Atomic Absorption Spectrometer

Atomic Absorption Spectrometer

Test Application
Medical Testing
Cannabis Testing
Analytical Instruments
Spectroscopy Instruments

Atomic absorption spectroscopy (AAS) is used to analyze metal samples by determining the presence and concentration of metals in a liquid sample. Metals include Fe, Cu, Al, Pb, Ca, Zn, Cd and many more. It also measures the concentrations of metals in the samples. Typical concentrations range in the low mg/L range.

In their elemental form, metals will absorb ultraviolet light when they are excited by heat. Each metal has a characteristic wavelength that will be absorbed. The AAS instrument looks for a particular metal by focusing a beam of UV light at a specific wavelength through a flame and into a detector. The sample of interest is aspirated into the flame. If that metal is present in the sample, it will absorb some of the light, thus reducing its intensity. These instruments measure the change in intensity. A computer data system converts the change in intensity into an absorbance.

 

Applications

The following applications are typical uses for AAS analysis, along with industry examples where this type of testing would be performed:

  • Checking for concentrations in finished goods
    •  Petrochemical – Impurities in gasoline: Fe, Mn, or Pb
    • Manufacturing/Metallurgy – Alloying element concentrations: Ag, Au, Ca, Cu, Fe, Ni, Pb, Zn, etc.
  • Measuring heavy/toxic metal content in products for human or animal consumption
    •  Medical – Cd, Pb, Ca, Fe, Zn
    • Pharmaceutical – Cr, Pb, As, Cd, Cu, Hg
    • Food – Pb, Cd, Cr, Ca, Cu, Fe, Ge, Mg, Mn, Na, Ni, Sb, Sn, or Zn
    • Water Treatment – Cd, Cu, Fe, Pb, Zn
    • Fodder/Animal Feed – Ca, Cu, Fe, K, Mg, Mn, Zn, Cd, Co, Cr, Pb
  • Metal content in soil/ore samples
    • Geological/Mining – Ag, Au, Ca, Cu, Fe, Ni, Pb, Zn, etc.
Features/Advantages

Features

  • Auto-ignition, and automatic selection of spectral bandwidth
  • Fully automated wavelength scanning and peak identification (not present in WFX-130 models, manual option only)
  • Automatic hollow cathode lamp changeover during multi-element analysis
  • Automatic changeover and position optimization of integrated flame/graphite furnace atomizer
  • Light-controlled graphite furnace power supply, utilizing fuzzy PID temperature control with dual curve working mode. This ensures rapid heating to a stable and accurate temperature and guarantees good temperature reproducibility. The software includes a temperature auto-correction function
  • Graphite furnace with pneumatic control and pressure lock ensures constant pressure and reliable contact
  • The patented oxygen-enriched air-acetylene flame instead of the traditional nitrous oxide/acetylene flame for high-temperature element analysis up to 2950ºC (Only available on WFX-110 and WFX-210 models)
  • High-performance hollow cathode lamps (HP-HCL) are available for increased sensitivity (~20%) of results or where metal concentrations are expected to be extremely low (not available for WFX-130 models)
  • Easy-to-use and flexible Windows OS with multi-window processing technology to allow the operator to observe the signal profile, measured results, and calibration curve all at the same time. Various analytical programs, data, signals, and images can all be stored for later use
  • Advanced safety features
    • Alarm and automatic safety protection to fuel gas leakage, insufficient air pressure, abnormal flame extinction, argon pressure deficiency, insufficient cooling water supply, and high temperature/current (during graphite furnace analysis)
    • Spray chamber made from explosion-proof material
    • All-titanium burner and stopper for flame analysis

Advantages

  • Simple operation and collection of data
  • Wide range of elemental analysis
Theory/Method

Atomic absorption spectroscopy (AAS) is performed by focusing a beam of ultraviolet (UV) light of a known wavelength through a flame and into a detector. The liquid sample of interest is atomized into a gaseous state and aspirated into the flame (solid samples. In their elemental form, metals will absorb UV light when they are excited by heat. Each metal has a characteristic wavelength that will be absorbed, and the absorbance is proportional to the concentration of the analyte in the sample. The detector measures the change in intensity of the UV beam and a computer converts the change in intensity into a concentration for that element.

