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ASTM F2259-03 (2008) – Determining the Chemical Composition of Alginates by 1H NMR Spectroscopy

by Chemistry, Herbal Supplement, NMR

Alginate is a linear polysaccharide composed of mannuronate (M) and a-L-guluronate (G). The polysaccharide is characterized by the relative ratio of M/G, G-Content, and average length of blocks of G in the polymer. M and G are:

ASTM F2259 recounts the standard sample preparation and 1H NMR analysis that allows the following parameters to be calculated:

The 1H Spectra obtained on a typical alginate sample are show below:


Finally the peaks representing the individual M and G components and sequences are deconvoluted from the spectrum.
The intensities obtained from the deconvolution are input into the excel spreadsheet shown above and the various ratios, M and G content and a series of diads and triads are calculated along with some G block lkength information. It is the block length information that often reveals telling differences between samples.

Process NMR Associates performs this analysis at a cost of $225 per sample. The samples, however, must be prepared by the customer using the methodology set forth in the test method.

The Role of NMR in FDA Mandated Identity Testing of Nutritional Supplements

by Chemistry, Herbal Supplement, NMR

Process NMR Associates Offers Testing, Consultation, and Support in Meeting Your Identity Testing, Laboratory Methodology, and Process Analytical Requirements for FDA DS CGMP Rule Compliance.

In conjunction with 21 CFR 111, the FDA’s Office of Nutrition, Labeling and Dietary Supplements has instituted the Dietary Supplement Current Good Manufacturing Practice Rule (DS GCMP Rule) and the Interim Final Rule effective December 2010. Laboratory compliance, including identity testing and analytical method protocols are now required for any manufacturer, packager, labeler or holder of dietary supplements without the previous exemption based on number of full time employees within the company. Smaller companies, typically without in-house laboratory and testing facilities, now need to obtain such services to meet the new compliance rules.

Process NMR Associates (PNA), the process analytical consulting company and analytical testing company with over 45 years of experience in the field of nuclear magnetic resonance spectroscopy (“NMR”) and organic spectroscopy (FTIR, NIR, ESR) is now offering expanded services for DS GCMP Rule compliance. As an example, The International Aloe Science Council (IASC), a trade association representing the global aloe vera industry, has selected Process NMR Associates, LLC (PNA) as its primary provider for Nuclear Magnetic Resonance (NMR) spectroscopic measurement of aloe vera. PNA’s services include measurement of aloe vera concentration, sacharride distributions, formulation ingredients, and, contaminant/degradation products, in aloe vera powders, whole leaf extracts, whole leaf and inner leaf gel concentrates, drink concentrates, and, ready to drink formulations. PNA’s NMR services are an integral part of the IASC certification and compliance program. “We are pleased to partner with Process-NMR Associates for providing analytical services related to the certification program,” said Devon Powell, Executive Director of the IASC. “PNA has demonstrated its capability to provide excellent analytical services in a timely manner to the organization and aloe vera industry at-large.”

Expanding analyses and methodologies beyond aloe vera include essential oil analyses, fish oils and omega-3 fatty acid analyses, herbal supplement characterization, adulteration monitoring, and, ingredient integrity analyses. It is PNA’s commitment to quality analytical services, sample analysis, reporting turnaround, and competitive pricing that enable us to provide value-added services to the dietary supplement market place.

60 MHz NMR of Essential Oils from Benchtop System – Comparison to 300 MHz NMR Data

by NMR

A comparison of the non-spinning 60 MHz NMR data compared with that obtained on a superconducting 300 MHz system are shown below for 10 Essential Oils – those essential oils are: Copaibo Balsam, Dill Weed, Citronella, Parsely Seed, Cinnamon Leaf, Balsam (Peru), Ginger, Eucalyptus Globulus, Petitgrain, Vetiver.

Copaibo Balsam NMR Analysis
Dill Weed Essential Oil - NMR Analysis
Citronella Essential Oil - NMR Analysis
Parsley Seed Essential Oil - NMR Analysis
Cinnamon Leaf Essential Oil - NMR Analysis
Balsam - Peru - Essential Oil - NMR Analysis
Eucalyptus Globulus - NMR Analysis
Ginger Essential Oil - NMR Analysis
Petitgrain Essential Oil - NMR Analysis
Vetiver Essential Oil - NMR Analysis

We currently have a database of 1H (60 and 300 MHz) and 13C NMR data of around 110 essential oils.

