Quantum dot-labelled antibody based on fluorescence immunoassays for the determination of arsanilic acid in edible pork and liver.

Arsanilic acid (ASA) residue, which is the most common contaminant in edible animal tissues such as pork and liver, has caused environmental and food-safety concerns. In this study, direct and indirect competitive fluorescence-linked immunosorbent assays (dc-FLISA and ic-FLISA) incorporating quantum dots (QDs) as the fluorescent label were developed for the first time to detect ASA residues in edible pork and animal liver. Monoclonal antibodies against ASA and rabbit anti-mouse antibody were conjugated to orange QDs with excitation wavelengths at 450 nm, and the QD-Abs served as detection probes. The limits of detection for dc-FLISA and ic-FLISA were 0.11 ng/mL and 0.001 ng/mL, respectively. QD-FLISA was used to analyse spiked samples; recoveries ranged from 80.2%-91.2% in dc-FLISA and 82.5%-91.2% in ic-FLISA, and the coefficients of variations (CV) were less than 12%. Compared with conventional indirect competitive enzyme-linked immunosorbent assay (ic-ELISA), the QD-FLISA described here was more sensitive and accurate in the analysis of ASA residues in animal tissues. Moreover, the results of QD-FLISA correlated well with HPLC. These results indicate that dc-FLISA and ic-FLISA are sensitive and reliable for detection of ASA residues in edible animal tissues.

Selective solid-phase extraction of four phenylarsonic compounds from feeds, edible chicken and pork with tailoring imprinted polymer.

The novel molecularly imprinted microspheres for four phenylarsonic compounds have been firstly prepared with the reversible addition-fragmentation chain transfer polymerization in a suspension system. The resulting polymeric microspheres were characterized by infrared spectrum, scanning electron microscope and differential scanning calorimetry. With serial adsorption experiments, the polymeric microspheres showed highly specific molecular recognition, fast mass transfer rate and robust adsorption of the substrates. Then, the imprinted polymer was used as the solid-phase extraction adsorbent to extract the phenylarsonic compounds from the feeds, edible chicken and pork. The cartridge was washed with 2 mL ethyl acetate and eluted with 3 mL of methanol- acetic acid (90:10, v/v). The recoveries of the molecularly imprinted solid-phase extraction (MISPE) column ranged from 83.4% to 95.1%. This work provided a versatile approach for the specific extraction of the organoarsenic compounds from complicated matrices and exhibited a bright future for the application of MISPE column.

An Electrochemical Immunosensor Based on SPA and rGO-PEI-Ag-Nf for the Detection of Arsanilic Acid.

A sensitive electrochemical immunosensor was prepared for rapid detection of ASA based on arsanilic acid (ASA) monoclonal antibody with high affinity. In the preparation of nanomaterials, polyethyleneimine (PEI) improved the stability of the solution and acted as a reducing agent to generate reduced graphene oxide (rGO) with relatively strong conductivity, thereby promoting the transfer of electrons. The dual conductivity of rGO and silver nanoparticles (AgNPs) improved the sensitivity of the sensor. The synthesis of nanomaterials were confirmed by UV-Vis spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. In the optimal experiment conditions, the sensor could achieve the detection range of 0.50-500 ng mL-1 and the limit of detection (LOD) of 0.38 ng mL-1 (S/N = 3). Moreover, the sensor exhibited excellent specificity and acceptable stability, suggesting that the proposed sensor possessed a good potential in ASA detection. Thus, the as-prepared biosensor may be a potential way for detecting other antibiotics in meat and animal-derived foods.

Multiple transformation pathways of p-arsanilic acid to inorganic arsenic species in water during UV disinfection.

