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Using LC-LTQ-Orbitrap MS we were able to identify 10 major phosphatidylinositol (PI) species present in 32 infant formulas (IF) collected from Australia, Europe and the USA. Based on the species fingerprint, the 32 formulas can be classified into several distinct groups by PCA analysis; this grouping pattern reflects origin and the label information of the formulas. The total content of all PI species was determined by LC-Triple Quadrupole MS in negative MRM mode using external standard calibration. The content of PI showed large variation between formulas and was very high in certain cases, which is believed to be related to the use of soybean lecithin in these products. Our study indicates that the content and speciation of PIs have significant contribution to the total amount of inositol in all 32 products surveyed; this contribution may be important for the fine nutritional profile and biological functions of IF products., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

For LC-MS-based lipidomic analysis of milk, total lipid extraction from raw milk is generally conducted with Folch or Bligh and Dyer methods; both methods are based on two-phase partition of lipids, and thus time-consuming. In this work, three solvent systems for one-phase extraction of milk lipids were compared with the standard Folch method. Two of the solvent systems (butanol/methanol, 3:1 and 1:1) previously tested for lipid extraction from plasma were found to provide adequate extraction for polar lipids, but incomplete extraction for triglycerides, especially highly lipophilic species. By contrast, our newly designed solvent mix composed of butanol, methanol and chloroform (at a 3:5:4 ratio) provided similar extraction efficiency for triglycerides and higher yield for some of the phospholipids, as compared to the Folch method. This new one-phase extraction method is very simple yet comprehensive and thus suitable for high throughput lipid analysis of milk samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Polar lipids (PLs) are a significant functional component of milk that are difficult to quantitate. A simple method for comprehensive identification and quantitative analysis of all essential PL species using bovine milk is described. The lipid fraction was extracted by a mix of chloroform and methanol and the extract was directly used for PL identification and quantification. PLs were separated by hydrophilic interaction liquid chromatography (HILIC) and detected by an Orbitrap mass analyser in positive mode. The structure of PLs was established or confirmed by tandem MS in both positive and negative modes. The method is sensitive (with a LOD for all PL classes ≤0.1 ng) and reproducible, enabling simultaneous quantification of 70 PL species within a run of 45 min. Application of this method to the quantification of PLs in 32 bovine milk samples revealed the relative abundance of different PL classes, significant variation of PL content between individual samples and the correlation between the major PL classes. The method provides a tool for investigating the variation and metabolism of important PL components in bovine and human milk and in diverse mammalian species., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Free oligosaccharides (OS) are a significant functional component of milk that are difficult to quantitate. A simple method for quantitative analysis of the major free OS in bovine milk is described. Following a defatting step, protein elimination was performed by ultrafiltration. OS were separated by hydrophilic interaction liquid chromatography (HILIC) and detected by an Orbitrap mass analyzer in negative mode. The method is sensitive [with a limit of detection (LOD) for all representative OS of <0.1 ng] and reproducible, enabling simultaneous quantification of 13 major OS within a single run. Application of this method to the quantification of major OS in 32 milk samples collected after three different feeding treatments allowed us to reveal the relative abundance of different OS species, the variation of the OS content between individual cows, and the correlations between some of the major OS.

Metabolite analysis or metabolomics is an important component of systems biology in the post-genomic era. Although separate liquid chromatography (LC) methods for quantification of the major classes of polar metabolites of plants have been available for decades, a single method that enables simultaneous determination of hundreds of polar metabolites is possible only with gas chromatography–mass spectrometry (GC–MS) techniques. The rapid expansion of new LC stationary phases in the market and the ready access of mass spectrometry in many laboratories provides an excellent opportunity for developing LC–MS based methods for multi-target quantification of polar metabolites. Although various LC–MS methods have been developed over the last 10 years with the aim to quantify one or more classes of polar compounds in different matrices, currently there is no consensus LC–MS method that is widely used in plant metabolomics studies. The most promising methods applicable to plant metabolite analysis will be reviewed in this paper and the major problems encountered highlighted. The aim of this review is to provide plant scientists, with limited to moderate experience in analytical chemistry, with up-to-date and simplified information regarding the current status of polar metabolite analysis using LC–MS techniques.

Current liquid chromatography (LC) based methods for the analysis of polar plant metabolites require multiple runs using complex mobile phases and a combination of different columns. Here we describe a fast liquid chromatography-mass spectrometry (LC-MS) method for the determination of major polar metabolites in plants that requires only a single run using a single column. The method takes advantage of the ability to acquire both positive and negative data in an ion trap mass spectrometer (MS) and also the accurate mass capability of the orbitrap MS. The separation of polar compounds is achieved with a polar, reversed-phase column (Synergi Hydro-RP). A single analysis with a 25min runtime is able to reliably determine the level of nearly all essential amino acids, several major organic acids and several major sugars in plant materials, as exemplified by analysis of a perennial ryegrass extract. The level of detection on column was below 0.1ng (average 0.03ng) for most amino acids, below 5ng (average 2.3ng) for organics acids and below 1ng (average 0.64ng) for sugars. The levels of quantified metabolites in ryegrass varied from 22μg/g dry weight for histidine to 41mg/g dry weight for sucrose., (Copyright © 2012. Published by Elsevier B.V.)

Bovine milk contains 3–5% of fat, of which the dominant portion (about 98%) is in the form of triacylglycerols, whereas polar lipids such as glycerophospholipids and sphingolipids are minor components (0.5–1%) of milk fat. Milk fat is thought to contain several thousand lipid species, making it the most complex material in nature in terms of lipid composition. Significant progress has been made in the past two decades in the identification and quantification of lipid species of milk thanks to the advance in analytical tools especially high-resolution mass spectrometers (MS). Currently, milk lipids are characterized mainly in two ways, i.e. global fatty acid composition profiling by gas chromatography and lipid molecular species identification and quantification by liquid chromatography tandem MS; the former provides information related to the physicochemical properties and nutritive quality of milk fat, whereas the latter provides the detailed chemical structure of lipid species. Until now, only about 400 lipid species have been described in bovine milk, with many low-abundance species remaining to be discovered. The merits and limitations of various separation techniques and different MS methodologies applied to lipid structural elucidation and quantification are critically reviewed and the challenging problems to be solved in milk lipidomic analysis highlighted. [ABSTRACT FROM AUTHOR]

Volatile phenols (VPs) derived from smoke-exposed grapes are known to confer a smoky flavor to wine. Current methods for determination of VPs in grape berries either involve complex sample purification/derivatization steps or employ two analytical platforms for free and bound VP fractions. We report here a simple gas chromatography-tandem mass spectrometry (GC-MS/MS) method for quantification of both free and bound VPs in grapes, based on optimized (1) GC-MS/MS parameters, (2) an analyte extraction procedure, and (3) phenol glycoside hydrolysis conditions. Requiring neither sample cleanup nor a derivatization step, this method is sensitive (LOD ≤ 1 ng/g berries) and reproducible (RSD < 12% for repeated analyses) and is expected to significantly reduce the sample turnover time for smoke taint detection in vineyards. [ABSTRACT FROM AUTHOR]