Determination In Milk Research Articles

Near-infrared carbon dots for cell imaging and detecting ciprofloxacin by label-free fluorescence sensor based on aptamer.

A label-free fluorescence sensor based on near-infrared carbon dots (NIR-CDs) and aptamer is described for the highly sensitive and selective detection of ciprofloxacin (CIP). NIR-CDs were synthesized from polyethyleneimine and reduced glutathione by one-step hydrothermal method. The electrostatic interaction between the positively charged carbon dots and the negatively charged aptamer resulted in fluorescence quenching. After the addition of CIP, the specific binding between CIP aptamer and CIP was stronger, resulting in fluorescence recovery. Under the optimal experimental conditions, the recovered fluorescence intensity has a linear relationship with the concentration of CIP in the range 0.5-800ng/mL, and the detection limit is 0.167ng/mL. The prepared carbon dots have excellent optical properties and biocompatibility, and due to their emission characteristics in the near-infrared window, they can be used for biological imaging, which has also been confirmed in the experiment. The feasibility of the label-free fluorescence sensor for the detection of CIP is also proved by confocal fluorescence imaging. The detection results of CIP determination in milk by this sensor are satisfactory, indicating that the developed sensor has great application potential.

Electrophoretically Deposited Green Synthesized Silver Nanoparticles Anchored in Reduced Graphene Oxide Composite Based Electrochemical Sensor for Detection of Bisphenol A

Bisphenol A (BPA), an endocrine-disrupting compound, is used in beverage and food packaging, leaches into the water and food source cycles affecting humans and the environment due to the thermodynamic instability of BPA. Herein, we report a sensitive, quick, economical, simple, and selective electrochemical platform exploring green synthesized silver nanoparticles (AgNps) anchored in reduced graphene oxide (RGO) composite for BPA determination in milk and water samples. For confirmation of the synthesis of AgNps-RGO composite, characterizations were done with X-ray diffraction, UV–visible spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and scanning electron microscopy. The sensor platform was fabricated using indium tin oxide (ITO) glass substrate through electrophoretic deposition. The sensor electrode (AgNps-RGO/ITO) achieved a sensitivity of 2.56 μA (log μM)−1 cm−2, a detection limit of 0.14 μM, and linear response in the range of 1.9 × 10−10 to 0.820 μM. This is mainly ascribed to the synergetic benefits of AgNps and RGO, which are synthesized in situ through the green route using Cinnamomum tamala leaf extract. The sensor showed insignificant interference from its analogs, inorganic and organic species, along with good repeatability and reproducibility. The developed sensor demonstrated good potential application to detect BPA with acceptable recoveries and their relative standard deviation values.

Development of paper devices with conductive inks for sulfanilamide electrochemical determination in milk, synthetic urine, and environmental and pharmaceutical samples

Development of paper devices with conductive inks for sulfanilamide electrochemical determination in milk, synthetic urine, and environmental and pharmaceutical samples

Vitamin B12 quantification in human milk – Beyond current limitations using liquid chromatography and inductively coupled plasma – Mass spectrometry

Vitamin B12 plays a key role in human biological functions and is vital in the neurological development of infants. The assessment of the vitamin B12 intake in exclusively breastfed babies depends on the reliability of its determination in milk. In this report, we present a new accurate and robust method for quantification of vitamin B12 in human milk. A highly specific sample preparation is applied, associated with chromatographic separation and detection by ICP-MS. Excellent sensitivity and accuracy are reported, with recovery values well within acceptability limits (80–120%), within- and between-day variability are lower than 10% and 15% respectively. Strong correlation with a microbiological assay was observed (r2 = 0.9) within the validation range (40–1000 pmol/L, corresponding to 54 to 1355 ng/L). The method can be used to routinely monitor vitamin B12 in clinical or population observational studies, determine infant’s intake or assess efficacy of mother’s supplementation.