p-Arsanilic acid (p-ASA) is widely used in China as livestock and poultry feed additive for promoting animal growth. The use of organoarsenics poses a potential threat to the environment because it is mostly excreted by animals in its original form and can be transformed by UV-Vis light excitation. This work examined the initial rate and efficiency of p-ASA phototransformation under UV-C disinfection lamp. Several factors influencing p-ASA phototransformation, namely, pH, initial concentration, temperature, as well as the presence of NaCl, NH4(+), and humic acid, were investigated. Quenching experiments and LC-MS were performed to investigate the mechanism of p-ASA phototransformation. Results show that p-ASA was decomposed to inorganic arsenic (including As(III) and As(V)) and aromatic products by UV-C light through direct photolysis and indirect oxidation. The oxidation efficency of p-ASA by direct photosis was about 32%, and those by HO and (1)O2 were 19% and 49%, respectively. Cleavage of the arsenic-benzene bond through direct photolysis, HO oxidation or (1)O2 oxidation results in simultaneous formation of inorganic As(III), As(IV), and As(V). Inorganic As(III) is oxidized to As(IV) and then to As(V) by (1)O2 or HO. As(IV) can undergo dismutation or simply react with oxygen to produce As(V) as well. Reactions of the organic moieties of p-ASA produce aniline, aminophenol and azobenzene derivatives as main products. The photoconvertible property of p-ASA implies that UV disinfection of wastewaters from poultry and swine farms containing p-ASA poses a potential threat to the ecosystem, especially agricultural environments.

Optimization of microwave-assisted extraction for six inorganic and organic arsenic species in chicken tissues using response surface methodology.

Response surface methodology was applied to optimize the parameters for microwave-assisted extraction of six major inorganic and organic arsenic species (As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p-arsanilic acid, and roxarsone) from chicken tissues, followed by detection using a high-performance liquid chromatography with inductively coupled mass spectrometry detection method, which allows the simultaneous analysis of both inorganic and organic arsenic species in the extract in a single run. Effects of extraction medium, solution pH, liquid-to-solid ratio, and the temperature and time of microwave-assisted extraction on the extraction of the targeted arsenic species were studied. The optimum microwave-assisted extraction conditions were: 100 mg of chicken tissue, extracted by 5 mL of 22% v/v methanol, 90 mmol/L (NH4 )2 HPO4 , and 0.07% v/v trifluoroacetic acid (with pH adjusted to 10.0 by ammonium hydroxide solution), ramping for 10 min to 71°C, and holding for 11 min. The method has good extraction performance for total arsenic in the spiked and nonspiked chicken tissues (104.0 ± 13.8% and 91.6 ± 7.8%, respectively), except for the ones with arsenic contents close to the quantitation limits. Limits of quantitation (S/N = 10) for As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p-arsanilic acid, and roxarsone in chicken tissues using this method were 0.012, 0.058, 0.039, 0.061, 0.102, and 0.240 mg/kg (dry weight), respectively.

Determination of para-arsanilic acid with improved diazotization reaction using differential pulse cathodic stripping voltammetry in aqueous system.

Para-arsanilic acid (p-ASA) has been widely used in the poultry industry to promote growth and prevent dysentery. It is excreted unchanged in the manure and released into non-target sites causing organoarsenic pollution risk to the environment and living system. Therefore, simple and effective analytical strategies are demanded for determining the samples that contain p-ASA. However, direct determination of both p-ASA and ortho-arsanilic acid (o-ASA) using differential pulse cathodic stripping voltammetry (DPCSV) gives the similar voltammograms that directly hamper the analysis used by the DPCSV technique. In this study, a method to determine and differentiate p-ASA from o-ASA via diazotization and coupling reaction of the amine groups followed by the direct DPCSV determination of diazo compounds is presented. The diazotization reaction carried out at pH 1.5 and 0 ± 1°C for 10 min showed two reduction peaks in DPCSV at-70 mV and -440 mV vs. Ag/AgCl (KCl 3 M). However, when the diazotization reaction was performed at pH 12.5 and 0 ± 1°C for 40 min, a coloured azo compound was produced and the DPCSV showed only one reduction peak that appeared at -600 mV vs. Ag/AgCl (3 M of KCl). The results of this study show that only p-ASA compound gave a reduction peak, whereas o-ASA compound did not give any peak. The detection limit of p-ASA was found to be 4 × 10(-8 )M. As a result, the proposed electro-analytical technique might be a good candidate to determine and differentiate the p-ASA present in the poultry and environmental samples.

Arsenic pollution of agricultural soils by concentrated animal feeding operations (CAFOs).

