Development of Immunoaffinity Sample-Purification for GC–MS Analysis of Ractopamine in Swine Tissue

A method combining immunoaffinity chromatography with gas chromatography–mass spectrometry (GC–MS) has been established for determination of ractopamine residues in swine liver and urine. After clean-up on an immunoaffinity chromatography column, GC–MS analysis revealed recovery from blank swine liver and urine fortified at 2.5–20 ng g^?1 (ng mL^?1 for urine), respectively, was 68.2–78.6 and 76.2–83.1%. The limits of detection and quantification were 0.5 ng g^?1 (or ng mL^?1) and 2.0 ng g^?1 (or ng mL^?1), respectively. The procedure was used for analysis of ractopamine residues in samples of swine liver and urine in which the levels were unknown. The amounts detected were 9–216 ng g^?1 (ng mL^?1).     

Capillary GC Analysis of Glyoxal and Methylglyoxal in the Serum and Urine of Diabetic Patients After Use of 2,3-Diamino-2,3-dimethylbutane as Derivatizing Reagent

The dicarbonyl compounds glyoxal, methylglyoxal, and dimethylglyoxal have been separated by capillary GC on a 30 m × 0.32 mm i.d. HP-5 column after precolumn derivatization with 2,3-diamino-2,3-dimethylbutane at pH 4. Chromatographic separation was complete in 6 min. Nitrogen was used as carrier gas at a flow rate of 2 mL min^?1. Split injection was performed with a split ratio of 10:1 (v/v). The derivatives were monitored by flame-ionization detection, and linear calibration plots were obtained in the ranges 0.06–0.69, 0.05–1.01, and 0.07–1.33 μg mL^?1 for glyoxal, methylglyoxal, and dimethylglyoxal, respectively; the respective detection limits were 20, 10, and 10 ng mL^?1. Glyoxal and methylglyoxal were analyzed in serum and urine from diabetics and from healthy volunteers. Amounts of glyoxal and methylglyoxal in serum from diabetic patients were 0.19–0.33 and 0.20–0.29 μg mL^?1, respectively, with respective relative standard deviations (RSD) of 0.8–1.0 and 0.8–1.1%. Amounts of glyoxal and methylglyoxal in serum from healthy volunteers were 0.05–0.08 and 0.04–0.10 μg mL^?1, respectively, with respective RSD of 0.9–1.2 and 1.0–1.2%. Levels of glyoxal and methylglyoxal in urine from diabetic patients were 0.18–0.40 and 0.25–0.36 μg mL^?1, respectively.     

On the Effect of Hydrogen Peroxide on the Flow‐Injection Determination of Platinum Based on Luminol Chemiluminescent Reaction

Abstract

A flow‐injection chemiluminescent (CL) method for the determination of trace amounts of Pt(IV) based on the oxidation reaction of luminol in alkaline solution is proposed. The effect of Pt(IV) on the oxidation of luminol was studied in the absence and in the presence of hydrogen peroxide. The positive effect of hydrogen peroxide as well as chloride ions on the sensitivity of measurements was observed. The developed method is characterized by a low limit of detection of Pt (LOD=0.06 ng mL^?1) and good reproducibility (RSD=2.2%). The addition of hydrogen peroxide to the reaction medium resulted in decreasing of platinum detection limit to 0.03 ng mL^?1.     

An Effective High-Performance Liquid Chromatographic–Mass Spectrometric Assay for Catecholamines, as the N(O,S)-Ethoxycarbonyl Ethyl Esters, in Human Urine

The purpose of this study was to develop a simple and accurate analytical method for determination of norepinephrine, epinephrine, and dopamine in urine. The method involves liquid–liquid extraction then liquid chromatography–mass spectrometry (LC–MS). Alkyl chloroformate derivatives were prepared, as the N(O,S)-alkoxycarbonyl alkyl esters of the analytes, in the aqueous samples. The optimum derivatizing reagent for preparation of the N(O,S)-alkoxycarbonyl alkyl esters was chosen by comparing the efficiency of LC of the derivatized analytes after liquid–liquid extraction. The optimum conditions for liquid–liquid extraction from the aqueous matrix were pH 3.0, no salt, and diethyl ether as extraction solvent. Limits of detection (LOD) were 0.5 ng mL^?1 for dopamine and epinephrine and 0.1 ng mL^?1 for norepinephrine. Limits of quantification (LOQ) for urine samples were 1.0 ng mL^?1 for all three compounds. The precision of intra- and inter-day assays was 1.65–581 and 7.17–9.73% (relative standard deviation, RSD), respectively. The range of inaccuracy for intra- and inter-day assays was ?6.47 to 11.9% and ?7.5 to 7.76% (bias) at concentrations of 5 and 50 ng mL^?1, respectively.     

