Microdialysis-integrated HPLC system with dual-electrode detection using track-etched membrane electrodes for in vivo monitoring of dopamine dynamics

A capillary high-performance liquid chromatography (HPLC) system equipped with a dual-electrode detector utilizing track-etched membrane electrodes (TEMEs) was combined with a microdialysis sampling setup. The electrochemical detector benefits from the high electrolysis efficiency of TEMEs, allowing for calibration-free coulometric detection and simplifying data analysis to determine the dopamine recovery through a dialysis probe. Additionally, this system was used for in vivo monitoring of dopamine in the right striatum of a mouse brain. Temporal changes in dopamine levels, including an exponential decay immediately after the dialysis probe insertion and an excess release of dopamine induced by a high concentration of potassium ions, confirmed the system's proper operation. Furthermore, subsequent measurements following the intraperitoneal injection of mirtazapine showed no increase in dopamine levels in the right dorsal striatum. The dual-electrode system displayed characteristic dopamine detection behavior, with anodic and cathodic peak pairs indicative of reversible electrochemical reactions. This capability facilitated the identification of the dopamine peak within the complex chromatogram of the mouse brain dialysate. The consistency between dopamine collection efficiency from standard solutions and dialysate indicated the absence of interfering electroactive substances overlapping with the dopamine peak in the chromatogram. This integrated analysis system successfully tracked temporal fluctuations in dopamine concentration within the mouse brain.

Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences


Digital-movie-based flow colorimetry for pH measurement with universal indicators


Direct analysis of airborne microplastics collected on quartz filters by pyrolysis-gas chromatography/mass spectrometry

Journal of Analytical and Applied Pyrolysis


Determination of trace perchlorate in river water by ion chromatography with online matrix removal and sample concentration

This paper proposes a simple ion chromatographic approach to determine trace amounts of perchlorate in river water samples. Determination of the trace perchlorate by ion chromatography typically faces two challenges: interference by matrix ions such as chloride, nitrate, and sulfate in the samples and insufficient detection sensitivity. In the present study, online pretreatment of the samples with an OnGuard II Ba/Ag/H disposable sample pretreatment cartridge prevented the sulfate peak tailing from overlapping with the perchlorate peak on the chromatogram. In addition, the matrix removal enabled as large as 10 mL of sample to be loaded into a high exchange capacity anion concentrator, significantly improving perchlorate's detection sensitivity. The proposed approach achieved a detection limit (S/N = 3) of 0.046 µg L without using a costly mass spectrometer and successfully determined sub µg L levels of perchlorate in river water.


Airborne hydrophilic microplastics in cloud water at high altitudes and their role in cloud formation


Practical usefulness of observing the free tropospheric acidic gases with a parallel plate wet denuder coupled ion chromatograph


Feedback standard addition method coupled flow injection analysis Validation by spectrophotometric determination of nitrite in seawater


Integrated continuous flow method with dual feedback-based controls for online analysis and process control

The concept of an integrated automated continuous flow method with dual feedback controls is presented for diluting a stock solution to provide a solution of a given concentration. The one control is used for the online process monitoring by a feedback-based flow ratiometry, where the product (the diluted liquid) is titrated through the rapid bidirectional scan of the product/reagent flow ratio. The feedback control limits the scanning to the necessary range to increase the analytical throughput. The other control is used for the process control to output the product with a preset concentration. The merging ratio of the stock solution and a solvent (diluent) is changed based on the information from the online analysis. The concept was verified by applying it to producing 0.1 mol dm CHCOOH. When the stock concentration was changed from 0.1 (reference concentration) to 0.3 and then 0.2 mol dm, the system searched for the suitable merging ratio and converged the output concentration to the reference value within 7.43 min with a relative error below 1.05%. The mean throughput rate of the process analysis was 11.2 titrations min. Successful results were also obtained for the 0.1 mol dm HCl production. The present concept could be the basis for process control with reduced wasteful output and effluent treatment with eco-friendly treated water discharge, resulting in the contribution to SDGs' goals of 6 (Clean water and sanitation), 9 (Industry, innovation and infrastructure), and 14 (Life below water).


Interference of high degrees salt on spectrophotometric flow injection analysis Quantitative error of nitrite from schlieren effect and salt effect

フローインジェクション吸光光度法における高濃度塩の干渉 –シュリーレン効果及び塩効果による亜硝酸イオンの定量誤差–


Noise Reduction Using Fourier Analysis in Microsoft Excel - Improvement of the Signal-to-Noise Ratio in Flow Injection Analysis -

Microsoft Excelのフーリエ解析を用いるノイズ信号の軽減 -フローインジェクション分析法におけるシグナルノイズ比の向上

In flow injection analysis (FIA), the baseline noise of the detection signal is an important parameter that determines the detection sensitivity. In this study, we applied the Fourier analysis/inverse Fourier analysis of Microsoft Excel to the detection signal of FIA to decrease the noise signal. The Fourier analysis of the detection signal for a sample of 0.06 mg L-1 NO2- showed many frequency components with amplitudes less than 0.04 mV. After removing these frequency components, inverse Fourier analysis was applied, and a smooth detection signal was obtained. Even with a sample of 2.50 mg L-1 NO2-, the noise signals were successfully removed using the Fourier/inverse Fourier analysis. The signal-to-noise ratio (S/N) of NO2- was improved by ca. 15 times. We concluded that removing noise signals by Fourier analysis effectively improves the S/N of FIA.


