Cost analysis of ELISA, solid-phase extraction, and solid-phase microextraction for the monitoring of pesticides in water

Nano-enabled sensing of per-/poly-fluoroalkyl substances (PFAS) from aqueous systems - A review

Per-/poly-fluoroalkyl substances (PFAS) are an emerging class of environmental contaminants used as an additive across various commodity and fire-retardant products, for their unique thermo-chemical stability, and to alter their surface properties towards selective liquid repellence. These properties also make PFAS highly persistent and mobile across various environmental compartments, leading to bioaccumulation, and causing acute ecotoxicity at all trophic levels particularly to human populations, thus increasing the need for monitoring at their repositories or usage sites. In this review, current nano-enabled methods towards PFAS sensing and its monitoring in wastewater are critically discussed and benchmarked against conventional detection methods. The discussion correlates the materials' properties to the sensitivity, responsiveness, and reproducibility of the sensing performance for nano-enabled sensors in currently explored electrochemical, spectrophotometric, colorimetric, optical, fluorometric, and biochemical with limits of detection of 1.02 × 10^-6 μg/L, 2.8 μg/L, 1 μg/L, 0.13 μg/L, 6.0 × 10^-5 μg/L, and 4.141 × 10^-7 μg/L respectively. The cost-effectiveness of sensing platforms plays an important role in the on-site analysis success and upscalability of nano-enabled sensors. Environmental monitoring of PFAS is a step closer to PFAS remediation. Electrochemical and biosensing methods have proven to be the most reliable tools for future PFAS sensing endeavors with very promising detection limits in an aqueous matrix, short detection times, and ease of fabrication.

A Quantification of Target Protein Biomarkers in Complex Media by Faradaic Shotgun Tagging

The progressive emergence of protein biomarkers promises a revolution in the healthcare industry and a shift of focus from disease management to much earlier intervention. Here, we introduce a facile shotgun tagging of ensemble proteins in clinically relevant media prior to specific target capture at antibody-modified electrodes. This facilitates a convenient voltammetric quantification of markers down to sub-pg/mL levels and across several orders of concentration. A translation of the methodology to an automated microfluidic platform enables marker quantification from 25 μL of sample in less than 15 min, demonstrated here with a simultaneous assaying of CRP and cardiac troponin I (cTnI). The assays show a good correlation with a standard immunoassay when applied to real patient serum samples. The platform is simple, generic, highly sensitive and requires no secondary labeling/binding or amplification.

Quantitation and speciation of residual protein within active pharmaceutical ingredients using image analysis with SDS-PAGE

Recent advances in biocatalysis and directed enzyme evolution has led to a variety of enzymatically-driven, elegant processes for active pharmaceutical ingredient (API) production. For biocatalytic processes, quantitation of any residual protein within a given API is of great importance to ensure process robustness and quality, pure pharmaceutical products. Typical analytical methods for analyzing residual enzymes within an API, such as enzyme-linked immunosorbent assays (ELISA), colorimetric assays, and liquid chromatographic techniques, are limited for determining only the concentration of known proteins and require harsh solvents with high API levels for analysis. For the first time, total residual protein content in a small molecule API was quantitated using image analysis applied to SDS-PAGE. Herein, a proposed methodology for residual protein detection, quantitation, and size-based speciation is presented, in which an orthogonal technique is offered to traditional analysis methods, such as ELISA. Results indicate that our application of the analytical methodology is able to reliably quantitate both protein standards and the total residual protein present within a final API, with good agreement as compared to traditional ELISA results. Further, speciation of the residual protein within the API provides key information concerning the individual residual proteins present, including their molecular weight, which can lead to improved process development efforts for residual protein rejection and control. This analytical methodology thus offers an alternative tool for easily identifying, quantitating, and speciating residual protein content in the presence of small molecule APIs, with potential for wide applicability across industry for biocatalytic or directed enzyme evolution efforts within process development.

