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Polyalphaolefin Hydrogenation – Residual Olefin Analysis – 1H NMR versus Bromine Number

by Benchtop NMR, NMR, PAT, Petroleum, Process NMR, qNMR, Reaction Monitoring

1H NMR is an excellent tool for monitoring the residual olefin content of polymers after hydrogenation reactions. The fact that the olefin fall in a unique region of the spectrum means that it is a straightforward measurement to quantify the %H present as olefin or to correlate that olefin content with other analyses such as bromine number. Here is an example of a polyalphaolefin residual olefin analysis. The olefin proton content (%H) was plotted against bromine number values obtained on each of the samples. A linear correlation was obtain but two different correlations were observed that were dependent on the viscosity index of the polyalphaolefin being analyzed. Figure 1 shows the 1H NMR spectra obtained on neat samples on a Picospin-80 spectrometer operating at 82.3 MHz. The methyl and methlene protons of the polymer backbone are plainly seen and the olefin and alpha-olefin protons are observed.

1H NMR - Polyalphaolefins - Residual Olefin Analysis
Figure 1: 1H NMR – Polyalphaolefins – Residual Olefin Analysis

 

Figure 2 shows the linear correlation between %H olefin and bromine number with the two correlations caused by different VI grade being indicated. The analysis shows that for the two viscosity grades the grade can be identified from the linear correlation that the data falls onto and the %H olefins content can directly yield the bromine number. This NMR method provides an alternative to the following ASTM standards:                                                            D1159 Test Method for Bromine Numbers of Petroleum Distillates and Commercial Aliphatic Olefins by Electrometric Titration                                      D1491 Test Method for Test for Bromine Index of Aromatic Hydrocarbons by Potentiometric Titration                                                                         D1492  Standard Test Method for Bromine Index of Aromatic Hydrocarbons by Coulometric Titration                                                                             D2710 Test Method for Bromine Index of Petroleum Hydrocarbons by Electrometric Titration                                                                                      D5776 Test Method for Bromine Index of Aromatic Hydrocarbons by Electrometric Titration

Correlation of Olefin Content obtained by 1H NMR with Bromine Number in Polyalphaolefins
Figure 2: Correlation of Olefin Content obtained by 1H NMR with Bromine Number in Polyalphaolefins

Residual Catalytic Cracker – Heavy Petroleum Feedstream Properties from 1H NMR at 43 MHz

by Benchtop NMR, Chemistry, Chemometrics, Energy, NMR, PAT, Petroleum, Process NMR, qNMR, Reaction Monitoring, TD-NMR Tagged: , ,

Back in October we presented a talk at Gulf Coast Conference that concerned the prediction of the chemical and physical properties of heavy petroleum feeds being converted to higher value product in a residual catalytic cracker (RCC). Over the years we have analyzed these materials by 300 and 60 MHz NMR and obtained good PLS-regression models that can adequately predict properties for real-time process control and optimization in a petroleum refinery. With the advent of a large number of new benchtop NMR systems we have been convincing ourselves that these types of analyses can be performed by systems such as the Magritek Spinsolve 43 MHz. We ran a series of samples that had been sitting around our lab for 15 years by dissolving them at about 50 volume% in a 50/50 CDCl3/CS2 solvent system. For each sample we had laboratory test data for a number of chemical and physical properties of interest to process engineers. We regressed the lab data variability against the variability in the Magritek 43MHz 1H NMR spectra and obtained cross-validated PLS models. The presentation material is given here at this link – Gulf Conference Presentation – 43 MHz RCC Feedstream Regression Models

Beer and Cider Analysis – Example of Spectral Repeatability of Benchtop 60 MHz NMR System

by Beer, Benchtop NMR, Cider, NMR, qNMR Tagged: , , , ,

Here is an example of spectral reproducibility. We are doing a lot of beer NMR at the moment on our 300 MHz NMR and for “giggles” we are running many samples through the various bench-top systems in our lab. We have been quantifying small organic acids (lactic, acetic, succinic , malic, citric, etc.) as they can give some idea of yeast activities and health during fermentation. We are also quantifying  and studying the 1,4/1,6 linkage distribution of residual dextrins. The series of superimposed spectra below consists of 28 spectra of a freeze dried beer sample (a unique Belgian Dubbel. Each spectrum was 128 pulses and took approximately 30 minutes per spectrum. So the superimposed data represents a 14 hour continuous stability test.The data was automatically processed with 16K zero-fill and autophase.It looks pretty damn good.

Zoe Belgian Dubbel - Freeze Dried - 1H qNMR analysis. 128 superimposed spectra representing a 14 hour spectral reprodcibility and stability test.
Zoe Belgian Dubbel – Freeze Dried – 1H qNMR analysis. 128 superimposed spectra representing a 14 hour spectral reprodcibility and stability test.

 

We’ve been looking at a lot of sour beers – here is a home-brewed Flemish Red aged in an oak barrel – note the high lactic and acetic content.

Flemish Red Ale - Freeze dried - 1H NMR
Flemish Red Ale – Freeze dried – 1H NMR

We’ve also been analyzing a lot of hard ciders – commercial and home-brewed varitieties of various styles – very different from one sample to another in the small molecule and sugar chemistry.

