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RA-4500

RA-4500

Fully Automated Reducing-Vaporization Mercury Analyzer

Sensitive, accurate, efficient

RA-4500 is a Fully Automated In-Situ Acid-Digest Reducing Vaporization-CVAAS mercury analyzer from NIC, which is specifically designed and engineered to provide a Seamless Start to Finish of mercury analysis for aqueous sample, incorporating the sample acid-digestion procedure.

Applications

Suitable for a wide variety of pre-digested sample solutions, aqueous samples, including drinking water, industrial wastewater, river water, lake water, seawater and rain-runoff

Methods

USEPA 245.1  |  USEPA 245.2  |  USEPA 245.5  |  USEPA 7470A  |  USEPA 7471B  |  ASTM D 3223-17  |  EN-1483  |  APHA 3112  |  JIS K0102  |  ISO 12846 and more

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Why Seamless Start to Finish?

To perform total mercury measurement, a sample solution must be first pre-digested and pre-oxidized to break down the complex mercury matrices, releasing all bounded organic mercury, and oxidizing all forms of mercury into stable ionic mercury before Reducing Vaporization and CVAAS measurement takes place.

Sample digestion and oxidation processes are often:

Time-consuming & labor intensive

According to EPA & APHA methods, it takes 2 hours for the sample solution to oxidize fully.

Tedious & hazardous

Multiple acids and oxidants are used for this process.

Machine versus Human

Manual handling and transfer is prone to mistake and error.

Specifically designed and engineered to provide peace of mind, all these problems are overcome by the superior features of RA-4500.

Features

Fully Automated Sample Digestion - First of Its Kind

RA-4500 is one of the ground-breaking mercury analyzers in the market. Incorporating NIC's cutting-edge innovation and engineering, RA-4500 manages to automate the entire sample digestion and analysis process with compliance with regulatory methods such as EPA and APHA. It comes with programmable software where users can program up to 10 steps of sample digestion steps with proportionally reduced usage and consumption of reagents.

Minimum Memory Effect & Contamination
– Non-Contact LED Sensor

As RA-4500 automates the sample digestion process, it involves the use of Potassium Permanganate (KMnO4) which is supposed to be added in excess for complete oxidation. Unlike the conventional method, RA-4500 is equipped with a built-in LED Sensor to verify the excess KMnO4 without direct contact with the sample solution. Thus, the cross-contamination issue at this stage is avoided completely.

Superior Detection Limit and Sensitivity
– Detection Limit Down to 0.5 ppt

RA-4500 is equipped with a Non-Dispersive CVAAS, which has a detection limit of down to 0.5 ppt (5 ppt including sample digestion process) with excellent accuracy and precision. With this superior detection limit and excellent precision, it provides a wide range of applications to be analyzed in RA-4500, such as river water, lake water, industrial discharges, etc., easily satisfying all wastewater/effluent discharge guideline and regulations in most countries.

High Productivity
- Autosampler with 80 Positions

RA-4500 is equipped with an autosampler of 80 positions which maximizes the throughput of any fast-paced laboratory, providing results with the shortest turnaround time possible.

Effective & Complete Digestion Process
– Precise Thermal Control

The autosampler tray in RA-4500 is integrated with an innovative solution – a state-of-art Infrared Heating Technology, which provides rapid heating under stable temperature control.

An effective and complete digestion process is crucial to obtain an accurate total mercury measurement as this process ensures all organic mercury is oxidized and converted into ionic mercury. This can only be achieved by having stable and precise temperature control.

Lower Operation Cost

NO Carrier Gas Required

Almost all CVAAS requires purified carrier gas such as nitrogen or argon to operate, which incur facility and extra cost of operation. In RA-4500, there is no carrier gas required which lowers down laboratory operation cost and ease of setting up.

Reduced Consumption of High Purity Reagents

When it comes to trace level of mercury analysis, the purity of the reagent plays a vital role in having minimum interference to the analyte measurement. Consumption of high purity reagents is inevitable; thus, operating cost is high. For RA-4500, since the sample size is less (5mL), all reagents used are reduced proportionally. It has built-in reagent pumps that are incredibly robust and reliable to deliver reagents with high consistency. Thus, every measurement can be performed with accuracy and precision, with reagents consumption saving up to 50%.

How Does it Reduce Reagent Consumption?

