The challenges of ractopamine use in meat production for export to European Union and Russia

Magnetic solid-phase extraction based on restricted-access molecularly imprinted polymers for ultrarapid determination of ractopamine residues from food samples by capillary electrophoresis

An ultrafast, efficient, and eco-friendly method combining magnetic solid phase extraction and capillary electrophoresis with diode array detection have been developed to determine ractopamine residues in food samples. A restricted access material based on magnetic and mesoporous molecularly imprinted polymer has been properly synthesized and characterized, demonstrating excellent selectivity and high adsorbent capacity. Short-end injection capillary electrophoresis method was optimized: 75 mM triethylamine pH 7 as BGE, -20 kV, 50 mbar by hydrodynamic injection during 8 s, and capillary temperature at 25 °C; reaching ultrafast ractopamine analysis (∼0.6 min) with good peak asymmetry, and free from interfering and/or baseline noise. After sample preparation optimization, the conditions were: 1000 µL of sample at pH 6, 20 mg of adsorbent, stirring time of 120 s, 250 µL of ultrapure water as washing solvent, 1000 µL of methanol: acetic acid (7: 3, v/v) as eluent, and the adsorbent can be reused four times. In these conditions, the analytical method showed recoveries around to 100 %, linearity ranged from 9.74 to 974.0 µg kg-1, correlation coefficient (r) ≥ 0,99 in addition to adequate precision, accuracy, and robustness. After proper validation, the method was successfully applied in the analysis ractopamine residues in bovine milk and bovine and porcine muscle.

Nanomolar electrochemical detection of feed additive ractopamine in meat samples using spinel zinc ferrite decorated 3-dimensional graphene nanosheets to combat food fraud in livestock industries

Accurate detection of feed additive is significant for food safety monitoring, warding off its illegal use in livestock production, safeguarding public health, and regulatory compliance. Hence, this paper presents a cost-effective and ultrasensitive electrochemical sensor for detecting commonly used animal feed additive, ractopamine to combat food frauds in meat samples. The sensor was created by embedding spinel zinc ferrite nanospheres (ZnFe2O4) on three-dimensional graphene (3DG) nanosheets using sonochemical method. ZnFe2O4 nanospheres were synthesized using solvothermal approach, and 3DG was prepared using hydrothermal method. Various characterization techniques were used for inspecting structural and morphological properties of materials, including XRD, SEM, TEM, elemental mapping, Raman spectroscopy, XPS, and EIS. The hybrid nanocomposite modified electrode showed excellent electrochemical performance, with high sensitivity of 16.97 μA μM-1 cm-2 and detection limit of 1 nM. The practicality of sensor was demonstrated by performing real sample analysis in pork, beef, and sausage which gave adequate recovery.

Comparison of immunoassay and LC-tandem mass spectrometry analyses of ractopamine in hog oral fluid

The accurate detection of ractopamine in food animals is crucial for marketing since some entities require animals or animal carcasses to be free of ractopamine residues. Field-based ractopamine screening tests that are rapid, sensitive, and capable of high-throughput are highly desirable to ensure that inadvertent exposure to ractopamine did not occur in animals marketed as animals that have not been fed ractopamine. An immunochemically based lateral flow assay was used to analyze oral fluids from hogs never exposed to ractopamine and from hogs that were presumed positives and results were confirmed using an enhanced sensitivity LC-MSMS method. We found that an immunochemically based lateral flow system having a working range of 2.5 to 15 ng mL-1 worked well as a screening assay with 1.7% false positive results in freshly collected hog oral fluids. Using ractopamine glucuronide standards and LC-MSMS, we determined that the false positive results were not due to the presence of ractopamine glucuronide metabolites in oral fluids.