Commercial Cider Example - Freeze Dried Sample - 1H NMR Analysis at 60 MHz
Commercial Cider Example – Freeze Dried Sample – 1H NMR Analysis at 60 MHz

 

Dry Basque Cider Example - Freeze Dried Sample - 1H qNMR Analysis
Dry Basque Cider Example – Freeze Dried Sample – 1H qNMR Analysis

 

1H qNMR at 300MHz or 60 MHz can be utilized to identify and quantify small molecule chemistry in fermentations. Below is an example of a quantitative chemistry report on a series of ciders.

Table - 1H qNMR - SMall Molecule and Sugars Analysis
Table – 1H qNMR – SMall Molecule and Sugars Analysis

 

Beer and Cider Analysis is offered with similar quantitative results is offered for $100 per sample in our analytical lab.

Benchtop NMR – Screening Tool for Adulterated Herbal Supplements

by Benchtop NMR, Chemistry, Herbal Supplement, NMR

Survey of Low Field NMR Spectrometer Platforms for Successful Screening of Sexual Enhancement and Weight Loss Supplements for Adulteration with Drugs and Drug Analogs

John C Edwards1, Kristie M Adams2, and Anton Bzhelyansky2

1Process NMR Associates, Danbury, CT
2United States Pharmacopeial Convention, Rockville, MD

The adulteration of dietary supplements (or natural health products) with synthetic pharmaceuticals is an area of increasing concern, which presents substantial risk to public health. Widely available in retail and via the Internet, these products are often marketed as sexual enhancement, weight loss and/or bodybuilding supplements. Unlike prescription drugs, supplements do not require premarket approval by FDA before they are made available for public consumption. In fact, the agency can only take investigational action after the adulterated product has caused harm and the adverse event has been reported via MedWatch (FDA’s online portal for voluntary reporting of adverse events associated with drugs, medical devices and dietary supplements).
Development of analytical tools for screening and identification of adulterated products in the marketplace represents a significant step forward in the fight against adulterated dietary supplements. Several organizations, including AOAC and USP, have undertaken initiatives to evaluate and recommend analytical methodologies for screening supplements for adulteration. HPLC and mass spectrometry have so far dominated the screening and quantitation studies published in the literature, with NMR spectroscopy often relegated to the status of structure elucidation tool. In this work, we investigate the ability of several-low field NMR spectrometric platforms to successfully identify and quantify the presence of adulterating drug substances in sexual enhancement and weight loss supplements purchased online and in US retail. 1H qNMR of both types of samples was performed with 300 MHz NMR to confirm the presence of adulterants such as sildenafil, tadalafil, and their structural analogues (sexual enhancement supplements) and various synthetic stimulants (weight loss supplements). We have concluded that a simple sample preparation protocol combined with straightforward 1H NMR spectroscopic analysis yields a rapid, robust and reliable screening test for adulterated supplements, presenting an attractive alternative to more labor-intensive, expensive and expertise-demanding techniques du jour.

This was presented by John Edwards at SMASH in September 2014, and at the Carolina NMR Symposium in November 2014

presentation can found here: Benchtop NMR – Herbal Supplement Adulteration Screening

43 MHz - 1H NMR - Benchtop Analysis of Contamination of herbal supplements with PDE5 inhibitors
43 MHz – 1H NMR – Benchtop Analysis of Contamination of herbal supplements with PDE5 inhibitors
300 MHz - 1H NMR - Benchtop Analysis of Contamination of herbal supplements with PDE5 inhibitors
300 MHz – 1H NMR – Benchtop Analysis of Contamination of herbal supplements with PDE5 inhibitors

Nutritional Supplement and Diesel Fuel Application Development for Benchtop NMR Systems Operating at 42, 60, and 80 MHz – Equivalency with Supercon NMR

by Benchtop NMR, Chemometrics, Energy, Herbal Supplement, NMR, PAT, qNMR

Benchtop high-resolution NMR systems are available at a number of field strengths and probe configurations. However beyond the obvious academic instruction market for these instruments very few applications have been demonstrated across all available platforms and thus proving the general applicability of benchtop NMR technology to industrial quality control. We will present two chemometric-based applications that have been developed at 4 different field strengths utilizing Varian Mercury 300 MHz, Magritek Spinsolve 42 MHz, Aspect AI 60 MHz, and Thermo Picospin 80 MHz NMR systems. Partial-least-squares (PLS) regression correlations were obtained on all 4 platforms relating to:
1) Omega-3 fatty acid composition of samples taken from various points in a nutritional supplement manufacturing process. Excellent correlations were obtained on all 4 NMR instruments proving that NMR technology is applicable to in-lab, at-line. or on-line analysis of fish oil derived omega-3 fatty acid supplements. The 40 second NMR analysis effectively replaces a 60+ minute GC analysis.
2) Physical and chemical property determination of diesel fuels where excellent correlations were obtained between 1H NMR variability and parameters such as density, aromatic content by GC, hydrogen content by 1H TD-NMR (ASTM D7171 method), and sulfur content. Many more physical and chemical properties can be correlated to the 1H NMR spectrum allowing a single 40 second NMR experiment to predict 10-15 parameters that each require dedicated analyzers.
Finally, we will present the concept and initial results from an independent server-based NMR application software that can be utilized in conjunction with the NMR software of the current benchtop NMR systems, or alternatively as a stand-alone application platform. This software would effectively make chemometric and direct measurement NMR application ubiquitous across all NMR platforms.

A link to this presentation in PDF form is given here: PLS-Regression – 300_80_60_43 MHz NMR of Fish Oil Supplements and Diesel Fuel