Standard Calibration Research Articles

A-160 Factor VIII Chromogenic Low Activity Sample Analysis in a Low Calibration Curve Model

Abstract Background Adequate laboratorial diagnostics of hemophilia is essential and could be done by chromogenic and one-stage assays based on APTT methodologies. Adverse effects of medications became less severe recently, but it remains important to be aware of to ensure that treatment is effective and ensure the best possible conditions for affected individuals. Classification of hemophilia according to FVIII activity: mild 25%–5%; moderate, 5%–1% and severe <1%. For new therapies such as emicizumab and some drugs with an extended half-life, the World Federation of Hemophilia recommends the use of a chromogenic assay of FVIII containing bovine FX for monitoring factor FVIII activity. Objetive: evaluate the applicability of a low calibration curve (LCC) in the chromogenic factor VIII (FVIII-Chr) assay by standardizing the dilution of the standard (calibrator) and thus ensuring the accuracy of the analyses in the lower values like severe hemophilia range. Methods The samples were obtained from H&H LAB SAS, which guarantees all requirements. Sysmex® CS 2100i Siemens Healthineers. Calibration was performed with Standard Human Plasma (SHP), together with FVIII-Chr. Quality Control (QC); the accuracy of the LCC was checked. Results Preparation of the LCC: SHP reconstitution, followed by 1:10 dilution between the SHP and the plasma deficient in FVIII. The curve was named FVIII-Chr Low. QC was performed through pathological control (PC) with 2 dilutions: 1) identical to the formation of the low curve, i.e., dilution 1:10 (2.3%–3.9%). 2) dilution 1:30 (0.2%–2%) to accommodate the range of activity comprising severe hemophilia. The values found confirms the curve’s quality. Discussion This study sought to develop a way to detect FVIII activities <1.5% in a reproductive manner, even with a reduced “N” number of samples for severe state. The chromogenic test presents a limit of detection for the optical density of D.O. 0.0080 reporting <0,3% FVIII-Chr activity, which is very close to the most diluted point of the LCC. Conclusion QC performance with PC 1/10 and 1/30 showed excellent reproducibility. With the protocol FVIII Low and LCC (SHP + PDF) it is possible to obtain results of FVIII-Chr <1.0% compatible patients with severe hemophilia clinical condition.

A-341 Development and Validation of an ICP-MS Method to Quantify Lead in Dried Blood Spots

Abstract Introduction The CDC estimates that ∼500 000 children in the US between ages 1–5 have unsafe blood lead concentrations (> 3.5 ug/dL). Lead toxicity can affect all bodily systems and can be detrimental to children's developing brains and nervous systems. Since lead exposure does not always induce obvious and immediate symptoms, screening is an essential tool to public health. Recently, there was a point of care device recalled that was used to measure blood lead across the country. The demise of this method left a gap for lead screening nationally. Dried blood spot (DBS) sampling is an excellent alternative to traditional collections as it is cost effective, less contamination prone, less invasive, and is amenable to non-standard collection locations. The objective of this study was to develop an accurate and precise DBS lead method with the intention of improving access to screening in underserved populations. Methods Lead was detected using an Agilent7800 ICP-MS. DBS were punched (6mm) and lead was extracted into a water based diluent containing EDTA, ammonium pyrrolidine dithiocarbamate, tetramethylammonium hydroxide, Triton X-100, ethanol and iridium. All DBS were sampled from Whatman903 protein saver cards using a 6mm punch. A 6-point calibration curve was made using custom UTAK whole blood lead controls and a diluent blank (target concentrations: 0, 1, 7, 14, 60 and 100 ug/dL). Exact concentrations of the liquid calibrators were determined using a previously validated lead whole blood method. Once the whole blood calibration concentrations were determined, 40 uL of each calibrator was spotted and allowed to dry for at least 24 hours before a 6mm spot was punched and extracted. Precision was determined using three concentrations of UTAK Whole Blood Lead QC (40 uL/spot; 6mm punch). Each level was run in replicates of five for five days. Linearity was confirmed by running five levels of DBS calibration standards for five days. Accuracy was evaluated using Wisconsin DBS Event Proficiency Testing (PT) Samples and results were compared to the peer means. For the method comparison, venous whole blood samples were collected into Royal Blue EDTA metal free vacutainer tubes; DBS samples were spotted directly from the finger (n = 20). Additional comparison samples (n = 10) were derived from the Pennsylvania whole blood PT program by spotting 40 uL. Results The interday precision for the low, mid, and high QC material was 5.0%, 7.5%, and 3.0% at concentrations of 6.8, 20.7, and 35.8 ug/dL, respectively. Lead concentrations from 1.0–100 ug/dL were within the allowable nonlinearity of 1 ug/dL or 5.0% (y = 1.01x-1.6;R = 0.999). Wisconsin DBS PT results (n = 12; range 0.0–38 ug/dL) were accurate within 10% of the peer mean and within acceptability criteria. Comparison of paired whole blood to DBS samples had an average bias of 4.68% (0.31 ug/dL; Y = 1.027x + 0.13(R = 0.999); range 0.1–77.7 ug/dL). Conclusions We developed and validated an accurate and precise lead DBS method using matrix-matched calibrators. This method supports that DBS collection may be an adequate sample to screen for lead exposure and could supplement the current need for additional ways to screen underserved and/or remote populations.

