Residue investigation of some phenylureas and tebuthiuron herbicides in vegetables by ultra-performance liquid chromatography coupled with integrated selective accelerated solvent extraction-clean up in situ.

BACKGROUND: Some trace amounts of urea herbicide residues can be transferred to humans via the food chain, thereby being potentially harmful to human health. The development of a robust analytical methodology for effective sample preparation and simultaneous determination of herbicide residues in vegetable samples is required for achieving food safety. RESULTS: The diuron-molecularly imprinted polymers (MIPs) synthesized have excellent affinity and high selectivity to phenylureas (monolinuron, isoproturon, diuron and linuron) and tebuthiuron. A novel automated procedure with better selectivity for vegetable sample treatment was developed by integrated matrix solid-phase dispersion-accelerated solvent extraction clean-up in situ. Five herbicides can be baseline separated with runtime down to 5 min by ultra-performance liquid chromatography, and good linearity was obtained with a correlation coefficient (r) of 0.9999. The limit of quantification of the method was in the range of 0.8-2.3 µg kg-1 . Diuron residue in cherry tomato sample was found to be 40 µg kg-1 . CONCLUSION: The developed method has satisfactory selectivity, good linearity, high sensitivity and accuracy as well as speediness, and can ensure rapid selective extraction and sensitive multi-residue analysis at low microgram per kilogram levels of the herbicides in vegetable food. © 2018 Society of Chemical Industry.

Rapid selective accelerated solvent extraction and simultaneous determination of herbicide atrazine and its metabolites in fruit by ultra high performance liquid chromatography.

A selective accelerated solvent extraction procedure achieved one step extraction and cleanup for analysis of herbicide atrazine and its metabolites in fruit. Using a BEH C18 analytical column and the gradient mode with 2 mM ammonium acetate aqueous solution/acetonitrile as a mobile phase achieved effective chromatographic separation of the five analytes within 4 min. The calibration curves were linear over two orders of magnitude of concentration with correlation coefficients (r) of 0.9996-0.9999. The method limit of quantification was 1, 2, 1.5, 3, and 2 µg/kg for atrazine, desethylatrazine, desisopropylatrazine, desethyldesisopropylatrazine, and hydroxyatrazine, respectively, in the case of atrazine it is at least two orders of magnitude lower than the maximum residue limit (0.25 mg/kg). The intra-day and inter-day precisions of the five analytes were in the range of 2.1-3.5 and 3.1-4.8 %, respectively. The recoveries of the five analytes at three spiked levels varied from 85.9 to 107% with a relative standard deviation of 1.8-4.9% for pear and apple samples. The ultra high performance liquid chromatography with diode array detection method was proved to be fast, inexpensive, selective, sensitive, and accurate for the quantification of the analytes in pear and apple samples.

Biomimetic Modification and In Vivo Safety Assessment of Superparamagnetic Iron Oxide Nanoparticles.

The efficacy of superparamagnetic iron oxide nanoparticles (SPIONs) for biomedical applications depends on the magnetic properties, long time stability in biological fluids, and specific targeting capacity. The properties of SPIONs were generally improved by surface modification, but common modification technologies were usually conducted with multi-steps under rigid conditions. In this work, a facile and simple approach to synthesize functionalized SPIONs contrast agents was set up. First of all, SPIONs were prepared by an improved ultrasonic co-precipitation method. Then the surfaces of these SPIONs were modified biomimeticly by dopamine (DA) with strong adhesion. At last, the c(RGDyK), a biomolecule with the capacity of specific targeting capacity towards liver tumor cells, were coupled with DA on SPIONs via Mannich reaction. Thus the novel magnetic composite nanoparticles (abbreviated as c(RGDyK)-PDA-SPIONs) were successfully prepared. The as-synthesized nanoparticles were characterized by scanning electron microscope (SEM), dynamic light scattering, magnetic hysteresis loop measuring instrument. As a result, that the c(RGDyK)-PDA-SPIONs had an average size of about 50 nm and uniform distribution, and had superparamagnetic properties, good water dispersion stability. The acute toxicity test of the assynthesized c(RGDyK)-PDA-SPIONs to mice was also investigated. It was observed that LD50 of c(RGDyK)-PDA-SPIONs was 4.38 g/kg, with a 95% confidence interval ranging from 3.49 g/kg to 5.87 g/kg. These results indicated the novel c(RGDyK)-PDA-SPIONs had excellent biocompatibility, which was endowed with a potential capacity to serve as MRI contrast agents in diagnosis and treatment of the liver tumor.