Triangular-wave controlled amplitude-modulated flow analysis for extending dynamic range to saturated signals

We have applied our amplitude-modulated flow analysis concept to extend the dynamic range to saturated analytical signals. Sample solution, the flow rate F of which is periodically varied with a triangular control signal V, is merged with a reagent solution delivered at a constant flow rate F. While the total flow rate F is kept constant, a diluent with F-(F + F) flow rate is aspirated from the third channel. The analytical signal V obtained downstream is processed by fast Fourier transform to obtain the amplitudes of the wave components in V. When the sample concentration C is low, V shows a triangular profile like V; the sum of the amplitudes ΣA is proportional to C. When C is high, V shows a trapezoidal profile because of the V saturation. A linear calibration curve can also be obtained for such saturated signals by plotting CΣA against C. The proof of the concept is validated by applying it to spectrophotometric determinations of a dye (Methylene Blue) and colored complexes of Fe - phenanthroline and Fe - Tiron.


Inner product of RGB unit vectors for detecting color transition: application to feedback-based flow ratiometric titration

The inner product (IP) of RGB unit vectors' approach for detecting color transition has further been applied to a feedback-based flow ratiometric titration, including nonaqueous titration. While the flow ratio of titrand/titrant containing an indicator was varying, the video image of the merged solution was taken with a digital microscope downstream. The indicator's color was converted to an RGB unit vector. The change in IP between vectors was used for determining the equivalence point. The concept was successfully applied to the determinations of drug and vinegar samples with reasonable throughput rate (> 18 s/titration) and precision (RSD < 4.4%).


Parallel plate wet denuder coupled ammonia transfer device-conductivity detector for near-real-time monitoring of gaseous ammonia


On-line analysis of free-tropospheric water-soluble acidic gases and particulate anions on the summit of Mt. Fuji, Japan


Development of a mugineic acid family phytosiderophore analog as an iron fertilizer

Iron (Fe) is an essential nutrient, but is poorly bioavailable because of its low solubility in alkaline soils; this leads to reduced agricultural productivity. To overcome this problem, we first showed that the soil application of synthetic 2'-deoxymugineic acid, a natural phytosiderophore from the Poaceae, can recover Fe deficiency in rice grown in calcareous soil. However, the high cost and poor stability of synthetic 2'-deoxymugineic acid preclude its agricultural use. In this work, we develop a more stable and less expensive analog, proline-2'-deoxymugineic acid, and demonstrate its practical synthesis and transport of its Fe-chelated form across the plasma membrane by Fe(III)·2'-deoxymugineic acid transporters. Possibility of its use as an iron fertilizer on alkaline soils is supported by promotion of rice growth in a calcareous soil by soil application of metal free proline-2'-deoxymugineic acid.


Amplitude modulated flow analysis for speciationProof of concept by quantification of Fe2+ and Fe3+ ions


Inner Product of RGB Unit Vectors for Simple and Versatile Detection of Color Transition


On-line collector for water-soluble atmospheric particulate matter compatible with a parallel plate wet denuder

ウエットデニューダーに対応した水溶性大気粒子状物質のオンライン捕集器


Rapid flow injection analysis by partial least squares regression -Validation by a spectrophotometric determination of iron with 1,10-phenanthroline-

部分的最小二乗法によるフローインジェクション分析の迅速化 -フェナントロリン吸光光度法を用いる鉄の定量による検証-


Miniaturized low-pressure ion-exchange module and its application to an acidic eluent generator for open tubular ion chromatography

We describe a miniaturized eluent generator (MEG), which can be integrated into open tubular capillary column ion chromatography (OTCC-IC). The MEG consists of one central eluent channel and two feed acid chambers, with each phase isolated by a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM). Pure water flowed through the central eluent channel while acid solution (HA) was fed to both chambers. Applying the electric field to the MEG, H+ and A- simultaneously and respectively through the CEM and AEM to form HA in the central channel. The MEG successfully produced tartaric acid and 2,6-pyridinedicarboxylic acid as the eluent for cation OTCC-IC. The gradient elution improved the peak resolution and analytical window for five common cations (Na+, NH4+, K+, Ca2+, Mg2+).


Online Analysis of Water-soluble Acidic Gases and Anions in Particles at the Southeastern Foot of Mt. Fuji

富士山南東麓における水溶性酸性ガス及び粒子状物質に含まれる陰イオンのオンライン観測

During the summer of 2018, we monitored the concentrations of water-soluble acid gases and particulate anions at the southeastern foot (1284 m a.s.l.) of Mt. Fuji, Japan, using gas/particle-ion chromatographs. All samples analyzed contained quantifiable levels of anions. The average concentrations of acid gas and particulate anion concentrations were, respectively, 1.10±0.37 nmol m-3 for HCl, 3.49±1.72 nmol m-3 for HONO, 1.23±0.59 nmol m-3 for HNO3, 0.33±0.20 nmol m-3 for SO2, 3.61±3.69 nmol m-3 for Cl-, 0.65±0.22 nmol m-3 for NO2-, 4.29±2.98 nmol m-3 for NO3-, and 4.47±3.57 nmol m-3 for SO42-. We found that the concentration of soluble acidic gases increased during the daytime, while no characteristic diurnal patterns were observed in the particulate anions.


Predictive evaluation of powder X-ray diffractogram of pharmaceutical formulation powders based on infrared spectroscopy

To ensure quality and stability, monitoring systems are recommended to analyze pharmaceutical manufacturing processes. This study was performed to predict powder X-ray diffraction (PXRD) patterns of formulation powders through attenuated total reflectance (ATR)-infrared (IR) spectroscopy in a nondestructive manner along with chemometrics. Caffeine anhydrate, acetaminophen, and lactose monohydrate were grinded at six weight ratios. The six sample groups were evaluated using ATR-IR spectroscopy and PXRD analysis. Partial least squares models were constructed to predict the PXRD intensities of the samples from the ATR-IR spectra. The prediction accuracy on the prepared PLS regression models was as high as R2 = 0.993. Linear relationships were obtained between the prediction data set and reference PXRD intensity at each degree. 2D PLS regression coefficient analysis enabled the analysis of the correlation between PXRD patterns and IR spectra.


