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Wen's Research Group
Gas chromatography (GC) provides a quantitative analysis of volatile and semi-volatile organic compounds found in a variety of matrices (gases, liquids and solids) in foods, medical materials, plastics, environmental samples and occupational monitoring samples.
Concentrations of many metals are determined by Inductively Coupled Plasma (ICP) by mass spectrometry (MS). The ICP is used to ionize the sample while the mass spectrometer is used to separate and quantify those ions. Calibrating the instrument with known standards allows for an unknown sample to be quantified.
The Shimadzu TOC-L uses a high-temperature combustion method to analyze aqueous samples for TOC and non-purgeable organic carbon (NPOC). Samples are treated with sulfuric acid to reduce the pH and sparged with ultra-pure carrier grade air to drive off inorganic carbon. High-temperature combustion (680 °C) on a catalyst bed of platinum-coated alumina balls breaks down organic carbon into carbon dioxide (CO2). The CO2 is carried by ultra-pure air to a non-dispersive infrared detector (NDIR) where CO2 is detected. The method used is SM5310B.
Water quality parameters: pH, Turbidity, Hardness, Conductivity, Acidity, Alkalinity, TOC, TDS, TSS.
Cations: Ca2+, Mg2+, Fe2+/Fe3+, NH4+, and other common heavy metals
Anions: NO2-, NO3-, SO42-, PO43-, Cl-, HS-/S2-
- Toxicity
Different series of Multi-Parameter Kits (Hach USA)
Widely found in natural waters, sulfate may be at high levels in mine drainage. High concentrations of magnesium or sodium sulfate in water act as cathartics. This test kit provides economical determination of sulfate levels using the Extinction/Turbidimetric methods.
- HPLC
A pH meter is used. Hydroxyl ions present in a sample as a result of dissociation or hydrolysis of solutes react with additions of standard acid. Alkalinity thus depends on the end-point pH used. pH greater than 7 means substance is an alkaline.
- Chlorine
For determination of reactive (ortho) phosphate (phosphorus) by the PhosVer® 3 ascorbic acid method. USEPA accepted for reporting for wastewater analysis using Hach Method 8048, Phosphorus, Reactive. Also used in acid-hydrolyzable and total phosphorus determination, after appropriate digestion.For determination of low range nitrite by the NitriVer® 3 diazotization method. USEPA accepted for reporting wastewater analysis using Hach Method 8507.
Time-resolved pH and redox monitoring meters are available.
TCLP or Toxicity Characteristic Leaching Procedure is a chemical analysis process used to determine whether there are hazardous elements present in a waste.
First, separation of liquid wastes: Liquids (containing less than 0.5% dry solid material) are filtered through glass fiber to create a TCLP extract. Wastes (containing 0.5% or greater dry matter) are separated and stored for later analysis. Second, particle size reduction: Using a standard 9.5 mm sieve, we filter solid material and prepare it for extraction by cutting, crushing or grinding to a particle size of 1 cm or less. Third, extraction of solid material: The solid material is then extracted for at least 18 hours with a slightly acidic fluid equal to 20 times its weight. The materials are placed in a tumbler to simulate the leaching action of water seeping through waste in the landfill. Fourth, final separation: The liquid waste is then separated from the solid waste through a fiberglass filter. The solid material is discarded and the liquid components are then assessed. The initial liquid components may be added or may be analyzed separately, depending on compatibility. Last, TCLP testing analysis: Lastly, we identify and quantify all inorganic and organic materials using EPA-approved methods.
Often the unicellular green algae is used to indicate toxicity. This method measures the inhibition of cell division caused by toxic substances. At high toxic concentrations, algaes can die. Hence, new algaes have to be stored and kept in stock to ensure further toxicity measurements after a toxic effect. The algae test takes 72 hours and the supply of the test organisms must be secured by purchase or breed.
- TOC - Total Organic Carbon and total nitrogen
- Nitrate/nitrite and ammonia test kits
EDTA Titrimetric Method- EDTA forms a chelated soluble complex when added to a solution of certain metal cations. If a small amount of dye is added to a solution containing calcium and magnesium ions at a pH of 10 ± 0.1, the solution turns wine red. If EDTA then is added as a titrant, the calcium and magnesium are complexed. When all of the calcium and magnesium are complexed, the solution turns from wine red to blue.
- Chloride
For determination of low range nitrite by the NitriVer® 3 diazotization method. USEPA accepted for reporting wastewater analysis using Hach Method 8507.
- Turbidity
- TCLP
- Phosphorus
A turbidity meter, a long device, is lowered into the water and at the end is a turbidity sensor. It reads turbidity in the water by shining a light into the water and reading how much light is reflected back to the sensor. These devices can house multiple water-quality sensors, such as a conductivity sensor to measure electrical conductance of the water, which is strongly influenced by dissolved solids, and a temperature gauge.
For determination of Chemical Oxygen Demand (COD) by the Reactor Digestion method. US EPA approved for wastewater analysis using Hach Method 8000.
- Alkalinity
- Sulfate
Typical environmental sample analysis
- BOD & COD
A small volume of filtered sample is introduced into an ion chromatograph (IC). The sample is pumped through a precolumn, separator column, suppressor column, and conductivity detector. Anions are separated in the precolumn and separator column based on their affinity for resin exchange sites in the columns. The suppressor column converts the sample anions to their acid form. The separated anions are measured by the conductivity detector. The concentration of anions is determined by comparing peak heights of unknowns to a calibration curve generated from known standards.
- Acidity/pH
- Heavy Metal
A small volume of filtered sample is introduced into an ion chromatograph (IC). The sample is pumped through a precolumn, separator column, suppressor column, and conductivity detector. Anions are separated in the precolumn and separator column based on their affinity for resin exchange sites in the columns. The suppressor column converts the sample anions to their acid form. The separated anions are measured by the conductivity detector. The concentration of anions is determined by comparing peak heights of unknowns to a calibration curve generated from known standards.
- Gas Analysis
The Shimadzu TOC-L is used to determine Total Inorganic Carbon (TIC), and carbonate alkalinity is calculated from the TIC concentration. A measured volume is pulled into the sampling syringe and injected with 1N HCl, and the released CO2 is carried by ultra-pure air to a non-dispersive infrared detector (NDIR) where CO2 is detected.
- Hardness
Wen Zhang, Ph.D., P.E., BCEE
Principal Investigator
Professor
Phone: (973) 596-5520
Fax: (973) 596-5790
Email: wen.zhang@njit.edu
Office Location: Colton Hall 211
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