Gene expression profiling analysis of locus coeruleus in idiopathic Parkinson's disease by bioinformatics.

This study aimed to explore the underlying molecular mechanisms of idiopathic Parkinson's disease (IPD) by bioinformatics analysis. Gene expression profile GSE34516 was downloaded from the Gene Expression Omnibus. Eight locus coeruleus post-mortem tissue samples derived from four IPD patients and four neurological healthy controls were used to identify the differentially expressed genes (DEGs) by paired t test. Based on the DEGs, principal components were analyzed. The Gene Ontology functional and Kyoto Encyclopedia of Genes and Genomes pathway analysis of the genome microarray data were then performed. Finally, protein-protein interaction (PPI) network of the DEGs was constructed. Total 261 DEGs including 195 up-regulated and 66 down-regulated DEGs were identified. Intracellular protein transport and RNA splicing via transesterification reactions were selected as the most two significantly enriched functions. Mismatch repair, N-glycan biosynthesis, spliceosome and nucleotide excision repair were the significantly enriched pathways. In the PPI network, CTSS, CD53, IGSF6, PTPRC and LAPTM5 were the hub nodes. Intracellular protein transport and RNA splicing via transesterification reactions were closely associated with IPD. The DEGs, such as CX3CR1, SLC5A7, CD53 and PTPRC may be the potential targets for IPD diagnosis and treatment.

Synthesis and evaluation of dummy molecularly imprinted microspheres for the specific solid-phase extraction of six anthraquinones from slimming tea.

Dummy molecularly imprinted microspheres with danthron as template were synthesized and their performance was evaluated. Accelerated solvent extraction can rapidly and effectively remove template molecules from the microspheres. The microspheres were applied as a specific sorbent for solid-phase extraction of six anthraquinones from slimming tea, showing excellent affinity and high selectivity to danthron and the target analytes. The molecular recognition mechanisms were discussed by the experimental validation with IR spectroscopy. The sample was treated using accelerated solvent extraction followed by dummy molecularly imprinted microspheres solid-phase extraction. Under the optimized ultra high performance liquid chromatographic conditions, the six target analytes can be baseline separated in 8 min, and good linearity was obtained in a range of 0.1-40 µg/mL with the correlation coefficient (r(2)) of ≥0.9998. The method limit of quantification was in a range of 1-2 mg/kg, it can ensure analysis of anthraquinones at mg/kg level. The intra- and interday precision (RSD, n = 6) for the analysis of the six analytes in a slimming tea was less than 4.5 and 5.4%, respectively. The developed method can be applied for the selective extraction, effective separation, and rapid determination of six anthraquinones in slimming tea.

Highly sensitive determination of cyromazine, melamine, and their metabolites in milk by molecularly imprinted solid-phase extraction combined with ultra-performance liquid chromatography.

A novel molecularly imprinted solid-phase extraction-ultra-performance liquid chromatography (MISPE-UPLC) method for effective separation and simultaneous determination of cyromazine, melamine, and their metabolites (ammeline and ammelide) in milk samples was developed. Molecularly imprinted polymers (MIP) were synthesized in an ethanol-water system, with melamine as the template and methacrylic acid as the organic functional monomer. The MIP were applied as a specific sorbent for the selective solid phase extraction of cyromazine, ammelide, melamine and ammeline. The molecular recognition mechanism was investigated by molecular simulation and the experiment was validate by using Fourier transform infrared spectroscopy and (1)H nuclear magnetic resonance spectroscopy. A new mechanism based on the formation of both an amido group and hydrogen bonds was developed. A binding study demonstrated that the MIP showed excellent affinity to and high selectivity for melamine and related compounds. Under optimized conditions, we achieved good linearity of the calibration curves with correlation coefficients >0.999. Low limits of quantification (LOQ) for the method were determined to be 1.25, 1.25, 2.59, and 6.42 µg/kg for cyromazine, ammelide, melamine, and ammeline, respectively, which were 3 orders of magnitude smaller than the maximum residue limit (MRL). The high sensitivity of this method allows detection at the microgram per kilogram level. The proposed MISPE-UPLC method is a highly selective and sensitive method for determination of cyromazine, melamine, and their metabolites (ammeline and ammelide) for use in the control and quality assurance of milk.

Multi-class, multi-residue analysis of trace veterinary drugs in milk by rapid screening and quantification using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry.

