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Liquid Sample Introduction Techniques
Using Ultrasonic Nebulization with ICP-OES Detection for USEPA Method 200.7
IntroductionMeasurement of Trace Elements in Water
To safeguard human health and the environment, the USEPA adjusts regulations for maximum contaminant levels (MCLs) in water based on accepted scientific findings and guidelines.
The current USEPA Method 200.7 revision 4.4 describes criteria for the measurement of metals and trace elements in drinking water and wastewater using inductively coupled plasma optical emission spectrometry (ICP-OES).
Liquid Sample IntroductionUltrasonic Nebulization
An ultrasonic nebulizer is an accessory for ICP-OES that enables higher sample transport efficiency (versus a standard pneumatic nebulizer) to the plasma. This benefit can be helpful for detection of more difficult elements such as As, Pb, Sb, Se, and Tl using ICP-OES.
This webinar describes the use of ultrasonic nebulization for improved ICP-OES detection of trace elements in waters per USEPA Method 200.7.
Ultrasonic Nebulization Principle of Operation
In place of a regulated gas flow for generation of a liquid sample aerosol (pneumatic nebulization), liquid sample is pumped across a quartz plate with an underlying oscillating (piezoelectric) crystal.
The oscillations of the crystal will break up the liquid flow and cause formation of a sample aerosol. Ultrasonic nebulization is typically up to 10x more efficient (versus a conventional pneumatic nebulizer) for conversion of liquid sample into a useable aerosol.
Teledyne CETAC U5000AT+ Ultrasonic NebulizerDimensions and Weight
Width: 35.6 cm (14.0 in)Depth: 34.9 cm (13.7 in)Height: 25.4 cm (10.0 in)
Weight: 12.3 kg (27 lbs)
TemperatureControllers (2)
U5000AT+ Important Features
• Integrated desolvation system (electrothermal)– Removes excess sample aerosol solvent
to ensure plasma stability• Built-in drain peristaltic pump
– Removes condensed sample solvent to waste
Teledyne CETAC U5000AT+ Schematic
Piezoelectric Crystal(Transducer)
U5000AT+ Transducer Assembly
Piezoelectric Crystal(disk shape) Quartz Plate
Instrumentation
ICP-OES: PerkinElmer Avio 500
Ultrasonic Nebulizer: Teledyne CETAC U5000AT+
Autosampler: PerkinElmer S23
U5000AT+ Ultrasonic Nebulizer Easy and Fast (10 min) Installation
Installation Steps for Ultrasonic Nebulizer (USN) using theTeledyne CETAC supplied interface kit:
1. Remove standard nebulizer and spray chamber from the ICP-OES.
2. Connect nebulizer gas inlet line from ICP-OES to the USN.
3. Connect sample out line from USN to ICP torch.
4. Connect sample line from autosampler to USN inlet line.
5. Connect power to USN and turn on unit. Wait 10 minutes for heater and cooler to stabilize. Start ICP.
No computer control or software needed
ICP-OES with Ultrasonic Nebulization
PerkinElmer Avio 500 ICP-OES, U5000AT+, ASX-280 Autosampler
Connections Between Host ICP-OES & U5000AT+ Ultrasonic Nebulizer
Argon In Line
Power Cable
Sample Out Line
Nebulizer Gas Line
Host ICP-AESPeri Pump
Autosampler
DrainPeri Pump
Ultrasonic NebulizerAerosol Generation: One Button Operation
Ultrasonic Nebulizer AerosolClose-Up View
Transducer
Sample Inlet Line
Aerosol
Operating Conditions ICP-OES with Standard Nebulizer and U5000AT+ USN
Parameter Std Nebulizer U5000AT+ USN
ICP Power 1500 W 1500 WPlasma Gas 8.0 L/min 10.0 L/minAuxiliary Gas 0.2 L/min 0.2 L/minNebulizer Gas 0.65 L/min 0.50 L/minTorch Injector 2 mm 2 mmUptake Rate 1.0 mL/min 1.25 mL/minCassette Position -3.0 -5.0Resolution Normal NormalNebulizer Type Meinhard K PiezoelectricSpray Chamber Baffled cyclonic ConicalHeater Temp N/A 140°CCooler Temp N/A 3°C
Integration Time 0.01 s min, 0.2 s max 0.01 s min, 3 s max
Peak Area 3 pts/peak 3 pts/peakReplicates 4 4
2% HNO3 matrix
Operating ConditionsTorch Cassette Position – (I)
Operating ConditionsTorch Cassette Position – (II)
Calibration
Reagent Blank and StandardsMultielement (29) standards prepared in 2% double-distilled HNO3 at 10, 20, 50, and 100 µg/L.Reagent blank of 2% double-distilled HNO3
No internal standard used.