B-297 Effortless and Streamlined Workflow for Absolute Quantitation of Therapeutic Monoclonal Antibodies Using Promise Proteomics mAbXmise Kits and TSQ Altis Plus Mass Spectrometer

Abstract Background Laboratories continuously seek improved productivity and efficacy for clinical testing, ultimately impacting the turn-around time and sample throughput. Various efforts have been made including rapid and high-throughput testing, automation, and high-end instrumentation. This also applies to therapeutic drug monitoring (TDM) of therapeutic monoclonal antibodies (mAbs). In particular, mass spectrometry (MS) has gained significant popularity in clinical laboratories for TDM of mAbs due to its great versatility to measure such complex biological proteins qualitatively and quantitatively. Here we present the streamlined workflow for the absolute quantitation of therapeutic mAbs using the Promise Proteomics mAbXmise kits and the Thermo Scientific™ TSQ Altis™ Plus mass spectrometer. The mAbXmise kit is the first commercial ready-to-use kit that offers all the necessary reagents for the LC-MS/MS assay including the stable-isotope labeled (SIL) proteins of the target mAbs (SIL-mAbs). The TSQ Altis™ Plus mass spectrometer is the latest generation of the TSQ MS series, offering superior acquisition speeds, sensitivity, selectivity, and robustness for routine and high-volume targeted protein quantitation. Methods The experimental workflow followed the instructions provided by Promise Proteomics with minor modifications (refer to instructions manual—https://customer.mabxmise.com). The kits used in this study include pre-coated plates with a full-length SIL-mAb corresponding to each target mAb sequence as internal standards with purity >95% and isotopic corporation >98%. Thus, the ITDM1 kit contains 2 SIL-mAbs and the OTDM1 kit contains 7 SIL-mAbs pre-coated in each plate. The kits also provide buffer stocks, reagents, 6 calibration standards including zero, and 2 QC controls. Each kit provides 12 strips capable of 96 sample preparation. The calibrators and QC samples were added to the mAbXmise plate and subjected to immunocapture followed by trypsin digestion. LC-MS/MS was performed using a Thermo Scientific™ Vanquish™ Flex UHPLC system hyphenated to TSQ Altis™ Plus mass spectrometer. Results Highly comparable results were observed across six replicates for both OTDM1 and ITDM1 kits with R2 values >0.99 and % RSD of peak areas of peptides <15. After confirming the complete sample preparation of 96 samples, an evaluation of LC-MS analytical performance was performed. The results show great linearity with R2 > 0.998 over measured calibration concentration points for all the OTDM1 and ITDM1 target peptides, respectively. Also, the data support the reproducible LC-MS measurement of the entire plate providing % RSD <10. The accuracy of QC samples was determined to be between 94 and 103% for OTDM1 peptides with a precision of <7% CV and between 95 and 107 % for ITDM peptides with a precision of <9% CV. The response of CAL1 (LLOQ) was 5 times higher than CAL0 for all the target peptides with accuracy between 96 and 112% and precision of <11% CV. Additionally, extremely reproducible retention times were observed from all SIL-mAb peptides with RT difference ±0.03 min during the evaluation. Conclusion The workflow tested in this report generated sensitive and robust data with high confidence, emphasizing the capability of MS-based TDM of mAbs as routine testing.

