Accessories FAQ

An achromatic doublet like the 74-ACR comprises two lenses and is designed to greatly reduce chromatic aberrations. The result is a consistent FOV for the sampling setup, where “contamination” of the spectrum caused by wavelengths outside the optimal FOV is eliminated. Typically, applications including absolute irradiance benefit the most from the use of an achromatic collimating lens.

No, in most cases you will need to purchase lenses separately.

Our cosine correctors have 180° FOV with theoretical response close to Lambert’s cosine law, which states that the irradiance or illuminance measured will vary with respect to the cosine of the angle between the optical axis of the source and the normal to the detector. Radiance or luminance is constant in all directions.

Although more expensive, quartz cuvettes are more durable, have better chemical compatibility, and perform better optically than plastic cuvettes. Consider:

• Quartz withstands mechanical strain and abrasion much better than plastic, and can be rinsed and wiped down many times without compromising optical clarity.
• Many chemicals (including organics like acetone and toluene) cannot be used with acrylics as they will readily dissolve this plastic, while quartz cuvettes allow for measurement of corrosive and caustic species.
• Plastic cuvettes tend to block UV transmission and may limit applications such as UV protein absorbance, whereas a Spectrosil® quartz cuvette will provide excellent performance from 170-2700 nm for continuous UV-Vis-NIR analysis.
• Plastic cuvettes are disposable, eliminating clean-up time; are not fragile like quartz cuvettes; and perform well for many routine lab measurements.

There are three main areas to account for when using cuvettes:

• Ensure the cuvette is used in the same orientation each time it’s removed and replaced in the sample holder. Typically, there is a small “V” or similar mark on one side of the cuvette to guide you. Also, most cuvettes have two optically clear sides and two frosted sides; take care to ensure the clear path is used for light measurement.
• Surface quality. Before placing a cuvette in the holder, use a Kimwipe® delicate task wiper or optical cloth to wipe finger oils or other interferences from the optical path. An unclean surface can create inconsistent and invalid shifts to the spectral response.
• Sample changing. Some tests may require the cuvette to be removed between measurements due to the nature of the sample (viscosity, toxicity, etc.) or some experimental parameter. However, whenever possible it is ideal to maintain the cuvette in its relative position in the holder and change the sample via pipetting. Open-top cuvettes usually accommodate this transfer well. Perhaps the most effective approach is to use a slender transfer or Pasteur pipette to add and remove fluids. The tiny tip allows for suction of fluid from the corners, minimizing the carry-over volume. The typical procedure is to rinse the cuvette with the next sample to be analyzed at least three times. If the residual fluid is less than 10% of the wash fluid (it’s more likely to be 1% or less), the carry-over is reduced to 1/1000. Also, it’s important that the pipettes be washed with the sample and not allowed to touch or scratch the inside optical surfaces.

Our cuvette holders have a “Z” dimension of 15 mm, except for the legacy product USB-ISS-UV-VIS-2, which is 10 mm. Also, qpod® and qpod 2e™ temperature-controlled cuvette holders have a “Z” dimension of 8.5 mm.

The “Z” dimension is the optical height for placement of the light beam transmitting through the cuvette, and is especially important with small-volume sampling. This dimension is measured from the bottom of the cuvette to the height of ideal optical interface; your sample volume must cover this region to produce valid spectra.

These are internal fluid channels designed to accept a constant-temperature water source for heating or cooling of the cuvette sample. The cuvette sample will equilibrate to some level between the water and ambient room temperatures, and a thermistor or other thermometer device may be used to confirm actual sample temperature. A more tightly controlled method of temperature regulation is available with the CUV-QPOD sample compartments.

The CUV-QPOD-2E has the control electronics incorporated into its body and comes with control software; the CUV-QPOD requires a separate controller. Pricing is comparable for both.

As the diagram demonstrates, light enters a bifurcated fiber assembly and then splits into two legs, each leg transmitting light to a sample. Light interacts with each sample and transmits through a second set of fibers, each of which connects to a port on the FOS-2X2-TTL.

On the spectrometer side of the setup, a bifurcated fiber assembly collects light from the FOS-2X2-TLL and funnels it to the spectrometer. With the FOS-2X2-TTL in place, you can activate the shutter on either light channel to get “clean” data from each sample. An alternative is to add a second spectrometer channel to monitor the second sample.

