Residence Time Of Sample Research Articles

A Review of the Efficacy of Ultraviolet C Irradiation for Decontamination of Pathogenic and Spoilage Microorganisms in Fruit Juices.

Ultraviolet C (UV-C, 200-280 nm) light has germicidal properties that inactivate a wide range of pathogenic and spoilage microorganisms. UV-C has been extensively studied as an alternative to thermal decontamination of fruit juices. Recent studies suggest that the efficacy of UV-C irradiation in reducing microorganisms in fruit juices is greatly dependent on the characteristics of the target microorganisms, juice matrices, and parameters of the UV-C treatment procedure, such as equipment and processing. Based on evidence from recent studies, this review describes how the characteristics of target microorganisms (e.g., type of microorganism/strain, acid adaptation, physiological states, single/composite inoculum, spore, etc.) and fruit juice matrices (e.g., UV absorbance, UV transmittance, turbidity, soluble solid content, pH, color, etc.) affect the efficacy of UV-C. We also discuss the influences on UV-C treatment efficacy of parameters, including UV-C light source, reactor conditions (e.g., continuous/batch, size, thickness, volume, diameter, outer case, configuration/arrangement), pumping/flow system conditions (e.g., sample flow rate and pattern, sample residence time, number of cycles), homogenization conditions (e.g., continuous flow/recirculation, stirring, mixing), and cleaning capability of the reactor. The collective facts indicate the immense potential of UV-C irradiation in the fruit juice industry. Existing drawbacks need to be addressed in future studies before the technique is applicable at the industrial scale.

Chemical Derivatization in Flow Analysis.

Chemical derivatization for improving selectivity and/or sensitivity is a common practice in analytical chemistry. It is particularly attractive in flow analysis in view of its highly reproducible reagent addition(s) and controlled timing. Then, measurements without attaining the steady state, kinetic discrimination, exploitation of unstable reagents and/or products, as well as strategies compliant with Green Analytical Chemistry, have been efficiently exploited. Flow-based chemical derivatization has been accomplished by different approaches, most involving flow and manifold programming. Solid-phase reagents, novel strategies for sample insertion and reagent addition, as well as to increase sample residence time have been also exploited. However, the required alterations in flow rates and/or manifold geometry may lead to spurious signals (e.g., Schlieren effect) resulting in distorted peaks and a noisy/drifty baseline. These anomalies can be circumvented by a proper flow system design. In this review, these aspects are critically discussed mostly in relation to spectrophotometric and luminometric detection.

EVIDENCES OF WEATHERING OF IRON-NICKEL AND TROILITE IN THE GRUZ'KE Н4-TYPE CHONDRITE

Terrestrial weathering of the Gruz'ke chondrite was investigated by considering its initial chemical, structural, and mineralogical characteristics. The spread of corrosion and degree of alteration were related to the high content of Fe-Ni metal, the phase inhomogeneity and the different concentration of Ni in the metal, as well as, the shock metamorphism features, and the residence time of the meteorite sample in a soil environment. The formation of secondary oxide veins and oxide rims, consisting of iron hydroxide pseudomorphs was caused by the selective corrosion of kamacite α-(Fe,Ni), compared to taenite γ-(Fe,Ni) and troilite FeS. A spatial relationship between shock metamorphism features, namely areas of plastic deformation, shock heating and weathering of the meteorite matter, has been confirmed. A secondary Ni-enriched phase, which contains 71.34 to 72.94 wt.% Ni, probably corresponds to awaruite (Ni2Fe to Ni3Fe) or native nickel. This phase is described for the first time as corrosion product of Fe-Ni grains in the Gruz'ke chondrite. We assume that this phase was formed during the alteration of Fe-Ni metal. Fe was removed from the meteorite metal during the corrosion process, while sulfur was introduced. The formation of iron hydroxide pseudomorphs caused changes in primary chemical and structural properties of some crystals of nickel-iron metal and troilite. Thus, the use of weathered mineral grains to interpret the pre-terrestrial conditions of the chondrite matter formation and evolution is limited. In spite of the changes in chemical and mineral composition, the corrosion products of nickel iron and troilite have consistent low chlorine content.Therefore we assume that the akaganeite β-FeO(OH,Cl) secondary phase is unlikely to form. It will prevent further alteration of the Fe-Ni metal and ensure long-term storage and preservation of the meteorite sample for further laboratory research and storage in the museum collection.

