Real Human Urine Samples Research Articles

Development and Application of a Sensor Based on Carbonaceous Materials and Cobalt Phthalocyanine Composite for Electrochemical Determination of Uric Acid

AbstractIn the present paper a voltammetric sensor based on glassy carbon electrode (GCE) and cobalt phthalocyanine (CoPc)/multiwalled carbon nanotube (MWCNT) composite has been successfully prepared for uric acid (UA) determination in real samples. The electrochemical behavior of UA at the GCE‐CoPc/MWCNT has been evaluated by employing cyclic voltammetry. The charge transfer coefficient, α, and the charge transfer rate constant, κs, for electron transfer between CoPc/MWCNT and GCE were calculated as 0.49 and 19.5±0.51 s−1, respectively. Under optimized conditions (pH 7.0 in 0.10 mol L−1 phosphate buffer) the best technique was the square wave voltammetry and responds linearly to UA from 0.2 up to 1.0 mmol L−1 (r=0.997) and 1.25 up to 4.0 mmol L−1 (r=0.991) with limits of detection and quantification of 0.26 and 0.86 mmol L−1, respectively. The developed method was successfully applied for UA determination in real samples of human urine. The modified electrode exhibits sensitive and stable responses and does not show interferences in presence of dopamine and ascorbic acid.

Analytical approach to determining human biogenic amines and their metabolites using eVol microextraction in packed syringe coupled to liquid chromatography mass spectrometry method with hydrophilic interaction chromatography column

Analysis of biogenic amines (BAs) in different human samples provides insight into the mechanisms of various biological processes, including pathological conditions, and thus may be very important in diagnosing and monitoring several neurological disorders and cancerous tumors. In this work, we developed a simple and fast procedure using a digitally controlled microextraction in packed syringe (MEPS) coupled to liquid chromatography mass spectrometry (LC–MS) method for simultaneous determination of biogenic amines, their precursors and metabolites in human plasma and urine samples. The separation of 12 low molecular weight and hydrophilic molecules with a wide range of polarities was achieved with hydrophilic interaction chromatography (HILIC) column without derivatization step in 12min. MEPS was implemented using the APS sorbent in semi-automated analytical syringe (eVol®) and small volume of urine and plasma samples, 50µL and 100μL, respectively. We evaluated important parameters influencing MEPS efficiency, including stationary phase selection, sample pH and volume, number of extraction cycles, and washing and elution volumes. In optimized MEPS conditions, the analytes were eluted by 3×50μL of methanol with 0.1% formic acid. The chromatographic separation of analytes was performed on XBridge Amide™ BEH analytical column (3.0mm×100mm, 3.5µm) using gradient elution with mobile phase consisting of phase A: 10mM ammonium formate buffer in water pH 3.0 and phase B: 10mM ammonium formate buffer in acetonitrile pH 3.0. The LC–HILIC–MS method was validated and, in optimum conditions, presented good linearity in concentration range within 10–2000ng/mL for all the analytes with a determination coefficient (r2) higher than 0.999 for plasma and urine samples. Method recovery ranged within 87.6–104.3% for plasma samples and 84.2–98.6% for urine samples. The developed method utilizing polar APS sorbent along with polar HILIC column was applied for simultaneous bioanalysis of trace amounts of polar endogenous biogenic amines in real human urine and plasma samples.

Polyfurfural film modified glassy carbon electrode for highly sensitive nifedipine determination

ABSTRACT A sensitive and convenient electrochemical strategy is developed for the determination of nifedipine basing on a polyfurfural film modified glassy carbon electrode (GCE) by the one-step electropolymerization of furfural. The prepared polyfurfural film/GCE exhibits excellent electrocatalytic activity towards nifedipine. A series of experimental parameters including the pH of supporting electrolyte, accumulation time and potential for nifedipine is also considered and optimized. Under optimal conditions, the proposed nifedipine sensor has a wide linear detection range from 1 × 10 −8 to 7 × 10 −6 mol dm −3 , with a low detection limit of 5 × 10 −9 mol dm −3 . The proposed nifedipine sensor also displays excellent selectivity, stability and reproducibility. In particular, it shows splendid analytical performance for the determination of nifedipine in real pharmaceutical and human urine samples in practice.

