determination of anions in dried distillers grains with...
TRANSCRIPT
1 The world leader in serving science
Kassandra I. Oates, Lillian Chen, Brian De Borba, and Jeffrey S. Rohrer 245th ACS National Meeting & Exposition April 7, 2013
OT70620_E 04/13S
Determination of Anions in Dried Distillers Grains with Solubles
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Overview
• Introduction to Dried Distillers Grains with Solubles (DDGS) • Nutrient Composition, Dietary Formulation, Processing
• Background on Target Anions
• Method 1: A rapid (<10 min) method for the determination of chloride, sulfate, and phosphate in DDGS
• Method 1 Results
• Method 2: A reliable method for the determination of inositol phosphates in DDGS using IC and postcolumn derivatization
• Method 2 Results
• Conclusion
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Introduction
Distillers Grains • Are a coproduct of fuel ethanol
production. • Have been used as an alternative
feed in ruminant diets since the early 1900s.
• Are an excellent source of: • Energy • Fat • Protein • Essential Minerals
• Provide three times the amount of nutrients available from grain alone.
Dooley, F.J.; Cox, M.; Cox, L. Distillers Grain Handbook: A Guide for Indiana Producers to Using DDGS for Animal Feed [Online]; Dept. of Agric. Econ., Purdue Univ., West Lafayette, IN, 2008; http://incorn.org/index.php?option=com_content&task=view&id=43 (accessed Mar. 27, 2013).
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DDGS Analysis
• For Trade Purposes • Moisture • Crude Protein • Crude Fat • Crude Fiber
• Residual Components • Mycotoxins • Antibiotics
• Nutrient Composition • Moisture, Crude Protein, Crude Fat,
Crude Fiber • Detergent Fiber • Ash (inorganic/total mineral content) • Trace Elements
• Essential for optimum animal heath (Mineral Tolerances of Animals, 2005)
• Amino Acids • Starch
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Nutrient Composition of DDGS
• 30% Protein • 10% Oil • 5% Ash • 55% Fiber • Amino Acids • Vitamins • Nonfermented sugars
(e.g., xylose, arabinose) • Low molecular weight
organic acids (e.g., lactic acid, acetic acid)
• Minerals • Major (0.05–1.15%): Ca, P, K,
Mg, S, Na, Cl • Minor (6–150 ppm): Zn, Mn, Cu,
Fe, Al, Se
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Dietary Formulation
• On a dry matter (DM) ration basis: • Beef Cattle: 10–40% • Dairy Cattle: 20–25% • Sheep: 10% • Poultry: 10–20% • Swine: ≥ 20%
• To prevent underfeeding, producers formulate diets under the assumption that mineral concentrations are low. • Supplements such as dicalcium
phosphate and calcium sulfate are added to the feed.
• This leads to nutritional disorders and excess waste.
DDGS replace corn grain or soybean meal and result in equal or better performance.
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DDGS Process Schematic from Whole Corn Kernels
DDGS WDGS
CDS
WDG
Parkin, G.; Weyer P.; Just C.L. Riding the Bioeconomy Wave: Smooth Sailing or Rough Water for the Environment and Public Health? Proceedings of the 2007 lowa Water Conference—Water and Bioenergy, March 6, 2007, Iowa State Center, Ames, IA.
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Sulfate
• Naturally occurring sulfur is present at 0.1% in the corn kernel and 0.2% in DDGS. • Organic sulfur (cystine, methionine)
• Reported sulfur up to1.0% in DDGS • Inorganic sulfur up to 0.8%
• Sulfuric acid • Water
Why does sulfur need to be regulated in DDGS? • Total sulfur per requirements of the National Research Council
for beef and cattle is 0.4% of the dry matter in rations. • Excess sulfur can lead to Polioencephalomalacia (PEM) in
ruminants, reduces the availability and absorption of other minerals, and can cause blindness, seizures, comas, and death.
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Phosphate and Inositol Phosphates
• Total phosphorus concentrations range from 0.5–1.0%. • Inorganic (phosphate) • Organic
• Phytate • Other (DNA, RNA, proteins, lipids, starch)
• Not all forms are digestible • Only ruminants have the enzymes needed to digest phytate
• Digestible phosphorus • Corn: ~21% • DDGS: ~59%
• Phosphate level is indicative of the extent of the hydrolysis of phytates and can be used to determine phosphorus bioavailability to nonruminants.
