Methanol-acetic Acid Research Articles

Development and validation of a non-aqueous capillary electrophoresis method for the determination of imatinib, codeine and morphine in human urine

A non-aqueous capillary electrophoresis (NACE) method that separates a tyrosine kinase inhibitor, imatinib, together with its main metabolite and two analgesics, codeine and morphine, from human urine is proposed. After a solid phase extraction step in urine, the four drugs were separated through a fused-silica capillary at 22 kV and 25 °C and detected at 207 nm. For this purpose 15 mM ammonium acetate and 1% acetic acid in methanol were used as the background electrolyte. Detection limits of 130 and 80 μg L−1 for imatinib and its metabolite and 40 and 60 μg L−1 for codeine and morphine were obtained. According to the validation study, the developed method was proved to be accurate, precise, sensitive and specific. The developed method is simple, rapid and sensitive and has been used to determine imatinib, codeine and their metabolites at clinically relevant levels in human urine from different patients under leukemia or analgesic treatment.

Active Ingredient Estimation of Clopyralid Formulation by Reversed Phase HPLC

A simple, accurate, and reliable high-performance liquid chromatography (HPLC) method was developed for determination, separation and estimation of clopyralid active ingredient in its formulation. The active ingredient in formulation was estimated by two methods and cleanup was performed using C18 SPE. Estimation was done by HPLC using 5 μm, C18 column, and mobile phase 0.02 % acetic acid in methanol: acetonitrile (90:10 v/v) and detection at 229 nm. The efficiency of clean up for standard clopyralid was found to be 98.02-98.66% at different concentrations. Overall recoveries for different methods ranged from 98.3-100.1 %. The LOD and LOQ were 0.1 and 0.3 ng respectively. The detector response was linear within concentrations range 0.25-10.0 ng at RSD 1.87%.

223 CRYOPRESERVATION OF IMMATURE BOVINE CUMULUS–OOCYTE COMPLEXES BY SLOW RATE FREEZING AND VITRIFICATION

Cryopreservation of mature oocytes can result in damage to the metaphase spindle due to the temperature sensitivity of microfilaments and microtubules. Cryopreservation of immature oocytes may circumvent this problem because these structures have not formed yet and the genetic material is enclosed within a nuclear envelope. Because intact oocyte cumulus-oocyte complexes (COC) are essential for normal maturation, we chose to cryopreserve immature intact COC. The aim of this study was to determine if immature COC cryopreserved by slow rate freezing or vitrification would resume meiosis upon thawing. In 2 separate experiments, immature COC (n = 102 and 79) were collected from cross-bred cattle by transvaginal ultrasound-guided aspiration and divided into 2 groups. For both experiments, the first group (n = 64 and 40) was placed directly into maturation medium (TCM 199 supplemented with 10% fetal bovine serum, 0.2 mM sodium pyruvate, 2 mM glutamine, and 5 μg mL–1 of FSH) and cultured for 22 h under 5% CO2 in air atmosphere at 39°C. In experiment 1, COC (n = 38) in the second group were cryopreserved by a slow rate freezing protocol. The COC were equilibrated for 5 min in 1.5 M ethylene glycol (EG), and 5 COC were loaded into 0.25-mL straws and placed into the cooling chamber of a Freeze Control unit at –6°C. After 5 min, straws were seeded, then cooled at 0.5°C per min to –35°C before plunging into LN. After storage in LN for 5 days, straws were removed from LN, thawed by placing straws in a 35°C water bath, and COC put into maturation as described above. In experiment 2, COC (n = 39) in the second group were cryopreserved by vitrification using a 3-step procedure. The COC were equilibrated in solutions consisting of 10% glycerol then 10% glycerol and 20% EG in PBS for 5 min each. The COC were then placed in a solution of 24% glycerol and 26% EG, and 1 to 3 COC were placed onto a cryotop device in minimal medium and plunged into LN within 45 s. After storage in LN for 2 days, COC were thawed by placing the cryotop device directly into a warmed dilution solution consisting of 0.5 M galactose in PBS. After 5 min in the dilution solution, COC were put into maturation as described above. For all groups, after 22 h of maturation cumulus cells were stripped from the oocytes by vortexing and oocytes were placed on slides for fixation in methanol acetic acid and stained with 1% orcein to determine the nuclear stage. In experiment 1, oocytes cryopreserved by slow rate freezing matured to MII at the same rate as control oocytes (45 v. 55%, P = 0.44). In experiment 2, oocytes cryopreserved by vitrification matured to MII at a lower rate than controls (49 v. 79%, P = 0.01). These results show that cryopreservation of immature intact COC is a viable alternative to cryopreservation of mature oocytes. Further studies are needed to optimize either slow rate freezing or vitrification of intact COC and determine the developmental competence of cryopreserved oocytes following fertilization.

