This document discusses two analytical chemistry methods: colorimetry and Kjeldahl. It provides details on:
- The principles, workings, and applications of colorimetry, which involves comparing color changes to determine small quantities of substances.
- The step-by-step process, reactions, and calculations involved in the Kjeldahl method to determine the nitrogen and protein content of samples. This includes destruction, distillation, and titration stages to convert organic nitrogen to ammonium sulfate then ammonia gas for analysis.
- References that provide further information on both methods and their uses in food and chemical analysis.
Spectroscopic, Thermal, Magnetic and conductimetric studies on some 7-hydroxy...IOSR Journals
7-hydroxy-4-methyl-8-(p-methylphenylazo)coumarin (L1) and 7-hydroxy-4-methyl-8-(p-methoxyphenylazo)coumarin (L2) have been prepared and characterized by elemental analysis, infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectra. The important infrared (IR) spectral bands corresponding to the active groups in the two ligands and the solid complexes under investigation were studied. Also the important fragments in the ligands and complexes were done using mass spectra and the main peaks were corresponding to the molecular weights of the ligands and complexes. The solid complexes have been synthesized and characterized by elemental and thermal analyses (TG and DTA) as well as by IR, 1H NMR, magnetic measurements, electronic transition, molar conductance, mass and electron spin resonance (ESR) spectra. The proposed steriochemical structures for the investigated metal complexes suggest octahedral geometry with respect to Mn, Co, Ni, Cu and Zn divalent metal ions with the investigated ligands 1:1 and 1:2 complexes and all of the formed complexes contain coordinated and hydrated water molecules. All of the prepared solid complexes behave as non-electrolytes in chloroform.
Spectroscopic, Thermal, Magnetic and conductimetric studies on some 7-hydroxy...IOSR Journals
7-hydroxy-4-methyl-8-(p-methylphenylazo)coumarin (L1) and 7-hydroxy-4-methyl-8-(p-methoxyphenylazo)coumarin (L2) have been prepared and characterized by elemental analysis, infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectra. The important infrared (IR) spectral bands corresponding to the active groups in the two ligands and the solid complexes under investigation were studied. Also the important fragments in the ligands and complexes were done using mass spectra and the main peaks were corresponding to the molecular weights of the ligands and complexes. The solid complexes have been synthesized and characterized by elemental and thermal analyses (TG and DTA) as well as by IR, 1H NMR, magnetic measurements, electronic transition, molar conductance, mass and electron spin resonance (ESR) spectra. The proposed steriochemical structures for the investigated metal complexes suggest octahedral geometry with respect to Mn, Co, Ni, Cu and Zn divalent metal ions with the investigated ligands 1:1 and 1:2 complexes and all of the formed complexes contain coordinated and hydrated water molecules. All of the prepared solid complexes behave as non-electrolytes in chloroform.
Oxidative Coupling: A Tranquil Approach for Determination of Selexipag by Vis...Ratnakaram Venkata Nadh
The present study is a first report on development of a spectrophotometric method for determination of selexipag (used to cure pulmonary arterial hypertension) in bulk and tablet formulation and its validation. The basis of the proposed method is formation of a chromophore (of λ max 600 nm) in presence of acidic ferric chloride by oxidative coupling reaction between selexipag and MBTH (3-methylbenzo-thiazolin-2-one hydrazone) solution. Regression analysis (r > 0.999) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (5 – 30 μg mL-1). As per the existing guidelines of ICH, various parameters of the method were tested for validation. Low values of R.S.D. (< 2%) were observed indicating that the proposed method is reproducible, accurate and precise
Kinetics of Ruthenium(III) Catalyzed and Uncatalyzed Oxidation of Monoethanol...Ratnakaram Venkata Nadh
Kinetics of uncatalyzed and ruthenium(III) catalyzed oxidation of monoethanolamine by N-bromosuccinimide
(NBS) has been studied in an aqueous acetic acid medium in the presence of sodium acetate
and perchloric acid, respectively. In the uncatalyzed oxidation the kinetic orders are: the first order in NBS,
a fractional order in the substrate. The rate of the reaction increased with an increase in the sodium acetate
concentration and decreased with an increase in the perchloric acid concentration. This indicates that free
amine molecules are the reactive species. Addition of halide ions results in a decrease in the kinetic rate,
which is noteworthy. Both in absence and presence of a catalyst, a decrease in the dielectric constant of the
medium decreases the kinetic rate pointing out that these are dipole—dipole reactions. A relatively higher
oxidation state of ruthenium i.e., Ru(V) was found to be the active species in Ru(III) catalyzed reactions. A
suitable mechanism consistent with the observations has been proposed and a rate law has been derived to
explain the kinetic orders.
