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qNMR

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27Cambridge Isotope Laboratories, Inc.
qNMR STANDARDS

3.337

7.952
7.943
7.628
7.619
7.610
7.508
7.499
7.490

Quantitative 1H-NMR (qNMR) continues to be utilized with muchsuccess in the pharmaceutical, chemical and food industries andin many facets of academic research. Regardless of the application,
all qNMR methods require a calibration signal whose integrated
signal intensity originates or is traceable to a known number ofprotons. Calibration for qNMR is made using either internal orexternal referencing methods. External methods rely on the useof a standard solution packaged in a defined NMR tube or capillary
to obtain an integral that can be used for sample quantification,
whereas internal methods rely on the use of a known amountof standard that is co-dissolved in the sample itself.

2.502
2.500
2.498

Standards for qNMRCurrent Data Parameters
NAME
KrisEXPNO
7PROCNO
1Benzoic acid
HH
(a)

(b)
(c)

F2 - Acquisition Parameters
Date_20140119
Time11.14
INSTRUM
spect
PROBHD
5 mm CPQCI 1HPULPROGzg
TD65536SOLVENT
DMSO
NS4DS
0SWH
10204.082 Hz
FIDRES
0.155702 Hz
AQ
3.2113140 sec
RG
8.01
DW
49.000 usec
DE14.03 usec
TE
299.5 K
D130.00000000 sec
TD01

COOH

(a)

NH(b)
N(c)

DMSO-d5======== CHANNEL f1 ========
NUC11H
P1
10.50 usec

External Calibration Standards

F2 - Processing parameters
SI65536SF
850.1800072 MHz
WDWEM
SSB
0LB
0.30 Hz
GB0PC
1.00

HOD

CIL is pleased to offer external calibration standards for qNMR.
The standards are formulated using CIL’s high-quality DMSO-d6
and benzoic acid from NIST (SRM 350(b)), a standard referencematerial for acidometry. Both 5 mM and 15 mM benzoic acidconcentrations are available. The concentration and associatedexpanded uncertainty of the benzoic acid has been accurately
determined using metrological techniques and verified using
qNMR. The 1H-NMR spectrum of benzoic acid in DMSO-d6
is presented in Figure 1.

10987654321ppm

Figure 1. 850 MHz 1H-NMR spectrum of benzoic acid in DMSO-d6.
Resonances from the aromatic protons of benzoic acid, HOD and DMSO-d5
are assigned. The acid proton resonance from benzoic acid (~12-13 ppm) isnot shown. (Courtesy Joe Ray, Baxter Healthcare Corporation, Round Lake, IL)

CIL is currently offering these standards in presealed NMR tubes.
Please see the information below for details regarding NMR tubes
and fill volumes. Other NMR tubes and concentrations may beavailable upon request.

qNMR Standard for External Referencing
Catalog No.

Description*

NMR Tube**Part No.

Fill VolumeDLM-9491A

5 mM Benzoic acid in DMSO-d6

1.7 mm O.D.	

Bruker Part No. Z106462

50 µL

DLM-9491B

5 mM Benzoic acid in DMSO-d6

3 mm O.D.	

Wilmad Part No. 335-PP-9160 µL

DLM-9491C

5 mM Benzoic acid in DMSO-d65 mm O.D.	

Wilmad Part No. 528-PP-8750 µL

DLM-7061A

15 mM Benzoic acid in DMSO-d6

1.7 mm O.D.	

Bruker Part No. Z106462

50 µL

DLM-7061B

15 mM Benzoic acid in DMSO-d63 mm O.D.	

Wilmad Part No. 335-PP-9160 µL

DLM-7061C

15 mM Benzoic acid in DMSO-d6

5 mm O.D.	

Wilmad Part No. 528-PP-8750 µL* The benzoic acid concentration and associated uncertainty are reported.
** All tubes are flame-sealed to ensure longevity.

Other NMR
fill volumes
and tubes areavailable.
Please inquire.

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isotope.com
qNMR STANDARDSStandards for qNMR (continued)
Internal Calibration Standards
The internal reference method commonly gives errors of <1% andis considered to be the most accurate and reproducible method
available to obtain quantita­tive 1H-NMR spectra. Unfortunately, thereference standard is typically weighed into each sample solution,an action that requires time and effort, and has been reported to
the largest source of error with this method.
CIL is pleased to offer a ready-to-use DMSO-d6 solution containing
a known amount of benzoic acid for internal referencing. Because
this solution is preformulated, the user does not need to weigh astandard material. The elimination of this step will reduce effort
and time in sample preparation and also may bring about moreaccurate results than if the user performs this formulation. To use
this product, the sample must be soluble in DMSO-d6, physicallyand chemically inert toward benzoic acid and stable in acidic pH.
Ideally, there will be no resonances from the sample in the regionof benzoic acid aromatic protons (7.4-8.1 ppm), HOD (~3 ppm
but is variable) and DMSO-d5 (2.5 ppm). The benzoic acidconcentration with associated uncertainty is presented on
the certificate of analysis.

qNMR Standard for Internal Referencing
Catalog No.

Description

AmpouleComments

DLM-9491D

5 mM Benzoic acid in DMSO-d61g

The benzoic acid concentration and associated uncertainty is reported.

DLM-7061D

15 mM Benzoic acid in DMSO-d61g

The benzoic acid concentration and associated uncertainty is reported.

CIL Formulation Procedure
The procedure that CIL uses to formulate qNMR externalcalibration reference standard bulk solutions allows for theexpanded uncertainty of the concentration of the calibration
standard (e.g., benzoic acid) to be determined. Traceability
to SI is maintained through the use of weight sets withSpan Accuracy

Linearity

Repeatability

calibration traceable to NIST and laboratory balanceswith NIST-traceable calibration certificates, maintaining
an unbroken chain of calibration to the kilogram.
The factors contributing to the uncertainty of the
benzoic acid concentration1 is shown in below.

Readability

Calibration
Pstd

Cw/w Final uncertainty

Calibration
Span Accuracy
Linearity
Repeatability
Readability
mstd
Calibration

mstd = mass standard, mg

Span Accuracy

Pstd = standard purity fraction

Linearity

msol = mass of solution, g

Repeatability

Cw/w = concentration, µg/gReadability
Mass of solvent
msol

Cause-and-effect diagram of factors contributing to the uncertainty of the benzoic acid concentration in the qNMR standard formulation.
Reference
1. EURACHEM CITAC Guide CG 4, “Quantifying Uncertainty in Analytical Measurement,” Third Edition, QUAM:2012

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