DMA-80 Direct Mercury Analyzer

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DMA-80

Direct Mercury Analyzer

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Introduction

• Mercury in the atmosphere can be from manmade sources

(coal-fired power plants, municipal incinerators, industrial boilers) or from natural sources (forest fires, geologic formations,

volcanoes)

• Precipitation is the primary mechanism for transporting

airborne gaseous or particulate mercury from the atmosphere to surface water and land

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Milestone Srl 5 Aqueous samples and extracts ASV 7472 Solid or semi-solid waste CV-AAS 7471A Liquid waste CV-AAS 7470A Sample type Technique Method

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CV-AAS

• Cold Vapor-Atomic Absorption Spectroscopy

– Samples are digested or dissolved

– Mercury is reduced to free atomic state by using tin (II) chloride or sodium boro-hydride in a closed

reaction vessel

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CV-AAS

Few minutes AAS Analysis Mercury reduction 1 hour Interference removal Wet chemistry 20 minutes- 1 hour Closed vessel microwave 2 hours- 2 days Hot plate

Sample acid digestion

Time Description

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CV-AAS and ASV

• Both methods require sample digestion and

further wet chemistry

• Sample digestion can be problematic because

of Hg volatility

• Sample preparation is the bottleneck for higher

analytical productivity

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DMA-80

Direct Mercury Analyzer

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DMA-80 Advantages

• Direct Hg determination at trace level on solid

and liquid samples

• No sample digestion step

• No wet chemistry pre-treatment step

• Fast, approximately 6 minutes per sample

• Eliminates waste disposal

• Validated results (US EPA method 7473) for

solid and liquid matrices

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DMA-80

Principle of operation

• Solid or liquid samples are weighed and introduced in the DMA-80

• The sample is initially dried and then thermally decomposed in a oxygen flow

• Combustion products are carried off and further decomposed in a hot catalyst bed

• Mercury vapors are trapped on a gold amalgamator and subsequently desorbed for quantitation

• The mercury content is determined using atomic absorption spectrophotometry at 254 nm

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DMA-80

• Major components

– Sample dosing system

– Thermal process furnaces

– Atomic absorption spectrophotometer – System controller

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Sample Dosing System

• Built-in 40 position auto-sampler for high

throughput unattended operation, for solid and

liquid samples

• Maximum sample weight 500 mg

• Maximum sample volume 500 µl

• Possibility of multiple sample dosing for Hg

pre-concentration on amalgamator

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Thermal Process

12 s 0-30 s 900°C 850-950°C Amalgam 600°C 550-650°C Catalysis 180 s 0-420 s 850°C 800-1.000°C Decomposition 60 s 0-300 s 300°C 20-300°C Drying Typical time Time range Typical temperature Temperature range Step

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Oxygen

“Research” grade (O₂> 99,95%) Purity 200 ml/minute Flow rate 4 bar (60 psig) Inlet pressure

Carrier and decomposition gas

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Atomic Absorption

Spectrophotometer

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AAS Technical Data

Si-photodiode sensor Detector 254 nm, 9 nm bandwidth Interference filter 253,65 nm Wavelength

Low pressure mercury lamp Light source

Single beam spectrophotometer with sequential flow through of

measurement cells Instrument optics

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DMA-80

Performance Specifications

(1)_{Sample weight 100 mg}

(2)_{Automatic switching when absorbance 0,8}

0,2 0,02 Detection limit (1st_{) 0,2-350} (2nd_{) 350-6.000} (1st_{) 0,02-35} (2nd_{) 35-600} Working range(2) Hg concentration(1) (µg/kg) Total Hg (ng) Data

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DMA-80

Performance Specifications

6 minutes Typical analysis time

< 1,5% Typical reproducibility

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System controller

• Lab TERMINAL

– Touch-screen Pentium-based controller, 266 MHz, 64 MB Ram, Windows 98, Color 12,1” TFT SVGA

monitor, CD-ROM, FD, Smart Card Reader, 2 COM, 1 USB, LAN ports

• Standard bench-top computer with similar

specifications

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Terminal 1024

• 12” large high resolution color screen controller

• “Touch control” display

• Supplied with keyboard and mouse

• “EasyControl” software for a complete control of all reaction parameters

• Optional “EasyDoc” software for data export on external computer

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EasyControl Software

• Evolution of previous Windows™ based DMA-80

software

• Selectable calibration algorithm

• Virtually unlimited memory for programs and

actual data storage

• Built-in service and diagnosis functions

• CFR-21 part 11 compliant

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Mercury Trap

• Optional mercury trap to be located at DMA-80 outlet

• Activated charcoal • Safe operation

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DMA-80

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Getting Started

• Oxygen cylinder with gas regulator stable at 4 bar (60 psig)

• Power 115-230 V/50-60 Hz

• Analytical balance with serial interface • Windows compatible printer

• Standard reference materials • Aqueous standards

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DMA-80 Calibration

• Liquid standards

– Different concentrations, same volume – Same concentration, different volumes

– Use fresh standards, stabilized with HNO₃ or HCl/K₂Cr₂O₇

• Solid standards

– Certified mercury content – Vary by weight

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Calibration 1

st

Cell

0,6% 0,7223 30 ng 1,2% 0,4996 20 ng 2,2% 0,2549 10 ng 1,5% 0,1272 5 ng 16,7% 0,0012 Blank RSD (n=3) Absorbance Solution

