Terminal report on the
Terminal report on the
On the Job Training
On the Job Training
Workplace:
Workplace:
DEPARTMENTOF SCIENCE AND
DEPARTMENTOF SCIENCE AND
TECHNOLOGY REGION 9
TECHNOLOGY REGION 9
Presented by:
Presented by:
Aranton, Raymond Roy O.
Aranton, Raymond Roy O.
BS Chemistry 3
BS Chemistry 3
Presented to:
Presented to:
Prof. Damiana M. Martinez
Prof. Damiana M. Martinez
Adviser
Adviser
ABOUT THE DOST LOGO ABOUT THE DOST LOGO
Excellence, Relevance, Cooperation and Cost-effectiveness Excellence, Relevance, Cooperation and Cost-effectiveness
The logo of the Department of Science and Technology (DOST) consists essentially of The logo of the Department of Science and Technology (DOST) consists essentially of four circles joined together side by side to form a square. The circles symbolize unit particles, the four circles joined together side by side to form a square. The circles symbolize unit particles, the building blocks of nature which are the subject and substance of science and technology. The building blocks of nature which are the subject and substance of science and technology. The
ci
circrcle le dedesisign gn gigives ves an an ilillulusision on of of momovemvement ent sisigngnififyiying ng prprogrogresess s ththrorough ugh ScScieiencnce e anandd Technology.
Technology.
•
• The space in the center of the joined circles forms a four-pointed star The space in the center of the joined circles forms a four-pointed star
symbolic of scientific creativity. symbolic of scientific creativity.
•
• The logo' s three-color scheme represents the unknown(black), truth andThe logo' s three-color scheme represents the unknown(black), truth and
enlightenment (white) and progress (blue). enlightenment (white) and progress (blue).
•
• The logo's four circles represent the four guiding principles in our S&TThe logo's four circles represent the four guiding principles in our S&T
development:
development:Excellence, Relevance, Cooperation and Cost-effectivenessExcellence, Relevance, Cooperation and Cost-effectiveness
MANDATE MANDATE
Th
The e DeDepapartrtmement nt of of ScScieiencnce e anand d TeTechnchnolology ogy (D(DOSOST) T) is is ththe e prprememieiere re scscieiencnce e andand technology body in the country charged with the twin mandate of providing central direction, technology body in the country charged with the twin mandate of providing central direction, leadership and coordination of all scientific and technological activities, and of formulating leadership and coordination of all scientific and technological activities, and of formulating policies, programs and projects to support national development.
policies, programs and projects to support national development.
Vision Vision
An
An excexcellellent ent proprovidvider er of of new new knoknowlewledge dge and and useuseful ful inninnovatovationions, s, comcompetpetent ent humhumanan resources and quality S&T services that uplift the socio-economic well-being of the Filipino resources and quality S&T services that uplift the socio-economic well-being of the Filipino people and ensure sustainability for future generations.
Mission
To provide central direction, leadership, and coordination of scientific and technological efforts and ensure that the results therefrom are geared and utilized in areas of maximum economic and social benefits for the people.
PRINCIPLES
In the current arena of globalization, science and technology have become the most important factor for national economic growth and source of competitive advantage. Recognition of this fact has led technologically-progressive nations and firms to invest substantial resources in research and development (R&D), technology acquisition and adaptation, S&T education and training, and S&T infrastructure.
No less than the President has identified science and technology (S&T) as a principal means to fuel the nation's economy and ensure the well-being of all Filipinos.
In line with the Medium-Term Philippine Development Plan, the Department of Science and Technology (Department or DOST) will pursue programs and activities guided by the principles of competence, competitiveness and conscience. Accordingly, the Department has adopted the following vision: A competent and competitive science and technology community with a social conscience.
The Medium-Term Plan of the DOST, for the period 1999 - 2004, presents the three-pronged approach which the science department shall adopt to realize this vision.
Firstly, by implementing high priority flagship programs to develop competence and competitiveness and address the needs of the poor and the disadvantaged. Secondly, by strengthening and giving sharper focus to continuing programs in science and technology to make them more relevant to the goals and thrusts of the current administration. And thirdly, by improving S&T governance and management, including institutional reforms for a more productive and efficient science community.
