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 H2SO4 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 H2SO4 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 Na2CO3 and H2SO4, the cathodic prepeak height of DBBQ was decreased with an increase in the Na2CO3 concentration. The decrease of the cathodic prepeak height of DBBQ was found to be linearly related to the Na2CO3 concentration ranging from 0.025 to 2.5 mM (r2 = 0.998). The total equivalent concentrations of inorganic bases in samples of mineral water and tap water were determined, and then the results were converted to the total alkalinities of the water samples (mg/L CaCO3). The total alkalinities of the water samples determined by the present electrochemical analysis were essentially the same compared with those by the neutralization titration method. From these results, we were able to demonstrate that the present electrochemical analysis with accuracy and precision could be applied to determine the total alkalinity, which is one of the indicators to examine water quality. The present electrochemical analysis would contribute to achieving the sustainable development goals (SDGs) of #6 and #14.

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). The secondary outcomes were psychological changes and pain relief one week after the induction of strong opioid analgesics. Results: The mean age of participants was 63.6 years. Furthermore, 26.1% had an Eastern Cooperative Oncology Group (ECOG) performance status of ≥3. The mean JBQ-II total score was 1.97 (95% confidence interval: 1.75-2.19). At the initiation of opioid therapy, there was no difference in the total scores between the baseline and one week later. Nevertheless, there was a significant difference in the subscale "disease progression" score (mean 2.97 vs. 2.59, difference in means 0.38, standard error 0.16, p = 0.026). Personalized Pain Goal (PPG) was achieved in about half of the participants, and a trend toward a higher score in the subscale "harmful effects" (concern about adverse events) was observed in those who did not achieve PPG. Conclusion: This study showed that patients with advanced recurrent cancer have psychological barriers to opioid induction. The relationship between the presence of psychological barriers before and after induction of opioid analgesics and the speed of pain improvement was determined. The results may provide fundamental information for prospective intervention studies to develop individualized education programs for patients with psychological barriers to opioids.Clinical Trial Registration Number UMIN000042443.

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. A potential of + 1.1 V vs. Ag/AgCl was applied to a glassy carbon working electrode. The ratio of the peak height of oxalic acid to that of the internal standard (synephrine) was proportional to the concentration of 0.45 µg L-1 to 1.8 mg L-1 with a correlation coefficient of 0.999. The detection limit (signal-to-noise ratio, S/N = 3) of oxalic acid was 0.17 µg L-1. By the HILIC-ECD, the oxalic acid content in crude drugs and Kampo medicine extract granules (Zingiberis Rhizoma Processum, Pinelliae Tuber, Sho-seiryu-to, Hange-shashin-to, etc.) were determined with less than 2.9% relative standard deviation (RSD, n = 6), and their recoveries were more than 88.7% with less than 3.3% RSD (n = 6). In conclusion, we demonstrated that the HILIC-ECD performed measurements that were quite selective, accurate, and precise for the determination of oxalic acid in herbal medicines.

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 (iH) is proportional to the HCl concentration in the electrolyte solution. (2) iH is linearly decreased with an increase in amino acids concentration in the electrolyte solution after the amino acids are neutralized by excess HCl. By the present electroanalytical method, FAN in a lean beef sample was determined to be 4.70 mgN g-1 with a repeatability of 3.4% relative standard deviation (n = 5). This result by the present electroanalytical method was in good agreement with a colorimetric method using a ninhydrin reagent. Moreover, the present electroanalytical method was able to monitor increases of FAN in lean beef samples during wet-aging. These results demonstrate the present electroanalytical method could help in the development of an on-site analysis for estimating aged beef samples via the determination of FANs.

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). For the electrochemical detection, methanol containing 1.0 mol L-1 ammonium acetate was used as a supporting electrolyte solution and + 1.2 V was applied to the electrochemical cell. We compared the performance of the present method to isocratic elution supercritical fluid chromatography, and the repeatability, linearity, and detection capability all showed better analytical parameters in the gradient elution. As such, we found that gradient elution supercritical fluid chromatography can achieve the faster separation and save resources compared to isocratic elution. Thus, the present method may contribute to the development of green analytical methods.

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-d1 was detected in the serum of stroke-prone spontaneously hypertensive rats after oral administration of ergosterol-d1. To quantitatively evaluate the serum concentration of brassicasterol-d1, an ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed for the simultaneous determination of picolinyl ester-derivatized ergosterol-d1 and brassicasterol-d1. The separation was performed on an ODS column (Waters Acquity UPLC BEH C18) with a mobile phase consisting of methanol and water containing 0.1% acetic acid (95/5, v/v). Linear calibration curves in the presence of the serum were obtained in a concentration range of 0.04-8 µg mL-1. Recovery rates of 95.6-119% were obtained with an RSD (n = 6) of less than 7.5%. The method was applied to the determination of time-concentration curves of ergosterol-d1 and brassicasterol-d1 in stroke-prone spontaneously hypertensive rats, showing a pharmacokinetic profile of ergosterol-d1 where the peak serum concentration of brassicasterol-d1 was 3-fold higher than that of ergosterol-d1.

