Purpose: Reviews the types of transmittance cells.

      If you have any questions regarding parts, please reach out to the HunterLab Customer Experience team.

HunterLab offers several types of transmittance cells for measuring the color of transparent liquids using sphere instruments:

• HunterLab Glass Cells: Rectangular, available in multiple path lengths, open top and capped, ensuring no compromise in performance.
• Molded Glass Cells: Rectangular and rugged, ideal for hot solutions and suitable for heating.
• Plastic Cells (20-mm Path Length): Rectangular, come with caps, disposable.
• Plastic Cells (10-mm Path Length): Rectangular, open top, disposable.
• HunterLab Glass Flow Through Cells: Available in multiple path lengths, designed for automatic operation.
• HunterLab Small Volume Glass Cells: 10-mm path length, 5 mL sample volume.
• Round Glass Vials: 24-mm path length, rugged, suitable for heating, disposable.
• Analytical and Semi-Micro Cells: Available in 10-mm and 20-mm path lengths, made of glass or disposable plastic, open or capped, requiring very small sample volumes.
• HunterLab Glass Cells: Open top and capped.

HunterLab Glass Cells - Open Top and Capped

For optimal measurement performance, HunterLab glass transmittance cells are recommended. These cells are custom manufactured to HunterLab's specifications using optical quality glass. Each cell is a three-piece construct, fused glass-to-glass and then annealed. Solvents do not affect these cells as the components are fused at the edges, not glued. They feature two flat windows and a U-shaped spacer abraded to minimize internal reflectance. HunterLab Quality Assurance monitors the path length, dimensions, and flatness of these cells, making them ideal for critical measurements.

These cells, with sample contents, can be heated to a temperature of 275°C without injury provided the heating method is even and gradual (not directional heating like a hot plate). An air-circulating heater and gradual gradient heating are recommended at temperatures near the limit of 275°. To avoid condensation, liquid samples should be heated to those temperatures in the cell or else the cell should be preheated before adding the hot sample.

These cells can be heated to 275°C without damage, provided the heating method is even and gradual (not directional heating like a hot plate). An air-circulating heater and gradual gradient heating are recommended at temperatures near the limit of 275°C. To avoid condensation, liquid samples should be heated in the cell or the cell should be preheated before adding the hot sample.

Molded Glass Cells for Hot Solutions

These Pyrex glass cells are produced by a one-step tubular injection molding operation on a stainless steel (Class A) mandrel, making them robust for holding hot solutions. They can also be used to heat crystalline powders to a liquid form before measurement. These molded glass cells are:

• Physically rugged for measuring hot solutions due to their molded construction.
• Rectangular with standard path lengths.
• Compatible with the C02-1005-481 Transmittance Cell Holder or D02-1011-568 Transmittance Spill Tray and Cell Holder in the transmittance compartment of all HunterLab sphere instruments.

While their performance characteristics (finish, repeatability, and reproducibility) are not as optimal as HunterLab glass cells, they are acceptable for many applications. Thickness variation in the outside wall of these cells can result in haze readings that are 2 haze units higher than those read using HunterLab cells. As an extra service, SGI will grind the outside faces of these cells to minimize wall distortion and improve haze measurement agreement with HunterLab transmittance cells.

Cells are available from: SGI - Scientific Glass & Instruments, Inc. 2521 Fairway Park Drive, Suite 404 Houston, TX 77001 TEL: (703) 682-1481 FAX: (713) 682-3054 NET: www.sginstr.com

(data table)

Disposable Plastic Cells - 20-mm Path Length

Tissue culture flasks made of clear polystyrene with screw-on caps for volatiles can serve as inexpensive transmittance cells. These are particularly useful for measuring samples that are difficult to clean or handle, and are handy when large numbers of measurements are required. While their performance is not as optimal as HunterLab glass cells, they are appropriate when the need for a disposable cell outweighs the small compromise in performance.

(Illustration and Part # tables)

HunterLab Glass Flow Through Cells

Flow through cells are useful for continuous sampling or ease of measurement with transparent liquid products.

• All flow cells will fit in the transmittance compartment of HunterLab sphere instruments using the D02-1009-960 Flow Through Cell Holder.
• The construction of the cells is clear annealed borosilicate, which can be heated (including the sample) in a water bath to 100 degrees Centigrade with no difficulty.
• The flow cells are aligned vertically in the holder and fed from the bottom to minimize air bubbles.
• The inlet and outlet ports are 7-mm ID and 9-mm OD to permit a high flow rate with port continuity at all path lengths so that the same tubing and pump can be used.
• You will need to purchase tubing and a peristaltic pump appropriate for your needs from non-HunterLab sources. Tygon tubing is clear, robust, and has good product life as                      peristaltic tubing. Peristaltic pumps such as the Master Flex line are acceptable. Both products are available from Cole Parmer (www.coleparmer.com).

