Production of certified reference materials - homogeneity and stability study based on the determination of total mercury and methylmercury

Development of Human Rhinovirus RNA Reference Material Using Digital PCR

The human rhinovirus (RV) is a positive-stranded RNA virus that causes respiratory tract diseases affecting both the upper and lower halves of the respiratory system. RV enhances its replication by concentrating RNA synthesis within a modified host membrane in an intracellular compartment. RV infections often occur alongside infections caused by other respiratory viruses, and the RV virus may remain asymptomatic for extended periods. Alongside qualitative detection, it is essential to accurately quantify RV RNA from clinical samples to explore the relationships between RV viral load, infections caused by the virus, and the resulting symptoms observed in patients. A reference material (RM) is required for quality evaluation, the performance evaluation of molecular diagnostic products, and evaluation of antiviral agents in the laboratory. The preparation process for the RM involves creating an RV RNA mixture by combining RV viral RNA with RNA storage solution and matrix. The resulting RV RNA mixture is scaled up to a volume of 25 mL, then dispensed at 100 µL per vial and stored at -80 °C. The process of measuring the stability and homogeneity of RV RMs was conducted by employing reverse transcription droplet digital polymerase chain reaction (RT-ddPCR). Digital PCR is useful for the analysis of standards and can help to improve measurement compatibility: it represents the equivalence of a series of outcomes for reference materials and samples being analyzed when a few measurement procedures are employed, enabling objective comparisons between quantitative findings obtained through various experiments. The number of copies value represents a measured result of approximately 1.6 × 105 copies/μL. The RM has about an 11% bottle-to-bottle homogeneity and shows stable results for 1 week at temperatures of 4 °C and -20 °C and for 12 months at a temperature of -80 °C. The developed RM can enhance the dependability of RV molecular tests by providing a precise reference value for the absolute copy number of a viral target gene. Additionally, it can serve as a reference for diverse studies.

Choice experiment to assess consumer attributes for a pharmaceutical product

Purpose

This study aims to identify the appropriate combination of attributes that must be present to deliver value in a new product for a pharmaceutical enterprise.

Design/methodology/approach

The application object was the Metronidazole analytical standard, using choice experiments to product attributes and price.

Findings

The practical results indicate that consumer value anticipation allows entry into the market with higher competitiveness.

Originality/value

Conceptually, it uses a value delivery approach, generally applied to large companies, in a case aimed at enterprises. In practice, for the enterprise studied, the value anticipation by the consumer allows entry into the market with higher competitiveness.

A novel simultaneous isotope dilution strategy as a powerful tool in the two-track certification process of trace metal mass fractions: a case study of mercury, cadmium and lead in soil and sediment materials

An analytical methodology based on isotope dilution (ID) principles was developed to establish the reference procedure for the simultaneous assignation of aqua regia extractable and total mass fractions of Hg, Cd, and Pb in soil and sediment matrix samples. The 'twin sample-spike blends' were prepared under close to the exact matching conditions, resulting in almost identical mass ratios of the spike to the sample in the blends, which followed either the aqua regia extraction method or total digestion procedure. The isotope ratios in 'twin-blends' were measured by inductively coupled plasma mass spectrometry (ICP-MS). The two-track IDMS strategy proposed in this work was successfully applied to three certified reference materials (CRMs): ERM-CC141 loam soil, EnvCRM 03 soil, and MODAS-2 bottom sediment. This ensured an adequate method validation. For two CRMs (EnvCRM 03 and MODAS-2) it was found that the isotope ratio values in 'twin-blends' for Hg, Cd, and Pb were almost identical with a variability of less than 2.4%. This confirmed that there is no measurable difference between the aqua regia extractable and the total mass fractions within the uncertainty ranges. Therefore, aqua regia mass fractions assigned in this study were found to be equal to certified element contents. For ERM-CC141 loam soil, the Hg isotope ratio values measured in the 'twin-blends' were found to be identical within their measurement uncertainties, and thus, it was concluded that the aqua regia extractable Hg content is identical to the total Hg content. However, in the case of Cd and Pb isotope ratio values in 'twin-blends' varied around 24% or 16%, respectively and because this significant difference was noticed, for both elements it is necessary to calculate the aqua regia content and the total content separately. Because this significant difference was noticed for both elements, it is necessary to calculate the aqua regia content and the total content separately. A detailed comparison of the isotope ratio values between the 'twin-blends' provided unambiguous information about aqua regia extractability of metals and it is a strong indicator for making decisions related to the assignment of either a single mass fraction valid for both procedures or two separate element mass fraction values. To our knowledge and based on the relevant literature survey, this is a novel strategy based on IDMS, and such studies have not been undertaken and presented so far.

