Optical Monitoring of Microplastics Filtrated from Wastewater Sludge and Suspended in Ethanol.

The abundance of microplastics (MPs) in the atmosphere, on land, and especially in water bodies is well acknowledged. In this study, we establish an optical method based on three different techniques, namely, specular reflection to probe the medium, transmission spectroscopy measurements for the detection and identification, and a speckle pattern for monitoring the sedimentation of MPs filtrated from wastewater sludge and suspended in ethanol. We used first Raman measurements to estimate the presence and types of different MPs in wastewater sludge samples.

Towards the Development of Portable and In Situ Optical Devices for Detection of Micro and Nanoplastics in Water: A Review on the Current Status.

The prevalent nature of micro and nanoplastics (MP/NPs) on environmental pollution and health-related issues has led to the development of various methods, usually based on Fourier-transform infrared (FTIR) and Raman spectroscopies, for their detection. Unfortunately, most of the developed techniques are laboratory-based with little focus on in situ detection of MPs. In this review, we aim to give an up-to-date report on the different optical measurement methods that have been exploited in the screening of MPs isolated from their natural environments, such as water.

Simultaneous investigation of the liquid transport and swelling performance during tablet disintegration.

Fast disintegrating tablets have commonly been used for fast oral drug delivery to patients with swallowing difficulties. The different characteristics of the pore structure of such formulations influence the liquid transport through the tablet and hence affect the disintegration time and the release of the drug in the body. In this work, terahertz time-domain spectroscopy and terahertz pulsed imaging were used as promising analytical techniques to quantitatively analyse the impact of the structural properties on the liquid uptake and swelling rates upon contact with the dissolution medium.

On optical sensing of surface roughness of flat and curved microplastics in water.

The growth of microplastic (MP) pollution is of increasing concern and represents a global challenge. In situ detection of these small particles is difficult because of their sizes, shapes, transparency or translucency, surface texture and ambient conditions. We propose and demonstrate the use of a prototype optical sensor to detect flat, nearly flat, curved and rough MPs prepared from commercial polyethylene terephthalate (PET) plastics and PET bottles in water.

Optical screening for presence of banned Sudan III and Sudan IV dyes in edible palm oils.

Due to the proven carcinogenicity of Sudan III and IV dyes, they are considered global public health issues. They are banned in all forms as food colourants. We propose the monitoring of simple and easy-to-measure optical properties of palm oils, such as the refractive indices and spectrophotometric properties, as efficient indicators to detect adulteration.

Optical transmission spectra study in visible and near-infrared spectral range for identification of rough transparent plastics in aquatic environments.

Erosion of microplastics due to residence time in aquatic environments causes roughening of the microplastic. Unfortunately, currently used measurement methods do not provide information on the surface roughness of the microplastic embedded in water. In this study we propose a novel method by using transmittance to get information on the magnitude of the surface roughness of microplastics and to rank microplastics by thickness.

A prototype of a portable optical sensor for the detection of transparent and translucent microplastics in freshwater.

Microplastic pollution in water bodies is an alarming problem which needs to be addressed. However, issues such as size, shape and their appearance to light (transparent or translucent) make it difficult to be optically detected. Here, a feasibility study of a portable prototype optical sensor with the capability of measuring simultaneously specular laser light reflection and transmission from microplastic particles is presented.

Outlook on optical identification of micro- and nanoplastics in aquatic environments.

Plastic pollution in natural water bodies is an emerging problem that requires quick actions. Recently, the role of micro- and nanoplastics in pollution and health issues has been realized and taken seriously. In this paper, we have studied optical properties, such as NIR spectra and refractive index, of some common plastic materials and present a method and data to screen especially problematic transparent plastics with rough surface in aquatic environments.

Hand-Held Refractometer-Based Measurement and Excess Permittivity Analysis Method for Detection of Diesel Oils Adulterated by Kerosene in Field Conditions.