Diphenyl diselenide grafted onto a Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-chitosan composite as a new nanosorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction

Diphenyl diselenide was immobilized on chitosan loaded with magnetite (Fe₃O₄) nanoparticles to give an efficient and cost-effective nanosorbent for the preconcentration of Pb(II), Cd(II), Ni(II) and Cu(II) ions by using effervescent salt-assisted dispersive magnetic micro solid-phase extraction (EA-DM-μSPE). The metal ions were desorbed from the sorbent with 3M nitric acid and then quantified via microflame AAS. The main parameters affecting the extraction were optimized using a one-at-a-time method. Under optimum condition, the limits of detection, linear dynamic ranges, and relative standard deviations (for n?=?3) are as following: Pb(II): 2.0 ng·mL^?1; 6.3–900 ng·mL^?1; 1.5%. Cd(II): 0.15 ng·mL^?1; 0.7–85 ng·mL^?1, 3.2%; Ni(II): 1.6 ng·mL^?1,.6.0–600. ng·mL^?1, 4.1%; Cu(II): 1.2 ng·mL^?1, 3.0–300 ng·mL^?1, 2.2%. The nanosorbent can be reused at least 4 times.

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Graphical abstract Fe₃O₄-chitosan composite was modified with diphenyl diselenide as a sorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.

     

Rabbit Monoclonal Antibody-Based Lateral Flow Immunoassay Platform for Sensitive Quantitation of Four Sulfonamide Residues in Milk and Swine Urine

Based on the available rabbit monoclonal antibody (RabMAb), a rapid and sensitive lateral flow immunoassay (LFA) platform has been developed for quantitative detection of four sulfonamide residues(SRs) of sulfadiazine (SD), sulfathiazole (STZ), sulfapyridine (SP), and sulfamethoxazole (SMX).Within the designed LFA competitive format assay, which was based on antigen-antibody properties, the hapten conjugate N¹-[4-(carboxymethyl)-2-thiazolyl] sulfanilamide linked to protein ovalbumin (TS-OVA) and goat anti-rabbit antibody were sprayed as capture and control reagents, respectively, and then the antibody was conjugated to colloidal gold particles as the detection reagent. With quantitative assessment aided by a colorimetric strip reader, the sensitivities of the established LFA method for SD, STZ, SP, and SMX were 0.91 ng mL^?1, 0.10ng mL^?1,0.12ng mL^?1, and 2.13ng mL^?1, and the half-maximum inhibition concentrations (IC₅₀) were 5.19 ng mL^?1, 1.25 ng mL^?1, 0.66 ng mL^?1, and 24.14 ng mL^?1, respectively. The recoveries at three spiked levels (5, 20, 50 ng mL^?1for SD, STZ, and SP; 20, 50, 100 ng mL^?1 for SMX) were in the range of 78.02–135.10% and 76.40–137.16% for milk and swine urine, respectively. More importantly, the detection performance of the established platform was consistent with that of in-parallel LC-MS/MS analysis. In conclusion, the proposed LFA platform has showed the potential for fast, sensitive and relatively accurate quantification of four sulfonamide residues in practical uses.     