Effects of dose loading conditions and device geometry on the transport and aerosolization in dry powder inhalers: A simulation study

The transport and aerosolization of particles are studied in several different dry powder inhaler geometries via Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations. These simulations combine Large Eddy Simulation of gas with Discrete Element Model simulation of all the carrier particles and a representative subset of the active pharmaceutical ingredient (API) particles. The purpose of the study is to probe the dominant mechanism leading to the release of the API particles and to demonstrate the value of the CFD-DEM simulations where one tracks the motion of all the carrier and API particles. Simulations are performed at different inhalation rates and initial dose loading conditions for the screen-haler geometry, a simple cylindrical tube inhaler, and five different geometry modifications that took the form of bumpy walls and baffles. These geometry modifications alter the residence time of the powder sample in the inhaler, pressure drop across the inhaler, the severity of gas-carrier interactions, and the number of collisions experienced by the carrier particles, all of which are quantified. The quality of aerosolization is found to correlate with the average air-carrier slip velocity, while collisions played only a secondary role. Some geometry modifications improved aerosolization quality with very little increase in the pressure drop across the device.

Microstructure and magnetism of Ga+-irradiated IrMn-based spin-valve multilayered film

An IrMn top-nailed spin-valve multilayer film was synthesized using direct-current magnetron sputtering on a naturally oxidized silicon substrate. The multilayered film microstructure and magnetism were analyzed using x-ray diffraction, transmission, and atomic force microscopies as well as vibrating sample magnetometry as functions of ion irradiation. The reverse saturation field residence time of the spin-valve multilayered sample was used to assess its magnetic stability. Ga+ distribution in the layers after irradiation was also simulated using the SRIM2003 package. Ga+ irradiation weakened the intensity of the (111) peak of the antiferromagnetic IrMn (111) layer, decreased surface roughness as well as exchange bias field and pinned layer coercive force, while increasing the free layer coercive force. However, the multilayer exchange bias field of the spin-valve film under the reverse saturation field after Ga+ irradiation did not change with time.

Intensification of bituminous coal and lignite oxidation by copper-based activating additives

The oxidation of lignite and bituminous coal samples modified by 5 wt% (in terms of dry salt) addition of copper salts Cu(NO3)2, CuSO4, and Cu(CH3COO)2 was studied. The samples’ reactivity was studied by thermogravimetry within a temperature range of 45–600 °C at a heating rate of 2.5 °C/min in an oxidizing environment. The introduction of activating additives has resulted in a significant decrease in the temperature of intense oxidation onset (ΔTi = 20/94 °C), in a reduction in the sample residence time in the volatile matter release region (Δte = 2/22 min) and the total duration of the coal combustible mass oxidation (Δtf = 8/14 min). The Friedman method was used to calculate the activation energy values for the oxidation process of the modified samples. The maximum change in activation energy values was observed for the bituminous coal sample. The possible mechanism behind the action of the copper-salt additives, which activate the oxidation of lignite and bituminous coal, is discussed. According to the data of mass spectrometric analysis, the concentration of NOx in the reaction products decreases as the temperature of the activated oxidation process is shifted towards the low-temperature region.

Research of thermal destruction dynamics of coal particles in oxidizing medium with copper nitrate

Oxidation of brown coal containing 5% by weight of (Cu(NO3)2) initiation additive has been studied. The experiment was conducted using thermogravimetric analysis at a heating rate of 2.5°C/min up to a maximum temperature of 600°C in air. Based on DTA results, the oxidation characteristics were analytically evaluated. It has been discovered that addition of (Cu(NO3)2) initiation agent leads to a significant decrease of initial temperature of oxidation, which serves to shift the reaction to the low-temperature region. The effect of the initiation additive also manifested in significant reduction of sample residence time within sublimation of volatile compounds. Mass-spectrometric analysis has revealed the presence of NOx (intense peak at 180°C) in oxidation products of the modified sample, which is explained by decomposition of copper nitrate. SEM results for the coal partially oxidized in the muffle furnace indicate significant change of surface and internal structure of the modified sample particles.

