G. H. Sarpara, Sijung Hu, James N. Miller, D. A. Palmer, M. T. French, M. Evans
Naphthofluorescein diphosphate has been synthesised from the parent dye, and shown to be an attractive long-wavelength alternative to other fluorigenic substrates for the determination of alkaline phosphatase. Its application to the determination of theophylline, an inhibitor of this enzyme, has been demonstrated. The optimum excitation wavelength of the hydrolysis product naphthofluorescein has been found to depend on the presence of additives such as cyclodextrins and (3-[3-cholamidopropyl]-dimethylamino)-1-propane sulfonate (CHAPS): such effects can be used to raise the excitation wavelength to match the output of a 635 nm diode laser in a simple and sensitive fluorescence detector.
{"title":"A new long-wavelength fluorigenic substrate for alkaline phosphatase: synthesis and characterisation","authors":"G. H. Sarpara, Sijung Hu, James N. Miller, D. A. Palmer, M. T. French, M. Evans","doi":"10.1039/A809018A","DOIUrl":"https://doi.org/10.1039/A809018A","url":null,"abstract":"Naphthofluorescein diphosphate has been synthesised from the parent dye, and shown to be an attractive long-wavelength alternative to other fluorigenic substrates for the determination of alkaline phosphatase. Its application to the determination of theophylline, an inhibitor of this enzyme, has been demonstrated. The optimum excitation wavelength of the hydrolysis product naphthofluorescein has been found to depend on the presence of additives such as cyclodextrins and (3-[3-cholamidopropyl]-dimethylamino)-1-propane sulfonate (CHAPS): such effects can be used to raise the excitation wavelength to match the output of a 635 nm diode laser in a simple and sensitive fluorescence detector.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"15 1","pages":"19-20"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90282699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Gooding, M. Situmorang, P. Erokhin, D. B. Hibbert
This paper presents a simple assay for the estimation of the amount of glucose oxidase immobilised onto the surface of enzyme electrodes. The two flavin adenine dinucleotide (FAD) cofactors were stripped from immobilised glucose oxidase using an 8 M urea solution. The resultant concentration of FAD in the urea solution was quantified using either fluorescence or voltammetry to determine the amount of glucose oxidase on the electrode surface. The assay is applied to a variety of different enzyme electrodes and is verified for a monolayer enzyme electrode using a quartz crystal microbalance.
{"title":"An assay for the determination of the amount of glucose oxidase immobilised in an enzyme electrode","authors":"J. Gooding, M. Situmorang, P. Erokhin, D. B. Hibbert","doi":"10.1039/A902718A","DOIUrl":"https://doi.org/10.1039/A902718A","url":null,"abstract":"This paper presents a simple assay for the estimation of the amount of glucose oxidase immobilised onto the surface of enzyme electrodes. The two flavin adenine dinucleotide (FAD) cofactors were stripped from immobilised glucose oxidase using an 8 M urea solution. The resultant concentration of FAD in the urea solution was quantified using either fluorescence or voltammetry to determine the amount of glucose oxidase on the electrode surface. The assay is applied to a variety of different enzyme electrodes and is verified for a monolayer enzyme electrode using a quartz crystal microbalance.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"163 1","pages":"225-228"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83338412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A computer simulation of active adsorbent sampling was used to investigate the possibility of effecting desorption of volatile organic compounds from an adsorbent trap both rapidly and efficiently via competitive adsorption with a concentrated solvent vapour. The simulation was then enacted in an experimental system to test the concept which used ion mobility spectrometry to follow the desorption of trapped pentan-2-one from a Tenax adsorbent bed, that was subjected to cold vapour desorption. The ion mobility spectra obtained indicated that pentan-2-one was rapidly released from the adsorbent trap with an accompanying enrichment of at least 600%. Desorption by the solvent vapour was shown to have an efficiency of greater than 99.8% in comparison to a thermal desorption method.
