Metabolic characterization of 25X-NBOH and 25X-NBOMe phenethylamines based on UHPLC-Q-Exactive Orbitrap MS in human liver microsomes.

The types and quantities of new psychoactive substances synthesized based on structural modifications have increased rapidly in recent years and pose a great challenge to clinical and forensic laboratories. N-benzyl derivatives of phenethylamines, 25B-NBOH, 25E-NBOH, 25H-NBOH, and 25iP-NBOMe have begun to flow into the black market and have caused several poisoning cases and even fatal cases. The aim of this study was to avoid false negative results by detecting the parent drug and its metabolites to extend the detection window in biological matrices and provide basic data for the simultaneous determination of illegal drugs and metabolites in forensic and emergency cases. To facilitate the comparison of metabolic characteristics, we divided the four compounds into two groups of types, 25X-NBOH and 25X-NBOMe. The in vitro phase I and phase II metabolism of these four compounds was investigated by incubating 10 mg mL-1 pooled human liver microsomes with co-substrates for 180 min at 37 â„ƒ, and then analyzing the reaction mixture using ultrahigh-performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry. In total, 70 metabolites were obtained for the four compounds. The major biotransformations were O-demethylation, hydroxylation, dehydrogenation, N-dehydroxybenzyl, N-demethoxybenzyl, oxidate transformation to ketone and carboxylate, glucuronidation, and their combination reactions. We recommended the major metabolites with high peak area ratio as biomarkers, B2-1 (56.61%), B2-2 (17.43%) and B6 (17.78%) for 25B-NBOH, E2-1 (42.81%), E2-2 (34.90%) and E8-2 (10.18%) for 25E-NBOH, H5 (49.28%), H2-1 (21.54%), and H1 (18.37%) for 25H-NBOH, P3-1 (10.94%), P3-2 (33.18%), P3-3 (14.85%) and P12-2 (23.00%) for 25iP-NBOMe. This is a study to evaluate their metabolic characteristics in detail. Comparative analysis of the N-benzyl derivatives of phenethylamines provided basic data for elucidating their pharmacology and toxicity. Timely analysis of the metabolic profiles of compounds with abuse potential will facilitate the early development of regulatory measures.

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.

Development of a lateral flow immunoassays-based method for the screening of ractopamine in foods and evaluation of the optimal strategy in combination of screening and confirmatory tests.

Ractopamine has been authorized as a feed additive and permitted in animal husbandry. With the establishment of the regulation to limit the concentration of ractopamine, a rapid screening method for ractopamine is urgently needed. Additionally, how to combine the screening and confirmatory tests of ractopamine is also critical to maximizing the efficiency of testing. Here, we developed a lateral flow immunoassays-based method for the screening of ractopamine in foods and proposed a cost-benefit analysis approach to optimize cost allocation between screening and confirmatory tests. After verifying the analytical and clinical performances of the screening method, a mathematical model was established to calculate the screening and confirmatory test results with various parameter settings, such as cost allocation, false-negative tolerance, and total budget size. The developed immunoassay-based screening test could successfully distinguish gravy samples with ractopamine levels over and lower than maximum residue limits (MRL). The area under curve (AUC) value of receiver operating characteristic (ROC) curve is 0.99. For the cost-benefit analysis, mathematical simulation indicated that when the samples are allocated to screening and confirmatory tests at the optimized cost allocation, the number of confirmed positive samples can increase by 26 times compared to the scenarios entirely relying on confirmatory testing. While conventional wisdom considers that screening should be carried out at low false-negative rates, such as 0.1%, our results indicated that the cutoff value of a screening test with a 20% false-negative rate at MRL could capture the maximum number of confirmed positive samples at a limited budget. Our work indicated that the participation of the screening method in ractopamine analysis and optimized cost allocation between screening and confirmatory tests could enhance the efficiency in detecting the positive samples, which provides a rational basis for decision-making in food safety enforcement for public health.

A UPLC-MS/MS methodological approach for the analysis of 75 phenethylamines and their derivatives in hair.

