Relative molar sensitivities of carnosol and carnosic acid with respect to diphenylamine allow accurate quantification of antioxidants in rosemary extract

[Determination of Allyl Isothiocyanate in Mustard and Horseradish Extracts by Single Reference GC and HPLC Based on Relative Molar Sensitivities]

The main component of the Mustard and Horseradish extracts, which are used as natural food additives in Japan, is allyl isothiocyanate (AITC). The determination of AITC using GC-FID is the official method employed in the quality control assessments for these products. In this method, a commercially available AITC reagent is used as a calibrant. However, ¹H-quantitative NMR (qNMR) analysis revealed that the AITC reagents contain impurity. Therefore, we examined the GC-FID and HPLC-refractive index detector (LC-RID) method based on relative molar sensitivities (RMSs) to high-purity single reference (SR). The RMSs of AITC/SR under the GC-FID and LC-RID conditions were accurately determined using qNMR. The AITC in two types of food additives was quantified using qNMR, SR GC-FID, and SR LC-RID methods. Both SR GC-FID and SR LC-RID showed good agreement within 2% with the AITC content determined by direct qNMR.

Quantification of tea-derived catechins without the requirement for respective calibration curves by single reference liquid chromatography based on relative molar sensitivity

BACKGROUND

Many studies report the monitoring of catechins in tea samples by chromatographic techniques. Unfortunately, only a small number of screening assays for catechins exist as a result of the complexity of authentic standards for the respective calibration curves. In the present study, a single reference (SR) exhaustive assay for the simultaneous quantification of tea-derived catechins by liquid chromatography (LC) with photodiode array and fluorescence detectors based on relative molar sensitivity (RMS) was developed as a screening assay of common tea samples without respective calibration curves using authentic standards.

RESULTS

Three original SR standards were proposed based on flavonoid structures, evaluated by quantitative ¹ H-NMR based on an indirect standard (1,4-bis(trimethylsilyl) benzene-d₄ ) and successfully separated in a LC chromatogram. In tea samples with these added SR calculated based on RMS, the concentrations of eight tea-derived catechins could be measured with a relative SD of < 8.5% by a single LC run.

CONCLUSION

This LC screening assay based on RMS allows reliable quantification without the requirement for respective calibration curves using authentic standards. © 2020 Society of Chemical Industry.

Use of Relative Molar Sensitivity as a Specific Value for Evaluating Heptaoxyethylene Dodecyl Ether Concentrations in Methanol Solution

Relative molar sensitivity (RMS) determined using quantitative ¹H NMR and HPLC with a refractive index (RI) detector was applied as a specific value for quantifying the levels of heptaoxyethylene dodecyl ether (HOEDE), a typical non-ionic surfactant, in methanol solutions. RMS was robust against changes of the analytical conditions (i.e., RI cell temperature, acetonitrile content in the mobile phase, HPLC system). Furthermore, the obtained HOEDE concentrations using a previously evaluated RMS were comparable to those obtained using a reference method for over 1 year.

Development of an HPLC method with relative molar sensitivity based on 1H-qNMR to determine acteoside and pedaliin in dried sesame leaf powders and processed foods

A high-performance liquid chromatography (HPLC) method with relative molar sensitivity (RMS) based on 1H quantitative NMR spectroscopy (1H-qNMR) has been developed for food ingredients such as acteoside (verbascoside) and pedaliin (pedalitin-6-O-glucoside) without requiring authentic and identical standards as the reliable analytical methods. This method is used methyl 4-hydroxybenzoate (MHB) as an alternative reference standard. Each RMS is also calculated from the ratio of each analyte's molar absorption coefficient to that of MHB after correcting the purities of the analytes and reference standard by 1H-qNMR. Therefore, this method can quantify several analytes with metrological traceability to the International System of Units (SI) using the RMS and one alternative reference standard. In this study, the content of acteoside and pedaliin in several samples, such as dried sesame leaf powders and commercially processed foods, can be determined by the proposed RMS method and demonstrated in good agreement that obtained by a conventional method. Moreover, the proposed method yields analytical data with SI-traceability without the need for an authentic and identical analyte standard. Thus, the proposed RMS method is a useful and practical tool for determining acteoside and pedaliin in terms of the accuracy of quantitative values, the routine analysis, and the cost of reagents.

Determination of perillaldehyde in perilla herbs using relative molar sensitivity to single-reference diphenyl sulfone

Perillaldehyde (PRL) is one of the essential oil components derived from perilla plants (Perilla frutescens Britton) and is a characteristic compound of the traditional medicine "perilla herb ()" listed in the The Japanese Pharmacopoeia, 17th edition (JP17). HPLC using an analytical standard of PRL has been used to quantitatively determine the PRL content in perilla herb. However, PRL reagents have been reported to decompose easily. In this study, we utilized an alternative quantitative method using on a single reference with relative molar sensitivity (RMS) based on the results of experiments performed in two laboratories. It was possible to calculate the exact RMS using an offline combination of ¹H-quantitative NMR spectroscopy (¹H-qNMR) and an HPLC/photodiode array (PDA) detector (or an HPLC/variable-wavelength detector [VWD]). Using the RMS of PRL to the single-reference compound diphenyl sulfone (DFS), which is an inexpensive and stable compound, the PRL content in the perilla herb could be determined using HPLC/PDA or HPLC/VWD without the need for the analytical standard of PRL. There was no significant difference between the PRL contents of perilla herb determined using the method employing the single-reference DFS with RMS and using the JP17 assay, the calibration curve of which was generated using the analytical standard of PRL with adjusted purity measured by ¹H-qNMR. These results demonstrate that our proposed method using a single reference with RMS is suitable for quantitative assays of perilla herb and can be an alternative method for the current assay method defined in the JP17.