Topic
Buffer solution
About: Buffer solution is a research topic. Over the lifetime, 6948 publications have been published within this topic receiving 112440 citations. The topic is also known as: pH buffer & buffer.
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TL;DR: In this article, a glassy carbon electrode covalently modified with penicillamine was used for the simultaneous determination of hydroquinone (HQ) and catechol (CC).
Abstract: A simple and highly selective electrochemical method has been developed for the simultaneous determination of hydroquinone (HQ) and catechol (CC) at a glassy carbon electrode covalently modified with penicillamine (Pen). The electrode is used for the simultaneous electrochemical determination of HQ and CC and shows an excellent electrocatalytical effect on the oxidation of HQ and CC upon cyclic voltammetry in acetate buffer solution of pH 5.0. In differential pulse voltammetric measurements, the modified electrode was able to separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 103 mV although the bare electrode gave a single broad response. The determination limit of HQ in the presence of 0.1 mmol L−1 CC was 1.0 × 10−6 mol L−1, and the determination limit of CC in the presence of 0.1 mmol L−1 HQ was 6.0 × 10−7 mol L−1. The method was applied to the simultaneous determination of HQ and CC in a water sample. It is simple and highly selective.
60 citations
TL;DR: In this paper, the authors investigated the conductivity of single-stranded and doublestranded herring deoxyribose nucleic acid (DNA) in buffer solution spotted and dried on Au nanocontacts.
Abstract: We investigate the conductivity of single-stranded and double-stranded herring deoxyribose nucleic acid (DNA) in buffer solution spotted and dried on Au nanocontacts. We find an exponential increase of the conductivity with increasing humidity that is identical for single- and double-stranded DNA within the measurement accuracy. While the small conductivity of dry DNA is comparable to that of a large band-gap semiconductor, we attribute the increase at high humidity levels to water molecules accumulated at the phosphate backbone. For high humidities we observe s-shaped current-voltage characteristics that can be well explained by the dissociation of water attached to the DNA molecules.
60 citations
TL;DR: Results suggest that lowered pH exerts its negative effect on NDF digestion between pH 6.2 and 5.8, as evidenced by increased lag and decreased rate, and that critical pH and specific, affected component of digestion varied among forages.
60 citations
TL;DR: It is proposed that at high ionic strength the enzyme is immobilised via the dimerisation domain to the SAM surface, thereby promoting the sequential intramolecular and heterogeneous electron transfer from Moco via Cyt b5 to the electrode.
Abstract: Human sulfite oxidase (hSO) was immobilised on SAM-coated silver electrodes under preservation of the native heme pocket structure of the cytochrome b5 (Cyt b5) domain and the functionality of the enzyme. The redox properties and catalytic activity of the entire enzyme were studied by surface enhanced resonance Raman (SERR) spectroscopy and cyclic voltammetry (CV) and compared to the isolated heme domain when possible. It is shown that heterogeneous electron transfer and catalytic activity of hSO sensitively depend on the local environment of the enzyme. Increasing the ionic strength of the buffer solution leads to an increase of the heterogeneous electron transfer rate from 17 s−1 to 440 s−1 for hSO as determined by SERR spectroscopy. CV measurements demonstrate an increase of the apparent turnover rate for the immobilised hSO from 0.85 s−1 in 100 mM buffer to 5.26 s−1 in 750 mM buffer. We suggest that both effects originate from the increased mobility of the surface-bound enzyme with increasing ionic strength. In agreement with surface potential calculations we propose that at high ionic strength the enzyme is immobilised via the dimerisation domain to the SAM surface. The flexible loop region connecting the Moco and the Cyt b5 domain allows alternating contact with the Moco interaction site and the SAM surface, thereby promoting the sequential intramolecular and heterogeneous electron transfer from Moco via Cyt b5 to the electrode. At lower ionic strength, the contact time of the Cyt b5 domain with the SAM surface is longer, corresponding to a slower overall electron transfer process.
60 citations
TL;DR: The limit of detection of low-molecular weight compounds in tissue sections, analyzed by matrix assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI), was significantly improved by employing sample washing using a pH-controlled buffer solution.
Abstract: The limit of detection of low-molecular weight compounds in tissue sections, analyzed by matrix assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI), was significantly improved by employing sample washing using a pH-controlled buffer solution. The pH of the washing solutions were set at values whereby the target analytes would have low solubility. Washing the tissue sections in the buffered solution resulted in removal of endogenous soluble ionization-suppressing compounds and salts, while the target compound remained in situ with minor or no delocalization during the buffered washing procedure. Two pharmaceutical compounds (cimetidine and imipramine) and one new protease inhibitor compound were successfully used to evaluate the feasibility of the pH-controlled tissue washing protocol for MALDI-MSI. Enhancement in signal-to-noise ratio was achieved by a factor of up to 10.
60 citations