Using vitellin monoclonal antibodies to assess the vitellogenesis-inhibiting hormone activity of Macrobrachium rosenbergii

Vitellogenesis in crustaceans is under the inhibitory regulation of the endocrine system in the X-organ/sinus gland complex in the eyestalks. In this study, two monoclonal antibodies specific to Macrobrachium rosenbergii vitellin and vitellogenin were generated to assess vitellogenesis-inhibiting hormone (VIH) activity. A combination of two monoclonal antibodies specific to the 89 and 100 kDa subunits of vitellin were used to develop a competitive enzyme-linked immunosorbent assay protocol for the quantitative determination of vitellogenin levels in haemolymph. Injection of eyestalk extracts from M. rosenbergii dissolved in either saline or in methanol-acetic acid caused a reduction in vitellogenin levels in the haemolymph at 12 and 24 h post-injection in bilateral eye-ablated prawns with developing ovaries. In contrast, the application of the heterologous eyestalk extract from Penaeus vannamei did not reduce vitellogenin levels in haemolymph. This assay is therefore specific and could be used to assess VIH activity during hormone purification.

Preparation and application of di(2-propylheptyl) phthalate molecularly imprinted solid-phase extraction sorbent

The molecular imprinted polymer (MIP) with high selectivity to di(2-propylheptyl) phthalate (DPHP) was synthesized by precipitation polymerization with dioctyl phthalate (DOP) as dummy template, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker. The binding ability of the template and functional monomer was investigated by UV spectrometry. Compared with the functional monomer acrylic acid (AA), MAA showed stronger binding capacity to DOP and the best combination mole ratio of 6 : 1. The selective adsorption performance of MIP for DOP, DPHP, dimethyl phthalate (DMP) and dibutyl phthalate (DBP) was investigated using the prepared MIP as high performance liquid chromatographic column packing. It was found that the prepared MIP showed higher retention ability and selectivity for DPHP. Using the prepared MIP as a solid-phase extraction (SPE) sorbent (MISPE), the effects of the type and amount of washing solvent and elution solvents on the recovery of DPHP were investigated. After optimization of MISPE profile, the DPHP extraction recovery of 96.8% was obtained when the following procedures were applied to MISPE cartridge: conditioning with 2 mL methanol, loading with 1 mL methanol, washing with 1 mL methanol-water (1 : 9, v/v), eluting with 5 mL methanol-acetic acid (9:1, v/v). The recovery of DPHP on non-imprinted polymer (NIP) cartridge was only 52.9%. The developed MISPE-HPLC method was applied to determine the concentrations of DPHP in rabbit serum at different time points after oral administration. It was found that the maximal concentration (c(max)) and time (t(max)) were 5.88 microg/mL and 4 h, respectively. The recoveries of spiked DPHP in rabbit serum ranged from 90.0% to 92.0% with the relative standard deviations less than 5%.