The influence of nanoxide additives on the characteristics of thermal decomposition of ammonium nitrate

Thermal decomposition of ammonium nitrate (NH4NO3) containing 5% (by weight) of catalytic additives in the form of metal oxides (NiO, CuO, Co2O3) has been studied. The experiment was performed by thermogravimetric analysis at a heating rate of 5°C/min to a maximum temperature of 800°C in argon atmosphere. Based on the results of DTA, physical and kinetic characteristics of thermal decomposition we analytically assessed. The addition of catalytic agents was found to lead to a decrease of onset temperature of active NH4NO3 decomposition, which promotes the reaction shift to the low-temperature region. The effect of the initiation additive manifested in a significant reduction of sample residence time within preheating stage (Δti = 5.2 min). In presence of catalytic additives the total time of thermal decomposition tf was found to decrease. The greatest change of Δtf (2.8 minutes) was recorded for the sample modified by addition of Co3O4. The maximum decrease of the average activation energy (for decomposition of 5%Co3O4/NH4NO3) was 14.2 kJ/mol.

Binding studies based on ultrafast affinity extraction and single- or two-column systems: Interactions of second- and third-generation sulfonylurea drugs with normal or glycated human serum albumin

Ultrafast affinity extraction was evaluated and used with microcolumns containing human serum albumin (HSA) to measure the global affinity constants and dissociation rate constants for several second- and third-generation sulfonylurea drugs with solution-phase normal HSA or glycated HSA. Glibenclamide, glimepiride and glipizide were used as model drugs for this work. Both single- and two-column systems were considered for the analysis of global affinities for the model drugs. These methods were optimized with respect to the flow rates, column sizes and sample residence times that were employed with each drug for ultrafast affinity extraction. Data acquired with single-column systems were further utilized to estimate the dissociation rate constants for normal HSA and glycated HSA with the given drugs. The binding constants obtained by the single- and two-column systems showed good agreement with each other and with values obtained from the literature. Use of a single-column system indicated that levels of glycation found in controlled or advanced diabetes resulted in a 18–44% decrease in the overall binding strength of the model drugs with HSA. Although the two-column system allowed work with smaller free drug fractions and clinically-relevant drug/protein concentrations, the single-column system required less protein, provided better precision, and was easier to use in binding studies.

A Monte Carlo Method to Quantify the Effect of Reactor Residence Time Distribution on Polyolefins Made with Heterogeneous Catalysts: Part IV—Intraparticle Transfer Resistance Effects

AbstractAn integrated Monte Carlo/polymeric multilayer model (MC/PMLM) is developed to predict the polymer particle size distribution (PSD) and microstructures of polyolefins made with heterogeneous catalysts under intraparticle mass transfer limitations. The Monte Carlo model is used to randomly sample particle sizes and residence times from the catalyst PSD and reactor residence time distribution (RTD), respectively, while the polymeric multilayer model is used to describe single‐particle growth considering intraparticle mass transfer resistances. The effect of reactor RTD, catalyst PSD, and polymerization kinetics on polymer PSD and polymer properties is systematically investigated with the MC/PMLM for the first time. The results show that intraparticle mass transfer limitations under various operating conditions may affect polymer PSD and polymer properties. In addition, due to the versatility of the Monte Carlo approach, the proposed MC/PMLM is adequate to describe complex cases, such as reactor systems with arbitrary RTD and catalyst particles having any PSD.

Growth of Tl-1223 superconducting thin films by rapidly heating-up sintering technology

Owing to high critical temperature (125 K) and high upper critical field, TlBa2Ca2Cu3O9 (Tl-1223) superconductor is a kind of superconducting power transmission material working at liquefied natural gas temperature, and it has a great potential application value in the strong and weak electric field. In this work, the Tl-1223 superconducting films are fabricated by rapidly heating-up sintering technology (RHST) on (00l) lanthanum aluminate substrates. The Tl-Ba-Ca-Cu-O target is used as a sputtering source to deposit the precursor films by the radio-frequency magnetron sputtering technique. The Tl-contained pellets, named annealing targets, are fabricated by the solid-state reaction of stoichiometric quantities of Tl2O3, BaO2, CaO and CuO powders with an initial cation ratio of m Tl:Ba:Ca:Cu=0.4-1.8:2:2:3. The amorphous precursors together with the annealing target providing Tl source are sealed in a silver foil and annealed at 820℃ for 5 min in argon atmosphere, then converted into Tl-1223 superconducting phase. The heating rates are set at 2.5℃/s from room temperature to 350℃, 5℃/s from 350℃ to 650℃, and 35℃/s from 650℃ to 820℃, respectively. The prepared films are characterized by X-ray diffraction and scanning electron microscope. In the conventional low heating rate process, all of the precursor films sintered together with the annealing targets containing different Tl content are first converted into Tl-2212 superconducting phase. That is because the sample residence time in the phase transition temperature range of Tl-2212 is longer, while the phase-formed temperature of Tl-2212 is lower than that of Tl-1223. In the RHST, when the metal ion molar ratio of Tl to Ba in the annealing target is 1.8:2, the main phase of the film is (00l)-oriented Tl-2212. In addition, the film also contains a small number of Tl-2223 grains. On reducing the ratio to 1:2, the film is composed of Tl-1212, Tl-2212, Tl-1223 and Tl-2223 grains. As the ratio decreases to 0.8:2, the film contains the (00l)-oriented Tl-1223 grains and traces of Tl-2223 grains. With the ratio decreasing to 0.4:2, purely c-axis oriented Tl-1223 film is obtained. The critical transition temperature Tc onset of the as-grown film is only 103 K. The film annealed again in oxygen gas has a dense crystal structure and excellent electrical properties. The Tc onset of the sample is about 116 K, and the critical current density Jc is about 1.5 MA/cm2 (77 K, 0 T). The experimental results show that the new sintering process to grow Tl-based films has several advantages such as the short processing cycles, less raw-material consumption, and low production cost.