Hydrogen peroxide residue determination in food samples by a glassy carbon electrode modified with CuO-SWCNT-PDDA nanocomposites

Copper oxide-single walled carbon nanotube (CuO-SWCNT) hybrid nanostructure and poly-(diallyldimethylammonium chloride) (PDDA) modified glassy carbon electrode (GCE) for sensitive enzyme-free H2O2 detection has been fabricated via electrostatic interaction strategies. Characterization by XRD, IR and SEM showing that CuO was coated on SWCNT molecular wires, and positively charged PDDA attached to the negatively charged SWCNT, thus CuO-SWCNT-PDDA was constructed. The reduction peak current of H2O2 was significantly increased due to the catalytic property of CuO, which was further enhanced by the synergic effect of SWCNT due to its improvement of electron transfer rate. The calibration curve was linear in the range of 1–1150 µM with a detection limit of 0.39 µM. The electrode coupled with amperometric measurement was successfully applied in H2O2 residue determination in milk and the soaking solutions of chicken paw samples. The results have no remarkable difference compared with the reference UV–Vis method.

Synthesis of highly electroactive nanoflowers like manganesetin oxide and electroanalytical application for chloramphenicol determination in milk and honey samples

Abstract In this report, we have described the disposable electrochemical sensor for the detection of chloramphenicol (CMP) based on MnSnO3 NFs (MSO NFs) modified glassy carbon electrode (GCE). MSO NFs were successfully synthesized through a simple and low-cost coprecipitation approach. FE-SEM, HR-TEM, FTIR, and XRD are used to examine the physical and chemical properties of as-synthesized MSO NFs. The electrochemical activity and performance of the proposed electrode towards the CMP sensor is explored by electrochemical techniques namely CV and DPV. The MSO NFs fabricated electrode showed a rapid current response towards CMP reduction. Under the optimum condition, a linear range is 0.003 μM to 92.21 μM, with low detection limit is calculated is 1 nM. In addition, the proposed sensor has achieved good reproducibility, and excellent selectivity, long-term stability. It was applied to the determination of CMP in spiked milk and honey food samples with satisfactory results. This result demonstrated the MSO NFs was potentially possible for practical applications. All these features, suggest that the MSO NFs is a promising candidate as a new class of electrocatalyst for the highly selective electrochemical sensor for CMP.

Meldonium determination in milk and meat through UHPLC-HRMS

A simple and sensitive procedure for the quantification of meldonium in milk and meat by UHPLC-HRMS is presented. Some products were investigated to contain this substance due to using a veterinary drug called “Emidonol”. According to the instruction for this drug, it can be used for injection (for cows) and as an additive in drinking water for chickens. Although meldonium is not a threat for human health, it is strictly prohibited in professional sports according to WADA Prohibited List. Sample preparation conditions were optimized for both matrices that allowed to eliminate matrix effects and achieve reproducible and accurate results. Protein precipitation with dilution were applied for milk samples, while chicken meat and liver were homogenized with quartz sand to achieve satisfactory meldonium recovery. The results of milk and meat samples analysis purchased at the farmers’ fair are presented in this article. Meldonium concentration in raw milk was investigated to be up to 880 ng/mL. However, pasteurization can be used for partial cleanup from meldonium (up to 2 times). The same research was conducted for chicken meat and liver. Thermal treatment shows a good result for a meat cleanup. The proposed method was partially validated, limits of detection and quantification were established for each matrix.

Green method using water for lactose and lactulose extraction and determination in milk by high-performance liquid chromatography with refractive index detection

Lactose is the main carbohydrate found in milk. However, the ultra-high temperature (UHT) process might convert lactose to lactulose by isomerization. Lactulose can be prebiotic; nevertheless, at high concentrations, it can be fermented in the gastrointestinal tract because it is not hydrolyzed by enzymes. In view of the increase in lactose intolerant consumers, it becomes necessary to determine the presence and amounts these compounds in UHT milk. Hence, this study aims to propose and validate a method with simple sample preparation to measure lactose and lactulose contents in milk. Following green chemistry principles, the proposed method is distinguished by the use of only water in the extraction step, with an effective sample clean-up step performed via ultracentrifugation; likewise, water was also employed as the mobile phase for high-performance liquid chromatography with refractive index detection analysis. Moreover, the proposed method allows for the verification of the efficiency of the lactose-free milk process by monitoring lactose residual levels in addition to measuring the degradation contents of glucose and galactose. Further, the developed method even represents an alternative for detecting counterfeit milk made with added sucrose, ensuring the quality of milk for consumers.