Adulteration of fuels is a major problem, especially in developing and third world countries. One such case is the adulteration of diesel oil by kerosene. This problem contributes to air pollution, which leads to other far-reaching adverse effects, such as climate change.

Wavelength-dependent excess permittivity as indicator of kerosene in diesel oil.

Adulteration of diesel oil by kerosene is a serious problem because of air pollution resulting from car exhaust gases. The objective of this study was to develop a relatively simple optical measurement and data analysis method to screen low-adulterated diesel oils. For this purpose, we introduce the utilization of refractive index measurement with a refractometer, scanning of visible-near-infrared transmittance, transmittance data inversion using the singly subtractive Kramers-Kronig relation, and exploitation of so-called wavelength-dependent relative excess permittivity.

Investigating elastic relaxation effects on the optical properties of functionalised calcium carbonate compacts using optics-based Heckel analysis.

Heckel analysis is a widely used method for the characterisation of the compression behaviour of pharmaceutical samples during the preparation of solid dosage formulations. The present study introduces an optical version of the Heckel equation that is based on a combination of the conventional Heckel equation together with the linear relationship defined between the effective terahertz (THz) refractive index and the porosity of pharmaceutical tablets. The proposed optical Heckel equation allows us to, firstly, calculate the zero-porosity refractive index, and, secondly, predict the in-die development of the effective refractive index as a function of the compressive pressure during tablet compression.

Characterisation of pore structures of pharmaceutical tablets: A review.

Traditionally, the development of a new solid dosage form is formulation-driven and less focus is put on the design of a specific microstructure for the drug delivery system. However, the compaction process particularly impacts the microstructure, or more precisely, the pore architecture in a pharmaceutical tablet. Besides the formulation, the pore structure is a major contributor to the overall performance of oral solid dosage forms as it directly affects the liquid uptake rate, which is the very first step of the dissolution process.

Fast and non-destructive pore structure analysis using terahertz time-domain spectroscopy.

Pharmaceutical tablets are typically manufactured by the uni-axial compaction of powder that is confined radially by a rigid die. The directional nature of the compaction process yields not only anisotropic mechanical properties (e.g.

On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC as sole excipient.

The physical properties and mechanical integrity of pharmaceutical tablets are of major importance when loading with active pharmaceutical ingredient(s) (API) in order to ensure ease of processing, control of dosage and stability during transportation and handling prior to patient consumption. The interaction between API and excipient, acting as functional extender and binder, however, is little understood in this context. The API indomethacin is combined in this study with microcrystalline cellulose (MCC) at increasing loading levels.

Optics-based compressibility parameter for pharmaceutical tablets obtained with the aid of the terahertz refractive index.

The objective of this study is to propose a novel optical compressibility parameter for porous pharmaceutical tablets. This parameter is defined with the aid of the effective refractive index of a tablet that is obtained from non-destructive and contactless terahertz (THz) time-delay transmission measurement. The optical compressibility parameter of two training sets of pharmaceutical tablets with a priori known porosity and mass fraction of a drug was investigated.

Reflectometric monitoring of the dissolution process of thin polymeric films.

Pharmaceutical thin films are versatile drug-delivery platforms i.e. allowing transdermal, oral, sublingual and buccal administration.

Characterization of the Pore Structure of Functionalized Calcium Carbonate Tablets by Terahertz Time-Domain Spectroscopy and X-Ray Computed Microtomography.

Novel excipients are entering the market to enhance the bioavailability of drug particles by having a high porosity and, thus, providing a rapid liquid uptake and disintegration to accelerate subsequent drug dissolution. One example of such a novel excipient is functionalized calcium carbonate, which enables the manufacture of compacts with a bimodal pore size distribution consisting of larger interparticle and fine intraparticle pores. Five sets of functionalized calcium carbonate tablets with a target porosity of 45%-65% were prepared in 5% steps and characterized using terahertz time-domain spectroscopy and X-ray computed microtomography.

On the Immersion Liquid Evaporation Method Based on the Dynamic Sweep of Magnitude of the Refractive Index of a Binary Liquid Mixture: A Case Study on Determining Mineral Particle Light Dispersion.