Animal wastes from concentrated animal feeding operations (CAFOs) can cause soil arsenic pollution due to the widespread use of organoarsenic feed additives. This study investigated the arsenic pollution of surface soils in a typical CAFO zone, in comparison with that of agricultural soils in the Pearl River Delta, China. The mean soil arsenic contents in the CAFO zone were elevated compared to those in the local background and agricultural soils of the Pearl River Delta region. Chemical speciation analysis showed that the soils in the CAFO zone were clearly contaminated by the organoarsenic feed additive, p-arsanilic acid (ASA). Transformation of ASA to inorganic arsenic (arsenite and arsenate) in the surface soils was also observed. Although the potential ecological risk posed by the arsenic in the surface soils was relatively low in the CAFO zone, continuous discharge of organoarsenic feed additives could cause accumulation of arsenic and thus deserves significant attention.

[Simultaneous determination of arsanilic, nitarsone and roxarsone residues in foods of animal origin by ASE-LC-AFS].

A method for simultaneous determination of arsanilic, nitarsone and roxarsone (ROX) residues in foods of animal origin was developed by accelerated solvent extraction-liquid chromatography-atomic fluorescence spectrometry (ASE-LC-AFS). The ultrasound centrifugation extraction and accelerated solvent extraction were compared, and the accelerated solvent extraction conditions, namely the proportion of the extraction solvent, the extraction temperature, extraction time and extraction times, were optimized. The operating conditions of LC-AFS and the mobile phase were optimized. Under the optimal conditions, the calibration curves for ASA , NIT and ROX were linear over the concentration range of 0-2.0 mg x L(-1) and their correlation coefficients were 0.999 2-0.999 8. The detection limits of ASA, NIT and ROX were 2.4, 7.4 and 4.1 microg x L(-1) respectively. The average recoveries of ASA, NIT and ROX from two samples spiked at three levels of 0.5, 2, 5 mg x kg(-1) were in the ranges of 87.1%-93.2%, 85.2%-93.9%, and 84.2%-93.7% with RSDs of 1.4%-4.6%, 1.2%-4.2%, and 1.1%-4.5%, respectively. This method possesses the merits of convenience and good repeatability, and is a feasible method for analysis of ASA, NIT and ROX in foods of animal origin.

Design and characterization of hybrid morphology nanoarrays as plasmonic Raman probes for antimicrobial detection.

Advances in nanofabrication have allowed the production of new and more reproducible substrates for the Raman detection of trace antimicrobials in water. The superior substrate uniformity combined with the ability to control surface morphology represents a significant step forward in the design of substrates with improved enhancement factors and trace-detection capabilities. The work presented herein successfully combines electron-beam lithography (EBL) and reactive ion-etching (RIE) protocols for the construction, testing, and validation of plasmonic hybrid morphology nanoarrays for the detection of arsenic antimicrobials in water. The fabricated substrates consist of 2500 µm(2) Ag-coated silicon dioxide (SiO2)/Si pillar nanoarrays of alternating hexagonal and elliptical features. Control of simple fabrication parameters such as inter-particle spacing (gap) and its orientation relative to the laser polarization vector (parallel or orthogonal) result in over a tenfold improvement in the apparent Raman response under optimized conditions. At a 633 nm excitation frequency, the best substrate performance was observed on parallel-oriented features with a 200 nm gap, with over one order of magnitude increase in the apparent surface-enhanced Raman scattering (SERS) signal relative to standard silver-polydimethylsiloxane (Ag-PDMS) nanocomposites. Monitoring of the characteristic As-C stretching band at 594 cm(-1) allowed the detection of arsenic antimicrobials in water well within the parts per million range. Calculated surface-enhancement factors (SEF) for this substrate, employing 532, 785, and 633 nm excitation wavelengths, was within five, six, and seven orders of magnitude, respectively. The effect of substrate morphology and nanofabrication process on the Raman enhancement factor is presented.

Identification of degradation products of phenylarsonic acid and o-arsanilic acid in contact with suspensions of soils of volcanic origin.

A set of organoarsenicals were identified in aqueous phenylarsonic acid (PA) and o-arsanilic acid (AA) solutions treated with soil of volcanic origin in batch systems. The transformation products were separated by liquid chromatography (RP-LC) and identified with element selective inductively coupled plasma-mass spectrometry (ICP-MS) as well as molecular selective electrospray ionization-mass spectrometry (ESI-MS) detection after their HPLC separation. The identification of the main degradation products by means of ESI-MS, ESI-MS/MS and ESI-TOF-MS showed the occurrence of nitrophenylarsonic acid and methylphenylarsinic acid in the solutions containing AA and PA in contact with soils, respectively. Using irradiation of PA solution with visible light, new compounds related from PA appeared with increasing irradiation times which were identified as 4-hydroxyphenylarsonic acid, 3-hydroxyphenylarsonic acid and 2-hydroxyphenylarsonic acid. Additionally, a dihydroxyphenylarsonic compound was identified as impurity of PA.

