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Objective To summarize and analyze the difficulties and key points in the measurement of gross α and gross β radioactivity in water based on the results of national measurement capability comparison assessment, and provide the basis and reference for the future work and the development of new local standards. Methods The research team participated in the comparison assessment for measurement of the gross radioactivity in water samples organized by National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention. According to the comparison assessment results and the content in the national standard GB/T 5750.13—2023 (published draft), the steps of spike recovery involved during the measurement were analyzed and discussed. Two different formulas used for spike recovery calculation were analyzed for their impact on the final measurement results. Results When the spike recovery F(derived) derived from the formulas was used for result calculation, the spike recovery ranged as follows: gross α: 63.00%−84.60%, and gross β: 95.0%−99.1%; 3/6 of the comparison results were determined as excellent and 3/6 as pass as a whole (among them, 4 were excellent and 2 were pass for both single gross α assessment items and single gross β assessment items). When the spike recovery F from the GB/T 5750.13—2023 (published draft) was used for result calculation, the spike recovery ranged as follows: gross α: 39.69%−71.57%, and gross β: 90.25%−98.21%; 5/6 of the comparison results were determined as fail and 1/6 as pass (among them, 5 were fail and 1 was pass for single gross α assessment items; 5 were excellent and 1 was pass for single gross β assessment items). When two different formulas were used for spike recovery calculation, there was a significant difference in gross α radioactivity measurement (t = 4.27, P = 0.03 < 0.05), but there was no significant difference in gross β radioactivity measurement (t = 0.667, P = 0.524 > 0.05). Conclusion In the measurement of gross α and gross β radioactivity in water, appropriate reference to the spike recovery has a great influence on the measurement results. Therefore, quality control should be strengthened to further ensure the accuracy of measurement.

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It has long been known that containers for sample analysis or storage can play a role in endotoxin recovery and have to be taken into account when determining endotoxin concentrations. However, there is little data on the effects of containers regarding (1→3)-ß-D-glucan, which plays a role as a contaminant in endotoxin measurements. To determine the effect of the container on (1→3)-ß-D-glucan measurements, four different types of containers were investigated at different temperatures and stored for up to 28 days. For short-term storage for 3 h at room temperature, no effect of the container on the (1→3)-ß-D-glucan recovery could be observed, but for storage at -20 °C, the results indicate that the storage time and temperature influences (1→3)-ß-D-glucan detection. All containers showed a trend of lower recoveries over time, but the polyethylene container showed a significantly lower recovery compared to the other containers. We also showed that freeze/thaw cycles had a strong influence on the recovery of (1→3)-ß-D-glucan in polyethylene containers. Our study showed that the container can affect not only the detection of endotoxins but also the detection of (1→3)-ß-D-glucans.

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Quantitative polymerase chain reaction (qPCR) has emerged as an important bioanalytical method for assessing the pharmacokinetics of human-cell-based medicinal products after xenotransplantation into immunodeficient mice. A particular challenge in bioanalytical qPCR studies is that the different tissues of the host organism can affect amplification efficiency and amplicon detection to varying degrees, and ignoring these matrix effects can easily cause a significant underestimation of the true number of target cells in a sample. Here, we describe the development and drug regulatory-compliant validation of a TaqMan® qPCR assay for the quantification of mesenchymal stromal cells in the range of 125 to 20,000 cells/200 µL lysate via the amplification of a human-specific, highly repetitive α-satellite DNA sequence of the chromosome 17 centromere region HSSATA17. An assessment of matrix effects in 14 different mouse tissues and blood revealed a wide range of spike recovery rates across the different tissue types, from 11 to 174%. Based on these observations, we propose performing systematic spike-and-recovery experiments during assay validation and correcting for the effects of the different tissue matrices on cell quantification in subsequent bioanalytical studies by multiplying the back-calculated cell number by tissue-specific factors derived from the inverse of the validated percent recovery rate.

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Osmium is defined in the international council for harmonization (ICH-Q3D) guidelines as an element whose concentration can be determined by validated methods including microwave-assisted nitric acid digestion and inductively coupled plasma mass spectrometry. However, microwave digestion using nitric acid is known to result in osmium recoveries higher than the theoretical values in spiked tests because of the formation of highly volatile osmium tetroxide in an oxidation reaction. To stabilize osmium, the addition of thiourea as a complexing agent has been tested and proved its utility. It remains unclear whether other compounds can prevent the over-recovery of osmium. In this study, we investigated four compounds, thiourea, ascorbic acid, sodium sulfite, and potassium metabisulfite, that could reduce the overestimation of osmium isotopes. The minimum amounts of thiourea, ascorbic acid, sodium sulfite, and potassium metabisulfite required to stabilize 10 ng/mL osmium in blank matrix were 1.0, 1.0, 2.5, and 2.5 g/L, respectively. The relative standard deviations obtained from 12 analyses for each stabilization solution were less than 3.3% in thiourea, 12.7% in ascorbic acid, 9.0% in sodium sulfite, and 10.6% in potassium metabisulfite. The stabilization solutions were investigated in a digested tablet matrix and were found to be effective. The impact of adding stabilization solutions on the determination of all ICH-Q3D element concentrations was also evaluated. As stabilization solutions had a small or significant impact on the determination of some elements, it was concluded that osmium determination should be conducted independently.

