On-line concentration and separation of proteins by capillary electrophoresis using polymer solutions

Ion-Exchange Chromatography Coupled With Dynamic Coating Capillary Electrophoresis for Simultaneous Determination of Tropomyosin and Arginine Kinase in Shellfish

Tropomyosin (TM) and arginine kinase (AK) are known as two major allergens in seafood. For the first time, we demonstrate a newly developed ion-exchange chromatography coupled with dynamic coating capillary electrophoresis (IEC-DCCE) method to simultaneously analyze the TM and AK in shellfish. First, we have optimized the procedure of IEC for simple enrichment of TM and AK crude extract. By using 30 mM borate-borax at pH 9.0 with 0.3% (v/v) Tween-20 as a dynamic coating modifier for capillary electrophoresis (CE) separation, the migration time, separation efficiency and electrophoretic resolution greatly improved. The limits of detection (LOD) were 1.2 μg mL-1 for AK and 1.1 μg mL-1 for TM (S/N = 3), and the limits of quantification (LOQ) were 4.0 μg mL-1 for AK and 3.7 μg mL-1 for TM (S/N = 10). The recovery of AK ranged from 91.5 to 106.1%, while that of TM ranged from 94.0 to 109.5%. We also found that only when the concentrations of AK and TM were above LOD reported here, these proteins can stimulate human mast cell (LAD2) degranulation. Finally, the use of IEC-DCCE to analyze fresh shellfish samples highlights the applicability of this method for the simultaneous detection of these allergens in complex food systems.

On-line sample preconcentration by sweeping and poly(ethylene oxide)-mediated stacking for simultaneous analysis of nine pairs of amino acid enantiomers in capillary electrophoresis

This study proposes a sensitive method for the simultaneous separation and concentration of 9 pairs of amino acid enantiomers by combining poly(ethylene oxide) (PEO)-based stacking, β-cyclodextrin (β-CD)-mediated micellar electrokinetic chromatography (MEKC), and 9-fluoroenylmethyl chloroformate (FMOC) derivatization. The 9 pairs of FMOC-derivatized amino acid enantiomers were baseline separated using a discontinuous system, and the buffer vials contained a solution of 150 mM Tris-borate (TB), 12.5% (v/v) isopropanol (IPA), 0.5% (w/v) PEO, 35 mM sodium taurodeoxycholate (STDC), and 35 mM β-CD, and the capillary was filled with a solution of 1.5 M TB, 12.5% (v/v) IPA, 35 mM STDC, and 35 mM β-CD. Based on the difference in viscosity between the sample zone and PEO solution and because of the STDC sweeping, the discontinuous system effectively stacked 670 nL of the 9 pairs of FMOC-derivatized amino acid enantiomers without losing chiral resolution. Consequently, the limits of detection for the 9 pairs of FMOC-derivatized amino acid enantiomers were reduced to 40-60 nM. This method was successfully used to determine d-Tryptophan (Trp), l-Trp, d-Phenylalanine (Phe), l-Phe, d-Glutamic acid (Glu), and l-Glu in various types of beers.

Multiplexed microRNA detection by capillary electrophoresis with laser-induced fluorescence

In this study, we developed a novel assay that simultaneously detects multiple miRNAs (microRNAs) within a single capillary by combining a tandem adenosine-tailed DNA bridge-assisted splinted ligation with denaturing capillary gel electrophoresis with laser-induced fluorescence. This proposed method not only represents a significant improvement in resolution but also allows for the detection of multiple miRNAs within a single capillary based on the length differences of specified target bridge DNA. The assay's linear range covers three orders of magnitude (1.0 nM to 1.0 pM) with a limit of detection (S/N=3) as low as 190 fM (2.5 zmol). Five miRNAs of Epstein-Barr virus (EBV) were also detected in EBV-infected nasopharyngeal carcinoma cells, while they did not appear in non-virus infected cells. Moreover, the electropherogram indicated that the screening of isomiRs (isomer of miRNA) of BART2 by CE-LIF is feasible by our proposed method. The developed electrophoresis-based method for miRNA detection is fast, amplification-free, multiplexed and cost-effective, making it potentially applicable to large-scale screening of isomiRs.