Determination of 8-iso-prostaglandin F2α (8-iso-PGF2α) in human urine by ultra-performance liquid chromatography–tandem mass spectrometry

A rapid, simple and sensitive method was developed for the determination of 8-iso-PGF2α in urine using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS); 8-iso-PGF2α-d4 was used as the internal standard (IS). Chromatographic separation was performed using an Acquity BEH C18 column with a mobile phase composition of A: 0.1% acetic acid in methanol:acetonitrile (1:1, v:v) and B: 0.1% acetic acid in water (A:B, 32.5:67.5, v:v). Detection was performed on a triple-quadrupole tandem mass spectrometer using atmospheric pressure chemical ionization (APCI) in negative mode and using multiple reaction monitoring (MRM). The MS/MS ion transitions monitored were m/z 353→193 and 357→197 for 8-iso-PGF2α and IS, respectively. The calibration curve was prepared in PBS buffer because of the presence of endogenous concentrations of analyte in the control matrix; the internal standard successfully correcting for matrix effects. Good linearity was observed over the concentration range of 0.025-20 ng/mL; the method proving to be accurate and reliable was successfully used in support of a pharmacodynamic study in humans.

Total phenolic contents and antioxidant capacities of 51 edible and wild flowers

Antioxidant capacities of 51 edible and wild flowers from China were systemically evaluated using ferric-reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays, and their total phenolic contents were measured by Folin–Ciocalteu method. The lipophilic components of flowers were extracted with tetrahydrofuran, and the hydrophilic ones were extracted with a methanol–acetic acid–water (50:3.7:46.3, v/v/v) mixture. The results showed that different flowers had diverse antioxidant capacities and phenolic compounds were a major contributor to their antioxidant activities. Rosa rugosa, Limonium sinuatum, Pelargonium hortorum, Jatropha integerrima and Osmanthus fragrans were found to have the highest antioxidant capacities. Homogentisic acid, cyanidin-3-glucoside, protocatechuic acid, catechin, gallic acid and epicatechin were quantified in these flowers using HPLC analysis. These flowers should save as potential rich resources of natural antioxidants for use as functional food ingredients or pharmaceuticals for control of diseases caused by oxidative stress.

Single-cell analysis of K562 cells: An imatinib-resistant subpopulation is adherent and has upregulated expression of BCR-ABL mRNA and protein

In chronic myeloid leukemia (CML) cells from different stages of maturation may have differential expression of BCR-ABL at both messenger RNA (mRNA) and protein level. However, the significance of such differential expression to clinical disease behavior is unknown. Using the CML-derived, BCR-ABL expressing cell line, K562, distinct plastic-adherent (K562/Adh) and nonadherent (K562/NonAdh) subpopulations were established and then analyzed both as single cells and as bulk cell populations. BCR-ABL mRNA was upregulated in K562/Adh compared with K562/NonAdh cells in both single cell and bulk population analyses (p < 0.0001). Similarly, phosphorylation of BCR protein was upregulated in K562/Adh, compared with K562/NonAdh cells (63.42% vs. 23.1%; p = 0.007), and these two K562 subpopulations were found to express significantly different microRNA species. Furthermore, treatment with the BCR-ABL tyrosine kinase inhibitor, imatinib, reduced cell viability more rapidly in K562/NonAdh compared with K562/Adh cells (p < 0.005) both at single and bulk cell levels. This discovery of an adherent subpopulation of K562 cells with increased BCR-ABL mRNA, increased phosphorylated BCR protein expression, differential microRNA expression, and increased imatinib resistance suggests that a similar subpopulation of cells can also mediate clinical resistance to imatinib during treatment of patients with CML.

Standardization of DNA Extraction from Methanol Acetic Acid Fixed Cytogenetic Cells of Cattle and Buffalo

The aim of the study is to standardize the simple method for extracting DNA from cells fixed in fixative (3:1 ratio of methanol and acetic acid glacial) mostly used for chromosomal studies in cattle and buffaloes. These fixed cells were stored for more than 6 months at refrigerated temperature. The fixed cells were washed 2-3 times by the ice cold 1x Phosphate Buffer Saline (PBS) with pH 7.4, so that effect of fixative may be eliminated. The genomic DNA was extracted by adding cell lysis and nucleus lysis buffers. The quality and quantity of DNA were estimated. The readings of nano drop and agarose gel electrophoresis indicate good quality DNA isolated with a rapid and simple protocol routinely using in our laboratory. The method enables us to study the DNA of a cattle and buffaloes after completing cytogenetic investigation or in cases where DNA samples are otherwise not available. This protocol may be useful for molecular analysis of DNA from fixed cells palettes.