{"title":"Cold vapour desorption of volatile organic compounds from an adsorbent trap","authors":"M. Huxham, C. L. Thomas","doi":"10.1039/A904353E","DOIUrl":"https://doi.org/10.1039/A904353E","url":null,"abstract":"A computer simulation of active adsorbent sampling was used to investigate the possibility of effecting desorption of volatile organic compounds from an adsorbent trap both rapidly and efficiently via competitive adsorption with a concentrated solvent vapour. The simulation was then enacted in an experimental system to test the concept which used ion mobility spectrometry to follow the desorption of trapped pentan-2-one from a Tenax adsorbent bed, that was subjected to cold vapour desorption. The ion mobility spectra obtained indicated that pentan-2-one was rapidly released from the adsorbent trap with an accompanying enrichment of at least 600%. Desorption by the solvent vapour was shown to have an efficiency of greater than 99.8% in comparison to a thermal desorption method.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"26 1","pages":"317-320"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76857958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Takuya Okamoto, Ken-ichiro Tanaka, H. Goto, Jin‐Ming Lin, M. Yamada, Y. Asano
An indicator phase, luminol immobilized on a strongly basic anion-exchange resin, was evaluated for the chemiluminescence sensing of O2 in N2 gas. The base catalyzed luminol chemiluminescence was monitored with a silicon photodiode installed in a flow cell, into which the luminol-loaded resin was packed. The signal was dependent significantly on resins and solvents used for the immobilization. Oxygen gas concentrations at ppm levels in a N2 gas and a city gas were determined by means of 1 ml sample injection.
{"title":"Luminol immobilized anion-exchange resin as an indicator phase for a chemiluminescence oxygen gas sensor","authors":"Takuya Okamoto, Ken-ichiro Tanaka, H. Goto, Jin‐Ming Lin, M. Yamada, Y. Asano","doi":"10.1039/A901414D","DOIUrl":"https://doi.org/10.1039/A901414D","url":null,"abstract":"An indicator phase, luminol immobilized on a strongly basic anion-exchange resin, was evaluated for the chemiluminescence sensing of O2 in N2 gas. The base catalyzed luminol chemiluminescence was monitored with a silicon photodiode installed in a flow cell, into which the luminol-loaded resin was packed. The signal was dependent significantly on resins and solvents used for the immobilization. Oxygen gas concentrations at ppm levels in a N2 gas and a city gas were determined by means of 1 ml sample injection.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"14 1","pages":"181-183"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75594115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Determination of iodine in glacial acetic acid is a major concern of acetic acid manufacturers and consumers. The use of ICP-MS for iodine determinations in acetic acid is hindered by memory effects that produce an elevated background signal necessitating long rinse times between samples. In this work, different analysis methods are employed in an attempt to minimize memory and matrix effects allowing for the accurate determination of iodine in glacial acetic acid using ICP-MS. Ammonium hydroxide solutions (3.7 and 7.4 M) were better at reducing the elevated iodine signal present after the introduction of an acetic acid sample than water or 0.3 M nitric acid. Memory effects were decreased when the sample was introduced by flow injection rather than constant sample aspiration. Peak areas generated by flow injection decreased significantly with increasing ammonium hydroxide concentration in the carrier solution. Iodine determinations made with 1.7 M ammonium hydroxide as the carrier solution were higher than determinations made with 3.7 M ammonium hydroxide as the carrier solution for the same samples, however, the percentage difference between the two determinations varied widely from sample to sample. All samples were analyzed by the method of standard additions in an attempt to compensate for matrix effects. This work illustrates the importance of the carrier solution in the determination of iodine in glacial acetic acid samples.Introduction
{"title":"Investigation of problems associated with the determination of iodine in glacial acetic acid samples using flow injection analysis-inductively coupled plasma-mass spectrometry†","authors":"K. L. Ackley, J. Day, K. Sutton, J. Caruso","doi":"10.1039/A904296B","DOIUrl":"https://doi.org/10.1039/A904296B","url":null,"abstract":"Determination of iodine in glacial acetic acid is a major concern of acetic acid manufacturers and consumers. The use of ICP-MS for iodine determinations in acetic acid is hindered by memory effects that produce an elevated background signal necessitating long rinse times between samples. In this work, different analysis methods are employed in an attempt to minimize memory and matrix effects allowing for the accurate determination of iodine in glacial acetic acid using ICP-MS. Ammonium hydroxide solutions (3.7 and 7.4 M) were better at reducing the elevated iodine signal present after the introduction of an acetic acid sample than water or 0.3 M nitric acid. Memory effects were decreased when the sample was introduced by flow injection rather than constant sample aspiration. Peak areas generated by flow injection decreased significantly with increasing ammonium hydroxide concentration in the carrier solution. Iodine determinations made with 1.7 M ammonium hydroxide as the carrier solution were higher than determinations