Liquid chromatography with isotope-dilution mass spectrometry for determination of water-soluble vitamins in foods

Recent advances in flexible and wearable sensors for monitoring chemical molecules

In recent years, real-time health management has received increasing attention, benefiting from the rapid development of flexible and wearable devices. Conventionally, flexible and wearable devices are used for collecting health data such as electrophysiological signals, blood pressure, heart rate, etc. The monitoring of chemical factors has shown growing significance, providing the basis for the screening, diagnosis, and treatment of many diseases. Nowadays, in order to understand the health status of the human body more comprehensively and accurately, researchers in the community have started putting effort into developing wearable devices for monitoring chemical factors. Progressively, more flexible chemical sensors with wearable real-time health-monitoring functionality have been developed thanks to advances relating to wireless communications and flexible electronics. In this review, we describe the variety of chemical molecules and information that can currently be monitored, including pH levels, glucose, lactate, uric acid, ion levels, cytokines, nutrients, and other biomarkers. This review analyzes the pros and cons of the most advanced wearable chemical sensors in terms of wearability. At the end of this review, we discuss the current challenges and development trends relating to flexible and wearable chemical sensors from the aspects of materials, electrode designs, and soft-hard interface connections.

Revised D-A-CH Reference Values for the Intake of Vitamin B6

BACKGROUND

The Nutrition Societies of Germany, Austria, and Switzerland as the joint editors of the "D-A-CH reference values for nutrient intake" have revised the reference values for vitamin B6 in summer 2019.

SUMMARY

For women, the average requirement (AR) for vitamin B6 intake was derived on the basis of balance studies using a pyridoxal-5'-phosphate (PLP) plasma concentration of ≥30 nmol/L as a biomarker of an adequate vitamin B6 status. The recommended intake (RI) was derived considering a coefficient of variation of 10%. The RIs of vitamin B6 for men, children, and adolescents were extrapolated from the vitamin B6 requirement for women considering differences in body weight, an allometric exponent, growth factors as appropriate, and a coefficient of variation. For infants aged 0 to under 4 months, an estimated value was set based on the vitamin B6 intake via breast feeding. The reference value for infants aged 4 to under 12 months was extrapolated from the estimated value for infants under 4 months of age and the average vitamin B6 requirement for adults. The reference values for pregnant and lactating women consider the requirements for the foetus and the loss via breast milk. Key Messages: According to the combined analysis of 5 balance studies, the AR for vitamin B6 to ensure a plasma PLP concentration of ≥30 nmol/L is 1.2 mg/day for adult females and the extrapolated AR for adult males is 1.3 mg/day. The corresponding RIs of vitamin B6 are 1.4 mg/day for adult females and 1.6 mg/day for adult males, independent of age. For infants, the estimated value is 0.1 mg/day and 0.3 mg/day, depending on age. The AR of vitamin B6 for children and adolescents ranges between 0.5 and 1.5 mg/day, and the RI is between 0.6 mg/day and 1.6 mg/day. During pregnancy, the AR is 1.3 mg/day in the first trimester and 1.5 mg/day in the second and third trimesters; the RI is 1.5 mg/day in the first trimester and 1.8 mg/day in the second and third trimesters. For lactating women, the AR is 1.3 mg/day and the RI is 1.6 mg/day.

Rapid Method for the Determination of Thiamine and Pantothenic Acid in Infant Formula and Milk-Based Nutritional Products by Liquid Chromatography‒Tandem Mass Spectrometry

Background

Thiamine and pantothenic acid play a critical role in numerous metabolic reactions and are typically supplemented in infant and adult nutritional formulas as thiamine chloride hydrochloride and calcium pantothenate salts.

Objective

A rapid compliance method for the analysis of thiamine and pantothenic acid applicable to infant formula and milk-based nutritional products is described.

Method

Proteins are removed by centrifugal ultrafiltration, followed by analysis by reversed-phase liquid chromatography‒tandem mass spectrometry (LC-MS/MS), with quantitation accomplished by internal standard technique.

Results

The method was shown to be accurate, with acceptable recovery (thiamine, 99.3–101.1%; pantothenic acid, 99.2–108.6%). A certified reference material (NIST 1849a), showed no statistical bias (α = 0.05) for thiamine (P = 0.64); although a statistically significant bias (P < 0.01) for pantothenic acid was found, the nominal bias was only 4.7% (mean = 7.1 mg/hg; certified value = 6.8 mg/hg). A comparison of results by LC-MS/MS and current methods showed negligible bias (mean bias: thiamine, 0.01 mg/hg; pantothenic acid, 0.17 mg/hg) and no statistical significance (α = 0.05; thiamine, P = 0.399; pantothenic acid, P = 0.058). Acceptable precision was demonstrated with a repeatability of 7.2% repeatability relative standard deviation (RSDr) (HorRat: 0.6) and an intermediate precision of 7.0% RSD for thiamine, and a repeatability of 5.7% RSDr (HorRat: 0.5) and an intermediate precision of 6.1% RSD for pantothenic acid.

Conclusions

This rapid method is intended for use in high-throughput laboratories as part of routine product compliance release testing of thiamine and pantothenic acid in manufactured infant and milk-based nutritional products.

Comprehensive and quantitative profiling of B vitamins and related compounds in the mammalian liver

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A validated method for quantification of 13 B vitamins and four related compounds in sheep liver.