Extraction of quercetin from Herba Lysimachiae by molecularly imprinted-matrix solid phase dispersion

A new kind of quercetin molecularly imprinted polymer (MIP) was synthesized and applied as a selective sorbent in matrix solid-phase dispersion (MSPD) for the extraction of quercetin in Herba Lysimachiae. The MIP was prepared by surface imprinting method using quercetin as template, methacrylic acid as functional monomer, trimethylolpropane trimethacrylate as crosslinker and methanol as porogen. The selectivity of quercetin MIP was evaluated according to their recognition to quercetin and a compound with similar molecular size (bergenin). Good binding for quercetin was observed in MIP adsorption experiment. The isothermal adsorption and dynamic adsorption experiments were also carried out in this study. The best quercetin extraction conditions were as follows: the ratio of MIP to sample was 1:1, the dispersion time was 10min, washing solvent was 2% aqueous methanol and elution solvent was acetic acid-methanol (2:98, v/v). The proposed method was compared with the method used in Chinese pharmacopeia. The similar extraction yield was obtained by the two methods. Moreover, this method is faster, simpler and can realize extraction and purification procedures in the same system.

Degradation of p12 Subunit by CRL4Cdt2 E3 Ligase Inhibits Fork Progression after DNA Damage

After acute DNA damage, the cell arrests S-phase progression by inhibiting origin initiation and fork progression to repair damaged DNA. The intra-S-phase checkpoint kinase Chk1 phosphorylates Cdc25A to target the latter for degradation by CRL1(β-TrCP) and so inhibit origin firing. The mechanism for inhibiting fork progression, however, has not been identified. Here, we show that degradation of p12, the fourth subunit of DNA polymerase δ, is critical for inhibiting fork progression. CRL4(Cdt2) is an E3 ligase that ubiquitinates and degrades p12 after UV treatment. Cells expressing a stable form of p12 exhibit UV-resistant DNA synthesis. DNA fiber assay and alkaline-sucrose gradient assay demonstrate that the impairment of fork progression after DNA damage requires p12 degradation. These results suggest that ubiquitination of p12 through CRL4(Cdt2) and subsequent degradation form one mechanism by which a cell responds to DNA damage to inhibit fork progression.

Extraction of Anthraquinones from Rhubarb by a Molecularly Imprinted–Matrix Solid-Phase Dispersion Method with HPLC Detection

A simple method based on matrix solid-phase dispersion for selective extraction of anthraquinones from rhubarb samples was developed using a molecularly imprinted polymer as sorbent. The molecularly imprinted polymer was prepared using emodin as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linking agent. The polymer was characterized by scanning electron microscopy and Fourier-transform infrared spectrometry. Isothermal adsorption and dynamic adsorption experiments were performed. The best extraction conditions for anthraquinones were obtained at a ratio of molecularly imprinted polymer to sample of 1:1, a dispersion time of 5 minutes, with 5% aqueous methanol as the washing solvent, and an elution solvent of methanol-acetic acid (99:1, v/v). Once the matrix solid-phase dispersion process was optimized, the extract was reacted with 8% hydrochloric acid for hydrolysis. The anthraquinones extracted from rhubarb were determined by liquid chromatography. The detection limits of chrysophanol, emodin, physcion, and aloe-emodin were 0.23, 0.24, 0.28, and 0.27 µg mL−1, respectively. The proposed method was compared with the method in Chinese pharmacopoeia, and the results show that the extraction yield of anthraquinones obtained by molecularly imprinted polymer–matrix solid-phase dispersion method was higher. Moreover, the proposed method is faster and simpler and can achieve extraction and purification in the same system.