軸方向分散を抑えた陽イオン交換モジュールとイオンクロマトグラフィーへの応用

軸方向分散を抑えた陽イオン交換モジュールとイオンクロマトグラフィーへの応用


Introduction of Air-Segmentation Approach to Flow Titration by Feedback-based and Subsequent Fixed Triangular Wave-controlled Flow Ratiometry

An air-segmentation approach has been introduced to a feedback-based and subsequent fixed triangular wave-controlled flow ratiometry to suppress axial dispersion in flow titration. The flow rate of a base solution containing an indicator is linearly varied with a control signal, V, supplied by a computer. The solution is merged with an acid solution under a constant total flow rate. Air is introduced to the merged solution in order to segment the solution with air bubbles. Both phases are led to a UV/Vis detector without phase separation. Air signals are removed by signal processing. The effect of the lag time between the merging of solutions upstream and the sensing of the corresponding signal downstream is offset by feedback-based upward and downward V scans, and thus the V that gives the equivalence composition is determined. Subsequently, fixed triangular wave control is applied to a narrower V range with a higher scan rate to enhance the throughput rate (maximally 11.8 titrations/min). Air-segmentation has been found to be effective to reduce axial dispersion and to preserve the titrand/titrant composition upon their just being merged. Consequently, the applicable range is extended especially to lower titrand concentration. The proposed method has been successfully applied to various acid-base titrations, including the nonaqueous titration of the Japanese Pharmacopoeia drug.


Track-etched membrane-based dual-electrode coulometric detector for microbore/capillary high-performance liquid chromatography


富士山体を用いた夏季自由対流圏における雲水中揮発性有機化合物の観測

富士山体を用いた夏季自由対流圏における雲水中揮発性有機化合物の観測

Journal of Japan Society for Atmospheric Environment


Quantification of overlapped peaks with partial least squares regression: Open tubular ion chromatography for sodium and ammonium ions


Effects of temperature on terahertz spectra of caffeine/oxalic acid 2:1 cocrystal and its solid-state density functional theory

Journal of Drug Delivery Science and Technology


Unprecedented High Throughput Titration by Feedback-Based and Subsequent Fixed Triangular Wave-Controlled Flow Ratiometry and Its Application to Quantification of Japanese Pharmacopoeia Drugs


Mechanochemical synthesis of zinc chloroapatite and evaluation of its crystallinity by attenuated total reflection - infrared spectroscopy and principal component analysis


Bilayer tablet dissolution kinetics based on a degassing cyclic flow UV-vis spectroscopy with chemometrics

Dissolution kinetics of a bilayer direct compress tablet was evaluated by using degassing cyclic flow UV-visible (Vis) spectroscopy with chemometrics. The model bilayer nicotinamide (NA)-pyridoxine hydrochloride (PH) 100.0 mg tablets were prepared via the dual compress method. The fast diffusion layer of the bilayer tablet contained nicotinamide, microcrystal cellulose, beta-lactose, magnesium stearate, and croscarmellose sodium. The slow release layer contained pyridoxine hydrochloride and carnauba wax. The monolayer direct compress tablets were prepared as dual ingredient (API)s formulation tablets. The degassing cyclic flow UV-Vis spectroscopy dissolution test was carried out using the prepared tablets. The dissolution test conditions were as follows: time, 60 min; temperature, 37°C; paddle method, 50 rpm, and UV-Vis spectra measurement 1 time/min. The UV-Vis spectra of the flow solution were measured in the range of 240-380 nm. API concentration was predicted by partial least squares (PLS) regression models based on UV-Vis spectra. The dissolution kinetics of the bilayer and monolayer tablets were evaluated based on the UV-Vis spectra with the predicted API concentration profile. The degassing flow system could prevent air bubbles in the flow cell at 1800 min. Therefore, simultaneous determination of NA and PH concentration based on the PLS regression was suggested to have high accuracy. PLS regression has advantages over the conventional λ absorbance method of simultaneous determination. We found that the kinetics of the separated bilayer tablet can be evaluated by the same kinetic analysis method used for the single layer model tablet.


Prediction of differential scanning calorimetry curve of theophylline direct compression model tablet using Raman spectra


Effect of amino acid on calcium phosphate phase transformation: attenuated total reflectance-infrared spectroscopy and chemometrics


Humic-Like Substances Global Levels and Extraction Methods in Aerosols


Flow injection analysis of nitrite nitrogen in seawater introducing standard addition method


Diurnal variations in partitioning of atmospheric glyoxal and methylglyoxal between gas and particles at the ground level and in the free troposphere


Internal Standard-Amplitude Modulated Multiplexed Flow Analysis

A new concept of flow analysis, internal standard-amplitude modulated multiplexed flow analysis, is proposed. A proof of concept was verified by applying it to the determination of ferrous ion (Fe) by 1,10-phenanthroline (o-Phen) spectrophotometry. The flow rates of sample solutions containing Methylene Blue (MB) as an internal standard substance were sinusoidally varied at different frequencies. The solutions were merged with a color reagent (o-Phen) solution, while the total flow rate was held constant. Downstream, analytical signals were monitored at the maximum absorption wavelengths of Fe-o-Phen complex and of MB (510 and 644 nm, respectively). The signals were respectively analyzed by fast Fourier transform. The concentrations of the analytes in respective samples were simultaneously determined from the amplitudes of the corresponding wave components. The precision, linearity of the calibration curve, limit of detection and robustness against deliberate fluctuation in flow rate were greatly improved by introducing the internal standard method. Good recoveries of around 100% were obtained for Fe spiked into real water samples.


