Fatty acids analysis by capillary electrophoresis: Fundamentals, advantages and applications.

This review covers the know-how of the Grupo de Química Analítica e Quimiometria regarding the analysis of fatty acids by capillary electrophoresis acquired over its 20 years of existence. Therefore, the fundamentals, advantages, and applications of this technique for analyzing different fatty acids in samples such as food, oils, cosmetics, and biological matrices are presented and discussed. Capillary electrophoresis is, thus, shown as an interesting and valuable separation technique for the target analysis of these analytes as an alternative to the gas chromatography coupled to flame ionization detection, as it offers advantages over the latter such as low analysis times, low sample and reagent consumption, the use of a nondedicated column, and simpler sample preparation. In addition, the methods shown in this literature review can be useful for quality control, adulteration, and health-related research by regulatory agencies.

Determination of creatinine in urine and blood serum human samples by CZE-UV using on-column internal standard injection.

Creatinine is a well-stablished biomarker for kidney malfunctions and for normalization parameter of urinary quantitative information. Recently, metabolic studies have been discovering other functionalities for creatinine tests in human urine and blood serum. In this work we present an enhanced capillary electrophoresis (CE) based protocol for determination of creatinine. CE is a high-throughput separation technique that have been getting attention through the last decades and might be considered to be adopted as an analytical instrumentation for clinical purposes. In the proposed method, we performed a short injection program with on-column addition of internal standard. Additionally, the method allows a simultaneous screening of non-proteinogenic amino acids that could be considered for metabolomics purposes. We design a pilot study that successfully estimated the creatinine value in 100 urine samples with (2.85 ± 1.78) mg dL-1 LOD; (8.24 ± 5.93) mg dL-1 LOQ and 82.4% accuracy. Considering that serum creatinine is also included in the clinical laboratory routines for estimated Glomerular Filtration Rate dosage, the method was complementary applied to 10 blood serum samples, which resulted in a model with (0.4 ± 0.2) mg dL-1 LOD; (2.0 ± 0.6) mg dL-1 LOQ and 83.8% of accuracy. All results were in agreement with reference values. The proposed method promotes a great analytical frequency and reproducibility with enhanced specificity compared with the ongoing protocol by Jaffe's reaction, thereby proving to be useful as an alternative for creatinine exams that might help complete a diagnosis of a series of health-related issues.

Short-End Injection Capillary Electrophoresis and Multivariate Analysis for Simultaneous Determination of Heavy Metals in Passiflora incarnata Tea.

An ultra-fast method for the simultaneous determination of heavy metals in Passiflora incarnata tea by capillary electrophoresis (CE) using a short-end injection combined with multivariate analysis was proposed. Separation was conducted by hydrodynamic injection (5 s at 0.5 psi) using the short-end injection procedure in a fused uncoated silica capillary (50 cm total length, 10.2 cm effective length, 50 µm i.d.) with separation time less than 2 min. An indirect UV detection at 214 nm was employed by using imidazole as a chromophore. The buffer used was 6 mmol/L hydroxybutyric acid (HIBA). The optimum conditions by full factorial with a central point were achieved by 18-crown-6 concentration (23.3 mmol L−1), voltage (+11.4 kV), methanol concentration (3.8%), and temperature (20 °C). The method showed good linearity (R2 > 0.998) for both Cd and Pb, inter-day precision of less than 14.49%, and an adequate limit of quantification only for Cd (LOQ < 0.5 µg mL−1 for Cd) based on the US Pharmacopeial Convention limit requirements for elemental impurities. After method validation, the method was applied to Passiflora incarnata tea samples from a local market. Furthermore, the developed method showed great potential for the determination of metals in other samples with proper sample preparation procedures.

Determination of hydroquinone and benzoquinone in pharmaceutical formulations: critical considerations on quantitative analysis of easily oxidized compounds.

Hydroquinone is a skin-lightening agent used as an active ingredient in topical dermatological formulations prescribed for treating cutaneous diseases caused by hyperpigmentation. Despite being widely used, some toxicological aspects have been associated with these products, mainly due to overdosage and long-term use combined with the easy oxidation of hydroquinone. In this work, an investigative study has been done to gather enough data for selecting a quantitative analytical method for quality control purposes that considers the ease of oxidation not only within the product but also during the experimental procedures. After studying the influence of pH, reversibility, sampling, and standard solution preparation on the redox reaction between hydroquinone and benzoquinone by using spectroscopic, electrophoretic, and electroanalytical measurements, a reliable, fast, and selective chronoamperometric method was achieved. The optimized method was used for the analysis of samples, previously diluted in Britton-Robinson (BR) buffer (pH 5.5) and methanol (1 : 9, v/v), by applying a potential fixed at 0.4 V. A glassy-carbon working electrode, lab-made Ag/AgCl(sat) and platinum wire as a reference electrode and auxiliary electrodes, respectively, and BR buffer (pH 5.5) as supporting electrolyte were the additional experimental conditions used. Analytical performance parameters were verified to confirm the applicability of the new method (LOD 4.22 µmol L-1 and LOQ 14.1 µmol L-1; recovery mean value of 100% with 0.22% RSD). A gel topical formulation containing 4% (w/w) hydroquinone was analyzed through the developed method for determination of dosage and oxidation traces, and a content of 3.53 ± 0.095% (w/w) was found with no indications of degradation.

