Colourimetric Tests Research Articles

Clinical laboratory techniques for detecting drugs of abuse: Feasibility in developing nations

Drugs of abuse are prescription, over-the-counter, or other forms of drugs that are often used for purposes other than those for which they are meant to be used, or in excessive amounts. The abuse of illicit drugs (for example cocaine, heroin, and codeine) poses a serious threat to public health, not to mention a great challenge to the health care system. It is important to review the techniques used in detecting these drugs of abuse to stay ahead of this growing global drug problem. This review aims to give an overview of known clinical laboratory techniques used in detecting some common drugs of abuse that could serve as an integral part of determining the presence of these drugs in bodily fluids and samples. Relevant literature was reviewed in various search engines (Google Scholar, PubMed, ScienceDirect, Bing). Findings showed that some of the current clinical laboratory techniques for detecting and quantifying drugs of abuse include Microcrystalline tests, thin-layer chromatography, colourimetric tests, immunoassays, urine dipstick tests, and ultraviolet spectroscopy. Apart from these known techniques, new and emerging techniques are being validated to serve as additions to these already existing techniques and be used in clinical settings. In conclusion, the burden of drug abuse is on the rise and becoming a public health concern. There should be an ever-increasing interest in developing new analytical methodologies not only to detect but also to quantify drugs of abuse which may be applied in a plethora of areas including clinical settings.Some of the outlined techniques are highly priced and for cost ineffectiveness, they may be difficult to afford and sustain in resource-restraint settings like developing nations. Hence, grants and laboratory infrastructural support may be needed from international donor agencies.

Model compounds for evaluating the reactivity of amphetamine-type stimulants

The use of controlled precursors for reaction optimisation is not always practical. One approach to limiting the use of controlled substances is to instead use ‘model compounds’. Herein, two model compounds resembling norephedrine and ephedrine were selected based on their (i) structural similarity (i.e., presence of key functional groups) and (ii) availability from multiple suppliers without restriction. Model compounds 2-amino-1-phenylethanol and 2-(methylamino)-1-phenylethanol (halostachine), were compared to norephedrine and pseudoephedrine by firstly subjecting them to transformations known in the synthesis of amphetamines, and secondly, comparing the compounds using colourimetric spot tests, FTIR and NMR.

The relationship between peripheral immune response and disease severity in SARS-CoV-2-infected subjects: A cross-sectional study.

Coronavirus disease 2019 (COVID‐19) is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and marked by an intense inflammatory response and immune dysregulation in the most severe cases. In order to better clarify the relationship between peripheral immune system changes and the severity of COVID‐19, this study aimed to evaluate the frequencies and absolute numbers of peripheral subsets of neutrophils, monocytes, and dendritic cells (DCs), in addition to quantifying the levels of inflammatory mediators. One hundred fifty‐seven COVID‐19 patients were stratified into mild, moderate, severe, and critical disease categories. The cellular components and circulating cytokines were assessed by flow cytometry. Nitric oxide (NOx) and myeloperoxidase (MPO) levels were measured by colourimetric tests. COVID‐19 patients presented neutrophilia, with signs of emergency myelopoiesis. Alterations in the monocytic component were observed in patients with moderate to critical illness, with an increase in classical monocytes and a reduction in nonclassical monocytes, in addition to a reduction in the expression of HLA‐DR in all subtypes of monocytes, indicating immunosuppression. DCs, especially plasmacytoid DCs, also showed a large reduction in moderate to critical patients. COVID‐19 patients showed an increase in MPO, interleukin (IL)‐12, IL‐6, IL‐10, and IL‐8, accompanied by a reduction in IL‐17A and NOx. IL‐10 levels ≥14 pg/ml were strongly related to the worst outcome, with a sensitivity of 78·3% and a specificity of 79·1%. The results of this study indicate the presence of systemic effects induced by COVID‐19, which appear to be related to the pathophysiology of the disease, highlighting the potential of IL‐10 as a possible prognostic biomarker for COVID‐19.