Some Excess Properties of Ternary Liquid Mixture of Water, Methanol, Ethanol ...paperpublications3
Abstract: Densities and viscosities of ternary liquid mixtures of water, methanol, ethanol of volume by volume ratio of 1:1:1 have been measured at 308.15, 313.15., 318.15, 323.15, 328.15, K .From the density and viscosity data the values of various properties, Excess volume (VE) Excess viscosity (µE) and Excess Gibb’s free energy of activation of flow (ΔGE) have been determined. On the basis of the values of interaction parameters and various excess properties, the nature of molecular interactions between the components of mixtures has been explained.
Keywords: Viscosity, Liquids, Density, Ternary Mixture, Water, Methanol and Ethanol, Excess Volume, Excess Viscosity, Gibb’s Free Energy.
Ultrasonic and Volumetric Investigations of -Butyrolactone with Aliphatic Al...IJERA Editor
Densities () and speeds of sound (u) have been determined for the binary liquid mixtures of -butyrolactone (GBL) with 1-propanol (1-Pro), 2-propanol (2-Pro), 1-butanol (1-But) and 2-butanol (2-But) at 303.15, 308.15, and 313.15 K and entire composition range. From the experimental results, the excess molar volume (VE), and deviation in isentropic compressibility (s) were calculated. The computed properties have been fitted to a Redlich-Kister type polynomial equation to derive binary coefficients and standard deviations.
Some physicochemical properties such as density, refractive index, solubility, conductance, dissociation constant etc. have been studied for some newly synthesized chalcones in different solvents at 308.15 K.
Mechanism of the Reaction of Plasma Albumin with Formaldehyde in Ethanol - Wa...IOSR Journals
The Spectrophotometric determination of the acid dissociation/ionisation constant (pKa) of plasma albumin-formaldehyde adduct in both water solution and Ethanol solutions was carried out in this study. The pKa values obtained in both media were used to establish the Bronsted-linear type constants from plots of pKa against logarithm of second order rate constants obtained at varying pHs in the study. The result of the pKa values obtained in both water solution and ethanol-water mixtures were found to be in the range of 5.0 - 8.0. This pointed to the fact that only lysine residue with pKa value 8.3 that might have possibly reacted with formaldehyde in this reaction of all the known amino acid residues in plasma albumin. The corresponding Brønsted-type plots proportionality constants (β) for the reaction in water and ethanol-water mixtures were found to be β = 0.059 and 0.0057 respectively. The reaction mechanisms that have low values for proportionality constants α or β are considered to have a transition state closely resembling the reactant with little proton transfer (Cox et al, 1988). Thus, one would suggest that the cross-linking of formaldehyde with plasma albumin in water and ethanol-water mixtures proceeds through little proton transfer
Reaction of aniline with ammonium persulphate and concentrated hydrochloric a...Maciej Przybyłek
In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.
Mannich Synthesis Under Ionic Liquid [Et3NH][HSO4] CatalysisIOSRJAC
Ionic liquid [Et3NH][HSO4] was found to be a particularly efficient catalyst for the synthesis of β- amino carbonyl pyrimidines through the Mannich condensation reaction of substituted pyrimidin-2(1H)-ones, cyclohexanone and 4-fluro/chlorobenzaldehyde under ultrasonic irradiation at room temperature. The present methodology offers several advantages such as excellent yields, simple procedure and mild conditions.
