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Articles Review[edit | edit source]
Abstract: A flow-injection manifold based on reagent injection into the sample stream is described for the determination of phosphate in natural waters. A double-beam photometric detector incorporating light-emitting diodes and photodiodes in enclosed in a 20-cm3 box. The response is linear over the range 0–2000 μg l−1 phosphate-phosphorus (r = 0.9992) and the limit of detection (2σ) is 12 μg l−1 phosphorus. The reagents are stable for at least 30 days and there is no interference from 10 mg l−1 silicate-silicon
- A low cost remote monitoring flow injection sensor device to measure phosphate using LED and photo detector
- Uses "double beam" method which means they used 2 set of LED - photo detector pair. One set is used as a reference measurement without sample and another set as sample measurement. This method is used to compensate for temperature effect and noise
- The paper showed the feasibility without extensive performance measurement
A portable battery-powered flow injection monitor for the in situ analysis of nitrate in natural waters [edit | edit source]
Abstract: The design and performance of a portable, automated flow injection (FI)-based photometric monitor are described. The system is controlled by an in-house microcomputer system that enables the monitor (including a solid state detector) to operate from a 12 V battery supply. The monitor uses the cadmium reduction/diazotization method to analyse for nitrate with a linear range of 0 to 12 mg l-1 and a limit of detection of 0.05 mg l-1 (NO3-N). The hardware and software design, monitor performance and results obtained during unattended operation are presented
- Uses single LED - photo detector pair configuration. To compensate for thermal effect, noise and to perform calibration, two set of measurement is done; one with the sample and one with standard nitrate. After some software filter, the ratio is calculated to get the absorbance value
- Measured accuracy for seven day trial is < 5 %
- Uses cadmium reduction to prepare the sample for detection
Abstract: A new spectrometer, here denoted the SLIM (simple, low-power, inexpensive, microcontroller-based) spectrometer, was developed that exploits the small size and low cost of solid-state electronic devices. In this device, light-emitting diodes (LED), single-chip integrated circuit photodetectors, embedded microcontrollers, and batteries replace traditional optoelectronic components, computers, and power supplies. This approach results in complete customizable spectrometers that are considerably less expensive and smaller than traditional instrumentation. The performance of the SLIM spectrometer, configured with a flow cell, was evaluated and compared to that of a commercial spectrophotometer. Thionine was the analyte, and the detection limit was ∼0.2 μM with a 1.5-mm-path length flow cell. Nonlinearity due to the broad emission profile of the LED light sources is discussed
- A portable, low cost colorimeter for remote data logging application
- Uses "flow cell" ? to allow for unattended sensing
- Uses multiple LED because the chemical under test can absorb broader wavelength
- Photo detector with integration and averaging method to detect intensity of light
- Suffer from non-linearity because of the combination between absorbance profile and LED spectrum
- Lost to commercial spectrometer in the aspect of wavelength resolution and noise
- Claimed could easily be changed to fluorometer just by making the detection angle 90 degree to the light source
Abstract: A robust, filter-based portable fluorometer was designed, prototyped, and tested for time-resolved luminescence (TRL) analysis. Its flexible optical design allows interchangeable configurations to support three measurement modes: liquid-phase TRL using a sample cuvette, solid-matrix TRL using a sorbent strip, and evanescent-field TRL using a quartz-rod waveguide. A xenon flashlamp is used as the light source and a photomultiplier tube (PMT) as the photodetector. A gating technique was implemented to overcome PMT saturation by the intense xenon lamp flash, therefore higher gains can be set to measure weak luminescence signals. The TRL signal is digitized at a 4μstime resolution and a 12bit amplitude resolution. Individual flashes were monitored by a photodiode and its current was integrated to compensate for source light fluctuation. Using tetracycline as a model analyte, a 0.025ppb limit of detection (LOD) with a typical 2% relative standard deviation, and a 3 orders of magnitude (0.5–300ppb) linear dynamic range (r2=0.9996) were achieved
- A portable, but not low cost, fluorometer for time resolved luminescence analysis
- Uses xenon flash lamp with filter as excitation source, and photo multiplier tube with filter as the detection device
- This device claimed to have better SNR by about 1 order of magnitude than state of the art commercial spectrometer at the time of the writing