A simple and rapid multi-class multi-residue analytical method was developed for the screening and quantification of veterinary drugs in milk by ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). A total of 90 veterinary drugs investigated belonged to almost 20 classes including lincomycins, macrolides, sulfonamides, quinolones, tetracyclines, ß-agonists, ß-lactams, sedatives, ß-receptor antagonists, sex hormones, glucocorticoids, nitroimidazoles, benzimidazoles, nitrofurans, and some others. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure was developed for the sample preparation without the solid-phase extraction step. The linearity, sensitivity, accuracy, repeatability, and reproducibility of the method were fully validated. The response of the detector was linear for each target compound in a wide concentration range with a correlation coefficient (R(2)) of 0.9973 to 0.9999 (among them R(2)>0.999 for 73 of 90 analytes). The range of the limit of quantification for these compounds in the milk ranged from 0.10 to 17.30µg/kg. The repeatability and reproducibility were in the range of 2.11 to 9.62% and 2.76 to 13.9%, respectively. The average recoveries ranged from 72.62 to 122.2% with the RSD (n=6) of 1.30 to 9.61% at 3 concentration levels. For the screening method, the data of the precursor and product ions of the target analytes were simultaneously acquired under the all ions MS/MS mode in a single run. An accurate mass database for the confirmation and identification of the target compounds was established. The applicability of the screening method was verified by applying to real milk samples. The proposed analytical method allows the identification and confirmation of the target veterinary drugs at trace levels employing quick analysis time. Certain veterinary drugs were detected in some cases.

Research on degradation of penicillins in milk by ß-lactamase using ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry.

The degradation of penicillin G, penicillin V, and ampicillin in milk in the presence of ß-lactamase was investigated by ultra-performance liquid chromatography coupled with electrospray ionization-time-of-flight mass spectrometry. Degradation products of the 3 penicillins in milk were identified based on the fact that the metabolites or degradation products contain a substructure of penicillin, and their degradation pathways in acidic milk in presence of ß-lactamase were developed. The influence of factors on the degradation was investigated, including ß-lactamase dosage, temperature, time, and acidity. The ratio of the 2 degradation products (penicilloic acid and penilloic acid) is different at different temperatures and pH. Penicilloic acid was the dominant species obtained at pH 6 under 40°C, but, being unstable, it could not be used as a standard for accurate analysis of penicilloic acid, and also could not be used as target for detection of penicillins in milk. Penilloic acid was the dominant species obtained at pH 2 above 40°C; it was stable and could be used as a standard for quantitative analysis and as target for detecting whether penicillins were used in milk.

Analysis of dissolved organic matters in Fu River of Baoding using three dimensional fluorescence excitation-emission matrix.

The fluorescence properties of dissolved organic matter (DOM) in Fu River in Baoding were investigated by three-dimensional fluorescence spectrometry. The type, distribution and origin of the DOM were estimated on basis of the position, number and intensity of fluorescence peaks in the spectra. Two types of fluorescence peaks were detected from Fu River. There are protein-like fluorescence peaks A with Ex/Em = 225-230/340 nm and soluble microbial metabolites peaks B with Ex/Em=275/340-350 nm. The protein-like fluorescence peaks and soluble microbial metabolites peaks were founded in different times and stations in Fu River. Certain correlation was observed between the fluorescence intensity of DOM and the water quality parameters of Fu River. Good correlation of different fluorescence peaks showed the same of source. The fluorescence intensity of the two types had a significant positive relationship with COD, TN, TP and NH3-N concentration, this phenomenon indicating that the fluorescence peaks can speculate the level of pollution of Fu River. These results provided a reference for the pollution control in Fu River.

Preparation of doxycycline-imprinted magnetic microspheres by inverse-emulsion suspension polymerization for magnetic dispersion extraction of tetracyclines from milk samples.

A magnetic dispersion extraction method was developed based on a molecularly imprinted magnetic microsphere (MIMM) for the selective clean-up and enrichment of tetracycline antibiotics from milk samples. The MIMMs were prepared by inverse-emulsion suspension polymerization, using doxycycline, trimethylolpropane trimethacrylate, acrylamide, methacrylic acid, and surface-modified Fe3 O4 as a template molecule, crosslinker, functional monomer, and magnetic component, respectively. Synthesis and extraction conditions were optimized for obtaining excellent affinity and high selectivity. The magnetism, covering amount, and selectivity of the magnetic microspheres were characterized by a vibrating sample magnetometer, thermogravimetric analysis, and a competitive recognition experiment. The MIMMs were applied to separate tetracycline antibiotics from milk samples by magnetic dispersion extraction, and an enrichment factor of 9.28 and a good sample clean-up were obtained. The average recoveries of four tetracycline antibiotics were obtained in the range of 74.5-93.8% with a precision of 1.2-5.2%. The LODs and LOQs of the proposed method were in the range of 7.4-19.4 and 24.7-64.7 µg/kg, respectively. The results indicated that magnetic dispersion extraction using MIMMs is a powerful tool for food-sample pretreatment with high selectivity and a simplified procedure.

