Timberline TL-2800 Single Channel Ammonia Analyzer / Nitrate Analyzer
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Listed in Standard Methods Online.
April 2004 - Method 4500-N D
"Conductimetric Determination of Inorganic Nitrogen"
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Timberline Instruments TL-2800 is a tubular membrane diffusion system for analysis of inorganic nitrogen in aqueous solutions. The patented gas diffusion / conductivity principle provides results unaffected by turbidity, color, or particulate matter in the sample.
The general principle is to combine an aqueous sample with a caustic solution and then contact the resultant mixture with a hydrophobic tubular membrane. Gaseous ammonia migrates through the membrane into a dilute absorber solution and is transported to a high performance conductivity detector. Ultra sensitive ammonia detection (down to 20 ppb) is easily achievable with a cycle time of less than 1 minute per sample.
This analytical approach can be used to test almost any aqueous media and is ideal where interference issues are a concern. Excellent quantitative results can be obtained on diverse media such as soil extracts, waste water, blood, milk and urine.
Common Applications
Soil Extracts
Waste Water Samples
Kjeldahl Digestates
Fermentation Kettle Samples
Body Fluids - Blood, Urine, and Milk
Special Features
Standard Diffusion Membrane Cell
The diffusion membrane cell directs the liquid flow through the tubular membrane to the conductivity detector. Each diffusion cell is encased in a compact box and is clearly labeled to assist in fluid line connections. The membrane is rugged, low maintenance, user friendly and has an anticipated lifetime of greater than a year. The detection of 10ppb ammonia is easily achievable on a day to day basis with excellent reproducibility.
Smooth, Reliable Reagent Delivery
A variable speed peristaltic pump is supplied with a five-channel micro cassette pump head. Each channel can be installed and removed independently from the others to allow easy tubing replacement. The 8-roller design of the pump head provides added precision and smooth flow. Tubing for the micro cassette pump head has three color coded collars and provides two pumping segments. Use one segment and then transfer to the other for double the tubing life.
Sensitive, Stable Detection
The TL-2800 uses a temperature controlled conductivity cell that is isolated from external temperature changes. A unique heat exchanger, placed before the cell, preheats the absorbing solution. This combination provides exceptional baseline stability even at high sensitivity ranges.
Multiple Ranges
Multiple ranges allow for the determination of inorganic nitrogen in concentrations from ppb to %.
Analog Output
The 0-1V analog output signal can be connected to a chart recorder or the Timberline data acquisition system.
Theory of Operation
The Timberline Model TL-2800 Ammonia/Nitrate Analyzer is based on the principle of gas diffusion across a membrane coupled with electrical conductivity measurement as first described by Carlson.1
The 8-roller peristaltic pump directs the sample, caustic, and absorbing solutions into the diffusion cell. Within the cell, the sample is mixed with a caustic solution. The resulting solution has a pH sufficiently high (pH 11-13) to convert virtually all of the ammonium ion present in the sample to dissolved ammonia gas. This sample/caustic solution flows past one side of a membrane that is permeable to gases but not to liquids or ionic species. The dissolved ammonia gas in the sample / caustic mixture will diffuse across the membrane.
On the other side of the membrane, a buffered solution2 absorbs the diffused ammonia gas. The buffered solution then flows into the conductivity detector. The flow passes through a low volume heat exchanger to establish thermal equilibrium of the solution before it reaches the conductivity cell. The conductivity cell measures the change in electrical conductance of the absorbing solution. This change is proportional to the concentration of ammonium in the original sample. Passing the sample/caustic mixture through an optional zinc reduction cartridge reduces nitrate and nitrite ions to ammonium, allowing measurement of the total inorganic nitrogen concentration.3
1Carlson, R.M.; Anal. Chem., 50(1978) 1528.
2Patent # 6090267
3Carlson, R.M.; Anal. Chem., 58(1986) 1590.
The Ammonia / Nitrate Analyzer Includes
A highly-sensitive Conductivity Detector, with active temperature control to maintain baseline stability.
A Diffusion Membrane Cell to selectively transfer ammonia from the sample to the absorbing solution via a tubular membrane.
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Integrated data acquisition system.
An 8-roller Peristaltic Pump to deliver all samples & reagents.
A complete Accessory Kit including reagent delivery bottles to safely store and deliver reagents.
Product Specifications
Dimensions | 6.375"H x 17"W x 13"D |
Weight | 20 Lbs |
Principles of Operation | Membrane Diffusion / Conductivity detection |
Concentration Range | 20 ppb to 1000 ppm |
Sample Rate | Up to 1 per minute |
Required Reagents | NaOH or KOH, DTPA, Deionized Water, Boric Acid, NH4OH |
Output | 0-1V Analog |
Flow Path Wetted Parts | Polymers, PVC (PEEK & Tefzel), SS, Electrodes-gold plated |
Power Supply | 120 VAC 60Hz or 240 VAC 50Hz |
Ordering Information
TL-2X00 Ammonia/Nitrate Analyzer | Catalog Number |
Single Channel TL-2800, 120 VAC | 2800-1 |
Single Channel TL-2800, 240 VAC | 2800-2 |
Dual Channel TL-2900, 120 VAC | 2900-1 |
Dual Channel TL-2900, 240 VAC | 2900-2 |
Auto Samplers | Catalog Number |
Cetac ASX-260, 120 Tube, 120/240 VAC | 2712 |
Cetac ASX-510, 240 Tube, 120/240 VAC | 2724 |
Timberline, 11 tube, 120 VAC | 2305-1 |
Timberline, 11 tube, 240 VAC | 2305-2 |
Data Acquisition and Recorders | Catalog Number |
Ross Strip Chart Recorder | 2750 |
Nitrate Accessories | Catalog Number |
Replacement Zinc Cartridge (Box of 10) | 2001 |
Pump Accessories | Catalog Number |
Replacement Pump Cartridge | 2004 |
Pump Tubing, 0.089mm ID, 12/pkg | 2081 |
Pump Tubing, 1.42mm ID, 12/pkg | 2082 |
Replacement Diffusion Membranes | Catalog Number |
Standard Sensitivity | 2050 |
High Sensitivity | 2010 |