Simultaneous quantification of Vitamins A, D3 and E in fortified infant formulae by liquid chromatography–mass spectrometry

Assessment of Regulatory Compliance Testing for Vitamin D in Infant Formula—Impact of Delegated Regulation (EU) 2019/828

Background

Since the publication of Standard Method Performance Requirements (SMPR®) for vitamin D in infant formula (SMPR 2011.004) by AOAC INTERNATIONAL, revised vitamin D limits have been recommended by the European Food Safety Authority (EFSA) for infant formula and adopted in Commission Delegated Regulation (EU) 2019/828. The vitamin D range introduced, 2–2.5 μg/100 kcal, is significantly narrower than previous limits specified by Codex Standard 72–1981 and requires lower method reproducibility metrics to adequately assess regulatory compliance. The narrower limits for vitamin D present a significant challenge for current-generation reference analytical methods that comply with SMPR 2011.004.

Objective

We evaluate the impact of Delegated Regulation (EU) 2019/828 on the demonstrated performance of AOAC Method 2016.05/ISO 20636:2018 to assess the likelihood that vitamin D results produced by the method would be found outside the EU limits when testing infant formula that is compliant as manufactured.

Methods

AOAC Method 2016.05/ISO 20636:2018, specifically data generated during multi-laboratory study, was used as a basis for statistical evaluation of the impact of the narrower EU vitamin D limits.

Results

The review of AOAC Method 2016.05/ISO 20636:2018 method performance against the vitamin D regulatory range introduced in (EU) 2019/828 indicates methods capable of performing in alignment with SMPR 2011.004 are likely to produce results that fail to meet EU requirements.

Conclusions

Our assessment illustrates the high probability that a well-manufactured product with vitamin D levels within the EU regulatory range would fail to meet the regulatory requirements due to analytical method variability when tested using fit-for-purpose methods. Further, required method performance cannot be expected with the future development of new methods. To avoid this, consideration should be given to aligning proposed regulatory limits with method performance metrics of current-generation compendial methods.

Highlights

Current, state-of-the-art methods cannot consistently verify infant formula product compliance for vitamin D in accordance with (EU) 2019/828.

Simultaneous Determination of Retinols and Tocols in Egg and Milk Products Based on RP-HPLC Linked with Fluorescent and Photodiode Array

In this paper, we built a method of verifying the 4 retinols of vitamin A and 8 tocopherol isomers of vitamin E in the food industry based on RP-HPLC-PDA-FLR. The effect of laboratory light conditions on the target components was considered for the first time, and it was found that the loss rate of the target components was the smallest in the case of a white laboratory bench with red or LED light in the dark room. There was no finding of extraction recoveries of the target components with a significant difference under different saponification conditions. Meanwhile, it was found that using ethyl acetate/n-hexane mixed solvent as the extraction solvent could ensure the effective extraction of the target components. Finally, baseline separation of 12 components was achieved within 45 min using the C30 column. With the help of methodological verification, we found that the recovery rate ranged from 76.45% to 93.52%, and RSD was between 0.19% and 12.99%; the Limit of Detection minimum value was 0.01 mg/100 g and the Limit of Quantitation minimum value was 0.03 mg/100 g. The detection method was successfully applied to the distribution detection of 4 kinds of retinols and 8 kinds of vitamin E in egg and dairy products and provided technical support for the accurate nutritional evaluation of vitamin A and vitamin E.

Determination of retinol and carotenoids in selected Malaysian food products using high-performance liquid chromatography (HPLC)