A rapid ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the targeted analysis of 75 phenethylamines and their derivatives from the hair matrix. The monitored classes of phenethylamines included the 2C series, D series, N-benzyl derivatives, mescaline-derived compounds, MDMA analogs, and benzodifurans. Approximately 20 mg of hair was weighed and pulverized with 0.1% formic acid in methanol by cryogenic grinding. After ultrasonication, centrifugation, and filtration, the supernatant was analyzed by LC-MS/MS operating in the scheduled multiple reaction monitoring mode. Phenethylamines and their derivatives were separated in 13 min on a biphenyl column (2.6 µm, 100 Å, 100 × 3.0 mm) using a gradient eluting mobile phase composed of 0.1% formic acid in water and acetonitrile. The developed and validated method showed good selectivity, sensitivity (LOD: 0.5-10 pg/mg and LOQ: 1-20 pg/mg), linearity (R2 > 0.997), accuracy and precision (< 20%), and stability. The method also showed good recovery and acceptable matrix effects for most of the targeted compounds. This analytical approach was successfully applied for the identification and quantification of phenethylamines in hair from authentic forensic cases.

Analysis of 2,5-dimethoxy-amphetamines and 2,5-dimethoxy-phenethylamines aiming their determination in biological matrices: a review.

PURPOSE: The present review aims to provide an overview of methods for the quantification of 2,5-dimethoxy-amphetamines and -phenethylamines in different biological matrices, both traditional and alternative ones. METHODS: A complete literature search was carried out with PubMed, Scopus and the World Wide Web using relevant keywords, e.g., designer drugs, amphetamines, phenethylamines, and biological matrices. RESULTS: Synthetic phenethylamines represent one of the largest classes of "designer drugs", obtained through chemical structure modifications of psychoactive substances to increase their pharmacological activities. This practice is also favored by the fact that every new synthetic compound is not considered illegal by existing legislation. Generally, in a toxicological laboratory, the first monitoring of drugs of abuse is made by rapid screening tests that sometimes can occur in false positive or false negative results. To reduce evaluation errors, it is mandatory to submit the positive samples to confirmatory methods, such as gas chromatography or liquid chromatography combined to mass spectrometry, for a more specific qualitative and quantitative analysis. CONCLUSIONS: This review highlights the great need for updated comprehensive analytical methods, particularly when analyzing biological matrices, both traditional and alternative ones, for the search of newly emerging designer drugs.

Presence of ß2 -agonist growth promoters in human urine samples: GC-MS/MS evaluation of the excretion profiles of ractopamine administered in microdoses.

ß2 -adrenergic agonists having the potential to be misused to enhance performance for their thermogenic and anabolic properties are prohibited in sports. Clenbuterol, ractopamine and zilpaterol are utilised legally or illegally as growth promoters of animals raised for their meat. No withdrawal times are imposed for ractopamine prior to slaughter; residues are detected in meat of treated animals, which constitutes a risk of inadvertent consumption. Insufficient information is available on the fate of ractopamine in humans to implement efficient detection in athletes' urine samples. We have developed a confirmation procedure for total ractopamine in urine following the enzymatic hydrolysis of glucuronides and sulphates and the conversion to tri-TMS derivative (limit of identification at 0.15 ng/ml). The sulphates were found to form between 85% to 97% of ractopamine excreted in athletes' urine samples analysed routinely or in volunteers following the administration of a micro-dose of 2.5 µg. Peak levels were reached at 2 to 6 h and decreased rapidly below 1 ng/ml 10 h after dosing. With one exception, the highest level estimated in athletes' samples was 1.2 ng/ml. Zilpaterol was confirmed in a few urine samples collected in the USA and Mexico (highest level 2 ng/ml), while hundreds of athletes' samples were reported to contain clenbuterol by our laboratory over the past 7 years. Most of these cases originated from Mexico (n = 102) and Guatemala (n = 119), often clustered in events during which multiple samples were collected, and for the vast majority, in levels lower than 0.2 ng/ml.

Simultaneous quantification of 106 drugs or their metabolites in nail samples by UPLC-MS/MS with high-throughput sample preparation: Application to 294 real cases.

