Dissipation, residues and risk assessment of oxine-copper and pyraclostrobin in citrus.

An efficient, sensitive, simple and fast method for the simultaneous determination of oxine-copper and pyraclostrobin in citrus fruit was developed and validated. The method uses ethylene diamine tetra-acetic acid as a competitive ligand to convert oxine-copper to soluble 8-hydroxyquinoline for analysis by QuEChERS and LC-MS/MS. Linear relationships were determined with correlation coefficients ranging from 0.9904 to 0.9998. The limits of detection for the analytes were 0.012-0.8 µg kg-1, and the limits of quantitation were 0.04-2.6 µg kg-1 in citrus. The average recoveries were 79.1-114.9% with relative standard deviations of less than 7.4%. The analyses of dissipation indicated that the half-lives of oxine-copper and pyraclostrobin were 1.94-3.67 and 1.79-2.48 days and the terminal residues were <0.08-8.99 and <0.02-1.90 mg kg-1, respectively. The risk quotients of oxine-copper and pyraclostrobin were 0.026-0.199 and 0.003-0.022, respectively. This risk assessment provides a reference for the safe and reasonable use of oxine-copper and pyraclostrobin and may help to establish maximum residue limits for these pesticides in China.

Quinoline biodegradation and its nitrogen transformation pathway by a Pseudomonas sp. strain.

A Pseudomonas sp. strain, which can utilize quinoline as its sole carbon, nitrogen and energy source, was isolated from activated sludge in a coking wastewater treatment plant. Quinoline can be degraded via the 8-hydroxycoumarin pathway. We quantified the first two organic intermediates of the biodegradation, 2-hydroxyquinoline and 2,8-dihydroxyquinoline. We tracked the transformation of the nitrogen in quinoline in two media containing different C/N ratios. At least 40.4% of the nitrogen was finally transformed into ammonium when quinoline was the sole C and N source. But addition of an external carbon source like glucose promoted the transformation of N from NH3 into NO3(-), NO2(-), and then to N2. The product analysis and gene characteristics indicated that the isolate accomplished heterotrophic nitrification and aerobic denitrification simultaneously. The study also demonstrated that quinoline and its metabolic products can be eliminated if the C/N ratio is properly controlled in the treatment of quinoline-containing wastewater.

Optimization of dispersive liquid-liquid microextraction of copper (II) by atomic absorption spectrometry as its oxinate chelate: application to determination of copper in different water samples.

In this study a dispersive liquid-liquid microextraction (DLLME) method based on the dispersion of an extraction solvent into aqueous phase in the presence of a dispersive solvent was investigated for the preconcentration of Cu(2+) ions. 8-Hydroxy quinoline was used as a chelating agent prior to extraction. Flame atomic absorption spectrometry using an acetylene-air flame was used for quantitation of the analyte after preconcentration. The effect of various experimental parameters on the extraction was investigated using two optimization methods, one variable at a time and central composite design. The experimental design was performed at five levels of the operating parameters. Nearly the same results for optimization were obtained using both methods: sample size 5 mL; volume of dispersive solvent 1.5 mL; dispersive solvent methanol; extracting solvent chloroform; extracting solvent volume 250 microL; 8-hydroxy quinoline concentration and salt amount do not affect significantly the extraction. Under the optimum conditions the calibration graph was linear over the range 50-2000 muicro L(-1). The relative standard deviation was 5.1% for six repeated determinations at a concentration of 500 microg L(-1). The limit of detection (S/N=3) was 3 microg L(-1).

Capillary electrophoretic assay for the stability of tris(8-quinolinolato)gallium(III) in tablet formulations.

A capillary electrophoresis (CE) method for testing the stability of a novel oral anticancer metallodrug, tris(8-quinolinolato)gallium(III) (KP46), is proposed. As both the intact drug and its eventual impurity or/and decomposition product, 8-quinolinol, are not charged (at most of the pH range), the micellar-mediated CE mode based on using micellar concentrations of sodium dodecyl sulfate was employed. The running electrolyte conditions were optimized in order to resolve the peak of KP46 from the signal of 8-quinolinol, as well as from these of tablet matrix components. The stability of KP46 in different organic and water-organic solvent systems was studied regarding its limited solubility and the following recovering experiments. The method thus developed was applied to the determination of KP46 in tablet formulations, for which sample preparation method, namely powdering and ultrasound-assisted extraction (with 50% aqueous acetone), was tested and optimized in terms of procedure time (10 min). Different in the content of the active substance (10-30%) batches of tablets stored for two years after preparation were validated and recoveries obtained at the level from 97 to 102% confirmed sufficient drug stability. This principal finding was verified by means of an independent method, gas chromatography coupled with mass spectrometry (GC-MS).