B-203 Development and Validation of an LC/MS/MS Method to Quantify Creatinine in Dried Blood Spots

Abstract Background Health disparities in diagnosis and treatment of chronic kidney disease (CKD) are apparent with Black, Brown, and socially disadvantaged people experiencing worse outcomes. Improving access to CKD screening may decrease disparities. Blood creatinine concentrations are a mainstay in CKD screening, as it is commonly used to estimate glomerular filtration rate. Creatinine is classically measured in serum/plasma using high-throughput chemistry analyzers. Dried blood spots (DBS) could offer a solution to under-screening, but require an alternative method since extraction from DBS retrieves minimal sample volume and is difficult to scale using conventional automation. The purpose of this study was to develop an LC/MS/MS DBS method to quantify creatinine and ultimately to increase screening access for underprivileged communities. Methods Creatinine was measured using a 100 × 2.1 mm Hypersil Silica column with an ABSciex API4000 MS/MS detector. A 5-point calibration curve was made using creatinine certified reference material (Cerilliant) and blank whole blood (UTAK) (target concentrations: 0.575, 0.975, 4.575, 10.575, 20.575 mg/dL). Calibrators were spotted onto Whatman903 cards and allowed to dry for at least 24-hours. A 6 mm punch was used for analysis of calibration points and patient samples. Once punched, water (50 ul) was added and the samples were incubated at 60°C for 15 min before shaking at 800 RPM. Acetonitrile with 2H-creatinine internal standard (IS; .06 mg/dL) was added and the mixture was shaken and centrifuged. The resulting supernatant was diluted to contain 20% water before injecting 10 uL. Creatinine was separated using an isocratic mobile phase (80% Acetonitrile, 20% DI water, 10 mM Ammonium Formate) and detected using MRM mode (Q1 114.0 m/z; Q3 86.8 m/z (quantifier) and 44.5 m/z (qualifier)). For the IS a Q1 of 117.0 m/z and Q3 of 89.9 m/z was applied and the extraction ratio of endogenous creatinine to IS was calculated to determine the concentration. Linearity was confirmed by running five levels of DBS calibration standards for five days. Imprecision was established by running 3 control levels five times for five consecutive days. Control material was purchased from BioRad and run as liquid. Accuracy was assessed using residual liquid CAP serum creatinine proficiency testing (PT) material in triplicate. DBS creatinine concentration determined by LC/MS/MS was compared to paired venous serum creatinine concentration determined by the Roche Cobas enzymatic creatinine assay (n = 63). Results Creatinine concentrations from 0.2–20 mg/dL were within the allowable nonlinearity of 0.075 mg/dL or 5.0% (y = 1.00x−0.010;R = 0.999). Intraday and interday precision was <2%and <3%, respectively for all levels (mean concentrations 1.00, 2.02, and 7.05 mg/dL). Residual CAP PT samples (n = 4) were within 2.5% of the peer group mean. Compared to venous results, DBS had a bias of −0.03 mg/dL (−3.573%) and a linear equation of (y = .904x +0.049; R = 0.83). Conclusion Preliminary results indicate that DBS are a viable sample source for measuring creatinine. Creatinine concentrations measured by DBS compared favorably with CAP PT. A clinically insignificant negative bias was seen when DBS creatinine concentration was compared to venous blood.

An efficient RP-HPLC-PDA Method for Estimating Dolutegravir and Lamivudine in Combined Pharmaceutical Formulations using a Box-Behnken Design Approach