Calibration
Correlation Coefficients:Standard Nebulizer: 0.9950 to 0.9999U5000AT+ Ultrasonic Nebulizer: 0.9991 to 0.9999
Element Signal EnhancementAs 188.979nm 100µg/L
Dashed Line: Std Neb.Solid Line: U5000AT+
Element Signal EnhancementSe 196.026nm 100µg/L
Dashed Line: Std Neb.Solid Line: U5000AT+
Element ICP-OES Intensity Comparison100 µg/L As, Pb, Sb, Se
Element Wavelength (nm)
Intensity Std Neb
Intensity U5000AT+
Factor
As 188.979 254 1838 7.2xPb 220.353 1499 9025 6.0xSb 206.836 284 2395 8.4xSe 196.026 289 2272 7.8x
Detection Limits
Instrument Detection Limits (IDLs)After calibration, the reagent blank was measured 10 times as a sample, the individual IDLs defined as 3x the standard deviation of the reagent blank concentration.The mean of the 10 individual blank runs for each element was calculated as the final IDL per Method 200.7 criteria.
Detection Limits in µg/L w. ICP-OES - IElement λ (nm) Std Neb U5000AT+ Factor
Ag 328.068 0.09 0.008 11.2
Al 394.401 0.17 0.018 9.4
As 188.979 1.1 0.15 7.3
Ba 493.408 0.03 0.02 1.5
Be 313.107 0.02 0.01 2.0
Ca 315.887 0.09 0.04 2.3
Cd 214.440 0.57 0.009 63.3
Co 228.616 0.46 0.02 23.0
Cr 267.716 0.15 0.01 15.0
Cu 324.752 0.28 0.012 23.3
Fe 238.204 0.24 0.02 12.0
K 766.490 0.33 0.014 23.5
Li 670.784 0.08 0.03 2.7
Mg 285.213 0.03 0.004 7.5
Mn 257.610 0.01 0.002 5.0
Detection Limits in µg/L w. ICP-OES - IIElement λ (nm) Std Neb U5000AT+ Factor
Mo 203.845 1.3 0.04 32.5
Na 589.592 0.37 0.04 9.3
Ni 231.604 0.43 0.02 21.5
P 178.221 5.4 0.28 19.2
Pb 220.353 1.4 0.06 23.3
Sb 206.836 2.2 0.12 18.3
Se 196.026 2.0 0.15 13.3
Si 251.611 1.1 0.51 2.1
Sn 189.927 0.98 0.07 14.0
Sr 421.552 0.08 0.01 8.0
Ti 334.940 0.05 0.004 12.5
Tl 190.801 1.4 0.19 7.3
V 292.402 0.07 0.004 17.5
Zn 206.200 0.19 0.02 9.5
Detection Limits
Instrument Detection Limits (IDLs)The average reduction in IDLs across the 29 measured elements is 14.3x, with a range of 1.5x to 63.3x.
The lower 1.5x to 2.7x factors may be due to reagent blank contamination.
Water Sample Description
Municipal Water MatrixThe municipal water sample was from the Platte West Water Treatment Plant (Elkhorn, NE) which serves the Omaha, Nebraska metropolitan area. This water sample is a treated type, meaning it is softened, clarified, filtered, and disinfected.