90Sr/90Y determination in milk by Cherenkov radiation after microwave digestion

In a case of a nuclear emergency, rapid radiostrontium analysis in milk is essential, since milk ingestion poses a considerable risk for radiostrontium implantation in the human body especially in infants. The main idea of this study is to investigate a simple, fast and low-cost method for 90Sr determination in milk samples, through microwave digestion followed by Cherenkov radiation detection on a Liquid Scintillation Counter Quantulus 1220™. Obtained results set method’s limit on a screening test for emergency situations only (uncontrolled nuclear waste discharges/nuclear power plant accidents etc.), adequate for a quick reliable estimate of 90Sr content.

A spectrophotometric procedure for sialic acid determination in milk employing a flow-batch analysis system with direct heating

The quantitative determination of sialic acid can indicate the addition of cheese whey to milk. This work describes an automated procedure to determine sialic acid in milk samples using a flow-batch system analysis with direct heating. The sialic acid quantification was based on a reaction between the sialic acid and acid ninhydrin producing a stable compound with maximum absorption at 470 nm. The flow-batch system was designed using heating and spectrophotometric detection in the reaction chamber. Under the optimum experimental conditions, a linear response ranging from 1.0 to 10.0 mg L−1 sialic acid (R = 0.99 and n = 7), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.239 and 0.726 mg L−1, respectively, a relative standard deviation of 1.90% (n = 10) for a reference solution of 4.0 mg L−1 sialic acid and a sampling rate of 7 determinations per hour were achieved. Analysis of eleven milk samples, application of the t-test to the results found, and comparison with the official method provided no significant differences at a 95% confidence level. Compared to the official method, the proposed system reduced reaction time by 50%, temperature of the reaction by 30%, and diminished the consumption of reagents and samples by 90%. Thus, the use of the proposed system is an economically viable and environmentally friendly option for the determination of sialic acid in milk.

Rapid and label-free detection of Brucella melitensis in milk and milk products using an aptasensor

In this work, a novel quartz crystal microbalance (QCM) aptasensor is designed for the diagnosis of Brucella melitensis bacteria, which affects the Mediterranean fever (brucellosis) from the zoonotic diseases that are very common in the Middle East Countries. The method is based on the selection of B. melitensis bacterium from solutions using B. melitensis specific binding aptamer (Apt) attached magnetic nanoparticles. The surface of the magnetic nanoparticles (i.e.,Fe3O4) was modified by 3-aminopropyltriethoxysilane (APTES) and then grafted with a hydrophilic macromonomer poly(ethyleneglycol)-methacrylate (PEG-MA) as a first block polymer and glycidylmethacrylate (GMA) as a second block functional polymer via atom transfer radical polymerization (ATRP) method [Fe3O4 @SiO2 @p(PEG-MA-GMA)], then, the specific binding aptamer was immobilized. The aptamer immobilized magnetic nanoparticles were used for the pre-concentration of the target bacterium, and the same aptamer sequence was also immobilized on the QCM chip and used for the quantitative detection of B. melitensis using QCM aptasensor. The detection limits of the QCM aptasensor were in the range 1.02–1.07 CFU mL−1, with recoveries up to 79%. The synthesized [Fe3O4 @SiO2 @p(PEGMA-GMA)] nanoparticles showed a good permanence and high isolation recoveries for the pull down of the target bacterium from food samples, after recycling eight times. The method was successfully applied to target bacterium determinations in milk and milk product samples.

Undergraduate laboratory experiment on determination of total protein content in milk powder by moving reaction boundary titration.

Laboratory exercises focused on protein quantification are frequently conducted in traditional undergraduate biochemistry laboratory curriculum. The laboratory course described here is designed to provide students with experience in measurement of protein content in milk powder by moving reaction boundary titration (MRBT), a new rapid technique for total protein content determination in milk. In addition, this approach is weakly influenced by nonprotein nitrogen reagents such as melamine and urea. The course was done as three weekly laboratory exercises. First, students established a standard curve for milk protein concentration by MRBT method. Then, students investigated the influence of nonprotein nitrogen reagents on MRBT method. Finally, students made a comparison among three different protein quantification methods (MRBT, Biuret, and Kjeldahl method). From the experiments, students grasped the concept and advantages of MRBT and deepened the understanding of protein quantification. This course offer students the opportunity to be exposed to an advanced technique, which may have practical significance to their future study and work in the life science field. © 2018 International Union of Biochemistry and Molecular Biology, 46(6):644-651, 2018.

