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RA Series


Reducing-Vaporization Mercury Analyzer

Compact, precise and accurate

RA-5A is a simple, standalone, and modular type of Reducing Vaporization-CVAAS mercury analyzer with ultra-high sensitivity and excellent precision in the smallest platform. It is also designed and engineered to have the flexibility to upgrade its autosampler according to customers’ needs.


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


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


Small Footprint with Superior Performance – An A4 Size CVAAS with 0.5 ppt Detection Limit

RA-5A occupies a size as big as an A4 paper. It certainly saves space for space-conscious laboratories. Compact RA-5A does not compromise its performance. With the innovative detector optics, it can achieve a detection limit as low as 0.5 ng/L with 5 ml sample volume and excellent precision with measurement of 0.05 µg/L at CV of 2.2%.

RA-5A Mercury Analyzer
RA-5A feature

Superior Repeatability & Accuracy

Compact RA-5A comes with impressive repeatability & accuracy.

Superior Reducing Vaporization by Discrete-Direct-Purge Technique

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

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

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

Lower Operation Cost – No Carrier Gas Required & Reduced Consumption of High Purity Reagents

Unlike other CVAAS, RA-5A does not require any carrier gas for its operation. Self-generating filtered purified ambient air is employed as carrier gas within RA-5A.

When comes to trace mercury analysis, purity of the reagents plays a vital role in having minimum background that interferes with the target analyte measurement. Consumption of reagents directly relates to the daily operating cost. For RA-5A operation, reagents do not flow continuously, unlike those flow-technique systems. Each reagent is dosed in specified amount directly into each sample solution contained in individual sample tube. Reagent consumption saving up to 50%. With less reagent used, less hazardous waste (containing acids and reagents) is generated, saving more on disposal cost.

Flexible & Cost-Effective Configuration – Various Autosampler Options

As the RA-5A has a low cost of ownership, it is affordable, and its capacity can be upgraded whenever necessary.
There are a few levels of automation and options of autosampler available, depending on the customers’ needs.

RA-5A Standalone
– Model 5100A (5 mL)

RA-5A Mercury Analyzer

RA-5A with Auto Reagent Dispenser RD-5 – Model 5200A

RA-5A Mercury Analyzer

RA-5A with Auto Reagent Dispenser RD-5 and Sample Changer SC-5 (5 mL) – Model 5300A

RA-4300A Mercury Analyzer


Fully equipped CVAAS with outstanding features for all laboratory demanding needs for mercury measurement

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Other Series

MA Series

A state-of-the-art Direct Mercury Analyzer

  • No sample digestion needed
  • Fast analysis time
  • Highly accurate
  • Solid , liquid, gaseous matrices

PE Series

In full compliance with UOP-98-20, PE Series can fulfill all analysis requirements of liquid hydrocarbon samples.

WA Series

Mercury analyzer for ultra-trace level analysis in gaseous matrices. Featuring Dual Gold Amalgamation technique and various capacity options.

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.


  • 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

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 the 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, the 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.

Standalone RA-5A

Standalone RA-5A is provided with a 5 mL impinger set. Impinger set can be upgraded to 20 mL or 250 mL.


All types of water samples and chemically decomposed digestates.

How Does It Work?

  • An acid-digested and oxidized sample solution is added into the sample tube, followed by manual addition of SnCl2 and H2SO4 to convert all ionic mercury into elemental mercury.
  • A stream of self-purified air purges through the sample solution, liberating elemental mercury and the analyte is transported to CVAAS in RA-5A for measurement.
  • Available for larger size impinger set (20 mL & 250 mL) for expanded sample volume analysis to better detection limits.
RA-5A Mercury Analyzer

5 mL Impinger Set

RA-5A Mercury Analyzer

20 mL Impinger Set

RA-5A Mercury Analyzer

250 mL Impinger Set

Note: To measure Total Mercury from the aqueous sample, the sample must be digested chemically to break down organic mercury before reducing vaporization takes place. Without sample digestion, only the Hg2+ and Hg0 can be measured with this technique.

RA-5A Mercury Analyzer

RA-5A with Auto Reagent Dispenser RD-5 – Model 5200A

Better automation with Reagent Dispenser for automatic dispensing of acid H2SO4 and reductant SnCl2.

  • An acid-digested and oxidized sample solution is added to the sample tube. Reagent Dispenser, RD-5, dispenses both the SnCl2and H2SO4 precisely into the sample tube to ready for the reduction process.
  • A stream of self-purified air purges through the sample solution, liberating elemental mercury and the analyte is transported to CVAAS in RA-5A for measurement.

Use with standard 5 mL (Glass) impinger set (option for 20 mL or 250 mL).

RA-5A Mercury Analyzer

RA-5A with Auto Reagent Dispenser RD-5 and Sample Changer SC-5 (5 mL) – Model 5300A

Reagent Dispenser (RD-5)

  • Use with a Reagent Dispenser (RD-5) for SnCl2, H2SO4 and auto-H2O rinse for bubbler in between sample sequence.

Sample Changer (SC-5)

  • Equipped with 30-positions of 5mL sample tube.
  • Choice for 12-positions of 20 mL or 5-positions 100/250 mL, with quick-swap tray and impinger head are available.
  • All sample tubes are of borosilicate glass
RA-5A Mercury Analyzer

12-Positions – 20mL sample size

RA-5A Mercury Analyzer

5-Positions – 100mL / 250mL sample size