made with 3.7 M ammonium hydroxide as the carrier solution for the same samples, however, the percentage difference between the two determinations varied widely from sample to sample. All samples were analyzed by the method of standard additions in an attempt to compensate for matrix effects. This work illustrates the importance of the carrier solution in the determination of iodine in glacial acetic acid samples.Introduction","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"50 2 1","pages":"295-298"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83401375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The separation of inorganic cations using a phosphocholine-type zwitterionic stationary phase [formed by coating an octadecyl silica column with a phosphocholine zwitterionic surfactant (PC-ZS)] and water as the mobile phase has been investigated. The PC-ZS possesses a positively charged group (+) and a negatively charged group (–), with the (+) being outermost and the (–) being innermost. In other words, the positions of the functional groups are opposite to that for sulfobetaine-type zwitterionic surfactants (SB-ZS) used previously for the separation of inorganic anions. With a PC-ZS stationary phase, cations having the same charges (e.g., Mg2+, Ca2+, Ba2+) were separated successfully. This study shows that the separation selectivity of zwitterionic stationary phases towards inorganic anions or cations is determined chiefly by the positions of the two charged groups on the zwitterion. The elution order for the cations (for example Ba2+
{"title":"Electrostatic ion chromatography of cations using an N -dodecylphosphocholine zwitterionic stationary phase and water as the mobile phase","authors":"Wenzhi Hu, P. Haddad, K. Hasebe, Kazuhiko Tanaka","doi":"10.1039/A809312A","DOIUrl":"https://doi.org/10.1039/A809312A","url":null,"abstract":"The separation of inorganic cations using a phosphocholine-type zwitterionic stationary phase [formed by coating an octadecyl silica column with a phosphocholine zwitterionic surfactant (PC-ZS)] and water as the mobile phase has been investigated. The PC-ZS possesses a positively charged group (+) and a negatively charged group (–), with the (+) being outermost and the (–) being innermost. In other words, the positions of the functional groups are opposite to that for sulfobetaine-type zwitterionic surfactants (SB-ZS) used previously for the separation of inorganic anions. With a PC-ZS stationary phase, cations having the same charges (e.g., Mg2+, Ca2+, Ba2+) were separated successfully. This study shows that the separation selectivity of zwitterionic stationary phases towards inorganic anions or cations is determined chiefly by the positions of the two charged groups on the zwitterion. The elution order for the cations (for example Ba2+<Mg2+<Ca2+) differed from that of cation-exchange, demonstrating that the zwitterionic stationary phase interacts with analyte ions in a unique manner. A retention mechanism based on coulombic attraction and repulsion effects and ion-pair formation is proposed.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"16 1","pages":"97-100"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87069418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A bacteria-modified carbon paste electrode has been prepared and used for the very sensitive and selective determination of trace amounts of gold(III). The modified electrode was able to detect a solution of 1.0 ppb Au(III) by applying cathodic stripping voltammetry. Advantages of the bacteria-modified electrode include high sensitivity, good stability, low cost and simple preparation. It could be a new class of modified electrode with practical value.
{"title":"Determination of trace amounts of gold(III) by cathodic stripping voltammetry using a bacteria-modified carbon paste electrode","authors":"R. Hu, Weide Zhang, Jinkun Fu, Y. Liu","doi":"10.1039/A900600A","DOIUrl":"https://doi.org/10.1039/A900600A","url":null,"abstract":"A bacteria-modified carbon paste electrode has been prepared and used for the very sensitive and selective determination of trace amounts of gold(III). The modified electrode was able to detect a solution of 1.0 ppb Au(III) by applying cathodic stripping voltammetry. Advantages of the bacteria-modified electrode include high sensitivity, good stability, low cost and simple preparation. It could be a new class of modified electrode with practical value.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"2616 1","pages":"147-148"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86166106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Alkasrawi, I. Popescu, B. Mattiasson, E. Csöregi, V. Laurinavicius
The present work describes the design and characteristics of a glucose electrode based on a newly isolated and purified, oxygen-independent, pyrrole quinoline quinone glucose dehydrogenase (PQQ–GDH) integrated in a redox hydrogel (poly(1-vinylimidazole) complexed with Os(4-4′-dimethylbipyridine)2Cl) using poly(ethylene glycol)diglycidyl ether (PEGDGE) as a crosslinker. The influence of the buffer’s nature and the presence of PQQ and Ca2+ ions on the enzyme stability were considered. The characteristics of the optimal electrode design were compared to those obtained for similarly prepared, glucose oxidase based electrodes. The optimal electrode configuration inserted in a single manifold flow injection system, was characterised by a linear range up to 100 µM, a sensitivity of 5.9 mA M–1 cm–2, and a detection limit of 5 µM (calculated as three times the signal-to-noise ratio).