Coccidiostats in milk: development of a multi-residue method and transfer of salinomycin and lasalocid from contaminated feed

ABSTRACTA confirmatory multi-residue method was developed for the determination in milk of 19 coccidiostats (amprolium, arprinocid, clazuril, clopidol, decoquinate, diclazuril, ethopabate, halofuginone, lasalocid, maduramicin, monensin, narasin, nicarbazin, nequinate, robenidine, salinomycin, semduramicin, toltrazuril sulfone and toltrazuril sulfoxide). Sample preparation utilising extraction with organic solvent and clean up by SPE and freezing was found reliable and time-efficient. Optimised chromatography and MS conditions with positive and negative ESI achieved sufficient sensitivity and selectivity. Validation experiments has proven method usefulness for routine analysis of coccidiostats in milk samples. An on-farm study conducted on dairy cows fed with experimentally contaminated feed with salinomycin and lasalocid showed negligible transfer to milk. No residues of lasalocid were found in collected samples. Salinomycin was found only in 5 of 168 samples analysed, while the concentrations of salinomycin in those samples (0.119–0.179 µg kg–1) was significantly below the limit of salinomycin in milk set by European Union legislation. Such low concentrations of both coccidiostats cannot be explained by conjugation during dairy cows’ metabolism, as shown by experiments with enzymatic hydrolysis.

Rapid method for radiostrontium determination in milk in emergency situations using PS resin

This study describes a new and rapid procedure for radiostrontium determination in milk samples based on the use of plastic scintillation resins (PS resins). The proposed method reduces the time of analysis by at least 2 h by combining separation and measurement preparation into a single step and optimizing the pre-treatment steps. The method is robust and reproducible, with good total recoveries (65% on average) and a relative bias for total radiostrontium activity (89Sr + 90Sr) below 7%. The minimum detectable activity for 100 mL of milk sample measured for 60 min is about 0.34 Bq L−1. The proposed method can quantify radiostrontium content in 5 h, which makes it suitable for use in emergency situations.

Vitamin B12 determination in milk, whey and different by-products of ricotta cheese production by ultra performance liquid chromatography coupled with tandem mass spectrometry.

Vitamin B12 (cobalamin) is a metal complex composed of a central cobalt ion bonded to six ligands. It is essential for major biological functions such as protein, fat and carbohydrate metabolism, the maintenance of the central nervous system, and the formation of red blood cells. Since mammals cannot synthesize cobalamin, dietary intake represents the only natural source for humans. Dairy products can provide significant levels of cobalamin; moreover, the European Food Safety Authority (EFSA) panel has set the recommended intake at 4 μg/day for adults. Vitamin B12 content was determined in milk and several matrices related to the process of transformation of the residual whey from Parmigiano Reggiano cheese-making to obtain ricotta cheese. In addition, vitamin B12 degradation during ricotta cheese shelf-life was studied. The analyses were performed using an ultra performance liquid chromatography-tandem mass spectrometry method. Results show that vitamin B12 amount in ricotta from dairy and experimental cheese-making brings respectively 1/8 to 1/4 of the adequate intake in adults established by EFSA. In addition, shelf-life experiment shows that cobalamine is fairly rapidly degraded in ricotta: light effect seems to be significant, even if the light exposure is short. The use of photoprotective packaging material increases B12 shelf-life in the early stage of storage.

Development of Sandwich Double-Competitive ELISA for Sulfonamides. Comparative Analytical Characteristics and Matrix Effect Resistance

Sandwich enzyme-linked immunosorbent assay (ELISA) of sulfonamides based on double-competitive interaction between haptenized protein as a captured antigen and analyte for binding to immobilized and enzyme-labeled antibodies was developed. This experimental assay format was examined in analytical properties and matrix effect resistance in comparison with usual ones: indirect, direct antigen-coated and antibody-coated ELISAs. All four assay formats were designed on the basis of interactions between the previously prepared monoclonal antibody and immunizing hapten, 4-(4-(4-aminophenylsulfonamido) phenyl)butanoic acid, providing the uniform output optical signal for correct comparison of each assay characteristic. The sensitivity (IC50) of the developed competitive sandwich assay was rather below 100 ng/ml for 11 sulfonamides which was suitable for their determination in milk, muscles and animal sera at established maximum residue limit concentration. Comparative examination did not reveal changes in assay specificity, and advantages in sensitivity, matrix effect resistance, and procedure duration before commonly used assay formats. Moreover, new design of assay was shown to be three-fold more consumable in antibody reagents in comparison with direct assay formats.

