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.     

Determination of three antidepressants in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction followed by gas chromatography–flame ionization detection

This paper presents a fast and simple method for the extraction, preconcentration and determination of fluvoxamine, nortriptyline and maprotiline in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction (TA‐DLLME) followed by gas chromatography–flame ionization detection (GC‐FID). An appropriate mixture of dimethylformamide (disperser solvent), 1,1,2,2‐tetrachloroethane (extraction solvent) and acetic anhydride (derivatization agent) was rapidly injected into the heated sample. Then the solution was cooled to room temperature and cloudy solution formed was centrifuged. Finally a portion of the sedimented phase was injected into the GC‐FID. The effect of several factors affecting the performance of the method, including the selection of suitable extraction and disperser solvents and their volumes, volume of derivatization agent, temperature, salt addition, pH and centrifugation time and speed were investigated and optimized. Figures of merit of the proposed method, such as linearity (r² > 0.993), enrichment factors (820–1070), limits of detection (2–4 ng mL^?1) and quantification (8–12 ng mL^?1), and relative standard deviations (3–6%) for both intraday and interday precisions (concentration = 50 ng mL^?1) were satisfactory for determination of the selected antidepressants. Finally the method was successfully applied to determine the target pharmaceuticals in urine. Copyright © 2014 John Wiley & Sons, Ltd.     

Development and validation of an HPLC method to quantify 3,4‐dideoxyglucosone‐3‐ene in peritoneal dialysis fluids

A method was developed and validated to quantify 3,4‐dideoxyglucosone‐3‐ene in peritoneal dialysis fluids by high‐performance liquid chromatography with UV detection after derivatization with o‐phenylenediamine. The advantages of this method compared with direct HPLC analysis are (i) the possibility of quantifying 3,4‐dideoxyglucosone‐3‐ene simultaneously together with other glucose degradation products, (ii) the compatibility of the method with MS detection for unequivocal identification of the analyte and (iii) a bathochromic shift of the UV absorbance maximum which leads to higher selectivity. The validated method was used to measure 3,4‐dideoxyglucosone‐3‐ene concentrations additionally to the glucose degradation products 3‐deoxyglucosone, methylglyoxal, glyoxal, 5‐hydroxymethylfurfural, 2‐furaldehyde, formaldehyde and acetaldehyde in 19 commercial products for peritoneal dialysis. Copyright © 2009 John Wiley & Sons, Ltd.     

Selective extraction of catecholamines by packed fiber solid‐phase using composite nanofibers composing of polymeric crown ether with polystyrene

For the first time, electrospun composite nanofibers comprising polymeric crown ether with polystyrene (PCE‐PS) have been used for the selective extraction of catecholamines – dopamine (DA), norepinephrine (NE) and epinephrine (E) – prior to their analysis by high‐performance liquid chromatography–electrochemical detection. Using a minicartridge packed with PCE‐PS composite nanofibers, the target compounds were extracted effectively from urine samples to which diphenylborinic acid 2‐aminoethyl ester was added as a complexing reagent. The extracted catecholamines could be liberated from the fiber by the addition of acetic acid. A good linearity was observed for catecholamines in the range of 2.0–200 ng mL^?1 (NE, E and DA). The detection limits of catecholamines (signal‐to‐noise ratio = 3) were 0.5 ng mL^?1 (NE), 0.2 ng mL^?1 (E) and 0.2 ng mL^?1 (DA), respectively. Under the optimized conditions, the absolute recoveries of the above three catecholamines were 90.6% (NE), 88.5% (E) and 94.5% (DA). The repeatability of extraction performance was from 5.4 to 9.2% (expressed as relative standard deviation). Our results indicate that the proposed method could be used for the determination of NE, E and DA in urine. Copyright © 2014 John Wiley & Sons, Ltd.     

Identification and quantification of six major α-dicarbonyl process contaminants in high-fructose corn syrup