The presented method is focused on simultaneous determination of retinol and two carotenoids (lutein, β-carotene) in selected Malaysian food products. A Dionex Ultimate 3000 Series High-Performance Liquid Chromatography system equipped with two Dionex Acclaim Polar Advantage II C18 columns was utilized in this study. Simultaneous elution of retinol, lutein and β-carotene was achieved within 45 min with gradient profile of methanol and ultra-pure water (95:5–100:0–95:5) programmed at 0.8 mL/min flow rate and 30 °C. Retinol was acquired at 325 nm while lutein and β-carotene were acquired at 440 nm. Limits of detection and quantification of retinol and lutein were at 0.10, 0.34 µg/mL, and 0.08, 0.26 µg/mL; respectively while higher levels were observed for β-carotene at 1.06 and 3.54 µg/mL. Linearity test indicated R2 of 0.996–0.999, along with high accuracy (71.92–116.29%) and excellent repeatability for all analytes. Extraction efficiency was determined using standard addition into representative food product with recovery obtained in the range of 61.86–116.90% for all three analytes. The developed in-house HPLC method incorporates an enclosed solid-phase extraction system that is believed to further improve sample purification and analytes detection. On the whole, the developed on-line SPE-HPLC technique and efficient sample pre-treatment is deemed a reliable approach for simultaneous determination of retinol, lutein and β-carotene, as analyzed among the selected Malaysian food products. Additionally, the described procedure could also benefit routine analysis of these analytes in other food matrices or for determination of other analytes with similar chemistry and faster elution.

Lipid-soluble vitamins from dairy products: Extraction, purification, and analytical techniques

Milk and dairy products are considered as essential sources of lipid-soluble vitamins (LSVs) for human nutrition. Due to the lower concentrations, complexity, and instability of LSVs during extraction, their quantification remains challenging. This review focus on advances in the extraction and quantification of LSVs from different dairy products. Saponification, and liquid-liquid (LLE), solid-phase (SPE), and supercritical fluid (SFE) extraction methods, as well as dispersive liquid-liquid microextraction, are the most common techniques. Liquid chromatography-mass spectrophotometry (LC-MS) has unique advantages for LSVs determination and quantification due to its high sensitivity and specificity.

Vitamin D composition of Australian foods

Australia needs accurate vitamin D food composition data to support public health initiatives. Previously, limitations in analytical methodology have precluded development of a comprehensive database. We used liquid chromatography with triple quadrupole mass spectrometry (LC-QQQ) to analyse 149 composite samples representing 98 foods (primary samples n = 896) in duplicate for vitamin D₃, 25-hydroxyvitamin D₃ (25(OH)D₃), vitamin D₂, 25(OH)D₂. The greatest concentrations of vitamin D₃ were found in canned salmon and a malted chocolate drink powder (fortified); chicken eggs and chicken leg meat contained the most 25(OH)D₃. Margarine (fortified) and chocolate contained the greatest concentrations of vitamin D₂, with smaller amounts found in various meat products. 25(OH)D₂ was detected in various foods, including meats, and was quantitated in lamb liver. These data advance knowledge of dietary vitamin D in Australia and highlight the importance of analysis of these four forms of vitamin D to accurately represent the vitamin D content of food.

Comparative Study for the Determination of Fat-Soluble Vitamins in Rice Cereal Baby Foods Using HPLC-DAD and UHPLC-APCI-MS/MS

Two liquid chromatographic systems, one coupled to atmospheric pressure chemical ionization and tandem mass spectrometric methods (UHPLC-APCI-MS/MS) and the other a high-performance liquid chromatographic coupled to diode array detector (HPLC-DAD) were used to develop and validate methods for the simultaneous determination of fat-soluble vitamins A, D3 and E in rice cereal baby foods. The chromatographic separation was performed on C18 columns with a mixture of methanol-acetonitrile as mobile phase for all methods. The extraction of fat-soluble vitamins included enzymatic hydrolysis with α-amylase, saponification, extraction with petroleum ether or n-hexane and purification with silica cartridge (only for vitamin D3). Quantification of vitamin D3 and E through UHPLC-APCI-MS/MS was performed by the use of internal standards (IS) D3-d3 and E-d6, respectively, while IS was not used for vitamin A. The methods were optimized and validated in terms of linearity, precision, trueness, limits of detection and quantification. The recoveries were in the range of 85.0-107% for retinol, 92.0-105% for α-tocopherol and 95.2-106% for cholecalciferol and the %RSD (Relative Standard Deviation) values ranged from 6.4% to 15%. The evaluation of the methods was also conducted through the estimation of uncertainties, the application in commercial samples and the participation in a proficiency test.