For further details on NMR analysis of essential oils please contact John Edwards

Solid-State 13C NMR Analysis of Herbal Supplements

by NMR

Solid-state 13C NMR is an excellent way to investigate what chemical functionality is present in herbal supplements. The large resonances at 60-105 ppm are due to cellulose/polysaccharides and some sugars. The peaks in the 0-60 ppm region are aliphatic carbons in fatty acid chains. Peaks in the 110-140 ppm region are alkene and aromatic carbons, while peaks in the 140 ppm and 150 ppm region are due to substituted aromatics and phenolic carbons. Peaks in the 160-200 ppm region are due to carboxylic acids, esters and amides. Solid-state NMR is a relatively simple technique that involves no sample preparation and observes the sample carbon chemistry in it’s entirety. The analysis reveals relative amounts of chemical functionality that can be utilized for product-to-product comparison or batch-to-batch manufacturing comparison. The chemical specificity of the technique also means that adulterants can readily be detected and identified. A few examples of “off the shelf” herbal supplements are shown below.

Solids 13C NMR of Green Tea - Cranberry - Milk Thistle

Figure 1: 13C CP-MAS NMR of Cranberry Extract, Green Tea Extract, and Milk Thistle Extract

Solids 13C NMR - Bilberry - Echinecea - Black Cohosh

Figure 2: 13C CP-MAS NMR of Black Cohosh Root Extract, Echinecea Powder, and Bilberry Extract

13C NMR of Valerian Ginseng Saw Palmetto, St Johns Wort

Figure 3: 13C CP-MAS NMR of Valerian Root Extract, Ginseng Extract, Saw Palmetto Extract, Grape Seed, and St John’s Wort.

For further details on these analyses and their utilization in quality control contact John Edwards

Benchtop Permanent Magnet High Resolution NMR Systems

by NMR, Process NMR

The latest buzz in the NMR news release world has been the emergence of the 45 MHz picoSpin (www.picospin.com) miniature NMR system that boasts shoe box size dimensions, a resolution of 80 ppb (3.5 Hz at peak half height), and a tiny 300 micron probe dimension. The sample can be injected with a syringe or pump. A number of application examples and spectra are posted on the application pages of the company website. It is noted that the spectra require the signal averaging of 24-200 pulses requiring an estimated experimental time of 3-10 minutes

The system claims to be the first miniature NMR system but I guess that depends on how you define “miniature”. A number of “relatively small” high resolution permanent magnet NMR systems operating at 60 MHz have been around since the early ’90s (Elbit-ATI, FoxboroNMR, Qualion, ASPeCT-MR, and ACT). The picoSpin NMR is definitely the first spectrometer to deliver high resolution NMR from such a small footprint permanent magnet combined with a capillary probe. The S/N of the picoSpin system is approximately 300:1 on a one pulse spectrum of water. On our 60 MHz systems we are routinely obtaining, non-spinning, one pulse spectra without signal apodization with a S/N of 1600:1 for a 5 mm sample size, and 3600:1 for a 10 mm sample size. Very little degradation of spectrum quality is observed moving from 5-10 mm probe systems. The 5mm lineshape spec is typically LW(50%)=2 Hz (34 ppb), LW(10%)=6 Hz, LW(0.5%)=20 Hz. For the 10 mm probe the spec is typically LW(50%)=2.5 Hz (43 ppb), LW(10%)=13 Hz, LW(0.5%)=80 Hz. We have many example spectra posted on this blog and on our website.

The S/N obtained with 5mm and 10mm sample dimensions represent a 28 and 144 fold improvement of sensitivity compared to the S/N obtained on the picoSpin system. This is a vitally important difference between these two technologies. One yields a useful, repeatable spectrum at a high S/N level after every pulse (4-5 seconds between spectra) while the other requires 100x longer time frame to obtain the same result. In the realm of reaction monitoring this time difference is a huge factor as a reaction can be at completion in a few minutes but an NMR analyzer providing a spectrum every 5 seconds allows dozens of observations to be performed in a short 2 minute reaction. The larger sample dimension in the 60 MHz systems also has the advantage of allowing a much wider range of industrial sector samples to be analyzed with respect to sample viscosity, contamination levels, sample temperature, and “particulate content”.

The picoSpin spectrometer does have a wonderful and truly portable package and will find many applications in university general chemistry labs and in QA/QC of liquid products, but I am not sure that it will have the stability and high sensitivity to allow it’s use in real time process control and reaction monitoring where the samples are complex mixtures, at high temperature, often with particulates present. Also the small probe dimension will mean that the analysis of flowing samples will be extremely difficult because of the small sample volume being analyzed.

Process NMR Associates is currently investigating the possibility of reducing the foot print of their 60 MHz NMR system to a platform that would support a 5 mm sample dimension operating at 60-80 MHz. The magnet would be closer to 50 lbs in weight in this scenario, and with a small FPGA based spectrometer would be a powerful mobile NMR system. However, I do not have a feel for whether the NMR and broader analytical community will be willing to accept the idea of low priced NMR systems selling in the $20-70K range. The question remains….if you build it, will they come? I would be interested to hear any comments on the utility of NMR in the field based on permanent magnet technologies at NMR frequencies of 45-80 MHz. Please address any comments to John Edwards.