Surface-enhanced Raman scattering (SERS) characterization of trace organoarsenic antimicrobials using silver/polydimethylsiloxane nanocomposites.

Organoarsenic drugs such as roxarsone and 4-arsanilic acid are poultry feed additives widely used in US broilers to prevent coccidosis and to enhance growth and pigmentation. Despite their veterinary benefits there has been growing concern about their use because over 90% of these drugs are released intact into litter, which is often sold as a fertilizing supplement. The biochemical degradation of these antimicrobials in the litter matrix can release significant amounts of soluble As(III) and As(V) to the environment, representing a potential environmental risk. Silver/polydimethylsiloxane (Ag/PDMS) nanocomposites are a class of surfaceenhanced Raman scattering (SERS) substrates that have proven effective for the sensitive, reproducible, and field-adaptable detection of aromatic acids in water. The work presented herein uses for the first time Ag/PDMS nanocomposites as substrates for the detection and characterization of trace amounts of roxarsone, 4-arsanilic acid, and acetarsone in water. The results gathered in this study show that organoarsenic species are distributed into the PDMS surface where the arsonic acid binds onto the embedded silver nanoparticles, enhancing its characteristic 792 cm(-1) stretching band. The chemisorption of the drugs to the metal facilitates its detection and characterization in the parts per million to parts per billion range. An extensive analysis of the distinct spectroscopic features of each drug is presented with emphasis on the interactions of the arsonic acid, amino, and nitro groups with the metal surface. The benefits of SERS based methods for the study of arsenic drugs are also discussed.

[Determination of arsanilic acid and sulfanilic acid as adulterant in feed additives by reversed-phase high performance liquid chromatography].

A reversed-phase high performance liquid chromatographic (RP-HPLC) method was established for the determination of arsanilic acid and sulfanilic acid as adulterant in the feed additives. The separation was carried out on a Waters Bondapak C18 column, and methanol-water (pH 2.9 adjusted by 0.01 mol/L phosphoric acid) (1 : 4, v/v) was used as the mobile phase with a flow rate of 1.0 mL/min. A diode array detector was used at 244 nm as the detection wavelength. Arsanilic acid and sulfanilic acid were separated within 3 min. The linear ranges all were 5 - 200 mg/L and the detection limits (S/N = 3) were 0.20 and 0.15 mg/L for arsanilic acid and sulfanilic acid, respectively. This method is simple and rapid, and suitable for the simultaneous determination of arsanilic acid and sulfanilic acid in feed additives.

Fluorimetric determination of arsanilic acid by flow-injection analysis using on-line photo-oxidation.

A flow-injection-fluorimetric method for the determination of arsanilic acid is proposed. The assay is based on the on-line decomposition of arsanilic acid in the presence of peroxydisulfate on irradiation with UV light. The arsenate generated in the photochemical reaction was reacted with molybdate in dilute nitric acid to form arsenomolybdic acid, which oxidised thiamine to thiochrome. The thiochrome was monitored fluorimetrically at 440 nm with excitation at 375 nm. The calibration graph was linear in the range 0.10-10.8 microg mL(-1) with a correlation coefficient of 0.999. The detection limit was 0.01 microg mL(-1) and the sample throughput was 55 samples h(-1). The applicability of the method was demonstrated by determining arsanilic acid in animal foodstuffs and water.

[Colorimetric method for the quantitative determination of arsanilic acid in combined medicated premixes]. / Kolorimetrichen metod za kolichestveno opredeliane na arsanilovata kiselina v kombinirani medikamentozni premiksi.

A colorimetric method was worked out to determine negligible amounts of arsanilic acid, based on the property of amino groups to form a yellow stained Schiff base in the interaction with an acid solution of p-dimethyl- aminobenzaldehyde. The optic density of the coloured solution in methanol is determined at 450 nm. The presence of the A, D3, C, K3 vitamins, furazolidon, neomycin sulphate, and tylosine phosphate does not interfere with the determination of arsanilic acid.