Influence of CuSO4 initiation additive on kinetic characteristics of coal oxidation and pyrolysis processes

Coals oxidation and pyrolysis processes of different metamorphic grades containing 5%wt of initiation additive were studied. The experiment was performed by thermogravimetric analysis method at a heating rate of 2.5°C/min to a maximum temperature of 600°C in an atmosphere of air and nitrogen. Based on the results of TGA, an analytical evaluation of kinetic characteristics of pyrolysis and oxidation processes was conducted. It has been established that addition of CuSO4 initiating agent leads to significant decrease in the initial temperature of oxidation and pyrolysis processes, which promotes the shift of the reaction to a low-temperature region. Change of the initial reaction temperature ΔTi for oxidation process was 30°C, ΔTd for pyrolysis was 45°C. Effect of initiation additive was also expressed in significant reduction of sample residence time within volatile substances sublimation zone: for oxidation Δti was 14 minutes, for pyrolysis Δtd was 18 min. For modified sample characterized by lower stage of metamorphism, the decrease in oxidation time Δtf was the greatest (22 min), which is explained by the high content of volatile substances. According to mass-spectrometric analysis, presence of SO2 (intense peaks at 290°C and 440°C) was recorded in modified samples oxidation products, which is explained by partial hydrolysis of copper sulfate.

Novel functionalities of hybrid paper-polymer centrifugal devices for assay performance enhancement.

The presented work demonstrates novel functionalities of hybrid paper-polymer centrifugal devices for assay performance enhancement that leverage the advantages of both paper-based and centrifugal microfluidic platforms. The fluid flow is manipulated by balancing the capillary force of paper inserts with the centrifugal force generated by disc rotation to enhance the signal of a colorimetric lateral flow immunoassay for pathogenic E. coli. Low-cost centrifugation for pre-concentration of bacteria was demonstrated by sample sedimentation at high rotational speeds before supernatant removal by a paper insert via capillary force after deceleration. The live bacteria capture efficiency of the device was similar to a commercial centrifuge. This pre-concentrated sample when combined with gold nanoparticle immunoconjugate probes resulted in a detection limit that is 10× lower than a non-concentrated sample for a lateral flow immunoassay. Signal enhancement was also demonstrated through rotational speed variation to prevent the flow for on-device incubation and to reduce the flow rate, thus increasing the sample residence time for the improved capture of gold nanoparticle-bacteria complexes in an integrated paper microfluidic assay. Finally, multiple sequential steps including sample pre-concentration, filtration, incubation, target capture by an integrated paper microfluidic assay, silver enhancement and quenching, and index matching were completed within a single device. The detection limit was 105 colony forming units per ml, a 100× improvement over a similar paper-based lateral flow assay. The techniques utilize the advantages of paper-based microfluidic devices, while facilitating additional functionalities with a centrifugal microfluidic platform for detection performance enhancement in a low-cost, automated platform amenable to point-of-care environments.