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BACKGROUND: Amoxicillin (AMX), which is one of the ß-lactam antibiotics used in the treatment of bacterial infections, is known to have a serious mechanism of resistance necessitating continuous monitoring of its level in pharmaceutical and serum samples. RESULTS: In this study, we presented selective, accurate, and precise square wave voltammetric method based on poly(4-amino-3-hydroxynaphthalene-1-sulfonic acid) modified glassy carbon electrode (poly(AHNSA/GCE)) for determination of amoxicillin in four selected tablet brands. Appearance of a peak in the oxidative scan direction without a peak in the reductive direction of cyclic voltammograms of both bare GCE and poly(AHNSA/GCE) with four folds current and much reduced potential on the modified electrode showed catalytic property of the modifier towards oxidation of AMX. While cyclic voltammetric studies of effect of scan rate showed predominantly diffusion controlled oxidation of AMX with one electron participation, effect of pH revealed participation of protons and electrons in a 1:1 ratio. The square wave voltammetric peak current response of the modified electrode for AMX showed linear dependence on the concentration of the spiked standard AMX in the range 10-150 µmol L-1 with 9.9 nmol L-1 LOD. The AMX content of the studied tablet brands were found in the range 97.84-100.78% of the labeled value. Spike recovery results of 99.6-100.5%, and interference recovery results of 95.4-100.8% AMX in the presence of 50-200% of ampicillin and cloxicillin validated the applicability of the method for determination of amoxicillin in tablet formulation. CONCLUSION: In contrast to the previously reported works on determination of amoxicillin, the present method showed an excellent performance making it a potential method for determination of amoxicillin in real samples including serum samples.

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Accurate determination of residual protein content in hydroxypropyl chitin (HPCH), a temperature-sensitive chitin derivative developed recently, is of great importance for biomedical applications. Coomassie brilliant blue (Bradford) method, Lowry method and Bicinchoninic acid (BCA) method were investigated to estimate the content of residual protein in HPCH. It was found that both Bradford and Lowry methods are not suitable for the protein assay in the HPCH sample. The BCA method could be used to determine protein content in HPCH solutions at low concentrations with good accuracy and precision and reasonable limit of detection and limit of quantitation for medical applications.

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Polyethyleneimine (PEI) is a flocculent that is widely used in the downstream purification of monoclonal antibodies. It is an in-process residual that is carried through the drug purification process and strongly inhibits residual DNA quantitation by real-time quantitative PCR assay. Very high sample dilutions (e.g., 1:10,000) can overcome the interference of PEI, but at the cost of DNA assay sensitivity. Diluting samples poses a significant risk to the assay sensitivity needed to satisfy regulatory requirements on the quantitation of residual genomic DNA present per dose (i.e., 10 ng/dose). Removing PEI while retaining DNA, by the use of sodium dodecyl sulfate, heparin and/or sarkosyl can overcome the interference of PEI and allow a more accurate quantitation of residual DNA.

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A selective and sensitive electrochemical method based on glassy carbon electrode modified with poly(malachite green) was developed for determination of tetracycline in pharmaceutical capsule formulation. Cyclic voltammetry and electrochemical impedance spectroscopy using [Fe(CN)6]3-/4- as a probe were used to characterize the potentiodynamiclly deposited poly(malachite green) on the surface of glassy carbon electrode. In contrast to the unmodified glassy carbon electrode, the fabricated poly(malachite green) modified glassy carbon electrode showed catalytic property towards two steps irreversible oxidation of tetracycline. Better correlation of the oxidative peak current with the scan rate than with the square root of scan rate supported by slope of 0.60 for log(current) versus log(scan rate) indicated that the oxidation reaction of tetracycline at the modified electrode was predominantly controlled by electron exchange step at the solution polymer interface. Under optimized solution pH, and accumulation parameters, the square wave adsorptive anodic striping peak current response of the modified electrode showed linear dependence on concentration of tetracycline in the range 5-100 µM with determination coefficient, method detection limit, and quantification limit of 0.99588, 1.6 µM, and 5.3 µM, respectively. The tetracycline content of a capsule sample claimed to have 250 mg/capsule was found to be 250.53 mg/capsule with 0.21% deviation. Excellent spike recovery result of 99.80%, and 98.49-99.78% recovery of tetracycline in capsule sample in the presence of 50-200% of UA, AA, and ampicillin validated the applicability of the method for determination of tetracycline in real samples with complex matrix like capsule formulations.

