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Quetiapine fumarate is an atypical antipsychotic drug, which is clinically used for the treatment of depression and bipolar disorders. A stability indicating method is required for the quality control of pharmaceutical dosage forms. This work focused on the developments of a rapid stability indicating reversed-phase HPLC-UV method for determination of quetiapine fumarate in tablets and extemporaneous formulations. Quetiapine fumarate was simultaneously determined in the presence of three impurities: quetiapine related compound B, quetiapine related compound G, and quetiapine N-oxide within 9 min. Optimal HPLC conditions were realized using Zorbax C8 column (100 mm × 4.6 cm i.d., 3 μm particle). Gradient elution utilized mobile composition of 0.15% triethylamine (pH 6.0) and acetonitrile : methanol (80:20) mixture at a flow rate of 1.2 mL/min with detection wavelength at 252 nm. The proposed method showed good linearity (r2 > 0.998), precision (RSDs ≤ 2.2), and accuracy (%recovery 96.8 – 99.4, RSD ≤ 1.9) with acceptable limits of detection (LOD ≤ 3.0 μg/mL) and quantitation (LOQ ≤ 10 μg/mL) at RSD ≤ 2.8). The method was successfully applied to the determination of quetiapine fumarate in pharmaceutical formulations and stability testing of extemporaneous formulations.

This work presents an affordable distance-based microfluidic paper-based device (μPAD), using polydiacetylene (PDA) liposome as a chromogenic substance with a smartphone-based photo editor, for rapid and in-field analysis of quaternary ammonium compounds (QACs) (e.g., didecyldimethylammonium chloride (DDAC), benzyldimethyltetradecyl ammonium chloride (BAC), and cetylpyridinium chloride (CPC)). In-field analysis of these compounds is important to ensure their antimicrobial activity and user safety since they are widely utilized as disinfectants in households and hospitals. The μPAD featured a thermometer-like shape consisting of a sample reservoir and a microchannel as the detection zone, which was pre-deposited with PDA liposome. The color change from blue to red appeared in the presence of QACs and the color bar lengths were proportional to the QAC concentrations. Reactions of QACs with the PDA required a specific pH range (from pH 4.0 to 10.0) and a readout time of 7 min. Analytical performance characteristics of the device were tested with DDAC, BAC, and CPC showing acceptable specificity, accuracy (96.1-109.4%), and precision (%RSDs ≤ 9.3%). Limits of detection and quantitation were in the ranges of 20 to 80 and 70 to 250 μM, respectively. Feasibility of the newly developed device was demonstrated for in-field analysis of QACs in fumigation solution providing comparable results with those obtained from a colorimetric assay (P 0.05). The proposed device shows potentials for further applications of other analytes since it offers speed, simplicity, and affordability for in-field analysis, especially in remote areas where expertise, resources, and infrastructures are limited. Graphical abstract.

Charantin is a mixture of β-sitosterol and stigmastadienol glucosides, which effectively lowers high blood glucose. Novel molecularly imprinted polymers coated magnetic nanoparticles (Fe3O4@MIPs) and filter paper (paper@MIPs) were synthesized by sol-gel polymerization to selectively extract charantin. β-sitosterol glucoside was selected as a template for imprinting a specific recognition owing to its larger molecular surface area than that of 5,25-stigmastadienol glucoside. Factorial designs were used to examine the effects of the types of porogenic solvents and cross-linkers on the extraction efficiency and imprinting factor before investigating other factors (for example, amounts of template and coated MIPs, and types of substrates for MIP immobilization). Compared to traditional liquid–liquid extraction, the optimal Fe3O4@MIP-based dispersive micro-solid phase extraction and paper@MIP extraction provided excellent extraction efficiency (87.5 ± 2.1% and 85.0 ± 2.9%, respectively) and selectivity. Charantin was well separated, and a new unidentified sterol glucoside was observed using the developed high-performance liquid chromatography with diode-array detection (Rs ≥ 2.0, n > 16,400). The developed methods were successfully utilized to extract and quantify charantin from M. charantia fruit powder and herbal products. Moreover, these methods are rapid (

