Nitrogen/Protein Determination in Starch by Flash Combustion using Large Sample Weight
Transcription
Nitrogen/Protein Determination in Starch by Flash Combustion using Large Sample Weight
Nitrogen/Protein Determination in Starch by Flash Combustion using Large Sample Weight as an Alternative to the Kjeldahl Method Liliana Krotz and Guido Giazzi Thermo Fisher Scientific, Milan, Italy Overview Purpose: To show the determination of Nitrogen / Protein in starch samples by flash combustion at high sample weight. Methods: Starch samples were analyzed using an elemental analyzer with an automatic autosampler. Results: Data collected of Nitrogen / Protein from different starch samples are discussed to assess the performance of the analyzer. Method The sample is weighed in via the Thermo ScientificTM amount of oxygen using th complete combustion of th capsule in the range of 100 Introduction After combustion, the prod reactor filled with copper. W adsorbed by the No-Stop T column and finally is detec The production process in the starch industry, the protein content, calculated by the determination of nitrogen, is periodically monitored and tested for quality control. Because starch is used in the preparation of animal feeds, bakery products, puddings, instant meals, syrups and desserts, the determination of N/Protein is critical. A complete report is autom Xperience dedicated data analysis. Eager Xperience balance to the sample tabl the instrument. It is therefore very important to have a method which allows the fast analysis of N/Protein with an excellent reproducibility. FIGURE 2. Nitrogen / Pro The Thermo ScientificTM FLASH 4000 Nitrogen/Protein Analyzer (Figure 1), based on the dynamic flash combustion of the sample, satisfies all the requirements of modern laboratories such as stability, accuracy, day-by-day reproducibility and high sample throughput , and does not require sample digestion or toxic materials. This alternative to the classical Kjeldahl method, based on Dumas (combustion) method, has been developed and approved by different associations such as ASBC, AOAC, AACC, AOCS, IFFO and ISO. This paper presents data on Nitrogen/Protein determination of different starch samples in a large range of concentrations (150 – 2500 ppm nitrogen), obtained with the analyzer using large sample weight to demonstrate the validity of the method without matrix effect. Data compared to the results obtained by the Kjeldahl method demonstrates the validity of the system. FIGURE 1. FLASH 4000 Nitrogen / Protein Analyzer. Analytical conditions: Left Furnace Temperature Right Furnace Temperature Oven Temperature: Carrier Flow: Reference Flow: Standard: Sample Weight: Note: The oxygen amount calculated automatically by software. *EDTA: EthyleneDiamineTe Results The starch samples analyz The data obtained demons indicating complete combu The calibration of the FLAS as calibration method. Table 1 shows the nitrogen 0.25 % N, analyzed ten tim obtained analyzing the sam the data are comparable a sample weight. 2 Nitrogen/Protein Determination in Starch by Flash Combustion using Large Sample Weight as an Alternative to the Kjeldahl Method n in starch samples by flash ental analyzer with an nt starch samples are TABLE 1. Nitrogen data of sta Method Sample weight (mg) The sample is weighed in a tin capsule and introduced into the combustion reactor via the Thermo ScientificTM MASTM 4000 autosampler together with the correct amount of oxygen using the Thermo ScientificTM OxyTuneTM function, insuring a complete combustion of the sample. The samples are weighed directly in the tin capsule in the range of 1000 - 2000 mg. After combustion, the produced gases are carried by a