Quantification of vitamin D3 and 25-hydroxyvitamin D3 in food - The impact of eluent additives and labelled internal standards on matrix effects in LC-MS/MS analysis

Deuterated vitamin D standards are used commonly as internal standards in LC-MS/MS analysis of vitamin D3 and 25-hydroxyvitamin D3 in food. However, the use of various eluent additives, such as methylamine, formic acid and ammonium formate, also contributes to matrix effects and the performance of analysis by affecting accuracy and robustness. For the first time, continuous post-column infusion experiments of isotopically labelled vitamin D3-[d6] were performed to evaluate ion-suppression in a wide variety of food (salmon, cheese, pork fat, pork meat, and egg yolk). Furthermore, results collected using five analytical methods, employing DAD/UV and MS/MS-detectors, were evaluated with in-house and standardised reference materials. The matrix effect was significant when analysing vitamin D3 in most food matrices using the deuterium labelled internal standard. Even though the use of the 13C5-labelled internal standard reduced matrix effects, a standardised method is needed to agree on the true value of vitamin D in food.

Differential Thermal Isomerization: Its Role in the Analysis of Vitamin D3 in Foods

Background

For nutritional purposes, the measurement of vitamin D3 (defined as the sum of vitamin D3 and previtamin D3) is required to obtain an accurate and reliable estimate of its content in foods. An often neglected aspect in the development of methods for the analysis of vitamin D3 is accounting for any potential analytical bias in the results associated with differential thermal isomerization between previtamin D and vitamin D.

Conclusions

For LC-UV methods using a vitamin D2 internal standard, cold saponification, or direct lipid extraction techniques should be avoided, unless chromatographic separation of vitamin D2, vitamin D3, and their previtamin forms is achieved so that UV absorbance corrections can be made. For both LC-UV and LC-MS methods using calciferol internal standards, the simplest solution to avoid analytical bias due to the presence of previtamin D is to utilize heating conditions (typically during saponification) such that previtamin D and vitamin D in the sample and the internal standard reach an equivalent equilibrium state prior to instrumental analysis. Only under such circumstances is the integration of previtamin D unnecessary to obtain accurate results for vitamin D3.

Highlights

A detailed discussion of the quantitation of vitamin D3 in food with concise recommendations for avoiding measurement bias as a consequence of differential thermal isomerization.

Association between serum vitamin B6 concentration and risk of osteoporosis in the middle-aged and older people in China: a cross-sectional study

OBJECTIVE

To determine the relationship between serum vitamin B₆ (Vit B₆) concentration and the status of bone mineral density and identify the relationship between serum Vit B6 and bone metabolism parameters in middle-aged and older people in China.

DESIGN

The present study was a cross-sectional study within the framework of an ongoing prospective population-based cohort study.

SETTING AND PARTICIPANTS

A total of 1829 residents (men ≥50 years and women ≥45 years) from two subdistricts were recruited from July 2015 to February 2016 in Shanghai, China.

MEASURES

Recruited residents were grouped (control, osteopenia and osteoporosis) according to their lumbar spine bone mineral density, measured through dual-energy X-ray absorptiometry. Serum Vit B₆ concentrations, bone turnover marker concentrations and calcium and phosphorus metabolism parameters were assessed.

RESULTS

No significant linear trend between serum Vit B₆ concentrations and lumbar bone mass was observed in the men. In the women, the average osteoporosis risk was 61% higher at serum Vit B₆ concentrations of <19.2 μg/L than at those of >26.9 μg/L (OR 1.61, 95% CI 1.00 to 2.58). However, there was no significance after controlling of serum 25-hydroxy-vitamin D concentration and parathyroid hormone concentration, respectively. In the osteoporotic women, the serum Vit B₆ concentration was significantly negatively correlated to concentrations of bone turnover marker including N-terminal propeptide of type I collagen, β-C-terminal telopeptide of type I collagen and osteocalcin. It was also positively related to the serum 25-hydroxy-vitamin D concentration and inversely related to the serum parathyroid hormone concentration.

CONCLUSIONS

A relatively low serum Vit B₆ concentration, even in the normal range, may be a risk factor for osteoporosis in postmenopausal women, which is dependent on serum 25-hydroxy-vitamin D concentration and parathyroid hormone concentration.