Oxidative Coupling: A Tranquil Approach for Determination of Selexipag by Vis...Ratnakaram Venkata Nadh
The present study is a first report on development of a spectrophotometric method for determination of selexipag (used to cure pulmonary arterial hypertension) in bulk and tablet formulation and its validation. The basis of the proposed method is formation of a chromophore (of λ max 600 nm) in presence of acidic ferric chloride by oxidative coupling reaction between selexipag and MBTH (3-methylbenzo-thiazolin-2-one hydrazone) solution. Regression analysis (r > 0.999) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (5 – 30 μg mL-1). As per the existing guidelines of ICH, various parameters of the method were tested for validation. Low values of R.S.D. (< 2%) were observed indicating that the proposed method is reproducible, accurate and precise
Kinetics of Ruthenium(III) Catalyzed and Uncatalyzed Oxidation of Monoethanol...Ratnakaram Venkata Nadh
Kinetics of uncatalyzed and ruthenium(III) catalyzed oxidation of monoethanolamine by N-bromosuccinimide
(NBS) has been studied in an aqueous acetic acid medium in the presence of sodium acetate
and perchloric acid, respectively. In the uncatalyzed oxidation the kinetic orders are: the first order in NBS,
a fractional order in the substrate. The rate of the reaction increased with an increase in the sodium acetate
concentration and decreased with an increase in the perchloric acid concentration. This indicates that free
amine molecules are the reactive species. Addition of halide ions results in a decrease in the kinetic rate,
which is noteworthy. Both in absence and presence of a catalyst, a decrease in the dielectric constant of the
medium decreases the kinetic rate pointing out that these are dipole—dipole reactions. A relatively higher
oxidation state of ruthenium i.e., Ru(V) was found to be the active species in Ru(III) catalyzed reactions. A
suitable mechanism consistent with the observations has been proposed and a rate law has been derived to
explain the kinetic orders.
Some Excess Properties of Ternary Liquid Mixture of Water, Methanol, Ethanol ...paperpublications3
Abstract: Densities and viscosities of ternary liquid mixtures of water, methanol, ethanol of volume by volume ratio of 1:1:1 have been measured at 308.15, 313.15., 318.15, 323.15, 328.15, K .From the density and viscosity data the values of various properties, Excess volume (VE) Excess viscosity (µE) and Excess Gibb’s free energy of activation of flow (ΔGE) have been determined. On the basis of the values of interaction parameters and various excess properties, the nature of molecular interactions between the components of mixtures has been explained.
Keywords: Viscosity, Liquids, Density, Ternary Mixture, Water, Methanol and Ethanol, Excess Volume, Excess Viscosity, Gibb’s Free Energy.
Ultrasonic and Volumetric Investigations of -Butyrolactone with Aliphatic Al...IJERA Editor
Densities () and speeds of sound (u) have been determined for the binary liquid mixtures of -butyrolactone (GBL) with 1-propanol (1-Pro), 2-propanol (2-Pro), 1-butanol (1-But) and 2-butanol (2-But) at 303.15, 308.15, and 313.15 K and entire composition range. From the experimental results, the excess molar volume (VE), and deviation in isentropic compressibility (s) were calculated. The computed properties have been fitted to a Redlich-Kister type polynomial equation to derive binary coefficients and standard deviations.
Some physicochemical properties such as density, refractive index, solubility, conductance, dissociation constant etc. have been studied for some newly synthesized chalcones in different solvents at 308.15 K.
Mechanism of the Reaction of Plasma Albumin with Formaldehyde in Ethanol - Wa...IOSR Journals
The Spectrophotometric determination of the acid dissociation/ionisation constant (pKa) of plasma albumin-formaldehyde adduct in both water solution and Ethanol solutions was carried out in this study. The pKa values obtained in both media were used to establish the Bronsted-linear type constants from plots of pKa against logarithm of second order rate constants obtained at varying pHs in the study. The result of the pKa values obtained in both water solution and ethanol-water mixtures were found to be in the range of 5.0 - 8.0. This pointed to the fact that only lysine residue with pKa value 8.3 that might have possibly reacted with formaldehyde in this reaction of all the known amino acid residues in plasma albumin. The corresponding Brønsted-type plots proportionality constants (β) for the reaction in water and ethanol-water mixtures were found to be β = 0.059 and 0.0057 respectively. The reaction mechanisms that have low values for proportionality constants α or β are considered to have a transition state closely resembling the reactant with little proton transfer (Cox et al, 1988). Thus, one would suggest that the cross-linking of formaldehyde with plasma albumin in water and ethanol-water mixtures proceeds through little proton transfer
Reaction of aniline with ammonium persulphate and concentrated hydrochloric a...Maciej Przybyłek
In this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.