helium flow to a second reactor filled with copper. Water is trapped through a Peltier system while the CO2 is adsorbed by the No-Stop Twin traps. Then the nitrogen is swept through a GC column and finally is detected by a thermal conductivity detector (TCD) (Figure 2). n content, calculated by the tested for quality control. s, bakery products, puddings, N/Protein is critical. A complete report is automatically generated by the Thermo ScientificTM Eager Xperience dedicated data handling software, and is displayed at the end of the analysis. Eager Xperience also allows the direct sample weight transfer from the balance to the sample table, and the complete control of the analytical parameters of the instrument. ows the fast analysis of FIGURE 2. Nitrogen / Protein configuration 981.0 997.4 984.8 998.3 1032.2 1013.4 998.0 1017.3 964.3 987.6 TABLE 2. Nitrogen data of sta nalyzer (Figure 1), based on the requirements of modern ducibility and high sample xic materials. This alternative bustion) method, has been as ASBC, AOAC, AACC, Sample weight (mg) 797.7 946.2 1101.6 1255.0 ion of different starch samples gen), obtained with the alidity of the method without he Kjeldahl method 1401.4 1611.1 2001.5 987.7 802.7 Analytical conditions: Left Furnace Temperature : Right Furnace Temperature : Oven Temperature: Carrier Flow: Reference Flow: Standard: Sample Weight: 1025.0 950°C 840°C 50°C 300 ml/min 300 ml/min 500 mg EDTA* (9.59 %N) 1000 - 2000 mg Note: The oxygen amount necessary for complete combustion of samples is calculated automatically by the OxyTune function present in the Eager Xperience software. *EDTA: EthyleneDiamineTetraAcetic acid Table 3 shows the Nitrogen / Pr 400 ppm N weighed in a range The protein content was calcula software using 6.25 as protein f TABLE 3. Nitrogen / Protein da 1.0 – 1.1 grams. N% Results 0.0472 The starch samples analyzed were chosen on basis of their differing nitrogen content. The data obtained demonstrates the no-matrix effect in the determination of nitrogen, indicating complete combustion for all type of samples. 0.0430 The calibration of the FLASH 4000 was performed with EDTA (9.59 %N) using K factor as calibration method. 0.0419 0.0484 Table 1 shows the nitrogen results obtained of a starch sample of approximately 0.25 % N, analyzed ten times at about 1 gram. Table 2 shows the nitrogen data obtained analyzing the same starch in a range from 700 mg to 2 grams. In both cases the data are comparable and no significant difference was observed changing the sample weight. 0.0454 0.0427 0.0441 0.0438 0.0422 0.0422 Thermo Scientific Poster Note • PN42212_PITTCON 2014_E_02/14S 3 TABLE 1. Nitrogen data of starch (0.25 %N) at 1 gram. Sample weight (mg) uced into the combustion reactor pler together with the correct OxyTuneTM function, insuring a are weighed directly in the tin by a helium flow to a second h a Peltier system while the CO2 is ogen is swept through a GC ctivity detector (TCD) (Figure 2). e Thermo ScientificTM Eager s displayed at the end of the ample weight transfer from the ntrol of the analytical parameters of N% 981.0 0.2547 997.4 0.2500 984.8 0.2518 998.3 0.2550 1032.2 0.2529 1013.4 0.2514 998.0 0.2579 1017.3 0.2502 964.3 0.2496 987.6 0.2538 Average N % RSD % °C °C C ml/min ml/min mg EDTA* (9.59 %N) 0 - 2000 mg combustion of samples is present in the Eager Xperience 797.7 0.2536 946.2 0.2530 1101.6 0.2528 1255.0 0.2600 1401.4 0.2556 1611.1 0.2571 2001.5 0.2637 987.7 0.2522 802.7 0.2536 1025.0 0.2541 0.2527 1.0520 with EDTA (9.59 %N) using K factor arch sample of approximately ble 2 shows the nitrogen data m 700 mg to 2 grams. In both cases nce was observed changing the Average N % RSD % 0.2556 C 4 D 5 6 