The Effects of Different Zilpaterol Hydrochloride Feed Supplements and Extended Aging Periods on the Meat Quality of Feedlot Bulls

This study researched the effects of two commercially available zilpaterol hydrochloride (ZH) β-adrenergic agonists, denoted as ZH-A and ZH-B, on the meat quality characteristics of typical South African feedlot bulls (taurine × indicus composites), over extended aging periods of up to 120 days. The effects of ZH were studied to address concerns about the possible adverse effects of ZH on beef quality following extended aging, which typically occurs during the exportation of beef by boat. The completely randomized control study consisted of 3 homogenous experimental groups, with 3 replicates per treatment and 50 bulls per replicate = 450 animals. Treatments were a negative control (CT) with no ZH supplementation added to the basal diet or a basal diet supplemented with either zilpaterol hydrochloride A (ZH-A) or zilpaterol hydrochloride B (ZH-B), both at 105 g ZH/ton, fed from the first day of the finishing period (D0) for 30 days. Subsamples were collected from 38 random carcasses from each treatment for proximate analysis and meat quality analysis using Longissimus dorsi samples. ZH supplementation decreased meat tenderness (Warner-Bratzler shear force values (WBSF)) of bulls fed ZH-A or ZH-B, compared to those fed the CT diet (p < 0.05; η2 = 0.24). The WBSF values of both ZH treatments were about 0.5-0.8 kg higher during the aging periods compared to the CT, but ZH did not affect post-mortem meat aging or meat quality characteristics differently compared to the CT. Post-mortem aging per se influenced all meat quality characteristics investigated (p < 0.001; η2 > 0.30), showing improvements in WBSF, a decrease in meat colour and an increase in drip and cooking losses. L*-values increased from 3 to 56 days of aging and then decreased to day 120 (p < 0.001; η2 = 032). Chroma values decreased from day 3 to day 120 (p < 0.001; η2 = 0.50). Hue° decreased from day 3 to day 7 and stabilized until day 120 (p < 0.001; η2 = 0.40). Moisture and cooking loss (CL) increased to 56 days and then decreased to 120 days.

Advance in Detection Technique of Lean Meat Powder Residues in Meat Using SERS: A Review

Food that contains lean meat powder (LMP) can cause human health issues, such as nausea, headaches, and even death for consumers. Traditional methods for detecting LMP residues in meat are often time-consuming and complex and lack sensitivity. This article provides a review of the research progress on the use of surface-enhanced Raman spectroscopy (SERS) technology for detecting residues of LMP in meat. The review also discusses several applications of SERS technology for detecting residues of LMP in meat, including the enhanced detection of LMP residues in meat based on single metal nanoparticles, combining metal nanoparticles with adsorbent materials, combining metal nanoparticles with immunizing and other chemicals, and combining the SERS technology with related techniques. As SERS technology continues to develop and improve, it is expected to become an even more widely used and effective tool for detecting residues of LMP in meat.

Multifunctional one-droplet microfluidic chemosensing of ractopamine in real samples: a user-oriented flexible nano-architecture for on-site food and pharmaceutical analysis using optical sensors

Illegal use of ractopamine (RAC) in the food industry has dire consequences for health which should be curbed by inexpensive on-site checks. In this study, four advanced nanostructures of AuNPs were examined for this purpose. For the first time, a novel cost-effective colorimetric opto-sensor based on gold nanoparticles in aqueous solution was developed and successfully utilized for the recognition of RAC in real samples. The colorimetric chemosensor based on AuNPs-CysA exhibited a linear range of 0.1 μM to 0.01 M with a limit of detection (LOD) of 0.001 μM. Also, using AuNPs-DDT as a photonic probe two ranges of linearity of 0.01 to 50 μM and 0.005 to 0.01 M were obtained (LOD = 1 nM). The outstanding features of the utilized nanostructures are the simple preparation, the suitable stability of AuNPs-CysA and the excellent selectivity of AuNPs-DDT toward RAC recognition. Finally, the engineered colorimetric systems were combined with a simple and inexpensive optimized microfluidic glass fiber-based device. This work paves the way for devising inexpensive and efficient on-site recognition devices for food safety checks.

Productive Performance, Physiological Variables, and Carcass Quality of Finishing Pigs Supplemented with Ferulic Acid and Grape Pomace under Heat Stress Conditions

The effect of individual and combined supplementation of FA and GPM on physiological variables, productive performance, and carcass characteristics of finishing pigs under heat stress conditions were investigated. Forty Yorkshire × Duroc pigs (80.23 kg) were individually housed and randomly distributed into 4 groups under a 2 × 2 factorial arrangement (n = 10): Control (basal diet, BD); FA, BD + 25 mg FA; GPM, BD with 2.5% GPM; and MIX, BD with 25 mg FA and 2.5% GPM. Additives were supplemented for 31 days. The inclusion of FA or GPM did not modify rectal temperature and respiratory rate. There was an effect of the interaction on FI, which increased when only GPM was supplemented, with respect to Control and MIX (p < 0.05). Average daily gain (ADG) and feed conversion (FC) were not affected by treatments (p > 0.05). The inclusion of FA improved hot and cold carcass weight, while the addition of GPM decreased the marbling (p < 0.05) and tended to increase loin area (p < 0.10). GPM increased liver weight (p < 0.05). The addition of GPM and FA can improve some carcass characteristics under heat stress conditions. It is necessary to continue investigating different levels of inclusion of GPM and FA in finishing pigs' diets.