High-fructose corn syrup (HFCS) is a widely used liquid sweetener produced from corn starch by hydrolysis and partial isomerization of glucose to fructose. During these processing steps, sugars can be considerably degraded, leading, for example, to the formation of reactive α-dicarbonyl compounds (α-DCs). The present study performed targeted screening to identify the major α-DCs in HFCS. For this purpose, α-DCs were selectively converted with o-phenylendiamine to the corresponding quinoxaline derivatives, which were analyzed by liquid chromatography with hyphenated diode array-tandem mass spectrometry (LC-DAD-MS/MS) detection. 3-Deoxy-D-erythro-hexos-2-ulose (3-deoxyglucosone), D-lyxo-hexos-2-ulose (glucosone), 3-deoxy-D-threo-hexos-2-ulose (3-deoxygalactosone), 1-deoxy-D-erythro-hexos-2,3-diulose (1-deoxyglucosone), 3,4-dideoxyglucosone-3-ene, methylglyoxal, and glyoxal were identified by enhanced mass spectra as well as MS/MS product ion spectra using the synthesized standards as reference. Addition of diethylene triamine pentaacetic acid and adjustment of the derivatization conditions ensured complete derivatization without de novo formation for all identified α-DCs in HFCS matrix except for glyoxal. Subsequently, a ultra-high performance LC-DAD-MS/MS method was established to quantify 3-deoxyglucosone, glucosone, 3-deoxygalactosone, 1-deoxyglucosone, 3,4-dideoxyglucosone-3-ene, and methylglyoxal in HFCS. Depending on the α-DC compound and concentration, the recovery ranged between 89.2% and 105.8% with a relative standard deviation between 1.9% and 6.5%. Subsequently, the α-DC profiles of 14 commercial HFCS samples were recorded. 3-Deoxyglucosone was identified as the major α-DC with concentrations up to 730 μg/mL HFCS. The total α-DC content ranged from 293 μg/mL to 1,130 μg/mL HFCS. Significantly different α-DC levels were not detected between different HFCS specifications, but between samples of various manufacturers indicating that the α-DC load is influenced by the production procedures.     

LC–MS/MS Determination of Catecholamines in Urine Using FMOC-Cl Derivatization on Solid-Phase Extraction Cartridge

A method for the determination of catecholamine derivatives in human urine is proposed that includes the derivatization of target compounds on a solid-phase extraction cartridge and determination of the analytes by a UHPLC method with tandem mass-spectrometric detection. 9-Fluorenyl-methoxycarbonyl chloride was used as the derivatization agent. The limits of detection for the analytes were 2.5 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-adrenaline, 5 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-octopamine, and 25 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-dopamine. The proposed procedure was tested on real samples obtained from volunteers.     

A Sensitive Electrochemical Immunosensor for α‐Fetoprotein Detection with Colloidal Gold‐Based Dentritical Enzyme Complex Amplification

A sensitive and specific electrochemical immunosensor was developed with α‐fetoprotein (AFP) as the model analyte by using gold nanoparticle label for enzymatic catalytic amplification. A self‐assembled monolayer membrane of mercaptopropionic acid (MPA) was firstly formed on the electrode surface through gold‐sulfur interaction. Monoclonal mouse anti‐human AFP was covalently immobilized to serve as the capture antibody. In the presence of the target human AFP, gold nanoparticles coated with polyclonal rabbit anti‐human AFP were bound to the electrode via the formation of a sandwiched complex. With the introduction of goat anti‐rabbit IgG conjugated with alkaline phosphatase, the dentritical enzyme complex was formed through selective interaction of the secondary antibodies with the colloidal gold‐based primary antibody at the electrode, thus affording the possibility of signal amplification for AFP detection. Current response arising from the oxidation of enzymatic product was significantly amplified by the dentritical enzyme complex. The current signal was proportional to the concentration of AFP from 1.0 ng mL^?1 to 500 ng mL^?1 with a detection limit of 0.8 ng mL^?1. This system could be extended to detect other target molecules with the corresponding antibody pairs.     

Highly Efficient Construction of Bisspirooxindoles Containing Vicinal Spirocenters through an Organocatalytic Modified Feist–Bénary Reaction

We have developed an organocatalytic modified Feist–Bénary reaction of cyclic dicarbonyl compounds, isatins and cyclic α‐bromo dicarbonyl compounds. This method affords bisspirooxindole‐fused dihydrofurans containing two vicinal spiro centers. To the best of our knowledge, employing cyclic α‐halo dicarbonyl compounds for the synthesis of bisspirooxindole‐fused dihydrofurans has not been previously reported.     

A Simple and Rapid High Performance Liquid Chromatographic Method with Fluorescence Detection for the Estimation of Amikacin in Plasma ‐ Application to Preclinical Pharmacokinetics

A simple and sensitive reversed‐phase liquid chromatographic method has been developed for the determination of amikacin by derivatization. The method is based on the pre‐column derivatization of amikacin with 9‐fluorenylmethyl chloroformate (FMOC‐Cl). Isepamicin was used as the internal standard. The derivatization reaction proceeds in aqueous solution at room temperature with a borate buffer of pH 7.3. The formation of the corresponding derivative of amikacin is instantaneous and it is stable for more than 48 h. Detection was performed by fluorescence. Several factors influencing the derivatization reaction yields were studied and optimized. The system offered the following analytical parameters: limit of detection (LOD) of 90 ng mL^?1 (3σ), linear correlation coefficient of 0.9998 and linear range response from 0.45 to 21.60 μg‐mL^?1. The precision of the method was < 6%. As a preliminary application, the method has been successfully applied to the amikacin determination in parenteral pharmaceutical formulations.     

