Determination of methenamine residues in edible animal tissues by HPLC-MS/MS using a modified QuEChERS method: Validation and pilot survey in actual samples

A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was developed for the determination of methenamine in edible animal tissues by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Samples were extracted with acetonitrile, and cleaned with anhydrous sodium sulfate and primary secondary amine (PSA) sorbent. An isotope dilution mass spectrometry technique was applied to compensate for matrix effect. The separation was performed on a HILIC column, and the mobile phase composed of acetonitrile-0.1% of formic acid and 5.0 mmol/L of ammonium acetate in water. The method showed a linear relationship in the range of 1.0–20.0 μg/L for methenamine, and the determination coefficients (R²) ranged from 0.9939 to 0.9995. The limit of detection (LOD) and quantification (LOQ) for methenamine in animal tissues sample was 1.5 μg/kg and 5.0 μg/kg, respectively. The average recoveries were 86.7–109.5% at spiked levels of 5.0, 25.0, 100.0 μg/kg. The intra-day precision ranged from 2.6 to 7.0%, and the inter-day precision ranged from 4.9 to 11.3%. The validated method was successfully applied to determination of methenamine in swinish muscle, kidney and liver.     

Analysis of tetracyclines in chicken tissues and dung using LC–MS coupled with ultrasound-assisted enzymatic hydrolysis

The accurate measurement of tetracycline antibiotics (TCs) in complex matrices related to chicken raising is important for food control. It was experimentally demonstrated that conventional acid deproteination methods led to high losses of TCs because TCs were strongly bounded to protein aggregates. To eliminate this effect, an ultrasound-assisted enzymatic hydrolysis method was developed to break the three-dimensional structures of proteins and release the bound TCs. This not only significantly improved the recovery of TCs but also shortened the pretreatment time from 960 to 6 min. By combining this new deproteination method and a solid phase extraction clean-up, a suitable sample preparation was achieved for the analysis of TCs with LC–MS/MS. The established LC–MS/MS analysis of TCs provided good linear ranges in the order of 20–1000 μg L⁻¹ with the limits of detection ranging from 1.05 to 3.50 μg L⁻¹ for the tested TCs. The new method yielded recoveries of TCs in spiked chicken-related samples as high as 89.1%–102.4%, being much higher than those (23.5%–36.2%) obtained using the acid deproteination process. When this method was used to analyze five practical samples of manures, it gave residual concentrations of 0.9–4.2 and 1.3–4.0 mg kg⁻¹ for oxytetracycline and chlortetracycline, respectively.     

Establishment of a method to detect sulfonamide residues in chicken meat and eggs by high-performance liquid chromatography

Sulfonamides are a group of antimicrobials used for treatment and prevention of infectious diseases in humans and animals. In veterinary practice, sulfonamides are extensively used due to its broad spectrum of activity and low cost. A multi-residue analysis of seven sulfonamides (sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethizole, and sulfamethoxypyridazine) in chicken and eggs using HPLC- DAD detection method has been proposed. Chicken and egg samples were homogenized and extracted with distilled water:ethyl acetate (1:3, v/v) liquid-liquid extraction. The extracts were defatted with n-heptane and dried under nitrogen flow at 55 °C. The dry residue was dissolved in 500 μL methanol:acetic acid:water mixture with a ratio of 10:4:36 (v/v/v) and 10 μL of the sample was subjected to HPLC determination under the following conditions: column, Luna 5 μ C18; particle size, 5 μm; mobile phase, 17 mM acetic acid: methanol: acetonitrile (83:10:7, v/v/v); flow rate, 1.0 mL/min; and detection, 270 nm. The specificity was evaluated by analyzing 30 different blank samples of chicken and eggs in order to verify the absence of potential interfering compounds. No interfering peaks were found around the retention time of analytes in the matrices under investigation. The linear correlation coefficients (r²) for 50–250 ppb range were above 0.99 for all sulfonamides tested. The mean recoveries for chicken and eggs spiked at 50, 100, and 150 ppb were in the range of 86–108% for all analytes. Repeatability and within laboratory reproducibility of the developed method was determined at 100 ppb and quantified as the relative standard deviation was lower than 15%. The decision limits were between 108 and 116 ppb for all analytes whilst the detection capability of all analytes ranged from 129 to 140 ppb. An inexpensive and simple liquid-liquid extraction with isocratic elution mode for rapid analysis of residues of seven sulfonamides in chicken and egg samples using HPLC-DAD detection was established in this study.     