On-line preconcentration strategy for the simultaneous quantification of three local anesthetics in human urine using CZE.

The simultaneous determination of usually employed anesthetics (procaine, lidocaine, and bupivacaine) has been developed and validated using CE with ultraviolet detection at 212 nm. The separation of these three drugs has been achieved in less than 7 min, using a temperature of 25ºC and 25 kV, with a 150 mM citrate buffer (pH 2.5) as BGE. Field-amplified sample injection (FASI) has been used for on-line sample preconcentration. Ultrapure water and ACN 50/50 (v/v) mixture gave the greatest enhancement factor when it was employed as an injection solvent. Injection voltage and time were optimized, being 13 kV and 13 s, the optimum values, respectively. To avoid the possible irreproducibility associated with the electrokinetic injection, an internal standard such as tetracaine, was employed. The instrumental detection limits (LOD S/N = 3) for the compounds ranged between 2.6 and 7.0 μg L(-1) and the quantitation limits (LOQ S/N = 10) between 37.8 and 55.9 μg L(-1) . The detection limits obtained in real human urine samples ranged between 55.2 and 83.6 μg L(-1) and the quantitation limits between 196.0 and 276.0 μg L(-1) . The proposed method has demonstrated its applicability to the analysis of these local anesthetics in urine samples without any pretreatment, allowing the rapid determination of these target analytes.

Two low-cost digital camera-based platforms for quantitative creatinine analysis in urine

In clinical analysis creatinine is a routine biomarker for the assessment of renal and muscular dysfunctions. Although several techniques have been proposed for a fast and accurate quantification of creatinine in human serum or urine, most of them require expensive or complex apparatus, advanced sample preparation or skilled operators. To circumvent these issues, we propose two home-made platforms based on a CD Spectroscope (CDS) and Computer Screen Photo-assisted Technique (CSPT) for the rapid assessment of creatinine level in human urine. Both systems display a linear range (r2 = 0.9967 and 0.9972, respectively) from 160 μmol L−1 to 1.6 mmol L−1 for standard creatinine solutions (n = 15) with respective detection limits of 89 μmol L−1 and 111 μmol L−1. Good repeatability was observed for intra-day (1.7–2.9%) and inter-day (3.6–6.5%) measurements evaluated on three consecutive days. The performance of CDS and CSPT was also validated in real human urine samples (n = 26) using capillary electrophoresis data as reference. Corresponding Partial Least-Squares (PLS) regression models provided for mean relative errors below 10% in creatinine quantification.

Graphene/Cu nanoparticle hybrids fabricated by chemical vapor deposition as surface-enhanced Raman scattering substrate for label-free detection of adenosine.

We present a graphene/Cu nanoparticle hybrids (G/CuNPs) system as a surface-enhanced Raman scattering (SERS) substrate for adenosine detection. The Cu nanoparticles wrapped by a monolayer graphene shell were directly synthesized on flat quartz by chemical vapor deposition in a mixture of methane and hydrogen. The G/CuNPs showed an excellent SERS enhancement activity for adenosine. The minimum detected concentration of the adenosine in serum was demonstrated as low as 5 nM, and the calibration curve showed a good linear response from 5 to 500 nM. The capability of SERS detection of adenosine in real normal human urine samples based on G/CuNPs was also investigated and the characteristic peaks of adenosine were still recognizable. The reproducible and the ultrasensitive enhanced Raman signals could be due to the presence of an ultrathin graphene layer. The graphene shell was able to enrich and fix the adenosine molecules, which could also efficiently maintain chemical and optical stability of G/CuNPs. Based on the G/CuNPs system, the ultrasensitive SERS detection of adenosine in varied matrices was expected for the practical applications in medicine and biotechnology.

