Food analysis: A continuous challenge for miniaturized separation techniques

Nano liquid chromatography, an updated review

Low flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for mass spectrometry have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow liquid chromatography , the types of columns employed, and strategies for multi-dimensionality of separations, which is key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend towards biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy to use platform.

Image learning to accurately identify complex mixture components

The study of complex mixtures is very important for exploring the evolution of natural phenomena, but the complexity of the mixtures greatly increases the difficulty of material information extraction. Image perception-based machine-learning techniques have the ability to cope with this problem in a data-driven way. Herein, we report a 2D-spectral imaging method to collect matter information from mixture components, and the obtained feature images can be easily provided to deep convolutional neural networks (CNNs) for establishing a spectral network. The results demonstrated that a single CNN trained end-to-end from the proposed images can directly accomplish synchronous measurement of multi-component samples using only raw pixels as inputs. Our strategy has some innate advantages, such as fast data acquisition, low cost, and simple chemical treatment, suggesting that it can be extensively applied in many fields, including environmental science, biology, medicine, and chemistry.

Ultrasensitive determination of serotonin in human urine by a two dimensional capillary isotachophoresis-capillary zone electrophoresis hyphenated with tandem mass spectrometry

A two-dimensional capillary isotachophoresis-capillary zone electrophoresis method hyphenated with tandem mass spectrometry was developed and validated for ultrasensitive quantification of serotonin in real human urine samples. Under optimal conditions, the separation was achieved within 12 min (including on-line sample preparation) with the limit of detection of 34 pg mL^-1 (due to a large volume sample injection, here 10 µL, and isotachophoretic preconcentration). This concentration limit represents the lowest value for serotonin in comparison to other previously published separation methods employing mass spectrometry detection and applied to urine matrices. Thanks to high orthogonality, on-line concentration and clean-up effects of this approach, other excellent validation parameters such as linearity (coefficient of determination > 0.99), inter-day and intra-day precision (relative standard deviations 3.5-12.2%), accuracy (relative errors within 99-109.4%), and recovery (96-102%) could be easily obtained too. To demonstrate applicability of the method, we monitored serotonin levels in various real samples (from a healthy volunteer and clinical ones). The determined levels, normalized on the creatinine concentrations, were in the range of 6.81-12.86 ng mmol^-1 creatinine This advanced method is suggested for an effective, reliable, high sample throughput, and low cost routine clinical screening or targeted metabolomic studies of serotonin in urine samples.

Personalized Nutrition and -Omics

With change in global concern toward food quality over food quantity, consumer concern and choice of healthy food has become a matter of prime importance. It gave rise to concept of “personalized or precision nutrition”. The theory behind personalization of nutrition is supported by multiple factors including advances in food analytics, nutrition based diseases and public health programs, increasing use of information technology in nutrition science, concept of gene-diet interaction and growing consumer capacity or concern by better and healthy foods. The advances in “omics” tools and related analytical techniques have resulted into tremendous scope of their application in nutrition science. As a consequence, a better understanding of underlying interaction between diet and individual is expected with addressing of key challenges for successful implementation of this science. In this chapter, the above aspects are discussed to get an insight into driving factors for increasing concern in personalized nutrition.

Novel strategy for food safety risk management and communication: Risk identification for benzoic acid residues in pickled vegetables