Determination of 5-Hydroxytryptamine, Norepinephrine, Dopamine and Their Metabolites in Rat Brain Tissue by LC–ESI–MS–MS

A liquid chromatography–electrospray ionization tandem mass spectrometry method has been developed to perform the determination of 5-hydroxytryptamine (5-HT), norepinephrine (NE), dopamine (DA) and their metabolites, i.e., 5-hydroxyindole-3-acetic acid (5-HIAA), 4-hydroxy-3-methoxyphenylglycol (MHPG) sulfate, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in rat brain tissue. Analytes were separated on a Thermo C₁₈ column (4.6 mm × 250 mm, 5 μm, SN: 1245575T, Thermo electron corporation, USA) with a mobile phase of 0.05% formic acid/acetonitrile (92:8 for ESI⁺, 82:18 for ESI^?, v/v) at the flow-rate of 0.8 mL min^?1. The LC system was coupled to a Waters Micromass Quattro Premier XE tandem quadruple mass spectrometer. MS acquisition of 5-HT, NE and DA was performed in positive electrospray ionization multiple reaction monitoring (MRM) mode, while negative electrospray ionization MRM mode was used to monitor their metabolites. The calibration curves were linear within the concentration range of 4–4,450 ng mL^?1 for 5-HT, 4–4,110 ng mL^?1 for NE and 4–4,100 ng mL^?1 for DA (r ≥ 0.999). The limit of quantitation was 4 ng mL^?1. 5-HIAA, MHPG, DOPAC and HVA have good linearity within the range of 12–1,000 ng mL^?1(r ≥ 0.998) and the limit of quantitation was 12 ng mL^?1. The intra- and inter-day RSD were lower than 8.45%. The method is sensitive, fast, accurate and usable for quantity determination of monoamine neurotransmitters and their metabolites in neuropsychiatric diseases.     

Simultaneous Determination of Gallium(III) and Indium(III) in Urine and Water Samples with Cloud Point Extraction and by Inductively Coupled Plasma Optical Emission Spectrometry

A simple, sensitive, and selective method for the determination of gallium and indium in different samples at trace levels is presented. This method was based on complexation of analyzes with 2-(5-bromo-2- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in the presence of t-octylphenoxy-polyethoxyethanol (Triton X-100). After phase separation, the analyzed concentrations were determined by inductively coupled plasma optical emission spectrometry. Quantitative extraction of gallium and indium was performed at pH 7.0, 1.7 mmol L^?1, 5-Br-PADAP, 1.3% (w/v) Triton X-100 and at 75°C. The relative standard deviations (RSD) of this method were between 0.3% and 1.6% (C = 20 ng mL^?1, n = 9). The calibration curve is linear over the concentration range 6–200 ng mL^?1 for gallium and 2–200 ng mL^?1 for indium, respectively. The limits of detection (LOD) for gallium and indium were 0.72 and 0.28 ng mL^?1, respectively. The results showed the developed method was not susceptible to matrix effects, providing recoveries between 98% and 102%. The accuracy of the developed method was evaluated by the analysis of spiked certified reference materials. The developed method was successfully applied to gallium and indium determination in urine and lake water with satisfactory results.     

LC-MS-MS Method for Simultaneous Determination of Icariin and Its Active Metabolite Icariside II in Human Plasma

An LC-MS-MS method was revised and validated for simultaneous determination of icariin and its active metabolite icariside II in human plasma. The analytes and daidzein (IS) were extracted by liquid–liquid extraction and analyzed by LC-MS-MS. The separation was performed by a Zorbax SB-C₁₈ column (3.5 μm, 2.1 × 100 mm) with an isocratic mobile phase consisting of methanol–water–formic acid (65:35:0.035, v/v/v) at a flow rate of 0.25 mL min^?1. Detection was performed on a triple quadrupole tandem mass spectrum by multiple reaction monitoring mode using the electrospray ionization technique in positive mode. The method had lower limits of quantitation 0.2 and 0.1 ng mL^?1 for icariin and icariside II, respectively, using 500 μL plasma sample. The linear calibration curves were obtained in the concentration range of 0.2–100 ng mL^?1 for icariin and 0.1–100 ng mL^?1 for icariside II. The RSD values of intra- and inter-day precision calculated from quality control (QC) samples were less than 7.2% for icariin and less than 6.5% for icariside II. The accuracy as determined from QC samples was within 3.8% for each analyte. The method has been applied to determine and evaluate the pharmacokinetic of icariin and its metabolite icariside II in volunteers following oral administration of icariin and extract of Epimedium, respectively.     