In this proof-of-concept study, we explore the detection of pesticides in food using a combined power of sensitive UV-induced fingerprint spectroscopy with selective capture by molecularly imprinted polymers (MIPs) and portable cost-effective paper-based analytical devices (PADs). The specific pesticides used herein as model compounds (both pure substances and their application products for spraying), were: strobilurins (i.e. trifloxystrobin), urea pesticides (rimsulfuron), pyrethroids (cypermethrine) and aryloxyphenoxyproponic acid herbicides (Haloxyfop-methyl). Commercially available spraying formulations containing the selected pesticides were positively identified by MIP-PADs swabs of sprayed apple and tomato. The key properties of MIP layer - imprinting factor (IF) and selectivity factor (α) were characterized using trifloxystrobin (IF-3.5, α-4.4) was demonstrated as a potential option for in-field application. The presented method may provide effective help with in-field testing of food and reveal problems such as false product labelling.

Cytochrome P450 (CYP450), and in particular CYP3A4, is the most abundantly expressed CYP450 isozyme implicated in many drug-drug and medicinal plant-drug interactions. Therefore, incorporation of CYP3A4 enzyme screening at an early stage of drug discovery is preferable in order to avoid enzymatic interactions. Here we present for the first time a paper-based CYP3A4 immobilized sol-gel-derived a platform using resorufin benzyl ether as a fluorogenic enzyme substrate used to investigate enzyme activity. The fluorescence intensity of the product can be simply quantified by using a handheld digital microscope and an image analysis software. The limit of quantitation was 0.35 μM with good precision (RSDs 0.05), while offering simplicity and lower cost. Kinetic parameters of the immobilized CYP3A4 in sol-gel coated paper were calculated from the Lineweaver-Burk plot, including Michaelis constant (Km) and maximum velocity (Vmax), which were 2.71 ± 0.35 μM and 0.43 ± 0.05 μM/min, respectively. Moreover, a functional test of these devices was conducted by assessments of known CYP3A4 inhibitors (i.e. ketoconazole, itraconazole) and inducers (i.e. phenytoin, carbamazepine). To further demonstrate the broad range of uses, the devices were utilized to assay plant extracts i.e. Areca catechu seeds, Camellia sinensis leaves, Eclipta prostrata aerial part, providing results in good agreement with previous studies. Furthermore, the sol-gel immobilized enzyme stored at 4 °C can increase storage stability, offering the activity of 86.3 ± 0.4% after 3-weeks storage, equivalent to the activity of the free enzyme solution after 1-week storage. The developed paper-based devices offer versatility, portability and low-cost.

Adamantane drugs (e.g., memantine, rimantadine, and amantadine) consist of a core tricyclodecane with different substituents. Memantine is used for treatment of Alzheimer’s disease, while rimantadine and amantadine are recommended for influenza A infection. Additionally, amantadine is clinically used for Parkinson’s disease. Analysis of adamantine drugs by optical detection requires some derivatization due to the lack of chromophores or fluorophores in their structures. This procedure is performed to enhance their detectability, but it can be time- and labor-intensive. This work focuses on developments of a simple and fast technique for the analysis of these drugs in a microplate platform. Derivatization was achieved in 50 mM borate buffer (pH 11.0) using a stoichiometric ratio between the analyte and fluorescamine (as a derivatizing reagent) of 1:10 and a reaction time of 10 min. The fluorescent derivatives were determined in a 96-well microplate using excitation and emission wavelengths at 385 and 485 nm, respectively. The method showed good linearity (r2 > 0.968), repeatability (RSDs of