TRIAL REGISTRATION NUMBER

NCT02958020; Post-results.

Clinical diagnostic tools for vitamin D assessment

Vitamin D deficiency has been implicated in a plethora of diseases including rheumatoid arthritis, Parkinson's disease, Alzheimer's disease, and osteoporosis. Deficiency of this vitamin is a global epidemic affecting both developing and developed nations. Within a clinical context, the qualitative and quantitative analysis of vitamin D is therefore vital. The main metabolic markers for assessing vitamin D status in humans are the hydroxylated forms of vitamin D, 25OHD₃ and 25OHD₂ on account of their long half-lives within the body and excellent stability. An adequate level for healthy individuals of these hydroxylated forms is estimated to be around 20-40ng/ml of blood. There are three main analytical techniques for determining the levels of 25OHD₃ and 25OHD₂. The first technique is immunoassay-based and can be performed in a rapid, high throughput, automated manner, allowing as many as 240 tests per hour with the duration of each assay as little as 18min. Furthermore, it offers excellent sensitivity with a detection range of 3.4-156ng/ml. A major downside of immunoassays is that they are unable to distinguish between the various forms of vitamin D. While HPLC is a highthroughput low cost instrument it is not a very sensitive technique and cannot quantify the down stream metabolites of vitamin D. The third technique, namely liquid chromatography-mass spectrometry (LC-MS/), provides excellent sensitivity with a wide dynamic range from 0.068pg/ml to 100ng/ml. Additionally, it offers a high level of separation and permits identification of vitamin D-related metabolites. However, a huge limitation with LC/MS/MS is their poor throughput for sample analyses. As yet, there is no analytical technique which combines the fine detection capabilities of LC/MS/MS and the rapid, automated format of immunoassay, for vitamin D analyses. Future attention therefore needs to be given to this area if the current clinical diagnostic tools for vitamin D analysis are to be further improved.

Ultrafast determination of vitamin E using LC–ESI–MS/MS for preclinical development of new nutraceutical formulations

Aim: We proposed a rapid and high quality method to determine α-tocopherol (α-T) in different biopharmaceutical samples using liquid chromatography-diode array detector on-line ESI–MS/MS. Materials & methods: A working standard solution of α-T and internal standard, phenyl-5,7-dimethyl-d6-α-tocopherol, were used for optimization and validation of the method. Levels of α-T in nanoemulsions, serum and plasma samples were evaluated. Results & conclusion: Precision (1% for retention time, 5% for peak area and 3% for relative peak area), linearity range (among 0.625–20.0 μg ml-1), LOD and LOQ, accuracy and matrix effect were studied. The validated chromatographic method is presented as valuable analytical tool for the determination of α-tocopherol in loaded drug delivery systems and in biodistribution levels in blood samples.

Evaluation of Vitamin D3 and D2 Stability in Fortified Flat Bread Samples During Dough Fermentation, Baking and Storage

Purpose: Vitamin D, a fat-soluble secosteroid, has a significant role in bone metabolism and helps calcium absorption in the body. Since vitamin D concentration is altered in fortified foods and dietary supplements, the actual amount of vitamin D may differ from the label value.

Methods: In this study, the concentrations of vitamin D₂ and D₃ of fortified bread sample were analytically determined. For this purpose, dough or homogenized bread sample was saponified using potassium hydroxide solution (30%, w/v) at 80°C, and the saponified analytes were extracted into n-heptane followed by liquid-liquid extraction. Then n-heptane fraction was evaporated to dryness and the sample was reconstituted in methanol. The effect of different parameters was evaluated by one variable at one-time strategy.

Results: The analytes concentrations were evaluated in dough fermentation, baking and storage steps. The effect of temperature in dough fermentation and baking was evaluated at the range of 5-30 and 200-250°C, respectively. Also, the fermentation time was studied in the range of 0-120 min. The analytes concentrations were followed for 1 to 5 days after baking. The results indicated that dough fermentation temperature has no significant effect on the concentration of the analytes. On the other hand, when the dough fermentation time and baking temperature are increased, the analytes concentrations are decreased. Also, the storage duration of the spiked bread samples decreased the analytes concentrations after one day.