Determination of Pantoprazole, Rabeprazole, Esomeprazole, Domperidone and Itopride in Pharmaceutical Products by Reversed Phase Liquid Chromatography Using Single Mobile Phase

A simple, sensitive, and precise high performance liquid chromatographic method for the analysis of pantoprazole, rabeprazole, esomeprazole, domperidone and itopride, with ultraviolet detection at 210 nm, has been developed, validated, and used for the determination of compounds in commercial pharmaceutical products. The compounds were well separated on a Hypersil BDS C18 reversed-phase column by use of a mobile phase consisting of 0.05 M, 4.70 pH, potassium dihydrogen phosphate buffer - acetonitrile (720:280 v/v) at a flow rate of 1.0 mL min^?1. The linearity ranges were 400–4,000 ng mL^?1 for pantoprazole, 200–2,000 ng mL^?1 for rabeprazole, 400–4,000 ng mL^?1 for esomeprazole, 300–3,000 ng mL^?1 for domperidone and 500–5,000 ng mL^?1 for itopride. Limits of detection (LOD) obtained were: pantoprazole 147.51 ng mL^?1, rabeprazole 65.65 ng mL^?1, esomeprazole 131.27 ng mL^?1, domperidone 98.33 ng mL^?1 and itopride 162.35 ng mL^?1. The study showed that reversed-phase liquid chromatography is sensitive and selective for the determination of pantoprazole, rabeprazole, esomeprazole, domperidone and itopride using single mobile phase.     

Simultaneous Determination of Levodopa, Benserazide and 3-O-Methyldopa in Human Serum by LC–MS–MS

For the first time a sensitive, specific and rapid LC–MS–MS assay is presented for the simultaneous determination of levodopa (L-DP), 3-O-methyldopa (3-OMD) and benserazide (BSZ) in human serum. The three compounds were extracted from human serum by protein precipitation followed by dilution of the supernatant with aqueous formic acid. In serum, linearity was observed between 50 and 1,000 ng mL^?1 of L-DP, 3-OMD and BSZ, respectively. Intra-day and inter-day RSD values were below 10.56 and 6.22% at concentrations of 120, 360 and 720 ng mL^?1. The presented method showed excellent specificity and sensitivity compared with other methods reported. It was applied to a pharmacokinetic study and demonstrated its applicability to pre-clinical and clinical pharmacological research.     

Separation and chromium speciation by single-wall carbon nanotubes microcolumn and inductively coupled plasma mass spectrometry

Microcolumn packed single-walled carbon nanotubes (SWCNTs) were used as solid phase extraction adsorbent for chromium speciation coupled to inductively coupled plasma mass spectrometry for detection. The effects of the experimental parameters, including pH of the solution, sample flow rate, volume and concentration of eluent, sample volume and interfering ions, on separation and determination of Cr(III) and Cr(VI) were investigated in detail. It was found that Cr(III) was selectively sorbed on the microcolumn packed with SWCNTs in the pH range from 2.0 to 4.0, while Cr(VI) remained in solution. The retained Cr(III) was subsequently eluted with 2.0 mL of 1.2 mol L^?1 nitric acid. Under the optimum conditions, the detection limits based on 3σ criterion were 0.01 ng mL^?1 and 0.024 ng mL^?1 for Cr(III) and Cr(VI), respectively. The relative standard deviations were less than 5.0% (n?=?9, c?=?1.0 ng mL^?1). The method was successfully applied to the speciation of chromium in real samples including natural and waste water. The recoveries of spiked samples were higher than 92.5%.     

Naked magnetite nanoparticles for both clean-up and solid-phase extraction-trace determination of mercury

A new solid-phase extraction method was developed for trace determination of Hg(II) by using a small amount of naked magnetite nanoparticles as an adsorbent. The magnetite nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The adsorbed Hg(II)-dithizone complex was eluted with 1.0 mL aliquot of an acidic 1-propanol solution prior to electrothermal atomic absorption spectrometry. A huge positive effect was found on the mercury adsorption by ionic strength. Under optimized condition, a linear calibration curve was obtained for mercury in the range of 0.2–50 ng mL^?1 with relative standard deviation in the range of 0.5–2.0%. The limit of detection and enrichment factor were 0.01 ng mL^?1 and 98.3, respectively. The effects of coexisting ions were studied extensively, and a new clean-up procedure was used to remove the matrix effects by using a simple sample pretreatment step using a little amount of magnetite nanoparticles. The method was successfully applied to the determination of Hg(II) in different water and human urine samples and a commercial sodium nitrate.     