The nail is an alternative matrix to complement hair analysis in proving drug intake over several months in forensic toxicology investigations. However, because of the high hardness and toughness of nails, the existing pretreatment procedures for nails have the disadvantages of either a high degree of time consumption (from hours to days), or low extraction recoveries. This study aims to propose a high-throughput nail sample preparation method and provide a quantitative analytical method for 106 drugs and their metabolites present in nail. We developed cryogenic grinding, coupled with high-speed grinding in the extraction solvent method, which could improve the extraction recovery by thoroughly destroying the nail keratin for approximately 18 min. Subsequently, an ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for the identification and quantification of 34 synthetic cannabinoids, 26 fentanyls, 18 synthetic cathinones, 10 phenylethylamines, eight opioids, three phencyclidine, two tryptamines, two piperazine, cocaine, benzoylecgonine, and tetrahydrocannabinol (THC). Nail samples were collected from people with a history of drug abuse from five different regions of China. The analysis of 294 authentic samples resulted in 213 detected samples, and showed a broad concentration range including 5.04-67.26 pg/mg for nine synthetic cannabinoids, 109.29-250.29 pg/mg for a synthetic cathinone, 5.06-434291 pg/mg for four phenylethylamines, 5.06-464278 pg/mg for three phencyclidine, 5.50-192195 pg/mg for six opioids, 19.44-36.11 pg/mg for cocaine, and 50.53 pg/mg for THC in nail. Furthermore, up to 10 different compounds were detected in a single nail sample. This nail analysis method serves as a useful tool for the large-scale surveillance of illicit drugs abuse.

Effect of collagen casing on the quality characteristics of fermented sausage.

OBJECTIVE: Fermented sausage is popular all over the world for its rich nutrition and unique flavor. Sausage casing is one of the key factors affecting the quality of fermented sausage. However, there is little information involved in this field. METHODS: In this study, collagen casings were used as a wrapping material, and natural casings (pig casings) were used as a control. The effects of the two types of casings on biogenic amine content and other quality characteristics of fermented sausage were analyzed with increasing the storage time. RESULTS: The results showed that with storage time increasing, the hardness and gumminess of fermented sausage in collagen casing (CC) group were higher than those in pig casing (PC) group (P<0.05), while the elasticity in CC group was lower than that in PC group (P<0.05). In the processing and storage period, there was no significant difference in the type and content of flavor substances between the two groups. More importantly, the contents of tryptamine, putrescine, cadaverine, histamine, tyramine and phenyethylamine in fermented sausage of CC group were lower than those in PC group (P<0.05). CONCLUSION: In conclusion, this study revealed that CC could improve the quality characteristics of fermented sausage and reduce the content of biogenic amines in fermented sausage, which provides a theoretical basis for the choice of casings in industrial production in the future.

New Synthetic Cathinones and Phenylethylamine Derivatives Analysis in Hair: A Review.

The analysis of psychoactive substances in hair is of great importance for both clinical and forensic toxicologists since it allows one to evaluate past and continuative exposure to xenobiotics. In particular, a new challenge is represented by new psychoactive substances: Among this new class of drugs of abuse, synthetic cathinone and phenethylamine derivatives are often detected in biological samples. Hence, there is a growing need to develop new analytical procedures or improve old ones in order to conduct evaluations of these emerging substances. This study is a systematic review of all the instrumental and experimental data available in the literature. A total of 32 articles were included in the review. Acidic solvents proved to be the most reliable solutions for extraction. Gas chromatography and liquid chromatography coupled to tandem mass spectrometric and high-resolution mass spectrometric systems represent the majority of the involved instrumental techniques. Sensitivity must be maintained at the pg/mg level to detect any occurrences up to occasional consumption. In total, 23 out of 32 articles reported real positive samples. The most frequently detected substance in hair was mephedrone, followed by butylone, methylone, MDPV, and α-pyrrolidinophenone-type substances.

Study of Substituted Phenethylamine Fragmentation Induced by Electrospray Ionization Mass Spectrometry and Its Application for Highly Sensitive Analysis of Neurotransmitters in Biological Samples.