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INTRODUCTION: Chromogenic substrate assays (CSA) to measure Factor IX (FIX) have recently become commercially available. However, information on their performance characteristics and use in diagnostic haemostasis laboratories remains limited. AIM: To evaluate the Hyphen Biomed (Hyphen) and Rossix FIX CSAs on fully automated coagulation analysers and compare them to the FIX one-stage assay (OSA). This study was conducted in a tertiary referral haemostasis laboratory associated with a haemophilia treatment centre. METHODS: Automated CSA protocols were adapted to the Sysmex CS2500 (CS2500) and Diagnostica Stago STA-R (STA-R) analysers. Samples assayed were from healthy volunteers, haemophilia B patients and FIX deficient plasma spiked with either plasma derived, recombinant or extended half-life FIX products. RESULTS: Reference intervals for Hyphen and Rossix assays were 73 IU/dL to 164 IU/dL and 73 IU/dL to 168 IU/dL, respectively, on the CS2500 analyser; and 84 IU/dL to 165 IU/dL for the Rossix assay on the STA-R. Repeatability across all method/analyser combinations resulted in CVs ranging from 0.8% to 5.4%. Between run reproducibility gave CVs <6.7% for all method/analyser combinations. In spiked samples, FIX recoveries were mostly within an acceptable limit of 100 ± 25% for BeneFIX® , Rixubis® and Alprolix® with some differences between CSAs. CONCLUSION: Both commercial factor FIX CSA kits can be adapted for Stago and Sysmex automated coagulation analysers. Reagent cost and workflow practices will need to be considered. These assays are potentially more consistent than OSA in measurement of replacement FIX products in haemophilia B patients.

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A sorbent trap that utilizes activated carbon (AC) as the solid trapping medium is a new technology for measuring total mercury (Hg) emissions from combustion facilities. In this study, sorbent trap technology was further developed, improved and evaluated at the laboratory scale. AC was impregnated with 5% aqua regia to enhance its Hg adsorption capacity. Sorbent traps spiked with an Hg standard solution were found to be reproducibly prepared and highly stable. The effect of the Hg concentration on the spiking efficiency was further investigated. The adsorption of elemental and oxidized Hg by the sorbent trap was studied under various experimental conditions (temperature, flow rate and inlet Hg concentration). The Hg concentration of the flue gas effluent from the sorbent trap was measured. In addition, the concentration of Hg adsorbed on the AC was determined by digesting the used AC with an acid according to US EPA method 3052 and then analyzing it with cold vapor atomic absorption spectrometry. Furthermore, the gas-phase Hg emissions from a combustion source were measured using the sorbent trap according to US EPA method 30B. The results showed that the sorbent trap could be used for Hg concentrations between 10.0 and 40.0 µg m(-3) and flow rates between 0.5 and 1.0 lpm with adsorption efficiencies greater than 90%.

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Advances in viral detection technologies have the potential to increase the safety assurance of medicines produced in biological production systems. However, taking full advantage of these technological advances in the regulated testing environment will require protocols for standardization and performance testing. The most essential performance characteristics of detection methods for these applications include sensitivity, breadth of detection, and consistency. We have evaluated an approach to establishing the suitability of advanced nucleic-acid-based detection systems for characterization of cell substrates and production cultures. This approach is based on selecting relevant challenge viruses, their preparation and characterization, their application to a sample preparation workflow, and quantitation of their recovery by an independent means as well as the advanced detection readout. This approach helps us evaluate the suitability of the workflow for handling diverse sample matrices across manufacturing platforms for vaccines and other biological products, and also suggests a means by which technology users, developers, and regulators may consider the critical performance attributes of novel detection technologies. We have applied this workflow to a novel microarray-based viral detection system in collaboration with Lawrence Livermore National Laboratory. This system is appealing because of the rapid turnaround of results compared to some other advanced detection technologies.

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The reliable detection of nanoparticles (NPs) in fish tissue is required to support ecotoxicological research and food safety investigations. Therefore the current work aimed to develop a simple method to determine Ti from TiO2 NPs in fish tissue whilst simultaneously measuring other elements in the sample. Spike recovery tests showed no differences when digestion was conducted in glass or plastic vials, there was stirring or sonication of the samples, or when sodium dodecyl sulfate was added. However, the addition of 2% Triton X-100 and sonicating and then vortexing of samples immediately prior to analysis did improve recovery (approximately 20% to >90% in trout gill and muscle samples). Method precision and accuracy were good with coefficients of variation <7%. Copper spike recovery results showed that the method is also suitable for multi-element analysis in the same samples. This improved method is simple with high throughput and represents a marked improvement for routine determination Ti from TiO2 NPs in fish tissues.

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