Development of novel isothermal-based DNA amplification assay for detection of pig tissues in adulterated meat

For the first time, we describe an innovative polymerase spiral reaction (PSR) assay for the rapid, simple, and accurate detection of pig tissues or pork in adulterated meat including heat-treated and processed ones. The PSR assay specifically targeting the mitochondrial cytochrome b (cyt-b) gene of the pig was successfully optimized permitting assay results in 65 min time. The developed detection method was 100% specific amplifying only the cyt-b gene and displaying negative results with all the tested non-pork meats. The sensitivity of the developed PSR (760 fg porcine DNA) was tenfold better than the end-point PCR and able to detect heat-treated (121 °C) and adulterated (0.5% pork in beef) meat and processed pork products such as sausages, salami, meatball, soup, curry, etc. The developed PSR-based method can be used for point-of-care detection with minimum instrumentation and technical expertise to guarantee instant clearance of exported and imported meat products. This is the first time that PSR has been adapted for food authenticity purposes.

Current Analytical Methods and Research Trends Are Used to Identify Domestic Pig and Wild Boar DNA in Meat and Meat Products

The pig, one of the most important livestock species, is a meaningful source of global meat production. It is necessary, however, to prove whether a food product that a discerning customer selects in a store is actually made from pork or venison, or does not contain it at all. The problem of food authenticity is widespread worldwide, and cases of meat adulteration have accelerated the development of food and the identification methods of feed species. It is worth noting that several different molecular biology techniques can identify a porcine component. However, the precise differentiation between wild boar and a domestic pig in meat products is still challenging. This paper presents the current state of knowledge concerning the species identification of the domestic pig and wild boar DNA in meat and its products.

Ractopamine at the Center of Decades-Long Scientific and Legal Disputes: A Lesson on Benefits, Safety Issues, and Conflicts

Ractopamine (RAC) is a synthetic phenethanolamine, β–adrenergic agonist used as a feed additive to develop leanness and increase feed conversion efficiency in different farm animals. While RAC has been authorized as a feed additive for pigs and cattle in a limited number of countries, a great majority of jurisdictions, including the European Union (EU), China, Russia, and Taiwan, have banned its use on safety grounds. RAC has been under long scientific and political discussion as a controversial antibiotic as a feed additive. Here, we will present significant information on RAC regarding its application, detection methods, conflicts, and legal divisions that play a major role in controversial deadlock and why this issue warrants the attention of scientists, agriculturists, environmentalists, and health advocates. In this review, we highlight the potential toxicities of RAC on aquatic animals to emphasize scientific evidence and reports on the potentially harmful effects of RAC on the aquatic environment and human health.

A portable colorimetric chemosensing regime for ractopamine in chicken samples using μPCD decorated by silver nanoprisms

In recent years the use of ractopamine (RAC), originally synthesized for the treatment of respiratory diseases, is on the rise as a dietary supplement in animals. The excessive use of RAC has some adverse effects on human health. Hence, the demand for simple, easy-to-use, and expendable devices for RAC recognition, even in remote areas, is felt more than ever before. This need prompted us to devise a straightforward colorimetric system for RAC recognition based on the etching effect of RAC on AgNPrs. This nanoprobe is a very advanced materials with great optical properties and stability, which could be used unprecedentedly without any combination or reagents for RAC recognition. Considering the needs and advantages, a simple colorimetric chemosensor for the quantification of RAC was designed and applied to a chicken sample. The designed chemosensor was integrated with an optimized microfluidic paper-based colorimetric device (μPCD), creating a suitable tool for the determination of RAC based on a time/color pattern. The analytical metrics for this simple colorimetric chemosensing regime comprise a best colorimetric LLOQ of 100 μM in solution with 10 μM of μPCD, a spectroscopic LLOQ of 10 nM, and a broad linearity range of 0.1-10 000 μM, which are outstanding compared with other colorimetric techniques. The main remarkable features of this study include the first utilization of AgNPrs with high stability and excellent optical properties without any reagent as an optical sensing probe and optimized μPCD toward RAC recognition and the innovative time/color semi-analytical recognition method. Moreover, the prepared portable μPCD modified with AgNPrs could be a prized candidate for commercialization due to the benefits of the low-cost materials used, like paper and paraffin, and the simple instructions for μPCD preparation. This report could be a pioneering work, inspiring simple and effective on-site semi-analytical recognition devices for harmful substances or illegal drugs, which simply consist of a piece of lightweight paper and one drop of the required reagent.