Platte River
By Shannon1 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=79267174
Municipal Water SampleResidue from evaporated 400mL aliquot
Operating Conditions ICP-OES with Standard Nebulizer and U5000AT+ USN
Parameter Std Nebulizer U5000AT+ USN
ICP Power 1500 W 1500 WPlasma Gas 8.0 L/min 10.0 L/minAuxiliary Gas 0.2 L/min 0.2 L/minNebulizer Gas 0.65 L/min 0.50 L/minTorch Injector 2 mm 2 mmUptake Rate 1.0 mL/min 1.25 mL/minCassette Position -3.0 -5.0Resolution Normal NormalNebulizer Type Meinhard K PiezoelectricSpray Chamber Baffled cyclonic ConicalHeater Temp N/A 140°CCooler Temp N/A 3°C
Integration Time 0.01 s min, 0.2 s max 0.01 s min, 3 s max
Peak Area 3 pts/peak 3 pts/peakReplicates 3 3
Municipal water matrix
Municipal Water SampleMeasured Major Elements
Element Wavelength (nm) Measured Conc.
Ca 317.933 45.9 mg/L + 0.9 mg/LNa 330.237 34.4 mg/L + 0.1 mg/LMg 285.213 98.3 mg/L + 1.9 mg/LK 766.490 8.6 mg/L + 0.1 mg/L
Ba 493.408 85.6 µg/L + 1.5 µg/LSr 421.552 45.9 µg/L + 5.4 µg/L
Calibration
Municipal Water Spikes and BlankSpikes prepared in water sample acidified to 2% (v/v) using double-distilled HNO3 at 5, 10, 20, 50, and 100 µg/L As, Cd, Pb, Sb, Se, and TlWater matrix blank acidified to 2% (v/v) using double-distilled HNO3
No internal standard used.
Correlation Coefficients in Municipal Water Matrix
Element Wavelength (nm) Corr. CoefficientAs 188.797 0.9999Cd 214.440 0.9999Pb 220.353 0.9999Sb 206.836 0.9999Se 196.026 0.9995Tl 190.801 0.9999
Spectral Overlay of As Spikes into Municipal Water Matrix using U5000AT+
Spectral Overlay of Pb Spikes into Municipal Water Matrix using U5000AT+
Detection Limits
Detection LimitsAfter calibration, the water blank was measured 10 times as a sample, the individual IDLs defined as 3x the standard deviation of the water blank concentration.The mean of the 10 individual blank runs for each element was calculated as the final IDL per Method 200.7 criteria.The limit of quantitation (LOQ) is defined as 3.3x the IDL.
Measured Detection Limits in Municipal Water Matrix
Element λ (nm) U5000AT+
IDL (µg/L)U5000AT+
LOQ (µg/L)USEPA
MCL (µg/L)As 188.797 0.44 1.45 10
Cd 214.440 0.07 2.31 8
Pb 220.353 0.28 0.92 15
Sb 206.836 0.26 0.86 6
Se 196.026 1.4 4.6 50
Tl 190.801 0.34 1.12 2
% Recovery Tests
Three separate sample matrices:1. Laboratory control sample (reagent blank)
a. 5 µg/L multielement (19) spike2. Untreated well water sample
a. 5 µg/L multielement (19) spike3. Standard reference material
a. NIST 1643f Trace Elements in Water
% Recovery Criteria per Method 200.7
1. Laboratory control sample (reagent blank)85% to 115%
2. Untreated well water sample70% to 130%
3. Standard reference material85% to 115%
Well Water Sample: Near Saint Croix River
Kmusser, CC BY-SA 2.5 <https://creativecommons.org/licenses/by-sa/2.5>, via Wikimedia Commons
Well Water SampleMeasured Major Elements
Element Wavelength (nm) Measured Conc.Ca 317.933 52.0 mg/L + 0.6 mg/LNa 330.237 24.4 mg/L + 0.5 mg/LMg 285.213 16.4 mg/L + 0.1 mg/LK 766.490 1.45 mg/L + 0.03 mg/LBa 493.408 90.2 µg/L + 2.5 µg/LSr 421.552 73.3 µg/L + 1.8 µg/LZn 206.200 9.56 µg/L + 0.45 µg/L