In pursuit of this vision, the Department will work with the S&T community on the urgent task of addressing the needs of Philippine society in proportion to their importance. In so doing, the Department enters into a new social contract with the Filipino people.
FUNCTIONS
1. Formulate and adopt a comprehensive National Science and Technology Plan, and monitor and coordinate its funding and implementation;
2. Promote, assist and, where appropriate, undertake scientific and technological research and development in areas identified as vital to the country's development;
3. Promote the development of indigenous technology and the adaptation and innovation of suitable imported technology, and in this regard, undertake technology development up to commercial stage;
4. Undertake design and engineering works to complement research and development functions;
5. Promote, assist and, where appropriate, undertake the transfer of the results of scientific and technological research and development to their end-users;
6. Promote, assist and, where appropriate, undertake the technological services needed by agriculture, industry, transport, and the general public;
7. Develop and maintain an information system and databank on science and technology; 8. Develop and implement programs for strengthening scientific and technological
capabilities through manpower training, infrastructure and institution-building; 9. Promote public consciousness in science and technology; and,
10.Undertake policy research, technology assessment, feasibility and technical studies.
POLICY DIRECTIONS
1. Forge more active partnerships in technology development and utilization
To encourage the active involvement of both the public and private sectors in joint technology development and utilization to increase productivity and quality of products in agriculture, industry and the service sectors
2. Pursue more active partnerships in defining directions and priorities
To promote consultation and cooperation between the public and private sectors in defining the directions and priorities of research and development, technology transfer and manpower development activities
3. Adopt a strong client-oriented research and development thrust
To support R&D in the government sector by allocating sufficient budget and manpower on projects that would increase the Philippine's capacity to export, accelerate countryside development and promote sustainable development. R&D will be conducted in areas which address specific needs of clients specially agri/aqua enterprises and small and medium local manufacturers.
To formulate appropriate laws and administrative policies to private sector investment in science and techno-logy, the private sector being the engine of growth and technological innovation
5. Aggressively acquire and adapt technology from domestic and foreign sources
To support the transfer of technology from domestic and foreign sources including utilization of local and foreign experts by providing incentives and other privileges
6. Upgrade S&T services
To upgrade and expand S&T services and facilities to ensure that local products meet global standards of excellence
7. Develop and upgrade S&T manpower
To increase the quality and quantity of scientists and engineers and encourage the private sector to play a bigger role in developing the nation's manpower base
8. Strengthen international S&T linkages
To expand and strengthen scientific and technical cooperation with other countries through technical assistance programs on techno-logy transfer, joint research undertakings and exchange of experts in identified priority areas
9. Promote science and technology culture
To increase awareness and appreciation of the usefulness of science and technology in everyday life especially among the youth
10. Improve the welfare of researchers, scientists and technologists
To improve the work environment and incentives for S&T personnel including appropriate rewards for significant contributions to national socio-economic growth
DOST IX REGIONAL STANDARDS AND TESTING LABORATORIES (RSTL)
I. INTRODUCTION:
The DOST IX - Regional Standards and Testing Laboratories (RSTL) offers testing and calibration services to various customers in the region. With the effort of providing better metrological, microbiological, physical and chemical laboratory tests and analyses, RSTL had continually improved its services paving the way for the Microbiological Laboratory and Physical & Chemical Laboratory to maintain its ISO 17025 Accreditation. ISO 17025 (General Requirements for the Competence of Testing and Calibration Laboratories) Accreditation is granted to laboratories that assures its customers of precision, accuracy and repeatability of test results.
From this, the Western Mindanao State University, College of Science and Mathematics, Chemistry Department let students taking up Bachelor of Science in Chemistry to conduct an ON the Job Training in this agency for them to enhance their capabilities in the field of science especially in chemistry also as a threshold for their future, an experience that they can apply in their own workplace which is the laboratory.
Physical and Chemical Laboratory
The ISO 17025 accredited physical and chemical laboratory conducts quantitative analyses on the following types of sample: raw and processed foods, fruit and fruit products, water and wastewater, soap and related products, condiments and spices, feeds, charcoal, limestone, rubber latex and
raw seaweeds.