Matrix solid phase dispersion assisted enzymatic hydrolysis as a novel approach for cocaine and opiates isolation from human hair

The possibility of assisting enzymatic hydrolysis (EH) procedures by sample disruption mechanisms inherent to matrix solid phase dispersion (MSPD) has been explored in the current study. EH of hair specimens from poly-drug abusers was assisted by dispersing/blending the sample (0.05g) with alumina (2.25g) before loading the dissolved enzyme (6mL of 1mgmL−1 Pronase E in 1.4M/1.4M Tris/HCl, pH 7.3) through the hair-alumina solid phase packaged inside a disposable MSPD syringe. The MSPD-EH method was developed, and it proved to offer quantitative results when isolating cocaine, benzoylecgonine (BZE), codeine, morphine and 6-monoacethylmorphine (6-MAM) from human hair samples. The procedure allows an on column clean-up/pre-concentration procedure of the isolated targets by attaching a previously conditioned Oasis HLB cartridge to the end of the MSPD syringe. The EH procedure of human hair with Pronase E can therefore be shortened to approximately 30min. Within this time, sample blending/dispersion, MSPD syringe package, elution (EH when dissolved Pronase E is passing through the sample-dispersant bed), and extract clean-up and target pre-concentration stages are achieved. Gas chromatography–mass spectrometry (GC–MS) was used for determining each target after elution from the Oasis HLB cartridges with 2mL of 2% (v/v) acetic acid in methanol, concentration by N2 stream evaporation, and dried extract derivatization with N-methyl-tert-butylsilyltrifluoroacetamide (BSTFA) and chlorotrimethylsilane (TMCS). The method was validated according to the guidance for bioanalytical method validation of the US Department of Health and Human Services, Food and Drug Administration. The simplicity of the proposed approach makes it a useful procedure for screening/quantifying drugs of abuse in hair specimens from poly-drug abusers.

Mesostructured Nanomagnetic Polyhedral Oligomeric Silsesquioxanes (POSS) Incorporated with Dithiol Organic Anchors for Multiple Pollutants Capturing in Wastewater

A functionalizable organosiliceous hybrid magnetic material was facilely constructed by surface polymerization of octavinyl polyhedral oligomeric silsesquioxane (POSS) on the Fe3O4 nanoparticles. The resultant Fe3O4@POSS was identified as a mesoporous architecture with an average particle diameter of 20 nm and high specific surface area up to 653.59 m(2) g(-1). After it was tethered with an organic chain containing dithiol via thiol-ene addition reaction, the ultimate material (Fe3O4@POSS-SH) still have moderate specific area (224.20 m(2) g(-1)) with almost identical porous morphology. It turns out to be a convenient, efficient single adsorbent for simultaneous elimination of inorganic heavy metal ions and organic dyes in simulate multicomponent wastewater at ambient temperature. The Fe3O4@POSS-SH nanoparticles can be readily withdrawn from aqueous solutions within a few seconds under moderate magnetic field and exhibit good stability in strong acid and alkaline aqueous matrices. Contaminants-loaded Fe3O4@POSS-SH can be easily regenerated with either methanol-acetic acid (for organic dyes) or hydrochloric acid (for heavy metal ions) under ultrasonication. The renewed one keeps appreciable adsorption capability toward both heavy metal ions and organic dyes, the removal rate for any of the pollutants exceeds 92% to simulate wastewater with multiple pollutants after repeated use for 5 cycles. Beyond the environmental remediation function, thanks to the pendant vinyl groups, the Fe3O4@POSS derived materials rationally integrating distinct or versatile functions could be envisaged and consequently a wide variety of applications may emerge.

Separation of acetic acid–methanol–methyl acetate–water reactive mixture

The aim of this research is to study the separation of a mixture with a methyl acetate synthesis reaction by pervaporation. The feed solutions that have compositions close to a chemical equilibrium are the main object of this work. The pervaporation of these solutions leads to the shifting of the composition from its chemical equilibrium. As a result, ester synthesis reaction coupled with pervaporation allows for more effective conversion of reagents. The hybrid process “reaction+pervaporation” was studied using membranes with a base of poly-(2,6-dimethyl-1,4-phenylene oxide) (PPO): a homogeneous PPO membrane and a composite membrane consisted of a PPO thin selective layer (~5µm) on the surface of a fluoroplastic composite hydrophobic membrane (MFFC). The transport properties of homogeneous and newly developed composite membranes based on the PPO were studied through the pervaporation of quaternary system acetic acid–methanol and water–methyl acetate. The sorption experiments were carried out to explain the pervaporation data. The possibility of using transformed composition variables for the analysis of pervaporation of mixtures in chemical equilibrium is demonstrated.It was shown that homogeneous and composite membranes are effective in shifting the esterification reaction equilibrium in pervaporation by the removal of methyl acetate or other esters from the reaction mixture. Composite membranes exhibited higher transport parameters (permeability and selectivity) than homogeneous membranes.