- Intended to detect drugs such as tetracycline
- Could be used to test different compounds due to the multi wavelength light source
Abstract: This article relates to the construction of a portable, low cost, thermal-regulating light-emitting diode (LED)-based, handheld fluorometer. This regulated fluorometer is based on both a low thermal mass infrared heater, and an orthogonal geometry LED-based filter fluorometer. Power is supplied through an external power supply and data is collected in real time through standard serial interfaces of personal computers or personal digital assistants. Thermal regulation is automatically maintained using temperature sensor feedback control. Optical excitation relies on LED light source(s) and optical detection is made through an adjustable integrating photodetector. With such a handheld system, applications requiring temperature sensitive photometric measurements for real-time analyte detection can be more easily performed in the field
- Portable, low cost fluorometer using blue LED as excitation source and integrating photo detector as detection element
- Sample can be thermal regulated using infrared heater and infrared thermometer
- Software only regulate temperature and changing integration settings, raw data output for further processing
- Tested using FAM fluorescent dye
- No comments about performance or accuracy of the fluorometer
Portable light-emitting diode-based photometer with one-shot optochemical sensors for measurement in the field [edit | edit source]
Abstract: This report describes the electronics of a portable, low-cost, light-emitting diode (LED)-based photometer dedicated to one-shot optochemical sensors. Optical detection is made through a monolithic photodiode with an on-chip single-supply transimpedance amplifier that reduces some drawbacks such as leakage currents, interferences, and parasitic capacitances. The main instrument characteristics are its high light source stability and thermal correction. The former is obtained by means of the optical feedback from the LEDpolarization circuit, implementing a pseudo-two light beam scheme from a unique light source with a built-in beam splitter. The feedback loop has also been used to adjust the LED power in several ranges. Moreover, the low-thermal coefficient achieved (−90 ppm/°C) is compensated by thermal monitoring and calibration function compensation in the digital processing. The hand-held instrument directly gives the absorbance ratio used as the analytical parameter and the analyte concentration after programming the calibration function in the microcontroller. The application of this photometer for the determination of potassium and nitrate, using one-shot sensors with ionophore-based chemistries is also demonstrated, with a simple analytical methodology that shortens the analysis time, eliminating some calibrating solutions (HCl, NaOH, and buffer). Therefore, this compact instrument is suitable for real-time analyte determination and operation in the field
- Another portable, low cost, LED based colorimeter to measure disposable, one use test strips
- What's interesting here is that they used optical feedback to stabilize intensity power from LED. In experiment they measured LED light intensity varies with temperature and time
- They used digital temperature sensor to compensate global electronic thermal drift. This is in contrast with article "Hand-held thermal-regulating fluorometer" where they regulate the temperature instead of compensating the effect of it
- The use of integrated photo diode with transimpedance amplifier to reduce some drawbacks such as leakage current, noise pickup, stray capacitance
- Precise and adjustable bias for LED using low thermal drift voltage reference, DAC, and digital potentiometers
Abstract: Global warming is believed to be caused by increasing amounts of greenhouse gases (mostly CO2) discharged into the environment by human activity. In addition to an increase in environmental temperature, an increased CO2 level has also led to ocean acidification. Ocean acidification and rising temperatures have disrupted the water’s ecological balance, killing off some plant and animal species, while encouraging the overgrowth of others. To minimize the effect of global warming on local ecosystem, there is a strong need to implement ocean observing systems to monitor the effects of anthropogenic CO2 and the impacts thereof on ocean biological productivity. Here, we describe the development of a low-cost fluorescent sensor for pCO2 measurements. The detector was exclusively assembled with low-cost optics and electronics, so that it would be affordable enough to be deployed in great numbers. The system has several novel features, such as an ideal 90° separation between excitation and emission, a beam combiner, a reference photodetector, etc. Initial tests showed that the system was stable and could achieve a high resolution despite the low cost
