Electrochemical Analysis for Total Alkalinity of Water by the Measurement of Cathodic Prepeak of Quinone Caused by Surplus Acid.

In this study, an electrochemical analysis, coupled with the concept of back neutralization titration and the voltammetric determination of surplus acid, is proposed for determining the total alkalinity of water samples. When linear sweep voltammetry of 3,5-di-tert-butyl-1,2-benzoquinone (DBBQ) with HSO in a water and ethanol (44 : 56, v/v) mixture was carried out using a bare glassy carbon working electrode, a cathodic prepeak of DBBQ caused by HSO was observed on the voltammogram at a more positive potential than when compared with the original cathodic peak of DBBQ. When similar voltammetry was carried out in the presence of NaCO and HSO, the cathodic prepeak height of DBBQ was decreased with an increase in the NaCO concentration.

Psychological Barriers to the Use of Opioid Analgesics for Treating Pain in Patients With Advanced Recurrent Cancer: A Multicenter Cohort Study.

Background: We aimed to gain insight into psychological barriers toward initiation of strong opioid analgesic use in patients with advanced recurrent cancer.

Methods: This study included 46 patients who were prescribed with opioid analgesics for advanced recurrent cancer. The primary outcome was psychological barriers assessed using the Japanese version of the Barriers Questionnaire-II (JBQ-II).

Statistical reliability of a relative standard deviation of chromatographic peak area estimated by a chemometric tool based on the FUMI theory.

In pharmaceutical analysis using a high-performance liquid chromatography (HPLC) system, repeatability assessment is significant to obtain reliable and precise quantitative results. The purpose of the present study is to experimentally show the statistical reliability of a relative standard deviation (RSD) of peak area estimated by a chemometric tool based on probability theory, called the function of mutual information (FUMI) theory, which stochastically provided an RSD of peak area and SD of baseline areas with width k (s(k)) from noises and a signal on a single chromatogram. An ultra-high-performance liquid chromatography with ultraviolet detection (UHPLC-UV) for determining ergosterol was applied as an example of the repeatability assessment.

Determination of oxalic acid in herbal medicines by semi-micro hydrophilic interaction liquid chromatography coupled with electrochemical detection.

In this study, the determination of oxalic acid in herbal medicines was performed by using a hydrophilic interaction liquid chromatography coupled with electrochemical detection (HILIC-ECD) method. A semi-micro column packed with amide-silica particles and an acetonitrile-30 mM phosphate buffer (pH 6.8) mixture (65:35, v/v) were used as the stationary and mobile phases, respectively, in the HILIC-ECD.

Gradient elution of hydroxyacetophenones by supercritical fluid chromatography with electrochemical detection.

Linear gradient elution supercritical fluid chromatography with electrochemical detection was developed using hydroxyacetophenones as analytes. Separation was carried out with a diol column (4.6 mm id × 250 mm length, 5 μm) as a stationary phase and a mixture of supercritical carbon dioxide and methanol as a mobile phase, where the ratio of carbon dioxide and methanol was changed from 99:1 (v/v) to 60:40 (v/v).

Simultaneous determination of deuterium-labeled ergosterol and brassicasterol in stroke-prone spontaneously hypertensive rats by ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry.

A previous study has shown that brassicasterol- was detected in the serum of stroke-prone spontaneously hypertensive rats after oral administration of ergosterol-. To quantitatively evaluate the serum concentration of brassicasterol-, an ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed for the simultaneous determination of picolinyl ester-derivatized ergosterol- and brassicasterol-. The separation was performed on an ODS column (Waters Acquity UPLC BEH C18) with a mobile phase consisting of methanol and water containing 0.

Electrochemical determination of free amino nitrogen in aged lean beef by the measurement of surplus acid after neutralization.

In this study, an electroanalytical method, which is based on the concept of acid-base back titration and the electrochemical sensing of acids by means of the reduction of quinone, is proposed for determining free amino nitrogen (FAN) in lean beef samples. To perform the electrochemical determination of FAN in beef samples, the following voltammetric behaviors of 3,5-di-tert-butyl-1,2-benzoquinone (DBBQ) in the presence of acid have been applied: (1) A cathodic prepeak height of DBBQ caused by HCl (i) is proportional to the HCl concentration in the electrolyte solution. (2) i is linearly decreased with an increase in amino acids concentration in the electrolyte solution after the amino acids are neutralized by excess HCl.