Determination of haloperidol in biological samples using molecular imprinted polymer nanoparticles followed by HPLC-DAD detection

In this study an extraction procedure using molecular imprinted polymer nanoparticles for the determination of haloperidol in biological samples is proposed. The haloperidol imprinted polymer nanoparticles were synthesized successfully by precipitation polymerization in a flask containing haloperidol as a template, ethyleneglycoldimethacrylate as a crosslinking agent, methacrylic acid as a functional monomer, and 2,2'-azobisisobutyronitrile as an initiator. The leached and unleached polymer nanoparticles have been characterized by infrared spectroscopy and scanning electron microscopy. The effect of different variables such as the pH of solution, uptake and elution time, type, and the least amount of eluent for elution of haloperidol from polymer was evaluated. Extraction efficiencies more than 97% were obtained by elution of the polymer with 1.5 mL of methanol-acetic acid-trifluoroacetic acid 79.9:20:0.1. Under optimal conditions maximum adsorption capacity was obtained 153.84 mg g(-1). The detection limit of the proposed procedure was between 0.2 and 0.35 μg L(-1). Finally this method was applied to the determination of haloperidol in plasma and urine samples and satisfactory results were achieved (RSD<6.9%).

11-Nor-9-carboxy-∆9-tetrahydrocannabinol quantification in human oral fluid by liquid chromatography–tandem mass spectrometry

Currently, ∆9-tetrahydrocannabinol (THC) is the analyte quantified for oral fluid cannabinoid monitoring. The potential for false-positive oral fluid cannabinoid results from passive exposure to THC-laden cannabis smoke raises concerns for this promising new monitoring technology. Oral fluid 11-nor-9-carboxy-∆9-tetrahydrocannabinol (THCCOOH) is proposed as a marker of cannabis intake since it is not present in cannabis smoke and was not measureable in oral fluid collected from subjects passively exposed to cannabis. THCCOOH concentrations are in the picogram per milliliter range in oral fluid and pose considerable analytical challenges. A liquid chromatography-tandem mass spectrometry (LCMSMS) method was developed and validated for quantifying THCCOOH in 1 mL Quantisal-collected oral fluid. After solid phase extraction, chromatography was performed on a Kinetex C18 column with a gradient of 0.01% acetic acid in water and 0.01% acetic acid in methanol with a 0.5-mL/min flow rate. THCCOOH was monitored in negative mode electrospray ionization and multiple reaction monitoring mass spectrometry. The THCCOOH linear range was 12-1,020 pg/mL (R(2) > 0.995). Mean extraction efficiencies and matrix effects evaluated at low and high quality control (QC) concentrations were 40.8-65.1 and -2.4-11.5%, respectively (n = 10). Analytical recoveries (bias) and total imprecision at low, mid, and high QCs were 85.0-113.3 and 6.6-8.4% coefficient of variation, respectively (n = 20). This is the first oral fluid THCCOOH LCMSMS triple quadrupole method not requiring derivatization to achieve a <15 pg/mL limit of quantification. The assay is applicable for the workplace, driving under the influence of drugs, drug treatment, and pain management testing.