Dry Mechanochemical Synthesis of Caffeine/Oxalic Acid Cocrystals and Their Evaluation by Powder X-Ray Diffraction and Chemometrics

We report the effects of dry mechanochemical synthesis conditions on the crystallization of caffeine (CA) and oxalic acid (OX) 2:1 cocrystal. CA anhydrate and OX dihydrate were grinded at various temperatures, rotation speeds, and grinding time. The cocrystal was also synthesized by an organic solvent evaporation method, as a reference. The produced samples were measured by a powder X-ray diffraction (PXRD) analysis. The PXRD spectra suggest that the grinded cocrystal has a lower crystallinity than the evaporated one. The diffractograms for the cocrystals synthesized by 2 kinds of methods were further evaluated by multivariate curve resolution-alternating least squares method. Sources of the mathematical models constructed were assigned to the cocrystal and unreacted mixture of CA and OX dihydrate. The present approach is concluded to be useful for the improvement of pharmaceutical property because cocrystallization is closely relating to the solubility characteristics, bioavailability, stability, and so on of drugs.


Mechanochemical synthesis of chloroapatite and its characterization by powder X-ray diffractometory and attenuated total reflection - infrared spectroscopy


High Throughput Titration Based on Variable and Fixed Triangular Wave Controlled Flow Radiometry with LED-Photodiode Detector


High Time-Resolution Monitoring of Free-Tropospheric Sulfur Dioxide and Nitric Acid at the Summit of Mt. Fuji, Japan


クリーンルーム雰囲気中のアンモニア及びアミンガスを監視するウエットデニューダ方式の自動モニタ


Quantification of pharmaceutical compounds based on powder X-ray diffraction with chemometrics

We propose an approach for the simultaneous determination of multiple components in pharmaceutical mixed powder based on powder X-ray diffraction (PXRD) method coupled with chemometrics. Caffeine anhydrate, acetaminophen and lactose monohydrate were mixed at various ratios. The samples were analyzed by PXRD method in the ranges of 2=5.00-30.0 and 35.0-45.0 degrees. Obtained diffractograms were analyzed by conventional peak intensity method, multi curve resolution (MCR)-alternating least squares (ALS) method and partial least squares (PLS) method. Constructed PLS models can most accurately predict the concentrations among different methods used. Each regression vector of PLS correlates not only to the compound of interest but also to the coexisting compounds. The combination of PXRD and PLS methods is concluded to be powerful approach for analyzing multi components in pharmaceutical formulations.


Online Analysis of Water-soluble Acidic Gases and Anions in PM2.5 at Tokushima City in Winter of 2015

2015年冬季の徳島市における水溶性酸性ガス及びPM2.5に含まれる陰イオンのオンライン分析

This paper describes a simultaneous analytical system used for atmospheric water-soluble acidic gases and anions in PM2.5. The analytical system, consisting mainly of a parallel-plate wet denuder, mist chamber-hydrophobic filter based particle collector, and ion chromatograph provides automatically two acidic gas and two PM2.5 data with in one hour. We applied the system to the continuous measurement of air pollutants at Tokushima, Japan in the winter of 2015, and obtained meaningful data in 97.9 % of the sampling period. The average acidic gas concentration and anion concentration in the PM2.5 were, respectively, 4.85±3.08 nmol m-3 for HCl, 22.19±18.47 nmol m-3 for HONO, 9.54±2.52 nmol m-3 for HNO3, 101.57±71.99 nmol m-3 for SO2, 3.78±6.48 nmol m-3 for Cl-, 3.37±1.99 nmol m-3 for NO2-, 25.16±31.49 nmol m-3 for NO3-, and 92.61±55.33 nmol m-3 for SO42-. Characteristic diurnal patterns were observed in several gases. The concentration of HCl fluctuated with changes in the temperature with a 2-hour time-lag. The concentration of HONO peaked in the morning and middle of the night, and its behavior showed a similar pattern of NO2 concentration. Backward trajectory analysis suggested that a high concentration of SO2 that was emitted from China was transported to the sampling site, Tokushima, Japan.

大気中の水溶性酸性ガス及びPM2.5に含まれる陰イオン濃度を高い時間分解能で同時観測可能なオンライン分析システムを構築した．本分析システムは，主に自作のパラレル式ウエットデニューダーと疎水性フィルターを装着したミストチャンバー，及び陰イオン分析用のイオンクロマトグラフ1台で構成され，酸性ガスとPM2.5中陰イオンのデータを1時間にそれぞれ二つずつ出力する．本分析システムを2015年冬季の徳島市の大気分析に適用したところ，観測期間の97.9% で有益なデータを得ることができた．酸性ガス濃度の平均値(n＝844)は，それぞれHCl: 4.85±3.08 nmol m-3，HONO: 22.19±18.47 nmol m-3，HNO3 : 9.54±2.52 nmol m-3，SO2 : 101.57±71.99 nmol m-3であり，SO2が高濃度に存在していた．一方，PM2.5に含まれる陰イオンの平均値(n＝844)は，それぞれCl-: 3.78±6.48 nmol m-3，NO2-: 3.37±1.99 nmol m-3，NO3-: 25.16±31.49 nmol m-3，SO42-: 92.61±55.33 nmol m-3であり，これら陰イオンの総濃度の9割以上をSO42-とNO3-が占めていた．観測期間中の同時刻のデータを平均化して，観測成分の日内変動を調べたところ，いくつかの酸性ガスで特徴的な挙動が明らかとなった．HCl濃度は気温の変動と類似していたが，そこには2時間のタイムラグが存在した．HONO濃度は午前9時頃と深夜0時頃にピークを有する二山型の変動がみられ，その挙動はNO2濃度の変動と類似していた．また，観測データを後方流跡線解析と対応させることにより，中国大陸から排出された高濃度のSO2が徳島に流入している可能性が示唆された．


