Limits...
Method development in quantitative NMR towards metrologically traceable organic certified reference materials used as (31)P qNMR standards.

Weber M, Hellriegel C, Rueck A, Wuethrich J, Jenks P, Obkircher M - Anal Bioanal Chem (2014)

Bottom Line: These substances contain both nuclei, (1)H and (31)P, and the concept is to show that it is possible to indirectly quantify a potential phosphorus standard via its protons using (1)H qNMR.The same standard with its assigned purity can then be used for the quantification of an analyte via its phosphorus using (31)P qNMR.For the validation of the concept, triphenyl phosphate and phosphonoacetic acid have been used as (31)P qNMR standards to determine the purity of the analyte tris(2-chloroethyl) phosphate, and the resulting purity values perfectly overlap within their expanded measurement uncertainties.

View Article: PubMed Central - PubMed

Affiliation: Sigma-Aldrich Switzerland, Industriestrasse 25, 9471, Buchs, Switzerland.

ABSTRACT
Quantitative nuclear magnetic resonance (qNMR) spectroscopy is employed by an increasing number of analytical and industrial laboratories for the assignment of content and quantitative determination of impurities. Within the last few years, it was demonstrated that (1)H qNMR can be performed with high accuracy leading to measurement uncertainties below 1 % relative. It was even demonstrated that the combination of (1)H qNMR with metrological weighing can lead to measurement uncertainties below 0.1 % when highly pure substances are used. Although qNMR reference standards are already available as certified reference materials (CRM) providing traceability on the basis of (1)H qNMR experiments, there is an increasing demand for purity assays on phosphorylated organic compounds and metabolites requiring CRM for quantification by (31)P qNMR. Unfortunately, the number of available primary phosphorus standards is limited to a few inorganic CRM which only can be used for the analysis of water-soluble analytes but fail when organic solvents must be employed. This paper presents the concept of value assignment by (31)P qNMR measurements for the development of CRM and describes different approaches to establish traceability to primary Standard Reference Material from the National Institute of Standards and Technology (NIST SRM). Phosphonoacetic acid is analyzed as a water-soluble CRM candidate, whereas triphenyl phosphate is a good candidate for the use as qNMR reference material in organic solvents. These substances contain both nuclei, (1)H and (31)P, and the concept is to show that it is possible to indirectly quantify a potential phosphorus standard via its protons using (1)H qNMR. The same standard with its assigned purity can then be used for the quantification of an analyte via its phosphorus using (31)P qNMR. For the validation of the concept, triphenyl phosphate and phosphonoacetic acid have been used as (31)P qNMR standards to determine the purity of the analyte tris(2-chloroethyl) phosphate, and the resulting purity values perfectly overlap within their expanded measurement uncertainties.

No MeSH data available.


Traceability chains for the purity determination of 31P qNMR standards triphenyl phosphate and phosphonoacetic acid. The quantification of phosphonoacetic acid using two independent NIST reference materials and different NMR experiments demonstrates the proof of concept that the received purity value is independent of the nucleus. This concept may be applied for the quantification of triphenyl phosphate. In a subsequent step, purity determination of tris(2-chloroethyl) phosphate is performed by 31P qNMR using triphenyl phosphate and phosphonoacetic acid as internal standards. The blue arrows symbolize 1H qNMR measurement and red arrows31P qNMR measurements
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4383826&req=5

Fig3: Traceability chains for the purity determination of 31P qNMR standards triphenyl phosphate and phosphonoacetic acid. The quantification of phosphonoacetic acid using two independent NIST reference materials and different NMR experiments demonstrates the proof of concept that the received purity value is independent of the nucleus. This concept may be applied for the quantification of triphenyl phosphate. In a subsequent step, purity determination of tris(2-chloroethyl) phosphate is performed by 31P qNMR using triphenyl phosphate and phosphonoacetic acid as internal standards. The blue arrows symbolize 1H qNMR measurement and red arrows31P qNMR measurements

Mentions: Figure 3 shows the concept for the quantification of the two different phosphorus candidate CRM. Using ammonium dihydrogen phosphate (NIST SRM 194a) in a 31P qNMR measurement, the obtained purity value of phosphonoacetic acid represents the first purity of a phosphorus-containing product, which is traceable to NIST SRM and hence to SI unit. Phosphonoacetic acid is additionally employed in a 1H qNMR measurement with potassium hydrogen phthalate (NIST SRM 84L) as reference as it is crucial to show that 1H qNMR results and 31P qNMR results are consistent within their measurement uncertainties for the quantification of triphenyl phosphate. Once these individual traceability chains prove the independence from the nuclei, triphenyl phosphate can be quantified according to the traceability chain on the left-hand side of the figure using only 1H qNMR measurements.Fig. 3


Method development in quantitative NMR towards metrologically traceable organic certified reference materials used as (31)P qNMR standards.