Microbiological Laboratory
The ISO 17025 Accredited Microbiological Laboratory offers analyses for raw and processed food products and water samples. Among these analyses are: Aerobic Plate Count
-Coliform Count - Escherichia coli Count - Yeast and Molds - Salmonella Detection - Fecal Coliform Count - Staphylococcus aureus. - Vibrio cholera - Pseudomonas aeruginusa.
Metrology Laboratory
The metrology laboratory performs volumetric and mass calibrations. The volumetric calibrations included calibration of vehicle tanks, proving tanks, calibrating buckets, storage tanks and flow meters while mass calibration covers calibration of scales and test weights from 2 kg to 60 kg OIMLClass M.
DOST IX Regional Standards and Testing Laboratories implement QMS (Quality Management System) in accordance with ISO (International Organization of Standardization)/ IEC (International Electrotechnical Commission) 17025 with a competent goal of “General Requirements for the competence of testing and calibration laboratories”
Quality Policy (Management System) 1. Quality Objectives
II. OBJECTIVES of the On the Job Training:
1. To determine the vision and mandate that governs the actions and activities of the assigned industry or government agency for the welfare of mankind,
2. To be able to get hold of knowledge for the conductance of chemistry subject in their laboratory activities,
3. To be able to determine the different standard parameters used in the laboratory of the assigned industry or government agency,
Provide TIMELY and ACCURATE microbiologial and chemical testing as well as calibration services
4. To be able to acquire experience on the use of laboratory techniques, methods of each parameters, and other useful action to develop the skill of the students, and
5. To be able to assist the laboratory personnel during experiments or in any manner.
III. PRINCIPLES AND METHODS OF ANALYSIS:
The following test methods of this report paper are observed or done by the student in training during the actual experiments conducted in the assigned industry or government agency.
1. Biochemical Oxygen Demand (BOD) of Water
Incubation Method
AOAC Official Method 973.44
Principle:
The method consists of filling with sample, to overflowing, an airtight bottle of the specified size and incubating it at the specified temperature for 5 d. Dissolved oxygen is measured initially and after incubation, and the BOD is computed from the difference between initial and final DO. Because the initial DO is determined shortly after the dilution is made, all oxygen uptake occurring after this measurement is included in the BOD me asurement.
Apparatus:
a. Incubation bottles: 250 or 300 mL glass stopper
b. Air incubator or water bath, thermostatically controlled at 20 ± 1oC.
Reagents:
a. Phosphate buffer solution: Dissolve 8.5 g KH2PO4, 21.75 g K 2HPO4, 33.4 g Na2HPO4·7H2O, and
1.7 g NH4Cl in about 500 mL distilled water and dilute to 1 L. The pH should be 7.2 without
further adjustment. Alternatively, dissolve 42.5 g KH2PO4or 54.3 g K 2HPO4in about 700 mL
distilled water. Adjust pH to 7.2 with 30% NaOH a nd dilute to 1 L.
b. Magnesium sulfate solution: Dissolve 22.5 g MgSO4·7H2O in distilled water and dilute to 1 L.
c. Calcium chloride solution: Dissolve 27.5 g CaCl2in distilled water and dilute to 1 L.
e. Alkali – Dissolve 40 g sodium hydroxide in distilled water. Dilute to 1 L.
f. Sodium sulfite solution: Dissolve 1.575 g Na2SO3in 1000 mL distilled water. This solution is not
stable; prepare daily.
g. Glucose-glutamic acid solution: Dry reagent-grade glucose and reagent-grade glutamic acid at 103oC for 1 h. Add 150 mg glucose and 150 mg glutamic acid to distilled water and dilute to 1 L.