This is a feasibility study of a modified immersion liquid technique for determining the refractive index of micro-sized particles. The practical challenge of the traditional liquid immersion method is to find or produce a suitable host liquid whose refractive index equals that of a solid particle. Usually, the immersion liquid method uses a set of immersion liquids with different refractive indices or continuously mixes two liquids with different refractive indices, e.

Noninvasive porosity measurement of biconvex tablets using terahertz pulses.

Biconvex pharmaceutical microcrystalline cellulose (MCC) compacts were investigated by the detection of terahertz (THz) pulse delay in the transmission measurement mode. The dimensions of the tablets were kept as constants but the porosity was a priori known variable. It is shown that the porosity of the biconvex compact has a linear correlation with the THz pulse delay.

Terahertz study on porosity and mass fraction of active pharmaceutical ingredient of pharmaceutical tablets.

In this study, terahertz time-domain spectroscopic (THz-TDS) technique has been used to ascertain the change in the optical properties, as a function of changing porosity and mass fraction of active pharmaceutical ingredient (API), of training sets of pharmaceutical tablets. Four training sets of pharmaceutical tablets were compressed with microcrystalline cellulose (MCC) excipient and indomethacin API by varying either the porosity, height, and API mass fraction or all three tablet parameters. It was observed, as far as we know, for the first time, that the THz time-domain and frequency-domain effective refractive index, as well as, the frequency-domain effective absorption coefficient both show linear correlations with the porosity and API mass fraction for training sets of real pharmaceutical tablets.

A structure parameter for porous pharmaceutical tablets obtained with the aid of Wiener bounds for effective permittivity and terahertz time-delay measurement.

A structure parameter that can be used to predict the pattern of arrangement of porous inclusions in pharmaceutical tablets is introduced. By utilizing the effective refractive index of a pharmaceutical tablet obtained from terahertz time-domain measurements, we have shown that there exists a promising correlation between the calculated structural parameter and the porosity of training sets of pharmaceutical tablets, having well-defined characterization. Knowing of the structural arrangement, i.

Estimation of Young's modulus of pharmaceutical tablet obtained by terahertz time-delay measurement.

In this paper, it is suggested that Young's modulus of pharmaceutical tablets with different porosity can be estimated from terahertz (THz) pulse time delay. We demonstrate such a possibility using a training set of tablets compressed from starch acetate. Once the mechanical properties are taught to the THz measurement system, using an ideal tablet as a reference, it is possible to get information about the Young's modulus of the tablet.

Inverse Abbe-method for observing small refractive index changes in liquids.

This study concerns an optical method for the detection of minuscule refractive index changes in the liquid phase. The proposed method reverses the operation of the traditional Abbe refractometer and thus utilizes the light dispersion properties of materials, i.e.

Non-contact weight measurement of flat-faced pharmaceutical tablets using terahertz transmission pulse delay measurements.

By measuring the time delay of a terahertz pulse traversing a tablet, and hence its effective refractive index, it is possible to non-invasively and non-destructively detect the weight of tablets made of microcrystalline cellulose (MCC). Two sets of MCC tablets were used in the study: Set A (training set) consisted of 13 tablets with nominally constant height but varying porosities, whereas Set B (test set) comprised of 21 tablets with nominally constant porosity but different heights. A linear correlation between the estimated absolute weight based on the terahertz measurement and the measured weight of both sets of MCC tablets was found.

Detection of porosity of pharmaceutical compacts by terahertz radiation transmission and light reflection measurement techniques.

We report on the non-destructive quantification of the porosity of pharmaceutical compacts (microcrystalline cellulose tablets) by using both optical and terahertz techniques. For the full analysis of the porosity of pharmaceutical tablets, the results obtained in both cases have shown that optical and terahertz techniques are complementary. The intrinsic refractive index of microcrystalline cellulose was estimated using the effective refractive index obtained from the time delay of the THz pulse together with the Bruggeman model for effective media.