Benzoic acid (BA) is widely used as an antimicrobial preservative to prolong the shelf-life of pickled vegetables. A method for rapidly determining the BA content in forty pickled vegetable samples was developed by coupling ultrasonic extraction with surface-enhanced Raman scattering (SERS) and an adaptive iteratively reweighted penalized least-squares (AirPLS) algorithm. The results obtained with this method were compared and correlated with those from high-performance liquid chromatography measurements. Amplification of the Raman scattering via the SERS effect was induced by gold nanoparticles (AuNPs) when BA was irradiated with a 785 nm laser. The AirPLS algorithm was used to reduce the background interference signal, which was also amplified. The amplified Raman scattering effect of BA in the pickled vegetables displayed a positive and significant correlation with the HPLC concentration of BA, with high reproducibility. For HPLC determination of the concentration of BA in the range of 0-820 ppm, the BA monomer's intensity of the 944-1,005 cm-1 and 1,366-1,373 cm-1 peaks, and BA dimer's intensity of the 1,025 cm-1 and 1,465-1,482 cm-1 peaks in the SERS spectrum were respectively converted to the Z-ratio BA monomer and Z-ratio BA dimer standard scores by Z-Score conversion. The sum's (Z-ratio BA monomer + Z-ratio BA dimer) sensitivity was 100%, and specificity was 90.9% by receiver operating characteristic curve. This study found that a Raman spectroscopy-based monitoring method can be one of the fastest screening inspection options that can complete an analysis within a short period of time and produce reliable results. This approach is particularly cost-effective, which makes it suitable for the initial screening of raw materials and provides an effective management strategy easy to communicate with food safety officials.

Miniaturized liquid chromatography applied to the analysis of residues and contaminants in food: A review

The humankind is pretty dependent on food to control several biological processes into the organism. As the world population increases, the demand for foodstuffs follows the same trend claiming for a high food production situation. For this reason, a substantial amount of chemicals is used in agriculture and livestock husbandries every year, enhancing the likelihood of contaminated foodstuffs being commercialized. This outlook becomes a public health concern; thus, the governmental regulatory agencies impose laws to control the residues and contaminants in food matrices. Currently, one of the most important analytical techniques to perform it is LC. Despite its already recognized effectiveness, it is often time consuming and requires significant volumes of reagents, which are transformed into toxic waste. In this context, miniaturized LC modes emerge as a greener and more effective analytical technique. They have remarkable advantages, including higher sensitivity, lower sample amount, solvent and stationary phase requirements, and more natural coupling to MS. In this review, most of the critical characteristics of them are discussed, focusing on the benchtop instruments and their related analytical columns. Additionally, a discussion regarding the last 10 years of publications reporting miniaturized LC application for the analysis of natural and industrial food samples is categorized. The main chemical classes as applied in the crops are highlighted, including pesticides, veterinary drugs, and mycotoxins.

Rapid determination of nucleotides in infant formula by means of nano-liquid chromatography

A rapid method for the quantification of five ribonucleotides 5'- monophophates (adenosine, cytidine, guanosine, inosine, uridine, 5'-monophosphate), in infant formula, has been proposed using nano-LC. To separate the studied compounds, capillary columns packed with different C18-based stationary phases were investigated. All the columns tested were laboratory prepared. The experiments were performed in ion-pairing RP chromatographic mode using tetrabutylammonium hydroxide as ion-pairing reagent. The method was developed using a core-shell XB-C18 capillary column with a mobile phase consisting of 5% v/v methanol and 95% v/v 100 mM ammonium formate, pH 8, containing 20 mM tetrabutylammonium hydroxide. All compounds were baseline resolved in less than 5 min with a flow rate of 500 nL/min in isocratic elution mode. Nucleotides were detected at 260 nm. Analytical validation parameters were evaluated. The RSD values for intraday and interday repeatability for retention time and peak area were <2.4 and 4.2%, respectively. The method linearity was good (R(2) < 0.9995) for the studied compounds. LOD and limit of quantitation were 0.25 and 0.50 μg/mL, respectively. The method was applied to the determination of nucleotides in infant formula, subjected to a centrifugal ultrafiltration process, prior their analysis. The amounts found were in agreement to the labeled contents.