Effects of Avocado Oil Supplementation on Insulin Sensitivity, Cognition, and Inflammatory and Oxidative Stress Markers in Different Tissues of Diet-Induced Obese Mice.

Obesity induces insulin resistance, chronic inflammation, oxidative stress, and neurocognitive impairment. Avocado oil (AO) has antioxidants and anti-inflammatory effects. This study evaluated the effect of AO supplementation on obese mice in the adipose tissue, muscle, liver, and hippocampus. Male C57BL/6J mice received a standard and high-fat diet (20 weeks) and then were supplemented with AO (4 mL/kg of body weight, 90 days) and divided into the following groups: control (control), control + avocado oil (control + AO), diet-induced obesity (DIO), and diet-induced obesity + avocado oil (DIO + AO) (n = 10/group). AO supplementation was found to improve insulin sensitivity and decrease hepatic fat accumulation and serum triglyceride levels in DIO mice. AO improved cognitive performance and did not affect mood parameters. Oxidative marker levels were decreased in DIO + AO mice in all the tissues and were concomitant with increased catalase and superoxide dismutase activities in the epididymal adipose tissue and quadriceps, as well as increased catalase activity in the liver. AO in obese animals further induced reductions in TNF-α and IL-1ß expressions in the epididymal adipose tissue and quadriceps. These results suggest that AO supplementation has the potential to be an effective strategy for combating the effects of obesity in rats, and human studies are needed to confirm these findings.

Determination of α- and ß-acids in hops by liquid chromatography or electromigration techniques: A critical review.

Hop plays an essential role in brewing beer and its study and analysis is of paramount importance. - and -acids are considered two of the most important hop components. While -acids are associated with the bitter flavor, -acids have antimicrobial effects. This work aims to critically review the published analytical methods for - and -acids determination in hops employing separation methods in liquid medium: liquid chromatography (LC) and capillary electrophoresis (CE). The types of hop samples, the optimized protocols to extract the hop acids, and the main instrumental conditions for both LC and CE techniques are highlighted and discussed. Specific and critical aspects of the - and ß-acids separation by LC and CE and some challenges in this field are raised. Several key aspects discussed in this review may be of practical importance for brewers, whether in the microbrewery or industry and for researchers in the brewing field.

Origin geographical classification of green coffee beans (Coffea a rabica L.) produced in different regions of the Minas Gerais state by FT-MIR and chemometric.

The present work was proposal the potential evaluation of Fourier-Transform Mid-Infrared (FT-MIR) associated with chemometric approach in green beans, in order to discriminate the origin of special Arabica coffees in a single state that has heterogeneous environments. Partial Least Squares Discriminant Analysis (PLS-DA) model presented as result: 3 latent variables, R 2 X (cum) = 0.892, R 2 Y (cum) = 0.659; Q 2 Y (cum) = 0.494, RMSEP = 0.182387, p-value CV-Anova = 0.009, 100% of both sensitivity and specificity and the prediction classification obtained was: 100, 83.33, 100, 83.33% for class 1, class 2, class 3 and class 4, respectively. These results can be considered adequate for the proposed hypothesis. The obtained results that the regions have markers such as trigonelline, chlorogenic and fatty acids, sensitive to absorption in the mid-infrared and that are able to determine the origin of green coffee beans of Arabica. Thus, the FT-MIR associated with chemometrics has the potential to employ speed, modernity and cost reduction in the certification of origin of coffees.

Determination of purity and anionic exchange efficiency of amino acid ionic liquids synthesis by multiple-injection capillary zone electrophoresis.