Fibers screw into collimating lenses on both sides of the FVA-UV, transmitting light across a metal disk into which a slit has been cut. The width of the slit varies as a function of the manually adjusted radial wheel position. Rotating the wheel allows you to vary the attenuation from the closed position (no light) to fully open.

Using a Gershun tube restricts the field of view of your sampling setup to a known value. Here’s an example: You’re collecting light emitted from a large projection screen in a movie theater. With a bare optical fiber, which has a 25° FOV, you may collect light from the entire screen. With the Gershun tube, you can adjust that FOV to 6°, for example, and collect light from a smaller part of the screen. This would allow you to compare spot to spot uniformity in brightness or color.

Yes, but you will still need to plug them into the appropriate spectrometer (Flame or USB2000+/USB4000). In addition to discrete cuvette holders and light sources, there are options with similar functionality including the ecoVis light source and CUV-FL-DA direct-attach cuvette holder.

Linear variable filters (LVFs) are useful tools for setups where high-pass, low-pass or bandpass filters are required. The filters are epoxied into slide carriers so you can move the transmission or blocking band through each filter’s wavelength range.

Where you place the LVFs is also important:

• Pre-sample. Use an in-line filter holder and a low-pass LVF-LL filter to block excitation energy from a light source above a certain wavelength, so that the light does not interfere with the fluorescence of the sample. The device is situated between the lamp and the sample. If the sample is in a cuvette, you can achieve the same result by using a cuvette holder adapter to secure the filter and then positioning the illumination fiber so that it transmits through the filter to the sample.
  
• Post-sample.By placing a filter holder and a high-pass LVF-HH between the sample and the spectrometer or detector, you can block excitation energy in the fluorescence region by passing light above a certain wavelength. You can achieve the same result with the cuvette holder adapter fixturing the LVF on the “read” port of the cuvette holder.
  
• Pre- and post-sample. You can combine pre- and post-filtering to further remove unwanted excitation signal from the fluorescence signal.

Also, LVFs can be used to reduce the stray light in absorbance measurements by limiting the illumination light to the wavelength band of interest. The LVF-HL lets you adjust both the wavelength and bandwidth of the filtering. The filter can be used either in-line or in a cuvette holder on either the illumination or read side of the holder.

Reflectance measurements are a ratio of the reflected light spectrum to the incident light spectrum. Since there is no way to directly collect all the light incident on a surface, reflectivity is usually measured relative to a reference standard. A reflectance standard can be used to calibrate and verify your spectral reflectance measurements.

The reflectance standard chosen should be similar in reflectivity to the sample to keep signal levels about the same during measurement and ensure the best S:N. The WS-1 diffuse reflectance standard is our most popular, since it is matte white in color and is >98% reflective from 250-1500 nm (then >95% reflective up to 2200 nm). The WS-1-SL can be a good choice when working in the field or in dirty environments, since it can be smoothed, flattened and cleaned if it gets pitted or dirty.

The STAN-SSH high reflectivity specular reference standard is the best choice when measuring very shiny surfaces, but it varies in reflectivity from 85-98% over its range of 250-2500 nm. This can be accounted for in OceanView software by uploading the reflectance values and correcting for the reflectivity of the standard. This data comes automatically with the STAN-SSH-NIST calibrated reference standard (250-2400 nm). If no correction is applied, OceanView will assume the standard is 100% reflective at all wavelengths, giving distorted data.

At the other extreme, the STAN-SSL low reflectivity specular reflectance standard is best for surfaces with low specular reflectance values like thin film coatings, anti-reflective coatings, blocking filters and substrates. It has just ~4.0% reflectance from 200-2500 nm.

Bifurcated fibers are a good choice for routing equal amounts of light from a light source to two different locations, and from a single sample to two spectrometers configured for different wavelength ranges (UV-Vis and Vis-NIR).

Fiber splitters are useful for mixing light from two different locations and delivering it through a single fiber to a spectrometer or sample. With a splitter, you can combine illumination from two different light sources, or mix light collected from two different sampling points before delivery to a spectrometer.

Fiber splitters have lower transmission efficiency than bifurcated fibers due to the inefficient geometrical overlap between the fiber cores at their junction point. This effectively eliminates splitters with small core diameter fibers for most applications, as their thicker cladding diameter results in minimal geometric overlap.