Combining selection valve and mixing chamber for nanoflow gradient generation: Toward developing a liquid chromatography cartridge coupled with mass spectrometer for protein and peptide analysis

Toward developing a micro HPLC cartridge, we have recently built a high-pressure electroosmotic pump (EOP). However, we do not recommend people to use this pump to deliver an organic solvent directly, because it often makes the pump rate unstable. We have experimented several approaches to address this issue, but none of them are satisfactory. Here, we develop an innovative approach to address this issue. We first create an abruption (a dead-volume) within a fluid conduit. We then utilize an EOP to withdraw, via a selection valve, a train of eluent solutions having decreasing eluting power into the fluid conduit. When these solutions are further aspirated through the dead-volume, these solutions are partially mixed, smoothening concentration transitions between two adjacent eluent solutions. As these solutions are pushed back, through the dead-volume again, a smooth gradient profile is formed. In this work, we characterize this scheme for gradient formation, and we incorporate this approach with a high-pressure EOP, a nanoliter injection valve, and a capillary column, yielding a micro HPLC system. We then couple this micro HPLC with an electrospray ionization - mass spectrometer for peptide and protein separations and identifications.

New analytical strategies applied to the determination of Coenzyme Q10 in biological matrix

In the last few years the importance of Coenzyme Q10 (CoQ10) determination has gained clinical relevance. CoQ10 is a redox-active, lipophilic substance integrated in the mitochondrial respiratory chain which acts as an electron carrier for the production of cellular energy. In addition, it is recognized as a primary regenerating antioxidant playing an intrinsic role against oxidative damage. There are some reports of low CoQ10 levels in a number of disorders, such as cancer, muscular, neurodegenerative, cardiological, and reproductive diseases. Therefore, it is a priority to develop analytical methodologies for evaluating CoQ10 in matrices of greater importance for the correct diagnosis of diseases, simple enough to be used in routine clinical laboratories. In this chapter two recently developed techniques, capillary electrophoresis and microHPLC, for the analysis of CoQ10 in biological matrices, are studied.

Chiral capillary electromigration techniques-mass spectrometry-hope and promise

Analytical methods for chiral compounds require a separation step prior to mass spectrometric detection. CE can separate enantiomers by the use of a chiral selector and can be hyphenated with MS. The chiral selector can be either embedded inside the capillary (electrochromatography) or added into the background solution (EKC). This review describes the fundamentals and highlights the recent developments (September 2009-May 2013) of chiral CEC and EKC with detection using MS. There were 20 research and more than 30 review papers during this period. The research efforts were driven by fundamental studies, such as the development of novel chiral selectors in electrochromatography and of advanced partial filling techniques in EKC in order to optimise separation. Other developments were in application studies, such as in food analytics and metabolomics.

Biomarker discovery and applications for foods and beverages: proteomics to nanoproteomics

Foods and beverages have been at the heart of our society for centuries, sustaining humankind - health, life, and the pleasures that go with it. The more we grow and develop as a civilization, the more we feel the need to know about the food we eat and beverages we drink. Moreover, with an ever increasing demand for food due to the growing human population food security remains a major concern. Food safety is another growing concern as the consumers prefer varied foods and beverages that are not only traded nationally but also globally. The 21st century science and technology is at a new high, especially in the field of biological sciences. The availability of genome sequences and associated high-throughput sensitive technologies means that foods are being analyzed at various levels. For example and in particular, high-throughput omics approaches are being applied to develop suitable biomarkers for foods and beverages and their applications in addressing quality, technology, authenticity, and safety issues. Proteomics are one of those technologies that are increasingly being utilized to profile expressed proteins in different foods and beverages. Acquired knowledge and protein information have now been translated to address safety of foods and beverages. Very recently, the power of proteomic technology has been integrated with another highly sensitive and miniaturized technology called nanotechnology, yielding a new term nanoproteomics. Nanoproteomics offer a real-time multiplexed analysis performed in a miniaturized assay, with low-sample consumption and high sensitivity. To name a few, nanomaterials - quantum dots, gold nanoparticles, carbon nanotubes, and nanowires - have demonstrated potential to overcome the challenges of sensitivity faced by proteomics for biomarker detection, discovery, and application. In this review, we will discuss the importance of biomarker discovery and applications for foods and beverages, the contribution of proteomic technology in this process, and a shift towards nanoproteomics to suitably address associated issues. This article is part of a Special Issue entitled: Translational plant proteomics.