Although liquid chromatography-tandem mass spectrometry (LC-MS/MS) equipped with electrospray ionization (ESI) is widely employed for metabolite analysis, substituted phenethylamines commonly undergo fragmentation during ESI in-source collision-induced dissociation (CID). Unexpected fragmentation hampers not only unambiguous identification but also accurate metabolite quantification. ESI in-source CID induces N-Cα bond dissociation in substituted phenethylamines lacking a ß-hydroxy group to produce fragment ions with a spiro[2.5]octadienylium motif. In contrast, phenethylamines with a ß-hydroxy group generate substituted 2-phenylaziridium through ESI in-source CID-induced H2O loss. The fragment ion yield produced by ESI in-source CID can be estimated by the dissociation rate constant and internal energy of the analyte ion, determined by employing density functional theory calculations and the survival yield method using a thermometer ion, respectively. Fragmentation is strongly enhanced by the presence of an ß-hydroxy group, whereas N-methylation suppresses fragmentation. In particular, octopamine and noradrenaline, which contain an ß-hydroxy and primary amine groups, produce more intense fragment ion signals than protonated molecules. Regarding the quantitative analysis of phenethylamines present in the mouse brain, the noradrenaline fragment ion used as the precursor in multiple reaction monitoring (MRM) provided a higher signal-to-noise ratio in the resulting spectra than protonated noradrenaline. The present method allows for the quantitative analysis of substituted phenethylamines with high sensitivity.

Determination of 8 biogenic amines in aquatic products and their derived products by high-performance liquid chromatography-tandem mass spectrometry without derivatization.

A method for the determination of 8 biogenic amines in aquatic products and their derived products was established by HPLC-MS/MS without derivatization. The samples were extracted by 5% perchloric acid solution. N-hexane was used to clean the extract. The analytes were separated by a column of ACQUITY UPLC HSS T3 (100 mm × 2.1 mm, 1.8 µm), and gradient eluted with a mixed solution of (0.5% formic acid) and acetonitrile. Good linearity was obtained with correlation coefficients (R2) >0.99. This method achieved higher sensitivity (from 0.1 mg/kg for tyramine, 2-phenylethylamine and tryptamine to 1.0 mg/kg for spermidine, spermine, cadaverin, histamine and putrescine). The average recoveries were demonstrated in the range of 70.9%-113.1%, with relative standard deviations (RSDs) from 0.33% to 10.81%. This method was suitable for the detection of BAs in aquatic products and their products.

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.

In-tube solid phase microextraction and determination of ractopamine in pork muscle samples using amide group modified polysaccharide-silica hybrid monolith as sorbent prior to HPLC analysis.

A facile in-tube solid phase microextraction (in-tube SPME) procedure was developed to enrich ractopamine before HPLC-UV analysis. This was achieved by employing amide groups modified polysaccharide-silica hybrid monolith as an efficient sorbent. The monolith was synthesized by a simple reaction with agarose oxide and tetramethoxylisane, followed by the modification of amide groups via subsequent ring opening, "thiol-ene" click and dehydration reactions. Under the optimized extraction conditions, the enrichment factors for ractopamine, dopamine, clenbuterol, para-methylphenol and phenol were determined to be 50.5, 32.2, 4.8, 2.1 and 1.8, respectively. The monolithic column has ideal selectivity for ractopamine. Coupled with HPLC-UV, this method demonstrated a linearity within 2.0-800 ng/g for ractopamine with spiking in pork muscles (R2 = 0.9958). The LOD was 0.64 ng/g (S/N = 3) and recoveries ranged from 85.2 to 108.1% (n = 3). This approach provides a feasible way for analysis of trace ractopamine in biological samples.

Simple and rapid determination of biogenic amines in fish and fish products by liquid chromatography-tandem mass spectrometry using 2,4,6-triethyl-3,5-dimethyl pyrylium trifluoromethanesulfonate as a derivatization reagent.

A simple and rapid analytical method was developed for determination of four biogenic amines [histamine (Him), cadaverine (Cad), tyramine (Tym), 2-phenylethylamine (Pea)] in fish and fish products. This method uses a new derivatization reagent, 2,4,6-triethyl-3,5-dimethyl pyrylium trifluoromethanesulfonate (Py-Tag). The four biogenic amines in the samples were extracted with trichloroacetic acid. The diluted extract was derivatized with Py-Tag (15 min at 50°C) and then subjected to liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limits of quantification for the method were 2 mg/kg for Him, Tym, and Pea and 10 mg/kg for Cad. The matrix effects derived from the tested fish and fish products were negligible in the LC-MS/MS analysis. The impact of the sample matrices on the Py-Tag derivatization was also negligible. The trueness and repeatability of the method were assessed by performing replicate analyses (n = 5) of five samples of fish and fish products, each spiked with the four biogenic amines at three different concentration levels. Analysis of the samples found 87%-104% of the spiked concentrations and the relative standard deviations were <6.1%. A reference sample and quality control canned fish samples were analyzed by the method, and the concentrations of the Him were within acceptable limits. The developed method was successfully used to determine concentrations of the four biogenic amines in 48 fish and fish products on the Japanese market. The developed method does not require cleanup using a solid-phase extraction column or similar, and the derivatization reaction time was only 15 min. The results suggested that the present method is reliable and suitable for rapid analysis of the four biogenic amines in fish and fish products.