An improved, automated whole air sampler and gas chromatography mass spectrometry analysis system for volatile organic compounds in the atmosphere

Abstract. Volatile organic compounds were quantified during two aircraft-based field campaigns using highly automated, whole air samplers with expedited post-flight analysis via a new custom-built, field-deployable gas chromatography–mass spectrometry instrument. During flight, air samples were pressurized with a stainless steel bellows compressor into electropolished stainless steel canisters. The air samples were analyzed using a novel gas chromatograph system designed specifically for field use which eliminates the need for liquid nitrogen. Instead, a Stirling cooler is used for cryogenic sample pre-concentration at temperatures as low as −165 °C. The analysis system was fully automated on a 20 min cycle to allow for unattended processing of an entire flight of 72 sample canisters within 30 h, thereby reducing typical sample residence times in the canisters to less than 3 days. The new analytical system is capable of quantifying a wide suite of C2 to C10 organic compounds at part-per-trillion sensitivity. This paper describes the sampling and analysis systems, along with the data analysis procedures which include a new peak-fitting software package for rapid chromatographic data reduction. Instrument sensitivities, uncertainties and system artifacts are presented for 35 trace gas species in canister samples. Comparisons of reported mixing ratios from each field campaign with measurements from other instruments are also presented.

A modified continuous flow apparatus for gas solubility measurements at high pressure and temperature with camera system

A continuous flow apparatus with a camera system was modified for high-pressure gas–liquid equilibrium measurements. The continuous flow method is suitable for phase equilibrium measurements of heat-sensitive materials, such as heavy oils and bio-based feedstocks, which are refined in hydroprocesses at high temperatures and pressures. Benefits of the modified apparatus are a short residence time of a sample in the heated zone and no sampling is required. In contrast, the static method is usually impractical with the heat-sensitive materials due to the long residence time of sample in the equilibrium cell. In this study, the continuous flow apparatus and the measurement method was adopted and validated. The validation was conducted by measuring hydrogen solubility in toluene and n-hexadecane at high temperatures and pressures (T=461–575K, P=5–10MPa) and comparing the results with the literature values. Relative average pressure deviation was found to be 3.8% for measurements of this work when the PC-SAFT equation of state was optimized against literature values while the relative average pressure deviations for the literature data sets varied from 0.9% to 4.7%. Thus, the quality of measurements was shown to be excellent. In addition, hydrogen solubility was also measured in n-octadecane in order to obtain new data for this system. All measured systems were modeled with the PC-SAFT and the original and modified Peng–Robinson equations of state in order to simplify the validation of the measurement method and to compare the performance of the selected models. PC-SAFT was found to predict phase behavior of the systems precisely whereas the predictions of the Peng–Robinson modifications were less precise.

Sampling system influence on gaseous air pollution measurements

Efficient sampling systems are key components of ambient air pollution measurement systems used for both regulatory and research purposes. Gaseous sampling systems were tested at 83 monitoring sites incorporating three different sampling system designs. The mean sample collection efficiency was 98% for CO, 99.1% for NO2, 88.7% for O3 and 96.7% for SO2. In most cases, the test uncertainties were greater than the 2% threshold for sample losses allowed by the relevant European Standards. These uncertainties were largely due to repeatability and signal noise within the equipment being tested and the low test gas concentrations required to avoid conditioning the sampling system. There is therefore little scope for improving the test uncertainty. For O3, test uncertainties and repeatability issues meant that firm conclusions could not be reached. For other pollutants, manifold systems offered no systematic advantages over simple PTFE tubing. PTFE tubes should therefore be favoured in site design, providing sample residence times can be met. The high average sampling efficiencies of PTFE sample tubes combined with the uncertainties inherent in the test procedure suggest that regular testing is not worthwhile for this type of sampling system providing sample lines are regularly changed or cleaned. Where a manifold is used, periodic maintenance should include cleaning, as well as flow and leak tests.

Pore development and combustion behavior of gasified semi-char in a drop tube furnace

A fly ash sample was collected en-suite from an industrial circulating fluidized bed (CFB) gasifier. The fly ash is herein referred to as semi-char (partially burnt char) as it still contained a high amount of carbon. CFB gasification involves long sample residence times and the resulting residual chars are expected to be different from conventional chars from processes such as pulverized coal gasification or chars prepared under laboratory furnaces where usually, residence times are relatively much shorter.In this study, the semi-char was burned in a flat flame reactor (FFR) under oxygen conditions. The semi-char reactivity, pore development and microstructure were then used to characterize its combustion behavior.The ‘raw’ semi-char, before the FFR oxygen reactions was porous with a dominant meso–macro pore structure which is associated with its formation path in the CFB gasifier. A linear monotonic decrease with conversion in both internal surface area and pore volume was then observed while pore size increased slightly with conversion.Pore structure and reactivity data were used to determine the effectiveness factor at various stages of conversion of the semi-char. Effectiveness factor values reveal the semi-char reactions to be close to kinetic controlled condition.