Mannich Synthesis Under Ionic Liquid [Et3NH][HSO4] CatalysisIOSRJAC
Ionic liquid [Et3NH][HSO4] was found to be a particularly efficient catalyst for the synthesis of β- amino carbonyl pyrimidines through the Mannich condensation reaction of substituted pyrimidin-2(1H)-ones, cyclohexanone and 4-fluro/chlorobenzaldehyde under ultrasonic irradiation at room temperature. The present methodology offers several advantages such as excellent yields, simple procedure and mild conditions.
The most frequently used methods for measuring protein content in foods include the Kjeldahl method, Dumas method, direct measurement methods using UV-spectroscopy and refractive index measurement. Each method has advantages and disadvantages
Metabolomic and thermodynamic analysis of C. thermocellum strains engineered ...Jordan Brown
This presentation details a preliminary integrated metabolomic and thermodynamic analysis towards the goal of improving the ethanol yield in C. thermocellum.
06-04-2024 - NYC Tech Week - Discussion on Vector Databases, Unstructured Data and AI
Round table discussion of vector databases, unstructured data, ai, big data, real-time, robots and Milvus.
A lively discussion with NJ Gen AI Meetup Lead, Prasad and Procure.FYI's Co-Found
Analysis insight about a Flyball dog competition team's performanceroli9797
Insight of my analysis about a Flyball dog competition team's last year performance. Find more: https://github.com/rolandnagy-ds/flyball_race_analysis/tree/main
Chatty Kathy - UNC Bootcamp Final Project Presentation - Final Version - 5.23...John Andrews
SlideShare Description for "Chatty Kathy - UNC Bootcamp Final Project Presentation"
Title: Chatty Kathy: Enhancing Physical Activity Among Older Adults
Description:
Discover how Chatty Kathy, an innovative project developed at the UNC Bootcamp, aims to tackle the challenge of low physical activity among older adults. Our AI-driven solution uses peer interaction to boost and sustain exercise levels, significantly improving health outcomes. This presentation covers our problem statement, the rationale behind Chatty Kathy, synthetic data and persona creation, model performance metrics, a visual demonstration of the project, and potential future developments. Join us for an insightful Q&A session to explore the potential of this groundbreaking project.
Project Team: Jay Requarth, Jana Avery, John Andrews, Dr. Dick Davis II, Nee Buntoum, Nam Yeongjin & Mat Nicholas
06-04-2024 - NYC Tech Week - Discussion on Vector Databases, Unstructured Data and AI
Discussion on Vector Databases, Unstructured Data and AI
https://www.meetup.com/unstructured-data-meetup-new-york/
This meetup is for people working in unstructured data. Speakers will come present about related topics such as vector databases, LLMs, and managing data at scale. The intended audience of this group includes roles like machine learning engineers, data scientists, data engineers, software engineers, and PMs.This meetup was formerly Milvus Meetup, and is sponsored by Zilliz maintainers of Milvus.
Techniques to optimize the pagerank algorithm usually fall in two categories. One is to try reducing the work per iteration, and the other is to try reducing the number of iterations. These goals are often at odds with one another. Skipping computation on vertices which have already converged has the potential to save iteration time. Skipping in-identical vertices, with the same in-links, helps reduce duplicate computations and thus could help reduce iteration time. Road networks often have chains which can be short-circuited before pagerank computation to improve performance. Final ranks of chain nodes can be easily calculated. This could reduce both the iteration time, and the number of iterations. If a graph has no dangling nodes, pagerank of each strongly connected component can be computed in topological order. This could help reduce the iteration time, no. of iterations, and also enable multi-iteration concurrency in pagerank computation. The combination of all of the above methods is the STICD algorithm. [sticd] For dynamic graphs, unchanged components whose ranks are unaffected can be skipped altogether.