Cobalt(III) Pretreatment for Total Phosphorus Determination

Abstract: A fast and simple pretreatment method of phosphorus compounds using Co3+ has been studied for the spectrophotometric determination of total phosphorus in water samples. Sample was mixed with a pretreatment solution (0.05 mol dm-3 CoSO4 in 1 mol dm-3 H2SO4) in an electrolytic cell at the volume ratio of 4:1. Highly reactive Co3+ was continuously generated through the electrolysis of Co2+ during the pretreatment. Aliquot of the solution was injected to the system of flow injection - Molybdenum Blue spectrophotometry in order to evaluate phosphate ion (PO43-) produced. Organic phosphorus compounds are completely decomposed to PO43- within 2 min by Co3+ under moderate condition (70°C). The Co3+ is also effective for the acid hydrolysis of polyphosphates; diphosphate and tripolyphosphate are converted to PO43- within 8 min through the pretreatment. Possible mechanisms of the pretreatment are discussed based on the strong oxidizing activity and the Lewis acid nature of Co3+.


Effect of hydroxypropyl cellulosse and hydroxypropyl methylcellulose on carbamazepine polymorphic transformation; attenuated total reflectance-infrared spectroscopy and chemiinformatics analysis


Application of Air Segmented Amplitude Modulated Multiplexed Flow Analysis with Software-Based Phase Recognition to the Determination of Ammonium Ion in Water Samples


Effect of carbon dioxide on self-setting apatite cement formation from tetracalcium phosphate and dicalcium phosphate dihydrate; ATR-IR and chemoinformatics analysis


Nafion Membrane Tube-Based On-Line Concentrator. Application to Urinary Orotic Acid Determined by Suppressed Ion Chromatography

This paper describes the performance of suppressed ion chromatography coupled with a Nafion membrane tube-based on-line concentration technique for the determination of urinary orotic acid, which serves as a biochemical indicator for ornithine transcarbamylase deficiency. After the separation of the analyte by the chromatography, it is concentrated while the eluent flows through the Nafion membrane tube, meanwhile, a nitrogen gas flows outside the tube to remove the solvent. The peak of orotic acid was increased with increasing sample residence time, nitrogen gas flow rate, and concentration temperature. With the concentrator, the detection sensibility was improved, and the lower detection limit was obtained compared to that without the concentrator. The optimized system has successfully been applied to the determination of orotic acid in real urinary samples.


Formaldehyde Content of Atmospheric Aerosol

Formaldehyde (HCHO) is a highly soluble polar molecule with a large sticking coefficient and thus likely exists in both gaseous and particulate forms. Few studies, however, address particulate HCHO (HCHO(p)). Some report that HCHO(p) concentrations (obtained only with long duration sampling) are very low. The lack of data partly reflects the difficulty of specifically measuring HCHO(p). Long duration filter sampling may not produce meaningful results for a variety of reasons. In this work, gaseous HCHO (HCHO(g)) and (HCHO(p)) were, respectively, collected with a parallel plate wet denuder (PPWD) followed by a mist chamber/hydrophilic filter particle collector (PC). The PPWD quantitatively removed HCHO(g) and the PC then collected the transmitted aerosol. The collected HCHO from either device was alternately analyzed by Hantzsch reaction-based continuous flow fluorometry. Each gas and particle phase measurement took 5 min each, with a 10 min cycle. The limits of detection were 0.048 and 0.0033 μg m(-3), respectively, for HCHO(g) and HCHO(p). The instrument was deployed in three separate campaigns in a forest station in western Japan in March, May, and July of 2013. Based on 1296 data pairs, HCHO(p), was on the average, 5% of the total HCHO. Strong diurnal patterns were observed, with the HCHO(p) fraction peaking in the morning. The relative humidity dependence of the partition strongly suggests that it is driven by the liquid water content of the aerosol phase. However, HCHO(p) was 100× greater than that expected from Henry's law. We propose that the low water activity in the highly saline droplets lead to HCHO oligomerization.


Air Segmented-Amplitude Modulated Multiplexed Flow Analysis with Software-Based Phase Recognition. Determination of Phosphate Ion

Amplitude modulated multiplexed flow analysis (AMMFA) has been improved by introducing air segmentation and software-based phase recognition. Sample solutions, the flow rates of which are respectively varied at different frequencies, are merged. Air is introduced to the merged liquid stream in order to limit the dispersion of analytes within each liquid segment separated by air bubbles. The stream is led to a detector with no physical deaeration. Air signals are distinguished from liquid signals through the analysis of detector output signals, and are suppressed down to the level of liquid signals. Resulting signals are smoothed based on moving average computation. Thus processed signals are analyzed by fast Fourier transform. The analytes in the samples are respectively determined from the amplitudes of the corresponding wave components obtained. The developed system has been applied to the simultaneous determinations of phosphate ions in water samples by a Malachite Green method. The linearity of the analytical curve (0.0-31.0 mol dm(-3)) is good (r(2)>0.999) and the detection limit (3.3 ) at the modulation period of 30s is 0.52 mol dm(-3). Good recoveries around 100% have been obtained for phosphate ions spiked into real water samples.