Determination of the Metabolites and Metabolic Pathways for Three β-Receptor Agonists in Rats Based on LC-MS/MS

This paper developed a universal detection method by high-performance liquid chromatography-tandem mass spectrometry to detect three typical clenbuterols, CLB, SAL, and RAC, and to investigate the metabolism of β-agonists in vivo. The parent ions and daughter ions of the three β-receptor agonist standards and the residues in the muscle, liver, and blood samples of rats were obtained by Total Ions Scan mode. The metabolites produced in different tissues at a specific time were qualitatively and quantitatively analyzed, and the corresponding metabolic pathways were inferred. The results showed that the three β-receptor agonists mainly existed in the form of prototype drugs in rats, with a small amount of clenbuterol methyl compound and albuterol methyl compound. There were significant differences in residual metabolism between different tissues of the same species. In addition, different β-receptor agonists have different absorption and utilization rates in rats.

Improving Genomic Selection for Heat Tolerance in Dairy Cattle: Current Opportunities and Future Directions

Heat tolerance is the ability of an animal to maintain production and reproduction levels under hot and humid conditions and is now a trait of economic relevance in dairy systems worldwide because of an escalating warming climate. The Australian dairy population is one of the excellent study models for enhancing our understanding of the biology of heat tolerance because they are predominantly kept outdoors on pastures where they experience direct effects of weather elements (e.g., solar radiation). In this article, we focus on evidence from recent studies in Australia that leveraged large a dataset [∼40,000 animals with phenotypes and 15 million whole-genome sequence variants] to elucidate the genetic basis of thermal stress as a critical part of the strategy to breed cattle adapted to warmer environments. Genotype-by-environment interaction (i.e., G × E) due to temperature and humidity variation is increasing, meaning animals are becoming less adapted (i.e., more sensitive) to changing environments. There are opportunities to reverse this trend and accelerate adaptation to warming climate by 1) selecting robust or heat-resilient animals and 2) including resilience indicators in breeding goals. Candidate causal variants related to the nervous system and metabolic functions are relevant for heat tolerance and, therefore, key for improving this trait. This could include adding these variants in the custom SNP panels used for routine genomic evaluations or as the basis to design specific agonist or antagonist compounds for lowering core body temperature under heat stress conditions. Indeed, it was encouraging to see that adding prioritized functionally relevant variants into the 50k SNP panel (i.e., the industry panel used for genomic evaluation in Australia) increased the prediction accuracy of heat tolerance by up to 10% units. This gain in accuracy is critical because genetic improvement has a linear relationship with prediction accuracy. Overall, while this article used data mainly from Australia, this could benefit other countries that aim to develop breeding values for heat tolerance, considering that the warming climate is becoming a topical issue worldwide.

Sensitive recognition of ractopamine using GQDs-DPA as organic fluorescent probe

A novel spectrofluorimetric sensing platform was designed for Ractopamine measurement in aqueous and plasma samples. d-penicillamine functionalized graphene quantum dots (DPA-GQDs) was utilized as a fluorescence probe, which was synthesized through the pyrolysis of citric acid in the presence of DPA. This one-pot down-top strategy causes to high-yield controllable synthesis method. The reaction time and probe concentration were optimized. Then, the fluorescence intensity of aqueous samples containing different Ractopamine concentrations and 500 ppm DPA-GQDs were measured at 25°C with an excitation wavelength of 274 nm. The sensing platform was also applied to detect Ractopamine in untreated plasma samples. The fluorescence spectroscopy technique responses indicated a linear relationship between the peak fluorescence intensity and ractopamine concentration in the range of 0.25-15 ppm with low limit of quantification of 0.25 ppm was for aqueous and plasma samples, respectively.