The Building Blocks of QuestDB, a Time Series Databasejavier ramirez
Talk Delivered at Valencia Codes Meetup 2024-06.
Traditionally, databases have treated timestamps just as another data type. However, when performing real-time analytics, timestamps should be first class citizens and we need rich time semantics to get the most out of our data. We also need to deal with ever growing datasets while keeping performant, which is as fun as it sounds.
It is no wonder time-series databases are now more popular than ever before. Join me in this session to learn about the internal architecture and building blocks of QuestDB, an open source time-series database designed for speed. We will also review a history of some of the changes we have gone over the past two years to deal with late and unordered data, non-blocking writes, read-replicas, or faster batch ingestion.
1. Nama : Rauza Tinur
Nim : 2105279
Tugas : Analisi Pangan dan Obat
A. METODE KOLORIMETRI
Menurut J. Bassett (1991) Kolorimetri adalah metode perbandingan
menggunakan perbedaan warna. Metode kolorimetri mengukur warna
suatu zat sebagai perbandingan. Kelebihan metode kolorimetri adalah
kemudahannya dalam menetapkan kuantitas zat yang sangat kecil.
Metode kolorimetri biasa digunakan dalam analisis kimia, metode
kolorimetri memiliki batas pada penetapan konstituen yang ada dalam kuantitas
yang kurang dari satu atau dua persen. Alat kolorimetri yang menggunakan sensor
atau sel fotolistrik disebut kolorimetri fotolistrik.
Menurut Firdaus (2014) Prinsip kerja kolorimetri adalah
ketika cahaya melewati sebuah benda, maka sebagian dari cahaya diserap, dan
akibatnya terjadi penurunan dalam berapa banyak cahaya yang dipantulkan oleh
mediumnya. Kolorimeter akan berubah sehingga pengguna dapat menganalisis
konsentrasi zat tertentu dalam medium tersebut. Perangkat ini bekerja atas
dasar hukum Beer-Lambert, yang menyatakan bahwa penyerapan cahaya yang
ditransmisikan melalui medium berbanding lurus dengan konsentrasi medium.
Kolorimetri melewati panjang gelombang cahaya tertentu melalui larutan,
dan kemudian mengukur cahaya yang datang melalui di sisi lain. Dalam
kebanyakan kasus, lebih terkonsentrasi larutannya yaitu cahaya lampu akan lebih
banyak diserap, dan dapat dilihat pada perbedaan antara cahaya pada sumber
asalnya dan setelah itu melewati solusi.
Untuk mengetahui konsentrasi suatu sampel, maka sampel dilihat dari
konsentrasi diketahui yang pertama disiapkan dan diuji. Ini kemudian diplot
pada grafik dengan konsentrasi pada satu sumbu dan absorbansi di sisi lain untuk
membuat kurva kalibrasi, ketika sampel tidak diketahui diuji hasilnya
dibandingkan dengan sampel yang dikenal pada kurva untuk menentukan
konsentrasi. Beberapa jenis kolorimetri otomatis akan membuat kurva kalibrasi
didasarkan pada kalibrasi awal.
2. Alat pada Metode Kalorimetri
Keterangan gambar:
(1) Pemilih panjang gelombang,
(2) Tombol pencetak,
(3) Penyesuaian faktor konsentrasi,
(4) Pemilih mode UV (lampu Deuterium),
(5) Pembacaan,
(6) Kompartemen sampel,
(7) Kontrol nol (100% T ),
(8) Tombol sensitivitas,
(9) Tombol ON/OFF
B. METODE KJELDAHL
Jelaskan fungsi dari setiap tahapan, reaksi yang terjadi dan bagaimana
perhitungan penetapan kadar protein nya?
Metode Kjeldahl atau digesti Kjeldahl dalam kimia analitik adalah metode
untuk penentuan kadar nitrogen organik dalam zat kimia seperti amonia.
Metode ini dikembangkan oleh Johan Kjeldahl (1883), Tujuan metode
kjeldahl adalah untuk menentukan kadar protein dalam suatu bahan.