Electrochemical determination of emodin in acidic media by high-performance liquid chromatography and its application to Polygoni Multiflori Radix samples.

Electrochemical reduction of emodin under acidic media occurs at a less negative potential when compared with that under neutral media. When emodin is electrochemically detected at a less negative potential, a decrease in background noise and improvement in specificity benefit the development of high-performance liquid chromatography with electrochemical detection (HPLC-ECD) for its determination. HPLC-ECD was performed using an octadecyl silica column, acetonitrile-water (60:40, v/v) containing 5 mmol L hydrochloric acid and 10 mmol L lithium perchlorate, as a mobile phase, and an applied potential at - 0.

Effects of digital processing on repeatability assessment of a multiple reaction monitoring liquid chromatography-tandem mass spectrometry system by ISO 11843-7.

ISO 11843 part 7 (ISO 11843-7) can provide a standard deviation (SD) of area measurements of a target peak through the stochastic behaviors of instrumental noises. The purpose of this study is to demonstrate that ISO 11843-7 can be applied to assess repeatability in an isocratic liquid chromatography-tandem mass spectrometry (LC-MS/MS) system without repetitive measurements. The relative standard deviation (RSD) of the peak area of ergosterol picolinyl ester, which was used as an example, on a multiple reaction monitoring (MRM) chromatogram was determined by ISO 11843-7.

Chemometric evaluations of repeatability and detection limit in high-performance liquid chromatography with electrochemical detection.

The function of mutual information (FUMI) theory proposes that it is possible to obtain a relative standard deviation (RSD) of the peak area of an analyte from baseline noises and a signal on a single chromatogram when the analyte concentrations are proportional to their peak areas. In this study, we demonstrate that the FUMI theory using noise parametrization by the difference method is applicable for the evaluations of repeatability and detection limit (DL) in high-performance liquid chromatography with electrochemical detection (HPLC-ECD). HPLC-ECD for determining vincristine (VCR) was taken as an example, and VCR was detected on a glassy carbon surface at +0.

Psychological barriers to the use of opioid analgesics for treating pain in patients with advanced recurrent cancer (BAROC): protocol for a multicentre cohort study.

Introduction: Opioid analgesics are essential for treating cancer pain. However, patients are sometimes reluctant to use them because of concerns about addiction and dependence. Rapid pain relief following opioid administration may help overcome the psychological barriers to opioid analgesic use.

Effects of sampling rate and noise filter processing on repeatability assessment in UHPLC with ultraviolet detection based on the ISO 11843-7.

The present study examines whether short measurement time and noise filter processing in an ultra-high-performance liquid chromatography with ultraviolet detection (UHPLC-UV) contribute to limitations for repeatability assessment based on the ISO 11843 part 7 (ISO 11843-7), which can stochastically provide a measurement standard deviation (SD) caused by baseline noise (S). In this study, ergosterol was used as an example in UHPLC-UV analysis. From the results of power spectrum analysis of baseline noise, 1024 consecutive digital data points provided a suitable S.

Supercritical fluid chromatography with post-column addition of supporting electrolyte solution for electrochemical determination of tocopherol and tocotrienol isomers.

A supercritical fluid chromatography with electrochemical detection system was developed for the simultaneous determination of tocopherol and tocotrienol isomers. The supercritical fluid chromatography with electrochemical detection system was connected with an additional pump to create a flow path to add a supporting electrolyte solution. The supporting electrolyte solution was mixed with a mobile phase in a post-column fashion, enabling the independent control of the separation and detection.

Determination of Phenolic Compounds in Beverages by Three-Flow Channel Isocratic HPLC with Electrochemical Detections Using a Column-Switching Technique.

For the quantitative analysis of phenolic compounds in beverage samples, a three-flow channel isocratic HPLC with electrochemical detection (3LC-ECD) system was devised using a column-switching technique. Phenolic compounds with significantly different hydrophobicity (the range of calculated log P: -0.77 to 3.