The purity of ionic liquids (IL) is important for its performance, so the methods able to quantify low concentration impurities are necessaries. Therefore, this paper aims to determine the purity and the anionic exchange efficiency for the preparation of amino acids ionic liquids (AAIL). For this, a Multiple-Injection Capillary Zone Electrophoresis (MICZE) method with direct UV detection was developed and optimized for iodide (I-) determination as impurity of AAIL synthesis, comparing this method with traditional injection modes. Furthermore, this paper aims to demonstrate the use of factorial design methods for the optimization of MICZE method. The method optimization allowed five consecutives I- injections of sample in a single run, with analysis time of less than 3 min, showing a larger analytical frequency, counting with 31 injections per hour. It was possible to determine the high purity of the prepared and analyzed AAIL, ranging from 89% to 95% and its overall ionic exchange yield varying from 55% to 87%.

Determination of antimalarial drugs in pharmaceutical formulations and human blood by liquid chromatography: a review.

Malaria is a life-threatening disease being treated by oral medication. This is the best treatment to reduce morbidity and mortality, prevent disease progression to the most severe form, lower the transmission of the disease and hinder the appearance of strains resistant to antimalarials. According to the World Health Organization, the most common antimalarial drugs are chloroquine, primaquine, mefloquine, lumefantrine, artemether, and artesunate in single dosage forms or fixed-dose combination. Within this context, the present review aims to show the evolution of different analytical methods that have been applied to the determination of these antimalarial drugs in pharmaceutical formulations and human blood by liquid chromatography in the last 10 years, along with statistical analyses of the methods.

A capillary electrophoresis method for free fatty acids screening and acidity determination in biodiesel.

The advent of policies that incentivize or require alternative diesel fuels has increased the demand for the development of fast analytical methods aiming for the quality control of these fuels. This study approached an alternative method for the determination of biodiesel acidity employing capillary zone electrophoresis based on free fatty acids screening and quantification. Sample preparation comprised vortex-assisted liquid-liquid extraction of free fatty acids and was a crucial step for analysis. It was studied through a 32 full factorial design considering sample mass and the stirring time. Then, solvent suitability was evaluated univariately. The free fatty acid screening was carried out employing a capillary zone electrophoresis method able to separate C16:0, C18:0, C18:1 n-9, C18:2 n-6, and C18:3 n-3, major fatty acids in a variety of vegetable oils used for biodiesel synthesis. In addition to the straightforward sample preparation protocol, the running time of the developed method was only 12 min. Moreover, ultraviolet absorption indirect detection of analytes was approached to avoid analytes derivatization, considering the lack of chromophore groups in saturated fatty acids. Statistical tests did not evidence any significant differences in the biodiesel acidity determination expressed in percentage of free fatty acids when comparing the proposed capillary zone electrophoresis method and the traditional potentiometric titration approach within the 95% confidence interval, which demonstrates the suitability of this alternative method for the biodiesel quality control in routine.

Capillary electromigration methods for fatty acids determination in vegetable and marine oils: A review.

Fatty acids determination is of paramount importance for quality control and suitable labeling of edible oils, required by regulatory agencies in several countries, and fast methods for this determination are worldly desired. This review article aimed to explore the available analytical methods for vegetable and marine oils analyses employing CE, which can be a straightforward and faster alternative than GC methods for fatty acid determination, considering some purposes. CE usually offers the possibility of a rapid analysis with a simple preparation of the sample, without requiring specific columns, which are inherent advantages of the technique. Instrumental conditions and the key points about fatty acids determination employing the technique are highlighted, and the main challenges and perspectives are also approached. Potential use of CE for edible oil analyses has been demonstrated for research and routine, which can be of interest for industries, regulatory agencies, and edible oil researchers. Therefore, we have explored the analytical approaches described in the last decades, intending to spread the interest of CE methods for fatty acid monitoring, label accuracy assessment, and food authenticity evaluation of edible oils.

Differentiation of aromatic, bittering and dual-purpose commercial hops from their terpenic profiles: An approach involving batch extraction, GC-MS and multivariate analysis.

Terpenes are one of the main classes of compounds in hops (Humulus lupulus, L). They play an important role in brewing due to their central function, which is related to beer aroma. A screening of terpenes in several commercial hop varieties was carried out by gas chromatography coupled to mass spectrometry after employing a simple, straightforward and high throughput extraction method. A single batch extraction, using hexane as solvent, was employed to obtain the terpenic fraction of the hop samples. Nineteen terpenes were identified in analyzed samples with ß-myrcene (2.22-45.30%), α-humulene (20.20-67.64%), and ß-caryophyllene (9.97-24.62%) being the major terpenes in all samples. The studied system was multivariate modeled by principal component analysis. Based on the proposed approach, it was possible to correlate the terpenic hop profiles to their specific purpose in the brewing industry and to distinguish aromatic hops (high α-humulene content), bittering hops (high ß-myrcene content), and dual-purpose hops (more complex and intermediate terpenic profile) among the samples.