Ractopamine and Other Growth-Promoting Compounds in Beef Cattle Operations: Fate and Transport in Feedlot Pens and Adjacent Environments

The current study represents a comprehensive investigation of the occurrence and fates of trenbolone acetate (TBA) and metabolites 17α-trenbolone (17α-TBOH), 17β-TBOH, and trendione (TBO); melengesterol acetate (MGA); and the less commonly studied β-andrenergic agonist ractopamine (RAC) in two 8 month cattle feeding trials and simulated rainfall runoff experiments. Cattle were administered TBA, MGA, or RAC, and their residues were measured in fresh feces, pen floor material, and simulated rainfall runoff from pen floor surfaces and manure-amended pasture. Concentrations of RAC ranged from 3600 ng g^-1, dry weight (dw), in pen floor to 58 000 ng g^-1 in fresh feces and were, on average, observed at 3-4 orders of magnitude greater than those of TBA and MGA. RAC persisted in pen floors (manure t_1/2 = 18-49 days), and contamination of adjacent sites was observed, likely via transport of windblown particulates. Concentrations in runoff water from pen floors extrapolated to larger-scale commercial feedlots revealed that a single rainfall event could result in mobilization of gram quantities of RAC. This is the first report of RAC occurrence and fate in cattle feedlot environments, and will help understand the risks posed by this chemical and inform appropriate manure-management practices.

Preparation of Magnetic Molecularly Imprinted Polymers for Selective Recognition and Determination of Clenbuterol in Pork Samples

Magnetic molecularly imprinted polymer (MMIP) was successfully synthesized with acrylamide as a functional monomer and clenbuterol (CLB) as a template molecule. The synthesized MMIPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectrometry (FT-IR). MMIPs were used to identify and bind CLB as a solid phase extraction material. The experiment data were fitted by the Freundlich isotherm adsorption model. The results show that MMIPs have excellent recognition performance for CLB. MMIPs were successfully applied as adsorbents to preconcentrated CLB in pork samples and detected by HPLC with UV. The limit of detection (LOD) and limit of quantification (LOQ) were 4.27 μg/L and 14.2 μg/L, respectively. The spiked recovery rates ranged from 94.44% to 102.29%. Therefore, the prepared MMIPs can be used for selective preconcentration of CLB content in complex animal-derived food samples.

Ultrasensitive determination of ractopamine based on dual catalytic signal amplification by Pd nanocubes and HRP using a flow injection chemiluminescence immunoassay

A rapid and highly sensitive flow injection chemiluminescence immunoassay was developed to detect ractopamine residues in pork products. Palladium nanocubes with excellent catalytic performance for a traditional luminol-PIP-H2O2 chemiluminescence system were used as effective carriers to connect a ractopamine antibody and horseradish peroxidase (HRP). Double amplification of a chemiluminescence signal was realized because of palladium nanocubes and HRP. Carboxyl-modified resin beads were used as suitable materials to load ractopamine-coating antigens due to their good biocompatibility and large specific surface area. Based on the principle of competitive immunity, ractopamine standard solution would compete with antigen loaded on carboxyl resin beads for limited binding sites on a ractopamine antibody. Thus, the chemiluminescence intensity of an immunosensor has a linear negative correlation with the logarithm value of ractopamine concentration. Under optimal experimental conditions, the detection range of ractopamine was 0.005-1000 ng mL-1, and the limit of detection (LOD) was 1.7 pg mL-1 (S/N = 3). The proposed immunoassay possessed acceptable accuracy, high specificity and reproducibility and RAC was examined in pork and pig feed with satisfactory results, which would provide a better prospect for the detection of small molecules in food and environment analysis.

