Rocío Barreiro

Application of molecularly imprinted polymers in food analysis: clean-up and chromatographic improvements

AbstractSeveral natural and synthetic substances have been monitored in analytical laboratories worldwide to ensure food safety. Multiple residue detection (i.e., detection of multiple analytes in a single sample or matrix) is a main weakness of existing analytical methods, when fast and reliable results are required. Multianalyte approaches may save time and money in the food industry, and more importantly, they allow the quick release of food products into the marketplace. In addition, multianalyte approaches notably decrease the time required between sampling and analysis to meet legal requirements.However, to achieve analytical success, it is necessary to develop thorough clean-up procedures to extract analytes from the matrix. In addition, good chromatographic separation methods are also necessary to distinguish closely related analytes. Molecular imprinting technology (MIT) is an emerging, powerful tool for sample extraction and chromatography. First used for solid-phase extraction, molecularly imprinted polymers (MIPs) are also effective chromatographic phases for the separation of isomers and structurally related molecules. In recent years, a number of analytical methods utilising MIT have been applied for the analysis of residues in food, and existing methodologies have been improved. This review article describes the latest applications of MIT in the development of methodologies to monitor the presence of residues of veterinary products in foodstuff.

Fast HPLC-MS/MS Method for Determining Penicillin Antibiotics in Infant Formulas Using Molecularly Imprinted Solid-Phase Extraction

The dairy cattle may suffer from different infections relatively often, but the inflammation of the mammary gland is very important to the farmer. These infections are frequently treated with penicillin antimicrobial drugs. However, their use may result in the presence of residues in animal products, such as milk powder and/or infant formulas, and it represents a potential risk for consumers. To monitor this, the EU has defined safe maximum residue limits (MRLs) through Commission Regulation (EU) number 37/2010. Although LC-MS is a trustful option for confirmation and quantification of antibiotics, the analysis of real samples with complex matrices frequently implies previous clean-up steps. In this work, precipitation polymerization has been used and different molecularly imprinted polymer (MIP) sorbents were tested and optimized for the fast and simultaneous solid-phase extraction (MISPE) of eight common penicillins (ampicillin, amoxicillin, oxacillin, penicillin G, penicillin V, cloxacillin, dicloxacillin, and nafcillin). The extracts were analyzed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and the applicability of these polymers as sorbents for the extraction of penicillins at MRL levels in milk powder (infant formulas) was proved. The limits of detection and quantification were below the legal tolerances, except for LOQ for oxacillin and cloxacillin.

Evaluation of Molecularly Imprinted Polymers for the Simultaneous SPE of Six Corticosteroids in Milk

A molecularly imprinted solid-phase extraction procedure was optimized for the simultaneous extraction of six corticosteroids commonly employed in animal husbandry. Two different molecularly imprinted polymers (MIPs) were synthetized by precipitation polymerization, using dexamethasone (DM) and flumethasone (FLU) as template molecules. Methacrylic acid was used as functional monomer and divinylbenzene as cross-linker, and the selected porogen was a solution of acetonitrile and toluene (3:1). After removal of the template, both molecularly imprinted and non-imprinted polymers were placed into glass cartridges to perform solid-phase extraction experiments. Loading, washing and elution steps were optimized for each MIP in order to test the suitability of the selected template molecules DM and FLU to provide selective polymeric sites for corticosteroids. Recovery measurements were performed by HPLC–MS/MS. The maximum recovery for all corticosteroids was achieved with DM-based MIP when loading with toluene and washing with 5% acetonitrile in toluene, and eluting with 1% acetic acid in methanol. When cleaning-up milk samples spiked with corticosteroids, the recovery of DM-based polymer decreased. However, the efficiency of FLU-based polymer clearly improved even when a strong matrix effect was observed. Additionally, two frequently used commercial solid-phase extraction (SPE) cartridges were compared with imprinted polymers. The commercial SPE cartridges gave good recoveries only for specific analytes while MIPs provided good recoveries for all analyzed corticosteroids.