Nouws antibiotic test: Validation of a post-screening method for antibiotic residues in kidney

Anticipating the rise in ‘suspect’ samples caused by the introduction of a more sensitive screening test for the presence of antibiotic residues in slaughter animals, an additional microbial post-screening method was developed. The test comprises four antibiotic group specific test plates, optimized for the analysis of kidney and has been validated according to 2002/657/EC using fortified kidney samples. For each test plate activity profiles are presented, enabling a considerate choice of one or more representative component for each test plate. This information can be used to minimize validation efforts for further implementation of the test in routine field laboratories.     

An enzyme linked immunosorbent assay for the determination of cyromazine and melamine residues in animal muscle tissues

Cyromazine and its metabolite melamine are toxic to animal and human. Herein this paper, an indirect competitive enzyme linked immunosorbent assay (ELISA) was first developed for the simultaneous determination of cyromazine and melamine in animal meats. The antigen of melamine was prepared by using of mixed anhydride method and the polyclonal antibody was obtained by immunising three rabbits with the conjugate. The antibody obtained was specific for melamine and showed 59% of crossreactivity toward cyromazine. Muscle samples were extracted with ammoniacal acetonitrile and purified by passing through a Millipore filter before ELISA analysis. The limits of detection for cyromazine and melamine were 4.5 and 1.8 ng/g, respectively. Recoveries for cyromazine and melamine from the fortified blank samples at fortification levels of 20, 50 and 100 ng/g were in the range of 87.0–98.6% and 84.6–94.3%, respectively, with coefficients of variation (CV) lower than 12%. The ELISA method was used for detection of the two analytes in some unknown samples and the results were further confirmed with a HPLC–UV method.     

Evaluation of the Bacillus calidolactis plate for post screening assay of β-lactam antimicrobial residues in Kenyan dairies

As part of efforts to establish a control program for antimicrobial residues in local Kenyan dairies, a low cost Bacillus calidolactis test plate was evaluated after laboratory standardization. Test parameters studied were: the practicability of the test handling, the test sensitivity in terms of limits of detection (LODs) compared to codex alimentarius maximum residue limits (MRLs) and repeatability within two different laboratories. The observed LODs were: penicillin G (2 μg/kg), ampicillin (2 μg/kg), amoxicillin (2 μg/kg), oxacillin (15 μg/kg), cefalexin (50 μg/kg), cephapirin (30 μg/kg) and ceftiofur (50 μg/kg). These levels were lower than established Codex Alimentarius MRLs. The agreement between the two laboratories was calculated to be 0.83 (83%) with a determined proportion of kappa (κ) ranging between 0.61 and 0.80κ which corresponds to a good agreement strength. The standard error se (k)=0.052 and the confidence intervals at 95% for κ=0.51–0.71 for the two laboratories. The study suggests that raw milk exhibiting inhibition diameters of <19 mm (p<0.05) in the B.calidolactis test plate fulfills the codex alimentarius MRL for the tested β-lactams at their various detection levels. It was concluded that the plate test could be a useful and affordable post screening assay for commonly used β-lactam antimicrobial in the dairy sector within low-income countries.     

分子筛脱蜡评价实验中正构烷烃含量的测定

采用分子筛直接吸附再经色谱数据补正的方法 ,测定液体石蜡的正构烷烃含量 ,并与气相色谱法的结果对比 ,其一致性较好。本方法所用仪器简单 ,操作简便 ,数据重复性较好 ,相对标准偏差在±1 %以内。     

Measurement of internal quality in chicken eggs using visible transmittance spectroscopy technology

The potential of the ultraviolet and visible (UV/VIS 200–800 nm) transmittance method to inspect the internal quality (freshness) of intact chicken egg was investigated. The nondestructive measurement optical models for egg quality were also studied. Three hundred and fifty chicken egg samples were used for measuring its freshness and spectral collection during egg storage time. Two correlation models between Haugh unit and the storage time, the yolk coefficient and the storage time were developed with the correlation coefficients of 0.994, 0.987, respectively. A relationship between the intact egg transmittance and the storage time was also developed with the correlation coefficients of 0.935 at the sensitive spectral wavelength of 465 nm. It was concluded that: the nondestructive inspection of egg freshness by transmittance properties is feasible in the range of 400–600 nm, while it is impossible to inspect egg freshness in the range of 200–400 nm due to the low transmittance.     