Flow Cell Operation

• A length of tubing is attached to the 9-mm OD of each of the two cell ports. At the other end of each length of tubing, it is good idea to attach a piece of glass tubing to be lowered into a beaker of sample liquid.
• Place the flow cell in the D02-1009-960 holder.
• Turn the peristaltic pump on. The pump rubs on the outside of the tubing, creating an internal vacuum within the tubing that sucks liquid through and into the cell.
• The cell is oriented in the D02-1009-960 Flow Through Cell Holder with the outlet port at the top. Air is automatically forced out of the cell as the liquid comes in. As soon as the flow cycle is complete, a measurement can be taken.
• To flush the system, turn off the pump, place the glass ends of the tubing into a beaker of water/solvent and cycle until clean.

Long path transmittance cells for YI  

Long Path YI consists of a long-path-spectrophotometer, PC-installed software for YI analysis and quartz cells (1cm x 25cm). Let's assume YI is Yellowness Index E313 C/2 or similar, a standard metric for quantifying trace yellowness in near water-white liquids in Hunter Lab software. There may be a mix up in cell dimensions here. For this UV/VIS analytical spectrophotometer, a 1cm or 10mm cell width is standard, but variation in depth to accommodate sample path length.

A 25cm or 250mm depth is not likely the case and the depth dimension may be 2.5cm or 25mm. Regular analytical transmittance cells have internal dimensions of 10mm width x 10mm depth, with the odd case at 10mm width x 20mm depth. A long path length cell is usually between 20mm and 100mm depth, and this increased sample path length would only be used to measure YI yellowness of near colorless liquid samples.

Hunter Lab standard colorimetric transmittance cells have 10, 20, 33 and 50mm path lengths.

2-mm flow cell

Some liquid samples are so highly absorbing or translucent such that little light from the instrument's lamp can get through in transmittance. By using a very thin 2-mm path length with these samples, it is possible to differentiate lot differences in color that would not be possible with a regular path length cell.

• HunterLab Part # A13-1011-613 is a practical small volume transmittance cell for transmittance color measurements that was developed to measure the color of small volumes of very      expensive development drugs in the pharmaceutical industry. It is a small, optically clear, manual loading, 10-mm path length round cell with a screw top.
• A13-1011-613 includes both an inject-a-cell top (that allows you to use a needle to load the cell through an injectable silicone membrane in the cell top) and second solid propylene        top (good for volatile samples).
• A special D02-1011-886 Transmittance Holder is needed to hold this small volume round cells at either the TTRAN or RTRAN port.
• This 10-mm path length round glass cell has an OD of 28-mm and an ID of 25-mm which just covers the transmittance port. If you fill the cell to the top, 5-mL of sample is needed. If      you fill the cell to the bottom of the screw top above the viewed sample area, the volume required is 4-mL of sample. By comparison, the standard rectangular HunterLab 10-mm cell      uses 20-mL of sample.
• The throat has a 12-mm OD and an 8-mm ID, allowing the cell to be loaded with a pipette or needle.
• The 10-mm path length allows you to standardize to top-of-scale (100% transmittance) using the cell with distilled water as a blank, and yet still have sufficient path length to                  differentiate small amounts of chromofores in near-clear liquids, as well as measure the APHA/PtCo/Hazen color scale if desired.

Round Small Volume (4mLx10mm) Transmittance Cell

Hunter Lab's round cell (A13-1011-613) is a practical small volume cell for transmittance color and haze measurements.

• This small, round, optically clear, manual loading, transmittance cell has a 10 mm path length and a screw top.
• It was originally developed to measure the color and haze of small volumes of very expensive development drugs in the pharmaceutical industry. The cell is made of clear                         borosilicate glass. Quartz is not needed for color measurement.
• This cell has both an inject-a-cell top (that allows the client to use a needle to load the cell through an injectable silicone membrane in the cell top) and second solid propylene top         (good for volatile liquids).

• A special Transmittance Holder (D02-1011-886) is needed to consistently center this round cell at the Total Transmittance (TTRAN) or Regular Transmittance (RTRAN) port positions       of Hunter Lab's ColorQuest XE, ColorQuest XT, VISTA, UltraScan PRO and UltraScan VIS sensors.
• This round glass cell has an OD of 28mm and an ID of 25mm which just covers the transmittance port. If you fill the cell to the top, 5 ml of sample volume is needed. If you fill the cell       to the bottom of the screw top above the viewed sample area, the volume required is 4 mL of sample. By comparison, the standard rectangular Hunter Lab 10 mm cell uses 20mL of         sample. The throat of the inlet port has a 12mm OD and an 8-mm ID allowing the cell to be loaded quickly with a pipette or needle.