This study used a quality-by-design (QbD) method to build a novel, high-performance reverse-phase fluid chromatography (RP-HPLC) system with diode array detection (DAD) for the simultaneous measurement of dolutegravir (DLG) and lamivudine (LMV) tablets. In accordance with the International Council for Harmonization’s (ICH) requirements, chromatographic conditions were adjusted utilizing the Box-Behnken design (BBD), and the resultant technique was verified for linearity, system appropriateness, precision, accuracy, sensitivity, robustness, and stability of the solution. At retention durations of 2,271 and 3,431 minutes, LMV and DLG peaks were separated using a C-18 column with 150 x 4.6 mm and 5 μm particles. The mobile phase was 0.1% orthophosphoric acid (OPA): acetonitrile (ACN) (50:50, v/v) at a flow rate of 0.8 mL/min and a pH of 3 at 25°C. Peaks were seen at 254 nm and the volume of sample injection was 20L. The percent strength of the commercially available tablet is 98.89 and 98.76 for LMV and DLG, respectively, using a standard calibration curve. The developed RP-HPLC technique’s stability is shown by the suggested RP-HPLC method’s capacity to identify LMV and DLG in the existence of their degradation products. As per ICH requirements, the findings of the validation parameters for linearity, system appropriateness, accuracy, precision, robustness, and sensitivity were all within acceptable limits. It is simple to use, accurate, efficient, and reasonably priced to employ the innovative RP-HPLC technology with BBD application for QbD.

Spectrophotometric Measurement of Lithium in Human Saliva Using the Chromogenic Reagent Thorin

The feasibility of using the chromogenic dye Thorin to spectrophotometrically measure lithium concentration in human saliva was explored. Absorbance wavelength maximum of the Li-Thorin complex was found to be 480 nm. Absorbance at 480 nm was obtained for saliva calibration standards containing 0.00–5.29 mEq/L of lithium. A least-squares fit produced a regression equation y = 0.128x + 1.449, R = 0.997. This was used to predict lithium concentrations in both artificially prepared lithium/saliva test solutions and in hospitalized patients treated with lithium. Results agree well with atomic absorption spectroscopy. Using a reagent blank with an equivalent amount of saliva as the test samples eliminated protein and electrolyte absorbance interference. This study supports the continued exploration of this method as a non-invasive point-of-care testing approach for monitoring saliva lithium in bipolar disorder.

Invariance of unemployment and vacancy dynamics with respect to diminishing returns to labor at the firm level

This paper shows analytically that introducing diminishing returns to labor at the firm level into the Diamond-Mortensen-Pissarides model, followed by recalibration, does not change aggregate dynamics of unemployment and vacancies. This invariance result holds for several standard calibration strategies developed for the model with constant returns, alternative bargaining solutions for the setting with diminishing returns, and different sources of diminishing returns. Invariance makes precise in which sense the common practice of abstracting from diminishing returns is innocuous. It provides an analytical benchmark for quantitative findings obtained in models that do combine a Diamond-Mortensen-Pissarides labor market with diminishing returns at the firm level.

Chemical Exposure Highlighted without Any A Priori Information in an Epidemiological Study by Metabolomic FT-ICR-MS Fingerprinting at High Throughput and High Resolution.

Epidemiological studies aim to assess associations between diseases and risk factors. Such investigations involve a large sample size and require powerful analytical methods to measure the effects of risk factors, resulting in a long analysis time. In this study, chemical exposure markers were detected as the main variables strongly affecting two components coming from a principal component analysis (PCA) exploration of the metabolomic data generated from urinary samples collected on a cohort of about 500 individuals using direct introduction coupled with a Fourier-transform ion cyclotron resonance instrument. The assignment of their chemical identity was first achieved based on their isotopic fine structures detected at very high resolution (Rp > 900,000). Their identification as dimethylbiguanide and sotalol was obtained at level 1, thanks to the available authentic chemical standards, tandem mass spectrometry (MS/MS) experiments, and collision cross section measurements. Epidemiological data confirmed that the subjects discriminated by PCA had declared to be prescribed these drugs for either type II diabetes or cardiac arrhythmia. Concentrations of these drugs in urine samples of interest were also estimated by rapid quantification using an external standard calibration method, direct introduction, and MS/MS experiments. Regression analyses showed a good correlation between the estimated drug concentrations and the scores of individuals distributed on these specific PCs. The detection of these chemical exposure markers proved the potential of the proposed high-throughput approach without any prior drug exposure knowledge as a powerful emerging tool for rapid and large-scale phenotyping of subjects enrolled in epidemiological studies to rapidly characterize the chemical exposome and adherence to medical prescriptions.

