1. No category

Basic and advanced technique of sample diges5on for metal analysis
GL SCIENCES INC. Sample Prepara5on Products Yoshiaki Furusho, PhD. http://www.gls.co.jp
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The Basic Diges5on Methods
Dry Digestion（Dry Ashing）　Direct heating, High Temp Oven
Microwave assist Dry Ashing System
Fusion
Fusion with graphite crucible, Pt crucible
High Temp Oven
Wet Digestion （Wet Ashing）　Open vessel Digestion
Hot Plate ＋Beaker ＋ Watch Glass、
Heat Block ＋Digestion Tube ＋Watch Glass
Kjeldahl Digestion
Closed Vessel Digestion
Stainless Steal Jacket and PTFE Vessel
Polypropylene Jacket and PFA Digestion Vessel
Microwave assist closed vessel digestion
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Dry Ashing
NO Reagent, just Heating
No reagent
Assist reagent
Regulation of
Calcium Oxide
Japanese Pharmacopia
To Take few hours
Electronic oven
To take few minites
High Temp
Low Temp
Target
Magnesium Oxide
Microwave
assist oven
Zn、Cd、Cr、Co、Cu、Pb etc.
Tips : semi volatile element is not accept over 500 deg.
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Microwave assist Dry Ashing system
• 
• 
• 
• 
Power : 1500 W
Reduce : Ashing time is shorter than oven
PC controlled instrument
1/10 time saving
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Microwave assisted dry ash applica5on
Quartz fiber crucible
Alumina crucible
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MW dry ashing 5me vs Old Techique
Comparison of Ashing Time
Sample
Type of sample
Current
MW Aching
Ashing time ( hour : minute )
Rate of time
%
Carbon Black
16:00
1:20
92%
Egg York
4:00
0:15
94%
Animal Feed
2:10
0:10
93%
Lactose
16:00
0:30
97%
Polyether
8:00
0:15
97%
Paper
3:00
0:10
94%
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What is Fusion?
Acid digestion is failure.
It makes salts, precipitations.
Oxides PbO, BaTiO3
Precipitations
Acid digestion is hard.
Fusion is good for these samples
Not successful with microwave vessel
400 ～ 1200 ℃
Rock, Ceramics
High melting point
materials
Flux
Pt
Graphite
Alkaline fusion tech is good for these samples
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Typical fusion technique
Glass bead
XRF
Remove matrix effect
Makes glass bead disk for easy XRF detection
Alkaline Fusion
At first, mekes glass bead. And then melt into
acid solution. Ex) 1M HCl, 1M HNO3
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ＩＣＰ
ＡＡＳ
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Fusion Technique < Basic procedure > 600-1100℃
５ ～ １０分
Glass Bead
XRF
・ Solid sample
① Flux
0.5g
ＩＣＰ
5g
② LiNO3、KNO3 1-20 µL
ＡＡＳ
③ LiBr 10-20µL
Sample : Flux = 1 : 10
Rotation and swinging
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1M Acid
Wet Diges5on Technique
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Common Diges5on Techniques and Associated Problems
•  Hot Plates •  Water/Oil/Sand Baths n 
Hot Plates Problems: n 
n 
Rus5ng, corrosion, short life span Poor temperature control n 
n 
Poor temperature uniformity n 
n 
Due to construc5on Contamina5on of samples n 
n 
n 
Use of thermometer From other samples From the Hot Plate Limited number of samples http://www.gls.co.jp
Water Baths n 
Low temperatures only n 
Need to replenish water Oil Baths n 
Higher temperatures n 
Dangerous 11
Review of General Diges5on Problems
• 
• 
• 
• 
Temperature Control Corrosion Cross contamina5on Glassware –  Cleaning a nuisance –  Calibra5on a nuisance •  Non-­‐reproducible results –  Loss of vola5le elements through boiling –  Loss of elements due to violent frothing http://www.gls.co.jp
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Solu5on of Diges5on problems
DigiPREP System Solution
For HNO3, HCL
digestion
DigiPREP Jr.
KeyPad
+
+
DigiTube
DigiPREP MS
Touch Screen
Controller
DigiPREP LS
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What is important for diges5on system?
2. 
Actual temperature control Acid resistance 3. 
Reduce cross contamina5on 4. 
Simultaneous diges5on 5. 
No “Hot Spots” 6. 
Good for semi-­‐vola5le element 7. 
Acid fume removal 8. 
Accuracy, reproducibility management 1. 