Enantioselective Analysis of Amphetamine-Related Designer Drugs in Body Fluids Using Liquid Chromatography and Solid-Phase Derivatization

A method for the enantioselective determination of the amphetamine-derived designer drugs 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxyethylamphetamine (MDE) based on their derivatization with (-)-1-(9-fluorenyl)ethyl chloroformate (FLEC) is described. The proposed procedure entails preconcentration and derivatization of the analytes into C₁₈-packed solid-phase extraction cartridges, chromatographic separation of the diastereomers originated in a C₁₈ column under gradient elution, and UV detection at 265 nm. Compared with the solution derivatization approach the described procedure increased analyte responses by factors of 28–58. The reliability of the method has been tested by analysing plasma and urine samples spiked with the analytes in the 0.015–1.0 μg mL^?1 concentration interval. The proposed conditions provided adequate linearity, and coefficients of variation ranging from 5% to 14% in plasma, and from 3% to 12% in urine. The recoveries of the analytes were of 78%–126% and 78%–128% in plasma and urine, respectively. The limits of detection (LODs) obtained for all the analytes were 5 ng mL^?1 in both biological matrices.     

On-Fiber Derivatization of SPME Extracts of Phenol, Hydroquinone and Catechol with GC-MS Detection

A gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of phenol (PHE), hydroquinone (HQ) and catechol (CAT) in urine was developed and validated. The method was based on the acidic hydrolysis of conjugated phenolic compounds and further extraction of analytes using solid-phase microextraction (SPME). Analytes were extracted by submersing the polar polyacrylate coated fiber (85 μm) into urine (adjusted to pH 3.0 with glacial acetic acid) for 20 min with magnetic stirring. The extracted compounds on the fiber were exposed to hexamethyldisilazane reagent in the vapor phase for 20 min to yield the corresponding trimethysililylated derivates. This on-fiber derivatization procedure allowed the formation of more amenable compounds for GC analysis, without adversely affecting the lifetime of the fiber. The MS was operated in the selected ion monitoring mode (SIM). The limits of detection were 0.3 μg mL⁻¹ for PHE, 0.15 μg mL⁻¹ for HQ and 0.02 μg mL⁻¹ for CAT. Inter and intra-assay precisions were also verified (coefficient of variation < 8%) with the use of deuterated internal standards. This method of GC-MS analysis can be readily utilized to monitor PHE and its metabolites (HQ and CAT) in urine samples.     

Development of a Carbon Nanotube Modified Ionic Liquid Electrode for the Voltammetric Determination of Methyldopa Levels in Urine

A glassy carbon electrode was modified with carbon nanotubes and the ionic liquid N‐butyl pyridinium trifluoromethyl methanesulfonate for the determination of methyldopa in urine samples. Methyldopa exhibited a well‐defined anodic signal over a broad pH range of 2–10 and the peak current increased approximately 100 fold over that of the unmodified electrode. Accordingly, a novel method for the determination of methyldopa was proposed using differential pulse voltammetry. The peak current was linear over a methyldopa concentration range from 21 to 2111 ng mL^?1 with a LOD of 6.9 ng mL^?1 and a LOQ of 7.4 ng mL^?1. The method was applied to determine the excretion profile of methyldopa in urine without sample pretreatment.     

Chemo‐ and Enantioselective Oxidative α‐Azidation of Carbonyl Compounds

We report high‐performance I⁺/H₂O₂ catalysis for the oxidative or decarboxylative oxidative α‐azidation of carbonyl compounds by using sodium azide under biphasic neutral phase‐transfer conditions. To induce higher reactivity especially for the α‐azidation of 1,3‐dicarbonyl compounds, we designed a structurally compact isoindoline‐derived quaternary ammonium iodide catalyst bearing electron‐withdrawing groups. The nonproductive decomposition pathways of I⁺/H₂O₂ catalysis could be suppressed by the use of a catalytic amount of a radical‐trapping agent. This oxidative coupling tolerates a variety of functional groups and could be readily applied to the late‐stage α‐azidation of structurally diverse complex molecules. Moreover, we achieved the enantioselective α‐azidation of 1,3‐dicarbonyl compounds as the first successful example of enantioselective intermolecular oxidative coupling with a chiral hypoiodite catalyst.     