Detection of porcine-derived ingredients from adulterated meat based on real-time loop-mediated isothermal amplification

Increasingly globalized and complex food supply chains contribute to a growing problem of meat fraud. Meat adulteration with pork is especially exceptionable to the global population for health concern and religious faith reasons. To prevent unfair competition and protect consumer rights, an efficient and rapid assay to identify the species of meat products is crucial. In this study, a real-time loop-mediated isothermal amplification (real-time LAMP) assay was developed for the detection of a porcine gene in meat products. The designed primers were highly selective for the porcine gene. The amplification showed no cross-reactivity with 11 other meats. The established method required 20 min with an initial amplification curve of approximately 10 min and demonstrated a detection limit of 1.76 pg/μL porcine DNA, which is 1000 times more sensitive than PCR. This study is the first attempt at detecting porcine-derived ingredients using a real-time LAMP assay in commercial products. This method meets specificity, rapidness, robustness, and sensitivity criteria; its practical application will greatly aid in battling adulteration in the food industry.

Ultramarine blue nanoparticles as a label for immunochromatographic on-site determination of ractopamine

A competitive immunochromatographic assay (ICA) is presented and used for on-site determination of ractopamine (RAC). Ultramarine blue nanoparticles were directly separated from ultramarine blue industrial products by centrifugation (< 10,000 rpm and > 4000 rpm) and used as visible labels in ICAs. The ultramarine blue nanoparticles were coated by polyacrylic acid (PAA), which provides carboxyl groups on the surface of ultramarine blue nanoparticles. An anti-RAC monoclonal antibody (mAb) was covalently immobilized on the carboxyl-modified ultramarine blue nanoparticle surface via diimide-activated conjugation between the carboxyl groups on the ultramarine blue nanoparticle surface and the amino groups of the antibodies. RAC and BSA-modified RAC competitively bind to the anti-RAC mAb on the ultramarine blue nanoparticles. The blue band in the test line is generated by the accumulation of ultramarine blue nanoparticles and is negatively associated with the RAC content. Under optimal conditions, the visual limit of detection (vLOD) of this ICA for RAC is 2.0 ng mL^-1, 2.0 ng mL^-1, and 1.0 ng mL^-1 in phosphate-buffered saline (PBS), feed samples, and pork samples, respectively. The ultramarine blue nanoparticle-based ICA also shows no cross activity with salbutamol, clorprenaline, clenbuterol, or terbutaline. Graphical abstract Schematic representation of the ultramarine blue nanoparticles immunochromatographic assay for detection of ractopamine (RAC) based on competitive method. The ultramarine blue nanoparticles were screened from commercial ultramarine pigments for the first time and used to detect ractopamine.

Sensitive and Matrix-Tolerant Lateral Flow Immunoassay Based on Fluorescent Magnetic Nanobeads for the Detection of Clenbuterol in Swine Urine

The lack of sensitivity and poor matrix tolerance are the main bottlenecks of the lateral flow immunoassay (LFIA). Here, a sensitive and matrix-tolerant method that integrated immunomagnetic separation and fluorescent lateral flow immunoassay (IMS-FLFIA) based on fluorescent magnetic nanobeads was developed to detect the clenbuterol (CLE) residue in swine urine. The limit of detection (LOD) of IMS-FLFIA is 4 times lower than that of traditional colloidal gold LFIA. This method, which exhibits similar LOD and linearity range in both phosphate-buffered saline and urine swine, is highly correlated with liquid chromatography-tandem mass spectrometry for the detection of real swine urine samples. The result indicated that IMS-FLFIA has a universal resistance to the swine urine matrix. The merits of this assay, high sensitivity, matrix tolerance, accuracy, and specificity, ensure a promising future in detection of veterinary drug residues.

Novel ractopamine-protein carrier conjugation and its application to the lateral flow strip test for ractopamine detection in animal feed

In this work, a novel conjugate of ractopamine and bovine serum albumin (RAC-BSA) has been developed via the Mannich reaction, with a mole coupling ratio for RAC-BSA of 9:1. The proposed conjugation method provides a simple and one-step method with the use of fewer reagents compared with other conjugation methods for competitive immunoassays. RAC-BSA conjugation was used to fabricate a competitive lateral flow strip test for RAC detection in animal feed. For sample preparation, RAC was spiked in swine feed purchased from the local markets in Thailand, and methanol and running buffer at a volume ratio of 10:90 was used as extraction buffer. The procedures for sample preparation were completed within 25 min. Under optimal conditions, the limit of detection (LOD), assessed by the naked eye within 5 min, was found to be 1 ng/g. A semi-quantitative analysis was also conducted using a smart phone and computer software, with a linearity of 0.075-0.750 ng/g, calculated LOD of 0.10 ng/g, calculated limit of quantitation of 0.33 ng/g, and good correlation of 0.992. The recoveries were found in the range of 96.4%-103.7% with a relative standard deviation of 2.5%-3.6% for intra- and inter-assays. Comparison of the results obtained by the strip test with those obtained by enzyme-linked immunosorbent assay had a good agreement in terms of accuracy. Furthermore, this strip test exhibited highly specific RAC detection without cross reactivity with related compounds. Therefore, the RAC-BSA conjugation via the Mannich reaction can be accepted as a one-step and easy conjugation method and applied to the competitive lateral flow strip test.