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-1 hydrochloric acid and 10 mmol L-1 lithium perchlorate, as a mobile phase, and an applied potential at - 0.4 V vs. Ag/AgCl. Under these optimal HPLC-ECD conditions, the detection limit (signal-to-noise ratio, S/N = 3) of emodin was 0.61 µg L-1. When this HPLC-ECD system was applied to the determination of emodin in Polygoni Multiflori Radix (PMR) samples, other peaks did not appear close to the emodin peak on a chromatogram. The emodin contents in PMR samples were determined with relative standard deviations (RSDs, n = 6) of less than 3.9%, and their recoveries ranged from 92 to 106%. We have shown that our HPLC-ECD system performed an accurate, precise, and specific determination of emodin in PMR samples.

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. The RSD by ISO 11843-7 (N = 1) was within a 95% confidence band of the RSD by repetitive measurements (N = 6). Moreover, the effects of digital smoothing, such as moving average, were also examined on the repeatability assessment in LC-MS/MS by ISO 11843-7. From the results of the comparisons of the RSDs obtained by ISO 11843-7 and the repetitive measurements, it was shown that suitable RSDs of the peak area were obtained from the smoothed MRM chromatograms by the moving average for narrow data point windows (e.g., one-sixth of the peak width). In conclusion, the utility of repeatability assessment based on ISO 11843-7 has been expanded for the validation of an LC-MS/MS system.

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. This study aims to determine the relationship between psychological resistance to strong opioid analgesic use and pain amelioration speed in patients with advanced recurrent cancer. METHODS AND ANALYSIS: This ongoing, multicentre, observational study enrols patients aged 20 years or older with distant metastasis or advanced recurrent cancer receiving strong opioid analgesics for cancer pain for the first time. All participants, both inpatient and outpatient, were recruited from five Japanese hospitals. We are investigating the relationship between psychological barriers at the start of treatment and pain relief during the first week of treatment in these patients. The primary outcome is the Japanese version of the Barriers Questionnaire-II score at baseline. The secondary outcomes are the relationships between psychological barriers to strong opioid analgesic use and changes in pain over time. The participants are asked to fill out an electronic patient-reported outcome daily during the first week of treatment. The sample size was determined based on the number of patients in the year prior to study commencement who used strong opioid analgesics, met the eligibility criteria and could be expected to consent to participate in the study. ETHICS AND DISSEMINATION: The study protocol was approved by the ethics committee (approval ID B200600091) of Yokohama City University on 24 August 2020. The protocol has been reviewed by the institutional review boards at the four participating study sites. The results will be published in a peer-reviewed journal and will be presented at a relevant meeting. TRIAL REGISTRATION NUMBER: UMIN000042443.

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 +0.8 V vs. Ag/AgCl. In the comparisons of precision profiles (plots of RSD of peak area against concentrations of an analyte), the stochastically estimated RSD (N = 1) by the FUMI theory fell within the 95% confidence intervals of statistically estimated RSD (N = 6) by repetitive measurements. Furthermore, the DL obtained by the FUMI theory (3.3×SD) was almost the same value as that by the signal-to-noise ratio (S/N) = 3. Moreover, we introduced a manual method for signal-noise resolution to obtain noise parameters from a chromatogram with low-pass Bessel filter processing. In conclusion, our results show that the FUMI theory using noise parametrization by the difference method can be applied to the evaluations of repeatability and DL in HPLC-ECD without and with a low-pass Bessel filter.

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 (SB). 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 SB. Thus, it was found that an SB can be obtained from about 1 min of baseline when a chromatogram was recorded at sampling rate of 20 points s-1 in the present UHPLC-UV system. The relative SDs (RSDs) of the peak area obtained by the ISO 11843-7 were within 95% of the confidential intervals of the RSDs obtained by repetitive measurements, indicating the ISO 11843-7 is applicable to estimate repeatability in a UHPLC-UV system. In a similar way, we found that the RSD of the peak area obtained from a chromatogram with noise filter processing in UHPLC-UV could also be estimated by the ISO 11843-7. In conclusion, we experimentally demonstrate that short measurement time and noise filter processing are not limitations for repeatability assessment based on the ISO 11843-7.

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. After optimization of the measurement conditions, vitamin E isomers and an internal standard substance (2,2,5,7,8-pentamethyl-6-hydroxychroman) were separated within 30 min using a mixture of supercritical carbon dioxide and methanol (99:1, v/v) as a mobile phase and a cyanopropyl column (4.6 mm inner diameter × 250 mm length, 5 µm). For the electrochemical detection, methanol containing 1.0 mol/L ammonium acetate was used as a supporting electrolyte solution, and the applied potential was set at +0.8 V. This analytical method showed good linearity (5-100 µg/mL) and repeatability (less than 2.5% relative standard deviation, n = 6) and was applicable to the determination of tocopherol and tocotrienol isomers in nutrition supplements.