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Calibration 2

nd

Cell

0,9% 0,7285 500 ng 1,9% 0,3117 200 ng 2,2% 0,1546 100 ng RSD (n=3) Absorbance Solution

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Certified Reference Materials

6.250 ± 190 NIST 2711 Soil

1.400 ± 80 NIST 2709 Soil

141 ± 19 NIST 1633b Fly Ash

93,8 ± 3,7 NIST 1630a Coal

34 ± 4 NIST 1573a Tomato Leaves

5,8 ± 0,5 NIST 1568a Rice Flour

Hg content (µg/kg) Sample

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NIST 1568a Rice Flour

2,0 3,0 4,0 5,0 6,0 7,0 8,0 Hg (µ g/ kg ) Certified DMA-80

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NIST 1573a Tomato Leaves

24,0 28,0 32,0 36,0 40,0 Hg (µg/ kg ) Certified DMA-80

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NIST 1630a Coal

80,0 85,0 90,0 95,0 100,0 Hg (µ g/ kg ) Certified DMA-80

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NIST 1633b Fly Ash

100,0 120,0 140,0 160,0 180,0 Hg (µ g/k g ) Certified DMA-80

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NIST 2709 Soil

1,0 1,2 1,4 1,6 1,8 Hg (m g /k g ) Certified DMA-80

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NIST 2711 Soil

5,8 6,0 6,2 6,4 6,6 Hg ( m g /k g ) Certified DMA-80

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Fresh Salmon

56,2 0,2992 5 58,0 0,3404 4 57,8 0,2330 3 54,1 0,2296 2 55,4 0,2849 1 Hg (µg/kg) Weight (g) Run

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Fresh Salmon

5 N 1,6 Sd (µg/kg) 56,3 Average (µg/kg)

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Detection Limit

The detection limit is defined as the concentration which will give an absorbance signal of two (sometimes three) times the magnitude of the baseline noise. The baseline noise may be statistically quantified typically by making ten or more replicate measurements of the baseline

absorbance signal observed for an analytical blank, and determining the standard deviation of the

measurements. The detection limit is then defined as the concentration which will produce an absorbance signal twice (or three times) the standard deviation

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Detection Limit

0,0006 10 0,0007 5 0,0008 9 0,0008 4 0,0010 8 0,0006 3 0,0008 7 0,0010 2 0,0010 6 0,0007 1 Absorbance Run Absorbance Run

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Detection Limit

0,02 ng DL 0,000468 3*Sd 0,000156 Sd 0,0008 Average

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DMA-80 Memory Effect

0,4 0,0097 (1st₎ Blank 2 1,5 0,0374 (1st₎ Blank 1 500 (set) 0,7285 (2nd₎ Standard 500 ng Mercury content (ng) Absorbance Sample

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Quartz Boats

• Analysis of liquids with DMA-80 autosampler • Improved performance

– Lower memory effect – Better reproducibility

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Quartz vs. Metal Boats

0 0,1 0,2 0,3 0,4 1 2 3 4 5 6 7 8 9 10 Run S ignal Metal Quartz

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Memory Effect

0,01 0,00 0,000 0,100 1 0,45 0,05 0,0011 0,100 1 1.106,01 110,60 0,1474 0,100 1 Result (µg/kg) Hg (ng) Height Weight (g) Sample ID

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Reproducibility at Low

Concentrations

AVG 8,55 SD 0,09 µg/kg RSD 1,01% Statistics 8,50 0,85 0,0217 0,100 8,49 0,85 0,0216 0,100 8,51 0,85 0,0217 0,100 8,53 0,85 0,0218 0,100 8,72 0,87 0,0222 0,100 Results (µg/kg) Hg (ng) Height Weight (g)

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Reproducibility at High

Concentrations

AVG 1.143,7 RSD 0,69% SD 7,88 µg/kg Statistics 1.143,4 114,34 0,1523 0,100 1.158,7 115,87 0,1543 0,100 1.141,3 114,13 0,1520 0,100 1.136,2 113,62 0,1514 0,100 1.138,8 113,88 0,1517 0,100 Results (µg/kg) Hg (ng) Height Weight (g)

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• US EPA method 7473

– Mercury in solids and solutions by thermal

decomposition amalgamation and atomic absorption spectrophotometry

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Comparison

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Comparison

DMA-80 vs. CV-AAS

Yes Minimal Waste generation Yes, to eliminate interferences Not required Wet chemistry Elevated Moderate Running cost

Limited to low range Up to 600 ng Working range 100 ml solution Up to 500 mg sample Sample size Aqueous Liquid and solids

Sample type Acid digestion Not required Sample preparation CV-AAS DMA-80 Technique

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Time Comparison

DMA-80 vs. CV-AAS

0 60 120 180 240 DMA-80 CV-AAS Ti m e ( m in ut es )

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DMA-80 Major Applications

• Biological

– Blood, urine, hair, tissue, plankton

• Liquids

– Waste water, crude oil, heavy oil, detergents, paints

• Solids

– Coal, fly ash, soil, sediment, sludge, minerals, food, feed, plastic, wood, vegetables, leaves, waxes

• Medicinal

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