Dissipation of Emamectin Benzoate Residues in Rice and Rice-Growing Environments.

The experiment developed the ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS) method for testing emamectin benzoate, and studied the metabolism of emamectin benzoate in rice plants and rice-growing environments via application of this testing method. The dissipation curve of emamectin benzoate standard substance was good at 0.5-200 µg L-1, and its correlation coefficient was greater than 0.99. In the concentration range of 0.1-50 µg kg-1, the average recovery rate of plants, soil, and field water was 82 %-102 %, and relative standard deviation (RSD) was between 0.3 % and 15.9 %. Half-lives in rice plants and soil were 0.8-2.8 days and 1.9-3.8 days, respectively, and emamectin benzoate was not detected in rice or rice hull. The experiment showed that emamectin benzoate is harmless to human health at the concentration recommended by the manufacturer.

Determination of Lactoferrin in Camel Milk by Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry Using an Isotope-Labeled Winged Peptide as Internal Standard.

An ultrahigh-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of lactoferrin in camel milk based on the signature peptide. The camel lactoferrin was purified by heparin affinity chromatography and then used to screen tryptic signature peptides. The signature peptide was selected on the basis of sequence database search and identified from the tryptic hydrolysates of purified camel lactoferrin by ultrahigh-performance liquid chromatography and quadrupole time-of-flight tandem mass spectrometry. The pretreatment procedures included the addition of isotope-labeled winged peptide and the disposal of lipids and caseins followed by an enzymatic digestion with trypsin. Analytes were separated on an Acquity UPLC BEH 300 C18 column and then detected on a triple-quadrupole mass spectrometer in 7 min. The limits of detection and quantification were 3.8 mg kg-1 and 11 mg kg-1, respectively. The recoveries ranged from 74.5% to 103.6%, with relative standard deviations below 7.7%. The validated method was applied to determine the lactoferrin in ten samples collected from Xinjiang Province.

Size-dependent modulation of graphene oxide-aptamer interactions for an amplified fluorescence-based detection of aflatoxin B1 with a tunable dynamic range.

Aflatoxin B1 (AFB1) is a common toxin found in many foods. While AFB1 sensors have been reported, few studies have shown amplified detection with tunable dynamic ranges. We herein report a simple and highly sensitive amplified aptamer-based fluorescent sensor for AFB1, which relies on the ability of nano-graphene oxide (GO) to protect aptamers from nuclease cleavage for amplified detection and on the nanometer size effect of GO to tune the dynamic range and sensitivity. The assay was performed by simply mixing the carboxyl-X-rhodamine (ROX)-labeled AFB1 aptamer, the GO, the nuclease, and the AFB1 samples. Modulating the size of the GO nanosheet resulted in three dynamic ranges, i.e., 12.5 to 312.5 ng mL(-1), 1.0 to 100 ng mL(-1), and 5.0 to 50 ng mL(-1), with corresponding limits of detection of 10.0 ng mL(-1), 0.35 ng mL(-1) and 15.0 ng mL(-1), respectively. The sensor was highly selective against other aflatoxins and common molecules in foods, and its performance was verified in corn samples spiked with known concentration of AFB1.

Photoluminescence properties of a new orange-red-emitting Sm(3+)-La3SbO7 phosphor.

The antimonate compound La3SbO7 has high chemical stability, lattice stiffness and thermal stability. Orange-red-emitting antimonate-based phosphors La3SbO7:xSm(3+) (x = 0.02, 0.05, 0.08, 0.10, 0.15, 0.20 and 0.25) were synthesized. The phase structure and photoluminescence properties of these phosphors were investigated. The emission spectrum obtained on excitation at 407 nm contained exclusively the characteristic emissions of Sm(3+) at 568, 608, 654 and 716 nm, which correspond to the transitions from (4)G5/2 to (6)H5/2, (6)H7/2, (6)H9/2 and (6)H11/2 of Sm(3+), respectively. The strongest emission was located at 608 nm due to the (4)G5/2→(6)H7/2 transition of Sm(3+), generating bright orange-red light. The critical quenching concentration of Sm(3+) in La3SbO7:Sm(3+) phosphor was determined as 10% and the energy transfer between Sm(3+) was found to be through an exchange interaction. The International Commission on Illumination chromaticity coordinates of the La3SbO7:0.10Sm(3+) phosphors are located in the orange-red region. The La3SbO7:Sm(3+) phosphors may be potentially used as red phosphors for white light-emitting diodes.

Determination of macro, micro and toxic element concentrations in peanuts from main peanut producing areas of China by ICP-MS: a pilot study on the geographical characterization.

Peanut is an important crop grown worldwide. The geographic origin of peanuts has been a topic of substantial attention since their prices can vary according to their geographic origins. This study evaluated the main macro (K, Ca, Mg, Na, and Al), micro (Fe, Zn, Mn, Ni, Sr, Mo, Cu, Se, V, Co), and toxic (As, Cd, Cr, and Pb) element concentrations in peanuts collected from six different Chinese provinces. Multi-element analysis of peanuts from different regions was carried out to develop a reliable method to trace the origin of peanuts. After microwave digestion, the element concentrations were determined through inductively coupled plasma mass spectrometry (ICP-MS). Certified reference material (CRM, GBW10011) was used to ensure accurate results. The profile of contents of major elements obtained in the current study showed the order: K > Mg > Ca > Al > Na > Zn > Fe > Mn > Ni > Sr > Mo. The average concentrations of toxic elements such as Pb, Cd, As, and Cr were very low and within the safe limits. Correlation analysis showed that there was a strong correlation between individual elements in peanut samples. The data were processed by means of the chemometric approach of linear discriminant analysis (LDA) and 97.0% of samples were correctly predicted.