Bioanalytical applications of capillary electrophoresis with laser-induced native fluorescence detection

In this article we describe recent developments and applications of capillary electrophoresis (CE) coupled with laser-induced native fluorescence (LINF) detection in the analysis of biological, pharmaceutical and environmental samples. Compared with traditional UV absorbance detection used in CE, the LINF technique can greatly improve the concentration sensitivity of CE without the need for derivatization; the only requirement being that the analyte must have native fluorescence. Instrumentation and laser sources used in CE–LINF are summarized and specific applications of CE–LINF to small-biomolecule analysis, profiling of human biofluids, detection of native fluorescent peptides and proteins, single-cell analysis and the use of online sample preconcentration methods are also reviewed in detail.

Microfluidic single-cell analysis of intracellular compounds

Biological analyses traditionally probe cell ensembles in the range of 103-106 cells, thereby completely averaging over relevant individual cell responses, such as differences in cell proliferation, responses to external stimuli or disease onset. In past years, this fact has been realized and increasing interest has evolved for single-cell analytical methods, which could give exciting new insights into genomics, proteomics, transcriptomics and systems biology. Microfluidic or lab-on-a-chip devices are the method of choice for single-cell analytical tools as they allow the integration of a variety of necessary process steps involved in single-cell analysis, such as selection, navigation, positioning or lysis of single cells as well as separation and detection of cellular analytes. Along with this advantageous integration, microfluidic devices confine single cells in compartments near their intrinsic volume, thus minimizing dilution effects and increasing detection sensitivity. This review overviews the developments and achievements of microfluidic single-cell analysis of intracellular compounds in the past few years, from proof-of-principle devices to applications demonstrating a high biological relevance.

Single cell analysis in full body quartz glass chips with native UV laser-induced fluorescence detection

In order to investigate the individual and inhomogenous cellular response, e.g. to external stimuli, single cell analysis is mandatory and may provide new cognitions in proteomics as well as in other fields of systems biology in the future. Here, we report on novel chip architectures for single cell analysis based on full body quartz glass microfluidic chips (QG chips) that extend our previous studies in polydimethylsiloxane (PDMS) chips, and enhance the detection sensitivity of native UV laser-induced fluorescence (UV-LIF) detection. Detection of a 10nM tryptophan solution with an S/N ratio of 11.9, which gives a theoretical limit of detection of 2.5 nM (with S/N=3), was possible. With these optimizations the three proteins alpha-chymotrypsinogen A, ovalbumin and catalase each at a concentration of 100 microg/mL (equal to 4 microM, 0.4 microM and 2.2 microM) were injected electrokinetically and could be separated with nearly baseline resolution. Furthermore, fluorescence spectra (excitation wavelength, lambda(ex) = 266 nm) clearly demonstrate the favourable properties like the very high UV transparency and the nearly vanishing background fluorescence of the QG chips as compared to PDMS chips and to PDMS quartz window (PQW) chips. Finally we exploit the improved sensitivity for single cell electropherograms of Spodoptera frugiperda (Sf9) insect cells.

Electrophoretic determination of albumin in urine using on-line concentration techniques

To improve the sensitivity of the UV-detection for the determination of trace amounts of albumin by capillary zone electrophoresis (CZE), five on-line preconcentration techniques, including field-amplified sample stacking (FASS), head-column field-amplified sample stacking (HC-FASS), stacking with a polymer solution, dynamic pH junction and large volume sample stacking (LVSS) with reversed polarity, were compared. Sensitivity enhancement factor and reproducibility were two factors that were used to assess the suitability of each method. To minimize protein adsorption on the capillary wall, capillaries were covalently modified with anionic polymer, poly(sulfopropylmethacrylate) coating. All used methods have good reproducibility. The maximum sensitivity enhancement factor (about 67-fold in terms of peak heights) was achieved with LVSS technique. The concentration limit of detection (LOD) (S/N=3) for the human serum albumin obtained with the optimized LVSS approach was 15 microg/ml with UV-detection. The method was further evaluated for the analysis of urine samples with gel-filtration-based sample-desalting procedure.