PqsA is required for the biosynthesis of 2,4-dihydroxyquinoline (DHQ), a newly identified metabolite produced by Pseudomonas aeruginosa and Burkholderia thailandensis.

A new metabolite, 2,4-dihydroxyquinoline (DHQ), was identified in cultures of the bacteria Pseudomonas aeruginosa and Burkholderia thailandensis. We found that the biosynthesis of DHQ correlates with the presence of a functional PqsA, which is a product of the pqsABCDE operon responsible for the synthesis of 4-hydroxy-2-alkylquinolines (HAQs) in P. aeruginosa. However, DHQ is not a degradation product or precursor of HAQs. This finding sheds some light on the poorly understood biosynthesis pathway of HAQs, which includes important communication signals regulating the expression of virulence factors.

DFT studies and vibrational spectra of isoquinoline and 8-hydroxyquinoline.

The geometry, frequency and intensity of the vibrational bands of isoquinoline (IQ) and 8-hydroxyquinoline (8-HQ) were obtained by the density functional theory (DFT) calculations with the B3LYP functional and 6-31 G* basis set. The vibrational spectral data obtained from the solid phase mid and far FT-IR and FT-Raman spectra of IQ and 8-HQ are assigned based on the results of the normal coordinate calculations. The observed and the calculated spectra are found to be in good agreement.

Distribution of intrasplenically injected colon cancer cells following pneumoperitoneum in mice.

BACKGROUND: Few studies have examined tumor cell distribution following laparoscopic surgery for colorectal cancer. We examined the effect of carbon dioxide pneumoperitoneum on the distribution of intrasplenically injected colon cancer cells in mice. METHODS: Mice were intrasplenically injected with 2 x 10(4) colon 26 cells labeled with 111In-oxine and were randomized to undergo pneumoperitoneum at 10 mmHg for 30 min or to receive no treatment other than anesthesia. Radioactivity of the liver, lungs, and spleen was measured 30, 60, 90, or 150 min following tumor inoculation. RESULTS: The dynamic changes in the hepatic radioactivity were not similar between groups. However, the values were not significantly different at any time point. The radioactivity of lungs was extremely low in both groups throughout the experimental period. CONCLUSIONS: Pneumoperitoneum does not appear to cause the accumulation of intraportally spreading tumor cells in the liver, but it may affect the dynamic changes of tumor cells. Also, tumor cell localization in the lungs is negligible in both pneumoperitoneum and control groups.

Assessment of the tissue distribution of transplanted human endothelial progenitor cells by radioactive labeling.

BACKGROUND: Transplantation of endothelial progenitor cells (EPCs) improves vascularization and left ventricular function after experimental myocardial ischemia. However, tissue distribution of transplanted EPCs has not yet been monitored in living animals. Therefore, we tested whether radioactive labeling allows us to detect injected EPCs. METHODS AND RESULTS: Human EPCs were isolated from peripheral blood, characterized by expression of endothelial marker proteins, and radioactively labeled with [111In]indium oxine. EPCs (106) were injected in athymic nude rats 24 hours after myocardial infarction (n=8) or sham operation (n=8). Scintigraphic images were acquired after 1, 24, 48, and 96 hours after EPC injection. Animals were then killed, and specific radioactivity was measured in different tissues. At 24 to 96 hours after intravenous injection of EPCs, approximately 70% of the radioactivity was localized in the spleen and liver, with only approximately 1% of the radioactivity identified in the heart of sham-operated animals. After myocardial infarction, the heart-to-muscle radioactivity ratio increased significantly, from 1.02+/-0.19 in sham-operated animals to 2.03+/-0.37 after intravenous administration of EPCs. Injection of EPCs into the left ventricular cavity increased this ratio profoundly, from 2.69+/-1.54 in sham-operated animals to 4.70+/-1.55 (P<0.05) in rats with myocardial infarction. Immunostaining of cryosections from infarcted hearts confirmed that EPCs homed predominantly to the infarct border zone. CONCLUSIONS: Although only a small proportion of radiolabeled EPCs are detected in nonischemic myocardium, myocardial infarction increases homing of transplanted EPCs in vivo profoundly. Radiolabeling might eventually provide an useful tool for monitoring the fate of transplanted progenitor cells and for clinical cell therapy.

LC of pharmaceutically important halogenated 8-hydroxyquinolines after precolumn derivatization with Pd (II).