Atmospheric Acid Gases in Tokushima, Japan, Monitored with Parallel Plate Wet Denuder Coupled Ion Chromatograph

During the summer of 2011 and winter of 2012, we continuously measured trace acid gas concentrations in Tokushima, Japan, using a parallel plate wet denuder coupled ion chromatograph. The average concentrations of hydrochloric acid (HCl), nitrous acid (HONO), nitric acid (HNO(3)), and sulfur dioxide (SO(2)) were, respectively, 0.54, 1.20, 1.17, and 3.22 g m(-3) in the summer, and 0.09, 1.06, 0.46, and 5.11 g m(-3) in the winter. In the summer, concentrations of all the acid gases increased after sunrise and showed a strong diurnal pattern with daytime maxima and nighttime minima, but the time at which concentration levels began to increase and the pace of increase differed among the acid gases. The concentration of HONO increased sharply immediately after sunrise, while concentrations of the other three gases began increasing about one and half hours later. SO(2) showed the fastest rate of increase, followed by HNO(3) and HCl. These differences were likely attributable to the formation processes of gaseous substances.


Surface Modified Annular Wet Denuder for the Collection of Water-Soluble Trace Gases


On-Line Measurement of Perchlorate in Atmospheric Aerosol Based on Ion Chromatograph Coupled with Particle Collector and Post-Column Concentrator

An automated analysis system has been developed for measuring perchlorate concentration in atmospheric aerosol. The perchlorate in aerosol sample, which has been collected with water mist in a hydrophobic filter/mist chamber based particle collector, is continuously preconcentrated. The matrix ions such as sulfate are subsequently removed from the preconcentrator. The remaining perchlorate is then analyzed on-line with an ion chromatograph in conjunction with a Nafion membrane tube based post-column concentrator. The sensitivity is increased by a factor of 7.7 with the post-column concentration technique. The proposed system has been successfully operated at Tokushima, Japan. The limit of detection is 0.35 ng/m(3) for 3 h sampling cycle. The perchlorate concentration in the atmospheric aerosol averaged 1.01±1.75 ng/m(3) (n=12).


Simultaneous Determination of Nitrite and Nitrate Ions by Air-Segmented Amplitude-Modulated Multiplexed Flow Analysis

The concept of amplitude-modulated multiplexed flow analysis has been extended to the simultaneous determination of multiple analytes in a sample. A sample solution containing nitrite and nitrate ions is delivered from two channels, but the flow rates are varied at different frequencies. One of the channels has a reduction column for converting nitrate ions to nitrite ions. Downstream, the absorbance of the diazo-coupling product is monitored after the merging of both solutions with a Griess reagent. The signal is analyzed by a fast Fourier transform (FFT) in real time. From the thus-obtained amplitude, a µmol dm(-3) level of the ions can be determined. The introduction of air bubbles is effective to reduce any axial dispersion, and hence to improve the sensitivity.


Parallel-Plate Wet Denuder Coupled Ion Chromatograph for Near-Real-Time Detection of Trace Acidic Gases in Clean Room Air

This paper describes the performance of our automated acidic (CH(3)COOH, HCOOH, HCl, HNO(2), SO(2), and HNO(3)) gases monitor utilizing a parallel-plate wet denuder (PPWD). The PPWD quantitatively collects gaseous contaminants at a high sample flow rate (8 dm(3) min(-1)) compared to the conventional methods used in a clean room. Rapid response to any variability in the sample concentration enables near-real-time monitoring. In the developed monitor, the analyte collected with the PPWD is pumped into one of two preconcentration columns for 15 min, and determined by means of ion chromatography. While one preconcentration column is used for chromatographic separation, the other is used for loading the sample solution. The system allows continuous monitoring of the common acidic gases in an advanced semiconductor manufacturing clean room.


Air-Segmented Amplitude-Modulated multiplexed Flow Analysis

Air-segmentation is applied to amplitude-modulated multiplexed flow analysis, which we proposed recently. Sample solutions, the flow rates of which are varied periodically, are merged with reagent and/or diluent solution. The merged stream is segmented by air-bubbles and, downstream, its absorbance is measured after deaeration. The analytes in the samples are quantified from the amplitudes of the respective wave components in the absorbance. The proposed method is applied to the determinations of a food dye, phosphate ions and nitrite ions. The air-segmentation is effective for limiting amplitude damping through the axial dispersion, resulting in an improvement in sensitivity. This effect is more pronounced at shorter control periods and longer flow path lengths.


Spectrophotometric Determination of Trace Phosphate Ion by Amplitude Modulated Flow Analysis Coupled with Malachite Green Method

An amplitude-modulated flow analysis coupled with lock-in detection is proposed for the determination of trace phosphate. The flow rate F(S) of sample solution is varied in response to a periodic signal V(c) of alternating waveform. A coloring reagent solution (ammonium molybdate + Malachite Green) is delivered at a constant flow rate F(R). Under the constant total flow rate F(T), both solutions are merged with a diluent (water). Phosphate ion in the sample reacts with molybdate and then with Malachite Green to form green ion pairs in acidic media. Downstream, the absorbance of the mixed solution is measured at 625 nm. The output voltage V(d) from the detector is sent to a lock-in amplifier, where the wave component of V(d) that has the same frequency as that of V(c) is distinguished from background signals. Phosphate ion can be determined from the amplitude of the component thus extracted. The calibration curve is linear (r(2) > 0.998) and the limit of detection (3.3sigma) is 0.17 micromol dm(-3). Compared with a conventional flow-based method with no modulation, the present method is less susceptible to the baseline drift due mainly to the adsorption of the ion-pair on the optical window, because the quantification is based not on the absorbance itself but on the amplitude of the absorbance. Good recoveries around 100% are obtained for the phosphate ions spiked into real water samples.