Simultaneous separation of artesunate and mefloquine in fixed-dose combination tablets by CZE-UV.

A novel method was proposed for simultaneous determination of artesunate (ATS) and mefloquine (MFQ) in fixed-dose combination tablets by capillary zone electrophoresis with simultaneous direct and indirect detection by ultraviolet (CZE-UV). The background electrolyte, consisting of 30/15 mmol L-1 TRIS/3,5-dinitrobenzoic acid buffer at pH 8.2, a chromophore buffer, was selected taking into account a detailed study involving the effective mobility vs. pH curves of the analytes and electrolyte compounds in association with the very low molar absorptivity of ATS. Suitable separation conditions, considering voltage, temperature and buffer concentration as factors, were achieved through the 33 Box-Behnken design investigation. The optimum baseline separation conditions were: injection pressure of 30 mbar for 10 s, cartridge temperature of 22.5 °C and positive voltage of +30 kV. The method proved to be rapid (5 minutes), simple, selective, linear (r2 > 0.98), precise (relative standard deviation (RSD): ATS < 2.9% and MFQ < 2.2%) and accurate (recoveries: ATS 98.13-102.96% and MFQ 98.75-106.77%), proving to be suitable for routine quality control analysis.

Improved anti-Cutibacterium acnes activity of tea tree oil-loaded chitosan-poly(ε-caprolactone) core-shell nanocapsules.

The purpose of this study was to develop tea tree oil (TTO)-loaded chitosan-poly(ε-caprolactone) core-shell nanocapsules (NC-TTO-Ch) aiming the topical acne treatment. TTO was analyzed by gas chromatography-mass spectrometry, and nanocapsules were characterized regarding mean particle size (Z-average), polydispersity index (PdI), zeta potential (ZP), pH, entrapment efficiency (EE), morphology by Atomic Force Microscopy (AFM), and anti-Cutibacterium acnes activity. The main constituents of TTO were terpinen-4-ol (37.11 %), γ-terpinene (16.32 %), α-terpinene (8.19 %), ρ-cimene (6.56 %), and α-terpineol (6.07 %). NC-TTO-Ch presented Z-average of 268.0 ± 3.8 nm and monodisperse size distribution (PdI < 0.3). After coating the nanocapsules with chitosan, we observed an inversion in ZP to a positive value (+31.0 ± 1.8 mV). This finding may indicate the presence of chitosan on the nanocapsules' surface, which was corroborated by the AFM images. In addition, NC-TTO-Ch showed a slightly acidic pH (∼5.0), compatible with topical application. The EE, based on Terpinen-4-ol concentration, was approximately 95 %. This data suggests the nanocapsules' ability to reduce the TTO volatilization. Furthermore, NC-TTO-Ch showed significant anti-C. acnes activity, with a 4× reduction in the minimum inhibitory concentration, compared to TTO and a decrease in C. acnes cell viability, with an increase in the percentage of dead cells (17 %) compared to growth control (6.6 %) and TTO (9.7 %). Therefore, chitosan-poly(ε-caprolactone) core-shell nanocapsules are a promising tool for TTO delivery, aiming at the activity against C. acnes for the topical acne treatment.

Prediction of Fatty Acids in Chocolates with an Emphasis on C18:1 trans Fatty Acid Positional Isomers Using ATR-FTIR Associated with Multivariate Calibration.

This work aimed to predict C18:1 TFA isomers as well as other groups of fatty acids (saturated, monounsaturated, polyunsaturated, and total TFA) in chocolates by ATR-FTIR and partial least square regression. The quantification of fatty acids in representative samples (white, dark, and milk chocolates) was rapid (<30 s) and did not require derivatization. The optimized models showed satisfactory linear correlations compared to a reference gas chromatographic method. Coefficients of correlation for prediction considering C18:1 positional isomers were 0.973 (trans 6-8), 0.991 (trans 9), 0.991 (trans 10), 0.988 (trans 11), and 0.998 (trans 12). When considering fatty acids groups, these coefficients ranged from 0.965 to 0.999. The obtained results indicate that this straightforward procedure is suitable for chocolate analysis, for determining its general lipid composition and TFA isomeric profile, which would be of great interest for quality control programs in the face of the new TFA regulations.

Effects of enzymatic lactose hydrolysis on thermal markers in lactose-free UHT milk.