Determination of CHLORPYRIFOS by GC/ECD in water and its sorption mechanism study in a RHODIC FERRALSOL

The validation of chromatographic methods is a costly process, however necessary, especially with regard to the validation of methods that accurately determine concentrations of pesticides in different environmental compartments. This research aimed at the development and validation of a simple and fast method for the determination of chlorpyrifos concentrations in water by means of a gas chromatograph with electron capture detection (GC/ECD), and to investigate chlorpyrifos dynamics of adsorption in a Rhodic Ferralsol in Southern Brazilian conditions. The developed chromatographic method was based in EPA 8141 method. Parameters to be checked for method validation were: Selectivity/specificity, linearity, precision, accuracy, robustness, limit of detection (LOD) and limit of quantitation (LOQ). Were employed the following methodologies for the validation process: ANVISA Resolution 899, DOQ-CGCRE-008 and FDA Bioanalytical Method Validation Guide. Also, through laboratory tests, the sorption dynamics of chlorpyrifos in Rhodic Ferralsol was evaluated. Thus, the soil was contaminated with increasing concentrations of chlorpyrifos, which were subjected to solid-liquid extraction with SPE cartridge Chromabond® C18 ec. The obtained results were submitted to the models of Langmuir, Freundlich, Dubinin-Radushkevich and Sips. By this method, chlorpyrifos peaks are obtained at 16.9 min, demonstrating practicality and low cost. This method exhibits precision and sensitivity, with satisfactory LQ and LQ values. The models of Langmuir, Freundlich, Dubinin-Radushkevich and Sips suggest the occurrence of simultaneous adsorption in mono and multilayer of chlorpyrifos in Rhodic Ferralsol colloids, as well as the predominance of a chemical, high energy binding process (irreversible). However, the chemisorption of chlorpyrifos is more related to the good fit found for Dubinin-Radushkevich sorption energy values (9.861 and 11.079 KJ mol^-1) and Q_m values estimated by Langmuir (485.55 and 389.61 μg g^-1 for linear and nonlinear model).

On chip preconcentration and fluorescence labeling of model proteins by use of monolithic columns: device fabrication, optimization, and automation

Microfluidic systems with monolithic columns have been developed for preconcentration and on-chip labeling of model proteins. Monoliths were prepared in microchannels by photopolymerization, and their properties were optimized by varying the composition and concentration of the monomers to improve flow and extraction. On-chip labeling of proteins was achieved by driving solutions through the monolith by use of voltage then incubating fluorescent dye with protein retained on the monolith. Subsequently, the labeled proteins were eluted, by applying voltages to reservoirs on the microdevice, and then detected, by monitoring laser-induced fluorescence. Monoliths prepared from octyl methacrylate combine the best protein retention with the possibility of separate elution of unattached fluorescent label with 50% acetonitrile. Finally, automated on-chip extraction and fluorescence labeling of a model protein were successfully demonstrated. This method involves facile sample pretreatment, and therefore has potential for production of integrated bioanalysis microchips.

The state of health economic research in South Africa: a systematic review

BACKGROUND

Economic factors are a limiting factor toward the implementation of many health programmes and interventions. Economic evaluation has a great potential to contribute toward cost-effective healthcare delivery in South Africa. Little is known about the characteristics and quality of health economic (including pharmacoeconomic) research in South Africa.

OBJECTIVE AND METHODS

This study assessed the state of health economic (including pharmacoeconomic) research in South Africa. PUBMED, MEDLINE, HealthSTAR, EconLit and PsycINFO databases were searched to identify health economic articles pertaining to South Africa published between 1 January 1977 and 30 April 2010. The searches used the following Medical Subject Headings (MeSH) terms and text words alone and in combination: 'costs', 'health' and 'South Africa'. Our study included only original economic studies/analyses that pertained to South Africa, addressed a health-related topic, and had a statement or word in the title, abstract or keywords that indicated that an economic (including cost) analysis had been conducted. The study only included complete peer-reviewed publications (e.g. abstracts were excluded) that were reported in the English language. Two reviewers independently scored each article in the final sample using the data collection form designed for the study.

RESULTS

In total, 108 studies investigating a wide variety of diseases were included in the study. These articles were published in 39 different journals mostly based outside of South Africa between 1977 and 2010. On average, each article was written by three authors. Most first authors had medical/clinical training and resided in South Africa at the time of publication of their study. Based on a 1-10 scale, with 10 indicating the highest quality, the mean quality score for all studies was 7.59 (SD 1.42) and half of the articles were of good quality (score 8-10) The quality of studies was related to the country in which the journal publishing the article was based (outside South Africa = higher); current residence of the primary author (outside South Africa = higher); method of economic analysis (economic evaluations higher than cost studies); type of data used (secondary higher than primary); primary training of the first author (health economics/pharmacoeconomics = higher); type of medical function (diagnosis = higher); study perspective (societal = higher); primary health intervention (pharmaceuticals = higher); study design (modelling = higher); number of authors (more = higher); and year of publication (more recent = higher) [p ≤ 0.05].