Determination of asphaltene precipitation using a CPA equation of state

Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. Therefore, predicting asphaltene phase behavior through thermodynamic modeling may help to control its precipitation and reduce the associated problems. In this work, a new modified CPA equation of state (EoS) was used to model asphaltene precipitation. This equation is based on a combination of a new physical part and the Wertheim association term.

The results of the new model were compared with the experimental data of five oil samples. The results showed that this modified CPA EoS can predict asphaltene precipitation with good accuracy.     

Feasibility of using NIR spectroscopy to detect herbicide residues in intact olives

This study sought to assess the feasibility of using Near-Infrared Spectroscopy (NIRS) technology to detect levels of diuron herbicide in intact olives. The experimental set comprised 216 olive samples fortified with varying concentrations of diuron at values above and below the MRL (Maximum Residue Limit). A diuron-free sample set was used as control. A range of strategies was tested based on NIRS data for the construction of discriminant models using the Partial Least Squares-Discriminant Analysis (PLS-DA). The best model developed correctly classified 85.9% of samples used in the validation set by olives with a content of diuron above and below the MRL, applying a second order derivative with Multiplicative Scatter Correction (MSC). It can be concluded that the proposed reflectance NIR spectroscopy is appropriate for the quality control of herbicide diuron in intact olives.     

Determination of avermectin and milbemycin residues in bovine muscle by liquid chromatography-tandem mass spectrometry and fluorescence detection using solvent extraction and low temperature cleanup

A simple and inexpensive sample preparation method based on solvent extraction, followed by low temperature cleanup, was demonstrated to be applicable for the determination of avermectin and milbemycin residues in bovine muscle by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography with fluorescence (LC-FL) detection. The analytical methodology was validated according to the Commission Decision 2002/657/EC, using LC-MS/MS for confirmatory and LC-FL for quantitative purposes. Mean recovery was between 88.9 and 100.7% in three distinct concentrations. The coefficient of variation for repeatability and within-laboratory reproducibility ranged from 0.78 to 5.1% and from 0.28 to 9.0%, respectively. Method precision led to satisfactory values of decision limits (CCα) and detection capabilities (CCβ). The proposed method has been applied in the Brazilian National Residue Control Plan since 2010 for the determination of avermectins and milbemycin residues in bovine muscle samples. A total of 760 samples were analyzed and none of them presented residues at concentrations above the permitted levels established by the more recently applied directives.     

Inactivation of Salmonella spp. in ground chicken using high pressure processing

High Pressure Processing (HPP) is a safe and effective process for improving the microbial safety and shelf-life of foods. Salmonella is a common contaminant in poultry meat and is frequently responsible for foodborne illness associated with contaminated poultry meat. In this study the inactivation of a five-isolate cocktail of Salmonella spp. in ground chicken (95% lean) using HPP at refrigeration temperature (4–6 °C) was studied. More than 5-log CFU/g inactivation was achieved at 450 MPa for10 min. In contrast, HPP treatment at 250 MPa or 350 MPa (single-cycle, 15 min) inactivated 0.5 log or 1.7 log CFU/g, respectively. The multiple-cycle HPP mode at 250 or 350 MPa (3-cycle with 5 min/cycle) showed higher cell reduction at 1.3 or 3.3 log CFU/g, respectively. HPP at 550 MPa for 10 min may reduce the cell counts, initially at 8.5 log CFU/g, to below the detection limit (1.0 log CFU/g) in current study. The images (electron microscopy) of the HPP shocked cells were examined for structural damage, which demonstrated that Salmonella cells may still look intact (with damages on rough/irregular surface at 450 MPa stress) under Scanning Electron Microscopy (SEM), but have significant damage internally (voids and uneven mass distribution patterns) under Transmission Electron Microscopy (TEM).     