In-capillary derivatization using fluorescamine as the labeling reagent was proposed to enhance the detectability of adamantine drugs (memantine, amantadine and rimantadine) by spectrophotometric detection. Fluorescamine and the drugs were delivered to the capillary electrophoresis instrument at a ratio of 10:1 by zone injection. The derivatization reaction occurred following the application of voltage (20 kV). The derivatized products, hydrolyzed- fluorescamine and excess fluorescamine were separated in 7 min using 100 mM borate buffer (pH 10.0) containing 0.1% w/v of Brij®-35 and 20% v/v of acetonitrile. Validation data showed good linearity (r2 > 0.98), precision (%RSDs

Quantum dots (QDs) have been widely applied in the analytical field including sensitive fluorescent assays on paper-based devices. A facile in-situ synthesis of QDs after a simple reagent deposition on paper could enable a rapid low-cost fabrication of QD–modified paper with a variety of properties and purposes such as enzymatic nanoreactors. Herein, for the first time, fluorescent ZnCd QDs were prepared by in-situ synthesis in the paper matrix using thiol-containing precursors and irradiation by UV light. A successful creation of the immobilized ZnCd QDs on paper (paper@ZnCd QDs) was monitored by their intrinsic fluorescence while their peroxidase mimetic activity was evaluated by a catalytic reaction between H2O2 and a substrate (3,3′,5,5′-tetramethylbenzidine, TMB) producing a blue coloured product of charged transfer complex of TMB (oxTMB). From three thiol precursors investigated, the insulin precursor provided a greater activity than glutathione (GSH) and both considerably larger than BSA. Finally, a QDs precursor mixture deposition onto the paper matrix was evaluated by the peroxidase-mimetic activity, which was comparable with a reference method. The in-situ preparation of paper@ZnCd QDs is simple, rapid and ‘green’, with potential in biomedical applications primarily as fluorescence imaging agent and enzyme mimetic paper-based nanoreactors.

Optical detection systems for portable analytical instrument require commercially available, miniaturized, robust and well performing light sources. Light emitting diodes (LEDs) have been extensively used in portable analytical devices as they are exceptionally stable light sources offering a number of advantages over traditional light sources including robustness, small size and low-cost. In the analytically more significant deep UV spectral range, LEDs suffer from low optical power and parasitic emissions in the visible wavelength range. Recently, newly developed deep UV-LEDs based on aluminium nitride (AlN) substrates have been introduced claiming improved performance, however there is little in terms of systematic evaluation of their performance parameters when used as light sources in chemical sciences. The aim of this work was to investigate the performance of these new generation deep UV‐LEDs, and assess their analytical applicability. Three AlN substrate based LEDs (OPTAN255H, OPTAN255J and OPTAN280J) were selected based on their maximum emission wavelength and maximum optical power. Their emission spectra, optical output power values and energy conversion efficiency (electrical/optical) were investigated. This work shows effects of forward current and voltages on the ratio of intensities of the visible parasitic emission to the desirable deep UV emission. Experimental results show that while the parasitic emission still exists with the new generation deep UV-LEDs, with increasing forward current the ratio of undesirable parasitic emission to the main deep UV emission rapidly decreased to values as low as 0.1% at the maximum forward current (100 mA). The new generation deep UV-LED (255 nm) was then applied as a light source for a photometric on-capillary detection, showing excellent linearity with stray light down to 0.8%, and effective pathlength above 92% of the used capillary inner diameter, and finally the performance was demonstrated by detection of four parabens separated by miniaturised capillary liquid chromatography.

In this study, a method based on chemometrics and Raman spectroscopy was developed to classify vegetable oils and quantify alpha-tocopherol, the most common vitamin E source in vegetable oils. The Raman spectra of 108 oil samples, obtained from 18 commercial brands and six oil types, were recorded in the scattering mode. The results of classification models, partial least squares–discriminant analysis (PLS-DA), and soft independent modeling of class analogies (SIMCA) showed that all samples were accurately assigned the oil brands and vegetable types. Furthermore, the partial least squares regression (PLSR) model for the determination of the alpha-tocopherol content was established from the Raman spectra of 72 calibration samples modeled with reference values achieved from high-performance liquid chromatography (HPLC). Data from both methods were highly correlated (R2 > 0.95). For the optimum PLSR model, orthogonal signal correction was employed in the data (800–2000 cm−1). Thus, a highly efficient model with 2 latent factors and a good root mean square error of prediction (16.05), was obtained.