Colorimetric detection of the β-agonist ractopamine in animal feed, tissue and urine samples using gold-silver alloy nanoparticles modified with sulfanilic acid

A highly sensitive, selective and simple method was proposed for colorimetric detection of ractopamine on the basis of the interaction between ractopamine and sulfanilic acid-modified gold-silver alloy nanoparticles (AuAgNPs). The AuAgNPs were prepared by the reduction of HAuCl₄ and AgNO₃ with sodium citrate in aqueous medium and further modified by sulfanilic acid. The interaction of ractopamine with sulfanilic acid induced rapid aggregation of sulfanilic acid-modified AuAgNPs along with an optical colour change, leading to precise quantification which could be detected by absorptiometry. Under the optimum conditions, the absorbance ratio (A₆₀₀/A₄₃₅) of sulfanilic acid-modified AuAgNPs exhibited a linear relationship with the concentration of ractopamine in the range of 4.5-31.6 ng/mL. The detection limit of ractopamine was 1.5 ng/mL. The established novel colorimetric detection method showed high selectivity towards ractopamine. The method was successfully applied to detect ractopamine in spiked pork, swine feed and swine urine samples with excellent recoveries from 94.4% to 112.5%. These results demonstrated that the proposed new method has a good potential for practical applications.

Application of Enzyme Digestion and Deconjugation Followed by Quick, Easy, Cheap, Effective, Rugged, Safe Extraction and Liquid Chromatography-Tandem Mass Spectrometry Methodology To Determine Ractopamine Residue in Pork

A new methodology is proposed for ractopamine residue analysis in pork. It consists of enzyme-mediated digestion and deconjugation steps; modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction; and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In brief, the samples were digested with protease and then deconjugated with β-glucuronidase enzyme; they were then subjected to extraction and cleanup by QuEChERS and underwent sequential analysis by LC-MS/MS. The method performance was evaluated in accordance to the validation guidelines regulated by the Brazilian Ministry of Agriculture and Food Supply. The limit of detection was 0.15 μg/kg and limit of quantification was 0.5 μg/kg. When the method was applied to real samples, ractopamine residue was found in concentrations (up to 7.86 μg/kg) below international recommendation limits up to 10 μg/kg. The method is sensitive, accurate, quick, simple, and suitable for routine analysis; therefore, it is a monitoring tool that may be adopted by laboratories to achieve compliance levels.

Reproducible Molecularly Imprinted Piezoelectric Sensor for Accurate and Sensitive Detection of Ractopamine in Swine and Feed Products

This paper describes the development of a reproducible molecularly imprinted piezoelectric sensor for the accurate and sensitive detection of ractopamine (RAC) in swine and feed products. The synthesized molecularly imprinted polymer (MIP) was directly immobilized on the surface of a quartz crystal microbalance (QCM) Au chip as the recognition element. The experimental parameters in the fabrication, measurement and regeneration process were evaluated in detail to produce an MIP-based piezoelectric sensor with high sensing capability. The developed piezoelectric sensor was verified to perform favorably in the RAC analysis of swine and feed products, with acceptable accuracy (recovery: 75.9⁻93.3%), precision [relative standard deviation (n = 3): 2.3⁻6.4%], and sensitivity [limit of detection: 0.46 ng g-1 (swine) and 0.38 ng g-1 (feed)]. This portable MIP-based chip for the piezoelectric sensing of RAC could be reused for at least 30 cycles and easily stored for a long time. These results demonstrated that the developed MIP-based piezoelectric sensor presents an accurate, sensitive and cost-effective method for the quantitative detection of RAC in complex samples. This research offers a promising strategy for the development of novel effective devices used for use in food safety analysis.