Bianalyte multicommutated flow analysis system for microproteinuria diagnostics

In this work a bianalyte multicommutated flow analysis (MCFA) system for determination of microproteinuria is presented. The developed MCFA system is based on two dedicated optoelectronic flow-through detectors which allow estimation of urinary protein creatinine ratio. For total protein determination, turbidimetric Exton's method was used, whereas creatinine was determined by the photometric Jaffe reaction. The developed analytical system is fully-mechanized, easy to operate, economic in reagent consumption and characterized by satisfactory analytical parameters. It allows protein determination in the range 36–300mgL−1 with 33mgL−1 detection limit and simultaneous determination of creatinine in the range 0.045–2.50mmolL−1 with 0.025mmolL−1 detection limit. The measurement procedure for the presented MCFA system offers performing 30 peaks per hour for both analytes. To prove the analytical usefulness of the system, real human urine samples have been analyzed. The correlation and agreement between results offered by the developed system and clinical analyzers are fully acceptable.

Ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction for the determination of eight drugs in biological samples by gas chromatography-triple quadrupole mass spectrometry

A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction (UA-LDS-DLLME) has been developed for the determination of multiple drugs of abuse in biological samples by gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS). A total of 100 µL of toluene as extraction solvent was dropped into the sample solution. Then the mixture was sonicated drastically in an ultrasonic bath for 3 min with occasional manual shaking to form a cloudy suspension. After centrifugation at 10,000 r/min for 3 min, the upper layer of low-density extractant was withdrawn and injected into the GC-QQQ-MS for analysis. The parameters affecting extraction efficiency have been investigated and optimized. Under the optimum conditions, good linearities were observed for all analytes with the correlation coefficients ranging from 0. 998 4 to 0. 999 4. The recoveries of 79.3%-100.3% with RSDs < 5.7% were obtained. The LODs (S/N = 3) were in the range from 0.05 to 0.40 µg/L. UA-LDS-DLLME technique has the advantages of less extraction time, suitable for batches of sample pretreatment simultaneously, and higher extraction efficiency. It was successfully applied to the analysis of amphetamines in real human urine samples.

Ultrasound-Assisted Low-Density Solvent Dispersive Liquid-Liquid Extraction for the Determination of Amphetamines in Biological Samples Using Gas Chromatography-Mass Spectrometry

In order to control drug crime effectively, it is necessary to develop selective analytical methods suitable for unambiguous identification and determination of drugs in illicit samples and biological matrices. A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction, (UA-LDS-DLLME) has been applied to the determination of four amphetamines (methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine, and 3,4-methylenedioxyamphetamine) in urine samples by gas chromatography-mass spectrometry. The parameters affecting extraction efficiency have been investigated and optimized. UA-LDS-DLLME used ultrasound energy to assist in the emulsification process without any disperser solvent. Under the optimized conditions, linearity was observed for all analytes in the 0.15–10 μg/mL range with correlation coefficients (R) ranging from 0.9886 to 0.9894. The recoveries of 75.6–91.4% with relative standard deviations of 2.5–4.0% were obtained. The limits of detection (S/N = 3) were estimated to be in the 5–10 ng/mL range. The UA-LDS-DLLME technique had the advantages of shorter extraction time, suitability for simultaneous pretreatments of batches of samples, and the higher extraction efficiency. It was successfully applied to the analysis of amphetamines in real human urine samples.