Well Water ICP-OES Spectra with 5µg/L As Spike
Std Neb
U5000AT+
Laboratory Control Sample and Well Water Matrix Spike Recoveries – (I)
Element LCS (µg/L)
% Recovery
W. Water Spike (µg/L)
% Recovery
Ag 4.85 97 4.25 85Al 5.12 102 5.60 112As 5.03 101 5.62 113Be 4.66 93 4.59 92Cd 5.07 101 4.77 95Co 5.08 102 3.79 76Cr 4.97 99 4.49 90Cu 5.19 104 5.11 102Fe 5.58 112 4.46 89Mn 4.98 100 5.00 100
5 µg/L spike
Laboratory Control Sample and Well Water Matrix Spike Recoveries – (II)
Element LCS (µg/L) % Recovery
W. Water Spike (µg/L)
% Recovery
Mo 5.06 101 4.73 97Ni 5.14 103 3.87 77Pb 5.23 105 4.31 86Sb 4.88 98 5.04 101Se 4.56 94 5.35 107Sn 4.84 97 4.88 98Ti 4.93 99 5.19 104Tl 5.16 103 5.33 107Zn 4.94 99 4.45 89
5 µg/L spike
% Recovery NIST 1643f Trace Elements in Water Using U5000AT+ w. ICP-OES (I)Element Measured (µg/L) Certified (µg/L) % Recovery
Ag 0.793 + 0.110 0.9703 + 0.0055 82
Al 148.9 + 1.1 133.8 + 1.2 111
As 63.00 + 1.92 57.42 + 0.38 110
Ba 451.4 + 16.6 518.2 + 7.3 87
Be 13.91 + 0.02 13.67 + 0.12 102
Cd 6.63 + 0.22 5.89 + 0.13 113
Co 22.15 + 0.31 25.30 + 0.17 87Cr 17.55 + 0.26 18.50 + 0.10 95
Fe 91.04 + 0.55 93.44 + 0.78 97
Mn 35.46 + 0.17 37.14 + 0.60 95
% Recovery NIST 1643f Trace Elements in Water Using U5000AT+ w. ICP-OES (II)
Element Measured (µg/L) Certified (µg/L) % Recovery
Mo 120.6 + 0.6 115.3 + 1.7 105Ni 52.7 + 0.5 59.8 + 1.4 88Pb 17.483 + 1.721 18.488 + 0.084 95Sb 57.88 + 1.65 55.45 + 0.40 104Se 11.218 + 1.997 11.700 + 0.081 96Sr 289 + 6 314 + 19 92Tl 7.252 + 1.026 6.892 + 0.035 105V 35.78 + 0.11 36.07 + 0.28 99
Zn 82.4 + 1.0 74.4 + 1.7 111
Analysis of Water Samples Using U5000AT+
USN with ICP-OES Detection per USEPA 200.7
• Enhanced signal and lower detection limits for important elements such as As, Cd, Pb, and Se
• Excellent agreement with NIST 1643f certified values
• Spike recoveries in acceptable ranges• Fast and easy setup with host ICP-OES• No computer control required
Ultrasonic Nebulizer for ICP-OESPart Numbers for Ordering
• U5000AT+ Ultrasonic Nebulizer
– U51-99-0001A+ (115 V)
– U51-99-0001B+ (220 V)
U5000AT+ Interface Kits for ICP-OESU5000AT+ Compatibility
• All ICP-OES Models– Examples with Interface Kit SP Numbers ( )
• Agilent (SP5155Y)• Analytik Jena (SP5155Y)• PerkinElmer (SP5155L)• Shimadzu (SP5155Z)• Spectro (SP5155P)• Teledyne Leeman (SP5155I)• Thermo Fisher (SP5155CC)
One interface kit provided at no charge with each U5000AT+
Ultrasonic NebulizationTeledyne CETAC Application Notes
• Municipal water• Well water• Pharmaceuticals (ex. aspirin)• Food matrices and juices• Toy product safety (per EN-71)• Fine chemicals (sulfuric acid)
Acknowledgement
• Special thanks to Santiago Villegas for his work in sample preparation, method development, data collection, and outline text for this important application.
Where to go for more information
• Service support– [email protected]
• Sales support– [email protected]
• Technical support– [email protected]– [email protected]
• Web information– https://www.teledynecetac.com/products/nebulizers/u50
00at+– https://www.teledynecetac.com/site-
products/Brochures/Flyer_U5000AT.pdf
