters
- Integrate peaks - Compare analyte peak to standard peak
- Calculate purity - Using the qNMR equation
qNMR Purity Calculation
Where:
- Wt = Weight (mass of sample or standard)
- MW = Molecular Weight
- I = Resonance Integral (peak area)
- N = Number of Equivalent Nuclei (hydrogens in the peak)
- P = Assigned Purity of Standard (typically 99.5-100%)
Applications of Quantitative NMR
Pharmaceutical Applications
- API purity determination - Active pharmaceutical ingredients
- Reference standard certification - Primary standards
- Impurity quantification - Identify and quantify impurities
- Drug substance release testing - QC/QA
- Stability studies - Track degradation over time
- Method validation - Validate other analytical methods
- Pill quantification - Validate quantity of drug in a pill
Research & Development
- Reaction monitoring - Track conversion and yield
- Product purity assessment - Verify synthetic products
- Natural product quantification - Bioactive compound content
- Formulation analysis - Drug product composition
- Mixture analysis - Quantify components in mixtures
Internal Standards for qNMR
Choosing the Right Internal Standard
The internal standard is critical for accurate qNMR. It must meet these criteria:
- High purity - Certified reference material (>99.5%)
- Well-resolved signals - No overlap with analyte peaks
- Simple spectrum - Preferably one sharp singlet
- Stable - Chemically and physically stable
- Soluble - In the same solvent as analyte
- Non-reactive - Doesn't interact with analyte
Common Internal Standards
- Dimethyl sulfone (DMSO₂) - Singlet at ~3.0 ppm
- Maleic acid - Singlet at ~6.3 ppm
- Ethylene carbonate - Singlet at ~4.5 ppm
- 1,3,5-Trimethoxybenzene - Singlet at ~6.1ppm and Singlet at ~3.8ppm, Good for aromatic samples
- 1,2,4,5-Tetrachloro-3-nitro-benzene - Singlet ~7.8ppm Good for aromatic samples
We can help select the optimal internal standard for your specific compound.
Advantages of qNMR vs Other Methods
| Feature | qNMR | HPLC-UV | GC-FID |
|---|---|---|---|
| Requires calibration curve? | No ✓ | Yes | Yes |
| Traceable reference needed? | No ✓ | Yes | Yes |
| Universal detector? | Yes ✓ | No (response varies) | No (no response for some compounds) |
| Primary method? | Yes ✓ | No (secondary) | No (secondary) |
| Structural information? | Yes ✓ | No | No |
Sample Requirements for qNMR
Sample Amount
- Minimum: 10-15 mg per run
- Recommended: 15-20 mg per run for best accuracy
- Higher concentration improves signal-to-noise
- Precision improves with more material
Recommended: Double or triplicate runs for maximum precision and reproducibility
Sample Preparation
- Solvent: Deuterated (CDCl₃, DMSO-d₆, D₂O, etc.)
- Internal standard: We can provide or you can supply
- Accurate weighing required - ±0.01 mg precision
- Complete dissolution - Sample must be fully dissolved
Accuracy and Precision
qNMR Delivers High Accuracy
Typical performance:
- Accuracy: ±1% (relative)
- Precision (RSD): <1% for well-resolved peaks
- Linearity: Excellent over wide concentration range
Factors affecting accuracy:
- Weighing precision (most critical)
- Peak resolution and overlap
- Acquisition parameters (relaxation delay, pulse angle)
- Integration accuracy
- Purity of internal standard
Turnaround Time & Pricing
Standard Turnaround: 3-5 business days
Rush Service: Rush service available for 1.5x normal cost (Please note Rush on the order form)
Includes: Full report with purity calculation, and raw data
Recommended: Double or triplicate runs for maximum precision and reproducibility
For pricing information, please visit our Pricing page or contact us.
Why Choose NuMega for Quantitative NMR?
Expertise
Experienced with qNMR methodology and regulatory requirements for pharmaceutical purity
High-Field NMR
500 MHz Bruker NMR provides excellent resolution for accurate integration
Complete Service
We handle internal standard selection, sample prep, analysis, and detailed reporting
Need Accurate Purity Determination?
Submit your samples for quantitative NMR analysis
Submit a Sample Request a Quote
Phone: (858) 793-6057 | Email: NuMegaLab@NuMegaLabs.com
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