Determination of tetrodotoxin in bivalve mollusks by hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry with internal standard calibration and its contamination in Zhejiang province, China

A method was established for determining tetrodotoxin (TTX) in bivalve mollusks by hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry (HILIC-MS/MS) using kasugamycin as the internal standard for quantification. Samples were subjected to ultrasonic extraction with methanol–water (1:1, v/v) containing 0.5% acetic acid, protein precipitation with acetonitrile, clean-up using a cation exchange solid phase extraction cartridge, elution with acetonitrile:water (1:1, v/v) containing 0.3% hydrochloric acid, neutralization with ammonia before HILIC-MS/MS analysis. The average recovery of the samples spiked at 3 levels ranged in 84.6%-98.1% with the relative standard deviation less than 7.2%. Using this method, the contamination of TTX in 429 bivalve mollusk samples collected in the local markets during 2018 and 2020 was investigated. The detection rates were 12.0–18.8%, following the order of oyster > mussel > clam > scallop. High contaminated oysters and mussels with TTX were found in July to August. Moreover, TTX analogs found in bivalve mollusks included 4-epiTTX, 5,6,11-trideoxyTTX, 4,9-anhydroTTX, and 5-deoxyTTX/11-deoxyTTX.

High-Pressure Calibration TiN Equation of State

High pressure is becoming an interesting area of research for originating vital properties in crystalline solids. In the present study, the pressure equation of the state of TiN was investigated by employing various equations of state (EoS) presented in the literature, such as Dodson EoS, Barden EOS, Birch-Murnaghan (B-M) EoS. The EoSs were processed to find the high-pressure effects on the characterizations of TiN such as volume compression ratio, bulk modulus B, Grüneisen parameter, and phonon frequency spectrum. It was shown that a gigantic pressure results in a significant reduction in the volume of the TiN material, and the volume compression ratio reduction, is almost the same for the existing equations of state and the comparative literature results up to a pressure of 80 GPa. The maximum pressure difference is observed to be 4.85 GPa. over the entire pressure of 120GPa. Increasing the bulk modulus with high pressure was expected by the present EoSs, and up to the pressure of about 60 GPa, all curves of bulk modulus are matched with each other. Eventually, a fair comparison has been made between the present results and the first principle approximation along with the generalized gradient approximation method in which a perfect agreement was observed. Finally, the feasibility of TiN EoS as a standard pressure calibration was demonstrated.

Solvent extraction of Cannabis sativa under cryogenic conditions

Extraction of natural products using safe, selective and green solvents is of major importance for their use as ingredients in foods, beverages, cosmetics and pharmaceutical products. In the particular case of cannabis, ethanol at ambient conditions has been found to be very effective in the extraction of cannabinoids, terpenoids, and other valuable metabolites; however, it also extracts chlorophyll, vegetable oils and waxes. Alternatively, the selectivity towards cannabinoids could be increased by operating at lower temperatures. In this regard, this work focused on the cryogenic extraction of leaves and flowers of Cannabis sativa L. with ethanol. Extractions were carried out in a rotary tumbler under batch operation at different temperatures (−80 °C to 20 °C) and solvent:solid ratios (4:1 to 25:1 mL/g). The content of cannabinoids in samples was measured via U-HPLC under isocratic elution using a mixture of a 0.1% wt. formic acid aqueous solution and pure acetonitrile, using a diode array detector at 280 nm, and with an external standard method. Terpenes were quantified by GC using headspace injection, FID detection, and using external standards for calibration. The yields with respect to dry biomass were in-between 0.43% and 4.22% wt. The corresponding cannabinoids content with respect to dry material ranged from 0.25% to 2.67% wt., and these mainly corresponded to cannabidiol and cannabinol. The content of terpenoids was in between 0.01 and 1% wt., and the major fraction corresponded to monoterpenes d-Limonene, β-Myrcene, α-Terpinene, Terpinolene, and p-Cymene. Cryogenic extracts were characterized by a translucent aspect with minor content of coloring compounds and other impurities. Preferred operating conditions corresponded to −20 °C and a solvent:solid ratio of 16:1 mL/g; under these conditions and with respect to dry biomass, the extraction yield was 3.47% wt., the cannabinoids content was 0.67% wt., and the CBD content was 0.59% wt.