Stacking and separation of fluorescent derivatives of amino acids by micellar electrokinetic chromatography in the presence of poly(ethylene oxide)

A new approach for the analysis of large-volume naphthalene-2,3-dicarboxaldehyde (NDA) derivatives of amino acids by micellar electrokinetic chromatography (MEKC) in conjunction with a purple light-emitting diode-induced fluorescence detection is described. In order to optimize resolution, speed, and stacking efficiency, a discontinuous condition is essential for the analysis of NDA-amino acid derivatives. The optimum conditions use 2.0M TB (pH 10.0) buffer containing 40mM sodium dodecyl sulfate (SDS) to fill the capillary, deionized water to dilute samples, and 200mM TB (pH 9.0) containing 10mM SDS to prepare 0.6% poly(ethylene oxide) (PEO). Once high voltage is applied, PEO solution enters the capillary via electroosmotic flow and SDS micelles interact and thus sweep the NDA-amino acid derivatives having smaller electrophoretic mobilities than that of SDS micelles in the sample zone. When the aggregates between SDS micelles and NDA amino acid derivatives enter PEO zone, they are stacked due to decrease in electric field and increases in viscosity. Under the optimum conditions, the concentration and separation of 0.53-microL 13 NDA-amino acid derivatives that are negatively charged has been demonstrated by using a 60-cm capillary, with the efficiencies 0.3-9.0x10(5) theoretical plates and the LODs at signal-to-noise ratio 3 ranging from 0.30 to 2.76nM. When compared to standard injection (30-cm height for 10s), the approach allows the sensitivity enhancements over the range of 50-800 folds for the derivatives. The new approach has been applied to the analysis of a red wine sample, with great linearity of fluorescent intensity against concentrations (R(2)>0.98) and the RSD (three repetitive runs in one day) values of the migration times for the ten identified amino acids less than 2.8%.

Capillary electrophoresis-based separation techniques for the analysis of proteins

CE offers the advantages of high speed, great efficiency, as well as the requirement of minimum amounts of sample and buffer for the analysis of proteins. In this review, we summarize the CE-based techniques coupled with absorption, LIF, and MS detection systems for the analysis of proteins mostly within the past 5 years. The basic principle of each technique and its advantages and disadvantages for protein analysis are discussed in brief. Advanced CE techniques, including on-column concentration techniques and high-efficiency multidimensional separation techniques, for high-throughput protein profiling of complex biological samples and/or of single cells are emphasized. Although the developed techniques provide improved peak capacity, they have not become practical tools for proteomics, mainly because of poor reproducibility, low-sample lading capacity, and low throughput due to ineffective interfaces between two separation dimensions and that between separation and MS systems. In order to identify the complexities and dynamics of the proteomes expressed by cells, tissues, or organisms, techniques providing improved analytical sensitivity, throughput, and dynamic ranges are still demanded.

Online concentration and separation of basic proteins using a cationic polyelectrolyte in the presence of reversed electroosmotic flow

We report an online concentration and separation method for basic proteins using poly(diallyldimethylammonium chloride) (PDDA) solutions in the presence of reversed EOF. Using a capillary dynamically coated with 2% PDDA containing 0.1 M NaCl and filled with 1.2% PDDA under neutral conditions (10 mM phosphate, pH 7.0), we have demonstrated the separation of six basic proteins with peak efficiencies ranging from 175 000 to 616 000 plates/m and RSDs of migration time less than 0.4%. Additionally, high-speed separation of six basic proteins (<7 min) was achieved using a short capillary filled with 0.6% PDDA solutions. Under injection of the large-volume sample (210 nL), the LODs at S/N of 3 for basic proteins are down to nanomolar range. For example, the LOD for lysozyme is 1.2 nM, which is a 260-fold sensitivity enhancement compared with conventional injection method. The proposed method has been applied to the stacking of lysozyme in human saliva samples. Without any pretreatment, we also demonstrated the capability of this method to detect low amounts of peptide samples through the stacking of tryptic peptide of myoglobin. The experimental results indicate that our proposed method has great potential for use in clinical diagnosis and proteomics applications.

Sample enrichment techniques in capillary electrophoresis: Focus on peptides and proteins

Compared to chromatography-based techniques, the concentration limits of detection (CLOD) associated with capillary electrophoresis are worse, and these have largely precluded their use in many practical applications. To overcome this limitation, researchers from various disciplines have exerted tremendous efforts toward developing strategies for increasing the concentration sensitivities of capillary electrophoresis (CE) systems, via the so-called sample enrichment techniques. This review highlights selected developments and advances in this area as applied to the analyses of proteins and peptides in the last 5 years.