Determination of procymidone residues in ginseng by GC–ECD and GC–MS equipped with a solvent-free solid injector

A rapid method for determination of the insecticide procymidone in ginseng was studied by gas chromatographic analysis equipped with a solvent-free solid injector, Keele injector. Ginseng samples were freeze-dried, weighed carefully in milligram quantities and introduced into a glass tube in a Keele injector at a gas chromatograph injection port. The glass tube was then crushed to allow the sample to directly carry onto a capillary column in a normal manner. The recoveries of procymidone by the Keele injector method were close to those by a traditional method using a syringe, giving the recovery values ranging from 86% to 92% at the tested concentrations of 0.1 and 1.0 mg/kg. The Keele injector method was examined to detect procymidone in ginsengs obtained from agricultural markets. When 27 ginseng samples were analyzed by GC–MS and GC–ECD equipped with the Keele injector method, 14 samples of them contained procymidone in concentrations ranging from 0.2 to 0.8 mg/kg, which was the same results by the traditional method. Using the Keele injector method could skip sample preparation steps required generally in the traditional method. The data suggest that the Keele injector can be used as a sample introduction device for GC–ECD or GC–MS analysis of procymidone residues in ginsengs.     

Characterization of well skin using buildup test and radon as a tracer

Pressure buildup tests are often used to determine the reservoir permeability and skin factor to quantify formation damage. However, no quantitative method is currently available for calculating the reduced permeability of the skin zone. With the help of radon measurements during the flow period preceding the buildup test, it is possible to calculate both the radius and the altered permeability in the damaged zone based on a radial composite model.     

Determination of asphaltene precipitation using a new CPA-based equation of state

Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. Therefore, predicting asphaltene phase behavior through thermodynamic modeling may help to control its precipitation and reduce the associated problems. In this work, a new modified cubic-plus-association (CPA) equation of state (EoS) was used to model asphaltene precipitation. This equation is based on a combination of a new physical part and an association term.

The new physical part has an evolved cubic equation of state with a new attractive term in this work. The results of the new modification of CPA EoS were compared with the experimental data of two oil samples (oil samples 1 and 2) that belonged to Moradi et al. The results showed that this modified CPA EoS can predict asphaltene precipitation with good accuracy.     

Determination of thermal inactivation kinetics of Listeria monocytogenes in chicken meats by isothermal and dynamic methods

The objective of this research is to determine the thermal inactivation kinetics of Listeria monocytogenes in chicken breast meat under both isothermal and dynamic conditions. A four-strain cocktail of L. monocytogenes was inoculated to chicken breast meat. Isothermal studies were performed by submerging samples under hot water maintained at constant temperatures ranging from 54 to 66 °C. The D values at each temperature were determined and used to calculate the z value, using log(D) = log(D₀) − T/z. Dynamic studies were conducted by submerging samples in a water bath with its temperature programmed to increase linearly from 30 to 65 °C at 1.25 °C/min or 1.73 °C/min. A method was developed to determine the kinetic parameters from linear heating temperature profiles.The thermal inactivation of L. monocytogenes in chicken breast meat followed the first-order kinetics. The z value determined from the isothermal studies was 4.95 °C, which is very close to the values reported in the literature. The dynamic method can also be used to determine the thermal inactivation kinetics of L. monocytogenes. The average z value (4.10 °C) determined by the dynamic method was slightly lower than that determined by the isothermal method. However, the parameters (D₀ and z) determined from both isothermal and dynamic methods can be used to estimate the survival of L. monocytogenes exposed to linear heating temperature profiles, with statistically equal accuracies.The dynamic method explored in this study can be used to determine the D₀ and z values of microorganisms that exhibit first-order kinetics and are exposed to linear heating temperature profiles. Compared to the isothermal method, the dynamic method requires few data points and is equally accurate.     

Detection of the residues of nineteen pesticides in fresh vegetable samples using gas chromatography–mass spectrometry

In this study, we investigated the presence of 19 different agricultural pesticides in 210 samples of eight types of domestic vegetables collected from several vegetable-growing regions in Bangladesh. A multiresidue method was developed to detect the pesticide levels in the collected samples using gas chromatography with mass spectrophotometry (GC–MS). Pesticide residues were detected in 51.30% of the total samples, and among the positive samples, 38.89% contained levels above the maximum residue levels (MRLs). The most frequently detected pesticides were chlorpyrifos (34) followed by carbofuran (17), diazinon (16), carbaryl (14), malathion (11), endosulfan (8), cypermethrin (7) and dimethoate (6). Some (10.47%) of the samples contained multiple residues. It is concluded that the continuous monitoring and strict regulation of pesticide use on food crops, especially vegetables, are necessary.