Determination of six underivatized biogenic amines by LC-MS/MS and study of biogenic amine production during trout (Salmo trutta) storage in ice.

Biogenic amines (BAs) are natural components of food produced mainly during metabolism in animals and plants. The determination of BAs is important because of their potential toxicity and their potential use as food spoilage indicators. In the present study, a method for the determination of six BAs (putrescine, cadaverine, histamine, ß-phenylethylamine, tyramine, and tryptamine) by Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS) with Atmospheric Pressure Chemical Ionisation (APCI) source has been used on trout samples (Salmo trutta) stored in ice for 15 days. The results showed that on day 15 quite large amounts of putrescine (76.530 mg/kg), cadaverine (85.530 mg/kg), tryptamine (25.210 mg/kg), and histamine (15.975mg/kg) were detected, while the other BAs remained low (ß-phenylethylamine: 3.230 mg/kg, tyramine: 0.165mg/kg). Furthermore, microbiological data (Total Vial Count- TVC, Pseudomonas spp, and Shewanella putrefaciens) showed that trout samples became organoleptically unacceptable on day 12, while volatile compound analysis showed a significant increase in total amounts of alcohols, aldehydes, and ketones on days 12 and 15.

Development and validation of analytical method for identification of new psychoactive substances using linear retention indexes and gas chromatography-mass spectrometry.

New Psychoactive Substances (NPS) are quickly developing to evade legislation, posing unprecedented challenges to public health and law enforcement authorities around the world. The aim of this work was to develop and validate a simple and reliable non-target gas chromatography/mass spectrometry (GC/MS) analytical method based on linear retention indexes for the expeditious identification of NPS without the need of analytical standards. The method was optimized and validated for 22 different drugs covering ten categories: phenethylamines (amphetamine, MDMA, methamphetamine, 25CNBOMe, 2-FA, 5-MAPB), "classic" drugs (cocaine, ephedrine, THC, heroine), synthetic cannabinoids (JWH-081, AM-2201, JWH-210, MAM-2201), piperazines (o-CPP, p-CPP), tryptamines (5-MeO-MiPT), synthetic cathinones (N-ethylpentylone), synthetic opioids (U-47700), aminoindanes (5-IAI), plant-based substances (Salvinorin-A) and "other" (methiopropamine). Three figures of merit (Selectivity, Precision and Robustness) were evaluated with retention index confidence intervals ranging from 0.5 to 20.6 i.u. and relative standard deviations in the range of 0.003% to 0.027% (repeatability) and 0.02% to 0.29% (intermediate precision). A general equation for estimating linear retention index variation as a function of retention time tolerance has been derived. This result in combination with a 2III6-3 fractional factorial design allowed to conclude column polarity to be only statistically relevant factor as compared to gas flow, split ratio, injection temperature, temperature program offset and column brand.

Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer.

The importance of RAC tracking in human biofluids has boosted many demands for designing an ultrasensitive tool to determine the trace value of the RAC from clinical, judicial, and forensic centers. In this study, an electrochemical biodevice has developed for the highly selective detection of this illegal feed additive under a double recognition strategy of the aptamer (Apt) and molecular imprinting polymer (MIP) on a glassy carbon electrode (GCE). The sensing relies on this fact that both the MIP and Apt act synergistically to trap the RAC molecules. The sensing surface fabrication steps have been monitored by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV(. The charge transfer resistance (Rct) value of the redox probe as a representative of the biodevice response has increased linearly with the RAC concentration increasing in a dynamic range of 1 fM to 1.90 µM. The detection limit (LOD) value has been estimated to be 330 aM, lower than all of the reported methods in the RAC sensing. Furthermore, the practical feasibility of biodevice has been evaluated in some human blood serum and urine samples. This strategy offers some useful advantages in reliable detection of the RAC, which may help in the routine analysis, as mandated by regulatory agencies.

Development and validation of a color spot test method for the presumptive detection of 25-NBOMe compounds.