Improved native UV laser induced fluorescence detection for single cell analysis in poly(dimethylsiloxane) microfluidic devices

Single cell analytics is a key method in the framework of proteom research allowing analyses, which are not subjected to ensemble-averaging, cell-cycle or heterogeneous cell-population effects. Our previous studies on single cell analysis in poly(dimethylsiloxane) microfluidic devices with native label-free laser induced fluorescence detection [W. Hellmich, C. Pelargus, K. Leffhalm, A. Ros, D. Anselmetti, Electrophoresis 26 (2005) 3689] were extended in order to improve separation efficiency and detection sensitivity. Here, we particularly focus on the influence of poly(oxyethylene) based coatings on the separation performance. In addition, the influence on background fluorescence is studied by the variation of the incident laser power as well as the adaptation of the confocal volume to the microfluidic channel dimensions. Last but not least, the use of carbon black particles further enhanced the detection limit to 25 nM, thereby reaching the relevant concentration ranges necessary for the label-free detection of low abundant proteins in single cells. On the basis of these results, we demonstrate the first electropherogram from an individual Spodoptera frugiperda (Sf9) cell with native label-free UV-LIF detection in a microfluidic chip.

Stacking, derivatization, and separation by capillary electrophoresis of amino acids from cerebrospinal fluids

This paper describes the in-column derivatization, stacking, and separation of amino acids by CE in conjunction with light-emitting diode-induced fluorescence using naphthalene-2,3-dicarboxaldehyde (NDA). According to the relative electrophoretic mobilities and the migration direction in tetraborate solution (pH 9.3), the injection order is cyanide, then amino acids, then NDA. Once poly(ethylene oxide) (PEO) migrates through the capillary under EOF, the amino acid.NDA derivatives, amino acids, and CN- ions migrating against the EOF enter the PEO zone. As a result of increases in viscosity and possible interactions with PEO molecules, the reagents/analytes slow down such that they become stacked at the boundary. In comparison with the off-column approach to the analysis of amino acids, our proposed method provides a lower degree of interference from polymeric NDA compounds and other side products. As a result, the plot of the peak height as a function of gamma-aminobutyric acid (GABA) concentration is linear over the range from 10(-5) to 10(-8) M, with the LOD being 4 nM. We demonstrate the diagnostic potential of this approach for the determination of amino acids, including GABA and glutamine, in biological samples through the analysis of large volumes of cerebral spinal fluids without the need for sample pretreatment.

Determination of aristolochic acid in Chinese herbal medicine by capillary electrophoresis with laser-induced fluorescence detection

We have demonstrated the analysis of aristolochic acids (AAs) that are naturally occurring nephrotoxin and carcinogen by capillary electrophoresis in conjunction with laser-induced fluorescence detection (CE-LIF). Owing to lack of intrinsic fluorescence characteristics of oxidized AAs (OAAs), reduction of the analytes by iron powder in 10.0 mM HCl is required prior to CE analysis. The reduced AAs (RAAs) exhibit fluorescence at 477 nm when excited at 405 nm using a solid-state blue laser. By using 50.0 mM sodium tetraborate (pH 9.0) containing 10.0 mM SDS, the determination of AA-I and AA-II by CE-LIF has been achieved within 12 min. The CE-LIF provides the LODs of 8.2 and 5.4 nM for AA-I and AA-II, respectively. The simple CE-LIF method has been validated by the analysis of 61 Chinese herbal samples. Prior to CE analysis, OAAs were extracted by using 5.0 mL MeOH, and then the extracts were subjected to centrifugation at 3,000 rpm for 5 min. After reduction, extraction, and centrifugation, the supernatants were collected and subjected to CE analysis. Of the 61 samples, 14 samples contain AA-I and AA-II, as well as 10 samples contain either AAI or AAII. The relative standard deviation (RSD) values of the migration times for AA-I and AA-II are less than 2.5% and 2.1% for three consecutive measurements of each sample. The RSD values for the peak heights corresponding to AA-I and AA-II in most samples are about 8.0% and 10.0%, respectively. The result shows that the present CE-LIF approach is sensitive, simple, efficient, and accurate for the determination of AAs in real samples.