7 8 9 D 10 G 11 G 1.4550 13 14 15 C 16 C 17 18 D 19 Protein % 0.2947 0.0484 0.2756 0.0430 0.2736 0.0454 0.2640 5.0777 3 12 0.0472 0.0427 Star 2 0.2636 0.0419 0.3022 0.0441 0.2685 0.0438 0.2841 0.0422 0.2667 0.0422 0.2619 TABLE 5. Statistical dat Starch ID A TABLE 3. Nitrogen / Protein data of starch (0.04 %N) in the range of 1.0 – 1.1 grams. RSD % Run 1 Table 3 shows the Nitrogen / Protein data of a starch sample of approximately 400 ppm N weighed in a range of 1000 – 1100 mg. The protein content was calculated automatically by the Eager Xperience dedicated software using 6.25 as protein factor. N% is of their differing nitrogen content. ect in the determination of nitrogen, ples. N% Table 5 shows the statistic calculated automatically b protein factor. No memory effect was ob the nitrogen. TABLE 4. Random sequ TABLE 2. Nitrogen data of starch (0.25 %N) in the range of 700 mg to 2 grams. Sample weight (mg) Table 4 shows the sequen randomly to evaluate mem content. RSD % 2 B C 5.0535 4 Nitrogen/Protein Determination in Starch by Flash Combustion using Large Sample Weight as an Alternative to the Kjeldahl Method D E F G N 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1 gram. Average N % RSD % Table 4 shows the sequence of analysis of starch samples in trace level analyzed randomly to evaluate memory effect when changing the sample type and nitrogen content. Table 6 shows the N/Prot liquid sample was adsorb the tin capsule and the sa Table 5 shows the statistical data of the relative samples. The protein content was calculated automatically by the Eager Xperience dedicated software using 6.25 as protein factor. No memory effect was observed indicating complete combustion and conversion of the nitrogen. TABLE 6. Nitrogen / Pro N% 0.0355 TABLE 4. Random sequence of starch samples at trace level. 0.2527 1.0520 he range of 700 mg to 2 grams. Average N % 0.2556 RSD % 1.4550 ch sample of approximately . by the Eager Xperience dedicated Protein % 0.0366 Run Starch ID Weight (mg) N% Protein % 1 A 1000.4 0.0177 0.1107 2 B 1002.5 0.0404 0.2528 3 C 1051.5 0.0162 0.1015 4 D 1050.4 0.0380 0.2378 5 B 1099.6 0.0404 0.2525 6 A 1100.9 0.0179 0.1120 7 E 1000.9 0.0356 0.2228 8 E 1003.9 0.0354 0.2212 9 D 1050.7 0.0382 0.2387 10 G 1050.8 0.0191 0.1196 11 G 1100.9 0.0188 0.1174 12 E 1100.3 0.0365 0.2280 13 F 1101.2 0.0143 0.0914 14 F 999.9 0.0150 0.0935 15 C 1050.9 0.0167 0.1046 16 C 1100.1 0.0162 0.1014 17 B 1102.1 0.0403 0.2519 18 D 1051.8 0.0387 0.2419 19 A 1051.0 0.0178 0.1115 RSD % 2 Starch ID B 0.2947 C 0.2756 0.2736 0.2640 0.2636 5.0535 D 0.3022 0.2685 E 0.2841 0.2667 0.2619 0.0380 0.0350 0.0354 An overlay of chromatogr the FLASH 4000 analyzin chromatogram is obtaine 173015 uV/sec while the glucose at 1 gram giving FIGURE 3. Overlay of ch TABLE 7. Nitrogen / Pro TABLE 5. Statistical data of starch samples at trace level. A %N) in the range of 0.0352 F G N% 0.0177 RSD % 0.0179 0.5618 0.0404 0.1430 0.0178 0.0404 0.0403 0.0162 0.0167 0.0162 0.0380 0.0382 0.0387 0.0356 0.0354 0.0365 0.0143 0.0150 0.0191 0.0188 1.7638 0.9414 1.6352 3.3787 1.1194 Protein % 0.1107 Sample 0.1120 0.5886 0.2525 0.1816 0.1115 0.2528 0.2519 0.1015 0.1046 0.1014 0.2378 0.2387 0.2419 0.2228 0.2212 0.2280 0.0914 0.0935 0.1196 0.1174 N RSD % 1.7750 0.8998 1.5872 3.3285 1.3128 1 0.2 3 0.0 2 0.0 Conclusion The FLASH 4000 analyze determination due to:. Excellent reproduc No memory effect Nitrogen determina effect. Combustion metho ISO, etc). AOAC is a trademark of The Ass Association of Cereal Chemists. trademark of The American Soci Fish Oil Organization. ISO is a tr of IMERYS MINERALS CALIFOR its subsidiaries This information is not intended t intellectual property rights of othe Thermo