Discrete-Direct-Purge Technique of Reducing Vaporization

Generally, there are two methods of Reducing Vaporization, i.e.,

  • Flow Injection Technique
  • Discrete-Direct-Purge Technique.

All mercury analyzers in NIC employ Discrete-Direct-Purge Technique to minimize memory effect from mercury which causes cross-contamination issue.

Differences between NIC Discrete-Direct-Purge Reducing Vaporization and other reducing vaporization techniques

RA-4300FG+

Ultra-trace level mercury solution for samples like rain water, sea water and more.

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How Does it Reduce Reagent Consumption?

Less Reagent Consumption, Less Waste Generation Compared to Flow-Injection Technique

Generally, the flow-technique system continuously pumps and flows the reagents through the system to stabilize the dynamic flow to get a consistent flow (sample) volume which is crucial for precise quantification purposes. Secondarily, the reagents used for the analysis are pumped continuously through the system to clean the flow paths and obtain a constant background. Overall, multiple milliliters per minute of liquids are used and generated as waste.

In discrete-direct-purge technique, much lesser reagents are consumed. This technique uses a fixed volume of reagents per sample analysis. Typically, only just 0.3 milliliter of reductant (SnCl2) is consumed per run.

Less usage of reagents which are generally acidic, generates less hazardous waste for disposal, saving the operating cost in both ways.

Similarly, for sample solution, NIC reducing vaporization normally uses fixed 5mL sample volume for analysis. As for flow technique, sample solution is continuously pumped through the system to complete the reaction with the reductant. Depending on the flow rate setting, typically each analysis generates between 7 to 10mL of liquid waste.

Differences between NIC Discrete Direct-Purge Reducing Vaporization and other reducing vaporization techniques

NIC’s Discrete Direct-Purge Reducing Vaporization

In this technique, the mercury analyzer handles each sample in a Discrete, independent sample tube. Each sample is therefore isolated from surface contact with any other samples in the analytical batch to be measured.

The Direct-Purge technique is then used to extract and transfer the converted Hg0 from each sample tube and into the detector for measurement. Since only mercury vapor contacts the flow path, sample-to-sample memory effects and carryover from over-range samples are virtually eliminated.

How It Works

  • First, reductant (SnCl2) is automatically added into the sample tube containing the acid-digested sample solution. The sample tube is sealed, leaving a closed-loop flow path to the detector.
  • The carrier gas is introduced to sparge (or purge) the solution, releasing the elemental mercury vapor from the solution and into the flow path, which then flows directly into the detector for measurement.

Advantages

  • Almost no sample-to-sample carryover or memory effect
  • Carryover from over-range samples is greatly reduced
  • Discrete technique only needs 200-300uL of reagent per sample
  • Reduces hazardous mercury wastes to less than one liter per full day of operation
  • Filtration of samples not required, as Direct-Purge technique can handle particulates in samples with no issues

Other Reducing Vaporization Techniques

  • Commonly based on Flow-Injection or Continuous-Flow Techniques to introduce the full sample solution into the system to complete the chemical reaction for the analysis.
  • The acidic sample solutions and reductant (SnCl2) enter the system via pump tubing with peristaltic pumping, which must be replaced often.
  • Chemical reduction begins when both the sample solution and reductant are mixed, reducing Hg2+into Hg0, within a continuous flow of reagents.
  • Prior to the detector, the liquid-gas phase separator or membrane separation device is needed to remove the liquid, allowing the Hg0gas to enter the detector.

Mercury is well-known for its strong affinity to absorb onto different materials and its high solubility in acidic reagents.

After the digestion and oxidization procedure, samples are usually very acidic. The acidic sample solutions and reductant, SnCl2, enter the system via pump tubing with peristaltic pumping. The acidic sample leaves a residue on the inner surface of pump tubing, creating possible active sites for mercury absorption from current mercury, which is easily passed on to the following samples.

Such phenomenon is inevitable with this technique and commonly exhibits as what is called the mercury memory-effect, experienced by many lab analysts. This effect is especially significant and severe when analyzing samples of varying mercury concentration levels.

Large multi-liter carboys of hazardous waste are produced daily from such flow-based techniques, creating the need for expensive waste disposal. Reduction of hazardous mercury wastes should be a priority for all mankind, and it is a priority of the Minamata Treaty. 

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