Determination of extractable and non-extractable florfenicol residues as florfenicol amine in eggs by UPLC-MS/MS.

Some florfenicol (FF) metabolites have a strong binding affinity towards biomolecules in the edible tissues of some food animals. These bound FF residues cannot be extracted directly from edible tissues with organic solvents and are present in higher concentrations even than solvent extractable residues. In this study, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established to detect the total residues of FF in eggs, by quantifying the metabolite florfenicol amine (FFA). The sample was hydrolyzed at 95-100 °C for 4 hours to release sample-matrix bound residues and convert them all into FFA. The hydrolyzed sample was washed with ethyl acetate to remove interfering substances, extracted with ethyl acetate under alkaline conditions, purified by solid phase extraction and quantified by UPLC-MS/MS. The recoveries of FFA in eggs ranged from 91.2 to 102.4%, with an RSD ≤ 10.9%. The LOD and LOQ were 0.5 and 1.0 µg/kg, respectively. This method can be applied to the quantification of total FF residues in eggs.

Analysis of 17 elements in cow, goat, buffalo, yak, and camel milk by inductively coupled plasma mass spectrometry (ICP-MS).

We analyzed the concentrations of 17 elements including arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), zinc (Zn), strontium (Sr), tin (Sn), aluminum (Al), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), sodium (Na), and selenium (Se) in cow, goat, buffalo, yak, and camel milk in China using inductively coupled plasma mass spectrometry. The concentrations of the elements varied and depended on the milk type. K, Ca, Na, and Mg were the most abundant elements. Fe and Zn concentrations ranged from 1 to 6 µg g-1, while Cu, Al, and Mn concentrations ranged from 0.1 to 1 µg g-1. Trace elements, especially toxic trace elements, were present at very low concentrations; however, Pb concentrations in cow milk reached the MRLs established by the Codex Alimentarius Commission. Data were analyzed by chemometrics to evaluate the correlations between elements in the milk samples. PCA and factor analysis highlighted the relationship between element distribution and milk type. The LDA model correctly identified most milk types. Element analysis combined with chemometrics can be used to distinguish milk types.

Distribution characteristics and risk assessment of polyhalogenated carbazoles in sea water of the Yellow Sea.

Polyhalogenated carbazoles (PHCZs), a novel type of organic pollutants with dioxin-like toxicity, have gained increasing attention in the past several years. In this study detection and distribution of five PHCZ compounds found in the Yellow Sea region are studied. The range of ∑PHCZ in the detection area is 0.062-0.322 ng/L (median: 0.112 ng/L), with 3,6-dichlorocarbazole and 3,6-dibromocarbazole content being the greatest, ranging from 0.035-0.269 ng/L and 0.010-0.682 ng/L, respectively, followed by 3-CCZ (0.010-0.020 ng/L). The relative toxicity of PHCZs is evaluated by the toxicity equivalent (TEQ), in which a range of 0-0.19 pgTEQ/L (median: 0.006 pgTEQ/L) is determined. According to the results, PHCZs are widely distributed in Yellow Sea water with relatively lower toxicity, and the impact of natural factors, as well as their potential sources, are discussed in order to provide basic scientific data for the investigation of PHCZs in seawater.

Depletion of florfenicol and florfenicol amine in eggs of laying hens and growing pullets after oral administration.

In this study, we carried out two experiments to evaluate depletion of florfenicol (FF) and its metabolite florfenicol amine (FFA) in eggs from growing pullets and laying hens. Eggs were collected, and the egg white and yolk were separated. FF and FFA were analysed by liquid chromatography-tandem mass spectrometry. In the first experiment, 30 laying hens were given FF capsules at 50 mg/kg·bw-1 daily for 5 d. FF + FFA was detectable in egg white (1,190 µg/kg) on day 1 of treatment and increased slowly thereafter. After treatment, the residues decreased rapidly and were not detected by day 11. In yolk, residues were detected at a lower concentration on day 1 and increased dramatically to 3308 µg/kg at the end of treatment. The residues remained steady over the next 4 days post-treatment, followed by a rapid drop. Residues were not detectable on day 15 post-treatment. In the second experiment, four groups (B1 through B4) of growing pullets were treated in the same manner for 25, 20, 15, and 10 days before egg primiparity. FF and FFA were not detectable in the eggs of group B1; however, they were detectable in egg whites and yolks of groups B2, B3, and B4. The highest total concentrations of FF and FFA detected in egg white and yolk of group B4 were 3,190 µg/kg and 3,214 µg/kg, respectively. Thereafter, concentrations decreased until no more residues were detected in egg whites or yolks on days 17 and 21 post-treatment, respectively. Therefore, drug treatment should be stopped at least 21 d before primiparity of growing pullets to guarantee food safety.

A novel dense granule protein, GRA22, is involved in regulating parasite egress in Toxoplasma gondii.

The intracellular protozoan parasite Toxoplasma gondii is capable of invading any nucleated cell and replicates within a parasitophorous vacuole (PV). This microenvironment is modified by secretory proteins from organelles named rhoptries and dense granules. In this report, we identify a novel dense granule protein, which we refer to as GRA22. GRA22 has no significant homology to any other known proteins. GRA22 possesses a signal peptide at the N-terminal end which is responsible for dense granule and PV localization. The RH strain GRA22 contains 12 copies of tandem repeats consisting each of 21 amino acids located between the 42nd and 293rd amino acid residues from a full length of 624 amino acids. On the other hand, ME49 strain GRA22 has 10 copies of tandem repeats. The Neospora caninum GRA22 ortholog completely lacks this repetitive sequence. GRA22 knock out parasites show a similar growth rate as the parental strain. However, the timing of egress is earlier than that of the parental strain. These results suggest that GRA22 is involved in regulating parasite egress in T. gondii.