Technical Specifications

General Specifications

Wavelength Range

190 – 900 nm

Wavelength Accuracy

Better than 0.25 nm

Resolution

Two spectral lines of Mn at 279.5 nm and 279.8 nm can be separated with the spectral bandwidth of 0.2nm, and valley-peak energy ratio less than 40% (30% for WFX-210)

Baseline Stability

0.004 Abs / 30 min

Background Correction

The D2 lamp background correction capability at 1 Abs is better than 30 times

The S-H background correction capability at 1.8 Abs is better than 30 times

Light Source System

Lamp Turret

WFX-130 – 4-lamp turret, auto-alignment, automatic fine adjustment, manual wavelength selection, peak picking

Other models – 6-lamp turret (2 high performance HCLs can be mounted to increase sensitivity of flame analysis), auto-alignment, automatic fine adjustment, fully automated scan and peak-picking

Lamp Current Adjustment

Automatic adjustment and display

Wide pulse current: 0 – 25 mA

Narrow pulse current: 0 – 10 mA

Lamp Power Supply Mode

Powered by two pulses simultaneously

Optical System

Monochromator

Single beam, Czerny-Turner design grating monochromator

Grating

1800 l/mm

Focal Length

277 mm

Blazed Wavelength

250 nm

Spectral Bandwidth

0.1 nm, 0.2 nm, 0.4 nm, 1.2 nm, automatic switchover

Atomizer

Flame/Graphite Furnace

Automatic ignition

Flame & graphite furnace atomizer automatic changeover, automatic graphite furnace position optimization, automatic flame height setting and horizontal position optimization
Automatic gas flow setting for WFX-210

Alarm and automatic protection functions for gas leak, abnormal flow, insufficient air pressure, abnormal flame extinction

Flame Analysis

Burner

10 cm single slot all-titanium burner

Spray Chamber

All-plastic spray chamber

Nebulizer

High efficiency glass nebulizer with metal sleeve

Characteristic Concentration and Detection Limit

Air-C2H2 Flame

Cu calibration:
Characteristic concentration ≤ 0.025 mg/L

Detection limit ≤ 0.006 mg/L

Oxygen-Enriched Air-C2H2 Flame

Ba calibration:
Characteristic concentration ≤ 0.22 mg/L

Al calibration:

Characteristic concentration ≤ 0.4 mg/L

Graphite Furnace Analysis

Temperature Range

Up to 3000ºC

Light-Controlled Temperature Range

1500ºC - 3000ºC, temperature auto-correction

Temperature Control Accuracy

≤ 1%

Heating Rate

2000ºC/s

Characteristic Mass

Cd ≤ 0.5 (10-12g), Cu ≤ 5 (10-12g), Mo ≤ 1 (10-11g)

Precision

Cd ≤ 3%, Cu ≤ 3%, Mo ≤ 4%

Safety Protection

Protections for over-heating, over-current, insufficient cooling water, and argon pressure monitoring

Graphite Furnace Autosampler

Sample Tray Capacity

55 sample cups and 5 cups for matrix modifier

Sample Cup Material

Polypropylene

Standard Cup Volume

3 mL for sample, 20 mL for matrix modifier

Number of Repeatable Measurements

Up to 99 times

Sampling System

100 µL and 5 mL injectors, large flow sampling nozzle rinsing

Sampling Precision and Repeatability

Precision: 1%

Repeatability: 0.3% for minimum sampling volume

Auto-Correction

Sampling nozzle auto-correction, sample cup height auto correction

Detection and Data Processing System

Detector

Photomultiplier with high sensitivity and wide spectral range

Software

Windows OS

Analytical Method

Working curve method (1st order and 2nd order fitting) with automatic sensitivity correction; standard addition method

Concentration

Auto-calculation of concentration and content

Repeatable Measurement

Repeated measurement of up to 99 times, automatic calculation of mean value, standard deviation, and relative standard deviation

Multi-Task Functions

Sequential measurement for multi-element determination within the sample (maximum 6 elements, depending on model)

Condition Reading

With model function

Result Printing

Measurement data and final analytical report printout, editable with Excel