Conclusion: Based on the obtained results, baking the dough at high temperatures lead to decrease in vitamin levels.

Review: Determination of Vitamin D in Dairy Products by High Performance Liquid Chromatography

This work reviews the methods used for the determination of vitamin D in some dairy products (milk and infant formulas) by high performance liquid chromatography (HPLC). The low vitamin D contents and the presence of interfering compounds require sample treatment and purification of the extract. The advantages and drawbacks of hot and cold saponification, direct extraction and different types of extract purification are also discussed, taking into account the lack of vitamin D stability by heating, exposure to light and oxidation. With respect to chromatographic determination, the mode (normal or reverse phase), type of column (microcolumn or conventional) and detection system (UV, electrochemical and mass spectrometry) are overviewed, considering the vitamers to be determined.

GC-MS and LC-MS approaches for determination of tocopherols and tocotrienols in biological and food matrices

Tocopherols and tocotrienols, widely described as vitamin E derivatives, have been proven to take part in a number of important biological functions. Among them, antioxidant properties had been investigated and documented in the literature. Since tocochromanols have revealed their plausible beneficial impact on several pathological processes, such as cancerogenesis or cognitive impairment diseases, there is a growing interest in quantitative determination of these compounds in biological fluids, tissues and plant organs. However, due to vitamin E chemical features, such as lipophilic and non-polar characteristics, quantitative determination of the compounds seems to be problematic. In this paper we present current analytical approaches in tocopherols and tocotrienols determination in biological and food matrices with the use of chromatographic techniques, especially gas chromatography (GC) and high performance liquid chromatography (HPLC) coupled with mass spectrometry. Derivatization techniques applied for GC-MS analysis in the case of tocol derivatives, especially silylation and acylation, are described. Significant attention is paid to ionization process of tocopherols and tocotrienols.

Analytical tools for the analysis of β-carotene and its degradation products

β-Carotene, the precursor of vitamin A, possesses pronounced radical scavenging properties. This has centered the attention on β-carotene dietary supplementation in healthcare as well as in the therapy of degenerative disorders and several cancer types. However, two intervention trials with β-carotene have revealed adverse effects on two proband groups, that is, cigarette smokers and asbestos-exposed workers. Beside other causative reasons, the detrimental effects observed have been related to the oxidation products of β-carotene. Their generation originates in the polyene structure of β-carotene that is beneficial for radical scavenging, but is also prone to oxidation. Depending on the dominant degradation mechanism, bond cleavage might occur either randomly or at defined positions of the conjugated electron system, resulting in a diversity of cleavage products (CPs). Due to their instability and hydrophobicity, the handling of standards and real samples containing β-carotene and related CPs requires preventive measures during specimen preparation, analyte extraction, and final analysis, to avoid artificial degradation and to preserve the initial analyte portfolio. This review critically discusses different preparation strategies of standards and treatment solutions, and also addresses their protection from oxidation. Additionally, in vitro oxidation strategies for the generation of oxidative model compounds are surveyed. Extraction methods are discussed for volatile and non-volatile CPs individually. Gas chromatography (GC), (ultra)high performance liquid chromatography (U)HPLC, and capillary electrochromatography (CEC) are reviewed as analytical tools for final analyte analysis. For identity confirmation of analytes, mass spectrometry (MS) is indispensable, and the appropriate ionization principles are comprehensively discussed. The final sections cover analysis of real samples and aspects of quality assurance, namely matrix effects and method validation.

Ozone fumigation increases the abundance of nutrients in Brassica vegetables: broccoli (Brassica oleracea var. italica) and Chinese cabbage (Brassica pekinensis)

Brassicaceae vegetables, among them broccoli and Chinese cabbage, are well recognized due to the nutritional properties. Four-week-old Chinese cabbage and broccoli seedlings were fumigated with O3 for 3 days before being transplanted into the field. The effect of O3 treatment was determined after reaching marketable quality (ca. 10 weeks). The inflorescences of O3-treated broccoli were enriched in vitamin E (α-tocopherol and γ-tocopherol), whereas Chinese cabbage heads had an increased content of anthocyanins and β-carotene. Ozone treatment did not significantly affect the productivity of both examined vegetables.