Digital Sublimation Printing on Knitted Polyamide 6.6 Fabric Treated with Non-Thermal Plasma.

The garment industry demands stamping processes that are increasingly more agile and less damaging to the environment. In this scenario, digital printing, with the sublimation transfer printing technique, presents itself as a viable option for synthetic textile substrates. Among the synthetic fibres, polyamide (P.A.) fibres stand out, as they are light, soft, durable, and boast moderate sweat absorption; however, before sublimation, superficial treatment is necessary in order to present good results such as withstanding washing and maintaining colour intensity. This study addresses the surface modification of the PA6.6 textile substrate by activating non-thermal plasma at atmospheric pressure to receive dye through the sublimation method with dispersed dye. The knitted PA6.6 fabric surface treatment was performed with plasma application at atmospheric pressure using air in the Plasmatreater AS400 equipment. The sublimation transfer effects were evaluated by wash fastness and colourimetric tests. To assess the wettability effect of the control and treated samples, a contact angle test was carried out on PA6.6 samples. Fourier transform infrared spectroscopy (FTIR) proved the changes in chemical functional groups in the fibres. The results showed a decrease in the contact angle of the textile surface, 4–5 grayscale results for colour change and transfer for washing, and an increase in colour strength. In the FTIR tests, there is an increase in the transmittance value of aromatic, carboxylic groups (C=O, 580 cm−1), amides (N=H, 1630 cm−1), and methyl groups (CH 1369 to 1463 cm−1) as well as the presence of new functional groups in the 3064 cm−1 and 2860 cm−1 bands. These conditions allowed sublimation in the knitted PA6.6 fabric and showed increased colour strength and good wash fastness.

Intelligent image-based colourimetric tests using machine learning framework for lateral flow assays

This paper aims to deliberately examine the scope of an intelligent colourimetric test that fulfils ASSURED criteria (Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free, and Deliverable) and demonstrate the claim as well. This paper presents an investigation into an intelligent image-based system to perform automatic paper-based colourimetric tests in real-time to provide a proof-of-concept for a dry-chemical based or microfluidic, stable and semi-quantitative assay using a larger dataset with diverse conditions. The universal pH indicator papers were utilised as a case study. Unlike the works done in the literature, this work performs multiclass colourimetric tests using histogram-based image processing and machine learning algorithm without any user intervention. The proposed image processing framework is based on colour channel separation, global thresholding, morphological operation and object detection. We have also deployed aserver-based convolutional neural network framework for image classification using inductive transfer learning on a mobile platform. The results obtained by both traditional machine learning and pre-trained model-based deep learning were critically analysed with the set evaluation criteria (ASSURED criteria). The features were optimised using univariate analysis and exploratory data analysis to improve the performance. The image processing algorithm showed >98% accuracy while the classification accuracy by Least Squares Support Vector Machine (LS-SVM) was 100%. On the other hand, the deep learning technique provided >86% accuracy, which could be further improved with a large amount of data. The k-fold cross-validated LS-SVM based final system, examined on different datasets, confirmed the robustness and reliability of the presented approach, which was further validated using statistical analysis. The understaffed and resource-limited healthcare system can benefit from such an easy-to-use technology to support remote aid workers, assist in elderly care and promote personalised healthcare by eliminating the subjectivity of interpretation.

Cellulose Acetate Nanofibres Containing Alizarin as a Halochromic Sensor for the Qualitative Assessment of Rainbow Trout Fish Spoilage

A halochromic sensor of cellulose acetate nanofibres and alizarin as a fish spoilage indicator in real time is described. The colour of this on-packaging sensor changes visually with an increase in the amount of total volatile basic nitrogen (TVB-N) and a rise in the pH value of product. Rainbow trout fillets were kept at refrigerator temperature (4 °C) for 12 days. TVB-N, pH, total viable count (TVC) and colourimetric tests were performed. Results showed that the pH, the TVB-N and the TVC increased with time. No colour changes were observed within 48 h, but after the fourth day, a very light brick colour on the nanosensor was observed. This colour became darker on the sixth day, representing actual pH changes. The colour of sensor tended towards violet on the 12th day; the colourimetric result proved the expected visual colour change in the electrospun nanosensor due to alizarin usage as a halochromic dye.