Assignation of inorganic mercury and methylmercury mass fractions in a soil matrix certified reference material by two analytical methodologies based on species-specific isotope dilution mass spectrometry and chromatographic separation

Assignment of inorganic mercury and methyl mercury mass fractions at an ultra-trace level in soil certified reference material EnvCRM 03 with a complex matrix composition was undertaken. Inorganic mercury and methyl mercury contents by species-specific isotope dilution inductively coupled plasma MS with on-line HPLC or with classical off-line chromatography were established. Different extraction protocols: sequential extraction ((1) H₂ SO₄ /KBr/CuSO₄ ; (2) dichloromethane; (3) Na₂ S₂ O₃ ) or one-step extraction (diluted HCl) in solid-liquid systems were verified. Sequential extraction allowed quantification and separation of inorganic mercury and methyl mercury on HPLC column in one chromatographic run and were found to be (316 ± 10) μg kg^-1 (U = 3.2%, k = 2) and (0.53 ± 0.02) μg kg^-1 (U = 3.8%, k = 2), respectively. Extraction by diluted HCl and application of classical off-line chromatography led to the separation of methyl mercury from predominant inorganic mercury form and was found to be (0.54 ± 0.03) μg kg^-1 (U = 5.4%, k = 2). To the best-obtained literature knowledge, there was no available soil material aimed for speciation analysis of inorganic mercury and methyl mercury so far. Both developed analytical methodologies were found to be equally sensitive and could be successfully applied for mercury species determination in samples with the complex matrix. This article is protected by copyright. All rights reserved.

Flexible and integrated dual carbon sensor for multiplexed detection of nonylphenol and paroxetine in tap water samples

Multiplex detection of emerging pollutants is essential to improve quality control of water treatment plants, which requires portable systems capable of real-time monitoring. In this paper we describe a flexible, dual electrochemical sensing device that detects nonylphenol and paroxetine in tap water samples. The platform contains two voltammetric sensors, with different working electrodes that were either pretreated or functionalized. Each working electrode was judiciously tailored to cover the concentration range of interest for nonylphenol and paroxetine, and square wave voltammetry was used for detection. An electrochemical pretreatment with sulfuric acid on the printed electrode enabled a selective detection of nonylphenol in 1.0-10 × 10^-6 mol L^-1 range with a limit of detection of 8.0 × 10^-7 mol L^-1. Paroxetine was detected in the same range with a limit of detection of 6.7 × 10^-7 mol L^-1 using the printed electrode coated with a layer of carbon spherical shells. Simultaneous detection of the two analytes was achieved in tap water samples within 1 min, with no fouling and no interference effects. The long-term monitoring capability of the dual sensor was demonstrated in phosphate buffer for 45 days. This performance is statistically equivalent to that of high-performance liquid chromatography (HPLC) for water analysis. The dual-sensor platform is generic and may be extended to other water pollutants and clinical biomarkers in real-time monitoring of the environment and health conditions. Silver pseudo-reference electrodes for paroxetine (REP) and nonylphenol (REN), working electrodes for paroxetine (WP) and nonylphenol (WN), and auxiliary electrode (AE). USP refers to the University of Sao Paulo. "Red" is reduced form and "Oxi" is oxidized form of analytes.