Analytical Parameters for Amplitude Modulated Multiplexed Flow Analysis

Analytical conditions of amplitude-modulated multiplexed flow analysis, the basic concept of which was recently proposed by our group, are investigated for higher sample throughput rate. The performance of the improved system is evaluated by applying it to the determination of chloride ions. The flow rates of two sample solutions are independently varied in accordance with sinusoidal voltage signals, each having different frequency. The solutions are merged with a reagent solution and/or a diluent, while the total flow rate is held constant. Downstream, the analytical signal V(d) is monitored with a spectrophotometer. The V(d) shows a complicated profile resulting from amplitude modulated and multiplexed information on the two samples. The V(d) can, however, be deconvoluted to the contribution of each sample through fast Fourier transform (FFT). The amplitudes of the separated wave components are closely related to the concentrations of the analytes in the samples. By moving the window for FFT analysis with time, a temporal profile of the amplitudes can be obtained in real-time. Analytical conditions such as modulation period and system configuration have been optimized using aqueous solutions of Malachite Green (MG). Adequate amplitudes are obtained at the period of as low as 5 s. At this period, the calibration curve for the MG concentration of 0-30 micromol dm(-3) has enough linearity (r(2) = 0.999) and the limit of detection (3.3sigma) is 1.3 micromol dm(-3); the relative standard deviation of repeated measurements (C(MG) = 15 micromol dm(-3), n = 10) is 2.4%. The developed system has been applied to the determination of chloride ions by a mercury(II) thiocyanate method. The system can adequately follow the changes in analyte concentration. The recoveries of chloride ion spiked in real water samples (river and tap water) are satisfactory, around 100%.


Atmospheric Methanethiol Emitted from a Pulp and Paper Plant on the Shore of Lake Baikal.


Dynamics of Sulfur-Containing Admixtures in the Atmosphere around the Point Source the Baikal Pulp and Paper Plant (South-East of Baikal Lake).


Spectrophotometric Determination of Anionic Sufactant Based on Ion-pair Formation with Methylene Blue in Riversed Flow Injection Mode


Application of Feedback-Based Flow Ratiometry to Simultaneous Determination of Calcium and Magnesium Ions by Chelatometry Using Photometric and Potentiometric Detectors


Use of a Capacitance Measurement Device for Surrogate Noncontact Conductance Measurement

A capacitance to digital converter (AD7746) is used in the same mode as noncontact conductance detectors. The detector output is linearly proportional to specific conductance (sigma) at low sigma values but becomes nonlinear and reaches a plateau value at sigma approximately >0.75 mS/cm, regardless of the nature of the electrolyte. For all applications at sub- to low-mM concentrations, the device, available as an evaluation board, provides a very affordable nothing-else-required means of contactless surrogate conductivity detection from capillary scale to larger bore conduits. For the same measurement cell volume, the detector provides virtually the same limits of detection (LODs) as a standard galvanic contact conductivity detector in conventional scale suppressed conductometric ion chromatography. The detection limits deteriorate as the conduit inner diameter decreases.


On-Line Gas-Free Electrodialytic Eluent Generator for Capillary Ion Chromatography.

Both low- and high-pressure, gas-free, capillary-scale electrodialytic generators for eluents in ion chromatography are described. While the low-pressure devices rely on planar or tubular membranes, the high-pressure devices rely on ion-exchange beads used both as one-way ionic gates and as ball-on-seat valves to provide sealing. The high-pressure device is easily implemented in the form of a commercial cross fitting and can withstand at least 1400 psi. By design these devices do not produce gas in the eluent channel; hence, it is not necessary to remove gas afterward. With appropriate electrolytes and electrode polarities, such devices can produce either acid or base or salt. In regard to ionic transport, the behavior of these devices fully corresponds to that of a semiconductor diode. To our knowledge, this is the first time such complete equivalence of ion transport through ion-exchange media and with the more familiar example of electron transport through a semiconductor diode under both forward- and reverse-biased conditions have been demonstrated. Reverse bias can be applied to minimize/prevent Donnan-forbidden leakage or ion exchange. Even with 4 M KOH in the electrode compartments and 4 microL/min water flowing through the eluent channel, with a reverse bias of -12 V, the leakage KOH concentration is <30 microM, whereas the KOH concentration with zero voltage applied, herein after termed open circuit penetration (OCP), is 1600 microM. It is suggested that this OCP occurs not as much through Donnan-forbidden leakage but via ion exchange. Chromatograms and reproducibility data are presented for both isocratic and gradient chromatography, using ion-exchange, latex-modified, open tubular and packed monolithic columns.


Amplitude Modulated multiplexed flow analysis


Postcolumn Concentration in Liquid Chromatography. On-Line Eluent Evaporation and Analyte Postconcentration in Ion Chromatography

On-line sample concentration by evaporation through a narrow-bore membrane tube is described. The device can be deployed just prior to the detector or the sample may be concentrated prior to injection. As solution flows through a solvent-permeable membrane tube, (heated) drying gas (nitrogen/air) flows outside it to remove the solvent. The removal rate increases with increasing sample residence time, drying gas flow rate, and temperature. Various membranes and three concentrator designs (a rectangular maze, a serpentine and a filament-filled helix, the last performing the best) were fabricated and tested for post- and preseparation applications in suppressed anion chromatography. An order of magnitude concentration factors are readily obtained. The present system involves active mass transport radially outward through the walls of a tube. This is a system in which many of the traditional paradigms of flow through a tubular conduit no longer hold true. Because the flow rate continuously varies along the tube, residence time does not scale linearly with residence volume or conduit length. The effects of such mass transport on the parabolic velocity profile of laminar flow remain unknown.