涂布2,4-二硝基苯肼的环形溶蚀器/滤膜系统和高效液相色谱法检测大气中二羰基化合物

建立了环形溶蚀器/滤膜系统(Annular denuder/filter pack system)和2,4-二硝基苯肼(DNPH)-高效液相色谱法(HPLC)采集和检测大气中气相和颗粒相二羰基化合物的方法。DNPH作为吸附剂分别涂布在环形溶蚀器的内壁和3层滤膜上,当大气样品经过环形溶蚀器时,含有气相二羰基化合物的气体吸附到环形溶蚀管内壁上与DN-PH发生反应,而颗粒相部分穿过环形溶蚀管,采集到滤膜上。样品经乙腈洗脱、浓缩后,采用HPLC进行分析。根据不同的采样流速、采样时间和DNPH的涂布量采集到的二羰基化合物的浓度,确定的最佳采样条件为:采样流速4 L/min,采样时间4~5 h,DNPH浓度0.47 g/L。使用Tedlar bag验证环形溶蚀器乙二醛和甲基乙二醛的采集效率(分别为82%和85%)。利用此方法对实际大气中的二羰基化合物进行了检测。     

Multi‐residue analysis of eight thioamphetamine designer drugs in human urine by liquid chromatography/tandem mass spectrometry

An analytical procedure for the simultaneous determination in human urine of several thioamphetamine designer drugs (2C‐T and ALEPH series) is reported. The quantitative analysis was performed by liquid chromatography/tandem mass spectrometry and has been fully validated. The mass spectrometer was operated in positive‐ion, selected reaction monitoring (SRM) mode. In order to minimize interferences with matrix components and to preconcentrate target analytes, solid‐phase extraction was introduced in the method as a clean‐up step. The entire method was validated for selectivity, linearity, precision and accuracy. The method turned out to be specific, sensitive, and reliable for the analysis of amphetamine derivatives in urine samples. The calibration curves were linear over the concentration range of 1 to 100 ng mL^?1 for all drugs with correlation coefficients that exceeded 0.996. The lower limits of detection (LODs) and quantification (LOQs) ranged from 1.2 to 4.9 ng mL^?1 and from 3.2 to 9.6 ng mL^?1, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

An Indirect Competitive Enzyme-linked Immunosorbent Assay for Simultaneous Determination of Florfenicol and Thiamphenicol in Animal Meat and Urine

A high-affinity polyclonal antibody was prepared by immunizing animals with haptens FFD and FFM. Under the optimal combination of coating antigen and antibody, an indirect competitive enzyme-linked immunosorbent assay (icELISA) for simultaneous detection of florfenicol and thiamphenicol residues in animal meat and urine samples was developed. The icELISA showed an IC₅₀ value of 1.32 ng mL^?1 for florfenicol and 2.13 ng mL^?1 for thiamphenicol, respectively. The linear ranges were from 0.31 to 5.61 ng mL^?1 with a limit of detection of 0.12 ng mL^?1 for florfenicol, and 0.41 to 11.2 ng mL^?1 with a limit of detection of 0.15 ng mL^?1 for thiamphenicol, respectively. The average recoveries of florfenicol and thiamphenicol in spiked samples ranged from 77.2% to 116.0% with a relative standard deviation of less than 15%. Therefore, this proposed icELISA provided a valid detection method for florfenicol and thiamphenicol residues in animal tissue and urine samples.     

An optimized method for the determination of volatile and semi-volatile aldehydes and ketones in ambient particulate matter

A method has been developed to measure aldehydes and ketones associated with atmospheric particles. Carbonyl compounds from particulate material collected on Teflon-coated glass-fiber filters were simultaneously extracted and derivatized with an appropriate 2,4-dinitrophenylhydrazine (2,4-DNPH) solution. The efficiency of this procedure utilizing various 2,4-DNPH concentrations and solvent compositions was studied for 13 carbonyl compounds of atmospheric importance. These include formaldehyde, acetaldehyde, acetone, dicarbonyls such as glyoxal and methylglyoxal, and biogenic carbonyls such as pinonaldehyde and nopinone. An extraction solution containing 3 × 10^?2 M 2,4-DNPH, in 60% acetonitrile/40% water, and pH 3 was most efficient in extracting and derivatizing these aldehydes and ketones (83-100% recovery). Improved sample enrichment and 2,4-DNPH purification methods were developed that afforded detection limits of 0.009-5.6 ng m^?3. The relative standard deviation for replicate analyses were 1.9-10.1%. Carbonyl compounds in ambient particulate samples were quantified during a recent field study. Median values for nine carbonyl species ranged from 0.01-33.9 ng m^?3 during the study.     