A simple method for daily inspections of gas chromatography-mass spectrometry systems with an instrumental detection limit as an indicator.

The purpose of this paper is to propose a simple method for daily inspections of a gas chromatography-mass spectrometry (GC-MS) system with an instrumental detection limit (IDL) as an indicator. A definition of DLs by ISO is 3.3σ where σ denotes the standard deviation (SD) of blank measurements.

Emerging Separation Techniques in Supercritical Fluid Chromatography.

Supercritical fluid chromatography (SFC) has unique separative characteristics distinguished from those of HPLC and gas chromatography. At present, SFC is widely used and there are many applications in various biological, medical, and pharmaceutical fields. In this review, we focus on recently developed novel techniques related to SFC separation including: new column stationary phases, microfluidics, two-dimensional separation, and gas-liquid separation.

Chemometric evaluation of repeatability of internal standard methods in high-performance liquid chromatography with a Japanese pharmacopoeia assay for indomethacin as an example.

The purpose of this study is to elucidate uncertainty structures of internal standard (IS) methods as compared with absolute calibration methods in liquid chromatography. A quantitative test of indomethacin with butyl 4-hydroxybenzoate as an IS in high-performance liquid chromatography with ultra-violet detection is taken here as an example. The repeatability is evaluated by both a usual statistical method of repetition and a theoretical approach, called the function of mutual information (FUMI) theory.

An automated assessment system of limits of detection and quantitation in gradient high-performance liquid chromatography with ultraviolet detection.

A previous paper of this series of study put forward a basic model of an automated system for predicting detection limits and showed its application to a simple example of isocratic high-performance liquid chromatography (HPLC). This paper describes an expansion of the basic system into gradient HPLC. The most serious problem with the expansion is a long-term variation in backgrounds, called gradient baseline drifts, which in theory cannot be covered by a noise model (stationary random process) of the original system.

HPLC with electrochemical detection for determining homogentisic acid and its application to urine from rats fed tyrosine-enriched food.

A highly sensitive method for determining urine homogentisic acid (HGA) is required to provide adequate diagnosis and therapy for alkaptonuria in early stages. In this study, we developed a highly sensitive high-performance liquid chromatography with electrochemical detection (HPLC-ECD) for determining HGA in urine. In order to obtain a chromatogram of HGA by HPLC-ECD, an oxidation current was monitored at +0.

Electrochemical Determination of Titratable Acidity for the Discrimination of Schisandrae Chinensis Fructus and Schisandrae Sphenantherae Fructus.

A simple electrochemical procedure has been developed for determining the titratable acidity in Schisandrae Chinensis Fructus (SCF) and Schisandrae Sphenantherae Fructus (SSF) by means of reduction of quinone in the presence of acid compounds. To measure a voltammogram, a test solution was prepared by mixing a water extract from SCF or SSF and an electrolyte cocktail containing 3,5-di-tert-butyl-1,2-benzoquinone and NaCl. The quantitative results of titratable acidity in the SCF and SSF samples by the present voltammetry were in good agreement with those by neutralization titration using 0.

An automated system for predicting detection limit and precision profile from a chromatogram.

This paper presents a basic model of an automated system for predicting the detection limit and precision profile (plot of relative standard deviation (RSD) of measurements against concentration) in chromatography. The fundamental assumption is that the major source of response errors at low sample concentrations is background noise and at high concentrations, it is the volumes injected into an HPLC system by a sample injector. The noise is approximated by the mixed random processes of the first order autoregressive process AR(1) and white noise.

Profiling and isomer recognition of phenylethanoid glycosides from Magnolia officinalis based on diagnostic/holistic fragment ions analysis coupled with chemometrics.

Isomers derived from natural products are promising candidates for drug discovery. However, characterization of isomers by mass spectrometry, especially stereoisomers and positional isomers, remains a large challenge due to insufficient reference standards and isomers' highly similar fragmentation pathways or nondistinctive ion abundances. Herein, this report presents the first proposal of a method, combining multiple diagnostic ion/neutral loss (DINL) postanalysis and especially untargeted fingerprint analysis of all fragment ions (FAAFI) by means of a home-made program and chemometrics, to profile chemical components and recognize their isomers derived from medicinal plants.