The great increase of new psychoactive substances over the past decade has substantially transformed the illicit drug industry to an ever-changing dynamic market. 25-NBOMe compounds are just one of these new substance groups that pose a public health risk in many countries around the world. These highly potent, hallucinogenic phenethylamines have previously been sold as "legal highs" or "synthetic LSD" and the necessity to rapidly identify their presence is crucial. While there are many laboratory-based analytical methods capable of identifying these compounds, the lack of presumptive test methods indicates the need for a specific and timely test that could be used in the field. Herein we outline the developed chemical spot test that can selectively identify the presence of 25-NBOMe compounds and related analogs through the reaction with a substituted benzoquinone reagent under basic conditions. This test method has been comprehensively validated showing a high level of selectivity, specificity, and precision with only two other illicit substances producing similar positive results as 25-NBOMe and few false-negative results seen. The working limit of detection was determined to be 225 µg and there was no cross-reactivity from potential adulterants of significance. This test has also been shown to work directly with blotter papers containing 25-NBOMe compounds, indicating no interference from this common matrix and the ability to differentiate these compounds from LSD. This method shows a high potential to be translated to a field compatible test that is simple, rapid, and selective for 25-NBOMe compounds.

Effects of differing withdrawal times from ractopamine hydrochloride on residue concentrations of beef muscle, adipose tissue, rendered tallow, and large intestine.

Ractopamine hydrochloride (RAC) is a beta-agonist approved by the U.S. Food and Drug Administration (FDA) as a medicated feed ingredient for cattle during the final days of finishing to improve feed efficiency and growth. Maximum residue limits and U.S. FDA residue tolerances for target tissues have defined management practices around RAC usage in the U.S. However, many countries have adopted zero tolerance policies and testing of off-target tissues, presenting a major challenge for international export. Therefore, the objective this study was to determine the necessary withdrawal time among cattle group-fed RAC to achieve residue concentrations below tolerance levels in muscle and off-target tissues. Specifically, both total and parent RAC residues were quantified in muscle, adipose tissue, rendered tallow, and large intestines from animals group-fed RAC and subjected to withdrawal 2, 4, or 7 days before harvest. Ractopamine (parent and total) residues were below the assay limit of detection (< 0.12 ng/g) in all muscle and adipose tissue samples from animals in control groups (no RAC). However, RAC residues were detectable, but below the limit of quantitation, in 40% of tallow and 17% of large intestine samples from control animals. As expected, mean RAC residue concentrations in muscle, adipose tissue, and large intestine samples decreased (P < 0.05) as the RAC withdrawal duration (days) was extended. Irrespective of RAC withdrawal duration, mean parent RAC residue concentrations in muscle, adipose tissue, and large intestine ranged from 0.33 to 0.76 ng/g, 0.16 to 0.26 ng/g, 3.97 to 7.44 ng/g, respectively and all tallow samples were > 0.14 ng/g (detectable but below the limit of quantitation). Results of this study provide a baseline for the development of management protocol recommendations associated with withdrawal following group-feeding of RAC to beef cattle in countries that allow RAC use and intend to export to global markets which may be subject to zero tolerance policies and off-target tissue testing.

Two-dimensional binary nanosheets (Bi2Te3@g-C3N4): Application toward the electrochemical detection of food toxic chemical.

Bismuth telluride is considered as an efficient and super-active electrocatalyst in the sector of electrochemical application. Herein, we prepared binary nanosheets (Bi2Te3) through simple solvothermal and hydrothermal method. Furthermore, to enhance the electrocatalytic activity, graphitic carbon nitrides nanosheets (g-C3N4) were used to prepare the composition of Bi2Te3/g-C3N4 binary nanosheets (BNs) with help of hydrothermal energy. Moreover, Bi2Te3/g-C3N4 hybrid was characterized by various techniques (XRD, XPS, SEM, TEM, EDS and EIS analysis). The electrochemical performance of Bi2Te3/g-C3N4 BNs modified GCEs were analyzed by electrochemical technique (DPV, EIS and CV methods). As modified the Bi2Te3/g-C3N4 BNs modified electrode exhibits excellent electrochemical activity towards food toxic ractopamine (RAC) with high-sensitive and nano-molar detection limit (LOD). Besides, the practical ability was analyzed to detect the RAC in meat samples using Bi2Te3/g-C3N4 BNs modified GCE.