Design and evaluation of a coupled monolithic preconcentrator-capillary zone electrophoresis system for the extraction of immunoglobulin G from human serum

The analysis of proteins in biological fluids by capillary electrophoresis (CE) is of interest in clinical chemistry. However, due to low analyte concentrations and poor concentration limits of detection (CLOD), protein analysis by this technique is frequently challenging. Coupling preconcentration techniques with CE greatly improves the CLOD. An on-line preconcentration-CE method that can selectively pre-concentrate any protein for which an antibody is available would be very useful for the analysis of low abundance proteins and would establish CE as a major tool in biomarker discovery. To accomplish this, the development of an on-line protein G monolithic pre-concentrator-CE device is proposed. To generate active groups for protein immobilization, glycidyl methacrylate (GMA) was used to prepare polymer monoliths. A 1.5-2 cm monolith was cast inside a 75 microm I.D. fused silica capillary that had previously been coated with alternating layers of negatively (dextran) and positively (polybrene) charged polymers. Protein G was covalently bound to GMA. Monoliths from different formulations were prepared and evaluated for binding capacity to optimize the monolith formulation for protein preconcentration. The physical properties of the column considered best for preconcentration were determined by mercury intrusion porosimetry. The total pore area was 4.8m(2)/g, the average pore diameter was 3.3 microm and the porosity was 82%. The monolith had a low flow resistance and was macroscopically homogeneous. The effectiveness of the monolith to rapidly pre-concentrate proteins at flow rates as high as 10 microL/min was demonstrated using a 1.8 microM IgG solution. This system proved effective for on-line sample extraction, clean-up, preconcentration, and CE of IgG in human serum. IgG from diluted (500 and 65,000 times) human serum samples was successfully analyzed using this system. The approach can be applied to the on-line preconcentration and analysis of any protein for which an antibody is available.

Single cell manipulation, analytics, and label-free protein detection in microfluidic devices for systems nanobiology

Single cell analytics for proteomic analysis is considered a key method in the framework of systems nanobiology which allows a novel proteomics without being subjected to ensemble-averaging, cell-cycle, or cell-population effects. We are currently developing a single cell analytical method for protein fingerprinting combining a structured microfluidic device with latest optical laser technology for single cell manipulation (trapping and steering), free-solution electrophoretical protein separation, and (label-free) protein detection. In this paper we report on first results of this novel analytical device focusing on three main issues. First, single biological cells were trapped, injected, steered, and deposited by means of optical tweezers in a poly(dimethylsiloxane) microfluidic device and consecutively lysed with SDS at a predefined position. Second, separation and detection of fluorescent dyes, amino acids, and proteins were achieved with LIF detection in the visible (VIS) (488 nm) as well as in the deep UV (266 nm) spectral range for label-free, native protein detection. Minute concentrations of 100 fM injected fluorescein could be detected in the VIS and a first protein separation and label-free detection could be achieved in the UV spectral range. Third, first analytical experiments with single Sf9 insect cells (Spodoptera frugiperda) in a tailored microfluidic device exhibiting distinct electropherograms of a green fluorescent protein-construct proved the validity of the concept. Thus, the presented microfluidic concept allows novel and fascinating single cell experiments for systems nanobiology in the future.

Silica nanoparticles for separation of biologically active amines by capillary electrophoresis with laser-induced native fluorescence detection

This paper describes the analysis of biologically active amines by capillary electrophoresis (CE) in conjunction with laser-induced native fluorescence detection. In order to simultaneously analyze amines and acids as well as to achieve high sensitivity, 10 mM formic acid solutions (pH < 4.0) containing silica nanoparticles (SiNPs) were chosen as the background electrolytes. With increasing SiNP concentration, the migration times for seven analytes decrease as a result of increase in electroosmotic flow (EOF) and decrease in their electrophoretic mobilities against EOF. A small EOF generated at pH 3.0 reveals adsorption of SiNPs on the deactivated capillary wall. The decreases in electrophoretic mobilities with increasing SiNP concentration up to 0.3x indicate the interactions between the analytes and the SiNPs. Having a great sensitivity (the limits of detection at a signal-to-noise ratio (S/N) = 3 of 0.09 nM for tryptamine (TA)), high efficiency, and excellent reproducibility (less than 2.4% of the migration times), this developed method has been applied to the analysis of urinal samples with the concentrations of 0.50 +/- 0.02 microM, 0.49 +/- 0.04 microM, and 74 +/- 2 microM for TA, 5-hydroxytryptamine, and tryptophan, respectively. The successful examples demonstrated in this study open up a possibility of using functional nanoparticles for the separation of different analytes by CE.