Online Purification and Screening of Nisoldipine with a Novel Poly(vinyl ester) Resin Monolithic Column

A monolithic column, prepared from a vinyl ester resin used as both monomer and cross-linking agent, has been used to remove matrix compounds from biological fluid. Using this column, nisoldipine in human plasma samples could be enriched online and the protein could be eluted. For this method of extraction, response (peak area) was a linear function of concentration in the range 2–80 ng mL^?1, with a linear regression coefficient of 0.99985. The limit of detection for nisoldipine in plasma was 1.2 ng mL^?1. For nisoldipine at concentrations of 10, 30, and 70 ng mL^?1 RSD were 4.33, 6.63, and 4.57%, respectively. Recovery for both extraction (>73.6%) and the entire analytical method (>90.7%) were acceptable for screening of plasma for nisoldipine. The 12-hour pharmacokinetic profile of nisoldipine in mice after oral administration (0.3 mg kg^?1) was investigated. The results indicated the method could be used for therapeutic monitoring of nisoldipine and enabled simple and rapid assay of the drug in plasma.     

Removal, preconcentration and spectrophotometric determination of U(VI) from water samples using modified maghemite nanoparticles

Arsenazo III modified maghemite nanoparticles (A-MMNPs) was used for removing and preconcentration of U(VI) from aqueous samples. The effects of contact time, amount of adsorbent, pH and competitive ions was investigated. The experimental results were fitted to the Langmuir adsorption model in the studied concentration range of uranium (1.0 × 10^?4–1.0 × 10^?2 mol L^?1). According to the results obtained by Langmuir equation, the maximum adsorption capacity for the adsorption of U(VI) on A-MMNPs was 285 mg g^?1 at pH 7. The adsorbed uranium on the A-MMNPs was then desorbed by 0.5 mol L^?1 NaOH solution and determined spectrophotometrically. A preconcentration factor of 400 was achieved in this method. The calibration graph was linear in the range 0.04–2.4 ng mL^?1 (1.0 × 10^?10–1.0 × 10^?8 mol L^?1) of U(VI) with a correlation coefficient of 0.997. The detection limit of the method for determination of U(VI) was 0.01 ng mL^?1 and the relative standard deviation (R.S.D.) for the determination of 1.43 and 2.38 ng mL^?1 of U(VI) was 3.62% and 1.17% (n = 5), respectively. The method was applied to the determination of U(VI) in water samples.     

Colorimetric Determination of Lead Using Gold Nanoparticles

A combined homogeneous assay and colorimetric determination method using gold nanoparticles was developed for rapid determination of lead(II) in contaminated natural waters. The presence of lead(II) in the colloidal gold suspension causes a change in the absorbance of the suspension. An increase in the absorption property at 595 nm is accompanied by a change in the size of the gold nanoparticles. High concentrations of lead cause aggregation of the gold colloids. Colloidal gold nanoparticles were synthesized using tannic acid as the reducing agent; this reagent allowed selective determination of lead in 10 µL of water, with a detection limit of 310 ng mL^?1 with an analysis time of 5 min. The coefficient of variation for lead(II) within the working range of the assay (520 ng mL^?1–13 µg mL^?1) varied from 1.3% to 9.2%. The limit of detection using this method with a sample volume of 50 µL was 60 ng mL^?1. The coefficient of variation for lead over the working range of the determined concentrations (80 ng mL^?1–25 µg mL^?1) varied from 0.2% to 9.3%, while the values for the inter-day assay (n = 8) were less than 10%. The method was employed for the analysis of river, lake, marsh, and spring water; the recovery of lead was determined to be 72.5%–130% for 10 µL of water and 93.6%–114.7% for 50 µL.     