Development of a novel chemiluminescence method for the determination of cefazolin sodium in injectable powder and human urine based on a luminol-Cu(III) complex reaction in alkaline medium.

A novel chemiluminescence (CL) method was developed for the determination of cefazolin sodium based on the CL reaction between the [Cu(HIO6)2](5-) Cu(III) complex and luminol in alkaline solution. Results showed that CL emission of Cu(III) complex-luminol in alkaline medium was significantly different from that in acidic medium. A possible mechanism of the enhanced effect of cefazolin on CL emission of the [Cu(HIO6)2](5-)-luminol system was proposed. The effect of the reaction conditions on CL emissions was examined. Under optimized conditions, a good linear relationship was obtained between CL intensity and concentrations of cefazolin sodium in the range of 2.0 x 10(-8) to 2.0 x 10(-6) g/mL with a correlation coefficient of R(2) = 0.9978. The limit of detection was 4.58 x 10(-9) g/mL. The proposed method was applied for the determination of cefazolin sodium in real samples with recoveries of 82.0-109% with an RSD of 0.7-2.1%. The proposed method was successfully used for the determination of cefazolin sodium in injectable powder preparations and human urine with satisfactory results.

[Identification of geographical origins of rice with pattern recognition technique by near infrared spectroscopy].

A rapid method was developed for discrimination of the geographical origins of rice with pattern recognition technique by near infrared spectrocopy (NIRS). A total of 119 geography signs product Xiangshui rice samples and 90 rice (Non-Xiangshui rice) samples produced from other places were analyzed by NIRS. After first derivative and smooth processing, principal component analysis (PCA) was used to reduce the dimensionality of the spectral data. Through the loading graph of the first three principal components, characteristic wave band (7 700-6 700, 5 700-4 300 cm(-1)) with max-relativity was determined. In whole wave, using agglomerative hierarchical cluster analysis and Fisher's linear discriminant, the discrimination of Xiangshui rice and Non-Xiangshui rice was all 100%. The correct rate of specific geographical origins of Non-Xiangshui rice was 91.9% by cluster analysis and 96.7% by discriminant analysis. For analysis in the characteristic wave bands, the correct rate of discriminant by cluster analysis was higher than the analysis result through the range of the whole band. Therefore, characteristic wave band has strong representativeness. The results indicate that it is feasible to discriminate the geographical origins of rice with pattern recognition technique by NIRS, and selecting characteristic wave band is one of the validated methods to improve the precision of the discrimination mode.

Simultaneous determination of the combined drugs of ceftriaxone sodium, metronidazole, and levofloxacin in human urine by high-performance liquid chromatography.

AIM: To develop a new high-performance liquid chromatography (HPLC) method for simultaneous determination of the combined drugs (ceftriaxone sodium, metronidazole, and levofloxacin) in human urine. METHODS: Ceftriaxone sodium, metronidazole, and levofloxacin were separated on a Kromasil 100-5 C18 (250 mm × 4.6 mm, 5 µm, AKZO NOBEL, Bohus, Sweden) analytical column, using the mobile phase consisted of 1.5 mM KH(2) PO(4) (pH 4.5) with 0.0125% triethylamine-methnol (70:30, v/v). Ceftriaxone sodium, metronidazole, and levofloxacin were detected by a photodiode-array detector at 247, 320, 292 nm, respectively. RESULTS: Under optimal conditions, the effective separation of ceftriaxone sodium, metronidazole, and levofloxacin was achieved. A good linearity with the correlation coefficients more than 0.999 was demonstrated. The detection limits of ceftriaxone sodium, metronidazole, and levofloxacin were 0.05, 0.01, and 0.25 µg/ml, respectively, and the average recoveries in human urine were in the range from 97.73 to 100.7% with the average relative standard deviation (RSD) in the range of 2.5% and 3.0%. CONCLUSION: The proposed method was sensitive, accurate, and rapid. This work may provide a reference for clinical rational drug use and methodology for the pharmacokinetics study of the combined drugs.