Carbamazepine is an antiepileptic drug with a narrow therapeutic index, which requires an efficient method for blood level monitoring. Finger-prick dried blood spot (DBS) collection is an alternative microsampling technique, which is less invasive than conventional venipuncture. Paper-based molecularly imprinted-interpenetrating polymer networks (MI-IPN) were developed as blood collection devices, which allowed for selective on-spot microextraction of carbamazepine from DBS. A hybrid of homogeneous polystyrene and silica gel polymer was synthesized and coated on a Whatman® Grade 1 filter paper. Proteins and other interferences in the blood samples were eliminated by using the MI-IPN collection devices, and the resulting DBS extracts were suitable for direct injection into the capillary electrophoretic instrument. The lower limit of quantitation of 4 μg/mL in capillary blood was achieved by the sweeping-micellar electrokinetic chromatography method using a KCl-containing matrix, which was sufficient for the therapeutic drug monitoring purposes. Method accuracies were in the range of 88.4 ± 4.5% to 94.5 ± 2.7% with RSD values ≤ 5.1%. The developed paper-based MI-IPN provided superior extraction efficiencies (92.2 ± 2.5%) in comparison with commercially available DBS collection cards, i.e., Whatman® 903 protein saver card (59.8 ± 2.8%) and GenCollect™ 2.0 card (47.2 ± 1.4%). The paper-based MI-IPN devices for DBS collection and on-spot extraction were characterized by simple fabrication, low costs, disposability, and reduction in sample preparation steps, and their further developments might open new perspectives in clinical applications, such as in therapeutic drug monitoring.

Exosome quantification is important for estimation of informative messengers (e.g., proteins, lipids, RNA, etc.) involving physiological and pathological effects. This work aimed to develop a simple and rapid distance-based paper portable device using exosome-capture vesicles (polydiacetylene conjugated with antiCD81) for exosome quantification in cell cultures. This novel concept relied on distinct aggregation of exosomes and exosome-capture vesicles leading to different solvent migration. Distances of the migration were used as signal readouts, which could be detected by naked eye. PDA-antiCD81 as exosome-capture vesicles were optimized (e.g., size, reaction ratio, and concentration) and the paper designs were investigated (e.g., diameter of sample reservoir and lamination layer) to enhance the solvent stop-flow effects. Finally, exosome screening on three cell culture samples (COLO1, MDA-MB-231, and HuR-KO1 subclone) was demonstrated. The method could linearly measure exosome concentrations in correlation with solvent migration distances in the range of 106 -1010 particles/mL (R2 > 0.98) from the cell culture samples. The exosome concentration measurements by the developed device were independently assessed by nanoparticle tracking analysis. Results demonstrated no statistically significant difference (p > 0.05) by t-test. This low-cost and rapid device allows a portable platform for exosome quantification without the requirement of expensive equipment and expertise of operation. The developed device could potentially be useful for quantification of other biomarker-related extracellular vesicles.

Brompheniramine, an antihistamine drug, was employed as a novel UV probe for capillary electrophoresis with indirect UV detection of adamantane drugs (memantine, amantadine, and rimantadine). The probe possesses high molar absorptivity of 24 × 103 L/mol cm at 6 mM, which enables the measurement of these nonchromophore analytes without derivatization. The simple background electrolyte (10 mM sodium dihydrogen phosphate (pH 5.0) containing 5 mM brompheniramine and 6 mM β-cyclodextrin) provided the separation of the analytes in a short time (7.5 min). Under these conditions, brompheniramine had similar mobility to that of the analyte ions resulting in symmetric peaks with minimal electrodispersion. The analytes displace the probe at a one-to-one ratio with transfer values close to unity. β-Cyclodextrin played a role in the resolution of the structurally similar adamantane derivatives. Method validation showed good linearity (r2 > 0.98), precision (%RSD ≤ 3.30), and accuracy (recoveries ranging from 98 to 109%). The proposed method was successfully applied to determine the adamantane content in pharmaceutical products.