本工作描述了一种以聚乙二醇二甘油酯醚(PEGDGE)为交联剂，将新分离纯化的氧不依赖的吡咯喹啉醌葡萄糖脱氢酶(PQQ-GDH)整合在氧化还原水凝胶(聚(1-乙烯基咪唑)与Os(4-4′-二甲基联吡啶)2Cl络合)中的葡萄糖电极的设计和特性。考虑了缓冲液性质、PQQ和Ca2+离子的存在对酶稳定性的影响。将最佳电极设计的特征与类似制备的葡萄糖氧化酶电极的特征进行了比较。最佳电极配置插入到单流形注射系统中，其特点是线性范围高达100µM，灵敏度为5.9 mA M - 1 cm-2，检测限为5µM(计算为信噪比的三倍)。
{"title":"A redox hydrogel integrated PQQ–glucose dehydrogenase based glucose electrode","authors":"M. Alkasrawi, I. Popescu, B. Mattiasson, E. Csöregi, V. Laurinavicius","doi":"10.1039/A907188A","DOIUrl":"https://doi.org/10.1039/A907188A","url":null,"abstract":"The present work describes the design and characteristics of a glucose electrode based on a newly isolated and purified, oxygen-independent, pyrrole quinoline quinone glucose dehydrogenase (PQQ–GDH) integrated in a redox hydrogel (poly(1-vinylimidazole) complexed with Os(4-4′-dimethylbipyridine)2Cl) using poly(ethylene glycol)diglycidyl ether (PEGDGE) as a crosslinker. The influence of the buffer’s nature and the presence of PQQ and Ca2+ ions on the enzyme stability were considered. The characteristics of the optimal electrode design were compared to those obtained for similarly prepared, glucose oxidase based electrodes. The optimal electrode configuration inserted in a single manifold flow injection system, was characterised by a linear range up to 100 µM, a sensitivity of 5.9 mA M–1 cm–2, and a detection limit of 5 µM (calculated as three times the signal-to-noise ratio).","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"230 1","pages":"395-398"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89645298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An electrochemical method for the direct detection of aluminium using single-use sensors is described. The sensor consists of three electrodes (working, auxilliary and pseudo-reference) screen-printed with carbon ink. Aluminium is accumulated at the carbon electrode at –1.6 V (vs. pseudo-reference) in zinc sulfate electrolyte for 90 s prior to anodic stripping using differential-pulse voltammetry. Linear calibrations were obtained between 10 and 450 ppb using the aluminium oxidation peak. The limit of detection was 8 ppb Al3+.
{"title":"Electrochemical detection of aluminium using single-use sensors","authors":"J. Dilleen, B. Birch, B. Haggett","doi":"10.1039/A907667K","DOIUrl":"https://doi.org/10.1039/A907667K","url":null,"abstract":"An electrochemical method for the direct detection of aluminium using single-use sensors is described. The sensor consists of three electrodes (working, auxilliary and pseudo-reference) screen-printed with carbon ink. Aluminium is accumulated at the carbon electrode at –1.6 V (vs. pseudo-reference) in zinc sulfate electrolyte for 90 s prior to anodic stripping using differential-pulse voltammetry. Linear calibrations were obtained between 10 and 450 ppb using the aluminium oxidation peak. The limit of detection was 8 ppb Al3+.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"268 1","pages":"363-365"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73253388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method for investigating the possibility of bias between sampling methods has been devised. It is effected by collecting paired samples from a number of different sampling targets. Paired samples are created by executing a standard sampling protocol and a sampling method under validation in a randomised fashion at each target. After chemical analysis of the two samples, the difference between a pair of results is an estimate of the bias for that target. Repeating the procedure for many distinct targets improves the precision of the estimate. If the analyte concentration range of the targets is small, the mean of the difference estimates is taken as the overall bias estimate. The mean bias can be tested for significance, if required, by a one-sample test. If the concentration range is wide, potential biases can be considered as functions of analyte concentration. Weighted functional relationship estimation is appropriate for this purpose.
{"title":"Estimating sampling bias by using paired samples","authors":"M. Thompson, D. Patel","doi":"10.1039/A902074H","DOIUrl":"https://doi.org/10.1039/A902074H","url":null,"abstract":"A method for investigating the possibility of bias between sampling methods has been devised. It is effected by collecting paired samples from a number of different sampling targets. Paired samples are created by executing a standard sampling protocol and a sampling method under validation in a randomised fashion at each target. After chemical analysis of the two samples, the difference between a pair of results is an estimate of the bias for that target. Repeating the procedure for many distinct targets improves the precision of the estimate. If the analyte concentration range of the targets is small, the mean of the difference estimates is taken as the overall bias estimate. The mean bias can be tested for significance, if required, by a one-sample test. If the concentration range is wide, potential biases can be considered as functions of analyte concentration. Weighted functional relationship estimation is appropriate for this purpose.","PeriodicalId":7814,"journal":{"name":"Analytical Communications","volume":"39 1","pages":"247-248"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74221674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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