Degradation of naproxen by combination of Fenton reagent and ultrasound irradiation: optimization using response surface methodology.

A central composite factorial design methodology was employed to optimize the degradation of naproxen (NPX) by the combination of Fenton reagent and ultrasound (US) irradiation. In this study, the variables considered for the process optimization were the hydrogen peroxide, ferrous ion and NPX initial concentrations, while ultrasonic power amplitude was adjusted at 90% and initial pH was 3. An appropriate quadratic model was developed in order to plot the response surface and contour curves. Optimum dosage of Fenton reagent for NPX removal was found to be hydrogen peroxide concentration = 9.98 mmol L⁻¹, ferrous ion concentration = 4.83 mg L⁻¹ while NPX concentration was equal to 20 mg L⁻¹. A degradation efficiency of 100% was achieved within 10 min under US.

[Curve fitting based on genetic algorithms for quantitative resolution in overlapped fluorescence spectra].

The exponentially modified Gaussian (EMG) model-based genetic algorithm was used as a fitness function for fitting fluorescence spectrogram. The method was effective for solving the interference of fluorescent substance in the course of the multi-component quantitative analysis. As an example, the interference of endogenous fluorophores in different urines with the fluorescence of gatifloxacin (GFLX) was examined. A good eradicating efficacy was achieved by using the fitting fluorescence spectrogram. Under the optimized experimental conditions, the good linear relationship between the fluorescence intensity and GFLX concentration was obtained in the range of 0.06-3.5 microg x mL(-1) with a correlation coefficient of 0.9994. The detection limit and recovery were 0.02 microg x mL(-1) and 99.2%-109.4%, respectively, with the relative standard deviation from 1.3% to 2.7%. The proposed fitting fluorescence spectrometric method was rapid, simple and highly sensitive for the determination of GFLX in different human urine without preseparation. The recovery, selectivity, linearity, precision and accuracy of the method are convenient for routine assays and pharmacokinetic studies.

[Determination of 9 heavy metal elements in sediment by ICP-MS using microwave digestion for sample preparation].

A method for determining 9 heavy metal elements in soil and sediment was developed by using microwave digestion-ICP-MS. The mixture of HNO3-H2O2-HF was found to give the best digestion results for soil and sediment of samples. Under the optimized conditions, the samples were analyzed by ICP-MS with the triple internal standard elements Ge, In and Bi. The results showed that all their correlation coefficients were over 0.999. The national standard soil referenee material (ESS-1 GSBZ50011-88) was analyzed by the described method and the results were accorded with the reference values. The measurement precision range was from 0.48% to 5.73% in terms of relative standard deviation. The recoveries and the limits of detection were in the ranges of 98.0% to 100.7% and 0.011 to 0.328 microg x L(-1) respectively, and 11 sediment samples were determined by the proposed method. It was indicated that the method was reliable for determining heavy metal elements in soil and sediment samples.

Time-varying spillovers among pilot carbon emission trading markets in China.

Clarifying the time-varying spillovers among pilot carbon emission permit trading markets in China is an important foundation for building the national carbon emission trading market. We calculate the dynamic spillover of carbon price return among the pilot carbon emission permit trading markets in China with the time-varying connectedness approach. The dataset is constructed from transaction data from seven pilot carbon markets in China during the period of June 23, 2014, to December 31, 2020. The quantitative analysis suggests that (i) Beijing and Chongqing carbon emission trading markets are the main spillover markets of carbon price returns, with strong pricing power, while the Guangdong and Tianjin markets are the main receivers of the price return spillover in other pilot carbon emission trading markets. (ii) The spillover effect among China's carbon markets has a strong policy orientation. The improvement and development of the carbon market driven by macroeconomic regulation and control policies can effectively improve the spillover ability of the carbon market, and the market trading activity, namely the volatility of the carbon price return rate, can amplify the spillover ability of the carbon market in the short term. (iii) There exist three types of price return spillover among China's pilot carbon emission trading markets, including central divergence, one-way chain transmission, and circular spillover. Along with the improvement of market operation efficiency, the central divergent type of spillover shifts to the pattern of circular spillover. It is necessary for the government to improve market efficiency and ensure the coordinated development of China's pilot carbon emission trading market and national carbon emission trading market.

Longitudinal changes in the hypothalamic-pituitary-adrenal axis and sympathetic nervous system are related to the prognosis of stroke.