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Limits of detection for the majority of analytes were within the range of 0.4–3.2 pmol/g.

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Simple sample extraction procedure with high throughput.

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Successfully applied to profile 1C major forms in 266 sheep liver samples.

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Potential for dietary and genetic studies in metabolic health and epigenetic gene regulation.

A method for the simultaneous quantification of B vitamins and related amines in one-carbon (1C) metabolism would benefit the study of diet and genetic/epigenetic regulation of mammalian development and health. We present a validated method for the simultaneous quantitative analysis of 13 B vitamers and four related 1C-pathway amine intermediates in liver using hydrophilic interaction chromatography (HILIC) coupled to electrospray ionization tandem mass spectrometry. Frozen sheep liver samples (50 mg) were homogenized in cold 50% acetonitrile containing 1% acetic acid with the addition of two isotope labelled internal standards. Hot acid hydrolysis was applied to release the protein-bound forms. The separation of 17 analytes was achieved using a pHILIC column with a total run time of 13 min. Detection was achieved in electrospray positive ionisation mode. Limits of detection for the majority of analytes were within the range of 0.4–3.2 pmol/g. The method was applied to 266 sheep liver samples and revealed that adenosylcobalamin, methylcobalamin, pyridoxic acid, flavin adenine dinucleotide and thiamine were the major forms of the B vitamers present with pyridoxal 5′-phosphate and thiamine pyrophosphate being detected at lower concentrations. Trimethylglycine and methylglycine were the predominant 1C-related amines measured. As anticipated, the B vitamin status of individuals varied considerably, reflecting dietary and genetic variation in our chosen outbred model species. This method offers a simple sample extraction procedure and provides comprehensive coverage of B vitamins coupled with good sensitivity and reliability.

Evolution of reference materials for the determination of organic nutrients in food and dietary supplements-a critical review

For over 40 years, food-matrix certified reference materials (CRMs) have been available for determination of trace element content, and a wide variety of materials are available from most producers of CRMs. However, the availability of food-matrix CRMs for organic nutrients has been more limited. The European Commission (EC) Bureau Communautaire de Référence (BCR) and the National Institute of Standards and Technology (NIST) introduced food-matrix CRMs with values assigned for vitamins and other organic nutrients such as fatty acids and carotenoids in the 1990s. The number of organic nutrients for which values were assigned has increased significantly in the past decade, and the approach and analytical methods used for assignment of the certified values have also evolved. Recently, dietary supplement-matrix CRMs such as multivitamin tablets with values assigned for vitamins and carotenoids, and fish and plant oils with values assigned for fatty acids have appeared. The development, evolution, and improvement of food- and dietary supplement-matrix CRMs for determination of vitamins, carotenoids, and fatty acids are described, with emphasis on CRMs made available in the past 10 years. Recent food and dietary supplement CRMs for the determination of organic nutrients include infant formula, multivitamin tablets, milk and egg powders, breakfast cereal, meat homogenate, blueberries, soy flour, fish and plant oils, dry cat food, and protein drink powder. Many of these food- and supplement-matrix CRMs have values assigned for over 80 organic and inorganic nutrients, toxic elements, proximates, and contaminants. The review provides a critical assessment of the challenges and evolving improvements in the production and the analytical methods used for value assignment of these CRMs. The current status and future needs for additional food- and dietary supplement-matrix CRMs for organic nutrients are also discussed. Graphical abstract Food Composition Triangle with currently-available food-matrix certified reference materials (CRMs) for the determination of organic nutrients positioned according to fat, protein, and carbohydrate composition.

Rapid and sensitive screening of some acidic micronutrients in infant foods by HPLC with fluorescent detector

BACKGROUND

Currently, commercially prepared complementary foods have become an important part of the diet of many infants and toddlers. But the method for simultaneous analysis of different types of micronutrient remains poorly investigated, which hinders the rapid and comprehensive quality control of infant foods. In the presented study, we first tried to employ the fluorescence labeling strategy combined with high-performance liquid chromatography-fluorescence detection for simultaneous determination of some acidic micronutrients including biotin, nicotinic acid, linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, arachidonic acid and linoleic acid in infant foods.

RESULTS

2-(5-Benzoacridine) ethyl-p-toluenesulfonate was used as the fluorescence labeling reagent for simultaneous labeling of the seven components. The labeling conditions were optimized systematically by response surface methodology. The correlation coefficients for the calibration curves of the tested compounds ranged from 0.9991 to 0.9998. Limits of detection were in the range of 1.99-3.05 nmol L(-1) . Relative standard deviation values of retention time and peak area of seven compounds were less than 0.05% and 0.75%, respectively. The intra- and inter-day precision was in the range of 1.81-3.80% and 3.21-4.30%, respectively. When applied to analysis of several infant foods it showed good applicability.

CONCLUSION

The developed method has been proven to be simple, inexpensive, selective, sensitive, accurate and reliable for analysis of some acidic micronutrients in infant foodstuffs. Furthermore, this developed method also has powerful potential in the analysis of many other complementary foodstuffs. © 2015 Society of Chemical Industry.

Electrochemical signatures of multivitamin mixtures

Distinct electrochemical signatures of multivitamins using cyclic square wave voltammetry at a disposable screen printed electrode.