Coupling of solid phase microextraction with electrospray ionization ion mobility spectrometry and direct analysis of venlafaxine in human urine and plasma

The capability of electrospray ionization-conventional ion mobility spectrometry (ESI–IMS) for direct analysis of the samples extracted by solid phase microextraction (SPME) was investigated and evaluated for the first time. To that end, an appropriate new desorption chamber was designed and constructed, resulting in the possibility of direct exposure of the SPME fiber to the electrospray solvent flow. Two different elution methods in dynamic and static modes were exhaustively investigated. The results indicated that the interface could help us to have an accurate and sensitive analysis without disturbing the electrospray process, in static elution method. Venlafaxine as a test compound was extracted from human urine and plasma by a convenient headspace SPME method. The positive ion mobility spectrum of the extracted drug was obtained and the analyte responses were calculated. The coupled method of SPME–ESI–IMS was comprehensively validated in terms of sensitivity, dynamic range, and recovery percentage. Finally, various real samples of human urine and plasma were analyzed, all verifying the feasibility and success of the proposed method for the easy routine analysis.

Applied Technology in Diaper-Based UTI Testing for Elder People by Using Nitrite Ion Selective Electrode

Urinary tract infections (UTI) are common infection diseases in the hospitals, especially for the elder people. Detecting UTI for the elder people is difficult and time-consuming procedure. Since measuring nitrite directly in urine is often employed in the diagnosis of UTI, a nitrite ion selective electrode (ISE) was investigated in this study in order to detect UTI samples directly on used diapers of patients. With a commercial ISE sensor for nitrite, the detecting system was built to quickly and precisely quantify different concentrations of nitrite ions in both water solutions and real human urine samples. Good results were shown in the experiment that the nitrite can be precisely detected in the fresh urine by the ISE with the relations as Ε=224.7-21.259×Lg (C+13.476), where E is the electrode potential and C is the concentration of nitrite ions. Besides, the method of extracting urine samples from used diapers was also studied for further research. The investigation suggested that a sampling module for used diapers could be simply realized if necessary.

Combination of a sub-3μm superficially porous particle packed column with charged aerosol detection for the simple and sensitive measurement of nine macrolides in human urine.

Due to the lack of chromophores in many macrolides, analytical methods based on mass spectrometry and electrochemical detection coupled to liquid chromatography have been suggested to be suitable for the quantification of macrolides in complex matrices. In this study, a simple and sensitive analytical method was established for the simultaneous measurement of nine macrolides in human urine by combining a sub-3μm superficially porous particle packed column with charged aerosol detection. After thorough investigation of various sample preparation methods, including two liquid-liquid extraction methods and four solid-phase extraction methods, HLB solid-phase extraction was selected and further optimized. Absolute recovery of the optimized sample preparation method ranged from 99.5-110.2%, indicating its very high extraction/clean-up efficiency. For chromatography, parameters influencing macrolide separation were systematically optimized, and the resulting conditions allowed baseline separation of nine macrolides within 24min using a very simple mobile phase. The established method was validated for linearity, limit of detection, limit of quantification, absolute recovery, and precision. Based on its limit of detection (0.025-0.100μg/mL), the method had similar or greater sensitivity than most methods based on electrochemical detection. It was found that the current method was appropriate for application to real human urine samples after drug administration.

Application of Ionic Liquid-based Nanofluids Containing Gold Nanoparticles in an Electrochemical Sensor for Uric Acid

Abstract Under ultrasonic dispersing, an ionic liquid-based nanofluid was prepared by extraction–reduction method using 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) as medium, poly(vinylpyrrolidone) as an extractant and a dispersant, and gold nanoparticles (AuNPs) as nanoparticles. A new electrochemical sensor for detecting uric acid (UA) was fabricated by immobilizing the ionic liquid-based nanofluids containing AuNPs on a glassy carbon electrode surface. This sensor exhibited good selectivity, reproducibility, and sensitivity for the direct determination of UA in real human urine samples.