An accurate, sensitive, and selective reversed phase high performance liquid chromatographic (HPLC) method was developed for the analysis of two halogenated 8-hydroxyquinoline derivatives; clioquinol (CQN) and iodoquinol (IQN). The proposed method depends on the complexation ability of the studied compounds with Pd(II) ions. Reversed phase chromatography was conducted using a 300 x 3.9 mm i.d. stainless steel column packed with 10 microm Bondclone phenyl at ambient temperature. A solution containing 0.005% w/v of Pd(II)-chloride in a mixture of acetonitrile-methanol-water (3:3:4 v/v/v) of pH 3.7 as a mobile phase pumped at a flow rate of 0.75 ml min(-1). UV-detection was performed at 282 and 285 nm for CQN and IQN, respectively. The method showed excellent linearity in the range 0.05-1.8 and 0.1-3.0 microg ml(-1) with limit of detection (S/N=2) 4.8 ng ml(-1) (1.57 x 10(-8) M) and 6.4 ng ml(-1) (1.61 x 10(-8) M) for CQN and IQN, respectively. The suggested method was successfully applied for the analysis of the studied drugs in bulk with average% recoveries of 99.68+/-0.44 for CQN and 99.65+/-0.53 for IQN. The proposed method was successfully applied for the analysis of the studied drugs in single or combined dosage forms with average% recoveries of 99.41+/-0.51-100.02+/-0.63. The proposed method could be used successfully for the determination of the studied compounds in the presence of their degradation product as they could be eluted with different retention times. The presence of metronidazole (MNZ) or tolnaftate (TFT) with the studied drugs does not affect their accurate determination. The results obtained were favorably compared with those obtained by the reference method. The results were satisfactorily, accurate, and precise.

High-performance liquid chromatographic assay of 8-hydroxyquinoline sulfate and its stability in immunobiological preparations.

Because of the ability of 8-hydroxyquinoline sulfate (8-HQS) to irreversibly bind metals from rubber stoppers, the stability of 8-HQS in tuberculin solutions was investigated. For the determination of 8-HQS, a simple and sensitive reversed-phase HPLC method with detection at 240 nm was developed and validated. Rapid decreases in concentrations of 8-HQS were found in samples stored in original vials which were exposed to different temperatures and vial positions.

Development of a novel octadecyl-bonded silica column and evaluation of its reliability in chromatographic analysis.

The chromatographic characterization of an octadecyl-bonded silica (ODS) column for high-performance liquid chromatography is described. In general, columns of the same type but obtained from various manufacturers give different chromatographic results, due to differences in the purity of column packings, the properties of the silica gel supports and the density of silanols on the surface of the silica gel. In order to solve this problem and to obtain a high performance ODS column, a series of methods with different samples and conditions were evaluated. The result is important for the optimization of conditions for the synthesis of ODS packings and for minimizing the deleterious effects arising from adsorption activity and metal impurity.

Reverse-phase high-performance liquid chromatographic determination of halogenated 8-hydroxyquinoline compounds in pharmaceuticals and bulk drugs.

A reverse-phase high-performance liquid chromatographic (HPLC) method was developed for determining iodochlorhydroxyquin, 5,7-dichloro-8-hydroxyquinoline, and 5,7-diiodo-8-hydroxyquinoline in creams, ointments, shampoos, tablets, and bulk drugs. A column packed with 10-micron phenyl-silica and a mobile phase of 0.001 M NiCl2 in acetonitrile-methanol-water (30:20:50) was used to separate the nickel complexes of the three drugs, with detection at 273 nm. Analysis of creams, ointments, shampoos, and tablets gave results close to the label declarations. Recovery of standard material added to samples was greater than or equal to 98%. Linearity of response was shown over a range of 30-150% of label claim for standards of the three drug substances. Multiple analyses of iodochlorhydroxyquin and diiodohydroxyquinoline bulk drugs showed purities of 99.96 and 98.77% with CV of 1.17 and 0.73%, respectively. The HPLC method offers an alternative to current USP procedures, which lack stability-indicating and specificity characteristics.

Infrared spectroscopy for tracing of topically applied ointment vehicles and active substances on healthy skin.

Infrared spectroscopy was used to trace active substances and ointment vehicles applied on the skin. Vaseline and lanoline could be traced after 8 hrs but not olive oil. From the active substances, ethyl-4-amino-benzoate (5 per cent), clioquinol (5 per cent), parabenes (15 per cent), 5,7-dichlor-8-hydroxy-2-methyl-chinolin (5 per cent), balsam of Peru (25 per cent) and pyroleum pini (12 per cent) could be traced 1 hr after application but had disappeared after 8 hrs. Ethylenediamine (1 per cent), chlorcresol (1 per cent), pyroleum lithantracis (5 per cent), were not traceable after 1 hr, and curiously neither neomycine sulphate in spite of its high concentration (20 per cent). The reaction of the skin surface lipids, after application of different substances, was deduced from the spectra. Clioquinol and pyroleum lithantracis seem to give rise to hydrolysis of the triglycerides, the free fatty acids being clearly identifiable. It is felt that infrared spectroscopy can be used as an effective method to trace different substances such as potent allergens on healthy or diseased skin.