CONCLUSION

Half of the articles were of poor or fair quality. Measures are needed to promote the commissioning of more and better quality health economic and pharmacoeconomic studies in South Africa.

Sample preparation for chromatography: An African perspective

Africa as a continent has its unique challenges for analytical chemists in sample preparation for chromatographic analyses. The areas of agriculture, environment, food and health provide formidable challenges when it comes to method development, for example, drought can result in inadequate supplies of good quality water. The testing of water quality necessitates the development of assay methods that can be employed to not only determine the quantities of pesticides associated with malaria and tsetse fly eradication programmes, but also to monitor mycotoxins or neurotoxins. Urbanisation has also meant that endocrine disruptors such as phthalate esters need to be monitored. This review will profile some of the activities by analytical chemists practising in the African continent, who seek to address some of the challenges in sample preparation for chromatographic analyses.

Capillary microextraction for simultaneous analysis of multi-residual semivolatile organic compounds in water

Capillary microextractor (CME) in combination with a gas chromatograph-mass spectrometer (GC-MS) was employed for the determination of trace priority hazardous substances in water. Three groups of semivolatile organic compounds (SVOCs), i.e., chlorinated hydrocarbons, pesticides and polycyclic aromatic hydrocarbons (PAHs), were simultaneously determined. SVOCs were extracted from 7 mL of water samples on a 100 cm commercial gas chromatographic column (0.32 mm id x film thickness 0.25 microm, HP-5 capillary column) and eluted with only 3 microL of acetonitrile. The extractant was analyzed by GC-MS in the selected ion monitoring mode. The method showed good linearity over the concentration range 10 ng L(-1) to 3.0 mg L(-1) with correlation coefficients (r) greater than 0.99 and low limits of detection ranged from 10 ng L(-1) to 1.0 mg L(-1). High recovery (more than 80%) was obtained with relative standard deviation less than 10%. The method was successfully applied for trace level analyses of SVOCs in water samples.

Determination of frequently detected herbicides in water by solid-phase microextraction and gas chromatography coupled to ion-trap tandem mass spectrometry

A method based on solid-phase microextraction (SPME) coupled with GC and ion trap tandem mass spectrometry has been developed for the analysis of nine herbicides and degradation products, among the most frequently found in natural water. A polydimethylsiloxane-divinylbenzene (PDMS-DVB)-coated fiber was selected to extract the analytes directly from the samples over the 0.01-1 microg L(-1) concentration range. Optimization of manual and automated SPME was performed on the basis of desorbed amounts, via various factorial experiment designs. Of the two modes, the automated one was found to be the most efficient. Memory effect was avoided owing to the 10-min fiber desorption time. Limits of detection reached down to below 0.01 microg L(-1) and repeatability ranged from 3 to 15% in natural water. A validation study was conducted involving the quantitation of the target compounds in Seine water with SPME/GC-MS-MS external calibration.

Comparison between conventional indirect competitive enzyme-linked immunosorbent assay (icELISA) and simplified icELISA for small molecules

A simplified indirect competitive enzyme-linked immunosorbent assay (icELISA) for small molecules was established by modifying the procedure of conventional icELISA. The key change was that the analyte, antibody, and enzyme-labeled second antibody in the simplified icELISA were added in one step, whereas in conventional icELISA these reagents were added in two separate steps. Three small chemicals, namely zeatin riboside, glycyrrhetinic acid, and chlorimuron-ethyl, were used to verify the new assay format and compare the results obtained from conventional icELISA and simplified icELISA. The results indicated that, under optimized conditions, the new assay offered several advantages over the conventional icELISA, which are simpler, less time consuming and higher sensitive although it requires more amount of reagents. The assay sensitivity (IC50) was improved for 1.2-1.4-fold. Four licorice roots samples were analyzed by conventional icELISA and simplified icELISA, as well as liquid chromatography (LC). There was no significant difference among the content obtained from the three methods for each sample. The correlation between data obtained from conventional icELISA and simplified icELISA analyses was 0.9888. The results suggest that the simplified icELISA be useful for high throughput screening of small molecules.