InsP0-5 + PO4
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Method 1
Equipment • Thermo Scientific™ Dionex™ ICS-2100 Integrated Reagent-Free™
IC (RFIC™) system including: • Pump • Degasser • Eluent Generator • Column Heater • Autosampler
Data Analysis • Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data
System software 7.1
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Method 1 Conditions
Column: Thermo Scientific™ Dionex™ IonPac™ AG11/AS11, 2 mm Eluent: 3–15 mM KOH 0–5 min, step at 5 min to 25 mM Eluent Source: Dionex ICS-2100, Thermo Scientific™ Dionex™ EGC III KOH with Thermo Scientific™ Dionex™ CR-ATC II Flow Rate: 0.5 mL/min Inj. Volume: 5 µL Temp: 30° C Detection: Thermo Scientific™ Dionex™ ASRS™ 300 Anion
Self-Regenerating Suppressor (2 mm), recycle mode
Sample Preparation Anions were extracted from a 1 g sample of DDGS by ultrasonic-assisted extraction in 100 mL of DI water, followed by centrifugation and dilution.
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Column
• The Dionex IonPac AS11 column is designed to separate a wide range of small organic acids from common anions which are often present in these types of samples.
• It has the ability to separate strongly retained polyvalent anions, such as phosphate.
• It is stable between pH 0–14.
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Anions in DDGS
1
2
3
0 1.5 3.0 4.5 6.0 7.5 -5
24.2
min
µS µS
-5.1
21.4
A
B
Column: Dionex IonPac AG11, AS11, 2 mm Eluent: 3–15 mM KOH 0–5 min, step at 5 min to 25 mM Eluent Source: Dionex EGC III KOH with Dionex CR-ATC Flow Rate: 0.5 mL/min Inj. Volume: 5 µL Temp: 30 ºC Detection: Dionex ASRS 300 (2 mm), recycle mode
Samples: A. Prepared DDGS sample B. Calibration standard Peaks: A B c 1. Chloride 1.3 mg/L 0.13 %* 5 mg/L 2. Sulfate 15.4 1.54 40 3. Phosphate 11.2 1.12 40 * calculated amount
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Linearity, Limits of Detection (LODs) and Limits of Quantification (LOQs)
1 Seven calibration levels, each injected in triplicate 2 LOD calculated as 3 × S/N 3 LOQ calculated as 10 × S/N
Analyte Calibration
Range (mg/L)
Linearity1 (r2)
LOD2 (µg/L)
LOQ3 (µg/L)
Chloride 0.15–5 0.9999 1.7 5.7 Sulfate 1.25–40 0.9999 3.3 10.9 Phosphate 1.25–40 0.9999 5.7 18.8
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Precision
Analytes Measured in Different Starting Grain Weights
(n = 7) Chloride Sulfate Phosphate
Amount Sampled
(g)
Average Amount Found
(%)
Peak Area RSD
Average Amount Found
(%)
Peak Area RSD
Average Amount Found
(%)
Peak Area RSD
0.75 0.13 0.41 1.52 0.44 1.11 0.43
1.00 0.13 0.40 1.49 0.50 1.08 0.48
1.25 0.13 0.59 1.49 0.63 1.09 0.69
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Accuracy
Chloride, Sulfate, and Phosphate Recovery in Spiked DDGS Samples
Chloride Sulfate Phosphate
Final Spiked Concn (mg/L)
Amount Recovered
(%)
Final Spiked Concn (mg/L)
Amount Recovered
(%)
Final Spiked Concn (mg/L)
Amount Recovered
(%)
0.27 107 3.13 102 2.30 104
0.55 100 5.87 99.2 4.59 97.5
1.16 100 12.4 101 9.15 99.0
1.49 97.5 15.5 98.4 11.5 96.2
1.71 97.9 18.5 98.8 13.7 96.5
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Method 2
Equipment • Dionex ICS-5000 RFIC system including:
• SP Single Pump or DP Dual Pump • DC Detector/Chromatography Compartment • AS-AP Autosampler
• Thermo Scientific Dionex ICS-5000+ Series VWD Variable Wavelength Detector with Analytical Flow Cell
• Thermo Scientific Dionex AXP Auxiliary Pump • Thermo Scientific Dionex EGC Carbonate Mixer Kit • Knitted Reaction Coil, 750 µL • Manifold, 3-way mixing tee
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Method 2: Conditions
Columns: Dionex CarboPac PA100 Analytical and Guard, 4 mm Eluent: A. DI water B. 0.5 M HCl Program: -15–0 min 5% B, 0–8 min 5–10% B, 8–25 min 10–35% B, 25–35 min 35–100% B, 35–42 min 100% B, 42–42.1 min 100–5% B Eluent Flow Rate: 1.0 mL/min Inj. Volume: 100 µL (full) Temperature: 30 ˚C Postcolumn Conditions PCR: 1% Fe(NO3)3 ∙ 9 H2O in 0.33 M HClO4 PCR Flow Rate: 0.4 mL/min Detection: UV absorbance, 290 nm Noise: 0.9 mAU
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The Dionex CarboPac PA100 Column
• Specifications • 8.5 µm EVB/DVB substrate agglomerated with 275 nm MicroBead
quaternary ammonium functionalized latex
• Able to separate InsP2-6 isomers because of its high ion-exchange capacity
• Isomers elute in order of increasing number of phosphate groups.