• The 10 mm path length allows the user to standardize to top-of-scale (100% transmittance) using the cell with distilled water negating any cell effects, and yet still have sufficient             path length to differentiate small amounts of chromophores in near-clear liquids, as well as measure sensitive metrics like YI Yellowness Index or the APHA/Pt-Co/Hazen color scale if       desired.
• Transmittance Haze measurements can also be made at the same time as the color measurements in TTRAN LAV mode.
• Specifications for the HunterLab round small volume glass cells are as follows:

HunterLab Catalog Number	Path Length (mm)	Diameter of Measurement Face (mm)	Port OD/ID (mm)	Approximate Cell Volume Needed (ml)
A13-1011-613	10	25	12/8	4
CMR-3111	20	25	12/8	8

 

• HunterLab has a CMR-3111 20 mm version round cell that is the same as the 10 mm round cell but with an increased 20 mm path length.  8mL Min Vol Round 20mm Trans Cell             (CMR-3111) Used with ColorQuest XE, ColorQuest XT, VISTA, UltraScan PRO, and UltraScan VIS.
• Provides a transmittance cell with a 10mm path length that just covers the TTRAN port and requires just 8mL of sample volume. The cell is round with a 25mm diameter ID and                 28mm diameter OD. The inlet port for manual loading has an 8mm diameter. The cell comes with two PTFE screw caps - 1 injection and 1 solid. The cell is used with HunterLab                 Transmittance Holder (D02-1011-886 purchased separately).

Disposable Round Glass Vials - 24-mm Path Length

 

 

These round vials have the advantage of being made of borosilicate glass appropriate for corrosives. They come with caps to handle volatiles and are sufficiently cost effective to be disposable or recyclable.

• The HunterLab D02-1011-550 Transmittance Holder for 27 - 30-mm Vials positions the curved surface of the round glass vial consistently for measurement at the TTRAN port.
• The D02-1011-550 holder accepts all 20 mL, 40 mL and 60 mL round glass vials and fits in all HunterLab sphere instruments. There are 4 user-adjustable screws in the holder that can            be employed to ensure that the vial does not wiggle in the holder.
• The 40-mL (1 1/3 oz) borosilicate glass threaded vial with a 27, 28 or 29-mm OD and 61-mm height is recommended for general use as a round disposable glass transmittance cell               on HunterLab instruments.
• The 20-mL (2/3 oz) version is recommended for small sample volumes. These vials will fit in the transmittance compartment of the VISTA, UltraScan PRO, or UltraScan VIS with the               door closed.
• There is also a 60-mL high vial of the same diameter that fits above the door for exterior venting or external loading if required. The 60-mL size is recommended for measuring                     the color of hot solutions, as the extra height allows the tube to be more easily grasped by a set of tongs.
• In all cases, the internal diameter is 24-mm, defining the sample path length.
• These round tubes work well when the material must be centrifuged for mixing or separating, or if the materials need to be heated. The polypropylene caps and molded borosilicate           glass can be autoclaved up to their melting points (450 degrees C), provided the heating and cooling is done slowly at a rate of 50 degrees per hour or less. There is the potential for           cracking if the temperature is raised/lowered to high levels at rapid rates. For lower temperatures (< 150 degrees C), heating and cooling should be no problem.
• Round glass vials can be ordered from: Qorpak, Corporate One West, 1195 Washington Pike Bridgeville, PA USA 15017-2808 TEL: 800-922-7558, TEL: 412-257-3100, FAX: 412-257-               3001, NET: www.qorpak.com

Vial Options include:

• Polypropylene caps in solid polypropylene and injectable silicone septa are available assembled with the vials or separate.
• A variety of internal cap liners can also be chosen, including metal, foamed polyethylene, polyethylene, vinyl and Teflon (minimal chemical reaction) disc liners.
• Individual barcode labels can be affixed for sample identification.
• There are a variety of cleaning procedures (vacuum ionization, particulate washing, and gamma sterilization) that can be done to ensure that there are no residual particulates (dirt,              dust, carton lint, fine glass particulates, bacteria) or film (bottle release agents, aerosols, oil) on the glass surface. The most cost-effective is to order vials that are cleaned but do not            have a certificate enclosed with each box. This provides an EPA-cleaning without the additional cost of certification.
• Some suppliers also have the same products available in HDPE: high-density polyethylene.
• These vials usually come shrink-wrapped with 72 or 144 in a case.

FAQ:   Can transmittance cells be used to measure opaque liquids or powders in reflectance?

Answer:

Yes, the 10-mm plastic cells will cover the reflectance port using the sample clamp to position the cell and keep the cell flush at the port while maintaining a constant surround using the white ceramic backing if the sample is not fully opaque.

It is recommended that you standardize in RSEX LAV (Reflectance Specular Excluded, Large Area of View) mode to negate the specular reflectance off the plastic window from the measurement. The absorbance of the plastic window will still be part of the measurement, but it is a constant and less than 1% absorbance.

See attached PDF fil for the complete article with illustrations, part numbers, and data tables.

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