Prepare fresh immediately before use. h. Water sample
i. Seeding material Procedure of BOD
1. Place sample in BOD bottle (250-300 mL) no air (2 sets) 2. Add the seeding material at different dilution
3. Add the phosphate buffer solution
4. Half of the set is keep for 5 days at 20°C for incubation 5. The remaining set id added 2 mL MnSO4
6. Add 2 mL azide and shake until orange ppt. let stand 7. Add 2 mL conc. H2SO4, shake until ppt. are dissolved
8. Discard 100 mL and add starch indicator
9. Titrate w/ 0.025 N Na2S2O3, until end point light blue
10. Record volume, as initial BOD Preparation from Seeding
Dilution: no. of sample x 3 Liters + 1 liter= vol. of distilled water Preparation of nutrients (Seeding)
a. Prepare the distilled water in a jar (polyethylene- calibrated)
b. Add nutrients 2 mL/ liter (2 mL) (13)= 26 mL
Cacl2sol’n, Phosphate buffer, FeCl36H2O, MgSO4sol’n
c. Aerate for 30 min. using air pump (to be used for the blank)
Fig.1. Digital titrator containing 0.025 N Na2S2O3
d. To the remaining nutrient solution add 20 mL/ L of seed and aerate for 15 min. (to be added to the sample)
Preparation of BOD seed control (2 trials each) a. Blank + nutrients
b. Add 6 mL seed + nutrients c. Add 15 mL seed + nutrients d. Add 30 mL seed + nutrients e. Add 45 mL seed + nutrients For sample (2 trials each)
a. 0.01% (0.03 mL) sample + nutrients b. 0.05% (0.15 mL) sample + nutrients c. 0.10% (0.30 mL) sample + nutrients d. 0.50% (1.50 mL) sample + nutrients e. 1.00% (3.00 mL) sample + nutrients
*Reserve 5 bottles incubate for 5 days at 20° C for DOf
After 5 days – final BOD
Repeat the above procedure for BOD.
If DO reading is high, no need of seeding, proceed to incubation and determine BOD.
The higher the DO the greater is the quality of water. Lower DO H2O is polluted,
DO is inversely proportional to BOD.
Do must be analyzed on site where the sample is collected or w/ in six hours. Must refrigerate the sample. The higher the temp. the higher the DO.
Calculation:
Depletion= DOi-DOf , %= Depletion/DOi x 100
2. Select the % depletion nearer 40-70% of seed control and sample 3. Compute fraction % dilution
Let x= % dilution of spl (selected), let y= % dilution of seed control (selected) f= 20 ml of seed added per liter of dilution
4. Compute the seed correction, SC.
Let z= depletion of seed control (selected), f= from #3 SC= zf
5. Compute for BOD, mg/L (after 5 days incubation), get also the temperature.
BOD5 (20°C)= change to decimal by dividing by 100
Ex. If % dilution of sample is 0.10% the fraction of dilution is 0.001
2. Oxygen (Demand) in Water
Titrimetric Method AOAC Official Method 973.45
Significance and Use
Dissolved oxygen is required for the survival and growth of many aquatic organisms, including fish. The concentration of dissolved oxygen may also be associated with corrosivity and photosynthetic activity. The absence of oxygen may permit anaerobic decay of organic matter and the production of toxic and undesirable esthetic materials in the water.
The Winkler titration is useful in a number of DO measurements;
2. to calibrate or verify readings obtained with a DO meter; and 3. to make a direct determination of DO on a water sample.
Apparatus and Reagents are the same with BOD
Procedure
Standardization of Sodium Thiosulfate
1. In a 500 mL wide-mouth Erlenmeyer flask place 2 g potassium iodide in 100-150 mL distilled water. Swirl to dissolve.
2. Add 2 drops of concentrated sulfuric acid and 20.0 mL of standard potassium bi-iodate solution. 3. Record the initial volume of sodium thiosulfate in the burette.
4. Titrate the potassium iodide solution with sodium thiosulfate to a straw yellow color.
5. Add several drops of starch, a blue / purple color will develop. Titrate dropwise until the blue / purple color disappears (solution will become clear).
6. Record the final volume of sodium thiosulfate in the burette. 7. Calculate the volume of sodium thiosulfate used.
Note: The amount of sodium thiosulfate used should be equal to the amount of potassium bi-iodate solution titrated (20 mL). This verifies that the sodium thiosulfate is 0.025 M (± 0.001).
Preparation of Sample
1. Fill a 300 mL BOD bottle with the sample to be analyzed. 2. With a pipette, add 1 mL of manganous sulfate.
3. With a pipette, add 1 mL of alkali-iodide-azide. 4. Stopper and invert the bottle several times to mix.
5. Allow the floc in the solution to settle to about half the volume of the bottle. 6. Invert the bottle several times to mix the floc back into the solution.