• Stable between pH 0–14
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Sample Preparation
• Inositol phosphates were extracted from DDGS by ultrasonic-assisted extraction in 0.5 M HCl, followed by centrifugation, and filtration.
• The sample was then treated with a Thermo Scientific™ Dionex™ OnGuard™ II RP and AG/H cartridges in series. • OnGuard treatment of the sample removes hydrophobic compounds and
chloride, which is necessary to reduce column overloading from the chloride in the sample.
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DDGS Sample vs In-House Reference Standard
Samples: a) DDGS sample b) In-house reference standard Peaks: 1–4: InsP2 5–13: InsP3 14–20: InsP4 21–24: InsP5 25: InsP6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 -65
0
600
min
mAU
12 13
14
15
16 17
18
19 20
21
22 23
24
25
1
2
3
4 6 8
9
11
PO4 Ox
SO4
a
b
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Linearity, LODs and LOQs
Analyte Calibration
Range (mg/L)
Linearity1
(r2) LOD2
(mg/L) LOQ3
(mg/L)
DL-Ins(1,2,5,6)-P4 3.1-100 >0.999 1.0 3.2
DL-Ins(1,2,4,5,6)-P5 3.1-100 >0.999 1.0 3.2
Ins(1,2,3,4,5,6)-P6 10-300 >0.999 1.0 3.2 1 Six calibration levels, each level injected in duplicate 2 LOD calculated as 3 × S/N 3 LOQ calculated as 10 × S/N
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To compare the amounts to the literature values, InsP amounts were determined on a dry matter (DM) basis.
Quantitation of Inositol Phosphate Isomers
InsP Analogue Prep # Peak Area
(mAU*min)
Peak Area RSD
Amount Found (mg/L)
Calculated Amount
(mg/g, DM)1
DM1 %
Average DM1 %
Ins(1,2,3,4,5,6)-P6 1 62.2 0.1 97.6 2.1 0.21
0.205 2 59.5 4.1 93.7 2.0 0.20
Ins(1,2,4,5,6)-P5 1 28.9 0.1 67.7 1.5 0.15
0.14 2 25.9 0.4 60.7 1.3 0.13
(1,2,5,6)-P4 1 18.9 1.3 33.0 0.68 0.07
0.07 2 17.4 0.3 30.4 0.66 0.07
1 Dry matter content was determined by drying 2 g of DDGS in an oven at 135 ˚C for 2 h. The sample contained 10.5% moisture (a dry matter value of 89.5%).
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Estimation of Total InsP2-6
Total InsP2-6 amounts were estimated using relative response factors.
Analogue Calculated
Amount (mg/g, DM)
% DM
InsP6 2.0 0.20
InsP5 2.3 0.23
InsP4 1.3 0.13
InsP3 1.3 0.13
InsP2 0.4 0.04
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Conclusion
• Method 1 provides a simple and accurate approach for determining water-soluble anions present in DDGS in less than 10 min on a Dionex IonPac AS11 column.
• Method 2 provides a rapid and reliable sample preparation procedure and chromatographic method to determine the phytate hydrolysis products in DDGS.
• For the determination of inositol phosphates, the Dionex OnGuard II RP and Ag/H cartridges simplified the sample preparation procedure when compared to the most commonly used capture and release methods.
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Thank you for your attention!