Mechanism of error caused by isotope-labeled internal standard: accurate method for simultaneous measurement of vitamin D and pre-vitamin D by liquid chromatography/tandem mass spectrometry

RATIONALE

Bias of up to 25% has been observed for vitamin D3 and D2 samples exposed to heating during sample preparation, even when isotope-labeled internal standards are used. The goals of this study were to identify the mechanism of the positive bias observed in measuring vitamin D3 and D2 by liquid chromatography/tandem mass spectrometry (LC/MS/MS) and determine a way to eliminate the error source.

METHODS

Several internal standards with varying locations of labeling were used for comparison in this study. Additionally, different temperatures (25, 37, 55, and 75 °C) and different treatment times were investigated for sample preparation and a LC/MS/MS method capable of simultaneously measuring vitamin D and pre-vitamin D was developed.

RESULTS

It was demonstrated that the different conversion behaviors of the analyte and the internal standard were the cause of the positive bias. This bias was eliminated when internal standards with labeling remote from the double-bond area of the molecules were used. Additionally, sample preparation was shortened from overnight saponification at room temperature to 0.5 h at 75 °C.

CONCLUSIONS

The use of an internal standard with labeling remote from the conjugated area eliminated the error source and gave accurate correction at all of the temperatures investigated. Heating may be used for rapid sample preparation as an alternative to overnight saponification at room temperature. This work not only describes the mechanism of an inaccurate internal standard correction, but also establishes a rapid LC/MS/MS method for simultaneous measurement of vitamin D and pre-vitamin D.

Vitamin D fortification of eggs for human health

BACKGROUND

Vitamin D is an essential component of vertebrate nutrition, and epidemiological surveys confirm a chronic vitamin D insufficiency in the human population. Eggs are one of the few natural sources rich in vitamin D, containing both vitamin D₃ (D₃) and 25-hydroxyvitamin D₃ (25(OH)D₃). 25-Hydroxyvitamin D₃ is especially useful because it provides five times the relative biological activity of vitamin D. In order to establish the potential for enrichment of eggs with D₃ and 25(OH)D₃, a total of 162 hens were fed three levels of D₃ in combination with three levels of 25(OH)D₃. Egg yolks were analysed for their D₃ and 25(OH)D₃ contents, and egg production, egg weights and feed efficiencies were recorded.

RESULTS

The contents of D₃ and 25(OH)D₃ in egg yolk increased significantly with increasing dietary concentrations. There were no significant differences in egg mass, egg weight or feed efficiency. Depending on the dietary concentrations used, it was possible to produce eggs with between 100 and 500 IU vitamin D, providing scope to meet the recommended daily requirement of vitamin D for children or adults.

CONCLUSION

The addition of higher levels of D₃ and 25(OH)D₃ produced eggs with sufficient vitamin D to meet the recommended daily requirements of adults and children without any detrimental effect on production parameters.

Quantification of the level of fat-soluble vitamins in feed based on the novel microemulsion electrokinetic chromatography (MEEKC) method

BACKGROUND

Simultaneous quantification of liposoluble vitamins is not a new area of interest, since these compounds co-determine the nutritional quality of food and feed, a field widely explored in the human and animal diet. However, the development of appropriate methods is still a matter of concern, especially when the vitamin composition is highly complex, as is the case with feed designated for laboratory animals, representing a higher health and microbiological status.

RESULTS

A method combining microemulsion electrokinetic chromatography (MEEKC) with liquid-liquid extraction was developed for the determination of four fat-soluble vitamins in animal feed. A separation medium consisting of 25 mmol L⁻¹ phosphate buffer (pH 2.5), 2-propanol, 1-butanol, sodium dodecyl sulfate and octane allowed the simultaneous determination of vitamins A, D, E and K within a reasonable time of 25 min. The polarity of the separation voltage was reversed in view of the strongly suppressed electro-osmotic flow, and the applied voltage was set at 12 kV. The fat-soluble vitamins were separated in the order of decreasing hydrophobicity.

CONCLUSION

It was proved that the proposed MEEKC method was sufficiently specific and sensitive for screening fat-soluble vitamins in animal feed samples after their sterilization.