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Acid types and their boiling points
n 
HNO3 : Nitric acid (70%) 16N 120 deg n 
H2SO4 : Sulfuric acid (97%) 36N 320 deg n 
HClO4 : Perchloric acid (60%) 9N 200 deg n 
HF : Hydrofluoric acid (50%) 27N 70 deg n 
HCl : Hydrochloric acid (38%) 12N 110 deg n 
H2O2 : Hydrogen peroxide 30% 150 deg Acid Combina5on http://www.gls.co.jp
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Diges5on vessel type per. 1
•  Glass : –  Dry down by H2SO4 =OK, HF=NG, Price =OK –  Damage from strong alkaline solu5on –  Si, Na, K, Al, B, Blank level = High, –  Surface=OK, Easy wash, Trace level analysis=NG •  Quartz : –  Dry down by H2SO4 =OK, HF=NG, Price =Expensive –  Damage from strong alkaline solu5on –  Si, Blank level = High –  Surface=OK, Easy wash, Trace level analysis=Excellent http://www.gls.co.jp
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Diges5on vessel type per. 2
•  PP Polypropylene (Digi TUBE)：
•  Dry down by H2SO4=NG, Br=NG, Up to 130 deg. •  Price = Excellent •  Damage from conc. Sulfuric acid & Nitric acid. •  Surface = Good , Wash = not enough (good for disposable) •  Teflon PFA, PTFE, TFM : •  Up to 250 deg, Good for dry down method •  High temp H2SO4 dry down = NG •  Price is Expensive •  Chemical Resistance = Excellent •  Surface = Good, Wash method is not easy http://www.gls.co.jp
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DigiTUBEs : Polypropylene diges5on tube
Screw Cap
Rack Rock
Watch Glass
Class A　Refluxing
Graduate syringe
Level of conc
acid
Labeling
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Useful acid and best system
This is good technique for beginner technician
H2SO4　Plastic, Oil, Lipid
・Oxidize, hydrate or sulfonate
・Strong acid
・Good digestion by　over 230℃
・Glass, Quartz and Watch Glass
HNO3　Powder food, biological fluid
・Strong oxidizing
・Strong acid
・Good digestion temp by 80-120℃
・DigiTUBEs and Watch Glass
Ba、Pb issue
Ti, Cr issue
30% H2O2
Helpful for acid digestion
Using with HNO3, H2SO4
Cool down and add it.
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Typical Useful Sejng Point
•  Nitric acid diges5on –  40, 70, 95, ( for DigiPREP Jr. & MS) –  70, 120, ( for DigiPREP HT) DigiPREP MS
•  Sulfuric acid diges5on –  80, 170, (DigiPREP Jr. & MS) –  170, 240, 340, ( for DigiPREP HT) DigiPREP HT
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Smart Temp Program for Acid Diges5on
Temp
1 step Program
Temp
Multi Step Program
Step 3
Step 2
Drinking Water
Environmental Water
Organics level is low
Time
Step 1
Wasted Water
Food Sample
Organics level is High
Time
Why do you need a temp programming for digestion?
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Food Sample Diges5on
•  DigiPREP Jr. with HNO3 + H2O2
–  70 deg to 110 deg for 1-2 hours
–  0.5 g/10 mL HNO3
–  Final Step is done by 30% H2O2 drops
•  DigiPREP HT250 with H2SO4 + H2O2
– 
– 
– 
– 
170 deg – 240 deg – 380 deg Digestion 2-3 hours / 1st Step
1 g – 5 g / 10-15 mL H2SO4
Cool the tubes until 60 deg
2nd Step by 30% H2O2 at room temp to 240 deg / 15 min
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Sampling of Food Samples for DigiTUBEs
Putting acid int DigiTUBEs
Sampling of Food Sample
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DigiTUBEs Diges5on for Rice at 110 deg
Finish of milk, rice, and souse
digestion by DigiPREP Jr.
Acid digestion by DigiPREP Jr. and
Touc Screen Controller
Milk
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Rice
Milk Powder Souse
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Rice applica5on by DigiPREP HT
1. 240 deg Digestion by H2SO4
3. H2O2 digestion at 240 deg.
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2. Finish of H2SO4 Digestion Step
4. HNO3 digestion at 120 deg.
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Which type of diges5on method should you use?