- A relatively low cost fluorometer for remote unattended sensing using blue and violet LED to excite sample containing pCO2
- 90 degree separation between excitation light and emission light, achieved using optical tube consisting of dichroic mirror, splitter, excitation filter and mirror. Previous other literature without using optical tube suffer from scattering of light from source
- Instability of LED light intensity is addressed by adding reference photo detector. Previous literature titled "Portable light-emitting diode-based photometer with one-shot optochemical sensors for measurement in the field" used optical feedback method which introduce another noise problem
- Uses microfluidic chip to place the sample
- Lower precision than the best currently available pCO2 sensor. The measured average is 1.7 μatm compared to the best precision 1 μatm
Fluorometer comparison[edit | edit source]
|Fluoroskan Ascent Microplate Fluorometer||Automated fluorometer system with reagent dispenser and 384 well plates.||$19000 - $37000 (Depends on the submodel)||http://carefordescientific.com/search.php?search_query=fluoroskan&x=0&y=0|
|Varioskan LUX multimode microplate reader||All in one system including absorbance, fluorescence, luminescence, alpha screen, time resolved fluorescence measurement. Multiple wavelength||$28000 - $55000 (Depends on the submodel)||http://carefordescientific.com/search.php?search_query=varioskan&x=0&y=0|
|BMG Polarstar Omega||All in one including absorbance, fluorescence including FRET, luminescence, time resolved fluorescence, and fluorescence polarization||$17000 (used)||https://www.dotmed.com/listing/microplate-reader/bmg/polarstar-omega-/1444673|
|Flx800 Fluorescence Reader||Cost effective filter based microplate reader; multiple wavelength; fluorescence, luminescence; reagent dispenser||$1200 - $3000 (used)||https://www.google.com/search?q=flx800+fluorescence+reader&ie=utf-8&oe=utf-8#q=flx800+fluorescence+reader&tbm=shop|
|Tecan Infinite F500||microplate reader; filter based; for absorbance, fluorescence, luminescence; multiple wavelength||-||-|
|Gemini EM Microplate Reader||Dual monochromator, temperature regulation, 6 - 384 well microplates||$5600 (used)||https://www.google.com/search?q=Gemini+EM+Microplate+Reader&ie=utf-8&oe=utf-8#q=Gemini+EM+Microplate+Reader&tbm=shop|
|Qubit 3.0 Fluorometer||Portable fluorometer for measuring DNA, RNA, protein. Could be used for raw fluorescence data using built-in blue and red LED||$2450||https://www.thermofisher.com/us/en/home/industrial/spectroscopy-elemental-isotope-analysis/molecular-spectroscopy/fluorometers/qubit/qubit-fluorometer.html|
|Jenway 62 series Fluorometer||Fluorometer using xenon lamp and photodiode/photomultiplier tube; filter based operation; cuvette to hold samples||$6500 - $9200||http://www.bibby-shop.com/products.aspx?cid=1&flt=Fluorimeters|
|Horiba Aqualog||Benchtop fluorometer; multiple wavelength; monochromator; measures absorbance and fluorescence||-||-|
|DeNovix QFX Fluorometer||Small, Android touchscreen interface; multiple wavelength; uses LED and photodiode||$2450||http://store.denovix.com/product-p/qfx.htm|
|Promega quantus fluorometer||Portable, small fluorometer; Red and blue fluorescence channel;||$1700||http://www.promega.com/products/fluorometers-luminometers-multimode-readers/fluorometers/quantus-fluorometer-simple-quantitation/quantus-fluorometer/|
|Stellarnet spectro fluorometer system||Modular fluorometer where we can choose which component we need; miniature fiber optic spectro fluorometer; light source depends on selected options||$3000 - $7500||http://www.stellarnet.us/systems/low-cost-spectrofluorometer-systems/?gclid=CjwKEAjwjca5BRCAyaPGi6_h8m8SJADryPLhCPqxGGED3ES o33HRFDCHjF2_oaSaLwASRLAouCP3pRoCDLvw_wcB|
References[edit | edit source]
- P. J. Worsfold, J. Richard Clinch, and H. Casey, "Spectrophotometric field monitor for water quality parameters", Analytica Chimica Acta 197 pp. 43–50 (1987).
- N. J. Blundell, A. Hopkins, P. J. Worsfold, and H. Casey, "A portable battery-powered flow injection monitor for the in situ analysis of nitrate in natural waters", J Automat Chem 15(5) pp. 159–166 (1993).
- K. M. Cantrell and J. D. Ingle, "The SLIM Spectrometer", Anal. Chem. 75(1) pp. 27–35 (2003).
- G. Chen, "Versatile portable fluorometer for time-resolved luminescence analysis", Review of Scientific Instruments 76(6) pp. 63107 (2005).
- A. S. Farmer, D. P. Fries, W. Flannery, and J. Massini, "Hand-held thermal-regulating fluorometer", Review of Scientific Instruments 76(11) pp. 115102 (2005).
- A. J. Palma, J. M. Ortigosa, A. Lapresta-Fernández, M. D. Fernández-Ramos, M. A. Carvajal, and L. F. Capitán-Vallvey, "Portable light-emitting diode-based photometer with one-shot optochemical sensors for measurement in the field", Review of Scientific Instruments 79(10) pp. 103105 (2008).
- X. Ge, Y. Kostov, R. Henderson, N. Selock, and G. Rao, "A Low-Cost Fluorescent Sensor for pCO2 Measurements", Chemosensors 2(2) pp. 108–120 (2014).