Introduction Clerodendrum plants have been traditionally used for inflammatory related diseases in Thailand. Crude extracts of Clerodendrum disparifolium and Clerodendrum laevifolium were assessed for antioxidant and anti-inflammatory activities in order to support traditional Thai claims about the therapeutic potential of these plants. Methods Ethanol and hexane extracts of leaves were evaluated for the in vitro antioxidant activity including phenolic content assay using Folin–Ciocalteu method, flavonoid content assay using an aluminium chloride (AlCl 3 ) colorimetric method, 2, 2-Diphenyl-2-picryl-hydrazyl (DPPH) free-radical scavenging activity assay, total reductive capability assay, total antioxidant activity assay using ferric thiocyanate (FTC) and thiobarbituric (TBA) methods. In addition anti-inflammatory activity was assayed against lipoxygenase. Results The phenolic and flavonoid contents, relating with their antioxidant activities, of the extracts ranged from 1167.21–3344.52 GAE/g of dry extract and 9.05–59.91 mg QE/g of dry extract, respectively. Reducing power increased with increasing concentrations of extracts. The lipid peroxidation inhibition was evaluated by ferric thiocyanate (FTC) and thiobarbituric (TBA) methods, which demonstrated the maximum inhibition in ethanol C. laevifolium (55.49%) and C. disparifolium (96.17%) extracts, respectively. Furthermore the ethanol C. laevifolium extract exhibited highest 2, 2-Diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging activity (IC 50 12.70 μg/mL) and also possessed the greatest anti-inflammatory activity (IC 50 14.12 μg/mL). Conclusions This study indicated that selected Clerodendrum leaf extracts exhibited potential antioxidant and anti-inflammatory activities, which could be focus of further phytochemical research and may be applicable as natural medicine.

Many separation methods have been developed for biomedical analysis, including chromatographic (e.g. high performance liquid chromatography (HPLC) and gas chromatography (GC)) and electrophoretic methods (e.g. gel electrophoresis and capillary electrophoresis (CE)). Among these techniques, CE provides advantages in terms of high separation efficiency, simplicity, low sample and solvent volume consumption, short analysis time and applicability to a wide range of biomedically important substances. Microchip electrophoresis (ME) is a miniaturized platform of CE and is now considered as a simpler and more convenient alternative, which has demonstrated potential in analytical chemistry. High-throughput, cost-effective and portable analysis systems can be developed using ME. The current review describes different separation modes and detectors that have been employed in ME to analyze various classes of biomedical analytes (e.g. pharmaceuticals and related substances, nucleic acids, amino acids, peptides, proteins, antibodies and antigens, carbohydrates, cells, cell components and lysates). Recent applications (during 2010-2014) in these areas are presented in tables and some significant findings are highlighted.

A simple, rapid and cost effective UV-VIS spectrophotometric method was validated and applied for stability assessment of 5% ceftazidime in extemporaneous ophthalmic solution in various conditions. Ceftazidime dissolving in sterile water showed the maximum absorbance (λmax) at 256 nm and no interference was observed. The method validation was determined in term of linearity, intra-day and inter-day precision, accuracy, limit of detection (LOD) and limit of quantitation (LOQ) according to ICH guideline. Spectrophotometric response was linear with r2 = 0.9998 in the range of 5-25 μg/mL. The mean recovery was 99.38% with percent relative standard deviations (%RSDs) of 0.83. Intra-day and inter-day precision showed %RSDs of < 1.00%. LOD and LOQ were 2.60 and 7.88 μg/mL, respectively. The method was reliable for stability study of extemporaneous ceftazidime ophthalmic solution. Results showed that the amount of ceftazidime in extemporaneous formulation stored in both ambient and accelerated conditions dramatically decreased within 1 day. However, the preparation was stable at 2-8 °C for 7 days. In conclusion, the storage temperature had greatly impact on ceftazidime ophthalmic solution therefore it should be kept in the refrigerator for a week and its stability could be monitored using the simple spectrophotometric method.