Development of a HPLC-MS/MS confirmatory method for the simultaneous determination of amphenicols in baby formulas using molecularly imprinted polymers

Chloramphenicol (CAP) is a broad-spectrum bacteriostatic antibiotic commonly used in veterinary medicine. However, toxic effects in humans such as Grey syndrome, bone marrow suppression, and fatal aplastic anaemia have been described. As a consequence, the use of CAP in foodstuffs has been banned within the European Union since 1994 and no maximum residue limit (MRL) has been established in animal-derived foods. On the other hand, thiamphenicol (TAP) and florfenicol (FLP) are allowed but different MRLs have been set in foodstuffs of animal origin. In this work, precipitation polymerisation has been used and different MIP sorbents were tested and optimized for the solid-phase extraction (MISPE) of a group of three, structurally related amphenicols in milk powder. Recoveries were calculated using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) working in negative mode. The proposed confirmatory method was validated according to the Commission Decision 2002/657/EC, resulting in CCα ranging from 0.06 to 10.5 ng mL−1 and reaching the required working levels. The applicability of these polymers for the extraction of amphenicols in spiked samples of baby formulas has been tested.

An analysis on how switching to a more balanced and naturally improved milk would affect consumer health and the environment

This study compares a premium brand of UHT milk, Unicla, characterised by an improved nutritional composition, to conventional milk, in terms of health effects and environmental impacts. Unlike enriched milks, in which nutrients are added to the final product, Unicla is obtained naturally by improving the diet of the dairy cows. Health effects have been analysed based on literature findings, while the environmental analysis focused on those spheres of the environment where milk is expected to cause the higher impacts, and thus carbon (CF) and water footprints (WF) have been determined. Five final products have been compared: 3 conventional (skimmed, semi-skimmed, whole) and 2 Unicla (skimmed, semi-skimmed) milks. As a functional unit, one litre of packaged UHT milk entering the regional distribution centre has been chosen. The improved composition of Unicla milk is expected to decrease the risk of cardiovascular disease and to protect consumers against oxidative damage, among other health benefits. Concerning the environmental aspect, CF of Unicla products are, on average, 10% lower than their conventional equivalents, mainly due to the lower enteric emissions of caused by the Unicla diet. No significant differences were found between the WF of Unicla and conventional milk. Raw milk is the main contributor to both footprints (on average, 83.2 and 84.3% of the total CF of Unicla and conventional milk, respectively, and 99.9% of WF). The results have been compared to those found in literature, and a sensitivity analysis has been performed to verify their robustness. The study concludes that switching to healthier milk compositions can help slowing down global warming, without contributing to other environmental issues such as water scarcity. The results should encourage other milk companies to commit to the development of healthier, less environmentally damaging products, and also to stimulate consumers to bet on them.

A facile method for the fabrication of magnetic molecularly imprinted stir-bars: A practical example with aflatoxins in baby foods.

A fast and facile method for the fabrication of magnetic molecularly imprinted stir-bars (MMIP-SB) has been developed, using a combination of imprinting technology and magnetite. Magnetite was prepared in the laboratory from the raw and embedded into molecularly imprinted polymers through a process of bulk polymerization. This novel design was applied to the analysis of aflatoxins, one of the most important groups of mycotoxins in terms of occurrence and toxicity. In the context of food safety, molecularly imprinted polymers are a promising tool to achieve selective and accessible methods of extraction for different residues and contaminants. Considering the toxicity of aflatoxins, a dummy template was preferred for the synthesis of the imprinted polymers. A rapid and affordable extraction method for isolating five different aflatoxins that may be present in food was developed. The MMIP-SB was used as a conventional stir-bar and combined with high performance liquid chromatography and mass spectrometry for the determination of aflatoxin M1 in milk powder (infant formulas) and aflatoxins B1, B2, G1 and G2 in cereal-based baby foods. The results showed an average recovery of 60%, 43, 40, 44 and 39%, respectively, and RSD below 10%. These in-house prepared stir-bars featured good stirring and extraction performance, and recognition abilities, offering a good alternative to more complicated.