Porous carbon derived from a metal–organic framework as an efficient adsorbent for the solid‐phase extraction of phthalate esters

A porous carbon designated as MOF‐5‐C was prepared by directly carbonizing a metal–organic framework (MOF‐5). The morphology and microstructure of MOF‐5‐C were characterized by scanning electron microscopy, N₂ adsorption, and powder X‐ray diffraction. The MOF‐5‐C retained the original porous structures of MOF‐5, and showed a high Brunauer–Emmett–Teller surface area (1808 m² g^?1) and large pore volume (3.05 cm³ g^?1). To evaluate its adsorption performance, the MOF‐5‐C was used as an adsorbent for the solid‐phase extraction of four phthalate esters from bottled water, peach juice, and soft drink samples followed by high‐performance liquid chromatographic analysis. Several parameters that could affect the extraction efficiencies were investigated. Under the optimum conditions, a good linearity was achieved in the concentration range of 0.1–50.0 ng mL^?1 for bottled water sample and 0.2–50.0 ng mL^?1 for peach juice and soft drink samples. The limits of detection of the method (S/N = 3) were 0.02 ng mL^?1 for bottled water sample, and 0.04–0.05 ng mL^?1 for peach juice and soft drink samples. The results indicated that the MOF‐5‐C exhibited an excellent adsorption capability for trace levels of phthalate esters, and it could be a promising adsorbent for the preconcentration of other organic compounds.     

Simultaneous chiral separation and determination of carvedilol and 5′-hydroxyphenyl carvedilol enantiomers from human urine by high performance liquid chromatography coupled with fluorescent detection

A sensitive and specific high performance liquid chromatography coupled with fluorescent detection (HPLC-FL) and tandem mass spectrometry detection (HPLC-MS/MS) methods for separation and determination of carvedilol (CAR) enantiomers and 5′-hydroxyphenyl carvedilol (5′-HCAR) enantiomers has been developed and validated. The analysed compounds were extracted from human urine by solid phase extraction. Good enantioseparation of the studied enantiomers was achieved on CHIRALCEL® OD-RH column using 0.05% trifluoroacetic acid and 0.05% diethylamine in water and acetonitrile in a gradient elution. The mass spectrometric data were acquired using the multiple reaction monitoring mode by positive electrospray ionisation. The method was validated over the concentration range from 25.0 ng mL^?1 to 200 ng mL^?1 for the analysed compounds. The limit of quantification varied from 14.2 ng mL^?1 to 24.2 ng mL^?1. Both the repeatability and inter-day precisions were below 10.0%, and the accuracy varied from ?13.2% to 3.77%. The extraction recoveries ranged from 79.2% to 108%. The present paper reports the method for the simultaneous determination of CAR enantiomers and their metabolite enantiomers (5′-HCAR) in human urine samples. This newly developed method was successfully used to analyse the aforementioned analytes in human urine samples obtained from patients suffering from cardiovascular disease.      

A rapid LC-MS/MS method for determination of urinary EtG and application to a cut-off limit study

Ethyl glucuronide (EtG) is a metabolite and a specific marker of alcohol consumption that can be detected days after the complete elimination of alcohol after drinking. A rapid, simple, and sensitive LC-ESI-MS/MS method for the determination of urinary ethyl glucuronide was developed and fully validated in accordance with analytical standards, using the C₁₈ column. The whole process including sample preparation and LC-MS/MS lasted 10 min. A comprehensive validation including HorRat, measurement uncertainty, system suitability and intermediate precision calculations among analysts, and a cut-off limit study was performed. The method was applied to real samples and a cutoff limit determination study. The LOD and LOQ (using the IUPAC and Eurachem methods) were determined as 104.21 ng mL^?1 and 165.00 ng mL^?1. A cut-off limit of ≈ 818 ng mg^?1 (normalised to creatinine) was found for urinary EtG. The results showed that the cut-off limits currently in use should be re-considered in further studies and standardised on a global scale. Normalisation to creatinine is important because of the risk of the dilution of urine intentionally or with a change of diet. The concentrations of real samples from subjects who had consumed alcohol were successfully predicted using this method, after zero HS-GC/MS results of urine alcohol concentration.