Hard Digestion
Easy Digestion
1 step Program
Block type
Multi step Program
Opened
Benefit ：Scale Up Digestion, Simultaneous
Demerit ： Volatiles Lost
Hot Plate
Heat Block
Heat Block
Kjeldahl Style Unit
Type A
Type Ｂ
Microwave System
Entry Model
Low cost
Closed
Microwave
Microwave System
High End Model
Expensive
Benefit ：No loss, High Temp OK Demerit ： Small scale
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Microwave Sample Prepara5on Techniques
Acid digestion for Atomic
Absorption (AA) and Emission
(ICP) Spectroscopy
Solvent extraction
for gas and liquid
chromatography
Hydrolysis of proteins
and peptides for Amino
Acid Analysis
Sample drying and
moisture
determination
Polymer Dissolution for molecular
weight determination via Gel
Permeation Chromatography (GPC)
Organic
Synthesis
Reactions
Acid digestion of reinforced
composites for gravimetric
determination of fiber content
Dry Ashing
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Schema5c of Sample Hea5ng by Microwaves
Vessel Wall
Transparent to
Microwave Energy
localized
superheating
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Sample-acid mixture
(absorbs microwave
energy)
Microwave heating
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Conostan Oil Nitric Acid Diges5on
Sample Size Pressure-Temperature Comparison
Temperature (oC)
300
2
3
350
300
250
250
200
200
150
150
100
100
50
.25 gram
.36 gram
50
.46 gram
0
Pressure (psig)
1
350
0
0
10
20
30 0
10
20
Time (min.)
30 0
10
20
30
6 vessels 10 mL HNO3, 620 watts
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Schema5c of Home Microwave EM Field Palern
Low Em Field Intensity
Microwave
Cavity
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High Em Field
Intensity
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High Sample Throughput Microwave Diges5on
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What is needed amer diges5on?
1.  Concentra5ng diges5on solu5on 2.  Reducing salt level in diges5on solu5on • 
Use dilu5on step by H2O currently 3.  Removing the Na, K, Ca, and Mg elements 4.  Selec5ve collec5ng from high matrix solu5on The solution is SPE technique
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What is SPE?
•  Powerful Clean Up, and Powerful Concentration Tool
•  Using Separation Packing Gel in Cartridge
•  Switch from Liquid/Liquid Extraction to Solid Phase Extraction
Clean Up Method
Concentration
Target
Interfere
Retain the interfere
Through the Target
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Retain the Target
Collect the Target
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Typical SPE Applica5on : Metal in sea water
Chelating resin SPE cartridge, 250 mg/6mL (InertSep ME-1, etc.)
【Conditioning】
3M HNO3 5 mL
Demineralized Water 5 mL x 2 time
100 mM Ammonium Acetate pH5.5, 5mL
【Sample Loading】
10-20 mL/min
Sample 100 mL
Add pH5.5, 100 mM Ammonium Acetate,
the final concentration is 0.1 M
【Rinsing】
Rinse with 5 mL Demineralized Water
* For Sea Water which contains a lot of Ca and Mg,
use 0.5 M Ammonium Acetate.
【Elution】
3M HNO3, 3 mL – 6 mL
【Calibration】 Complete to 10 mL volume
ICP-AES, ICP-MS, and AAS
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How to use SPE cartridge
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Reagents for SPE http://www.gls.co.jp
2M Nitric Acid http://www.gls.co.jp
EnviroMAT ES-­‐H-­‐1 Ground Water http://www.gls.co.jp
STD of Cu 1000ppm http://www.gls.co.jp
SPE Manifold for Metal Analysis http://www.gls.co.jp
SPE Manifold with DigiTUBEs http://www.gls.co.jp
Modified Acid Resistance SPE Manifold http://www.gls.co.jp
Set the SPE Cartridge http://www.gls.co.jp
Add the Buffer Solu5on http://www.gls.co.jp
How to Load large volume sample 基本的に脱HFも可能
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Analysis results amer SPE treatment (Sea water)
valeur mesurée
valeur certifiée
20
valeur certifiée
U
2500
Cd
40
valeur mesurée
3000
U (ng/L)
Cd (ng/L)
60
2000
1500
1000
500
0
500
CASS-4
22
valeur mesurée
300
0
SLEW-3 2 4
CASS-4
11
3000
valeur certifiée
Zn
400
Zn (ng/L)
SLEW-331
200
0
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SLEW-342
valeur certifiée
1000
0
3 1
SLEW-3
4
1500
500
2 2
CASS-4
SLEW-3 13 SLEW-3 2
V
2000
100
1 1
CASS-4
CASS-422
valeur mesurée
2500
V (ng/L)
CASS-4
1 1
11
CASS-4
CASS-4 2
2
SLEW-3 13 SLEW-3 2 4
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Conclusion of acid diges5on
Decomposition of
Organic materials
Not interfere of
detection technique
Melting target elements
Volatile, Precipitation,
Hydration
High Method Blank
Quantity↓
Quantity↓
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