Clerodendrum disparifolium is a Thai herbal medicine, which is used for the treatment of insect bites and sting reactions by applying finely crushed leaves to the inflamed area. However, this usage is inconvenient. The study aimed to develop gel-and cream-based formulations containing 0.5 %w/v of C. disparifolium extract, and evaluate their physicochemical properties. Different topical formulations were prepared using Carbopol 934 for gels and stearic acid for creams by varying their concentrations. The results showed that gel-based formulation containing Carbopol 934 in the range of 0.5-1.0 %w/w had good appearance, appropriate spreadability (7.30-8.70 cm) and viscosity (33,100-68,920 centipoise (cps)). The pH of gel-based formulation ranged from 6.01 to 6.11. For cream-based formulation containing 10-12 % w/w of stearic acid exhibited good physicochemical characteristics. The spreadability, viscosity and pH were 5.00-5.50 cm, 110,050-174,900 cps and 6.03-6.08, respectively. The results provided the suitable formulations, which should be continuously developed for large-scale pharmaceutical production.

Brompheniramine, an antihistamine drug, was employed as a novel UV probe for capillary electrophoresis with indirect UV detection of adamantane drugs (memantine, amantadine, and rimantadine). The probe possesses high molar absorptivity of 24 × 10

Rapid detection of microorganisms by alternative methods is desirable. Electromigration separation methods have the capability to separate microorganisms according to their charge and size and laser-induced fluorescence (LIF) detection have single-cell detection capability. In this work, a new combined separation and detection scheme was introduced using chip-based capillary electrophoresis (chip-CE) platform with LIF detection. Three microorganisms Escherichia coli , Staphylococcus aureus, and Candida albicans were selected as representatives of Gram-positive bacteria, Gram-negative bacteria, and fungi. While their cells carry an overall negative charge in neutral to alkaline pH, staining them with nile blue (NB) provided highly sensitive LIF detection with excitation and emission wavelengths at 635 nm and 685 nm, respectively, and at the same time, the overall charge was converted to positive. Electrolyte pH and concentration of polyethylene oxide (PEO) significantly affected the resolution of the microorganisms. Their optimal separation in the 14 mm separation channel was achieved in less than 30 s (R s > 5.3) in an electrolyte consisting of 3.94 mM Tris, 0.56 mM boric acid, 0.013 mM ethylenediaminetetraacetic acid disodium salt dihydrate (pH 10.5), and 0.025% PEO, with injection/separation voltages of +1000/+1000 V. The separation mechanism is likely employing contributions to the overall cationic charge from both the prevalently anionic membrane proteins and the cationic NB. Importantly, the resulting cationic NB-stained cells exhibited excellent separation selectivity and efficiency of ~38000 theoretical plates for rapid separations within 30-40 s. The results indicate the potential of chip-CE for microbial analysis, which offers separations of a wide range of species with high efficiency, sensitivity, and throughput.