Background and purpose: This study sought to improve methods to identify biomarkers in the neuroendocrine system related to stroke progression to improve the accuracy of traditional tools for evaluating stroke prognosis. Methods: Seventy-four stroke patients and 237 healthy controls were prospectively included. We measured urinary epinephrine (E), noradrenaline (NE), dopamine (DA) and cortisol (F) on days 1, 3, and 5 after stroke onset and plasma F, adrenocorticotropic hormone (ACTH), thyrotropin (TSH), prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and growth hormone (GH). The correlation between these hormone levels and 90-day prognosis was analyzed, their value in assessing prognosis was compared with lesion volume and National Institutes of Health Stroke Scale (NIHSS) scores using receiver operating characteristic (ROC) curves, and their correlation with conventional clinical variables was assessed. Results: Levels of F, 24-h urinary free cortisol(UFC), E, NE, DA, and GH on days 1, 3, and 5 were significantly higher in stroke patients than in controls (P < 0.01), while ACTH and TSH decreased, gradually approaching normal within 5 days of onset. Levels of E, NE, F, and 24-h UFC were proportional to severity, and all gradually decreased within 5 days of onset in patients with a good prognosis and gradually increased or remained high in those with a poor prognosis. After adjustment for age, sex, NIHSS, or Glasgow Coma Scale (GCS) score, F > 13.6 µg/dL, ACTH > 22.02 pg/mL and NE > 123.5 µg/ 24 h were identified as risk factors for a poor prognosis 90 days after stroke (P < 0.05). The combination of F, ACTH, NE, white blood cell count (WBC), glucose (Glu), and hemoglobin (Hb) was significantly more accurate than lesion volume (AUC: 0.931 vs. 0.694 P = 0.019) and NIHSS score (AUC: 0.931 vs. 0.746 P = 0.034) in predicting poor prognosis of stroke 1 day after onset. Hormones and traditional clinical variables were correlated to varying degrees, with NE correlating most strongly with 24-h UFC (r = 0.54) and moderately positively with lesion volume (r = 0.40) and NIHSS score (r = 0.45). Conclusions: Stroke causes significant time-phased dynamic changes in the hypothalamic-pituitary-adrenal axis and sympathetic nervous system, and plasma F, ACTH, and urinary NE levels can be used to assess stroke severity and prognosis. Chinese clinical trial registry: Registration Number: ChiCTR1900024992. Registration Date: 2019/8/6.

Development of chemiluminescence method for determination of 10-hydroxycamptothecin based on luminol-[Ag(HIO6)2]5⁻ reaction in alkaline solution.

A novel chemiluminescence (CL) method was developed for the determination of 10-hydroxycamptothecin(HCPT) based on the CL reaction between [Ag(HIO6)2]5⁻ and luminol in alkaline solution. CL emission of Ag(III) complex-luminol in alkaline medium was very different from that in acidic medium. A possible mechanism of enhanced CL emission was suggested. The enhanced effect of HCPT on CL emission of the [Ag(HIO6)2]5⁻-luminol system was found. The enhanced degree of CL emission was proportional to HCPT concentration. The effect of the reaction conditions on CL emission was examined. Under optimal conditions, the limit of detection was 6.5 × 10⁻9 g mL⁻¹. The proposed method was applied for the determination of HCPT in real samples with the recoveries of 93.2-109% with the RSD of 1.7-3.3%.

Simultaneous determination of malachite green, enrofloxacin and ciprofloxacin in fish farming water and fish feed by liquid chromatography with solid-phase extraction.

An effective and sensitive method for simultaneous analysis of malachite green (MG), enrofloxacin (ENFLX) and ciprofloxacin (CPFLX) by liquid chromatography-diode array detection with solid-phase extraction (SPE) is developed. The conditions of SPE and LC were investigated and optimised. The effective separation of these compounds was achieved using a ZY1104 C18 column (250 × 4.6 mm, 5 µm) with 20 mM tetrabutyl ammonium bromide (pH 3.0)-acetonitrile as mobile phase and gradient elution. The diode array detection was used at 278 nm for ENFLX and CPFLX and at 613 nm for MG. Under the optimal conditions, the method LOD values of MG, ENFLX and CPFLX were 0.01, 0.07 and 0.10 µg L( -1) for fish farming water samples and 1.5, 10.5 and 15 µg kg( -1) for fish feed samples, respectively. The relative recoveries of the three analytes were achieved to be 76.7-82.3% with the RSDs (n = 5) of 3.2-4.6% for spiked fish farming water samples and 78.8-93.7% with the RSDs (n = 5) of 3.1-4.8% for spiked fish feed samples.