7. Allow the floc in the solution to settle to about half the volume of the bottle.
8. After settling, add 1 mL concentrated sulfuric acid, stopper and gently invert several times. Continue until the precipitate has dissolved back into solution.
9. If a brown color develops, there is dissolved oxygen in the sample. If no color develops or it is very faint, it may be appropriate to obtain another sample at this time to ensure that there has not been an error in the sample preparation.
Titration
1. Pour 200 mL of the sample to be titrated in a 500 mL wide-mouth flask. 2. Record the initial volume of sodium thiosulfate in the burette.
3. Titrate with standardized sodium thiosulfate solution to a pale yellow endpoint (swirl the flask gently while titrating or use a magnetic stirrer).
4. Add several drops of starch solution and continue titrating dropwise until the disappearance of the blue / purple coloration.
6. Calculate* the volume of sodium thiosulfate used. *Refer the calculation with BOD
3. Determination of Ash
Gravimetric Method AOAC Official Method 923.03
Ash content– the total mineral residue left (g/100g) after inceneration of organic matter at a temperature < 650oC.
Volatilization of organic salts like alkali chlorides and a portion of the ash will fuse and enclose some carbon preventing them from being ignited, the remaining is the ash.
Procedure:
Sample preparation:
a. Homogenize sample
b. Analyze immediately after, or if not analyzed immediately, keep refrigerated. 1. Heat marked crucible in furnace at specified temperature for 1 hr.
2. Lower temperature to 1800C, transfer to the dessicator and cool for 30 to 1 hr, and weigh (w1)
3. Parameters of weighing Temperature (20-25oC)
Humidity (< 60 %)
4. Weigh appropriate sample size (in duplicate) into the pre weighed crucible dish (w2) 5. For dry samples, char sample in hot plate until smoke ceases, and transfer in the furnace to
complete ashing
6. For wet or liquid sample, pre dry over boiling water bath until sample is dry and char the sample as in 5.
7. Continue inceneration at 500-600oC until residue is grayish or uniformly white
8. Decrease temperature to 1800C, transfer crucible into a dessicator cool for 30-60 min (w3).
9. Repeat 7-8 until constant weight Calculation:
Note: (if sample not completely white, moist ash with water of dilute nitric acid, evaporate in water bath and repeat heating for 30-60 min)
4. Determination of Crude Protein
Kjeldahl Method (Block Digestion) AOAC Official Method 981.10
Purpose:
This method is for the quantitative determination of crude quantitative of crude protein content of a sample.
Basic Principle:
The Kjeldahl method is the standard method of nitrogen determination dating back to its development in the late 1800's. The method consists of three basic steps:
1) digestion of the sample in sulfuric acid with a catalyst, which results in conversion of nitrogen to ammonia;
2) distillation of the ammonia into a trapping solution; and
3) quantification of the ammonia by titration with a standard solution.
• Kjeldahl flasks, 500 to 800 mL Kjeldahl digestion unit with fume removal manifold
Kjeldahl distillation apparatus - Kjeldahl flask connected to distillation trap by rubber stopper. Distillation trap is connected to condenser with low-sulfur tubing. Outlet of condenser should be less than 4 mm diameter.
• Erlenmeyer flask, 500 mL
• Analytical balance, sensitive to 0.1 mg
Reaction:
Na2SO4 + CuSO4•5H2O
Protein + H2SO4 (NH4)SO4
(NH4)SO4 + 2NaOH NH3 + Na2SO4 + 2 H2O 3NH3 + H3BO3 (NH4)3BO3
(NH4)3BO3 + 3HCl 3NHCl + H3BO3
Reagents:
1. Sulfuric acid , concentrated, 95-98%,
2. reagent grade Sodium hydroxide, pellets, flakes, or 45% solution with specific gravity 1.36 (low N) dissolve 450 g in cool water and dilute to 1 L Potassium sulfate (K2SO4),
3. anhydrous Copper sulfate (CuSO4),
4. Methyl red indicator dissolve 1 g methyl red (sodium salt) in 100 mL ethanol
5. Bromocresol green indicator, dissolve 100 mg BG to 100 ml ethanol
6. Boric acid (4%) with BG and MR indicator (dissolve 40 g Boric acid to 600 mL boiled hot water,mix and volume to 900 mL a\den add 10 ml BR and 7 m L of MR and volume ro 1L.