A capillary zone electrophoretic method using UV detection is developed for the analysis of four biological active pyridines [i.e., nicotine (NIC), cotinine (COT), nicotinic acid (NA), and nicotinamide (NM)]. The separation of the pyridines is achieved in 25 mM sodium dihydrogen phosphate ( pH 2.1) using a fused-silica capillary with an effective length of 56 cm and an inner diameter of 50 mm (extended light path), hydrodynamic injection at 50 mbar for 10 s, a temperature of 258C, applied voltage of 30 kV, and UV detection at 260 nm. These conditions provide baseline separation of all the analytes [resolution (Rs) > 3.6] in 9.4 min with good linearity (r 2 > 0.998, in ranges of 50–600 mg/mL for NIC, 8 –160 mg/mL for NM, and 10–200 mg/mL for COT and NA), precision (relative standard deviation

Paper-based microfluidic devices (μPADs) are capable of achieving rapid quantitative measurements of a variety of analytes inexpensively. μPADs rely on patterning hydrophilic-hydrophobic regions on a sheet of paper in order to create capillary channels within impermeable fluidic brakes on the paper. Here, we present a novel, highly flexible and low-cost fabrication method using a desktop digital craft plotter/cutter and technical drawing pens with tip size of 0.5 mm. The pens were used with either commercial black permanent ink for drawing fluidic brakes, or with specialty in-house formulated aqueous inks. With the permanent marker ink it was possible to create barriers on paper rapidly and in a variety of designs in a highly flexible manner. For instance, a design featuring eight reservoirs can be produced within 10 s for each μPAD with a consistent line width of brakes (%RSD

Trends towards portable analytical instrumentation of the last decades have not been equally reflected in developments of portable liquid chromatography (LC) instrumentation for rapid on-site measurements. A miniaturised medium pressure capillary LC (MPLC) system with gradient elution capability has been designed based on a flexible modular microfluidic system using primarily off-the-shelf low cost components to ensure wide accessibility to other analysts. The microfluidic platform was assembled on a breadboard and contained microsyringe pumps and switch valves, complemented with an injection valve and on-capillary detectors, all controlled by a PC. Four miniaturised microsyringe pumps, with 5, 20 and 100 μL syringe volume options, formed the basis of the pumping system. Two pairs of pumps were used for each mobile phase to create gradient elution capability. The two microsyringe pumps in each pairs were linked by two electrically operated microfluidic switching valves and both pairs of pumps were connected through a zero void volume cross-connector, thus providing a low hold-up volume for gradient formation. Sample was injected by a 20 nL nano-LC sampling valve, directly connected to a 18 cm long 100 μm i.d. Chromolith CapRod RP-18 monolithic capillary column. On-capillary LED-based UV-vis photometric detection was conducted through a piece of equal diameter fused silica capillary connected after the column. The performance of the portable LC system was evaluated theoretically and experimentally, including the maximum operating pressure, gradient mixing performance, and the performance of the detectors. The 5 μL microsyringe pump offered the best performance, with typical maximum operating pressures up to 11.4 ± 0.4 MPa (water) and gradient pumping repeatability of between 4 and 9% for gradients between 0.10% s(-1) and 0.33% s(-1). Test analytes of charged and uncharged dyes and pharmaceuticals of varying hydrophobicity showed typical RSD values of 0.7-1.4% and 3.3-4.8% in isocratic mode and 1.2-4.6% and 3.2-6.4% in gradient mode, respectively for retention time and peak area repeatability.

Capillary electrophoresis (CE) coupled with capacitively-coupled contactless conductivity (C4D) and fluorescence (FD) detectors and chip-CE for monitoring of nicotine and cotinine derivatization was demonstrated. Separation of the substrates and intermediates could be achieved by CE-C4D in 7 min (Rs > 2.7) using 45 mM acetic acid (pH 3.0) and this system was applied to detect the intermediate formation. Final fluorescent products could be analyzed by micellar electrokinetic chromatography (MEKC-FD) in 5 mM borate buffer (pH 9.0) containing 10 mM sodium dodecylsulfate (SDS) (%RSD < 3.00%). Transferring of MEKC-FD to chip-CE allowed for shorter analysis time (2.5 min) and decreased sample consumption. The chip-CE-FD shows good detection and quantitation limits (< 7.5 μM) and precision (%RSD < 2.81%) and was employed to determine nicotine and cotinine in artificial urine. This work reveals the potential of CE and chip-CE with dual detectors as simultaneous, convenient and rapid methods for monitoring pyridine derivatization. © The Japan Society for Analytical Chemistry.