Use a smaller diameter fiber for routing high light levels, as in absorbance and irradiance measurements, and a large diameter fiber for low light level applications such as fluorescence. We offer fibers in core diameter sizes ranging from 8 µm to 1000 µm, but recommend 400 μm fibers as a good starting point for most applications.

Our fibers have FOV of ~25°. Adding an accessory like a collimating lens or cosine corrector to the end of a fiber allows users to adjust the FOV, collection efficiency and spatial resolution of their setup.

Keyed SMA 905 connectors are useful to achieve the same relative fiber orientation to the spectrometer, which can be critical for high-precision measurements or certain complex fiber designs. Additionally, patch cords with linear keyed SMAs may provide improved efficiency in spectrometers with a tall detector, such as those in the QE Pro, Maya2000 Pro, or NIRQuest optical benches.

Ocean Optics optical oxygen sensors are compatible in both gas and liquid phases. Dissolved oxygen measurements are critical in fields such as medical, biological, marine and beverages. While aqueous DO₂ measurements are the most common, Ocean Optics oxygen sensors also are compatible in common process fluids such as alcohols, fuels and high-oxygen-capacity fluorocarbon fluids.Since these fluorescent chemical sensors work on the principle of partial pressure, the conversion from these ppO₂ values to the typical mg/L (ppm) units requires some information about the liquid system properties. This may include salinity levels and/or Henry’s coefficients to determine relative affinity of oxygen into that system

We have numerous analytes with our SERS substrates using a QE Pro-Raman spectrometer and 785 nm probe, as shown in the table below. Limits of detection will vary with the sensitivity of the Raman instrument used for measurement.

Analyte	Classification	Limit of Detection	Laser Wavelength (nm)
Food & Agriculture
Acetamiprid	Neonicotinoid insecticide	1 ppm	785
Aflatoxin B1	Aflatoxin	No SERS Activity	NA
Bardac	Insecticide	1 ppm	785
Captan	Fungicide	1000 ppm	785
Carbophenothion	Organophosphate insecticide	1 ppm	785
Carbofuran	Carbamate pesticide	1000 ppm	785
Chlorpyrifos	Organophosphate insecticide	1 ppm	785
Clothianidin	Neonicotinoid insecticide	10 ppm	785
Coumaphos	Insecticide	1 ppm	785
Crystal Violet	Fungicide	10 ppt	785
Deoxynivalenol	Mycotoxin	No SERS Activity	NA
Dichlorvos	Organophosphate insecticide	100 ppm	785
N,N-diethyl-meta-toluamide (DEET)	Insect repellent	1 ppm	785
Diphenylamine	Diphenyl fungicide	1 ppm	785
Fipronil	Insecticide	No SERS Activity	NA
Fludioxonil	Pyrrole fungicide	10 ppm	785
Folpet	Fungicide	1000 ppm	785
Imidacloprid	Insecticide	1 ppm	785
Malachite Green	Fungicide	1 ppb	785
Malathion	Organophosphate insecticide	1 ppm	785
Melamine	Food adulterant	1 ppm	532 or 785
Methomyl	Carbamate pesticide	100 ppb	785
Metofluthrin	Insect repellent	10 ppm	785
Permethrin	Insecticide	1 ppm	785
Phosalone	Organophosphate insecticide	1 ppm	785
Phosmet	Organophosphate insecticide	1 ppm	785
Profenofos	Organophosphate insecticide	10 ppb	785
Thiamethoxam	Insecticide	1 ppm	785
Thiram	Fungicide and animal repellent	1 ppm	785
Transfluthrin	Insecticide	10 ppm	785
Tribufos	Organophosphate pesticide	1 ppm	785
Trichlorfon	Organophosphate insecticide	1 ppm	785
Illicit Drugs
Cocaine	Stimulant	1 ppm	785
Codeine	Opiate	100 ppb	785
Heroin	Opiate	1 ppm	785
Ketamine	Hallucinogen	100 ppm	785
MDMA	Stimulant	10 ppm	785
Methamphetamine	Stimulant	1 ppm	785
Morphine	Opiate	10 ppb	785
Tetrahydrocannibinol (THC)	Psychotropic (Cannabis)	1 ppm	785
Dyes
Rhodamine B	Dye	1 ppm	785
Rhodamine 6G	Dye	1 ppm	785
Ru(Bpy)3	Dye	1 ppb	785
Biologicals
Albumin (bovine)	Protein	500 ppm	785
Albumin (human)	Protein	500 ppm	785
E. coli	Bacterium	Unknown	785
Glucose	Sugar	No SERS Activity	NA
Hemoglobin	Protein	No SERS Activity	NA
Antibiotics
Ceftiofur	Antibiotic	10 ppm	785
Penicillin	Antibiotic	10 ppm	785
Tetracycline	Antibiotic	10 ppm	785
Miscellaneous
Acetate	Salt	No SERS Activity	NA
1-aminohydantoin HCl	Anti-cancer agent	1 ppm	785
Bitrex (denatonium benzoate)	Denaturant	No SERS Activity	NA
BPE	Taggant/Marker	100 ppt	785
Geosmin	Flavor compounds	No SERS Activity	NA
GtMIB	Flavor compounds	No SERS Activity	NA
2-methylisoborneol (MIB)	Flavor compounds	No SERS Activity	NA
2-naphthalenethiol	Flavoring agent	100 ppb	785
Nicotinamide	Vitamin	10 ppm	785
Oxalate	Nutrient	No SERS Activity	NA
1,10-phenanthroline	Heterocyclic organic	100 ppb	785
(-)-Riboflavin	Vitamin	10 ppm	785
Semicarbazide HCl	Detection agent	10 ppm	785