Colour quantitation for chemical spot tests for a controlled substances presumptive test database.

Crime scene investigators (CSIs) often encounter unknown powders, capsules, tablets, and liquids at crime scenes, many of which are controlled substances. Because most drugs are white powders, however, visual determination of the chemical identity is difficult. Colourimetric tests are a well-established method of presumptive drug identification. Positive tests are often reported differently, however, because two analysts may perceive colour or record colourimetric results in different ways. In addition to perceiving colour differently, it is very common for there to be poor visibility conditions (e.g. rain, darkness) while performing these tests, further obscuring the results. In order to address these concerns and to create uniformity in the reporting of on-site colourimetric test results, this study has evaluated two of the state-of-the-art apps (ColorAssist® and Colorimeter®) for reporting the colour test results quantitatively in red-green-blue (RGB) format. The compiled library database of presumptive test results contains over 3300 data points including over 800 unique drug/test combinations. Variations observed between test replicates, from performing a test on different days, recording with a different device type (e.g. iPod Touch, iPhone models 4, 5c, 5s, or 6), and using different quantities of drug are discussed. Overall, the least variation in Euclidian norm was observed using ColorAssist® with the camera light (25.1±22.1) while the variation between replicates and data recorded using different devices was similar. The resulting library is uploaded to a smartphone application aimed to aid in identifying and interpreting suspected controlled substance evidence. Copyright © 2016 John Wiley & Sons, Ltd.

Hop proanthocyanidins for the fining of beer

Fining agents are used in the clarification of beers; they help to reduce the time required to sediment suspended yeast cells and ensure the clarity and colloidal stability of beer. Following an adventitious observation during dry-hopping experiments, we identified a fining activity associated with Saaz hops. Extracts of hop cones were subsequently shown to have the capacity to flocculate yeast and result in their sedimentation. This activity has since been identified in extracts of many different hop varieties and, significantly in spent hops, the co-product resulting from commercial extraction of hops with either CO2 or ethanol. Here we illustrate the activity of the novel finings extracted from spent hops following CO2 extraction of Galena hops. The sediments formed on fining were compact, relative to those obtained when commercial isinglass was used to fine the same beers. The hop extracts were also effective in reducing 90° haze in beers under conditions designed to mimic both cask ale (12 °C) and lager (4 °C) type applications. The compounds responsible for the fining activity appear to be large (30–100 kDa, or more) polyphenols. Analysis of the polyphenols using colourimetric tests indicated the presence of proanthocyanidins. On acidic hydrolysis these generated cyanidin, which would be derived from a polymer composed of catechin and epicatechin subunits. The presence of these materials in spent hops offers the possibility to develop commercial products, with desirable fining properties, from an existing co-product stream. Furthermore, the finings are derived from a traditional ingredient of the brewing process.

Overestimation of geogenic arsenic in landfill leachate: interference of humic and phosphinic acid in a commercial test kit