Pressurized liquid extraction and dispersive liquid-liquid microextraction for determination of tocopherols and tocotrienols in plant foods by liquid chromatography with fluorescence and atmospheric pressure chemical ionization-mass spectrometry detection

Pressurized liquid extraction (PLE) and dispersive liquid-liquid microextraction (DLLME) were used to isolate and preconcentrate tocopherols and tocotrienols from plant foods. The Taguchi experimental method was used to optimize the six factors (three levels for each factor), affecting DLLME, namely: carbon tetrachloride volume, methanol volume, aqueous sample volume, pH of sample, sodium chloride concentration and time of the centrifugation step. The influencing parameters selected were 2 mL of methanol:isopropanol (1:1) (disperser solvent), 150 µL carbon tetrachloride (extraction solvent) and 10 mL aqueous solution. The organic phase was injected into reversed-phase liquid chromatography (LC) with an isocratic mobile phase composed of an 85:15 (v/v) methanol:water mixture and a pentafluorophenyl stationary phase. Detection was carried out using both fluorescence and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in negative ion mode. Quantification was carried out by the standard addition method. Detection limits were in the range 0.2-0.3 ng mL(-1) for the vitamers with base-line resolution. The recoveries obtained using the optimized DLLME were in the 90-108% range, with RSDs lower than 6.7%. The APCI-MS spectra, in combination with fluorescence spectra, permitted the correct identification of compounds in the vegetable and fruit samples. The method was validated according to international guidelines and using two certified reference materials.

Ozone fumigation results in accelerated growth and persistent changes in the antioxidant system of Brassica oleracea L. var. capitata f. alba

The growth response and antioxidant capacity of Brassica oleracea var. capitata f. alba plants treated with 70ppb of ozone was examined. Four week old cabbage seedlings were fumigated with O3 for 3 days before being transplanted into the growing field. The effect of O3 treatment was determined directly after fumigation and over the course of field cultivation. Plants subjected to O3 treatment had an increased diameter of rosettes and number of leaves after 3 and 7 weeks in agriculture, respectively. In addition, the vast majority of fumigated plants reached marketable quality faster than control plants, indicating a positive role of episodes of increased O3 concentrations during vegetation on growth and yielding. Our analysis revealed that by fumigating juvenile white cabbage plants with moderate doses of O3 the activity of catalases (CAT) and peroxidases was elevated. The activity of the examined enzymes was not affected directly after fumigation, but it increased after several weeks in the experimental field. Increased CAT activity was accompanied by changes in 2 out of the 3 CAT genes CAT1 and CAT2, where CAT2 seemed to be responsible for the induced CAT activity. The biosynthesis of low-molecular stress protectants - tocopherols and the glucosinolate (GLS) sinigrin was transiently affected by ozone. γ-Tocopherol (γ-toc) content significantly increased directly after fumigation, but after 3 weeks of vegetation in the field its concentration reached values similar to control. The biosynthesis of α-tocopherol (α-toc) and sinigrin seemed to be upregulated in fumigated plants. However, the response was delayed; no differences were registered directly after treatment, but 3 weeks after transplanting the concentration of sinigrin and α-toc was elevated.

Comprehensive profiling of carotenoids and fat-soluble vitamins in milk from different animal species by LC-DAD-MS/MS hyphenation

This paper describes a novel and efficient analytical method to define the profile of fat-soluble micronutrients in milk from different animal species. Overnight cold saponification was optimized as a simultaneous extraction procedure. Analytes were separated by nonaqueous reversed-phase (NARP) chromatography: carotenoids on a C(30) column and fat-soluble vitamins on a tandem C(18) column system. Besides 12 target analytes for which standards are available (all-trans-lutein, all-trans-zeaxanthin, all-trans-β-cryptoxanthin, all-trans-β-carotene, all-trans-retinol, α-tocopherol, γ-tocopherol, δ-tocopherol, ergocalciferol, cholecalciferol, phylloquinone, and menaquinone-4), the DAD-MS combined detection allowed the provisional identification of other carotenoids on the basis of the expected retention times, the absorbance spectra, and the mass spectrometric data. Retinol and α-tocopherol were the most abundant fat-soluble micronutrients and the only ones found in donkey's milk along with γ-tocopherol. Ewe's milk also proved to be a good source of vitamin K vitamers. Bovine milk showed a large variety of carotenoids that were absent in milk samples from other species with the only exception of all-trans-lutein and all-trans-zeaxanthin.