Analysis of Naturally Occurring Steroid Hormones in Infant Formulas by HPLC-MS/MS and Contribution to Dietary Intake

Milk is a natural fluid and as such contains small amounts of naturally occurring steroids. Human milk is recommended as the optimal source of nutrients for infants and young children, and it has been associated to several short- and long-term benefits. For this reason, its composition is used as a reference for designing infant formulas. However, the available information on the hormonal levels of these dairy products is scarce, and it is usually limited to estradiol and estrone. In the present study, six natural sex hormones (pregnenolone, progesterone, estrone, dehydroepiandrosterone, testosterone and androstenedione) have been extracted from sixteen milk-based infant formulas and analyzed with liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The purpose of this research was to quantify natural steroid hormones in various infant formulas, to provide food and nutrition practitioners with information to estimate intakes in children. In addition, data found in the literature was used for comparison. The findings suggest that there are certain similarities between bovine milk and dairy products for infants. Furthermore, the detected levels were in general lower than those observed in human milk and/or colostrum. The reported results represent a valuable addition to the current knowledge on natural hormone content of infant foods.

Confirmation of β-agonist residues in bovine retina and liver using HPLC-MS/MS and evaluation of matrix-dependent problems

ABSTRACT β-Agonists or β-adrenergic agonists are synthetic drugs sometimes used for therapeutic purposes in veterinary medicine. However, these compounds also belong to a class of illegal growth promoters that decrease the fat content in farm animals. The purpose of this study was to develop an analytical LC-MS/MS confirmatory method for the detection of nine β-agonists in bovine retina and liver tissues. The obtained CCα values ranged from 0.29 to 1.54 µg kg–1 in retina and from 0.03 to 0.18 µg kg–1 in liver, and CCβ values from 0.50 to 2.63 µg kg–1 and from 0.05 to 0.30 µg kg–1, respectively. Additionally, the importance of a matrix effect in these two tissues for the achievement of accurate detection of non-compliant samples was studied and discussed. It was concluded that the main characteristic of this phenomena is its considerable variability from one animal to another. Also, the total amount of matrix in the final extract can provide differences in the matrix-matched calibration line.

Effects of bovine pregnancy on the fatty acid composition of milk: the significance for humans needs

ABSTRACT Milk from 40 Holstein dairy cows was collected from two different farms in Galicia (Spain). The differences in the fatty acid composition of two groups of cows, 20 pregnant and 20 non-pregnant, was studied to determine whether pregnancy status is a determinant factor that can alter the fatty acid profile of milk. Gas-chromatography (GC) coupled to flame ionisation detection (FID) was used for the determination of the fatty acids. Differences in the milk fatty acids between pregnant and non-pregnant cows were pronounced showing statistically significant differences for some fatty acids and the total saturated and monounsaturated fatty acids. Milk from non-pregnant cows was lower in saturated fatty acids and higher in monounsaturated fatty acids (unlike milk from pregnant cows). The effects of the consumption of bovine milk, particularly milk fat, on human health have been studied in depth and sometimes are associated with negative effects, but milk has also several beneficial characteristics linked to some fatty acids.

Fatty acid composition of breast milk in Galicia (NW Spain): A cross-country comparison

Based on the premise that the fatty acid composition of human milk can be substantially altered by diet, the current study investigated the fatty acid profile (fattyacidome) of breast milk in Galicia, a small region located in the north-west of Spain and characterized by the Southern European Atlantic Diet (SEAD). A cross-country comparison was also performed to assess worldwide variety and diet impact, reviewing the profiles reported various European, North and South American, Asian and African countries and Australia. Galician human milk appeared similar to the rest of Europe, with some particular features related to the SEAD (dairy, pork, beef and sunflower and olive oils), such as relatively high levels of linoleic acid and lower α-linolenic acid. The results also showed the existence of woman-specific profiles and significant changes over lactation in some fatty acids. Worldwide, the fatty acid profiles were similar, with the clear exception of Asiatic breast milk. The impact of fatty acids on infant health warrants further investigation.