Weber M, Hellriegel C, Rueck A, Wuethrich J, Jenks P, Obkircher M - Anal Bioanal Chem (2014)

Traceability chains for the purity determination of 31P qNMR standards triphenyl phosphate and phosphonoacetic acid. The quantification of phosphonoacetic acid using two independent NIST reference materials and different NMR experiments demonstrates the proof of concept that the received purity value is independent of the nucleus. This concept may be applied for the quantification of triphenyl phosphate. In a subsequent step, purity determination of tris(2-chloroethyl) phosphate is performed by 31P qNMR using triphenyl phosphate and phosphonoacetic acid as internal standards. The blue arrows symbolize 1H qNMR measurement and red arrows31P qNMR measurements
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4383826&req=5

Fig3: Traceability chains for the purity determination of 31P qNMR standards triphenyl phosphate and phosphonoacetic acid. The quantification of phosphonoacetic acid using two independent NIST reference materials and different NMR experiments demonstrates the proof of concept that the received purity value is independent of the nucleus. This concept may be applied for the quantification of triphenyl phosphate. In a subsequent step, purity determination of tris(2-chloroethyl) phosphate is performed by 31P qNMR using triphenyl phosphate and phosphonoacetic acid as internal standards. The blue arrows symbolize 1H qNMR measurement and red arrows31P qNMR measurements
Mentions: Figure 3 shows the concept for the quantification of the two different phosphorus candidate CRM. Using ammonium dihydrogen phosphate (NIST SRM 194a) in a 31P qNMR measurement, the obtained purity value of phosphonoacetic acid represents the first purity of a phosphorus-containing product, which is traceable to NIST SRM and hence to SI unit. Phosphonoacetic acid is additionally employed in a 1H qNMR measurement with potassium hydrogen phthalate (NIST SRM 84L) as reference as it is crucial to show that 1H qNMR results and 31P qNMR results are consistent within their measurement uncertainties for the quantification of triphenyl phosphate. Once these individual traceability chains prove the independence from the nuclei, triphenyl phosphate can be quantified according to the traceability chain on the left-hand side of the figure using only 1H qNMR measurements.Fig. 3

Bottom Line: These substances contain both nuclei, (1)H and (31)P, and the concept is to show that it is possible to indirectly quantify a potential phosphorus standard via its protons using (1)H qNMR.The same standard with its assigned purity can then be used for the quantification of an analyte via its phosphorus using (31)P qNMR.For the validation of the concept, triphenyl phosphate and phosphonoacetic acid have been used as (31)P qNMR standards to determine the purity of the analyte tris(2-chloroethyl) phosphate, and the resulting purity values perfectly overlap within their expanded measurement uncertainties.

View Article: PubMed Central - PubMed

Affiliation: Sigma-Aldrich Switzerland, Industriestrasse 25, 9471, Buchs, Switzerland.

ABSTRACT
Quantitative nuclear magnetic resonance (qNMR) spectroscopy is employed by an increasing number of analytical and industrial laboratories for the assignment of content and quantitative determination of impurities. Within the last few years, it was demonstrated that (1)H qNMR can be performed with high accuracy leading to measurement uncertainties below 1 % relative. It was even demonstrated that the combination of (1)H qNMR with metrological weighing can lead to measurement uncertainties below 0.1 % when highly pure substances are used. Although qNMR reference standards are already available as certified reference materials (CRM) providing traceability on the basis of (1)H qNMR experiments, there is an increasing demand for purity assays on phosphorylated organic compounds and metabolites requiring CRM for quantification by (31)P qNMR. Unfortunately, the number of available primary phosphorus standards is limited to a few inorganic CRM which only can be used for the analysis of water-soluble analytes but fail when organic solvents must be employed. This paper presents the concept of value assignment by (31)P qNMR measurements for the development of CRM and describes different approaches to establish traceability to primary Standard Reference Material from the National Institute of Standards and Technology (NIST SRM). Phosphonoacetic acid is analyzed as a water-soluble CRM candidate, whereas triphenyl phosphate is a good candidate for the use as qNMR reference material in organic solvents. These substances contain both nuclei, (1)H and (31)P, and the concept is to show that it is possible to indirectly quantify a potential phosphorus standard via its protons using (1)H qNMR. The same standard with its assigned purity can then be used for the quantification of an analyte via its phosphorus using (31)P qNMR. For the validation of the concept, triphenyl phosphate and phosphonoacetic acid have been used as (31)P qNMR standards to determine the purity of the analyte tris(2-chloroethyl) phosphate, and the resulting purity values perfectly overlap within their expanded measurement uncertainties.

No MeSH data available.