Vitamin D and 25-hydroxyvitamin D determination in meats by LC-IT-MS

This paper reports a method for the rapid, sensitive and simultaneous analysis of vitamin D (Vit D) and 25-hydroxyvitamin D (25OH-Vit D) in meats. Samples were saponified and underwent solid phase extraction with analysis by normal phase liquid chromatography (LC) with ion trap mass spectroscopy (IT-MS), using positive polarity atmospheric pressure chemical ionisation (APCI). Limits of detection (LOD) and quantification (LOQ) for Vit D and 25OH-Vit D were 0.03 and 0.05 μg/100g respectively. Deuterium labelled Vit D and 25OH-Vit D internal standards were added as surrogates prior to saponification, correcting for extraction inefficiencies and potential MS matrix enhancement or suppression effects. Recoveries using internal/surrogate standard correction ranged from 80% to 100% for all vitamers. Measurement uncertainty ranged from 6% to 15% for all vitamers in this method. This process required only 7.5 g of sample per extraction and a batch of 28 extractions could be completed in six hours.

Method for simultaneous analysis of eight vitamin E isomers in various foods by high performance liquid chromatography and fluorescence detection

The objective of this study was to optimize a method to investigate the occurrence and to quantify the full isomeric composition of vitamin E (α-, β-, γ- and δ-tocopherols and tocotrienols) in 6 vegetables (raw and cooked), 3 herbs/spices, raw and cooked eggs, vegetable oils (canola, olive and soybean), flaxseed and sorghum (flour and seeds) and soy (flour) by HPLC with fluorescence detection. Different conditions of extraction and analysis were tested. The optimized method consisted of direct extraction with solvent (hexane:ethyl acetate, 85:15, v/v). For analysis normal phase column was used with mobile phase consisting of hexane:isopropanol:acetic acid (98.9:0.6:0.5) with isocratic elution and fluorescence detection. Excellent separation of all isomers was obtained along with adequate quantification in the foods analyzed. Recovery rates of standards ranged from 91.3 to 99.4%. The linearity range for each isomer varied from 2.5 to 137.5 ng/mL (R² greater than 0.995 in all cases). Detection limits ranged from 21.0 to 48.0 ng/mL for tocopherols and from 56.0 to 67.0 ng/mL for tocotrienols, while quantification limits ranged from 105.0 to 240.0 ng/mL for tocopherols and from 280.0 to 335.0 ng/mL for tocotrienols. The optimized method was considered simple, fast and reliable, and also preserved vitamin E isomers when compared to validated methods involving saponification.

Vitamin D3 quantification in a cod liver oil-based supplement

A reliable, accurate and reproducible method to quantify vitamin D3 (Vit. D3) in oily dietary supplements was developed after three Vit. D3 intoxications were diagnosed as reasonably resulting from a dietary administration of a cod liver oil based supplement. Liquid chromatography coupled to mass spectrometry operating in atmospheric pressure chemical ionization conditions (LC-APCI) and by using a deuterium labelled internal standard resulted to be an effective technique to reach the analytical aim. Due to the complexity of the oily matrix, the new analytical approach required a solid phase extraction step prior to analysis. The amount of Vit. D3 declared on the label of the cod liver oil based supplement for each soft capsule is 1.5μg. Consequently, the method was developed to quantify Vit. D3 amounts in the range 1-5μg/mL. To improve reliability of obtained data, both MS and MS/MS acquisition methods were employed. The method was evaluated by measuring the characteristic parameters such as linearity, precision, accuracy and robustness and cross checked against a certified pharmaceutical preparation. The LC-APCI-MS and MS/MS methods were applied in order to assess the Vit. D3 content in the dietary supplements taken by the intoxicated patients, found about three order of magnitude higher than that declared. The Vit. D3 content of other batches of the same commercial product was found as declared.