Using a postcolumn-infused internal standard for correcting the matrix effects of urine specimens in liquid chromatography–electrospray ionization mass spectrometry

Matrix effects (MEs) are a major problem affecting the quantitative accuracy of liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) when analyzing complicated samples. While analyzing urine specimens, the wide diversity of endogenous materials and different urine concentrations may result in inaccurate quantification. In this study, we propose a postcolumn-infused internal standard (PCI-IS) strategy for universal correction of MEs in urine specimens. MEs can be effectively corrected by dividing the target analyte signal intensity by the PCI-IS intensity. To evaluate the performance of PCI-IS, we used 6 benzodiazepine (BZD) drugs in 5 different concentrations of urine matrixes as a test model. The divergence of the BZD drug signal responses in 5 different urine matrixes was expressed using their respective coefficients of variation (CV) to evaluate the efficiency of using PCI-IS in correcting matrix effects. The CV of the BZD drug signal intensities in these 5 different concentrations of the urine matrixes were reduced from 10 to 30% to less than 10% when the PCI-IS correction method was employed. When the PCI-IS method was used to correct the 6 BZDs in 25 real human urine samples, over 90% of the test results exhibited quantification errors of less than 20%, and all of the test results had quantification errors of less than 30%. These results demonstrate that the PCI-IS method can resolve the problem of inaccurate quantification that arises from the diversity of urine specimens. The PCI-IS method is particularly useful for clinical analysis or forensic toxicology to improve the quantification accuracy in an economical way.

Electrochemical determination of ascorbic acid, dopamine and uric acid based on an exfoliated graphite paper electrode: A high performance flexible sensor

An exfoliated flexible graphite paper (e-FGP) with rough edges is proposed as a high performance working electrode for the electrochemical determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Scanning electron microscopy (SEM), cyclic voltammetry (CV), different pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were applied to investigate the unique properties of the high performance electrode. The results demonstrate its excellent electrocatalytic activity toward the oxidation of AA, DA and UA with well-separated voltammetric peaks. The calibration curves in the range of 20–400μM, 0.5–35μM, 0.5–35μM, and the detection limits (S/N=3) of 2.0μM, 0.01μM, 0.02μM were obtained for AA, DA and UA in neutral phosphate buffer solutions (PBS), respectively. This mechanically flexible sensor with good selectivity and remarkable sensitivity could be used to determine DA and UA in real human urine samples.

Multicommutated flow analysis system for determination of creatinine in physiological fluids by Jaffe method

For the needs of photometric determination of creatinine according to Jaffe protocol a dedicated paired emitter detector diode (PEDD) detector has been developed. This PEDD device has been constructed in the compact form of flow-through cell (30μL total volume and 7mm optical pathlength) integrated with 505nm LED-based emitter and 525nm LED-based detector compatible with multicommutated flow analysis (MCFA) system. This fully mechanized MCFA system configured of microsolenoid valves and pumps is operating under microprocessor control. The developed analytical system offers determination of creatinine in the submillimolar range of concentrations with detection limit at ppm level. The throughput offered by the system operating according to multi-point fixed-time procedure for kinetic measurements is 15–40 samples per hour depending on the mode of measurements. The developed PEDD-based MCFA system has been successfully applied for the determination of creatinine in real samples of human urine as well as serum. The developed sampling unit used the system is free from effects caused by differences in sample viscosity.

Electrochemical detection of dopamine using water-soluble sulfonated graphene

In the present study, a biosensor was prepared using the water-soluble sulfonated graphene with the aim of achieving the selective and sensitive determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). The aromatic π–π stacking and electrostatic attraction between positively charged DA and negatively charged sulfonated graphene can accelerate the electron transfer whereas weakening AA and UA oxidation on the sulfonated graphene-modified electrode. Fourier transform infrared spectra (FTIR), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the successful synthesis of sulfonated graphene sheets. Differential pulse voltammetry was used for electrochemical detection, the separation of the oxidation peak potentials for AA-DA, DA-UA and UA-AA was about 227mV, 125mV and 352mV, which allowed selectively determining DA. A broad linear range, low detection limit, along with good ability to suppress the background current from large excess ascorbic acid (AA) and uric acid (UA) were obtained. The as-prepared sulfonated graphene sheets exhibited superior performance over conventional negatively charged Nafion films, such as flexible film thickness, unique nanostructure, excellent anti-interference ability, high sensitivity and selectivity. The proposed method was used to detect DA in real hydrochloride injection sample, human urine and serum samples with satisfactory recovery results.