Sample preparation for peptides and proteins in biological matrices prior to liquid chromatography and capillary zone electrophoresis

The determination of peptides and proteins in a biological matrix normally includes a sample-preparation step to obtain a sample that can be injected into a separation system in such a way that peptides and proteins of interest can be determined qualitatively and/or quantitatively. This can be a rather challenging, labourious and/or time-consuming process. The extract obtained after sample preparation is further separated using a compatible separation system. Liquid chromatography (LC) is the generally applied technique for this purpose, but capillary zone electrophoresis (CZE) is an alternative, providing fast, versatile and efficient separations. In this review, the recent developments in the combination of sample-preparation procedures with LC and CZE, for the determination of peptides and proteins, will be discussed. Emphasis will be on purification from and determination in complex biological matrices (plasma, cell lysates, etc.) of these compounds and little attention will be paid to the proteomics area. Additional focus will be put on sample-preparation conditions, which can be 'hard' or 'soft', and on selectivity issues. Selectivity issues will be addressed in combination with the used separation technique and a comparison between LC and CZE will be made.

Application of dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium in wall modification for capillary electrophoresis separation of proteins

A zwitterionic surfactant, dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium (C12H25N+(CH3)2CH2CHOHCH2SO3-), named dodecyl sulfobetaine (DSB), was used as a novel modifier to coat dynamically capillary walls for capillary electrophoresis separation of basic proteins. The DSB coating suppressed the electroosmotic flow (EOF) in the pH range of 3-12. At high DSB concentration, the EOF was suppressed by more than 8.8 times. The DSB coating also prevented successfully the adsorption of cationic proteins on the capillary wall. Anions, such as Cl-, Br-, I-, SO4(2-), CO3(2-), and ClO4-, could be used as running buffer modifiers to adjust the EOF for better separation of analytes. Using this dynamically coated capillary, a mixture of eight inorganic anions achieved complete separation within 4.2 min with the efficiencies from 24,000 to 1,310,000 plates/m. In the presence of ClO4- as EOF adjustor, the separation of a mixture containing four basic proteins (lysozyme, cytochrome c, alpha-chymotrypsinogen A, and myoglobin) yielded efficiencies of 204,000-896,000 plates/m and recoveries of 88%-98%. Migration time reproducibility of these proteins was less than 0.5% relative standard deviation (RSD) from run to run and less than 3.1% RSD from day to day, showing promising application of this novel modifier in protein separation.

Discontinuous electrolyte systems for improved detection of biologically active amines and acids by capillary electrophoresis with laser-induced native fluorescence detection

On-line concentration and separation of biologically active amines and acids by capillary electrophoresis (CE) in conjunction with laser-induced fluorescence using an Nd:YAG laser at 266 nm under discontinuous conditions is presented. The suitable conditions for simultaneous analysis of amines and acids were: samples were prepared in a solution (pH* 3.1) consisting of 10 mM citric acid, 89% acetonitrile (ACN), and water; a capillary was filled with 1.5 M Tris-borate (TB) buffer (pH 10.0); and the anodic vial contained PTG10 buffer (pH* 9.0) that consists of 50 mM propanoic acid, Tris, 10% glycerol, and water. After injecting a large-volume sample, amines and acids were separately stacked at the front (cathodic side) and back (anodic side) of the acidic sample zone, mainly because of changes in their electrophoretic mobilities as a result of changes in pH, viscosity, and electric field when high voltage was applied. When the sample was injected at 15 kV for 360 s, the concentration limits of detection (LODs) for 5-hydroxytryptamine (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) were 0.27 and 0.31 nM, respectively, which are about 400- and 800-fold sensitivity improvements when compared to those injected at 1 kV for 10 s. For the analysis of amines, samples were prepared in 100 mM citric acid (pH* 1.8) containing 89% ACN and both the capillary and anodic vial were filled with 400 mM PTG20 (propanoic acid, Tris, 20% glycerol, and water) at pH* 4.5. Using a large injection volume (15 kV for 360 s), we achieved concentration LODs of 17 pM and 0.3 nM for tryptamine and epinephrine, which are about 5200- and 14,000-fold sensitivity improvements, respectively, in comparison with those injected at 1 kV for 10 s. The features of simplicity (no sample pretreatment), rapidity (12 min), and sensitivity for identification of amines and acids of interest in urine samples show diagnostic potential of the two approaches developed in this study.