NutriChip: nutrition analysis meets microfluidics

This focus article introduces the concept of NutriChip, an integrated microfluidic platform for investigating the potential of the immuno-modulatory function of dairy food. The core component of the NutriChip is a miniaturized artificial human gastrointestinal tract (GIT), which consists of a confluent layer of epithelial cells separated from a co-culture of immune cells by a permeable membrane. This setting creates conditions mimicking the human GIT and allows studying processes that characterize the passage of nutrients though the human GIT, including the activation of immune cells in response to the transfer of nutrients across the epithelial layer. The NutriChip project started by developing a biologically active in vitro cellular system in a commercial Transwell co-culture system. This Transwell system serves as a reference for the micro-scale device which is being developed. The microfluidic setup of NutriChip allows monitoring of the response of immune cells to pro-inflammatory stimuli, such as lipid polysaccharide (LPS), and to the application of potentially anti-inflammatory dairy food. This differential response will be quantified by measuring the variation in expression of pro-inflammatory cytokines, including interleukin 1 (IL-1) and interleukin 6 (IL-6), secreted by the immune cells, and this is achieved by using a dedicated optical imager. A series of dairy products will be screened for their anti-inflammatory properties using the NutriChip system and, finally, the outcome of the NutriChip will be validated by a human nutrition trial. Therefore, the NutriChip platform offers a new option to evaluate the influence of food quality on health, by monitoring the expression of relevant immune cell biomarkers.

Food Analysis: Present, Future, and Foodomics

This paper presents a revision on the instrumental analytical techniques and methods used in food analysis together with their main applications in food science research. The present paper includes a brief historical perspective on food analysis, together with a deep revision on the current state of the art of modern analytical instruments, methodologies, and applications in food analysis with a special emphasis on the works published on this topic in the last three years (2009–2011). The article also discusses the present and future challenges in food analysis, the application of “omics” in food analysis (including epigenomics, genomics, transcriptomics, proteomics, and metabolomics), and provides an overview on the new discipline of Foodomics.

Thirty years of capillary electrophoresis in food analysis laboratories: potential applications

CE has generated considerable interest in the research community since instruments were introduced by different trading companies in the 1990s. Nowadays, CE is popular due to its simplicity, speed, highly efficient separations and minimal solvent and reagent consumption; it can also be included as a useful technique in the nanotechnology field and it covers a wide range of specific applications in different fields (chemical, pharmaceutical, genetic, clinical, food and environmental). CE has been very well evaluated in research laboratories for several years, and different new approaches to improve sensitivity (one of the main drawbacks of CE) and robustness have been proposed. However, this technique is still not well accepted in routine laboratories for food analysis. Researching in data bases, it is easy to find several electrophoretic methods to determine different groups of analytes and sometimes they are compared in terms of sensitivity, selectivity, precision and applicability with other separation techniques. Although these papers frequently prove the potential of this methodology in spiked samples, it is not common to find a discussion of the well-known complexity of the matrices to extract analytes from the sample and/or to study the interferences in the target analytes. Summarizing, the majority of CE scientific papers focus primarily on the effects upon the separation of the analytes while ignoring their behavior if these analytes are presented in real samples.

Determination of trigonelline in seeds and vegetable oils by capillary electrophoresis as a novel marker for the detection of adulterations in olive oils

A capillary electrophoresis method with UV detection was developed for the first time for the determination of the pyridine betaine trigonelline (N-methylnicotinic acid) in seeds and vegetable oils. Analytical characteristics of the method showed its good performance in terms of linearity (r > 0.999), precision (relative standard deviations < 5%), and limits of detection (up to 0.9 microM or 1 ng/g for oils). The developed method was applied to the analysis of soy and sunflower seeds, three varieties of olives, and sunflower, soy, and extra virgin olive oils. Trigonelline was determined in soy and sunflower seeds and their respective oils, whereas it was not detected in olives or olive oils. Different mixtures of extra virgin olive oil with seed oils were analyzed, detecting up to 10% of soy oil in olive oil. As a consequence, trigonelline is proposed in this work as a novel marker for the detection of adulterations of olive oils with other vegetable oils such as soy and sunflower oils.