Hybrid flow analyzer for automatic hollow-fiber-assisted ionic liquid-based liquid-phase microextraction with in-line membrane regeneration

The proof-of-concept of a new methodology for in-line hollow-fiber (HF)-assisted three-phase liquid-phase microextraction (LPME) allowing for handling of the feed and acceptor aqueous solutions and of minute volumes of the organic extracting phase in a programmable flow mode is reported in this paper. The flow analyzer fosters in-line anchoring of ionic-liquid-laden extracting solution (10 % (v/v) methyltrioctyl ammonium chloride in kerosene) in the pores of a single-strand microporous polypropylene HF, and regeneration of the liquid-phase membrane itself for each individual analysis cycle in a fully automated mode. Using hexavalent chromium as a model analyte and 1,5-diphenylcarbazide as a chromogenic probe in the acceptor solution, the flow-based HF-LPME hyphenated system was harnessed to the clean-up of troublesome samples (viz., domestic wastewater and soil leachates) with concomitant enrichment of target species. Distinct extraction modes and chemistries were assessed for enhanced Cr(VI) permeability. A single sample plug was subjected to a twofold backward-forward flow extraction so as to decrease the thickness of the boundary layer at the HF shell side for improved extraction efficiency. Under the optimized physicochemical variables, a limit of detection of 4.6 μg L(-1) Cr(VI), a dynamic linear range of up to 500 μg L(-1) and intermediate precision better than 10 % were obtained for a sample volume of 2.8 mL buffered at pH 4 and a volume of organic extractant of 120 μL, with an enrichment factor of ca. 11 for a sample residence time in the donor compartment of merely 4.5 min. Analyte recoveries in domestic wastewaters were ≥83 % using external calibration with relative standard deviations better than 14 %, thereby demonstrating the expedient clean-up of samples with elevated content of dissolved organic carbon. The automatic HF-LPME method was validated in terms of bias against the SRM 2701 (NIST soil) preceded by the EPA alkaline digestion method 3060A. No significant differences between Cr(VI) concentration as obtained with the automatic HF-LPME system (546 ± 57 mg kg(-1)) and the certified value (551.2 ± 17.2 mg kg(-1), expressed as mean ± combined uncertainty) were encountered at the 0.05 significance level.

Evolution of syngas from cardboard gasification

Evolutionary behavior of syngas characteristics evolved during the gasification of cardboard has been examined using a batch reactor with steam as a gasifying agent. Evolutionary behavior of syngas chemical composition, mole fractions of hydrogen, CO and CH 4, as well as H 2/CO ratio, LHV (kJ/m 3), hydrogen flow rate, and percentage of combustible fuel in the syngas evolved has been examined at different steam to flow rates with fixed mass of waste cardboard. The effect of steam to carbon ratio as affect by the steam flow rate on overall syngas properties has therefore been examined. A new parameter called coefficient of energy gain (CEG) has been introduced that provides information on the energy gained from the process. This new parameter elaborates the importance of optimizing the sample residence time in the reactor.

Development of an open-tubular trypsin reactor for on-line digestion of proteins

A study was initiated to construct a micro-reactor for protein digestion based on trypsin-coated fused-silica capillaries. Initially, surface plasmon resonance was used both for optimization of the surface chemistry applied in the preparation and for monitoring the amount of enzyme that was immobilized. The highest amount of trypsin was immobilized on dextran-coated SPR surfaces which allowed the covalent coupling of 11 ng mm−2 trypsin. Fused-silica capillaries were modified in a similar manner and the resulting open-tubular trypsin-reactors having a pH optimum of pH 8.5, display a high activity when operated at 37 °C and are stable for at least two weeks when used continuously. Trypsin auto-digestion fragments, sample carry-over, and loss of signal due to adsorption of the protein were not observed. On-line digestion without prior protein denaturation, followed by micro-LC separation and photodiode array detection, was tested with horse-heart cytochrome C and horse skeletal-muscle myoglobin. The complete digestion of 20 pmol μL−1 horse cytochrome C was observed when the average residence time of the protein sample in a 140 cm ×50 μm capillary immobilized enzyme reactor (IMER) was 165 s. Mass spectrometric identification of the injected protein on the basis of the tryptic peptides proved possible. Protein digestion was favorable with respect to reaction time and fragments formed when compared with other on-line and off-line procedures. These results and the easy preparation of this micro-reactor provide possibilities for miniaturized enzyme-reactors for on-line peptide mapping and inhibitor screening.