Pyrolysis acetylation: A novel on-line Py-GC-MS derivatisation for the characterisation of nitrogen-containing polymers

Several on-line chemical reactions have been combined with Py-GC-MS to improve the chromatographic behaviour of polar pyrolysis products. Derivatisations, principally methylation and silylation, have been widely employed to the analysis of oxygenated pyrolysis products, while the conversion of nitrogen-containing compounds resulted more challenging. The present study shows that amines can be efficiently converted into the corresponding N-substituted amides (acetamides) by conducting pyrolysis in the presence of acetic anhydride (PyAc). PyAc was assessed on three common N-containing polymer families, polyethylenimine (PEI, linear and branched), polyurethane (PUR, based on the methylenediphenyl diisocianate monomer) and nylons (polyamide PA6 and PA66). Upon PyAc, PEI produced a series of N-methyl, ethyl, ethenyl acetamides indicative of the formation of several alkylated monoamines that were more difficult to detect in the free form by conventional Py-GC-MS. Acetyl derivatives of linear acyclic polyamines and piperazines were also identified confirming previous investigations. In the case of PUR, the acetylated 4,4′-diaminodiphenylmethane was generated along with the diisocyanate monomer. PyAc of PA66 produced the acetyl derivative of 1,6-hexyldiamine, while the caprolactam of PA6 was only partially acetylated. The effectiveness of acetylation was confirmed by PyAc of calibration standards for microplastic analysis. Besides the acetylated amines distinctive of PUR and PA66, the acetylated forms of 1,4-butandiol from PUR and bisphenol A from polycarbonate were detected. The results showed the potential of extension of PyAc to other polymer families and highlighted some weaknesses to be solved.

Estimation of Paracetamol in various brands of Paracetamol Tablets and their Comparative Study

Paracetamol is a widely used non-prescription medication and is available in several brands in the market which makes it difficult to select the safe and effective one. Therefore, the study aims to establish the pharmaceutical equivalence of the different brands of paracetamol tablets and to justify the quality of different brands available in the market. The study involves the quantitative analysis of ten different brands of Paracetamol 500 mg tablets, using Ultra Violet Spectrophotometric methods, in which the samples were dissolved in 0.1M sodium hydroxide solution and distilled water and their various absorbances determined at the wavelength (λmax) of 257nm. Quantitative estimation of Paracetamol carried out by UV-Visible spectrophotometric methods, by using standard absorptivity value (assay method given in Indian Pharmacopoeia) and calibration curve method. The percentage content for each sample was calculated byboth methods using appropriate formulae and also determined whether or not they comply with standard specifications as per IP. The percentage content of paracetamol in different brands of paracetamol tablets was compared by IP Method. The results obtained by the IP method and Calibration curve method were also compared.

Reliability of Cold-Formed Steel Sections Subjected to Web Crippling

This study aims to evaluate the structural safety of cold-formed steel sections subjected to concentrated loads in regions without transverse stiffeners, susceptible to web crippling, and dimensioned according to the North American Specification (AISI S100) and the Norma Brasileira (NBR 14762 2010) standard. Experimental data from various sections reported in the literature were analysed, obtaining professional factor statistics. Target reliability indices commonly used in the calibration of cold-formed steel standards were considered. A reliability analysis according to the First-Order Reliability Method (FORM) was developed for several action combinations found in the AISI and NBR standards. In addition to the scenarios prescribed by the AISI (2016), a scenario for the NBR 14762 (2010) standard is proposed, which, although it does not yet exist in the standard, was adopted for research purposes. In the proposed scenario, it was discovered that the resistance factor stipulated by the NBR 14762 (2010) standard did not produce satisfactory outcomes regarding a target reliability index of 2.5 in 10 out of 25 examined cases.