Metode ini dapat diterapkan pada senyawa-senyawa organik maupun anorganik
meliputi makanan, daging, biji-bijian, air limbah, tanah dan banyak sampel yang
lainnya.
Prinsip metode Kjeldahl adalah berdasarkan perubahan nitrogen organik
menjadi garam amonia dengan cara destruksi dengan asam sulfat pekat dan
pemnambahan suatu katalisator yang sesuai, hasil destruksi didestilasi dalam
suasana basa kuat.
Metode ini terdiri dari pemanasan zat dengan asam sulfat, yang menguraikan
zat organik melalui oksidasi untuk membebaskan nitrogen menjadi amonium sulfat.
Pada langkah ini, kalium sulfat ditambahkan untuk meningkatkan titik
didih medium (dari 337 °C - 373 °C).
Reaksi penguraian sampel dinyatakan selesai saat warna pelarut berubah dari
gelap menjadi cerah dan tidak berwarna. Larutan kemudian disuling dengan sejumlah
kecil natrium hidroksida, yang mengubah garam amonium menjadi amonia. Gas
amonia terbentuk dan jumlah nitrogen yang terdapat dalam sampel dapat ditentukan
melalui titrasi kembali.
3. Ujung kondensor dicelupkan ke dalam larutan penampung asam borat.
Amonia bereaksi dengan asam dan sisa asam kemudian dititrasi dengan
larutan natrium karbonat dan indikator metil jingga.
Penguraian: Sampel + H2SO4 → (NH4)2SO4(aq) + CO2(g) + SO2(g) + H2O(g)
Pelepasan amonia: (NH4)2SO4(aq) + 2NaOH → Na2SO4(aq)+2H2O(l)+ 2NH3(g)
Penangkapan amonia: B(OH)3 + H2O + NH3 → NH4
+ + B(OH)4
−
Titrasi kembali: B(OH)3 + H2O + Na2CO3 → NaHCO3(aq) + NaB(OH)4(aq) +
CO2(g) + H2O
Alat dari Metode Kjedahl:
Menurut Julian McClements (2007), Keunikan, ketepatan dan kemampuan
reproduktifitas metode Kjeldahl menjadikannya metode yang diakui secara
internasional untuk mengukur kandungan protein dalam makanan dan ini
merupakan metode standar yang dengannya semua metode lain dinilai.
Namun, metode ini tidak menunjukkan kadar protein yang tepat, karena
nitrogen nonprotein juga ikut terukur bersama nitrogen protein. Hal ini dibuktikan
dengan insiden makanan hewan peliharaan 2007 dan skandal susu Tiongkok tahun
2008, ketika melamin, bahan kimia kaya nitrogen, ditambahkan dalam bahan baku
agar kandungan protein menjadi tinggi. Selain itu, faktor koreksi yang berbeda
diperlukan untuk protein yang berbeda guna memperhitungkan urutan asam amino
yang berbeda pula.
Kelemahan lainnya, seperti perlunya pemakaian asam sulfat pekat pada suhu
tinggi dan waktu pengujian yang relatif lama (satu jam atau lebih), membuatnya
tidak seefektif metode Dumas dalam penetapan kadar protein kasar.
Metode Kjeldahl atau digesti Kjeldahl ini terbagi menjadi 3 yaitu:
4. 1. Tahap Destruksi
Destruksi merupakan suatu perlakuan untuk melarutkan atau mengubah
sampel menjadi bentuk materi yang dapat diukur sehingga kandungan unsur-unsur
didalamnya dapat dianalisis.
Pada tahap ini sampel dipanaskan dengan asam sulfat pekat sehingga terjadi
dekstruksi menjadi unsur-unsurnya, dimana seluruh N organik dirubah menjadi N
anorganik yaitu elemen karbon (C) teroksidasi menjadi karbondioksida (CO2) dan
hidrogen (H) teroksidasi menjadi air (H2O), sedangkan elemen nitrogennya akan
berubah menjadi ammonium sulfat (NH4)2SO4. Asam sulfat yang dipergunakan
untuk dekstruksi harus dalam jumlah yang cukup dan diperhitungkan untuk dapat
menguraikan bahan protein, lemak, dan karbohidrat didalam sampel.