Microfluidic chip electrophoresis (chip-CE) is a separation method that is compatible with portable and on-site analysis, however, only few commercial chip-CE systems with laser-induced fluorescence (LIF) and light emitting diode (LED) fluorescence detection are available. They are established for several application tailored methods limited to specific biopolymers (DNA, RNA and proteins), and correspondingly the range of their applications has been limited. In this work we address the lack of commercially available research-type flexible chip-CE platforms by exploring the limits of using an application-tailored system equipped with chips and methods designed for DNA separations as a generic chip-CE platform – this is a very significant issue that has not been widely studied. In the investigated Agilent Bioanalyzer chip-CE system, the fixed components are the Agilent chips and the detection (LIF at 635 nm and LEDIF at 470 nm), while the chemistry (electrolyte) and the programming of all the high voltages are flexible. Using standard DNA chips, we show that a generic CE function of the system is easily possible and we demonstrate an extension of the applicability to non-aqueous CE (NACE). We studied the chip compatibility with organic solvents ( i.e. MeOH, ACN, DMF and DMSO) and demonstrated the chip compatibility with DMSO as a non-volatile and non-hazardous solvent with satisfactory stability of migration times over 50 h. The generic CE capability is illustrated with separations of fluorescent basic blue dyes methylene blue (MB), toluidine blue (TB), nile blue (NB) and brilliant cresyl blue (BC). Further, the effects of the composition of the background electrolyte (BGE) on the separation were studied, including the contents of water (0–30%) and buffer composition. In background electrolytes containing typically 80 mmol/L ammonium acetate and 870 mmol/L acetic acid in 100% DMSO baseline separation of the dyes were achieved in 40 s. Linearity was documented in the range of 5–28 μmol/L, 10–100 μmol/L, 1.56–50 nmol/L and 5–75 nmol/L ( r 2 values in the range 0.974–0.999), and limit of detection (LOD) values were 90 nmol/L, 1 μmol/L 1.4 nmol/L, and 2 nmol/L for MB, TB, NB and BC, respectively.

Rapid detection of microorganisms by alternative methods is desirable. Electromigration separation methods have the capability to separate microorganisms according to their charge and size and laser-induced fluorescence (LIF) detection have single-cell detection capability. In this work, a new combined separation and detection scheme was introduced using chip-based capillary electrophoresis (chip-CE) platform with LIF detection. Three microorganisms Escherichia coli, Staphylococcus aureus, and Candida albicans were selected as representatives of Gram-positive bacteria, Gram-negative bacteria, and fungi. While their cells carry an overall negative charge in neutral to alkaline pH, staining them with nile blue (NB) provided highly sensitive LIF detection with excitation and emission wavelengths at 635 nm and 685 nm, respectively, and at the same time, the overall charge was converted to positive. Electrolyte pH and concentration of polyethylene oxide (PEO) significantly affected the resolution of the microorganisms. Their optimal separation in the 14 mm separation channel was achieved in less than 30 s (R(s)5.3) in an electrolyte consisting of 3.94 mM Tris, 0.56 mM boric acid, 0.013 mM ethylenediaminetetraacetic acid disodium salt dihydrate (pH 10.5), and 0.025% PEO, with injection/separation voltages of +1000/+1000 V. The separation mechanism is likely employing contributions to the overall cationic charge from both the prevalently anionic membrane proteins and the cationic NB. Importantly, the resulting cationic NB-stained cells exhibited excellent separation selectivity and efficiency of ∼38000 theoretical plates for rapid separations within 30-40 s. The results indicate the potential of chip-CE for microbial analysis, which offers separations of a wide range of species with high efficiency, sensitivity, and throughput.