Versatile reactivity of dioxaneferrocenylimine palladacycles by controlled acid hydrolysis. Crystal and molecular structure of [Pd{CpFe[η5-C5H2{CH(OMe)2}C(H)[dbnd]N-2,4,6-Me3C6H2]}(Cl)(PPh2Et)

Treatment of a or b with Li2[PdCl4] in methanol at room temperature for 48 h, gave the tetrametallic chlorine bridged complexes [Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)NR]}(μ-Cl)]2, 1a and 1b, containing a cyclic acetal on the metallated cyclopentadienyl ring. The reactions of 1a and 1b with the Ph2P(CH2)nPPh2 diphosphines in a 1:1 ratio gave the tetrametallic species [{Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)NR]}(Cl)}2(μ-Ph2P(CH2)nPPh2)], n = 1–4 as appropriate, 2a–5a and 2b–5b, with the diphosphine in a bridging mode and terminal chlorine ligands. Treatment of 1a and 1b with monophosphines yielded the dimetallic compounds [Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)NR]}(Cl)(L)] (L = PPh3, PPh2Me, PPh2Et) 6a–8a and 6b–7b. Reaction of the phosphine derivatives with aqueous acetic acid gave the corresponding functionalized compounds with transformation of the 1,3-dioxane ring into a formyl group on the metallated ring 9a–15a and 9b–14b. Reaction of 8a with acetic acid in methanol gave [Pd{CpFe[η5-C5H2{CH(OMe)2}C(H)N-2,4,6-Me3C6H2]}(Cl)(PPh2Et)] 16a, after a transacetalization reaction with an acetal moiety –CH(OMe)2 on the metallated five-membered ring. The molecular structure of compound 16a has been determined by X-ray diffraction analysis.

Fast determination of sulfonamides and their acetylated metabolites from environmental water based on magnetic molecularly imprinted polymers

Group-selective magnetic molecularly imprinted polymers (MMIPs) that can extract four widely used sulfonamide antibiotics and their acetylated metabolites from environmental water were synthesized in this study. The MMIPs with saturation magnetization value of 16.7 emu g(-1) could be separated from the environmental water samples easily by the application of an adscititious magnetic field, reducing the time consumption of pretreatment. The extraction conditions were evaluated, and optimal extraction conditions were as follows: extraction time, 25 min; amount of polymers, 90 mg; washing solvent, 30 % methanol aqueous solution; and elution solvent, methanol-acetic acid (95:5, v/v). The target analytes were detected by liquid chromatography-tandem mass spectrometry, and the detection limits of the method are in the range of 0.38-1.32 ng L(-1). The relative standard deviations of intra- and inter-day are in the range of 1.3-6.8 % and 1.7-9.1 %, respectively. The proposed method is suitable for the analysis of environmental water samples.

A simple method for the determination of fluoroquinolone residues in tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) employing LC-MS/MS QToF

The use of antimicrobials in livestock production is a powerful resource applied throughout the world to guarantee high yield and control bacterial diseases in aquaculture. However, residues of these substances in animal products represent a potential risk to consumer health when residue levels are above the established maximum residue limits (MRLs). Fluoroquinolones (FQs) are antimicrobials commonly used worldwide in aquaculture. The aim of this work was to develop and validate a simple analytical method for the simultaneous determination of norfloxacin, danofloxacin, enrofloxacin and ciprofloxacin levels in tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) fillets using liquid chromatography–tandem mass spectrometry (LC-MS/MS) quadrupole time of flight (QToF). The FQs were extracted from the fillets with 1% acetic acid–methanol and 1% acetic acid–acetonitrile solutions using ultrasonic assistance. The clean-up was performed with hexane. Chromatographic separation was conducted in an XTerra RP18 column (2.1 × 150 mm, 5 µm) at 25 °C with a flow of 0.2 mL min−1. The mobile phase consisted of 0.1% aqueous formic acid and acetonitrile, with gradient elution. The validation parameters for all FQs were linearity (>0.99), intra-day precision (CV of 1%–9%), inter-day precision (CV of 3%–17%), decision limit (63–126 ng g−1), detection capability (76 –152 ng g−1) and accuracy (90%–111%). The limit of quantification was lower than the MRL for each FQ, indicating that the method is suitable for the determination of the FQ levels in the fish fillets. The mass analyser of the QToF type was able to confirm the identities of the FQs with an error of the accuracy of the mass (reasons m/z) of less than 10 ppm.