Large-scale groundwater contamination by arsenic (As) requires economical yet reliable analytical procedures to monitor the quality of well water and the effluent of As elimination processes. The silver diethyldithiocarbamate (AgDDTC) method provides the basis of a series of colourimetric tests used as a compromise between semi-quantitative field-test kits and expensive instrumental analytics. This study aimed at understanding the significant As overestimation by the AgDDTC method observed in landfill leachate samples. Results of the AgDDTC test were up to threefold the levels obtained by reference analyses. Overestimation broadly agreed with the time course of chemical oxygen demand and total phosphorus in the leachate. We hypothesised that the interference was caused by reduced P species or humic acid (HA), respectively. To test this, As-AgDDTC determinations from As standards were conducted with phosphonic (H3PO3) and phosphinic acid (H3PO2) as well as two commercial HA as matrix components. While H3PO3 showed no effect, H3PO2 in concentrations of 0.06 to 28 mg P L−1 yielded As recoveries of up to 130%. This was probably due to the evolution of phosphine (PH3) as suggested by the absorption spectra recorded after reacting pure PH3 with AgDDTC in pyridine. The HA in concentrations of 0.6–320 mg dissolved organic carbon L−1 gave As recoveries of up to 600%, possibly due to a chromophoric reaction of volatile HA digestion products formed during the reduction step. Significant As overestimation in the presence of the above-named compounds may require pre-oxidation of the samples. To recognise interference effects, the acquisition of full absorbance spectra may be recommendable in lieu of fixed wavelength analyses.

Microwave assisted retting – A novel method of processing of flax stems

A new method for retting of flax stem was introduced by using microwave energy. The combined effect of pre-soaking, microwave volumetric heating and the non-thermal effect of microwave energy were applied in the retting of flax stem. Effective retting was observed in various combinations of pre-soaking, Microwave treatment times and microwave energy. The samples soaked for 24 and 36 h with microwave treatments of 20 min showed better retting efficiency. Fried tests, Near Infrared analysis and fibre diameter analysis were done to find out the retting efficiency. The effect of non-thermal effect of microwave in flax retting was proved experimentally. Colourimetric tests and tensile strength tests were conducted to compare the quality of fibres after microwave retting and no significant changes in the physical qualities were observed. The water released after pre-soaking was not contaminated because of less microbial activity in short duration of the entire process. In industrial point of view, this method is acceptable because of the ease of recyclability of the pre-soaked water and comparably short duration of the process.

Rapid quantitative colourimetric tests for trinitrotoluene (TNT) in soil

A rapid quantitative colourimetric test was developed for the determination of 2,4,6-Trinitrotoluene (TNT) in soil. Quantification was achieved using an innovative application of photography where the relationship between the Red Green Blue (RGB) value and concentration of colorimetric product was exploited. The wide linear range (1–50mg/L) and low detection limit (0.73±0.01mg/L to 3.5±0.4mg/L) achieved was comparable with spectrophotometric quantification methods. Quantification was validated both with known concentration standards and spiked soil extracts confirming the accuracy of the technique. The results demonstrate a powerful technique with the capacity for development as a rapid on site field test for the analysis of explosives.

Digital image‐based colourimetric tests for amphetamine and methylamphetamine

Digital image analysis was applied to the products of simple colorimetric [corrected] tests for amphetamine and methylamphetamine. Adobe Photoshop software was used for colour analysis to obtain analytical data in the form of a Red Green Blue (RGB) value. Calibration curves were developed for each compound and a number of illicit amphetamine samples were analyzed to demonstrate the application of the technique. A wide linear range and low detection limit for both drugs under test facilitated the application to illicit samples. Good agreement with gas chromatographic quantification results was obtained for the illicit samples analyzed by this method. The results show great potential for use as a semi-quantitative field test for illicit drug compounds.

Field indicator of chloride penetration depth

Chloride-induced corrosion of steel reinforcement is causing serious damage to many concrete structures. A number of methods to evaluate the chloride penetration into concrete have been developed. The most common practice in measuring the chloride profile is very time consuming. A simple colourimetric method of measuring the depth of chloride penetration into concrete by spraying a 0.1-N AgNO 3 solution is very attractive. But some questions have been raised about its sensitivity. In this article, the results from colourimetric tests and the corresponding quantity of chloride detected at the colour-change boundary, determined for more than 70 concrete samples, are given. The magnitude and variation of chloride concentrations are compared with those reported in the literature and evaluated in relation to typical chloride threshold values. In addition, a relationship between the colourimetric penetration depth and the charge passed during testing to ASTM C1202 is shown.