Determination of chlorpyrifos’ main metabolite 3,5,6-trichloro-2-pyridinol in human urine by ultra performance liquid chromatography coupled with tandem mass spectrometry

A method for the determination of 3,5,6-trichloro-2-pyridinol (3,5,6-TCP) in human urine, which is the main metabolite of chlorpyrifos, has been established employing ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/ MS). The urine samples were prepared by liquid-liquid extraction with dichloromethane-ethyl acetate (20: 80, v/v) solution followed by the separation with the gradient elution of acetonitrile-water on an ACQUITY UPLC BEH C18 column. The analyte was detected by tandem mass spectrometry under the negative ion mode with the electrospray ionization (ESI) source and the selective ion recording (SIR) mode. Under the optimized conditions, the calibration curve was linear in the range of 0.005 -0.4 mg/L. The limit of detection was 0.41 microg/L. The average recovery was 97.9%. The intra- and inter-day precisions calculated with RSDs were all within 15% at each quality control (QC) level. The developed method is simple, sensitive, accurate and repeatable, which has been successfully applied to determine the exposure level of 3,5,6-TCP in the real samples of human urine. The results show that this method is supportive for the exposure assessment in human health risk analysis and monitoring the biological burden of chlorpyrifos.

A simple one-pot synthesis of graphene nanosheet/SnO2 nanoparticle hybrid nanocomposites and their application for selective and sensitive electrochemical detection of dopamine.

A novel one-pot synthesis of graphene nanosheet/SnO2 nanoparticle hybrid nanocomposites (GN/SnO2) was realized by using graphene oxide nanosheets (GONs) functionalized with sodium dodecyl sulfonate and SnCl2 as the starting materials. The morphology and structure of the synthesized SDS-GN/SnO2 nanocomposites were characterized by Raman spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction analysis. It was found that SnO2 nanoparticles were homogeneously distributed on the graphene nanosheets. The electrochemical behavior of dopamine (DA) at the SDS-GN/SnO2 nanoparticle modified electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed that the modified electrode exhibited excellent electrocatalytic activity towards the electrochemical oxidation of DA. The separation of the oxidation peak potentials for ascorbic acid (AA)-DA, uric acid (UA)-DA and UA-AA obtained by DPV is about 132 mV, 128 mV and 260 mV, respectively, which allows selective and sensitive detection of DA in the presence of AA and UA. The anodic peak currents were linear with the concentration of DA in the range from 1.0 × 10-7 to 1.0 × 10-5 M with a coefficient of 0.9980. The detection limit was 80 nM (S/N = 3). The proposed method could be applied for the determination of DA in real human urine samples.

Direct electrodeposition of gold nanotube arrays of rough and porous wall by cyclic voltammetry and its applications of simultaneous determination of ascorbic acid and uric acid

Gold nanotube arrays of rough and porous wall has been synthesized by direct electrodeposition with cyclic voltammetry utilizing anodic aluminum oxide template (AAO) and polycarbonate membrane (PC) during short time (only 3min and 2min, respectively). The mechanism of the direct electrodeposition of gold nanotube arrays by cyclic voltammetry (CV) has been discussed. The morphological characterizations of the gold nanotube arrays have been investigated by scanning electron microscopy (SEM). A simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry (DPV) was constructed by attaching gold nanotube arrays (using AAO) onto the surface of a glassy carbon electrode (GCE). The electrochemical behavior of AA and UA at this modified electrode has been studied by CV and differential pulse voltammetry (DPV). The sensor offers an excellent response for AA and UA and the linear response range for AA and UA were 1.02×10−7–5.23×10−4molL−1 and 1.43×10−7–4.64×10−4molL−1, the detection limits were 1.12×10−8molL−1 and 2.24×10−8molL−1, respectively. This sensor shows good regeneration, stability and selectivity and has been used for the determination of AA and UA in real human urine and serum samples with satisfied results.