Automatic Piston-Type Flow Standard Device Calibration System

Measurement of flow is crucial for assuring product quality, increasing manufacturing effectiveness, and promoting the development of science and technology. With the advancement of calibration and automation, standard devices using the mass method, volumetric method, and master meter method have limitations, such as low calibration efficiency and automation, large size, and complex operation. Innovations in this area are desperately needed. To realize the automation of calibrating ultrasonic water meters, a piston-type flow standard device calibration system with a high degree of automation, high calibration efficiency, small size, and easy operation was designed. A piston-type flow standard device was designed, the standard device was modeled, the selection of the main hardware and the design of the automated control of the hardware parts were completed; an automation control system adapted to the flow standard device was developed; and, furthermore, a water meter flow point calibration algorithm integrating the start–stop method and the dual-time method, as well as a water meter flow correction algorithm, was devised to improve the efficiency of ultrasonic water meter calibration. An uncertainty assessment of the designed system was completed; the standard uncertainty and expanded uncertainty of the device were 0.013% and 0.026%. Meanwhile, flow calibration tests were conducted, validating the rationality of the automated calibration algorithm for ultrasonic water meters. The results show that ultrasonic water meters calibrated with flow correction have a flow error within ±3% in the “low flow range” and within ±2% in the “high flow range”, with a repeatability of less than 0.05%. This indicates that a piston-type flow standard device, coupled with an automation calibration control system, can efficiently, accurately, and conveniently perform water meter calibration, and the system has good practical value.

High-resolution Spectroscopic Metallicities of Milky Way Cepheid Standards and Their Impact on the Leavitt Law and the Hubble Constant

Milky Way Cepheid variables with accurate Hubble Space Telescope photometry have been established as standards for primary calibration of the cosmic distance ladder to achieve a percent-level determination of the Hubble constant (H 0). These 75 Cepheid standards are the fundamental sample for investigation of possible residual systematics in the local H 0 determination due to metallicity effects on their period–luminosity relations. We obtained new high-resolution (R ∼ 81,000), high-signal-to-noise (S/N ∼ 50–150) multiepoch spectra of 42 out of 75 Cepheid standards using the ESPaDOnS instrument at the 3.6 m Canada–France–Hawaii Telescope. Our spectroscopic metallicity measurements are in good agreement with the literature values with systematic differences up to 0.1 dex due to different metallicity scales. We homogenized and updated the spectroscopic metallicities of all 75 Milky Way Cepheid standards and derived their multiwavelength (GVIJHK s ) period–luminosity–metallicity and period–Wesenheit–metallicity relations using the latest Gaia parallaxes. The metallicity coefficients of these empirically calibrated relations exhibit large uncertainties due to low statistics and a narrow metallicity range (Δ[Fe/H] = 0.6 dex). These metallicity coefficients are up to 3 times better constrained if we include Cepheids in the Large Magellanic Cloud and range between −0.21 ± 0.07 and −0.43 ± 0.06 mag dex−1. The updated spectroscopic metallicities of these Milky Way Cepheid standards were used in the Cepheid–supernovae distance ladder formalism to determine H 0 = 72.9 ± 1.0 km s−1 Mpc−1, suggesting little variation (∼0.1 km s−1 Mpc−1) in the local H 0 measurements due to different Cepheid metallicity scales.

A novel sample preparation method based on polarity grouping for comprehensive determination of 315 pesticides and other contaminants in wolfberry by liquid chromatography-tandem mass spectrometry

A novel sample preparation method based on polarity grouping was developed for the comprehensive determination of 315 undesirable low-weight organic pollutants ranging from polar to weakly polar in wolfberry. The method involves the swelling of the sample in ammonium acetate buffer, two-phase extraction, three-phase extraction, and dispersive solid phase extraction (D-SPE) with the assistance of low-temperature centrifugation and analysis by ultrahigh performance liquid chromatography coupled with electrospray ionization tandem mass (UHPLC-ESI-MS-MS) by using the multiple reaction monitoring mode. The recoveries of the analytes with wide range of polarity were satisfactory. The matrix-fortified standard calibration curves were compared for quantification. The results of linearity were satisfactory with linear regression coefficients (R) ranging from 0.9901 to 1.000. The limits of quantification ranged from 1 μg/kg to 10.0 μg/kg, indicating the compliance of products with legal tolerances. The average recoveries for spiked wolfberry were in the range of 69.3 %–145.2 % with RSD values of 0.2 %–28.6 %. The inter-day precision was in the range of 0.2 %–27.0 %. For over 90 % of the analytes, the recoveries were 70 %–120 % with RSD values below 20 %. The application of this method in routine monitoring programs would imply a drastic reduction of both effort and time.