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 3.02) were simultaneously measured to draw three chromatograms by the 3LC-ECD; the peaks of gallic acid (GA), protocatechuic acid (PCA), and gallocatechin (GC) were observed at electrochemical detector 1 (D1) within 42 min, the peaks of procyanidin B3 (B3), epigallocatechin (EGC), catechin (C), epicatechin (EC), procyanidin B2 (B2), ethyl gallate (Eg), and epigallocatechin gallate (EGCg) were observed at D2 within 50 min, and the peaks of epicatechin gallate (ECg), gallocatechin gallate (GCg), catechin gallate (Cg), propyl gallate (Pg), and resveratrol (RVT) were observed at D3 within 70 min. The relationships between the phenolic compound concentrations and their chromatographic peak heights gave good linearity with correlation coefficients of more than 0.998. The detection limits of the phenolic compounds by the 3LC-ECD ranged from 0.6 to 3.0 µg/L. Further, the phenolic compound concentrations of commercially available teas and wines were determined with a relative standard deviation (RSD) of less than 4.9% (n = 6), and their recoveries ranged from 91 to 109%. These results indicate that the 3LC-ECD system provided an accurate, precise, and specific determination of the phenolic compounds in beverages without affecting the matrices derived from these samples.

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. Estimation of σ is carried out according to the function of mutual information (FUMI) theory and actually with commercial software (TOCO19). An IDL which is a combination of a signal area, width and noise level is concluded to be a good indicator for daily inspections compared with each of its constituents. Methyl stearate is used as a standard material for the daily inspection of a programmed-temperature GC-MS system. A short chromatogram of 1800 data points (1.5 min) containing a target signal and background noise is fit for the IDL prediction by TOCO19. The relative SDs (RSDs) based on the theoretically estimated σ are shown to coincide with statistical results from repeated measurements within 95% confidence intervals. Column temperature is observed to affect IDLs through background fluctuation and then temperature-IDL relationship is examined in a range from 170 to 270 °C. Actual daily inspections over a month are demonstrated.

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. In addition, we discuss the application of SFC using a water-containing modifier to biological molecules such as amino acids, peptides, and small proteins that had been challenging analytes.

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. The latter predicts the precision from noise and signals of instrumental output. Plots of relative standard deviations (RSDs) of measurements against analyte amounts, called precision profiles, are compared between the IS methods for indomethacin and their corresponding absolute calibration methods over a wide range of amount. Sample injection errors are observed to be effectively eliminated at high amounts by the IS methods, but at low amounts where background random noise dominates over the other error, the superiority of the IS methods is overshadowed and the precision of both the methods is almost comparable. The smallest possible amount of IS material without spoiling the integrity of analysis is estimated from the precision profiles.

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 +0.5 V vs. Ag/AgCl. The peak heights of HGA showed linearity (r = 0.999) ranging from 4.2 ng/mL to 168 ng/mL, and the detection limit was 1.2 ng/mL (signal-to-noise ratio, S/N = 3). In recovery tests using human control urine spiked with an HGA standard, the recoveries of HGA were more than 93.2 %, and the relative standard deviations (n = 6) were less than 1.9 %. As an in vivo application using male Wistar rats, the level of urine HGA, which was metabolized from tyrosine in tyrosine-enriched food, was determined by this HPLC-ECD method. The determination of HGA in urine by this HPLC-ECD method requires only 0.1 mL of a rat urine specimen and simple sample preparation consisting of dilution and filtration.

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. This paper demonstrates that the above problem can be solved with modifying a parametrization procedure of the noise model. The essential role of the system is to predict the standard deviation (SD) of measurements at low concentrations from a chromatogram without repeated measurements of real samples. Laboratory-made software enables the automated assessment of the limits of detection and quantitation for each of chromatographically separated signals in a single run. Simulated background noise which consists of the stationary noise model with linear slopes is used to confirm the accuracy and reproducibility of the automated prediction. A gradient HPLC determination for cefaclor is taken as an example. The parametrization modification improves the correlation coefficient, r2, between the observed and theoretical distributions of the area measurements from 0.373 to 0.966. The statistical confidence levels of the theoretically predicted relative SDs for cefaclor were verified by comparing them with those obtained by repeated experiments (r2 = 0.989). The limits of detection (= 3.3 × SD = 18.0 µg/L) and quantitation (= 10 × SD = 54.7 µg/L) for cefaclor have signal-to-noise ratios close to the commonly adopted values, 3 and 10, respectively.

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 0.1 M NaOH (r2 = 0.980): y = 1.003x + 0.010, where the y- and x-axes were the titratable acidity obtained by the present voltammetry and the neutralization titration, respectively. Further, the titratable acidities in the SSF samples were significantly lower than those in the SCF samples (p < 0.01). From these findings, we show that the titratable acidity is useful as an indicator to discriminate between SCF and SSF. Moreover, a prototype of electrochemical portable sensor for on-site analysis has been provided to perform this procedure.