Lactose-free products are more susceptible to chemical and physical modifications during heating and storage, due to the release of glucose and galactose during enzymatic processing, both more reactive than lactose. The present study demonstrates the effect of enzymatic lactose hydrolysis on 5-hydroxymethylfurfural (HMF), whey protein nitrogen index (WPNI) and lactulose used as thermal markers for UHT milk process monitoring. Six milk leading brands which provided regular and lactose-free UHT milk were selected, giving a total of 12 UHT milk samples analyzed in authentic duplicates. All lactose-free samples showed high levels of HMF index (42.15 µmol L-1, against 13.11 µmol L-1 for regular samples) and low lactulose contents (13.03 mg 100 mL-1, against 35.59 mg 100 mL-1 of regular ones). High variations in HMF (55-85%) and lactulose (42-91%) intra-brand analysis indicated that both markers are influenced by the lactose hydrolysis process. The paired t test indicated there was no difference among WPNI indexes of regular and lactose-free milks suggesting that this thermal marker is suitable to infer about heat damage in lactose-free dairy matrices.

Nb2O5 supported in mixed oxides catalyzed mineralization process of methylene blue.

Heterogeneous photocatalysis has become a significant green technology for water treatment. The application of Nb2O5 catalyst for the photodegradation of contaminants has merged as an important tool to this process. Furthermore, it is known that catalytic phases supported on metal oxides are an alternative method for enhancing its activity. In this work, supported Nb2O5 on mixed oxides as catalyst was applied to degrade methylene blue dye, leading to almost 100% of dye degradation without the need of any additives, after only three hours of sunlight exposure. The effect of catalyst concentration, exposure time and light source were investigated. The best catalyst activity was found at 1.5 g L-1 and for higher catalyst concentrations the degradation was kept constant. Plausible intermediates of this degradation process were observed and characterized by NMR, LC/MS and CZE techniques. After degradation, the catalyst was recovered and could be further re-applied in other three reaction cycles without significant loss of catalytic activity.

Rapid method for the determination of citrate, phosphate and sulfite in seafood by capillary zone electrophoresis.

Since seafood is susceptible to decomposition, additives may be used to maintain its quality. However, some additives may be improperly used to disguise spoilage, thus resulting in food fraud. Market growth demands faster and more reliable quality control tools that incorporate the most common additives in a single analysis. This study developed a rapid analytical method for the determination of citrate, phosphate and sulfite in seafood by capillary zone electrophoresis with indirect UV-Vis detection. Electrophoretic separation was achieved in less than 3.5 min. The background electrolyte consisted of 20 mmol L-1 of benzenesulfonic acid and 45 mmol L-1 of aminocaproic acid. After validation, the method was applied for 24 seafood real samples. Citrate was found in five samples. Four samples presented higher phosphate and sulfite concentrations than those permitted by Brazilian legislation. Good analytical performance indicates that the method is a viable alternative for food control in routine analysis.

Fast capillary electrophoresis method for determination of docosahexaenoic and eicosapentaenoic acids in marine oils omega-3 supplements.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential omega-3 fatty acids (FA) in human nutrition. Dietary supplements containing these FA are available in the market and there is a need to assess their quality to prevent frauds. The purpose of this work was to optimize and validate a fast capillary electrophoresis (CE) method to determine EPA and DHA content in marine oils omega-3 supplements. Sample preparation comprised only a saponification step and analysis time was 8 min. Validation was performed according to limits of detection and quantification, linearity, accuracy and repeatability. Ten real samples of marine oil supplements were analyzed by CE and compared to conventional gas chromatography method. No significant differences between both methods were found within 95% confidence interval. Overall, CE method was successful to FA quantification and it could be used for fast FA monitoring during omega-3 supplement manufacture, final product quality assurance and labelling.

Lipid Composition of Brazilian Chocolates and Chocolate Products with Special Emphasis on Their Fat Origin and Trans C18:1 Isomeric Profile.

The aim of this work was to provide recent fatty acid (FA) profiling of chocolates and chocolate products, principally C18:1 trans FAs (TFAs). Thirty-two samples were analyzed by gas chromatography and FAs were quantified. The total TFA content declared in chocolate labeling and the real TFA content were compared. The TFA content ranged from 0.04 to 2.51 g/100 g of sample, and it was noticed that several manufacturers were underestimating the total TFA content in their labeling. The main TFA isomers quantified were C18:1 trans-9 (0.006-0.244%), C18:1 trans-10 (0.009-0.392%), and C18:1 trans-11 (0.013-0.464%), expressed in g/100 g of sample. Principal component analysis was used to discriminate industrial fats from natural trans fats based on the isomeric TFA profile and dairy fat (DF) biomarkers allowing to group samples in four clusters: high TFA content and high DF content, high TFA content and low DF content, low TFA content and high DF content, and low TFA content and low DF content.