All deuterium sources have an alpha line, a sharp spectral feature centered at 655 nm. This feature and other deuterium lines produce “unbalanced” output in the deuterium and halogen sources. Simply adjusting the integration time of the spectrometer to suppress the alpha line does not solve the problem as the efficiency of the system at UV wavelengths drops significantly, compromising signal-to-noise performance.

A system of proprietary internal mirrors and filters eliminates the D-alpha, D-beta and Fulcher lines in the deuterium source, producing a “smoother” spectrum across the entire wavelength range and eliminating problems associated with saturation. By comparison, most combination UV-NIR sources can be adjusted for relative intensity only.

• Check that the correct cables are connecting the PX-2 to the spectrometer.
• Ensure that its power supply is connected to a power outlet.  
• Verify that the switch on the PX-2 is set to the corresponding mode that will be used (i.e. single vs. multiple flash mode).

When using continuous strobe, the continuous strobe delay (the length of time between each flash) must be a value that divides evenly into the integration time.  For example if you have an int. time of 100 ms and use a continuous strobe delay of 20,000 µs, since 100/20 = 5 there will be 5 flashes of the PX-2 in the 100 ms int. time.  The only other requirement is that the lamp does not exceed its maximum frequency of 220 Hz.

////// OceanDirect Testing /////

// Set up PX-2 with single strobe & get a spectrum using .NET interface

// Set int. time to 10ms

ocean.setIntegrationTimeMicros(deviceID, ref errorCode, 10000);

// Set delay of 1560 microseconds

ocean.AdvancedFeatures().SingleStrobeController().setStrobeDelay(Global.deviceID, ref errorCode, 1560);

// Set pulse width to 40 micros

ocean.AdvancedFeatures().SingleStrobeController().setStrobeWidth(deviceID, ref errorCode, 40);

// enable single strobe

ocean.AdvancedFeatures().SingleStrobeController().setStrobeEnable(Global.deviceID, ref errorCode, true);

// Get a spectrum

// ocean.getSpectrum(deviceID, ref errorCode);

////// TESTING /////

// Set up PX-2 & get a spectrum using Continuous Strobe

// Set int. time to 100ms

ocean.setIntegrationTimeMicros(deviceID, ref errorCode, 100000);

// Set Continuous Strobe Delay to 20000 micros

ocean.AdvancedFeatures().ContinuousStrobeController().setContinuousStrobePeriodMicroseconds(deviceID, ref errorCode, 20000);

// enable Continuous Strobe

ocean.AdvancedFeatures().ContinuousStrobeController().setContinuousStrobeEnable(deviceID, ref errorCode, true);

//Get a spectrum

ocean.getSpectrum(deviceID, ref errorCode);