Tailoring elution of tetraalkylammonium ions. Ideal electrostatic selectivity elution order on a polymeric ion exchanger

Although ion exchange is often depicted as a process driven by electrostatic forces, ionic solvation or hydrophobic forces contribute greatly to ion exchange selectivity and is often the dominant factor. On a variety of commercial anion exchange columns, monovalent ClO4- elutes after doubly charged SO42- and even triply charged PO43-. For identically charged alkali metal ions, electrostatic charge densities based on crystal radii would suggest Li+ to be the most strongly retained on a cation exchanger. In practice, it is typically the least strongly held cation on most cation exchangers, because of its very high hydration energy and with most eluents its capacity factor approaches zero. Even when the ion is very poorly solvated, as with tetraalkylammonium (NR4+) cations, there has never been a report on a polymeric ion exchanger of an ideal electrostatic selectivity order where NR4+ cations elute in their increasing charge density order: R = n-butyl first, followed by n-propyl, ethyl, and last, methyl. We show that this selectivity order is easily achieved on recently described methracrylate-based monolithic capillary cation exchange columns (Ueki, Y.; Umemura, T.; Li, J. X.; Odake, T; Tsunoda, K. Anal. Chem. 2004, 76, 7007-7012) with minor amounts of hydroorganic modifiers. Indeed, under such conditions, Li+ (and other alkali cations) elutes after NMe4+.


Versatile gas/particle ion chromatograph

A new, compact gas/particle ion chromatograph has been developed for measuring ionic constituents in PM2.5 (particulate matter of aerodynamic diameter < or = 2.5 microm) and water-soluble ionogenic gases. The instrument has separate sampling channels for gases and particles. In one, a membrane denuder collects soluble gases for preconcentration and analysis. In the other, a cyclone removes larger particles, a membrane denuder removes soluble gases, and a continuously wetted hydrophilic filter collects particles. A single, multiport, syringe pump handles liquid transport, and one conductivity detector measures anions and ammonium for both channels. Electrodialytically generated gradient hydroxide eluent permits 20 min chromatographic runs. Gas/particle samples are each collected for 40 min, butthe sampling intervals are staggered by 20 min. Liquid samples from the gas denuder and particle collector are aspirated and preconcentrated on sequential cation and anion concentrators and transferred respectively to an ammonia transfer device and an anion separation column. The flow configuration results in an ammonium peak before anion peaks in the chromatogram. The system measures ammonia, organic acids (such as acetic, formic, and oxalic acids), HCl, HONO, SO2, HNO3, and the corresponding ions in the aerosol phase. Low ng/m3 to sub-ng/m3 limits of detection (LODs) are attained for most common gases and particulate constituents, the LODs for gaseous SO2 to NH3 range, for example, from sub parts per trillion by volume (sub-pptv) to approximately 5 pptv.


Continuous collection of soluble atmospheric particles with a wetted hydrophilic filter

Approximately one-third of the area (14-mm diameter of a 25-mm diameter) of a 5-microm uniform pore size polycarbonate filter is continuously wetted by a 0.25 mL/min water mist. The water forms a continuous thin film on the filter and percolates through it. The flowing water substantially reduces the effective pore size of the filter. At the operational air sampling flow rate of 1.5 standard liters per minute, such a particle collector (PC) efficiently captures particles down to very small size. As determined by fluorescein-tagged NaCl aerosol generated by a vibrating orifice aerosol generator, the capture efficiency was 97.7+% for particle aerodynamic diameters ranging from 0.28 to 3.88 microm. Further, 55.3 and 80.3% of 25- and 100-nm (NH4)2SO4 particles generated by size classification with a differential mobility analyzer were respectively collected by the device. The PC is integrally coupled with a liquid collection reservoir. The liquid effluent from the wetted filter collector, bearing the soluble components of the aerosol, can be continuously collected or periodically withdrawn. The latter strategy permits the use of a robust syringe pump for the purpose. Coupled with a PM2.5 cyclone inlet and a membrane-based parallel plate denuder at the front end and an ion chromatograph at the back end, the PC readily operated for at least 4-week periods without filter replacement or any other maintenance.


Characteristics of water-soluble components of atmospheric aerosols in Yokohama and Mt. Oyama, Japan from 1990 to 2001


Membrane based parallel plate denuder for the collection and removal of soluble atmospheric gases

A continuously wetted cellulose acetate membrane-based parallel plate diffusion denuder is described. This is the first membrane-based denuder that has a small enough internal liquid holdup volume to permit reasonably rapid response time (10 --> 90% rise time of approximately 1.2 min for a transient event at a liquid flow rate of 500 microL/min) while permitting quantitative removal of common soluble atmospheric trace gases at flow rates up to 1.7 L/min. The latter attribute permits the use of the device as the first element in a particle sampling and analysis system for the quantitative removal of potentially interfering soluble trace gases. Particle losses in the denuder range from 0.9 to 2.9% over an aerodynamic diameter range of 0.38-3.48 microm, averaging 1.8%. However, only approximately 0.5% of the particles actually appears in the denuder effluent liquid. The relatively compact (300 mm H x 57 mm W x 26 mm D) wet denuder should be attractive in a number of applications. We show excellent agreement for HONO measurements with a conventional larger parallel plate wetted denuder in field measurements.


Deposition of coarse soil particles and ambient gaseous components dominating dew water chemistry

Journal of Geophysical Research: Atmospheres


Size distribution of dew droplets and dew formation effect on deposition fluxes

Bulletin of the Chemical Society of Japan


Controlling factors of weak acid and base concentrations in urban dewwater -comparison of dew chemistry with rain and fog chemistry-


Dominant factors of major and minor components and formation of hydroxyalkanesulfonate in urban dew-water


A study on chemical components and acidification mechanism of dew-water

露水の化学組成とその酸性化機構に関する研究

Journal of Japan Society Atmospheric Environment