A novel chemiluminescence reaction system for the determination of lincomycin with diperiodatonickelate(IV)

A sensitive and high selective chemiluminescence (CL) method was developed for the determination of lincomycin in acid medium using diperiodatonickelate as a reagent. The mechanism leading to luminescence is discussed by comparing the spectra of fluorescence and CL. Relative CL intensity is linear in the range from 8.0 ng mL^?1 to 1.0 µg mL^?1, the limit of detection is 2.5 ng mL^?1 (3σ), and the relative standard deviation is 4.0% at 0.1 µg mL^?1 of lincomycin (n?=?7). The method was successfully applied to the determination of lincomycin in injections, human urine, and in serum samples.     

Solvent Bar Microextraction with HPLC for Determination and Protein-Binding Characteristics of Oleanolic Acid and Ursolic Acid

An improved solvent bar microextraction (SBME) combined with HPLC was applied to rapidly determine oleanolic acid (OA) and ursolic acid (UA) in Chinese medicinal herbs (CMHs), and to investigate drug–protein binding. Variables influencing SBME were investigated and optimized. Under optimal conditions, the linear ranges of 3.6–1,820 ng mL^?1 for OA and 4.2–2,080 ng mL^?1 for UA were obtained with square correlation coefficients of 0.9996 and 0.9997, respectively. The detection limits were 1.3 ng mL^?1 for OA and 1.5 ng mL^?1 for UA. The relative standard deviations were lower than 9.4 %. The protein-binding rates, the numbers of binding sites, and the binding constants of OA and UA were also obtained via the method. It has been demonstrated that SBME can not only be a simple, rapid and efficient sample preparation method for determination of active components from CMHs but also be a potential research protocol for protein-binding interactions.     

Determination of Tangeretin in Rat Plasma by LC-Electrospray-Ion Trap MS

A selective, sensitive, and accurate method has been developed and validated for the quantification of tangeretin in rat plasma. The application of LC-electrospray-ion trap mass spectrometry in full scan and multiple reactions monitoring modes were investigated. Following solid phase extraction using a hydrophilic–lipophilic balance cartridge, the analytes were separated on a C₁₈ column using an isocratic mobile phase composed of acetonitrile/water (50:50, v/v) containing 0.3% formic acid. In full scan mode, the LOQ was 2 ng mL^?1. The standard calibration curve was linear (R ² = 0.9999) over the concentration range 2–200 ng mL^?1. The precision over the concentration range was within 15% (RSD) and the accuracy was ranged from 86 to 115%. In multiple reaction monitoring mode, the LOQ was 1 ng mL^?1 and the standard calibration curve was linear (R ² = 0.9976) over the concentration range 1–100 ng mL^?1 with a precision of 12% and accuracy rangeing from 91 to 113%.     

Nonextractive Trace Level Simultaneous Determination of Mercury(II) and Zinc(II) in Environmental Samples with 2‐(5‐Bromo‐2‐pyridylazo)‐5‐diethylaminophenol and Cetylpyridinium Chloride

Abstract

A simple, rapid, selective, and sensitive method for the derivative spectrophotometric determination of Hg(II) and its simultaneous determination in the presence of Zn(II) using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant, has been developed. The molar absorption coefficient and analytical sensitivity of the 1∶1 Hg(II) complex at 558 nm (λ_max) are 5.78×10⁴ L mol^?1 cm^?1 and 0.67 ng mL^?1, respectively. The detection limit of Hg(II) is 1.40×10^?2 ng mL^?1, and Beer's law is valid in the concentration range 0.05–2.40 µg mL^?1. Overlapping spectral profiles of Hg(II) and Zn(II) complexes in zero‐order mode interfere in their simultaneous determination. However, 0.10–2.00 µg mL^?1 of Hg(II) and 0.065–0.650 µg mL^?1 of Zn(II), when present together, can be simultaneously determined at zero cross point of the derivative spectrum, without any prior separation. The relative standard deviation for six replicate measurements of solutions containing 0.134 µg mL^?1 of Hg(II) and 0.620 µg mL^?1 of Zn(II) is 1.72 and 1.47%, respectively. The proposed method has successfully been evaluated for trace level simultaneous determination of Hg(II) and Zn(II) in environmental samples.