GC–MS determination of 7-dehydrocholesterol and cholesterol in milk to verify eco-friendly conditions in cow housing

Dairy products are consumed worldwide in large quantities and play an important role in a diet. Labelling of these products as “eco”, “bio” or “organic” has become a trend in recent years, and verification of such advertised properties directly from the dairy products themselves, without the possibility of examining the environment where they were produced, is often next to impossible. However, it is crucial for combating potential false advertising. Herein, a simple approach to distinguish between indoor and outdoor rearing based on quantitation of cholesterol and 7-dehydrocholesterol in milk samples by GC–MS was evaluated. Repeated liquid–liquid extraction into n-heptane resulted in 99% extraction yield. Quantitation by internal standard calibration method with epicoprostanol provided limits of quantitation of 0.814 µg/100 g and 5.60 µg/100 g in milk for cholesterol and 7-dehydrocholesterol, respectively. Values of parameter defined as thousandfold 7-dehydrocholesterol to cholesterol ratio ranged from 0.35 to 1.34 for outdoor reared cows in comparison with indoor category (2.14 to 2.85). A statistically significant difference (at 99% confidence level) between indoor and outdoor rearing was observed. The developed method is an efficient tool for verification of livestock living conditions and, hence, for verification of eco-friendly labelling by dairy producers.

Bioavailability Assessment of Heavy Metals and Organic Pollutants in Water and Soil Using DGT: A Review

In recent years, the diffusive gradients in the thin films (DGT) technique has also been increasingly applied to assess the bioavailability of heavy metals and organic pollutants in the soil. The combination of binding and diffusion phases made from different materials allows for the targeted determination of different target substances. This review briefly introduces the compositions and development of the DGT technique and analyzes the composition structure of DGT and the impact of environmental factors, such as pH, ion strength (IS), and dissolved organic matter (DOM), on the bioavailability evaluation of heavy metals and organic pollutants in soil. Finally, the application potential and broad application prospects of the DGT technique were expected. In addition, standardized DGT technique methods and calibration procedures are conducive to the establishment of a more stable and reliable measurement system to enhance the robustness of the DGT technique application in the soil.

Histochemical mapping of the duration of action of photobiomodulation on cytochrome c oxidase in the rat brain.

This is the first study mapping the duration of action of in vivo photobiomodulation (PBM) on cytochrome-c-oxidase (CCO). In cellular bioenergetics, CCO is the terminal rate-limiting enzyme in the mitochondrial electron transport chain, which catalyzes oxygen utilization for aerobic energy production. PBM using transcranial infrared laser stimulation (TILS) is a promising intervention for non-invasively modulating CCO in the brain. TILS of the human prefrontal cortex directly causes CCO photo-oxidation, which is associated with increased cerebral oxygenation and improved cognition. This experiment aimed to map the duration of action of in vivo PBM on CCO activity in discrete neuroanatomic locations within rat brains up to 4 weeks after a single TILS session (50 s, 1064 nm CW, 250 mW/cm2). Control brains from rats treated with a sham session without TILS (laser off) were compared to brains from TILS-treated rats that were collected 1 day, 2 weeks, or 4 weeks post-TILS. Cryostat sections of the 36 collected brains were processed using quantitative enzyme histochemistry and digitally imaged. Densitometric readings of 28 regions of interest were recorded and converted to CCO activity units of oxygen utilization using calibration standards. Data analysis (ANCOVA) compared each laser-treated group to sham with whole-brain average as a covariate. The prefrontal infralimbic cortex showed the earliest significant increase in CCO activity between 1-day post-TILS and sham groups, which continued elevated for 2-4 weeks post-TILS. Significant differences in CCO activity between 2-weeks and sham groups were also found in the lateral septum, accumbens core, CA3 of the hippocampus, and the molecular layer of the hippocampus. The medial amygdala showed a significant decrease in CCO activity between 4-weeks and sham. Further analyses showed significant inter-regional CCO activity correlations among the brain regions as the result of TILS, with the most pronounced changes at 4-weeks post-stimulation. The time course of changes in CCO activity and network connectivity suggested that TILS caused different neuroplasticity types of bioenergetic changes at different time scales, depending on brain region and its depth from the cortex. In conclusion, this controlled CCO histochemical study demonstrated a long-lasting duration of action of PBM in the rat brain.