MICRO-PLASTICS - How Can We Help?
MICRO-PLASTICS..........HOW CAN WE HELP?
Some definitions of Micro-plastics regard 5mm as the upper size limit, whilst others regard 1mm or even 330 Microns as the limit.
Whichever definition is used, it is important to clearly measure both the physical dimensions and the concentration of such particles when considering their environmental impact, control and management.
Undoubtedly legislation will soon be enacted nationally and internationally to address this issue, so we have been considering how we can help in this important area.
I-in-I combines its knowledge of imaging, precision movement control and information generation to help scientists and environmentalists around the globe gather data about this major concern.
We recognise that investigators face a complex task in gathering such information as the particle composition is highly variable, sizes are small and the sampling volumes are large.
Different methods are used to measure the concentration of Micro-plastics, including filtration, sedimentation, centrifugation and chemical staining. I-in-I can contribute to all of these techniques.
Taking an initial look at a sample before sending it for laboratory examination can save time and guide further sampling. Two forms of portable microscope help with this task:
Our handheld, battery operated video microscope has built-in illumination, LCD display, image capture and measurement capabilities. Selecting from its 4x to 14x magnification range provides an ideal overview of the sample.
Our portable optical microscope is also battery operated, has a built-in LED illuminator and it can be linked with a mobile phone for image capture. With a magnification range of 100x-400x, it is ideal for a more in-depth view of the sample. Its’ inverted configuration provides a convenient underside view for sample in a cavity slide.
When examining water samples, filters are often employed to isolate and concentrate particles into a relatively small area and the number/size is related to the sample volume. Typically 40-50mm diameter filters are used and mounted on a slide for study with the microscope.
To see and measure individual particles on filters, it is necessary to examine the contents with magnifications of 4x-500x depending on the size range of the particles. To gain measurable distribution data the filter area is either representatively sampled or sequential fields of view over the entire filter are examined and then statistically combined.
With this approach, the examination and enumerating of particles for type, size and frequency becomes a tedious and repetitive task that can ultimately compromise reporting accuracy.
I-in-I provides solutions at different levels.
ENHANCED FILTER-BASED EXAMINATION
I-in-I Video Microscopes remove the tedium of visual examining samples through eyepieces for extended periods, as the magnified particles are viewed on screen, a much less tiring approach. These images can be shared with colleagues when discussion is needed or recorded for later examination or reporting. With magnifications from 2x to 500x+, the entire size range can be accommodated.
Built for accurate measurement tasks, I-in-I Video Microscopes employ sophisticated imaging technology with ‘electronic image distortion correction’, a special ‘flat image objective lens’ and ‘built-in electronic image stacking/extended focus imaging’ when the particles are outside the focus limits of the standard microscope optics.
The basic operation described above using ‘white light’ imaging appears relatively easy, but there are challenges that need to be overcome in order to more clearly distinguish micro-plastic particles from other debris or the filter material.
Techniques involving the use of colour dyes that selectively combine with certain micro-plastics and especially micro-fibres, such as ‘Nile Red’, are being developed to provide fluorescence-type differentiation of the micro-plastic materials and achieve greater clarity for such enumeration purposes. I-in-I Video Microscopes are ideally suited to such tasks, due to the integration of wavelength selective LED illumination and interchangeable barrier filters.
Even when the enhanced images are made and presented clearly on screen, automation helps to cut through the tedium of repetitive manual field-to-field examination.
Motorised stage and focus functions, controlled by automated scanning software, enable whole sample or selective areas to be scanned without manual intervention.
Over-night or extended periods of operation are facilitated using larger capacity stages that handle up to 12-slides in one operation.
Once sample images with high resolution and extended depth of focus are created they are analysed by additional software, providing a full statistical report on the micro-plastic content.
SEDIMENTATION & CENTRIFUGATION METHOD
Standard techniques for enumeration of Micro-plastic samples include the use of sedimentation, sometimes combined with centrifugation, to provide concentration of the samples for imaging.
Using such techniques, normally involves a flat-bottom vessel where the particles settle. In this case, the particles are best observed from the underside of the vessel using an inverted microscope.
Conventional inverted configurations are derived from high magnification compound microscopes that are normally used for examination of cells cultures. They use transmitted light illumination, as such cells are transparent. Micro-plastics are generally opaque thus using this illumination and view results in images of particles ‘in shadow’.
I-in-I Video Microscopes can be mounted below the sample with the reflected illumination (white-light or wavelength specific) also mounted below the sample. In this way the sample is examined through the transparent base of the vessel while the light is directed onto the ‘viewed’ side of the sample.
In a similar way to the slide imaging described above, the sample is examined and enumerated manually or using the automated approach.
Vessels of different sizes are accommodated using sample holders that fit within the stage.
As particles lie at the base of the vessel, their focus levels are similar, thus the internal electronic focus adjustment of the I-in-I Video Microscope is used to form an extended focus image, where all the particle detail is simultaneously in focus.
Ingestion of Micro-plastic particles and fibres by plankton and other water-borne organisms provides useful data about the distribution of specific materials and their toxic effect.
Such detail, as well as non-ingested Micro-plastics, can be enhanced by the use of Confocal Microscope Imaging, as different internal components and ingested materials can be differentiated due to their fluorescence characteristics.
Often with such cellular imaging light emission from ‘out-of-focus’ planes in an image, negatively interferes with the detail from ‘in-focus’ levels, obscuring a clear view. The confocal approach produces images where all such details are clearly revealed.
Adapting an existing compound microscope is often a cost-effective means of establishing such an imaging facility without affecting the original purpose of the microscope. With a laser-free approach, regulatory issues are minimised.
Confocal Imaging can be used with upright or inverted microscope configurations and most research microscopes can be used.
I-in-I SOLUTIONS FOR MICRO PLASTICS
I-in-I provides the most comprehensive range of solutions for examining and quantifying Micro-plastic samples.
We will be pleased to discuss the most appropriate solution for your Micro-plastics projects, based upon a deep knowledge of modern imaging technology and applications.