Scientific Poster Note • PN42212_PITTCON 2014_E_02/14S 5 amples in trace level analyzed g the sample type and nitrogen Table 6 shows the N/Protein data obtained of a slurry starch sample analysis. The liquid sample was adsorbed by the inert material Chromosorb (WAW 30/60 mesh) into the tin capsule and the sample weight used for analysis was 1.0 – 1.5 grams. mples. The protein content was dicated software using 6.25 as TABLE 6. Nitrogen / Protein data of slurry starch. N% e combustion and conversion of RSD % 0.0355 at trace level. N% Protein % 0.0177 0.1107 0.0404 0.2528 0.0162 0.1015 0.0380 0.2378 0.0404 0.2525 0.0179 0.1120 0.0356 0.2228 0.0354 0.2212 0.0382 0.2387 0.0191 0.1196 0.0188 0.1174 0.0365 0.2280 0.0143 0.0914 0.0150 0.0935 0.0167 0.1046 0.0162 0.1014 0.0403 0.2519 0.0387 0.2419 0.0178 0.1115 0.2200 0.2186 0.0354 0.2214 An overlay of chromatograms is shown in Figure 3 to demonstrate the performance of the FLASH 4000 analyzing samples at about 100 ppm nitrogen at 1 gram. The black chromatogram is obtained from sample F (about 150 ppm N) with a Nitrogen Area of 173015 uV/sec while the red chromatogram is the blank analysis obtained with glucose at 1 gram giving a Nitrogen Area of 34223 uV/sec. FIGURE 3. Overlay of chromatograms TABLE 7. Nitrogen / Protein data comparison RSD % 0.5886 0.2525 0.1816 0.1115 0.2528 0.2519 0.1015 0.1046 0.1014 0.2378 0.2387 0.2419 0.2228 0.2212 0.2280 0.0914 0.0935 0.1196 0.1174 1.7750 0.8998 1.5872 3.3285 1.3128 3.1968 0.2373 0.0350 Sample 0.1120 0.2291 3.1947 0.0380 ace level. 0.1107 RSD % 0.2216 0.0352 0.0366 Protein % Protein % FLASH 4000 Kjeldahl Method N% Protein % N% Protein % 1 0.2527 1.5794 0.2504 1.5650 3 0.0358 0.2237 0.0360 0.2250 2 0.0404 0.2525 0.0399 0.2494 Conclusion The FLASH 4000 analyzer demonstrates the best solution for Nitrogen / Protein determination due to:. Excellent reproducibility and accuracy. No memory effect when changing the sample and content of nitrogen. Nitrogen determination in a wide range from trace to high content without matrix effect. Combustion method is approved by official organizations (AOAC, AACC,AOCS, ISO, etc). AOAC is a trademark of The Association of Official Analytical Chemists. AACC is a trademark of The American Association of Cereal Chemists. AOCS is a trademark of The American Oil Chemists' Society. ASBC is a trademark of The American Society of Brewing Chemists. IFFO is a trademark of The International Fishmeal and Fish Oil Organization. ISO is a trademark of The International Standards Organization. Chromosorb is a trademark of IMERYS MINERALS CALIFORNIA, INC. All other trademarks are the property of Thermo Fisher Scientific and its subsidiaries This information is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others. 6 Nitrogen/Protein Determination in Starch by Flash Combustion using Large Sample Weight as an Alternative to the Kjeldahl Method www.thermoscientific.com ©2014 Thermo Fisher Scientific Inc. All rights reserved. ISO is a trademark of the International Standards Organization. AOAC is a trademark of The Association of Official Analytical Chemists. AACC is a trademark of The American Association of Cereal Chemists. AOCS is a trademark of The American Oil Chemists’ Society. ASBC is a trademark of The American Society of Brewing Chemists. IFFO is a trademark of The International Fishmeal and Fish Oil Organization. ISO is a trademark of The International Standards Organization. Chromosorb is a trademark of IMERYS MINERALS CALIFORNIA, INC. All other trademarks are the property of Thermo Fisher Scientific, Inc. and its subsidiaries. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details. 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