Untuk mempercepat dekstruksi maka ditambahkan katalisator,menggunakan
kalium sulfat (K2SO4) dan tembaga (II) sulfat (CuSO4). Dengan penambahan
katalisator ini, maka titik didih asam sulfat akan ditinggikan sehingga proses
dekstruksi akan berjalan dengan cepat. Tiap 1 gram kalium sulfat akan mampu
meningkatkan titik didih asam sulfat 3ºC. Suhu dekstruksi berkisar antara 370ºC-
410ºC. Proses dekstruksi diakhiri jika larutan telah menjadi warna hijau jernih.
Reaksi yang terjadi pada proses dekstruksi adalah:
Protein + H2SO4 Katalisator → (NH4)2SO4 + CO2 + SO2 + H2O
N organik/anorganik + H2SO4 → (NH4)2SO4 + H2O + CO2
2. Tahap Destilasi
Destilasi adalah suatu metode pemisahan analit dari komponennya dengan
menggunakan prinsip dasar perbedaan titik didih. Tahap desitilasi amonium sulfat
(NH4)2SO4 yang terbentuk pada tahap dekstruksi dipecah menjadi amonia (NH3)
dengan penambahan NaOH sampai kalis dan dipanaskan.
Amonia yang dibebaskan selanjutnya akan ditangkap oleh larutan baku asam.
Larutan baku asam yang dipakai adalah asam sulfat (H2SO4), supaya kontak antara
asam dan amonia berjalan sempurna, maka ujung selang pengalir destilat harus
tercelup kedalam larutan asam. Destilasi diakhiri bila semua amonia terdestilasi
sempurna yang ditandai dengan destilat tidak bereaksi basa.
Reaksi yang terjadi pada tahap destilasi yaitu:
(NH4)2SO4 + 2 NaOH →Na2SO4 + 2 H2O + 2 NH3
5. 3. Tahap Tritrasi
Titrasi merupakan metode analisis kimia secara kuantitatif untuk
menentukan konsentrasi suatu reaktan. Oleh karena pengukuran volum berperan
penting dalam titrasi, maka teknik ini juga disebut dengan analisis volumetrik.
Penampung destilat yang digunakan adalah asam sulfat berlebih, maka sisa
asam sulfat yang tidak bereaksi dengan amonia dititrasi dengan NaOH 0,02 N
menggunakan indikator mengsel. Titik akhir titrasi dapat ditandai dengan
perubahan warna dari warna ungu menjadi hijau,
Indikator Mengsel dibuat dengan mencampurkan 100 mg metilen
merah dan 30 mg metilen biru dalam 60 ml alkohol 96 kemudian diencerkan
dengan aquadestilata yang telah didihkan hingga 100 ml Sudarmadji, dkk.,
1989.
Reaksi yang terjadi pada tahap titrasi yaitu:
NH3 + H2SO4 → (NH4)2SO4
Kelebihan H2SO4 + 2 NaOH → Na2SO4 + 2 H2O
Kadar protein dihitung dengan persamaan berikut ini:
Kadar Protein (%) =(Vb-Vt)/Berat sampel (mg)×N NaOH ×14,007×FK ×100%
Fk = Faktor konversi atau perkalian = 6,25
Besarnya faktor konversi nitrogen tergantung pada persentase nitrogen yang
menyusun protein dalam bahan pangan yang dianalisa tersebut.
Perhitungan:
% N =
(𝑉𝑏 − 𝑉𝑠) 𝑥 𝑁 𝑁𝑎𝑂𝐻 𝑥 𝛷 𝑥 𝐵𝐸 𝑁
𝑊𝑠 𝑥 1000
𝑥100%
% P = % N 𝑥 Faktor Konversi
Keterangan :
Vb = Volume blanko (ml),
Vs = Volume titrasi sampel (ml),
N NaOH = Normalitas NaOH baku,
BE Nitrogen = 14,008 ,
Ws = Berat sampel (gram)
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