Development of a new two‐enzyme biosensor based on poly(pyrrole‐co‐3,4‐ethylenedioxythiophene) for lactose determination in milk

A new lactose biosensor was developed by preparing a suitable copolymer of polypyrrole and poly(3,4‐ethylenedioxythiophene) synthesized using the electropolymerization method. Pyrrole and 3,4‐ethylenedioxythiophene monomers were deposited in the presence of sodium dodecylbenzene sulphonic acid on a platinum disc electrode, which was used as the working electrode. The sensor is based on the serial reactions of β‐galactosidase and galactose oxidase immobilized on a copolymer‐modified platinum disc electrode. Successful synthesis of the enzyme‐immobilized copolymer was confirmed by FT‐IR spectrometry, SEM, and electrochemical analysis. The response of the enzyme electrode to lactose was determined by cyclic voltammetry at + 0.40 V. The response time of the biosensor was found to be from 8 to 10 s, and the upper limit of the linear working portion was found to be at a lactose concentration of 2.30 mM with a detection limit of 1.4 × 10−5 M. The apparent Michaelis–Menten constant was found to be 0.65 mM of lactose. The effects of interferents were also investigated. Lactose concentrations determined by the biosensor were in good agreement with those measured by the reference methods. Our results show that the developed biosensor has a significant potential to the determination of lactose concentration in milk. POLYM. ENG. SCI., 58:839–848, 2018. © 2017 Society of Plastics Engineers

Determination of lactose in milk products: a comparison of three-enzyme amperometric biosensor and gas chromatography/tandem mass spectrometry

Two completely different analytical methods for lactose determination are presented. Three-enzyme biosensor involving β-galactosidase, glucose oxidase, and horseradish peroxidase was constructed with successive steps of optimization. Primary experiments were carried out with horseradish peroxidase biosensor in solution of hydrogen peroxide. Addition of poly(ethylene glycol) diglycidyl ether was examined and the best constant potential for chronoamperometric experiments was selected at −0.05 V using cyclic voltammetry. Ferrocene was chosen as the best from three tested mediators and optimum concentration of ferrocene was found out at 2 g dm−3. Two electrode materials were compared. Spectroscopic graphite electrode proved better electrochemical response for its twice larger electro-active surface than screen-printed carbon electrode. Phosphate buffer solution of pH 7.5, at which the three-enzyme system provided the highest current signal, was used for lactose determination in milk, milk powder, curd cheese, and yogurt. Gas chromatography with tandem mass spectrometric detection was used for determination of lactose, glucose, and galactose in the real samples with internal standard salicine using single ion monitoring mode. Determined content of lactose in the milk products was compared with declared values. Gas chromatography with tandem mass spectrometric detection offers higher sensitivity and orthogonal selectivity in comparison to enzyme biosensor.

Multivariate Optimization Applied to Chromium Determination in Milk and Similar Baby Food Samples by Graphite Furnace Atomic Absorption Spectrometry

Multivariate Optimization Applied to Chromium Determination in Milk and Similar Baby Food Samples by Graphite Furnace Atomic Absorption Spectrometry

Production and Validation of an Alkaline Phosphatase Reference Material in Lyophilized Milk

The paper describes the characterization and evaluation of a reference material in lyophilized milk to be used for the determination of alkaline phosphatase with the reference method ISO 11816-1:2013. The reference material was produced at three levels of activity, calibrated for the determination of alkaline phosphatase activity in pasteurized (sample “60”), thermized (sample “600”), and raw milk (sample “6000”). The first assignment of the title and the uncertainties were realized through a round of 18 Italian laboratories and the EUR-MMP in 2014. In 2015, a second round was repeated with the participation of 17 expert laboratories of the net of NRLs-MMP. The first titles were confirmed, whereas the second trial succeeded in a good improvement of the final uncertainties (sample “60” = 96.10 ± 2.03; sample “600” = 775.91 ± 13.03; sample “6000” = 6040.65 ± 126.89 mU/L). The materials were fully characterized according to ISO Guide 35:2006 and proved to be highly crono and temperature stable, so these are excellent candidates to be used for internal instrumental quality control or for the organization of interlaboratory trials for alkaline phosphatase determination in milk.