7. Hydrochloric acid standard solution, 0.2 N. from stock solution of 12 N HCl.
8. Sodium hydroxide standard solution Prepare 0.1 N sodium hydroxide (NaOH) solution and standardize by method. After standardizing hydrochloric acid and sodium hydroxide, check one against the other by titrating one with the other and calculating normality.
Procedure: Digestion
1. Weigh approximately 0.5-10.0 g ground sample into digestion flask, recording weight (W) to nearest 0.1 mg.
2. Add 2 pieces anhydrous copper sulfate. Then add 13-15 mL sulfuric acid. (Add additional 1.0 mL sulfuric acid for each 0.1 g fat or 0.2 g other organic matter if sample weight is greater than 1 g.)
3. Shake gently to wet sample
5. Heat until white fumes clear bulb of flask, swirl gently, and continue heating for 90 min for copper catalyst or 40 min for CuSO4 catalyst.
6. Cool, cautiously add 75 mL distilled water and cool to room temperature (less than 25oC).
Distillation
1. Clean the system ( distilling the distilled water for 3 min) 2. Order: blank, ammonium sulfate and sample
3. Dispense 50 mL 40% NaOH to the diluted digest
4. 25 mL 4% Boric acid with indicator to a receiver Erlenmeyer flask was prepared and place into the distilling unit
5. The receiver solution in the distillate flask will be green indicative of alkali ammonia
Titration
1. Titrate excess acid with standard sodium hydroxide solution to blue/grey endpoint is achievedorange record volume to nearest 0.01 mL (VNaOH). Titrate the reagent blank (B) similarly.
Calculation:
Percent Nitrogen (N)
%N (DM basis) =[(VHCl x NHCl) - (VBK x NNaOH) -(VNaOH x NNaOH)]/1.4007 X W X Lab DM/100
• Where VNaOH = mL standard NaOH needed to titrate sample • VHCl = mL standard HCl pipetted into titrating flask for sample • NNaOH = Normality of NaOH
• NHCl = Normality of HCl
• VBK = mL standard NaOH needed to titrate 1 mL standard HCl minus B
• B = mL standard NaOH needed to titrate reagent blank carried through method and
distilled into 1 mL standard HCl
• 1.4007 = milliequivalent weight of nitrogen x 100 • W = sample weight in grams
Percent Crude Protein (CP)
Factors for conversion of Nitrogen to protein
Sample F
Meat and fish 6.25
Gelatin 5.55
Milk and milk products 6.38
Casein 6.40 Human milk 6.37 Eggs: whole Vitellin Albumin 6.25 6.32 6.12 Rice and rice flour 5.95 Wheat: whole Bran Embryo Endosperm 5.83 6.31 5.80 5.70 Barley, otes, rye, flour 5.83
5. Free Fatty Acid (FFA) in Crude and Refined Oils
AOAC Official Methods 940.28
Principle:
The properties of the triglyceride and the biodiesel fuel are determined by the amounts of each fatty acid that are present in the molecules. Chain length and number of double bonds determine the physical characteristics of both fatty acids and triglycerides. Transesterification does not alter the fatty acid composition of the feedstocks and this composition plays an important role in some critical parameters of the biodiesel, as cetane number and cold flow properties
Reagents:
1. Neutralized alcohol , ethanol is added 2 mL phenolphthalein, warm and enough 0.1 M NaOh is added till faint permanent pink colution is obtained.
2. Standardized 0.25 NaOH, 4 g of NaOH to 1 L solution,
Procedure:
1. Weigh 7.05 g oil (crude oil) into 250 mL flask 2. Add 50 mL of neutralized alcohol
3. Titrate with 0.25 M NaOH,
4. Vigorously shake until permanent faint pink that last ≥ 1 min. 5. Record volume of the base
Calculation:
6. Total hardness
Titrimetric method
Principle:
The total concentration of alkaline earth metal ions, such as calcium and magnesium, in water determine the hardness of water. The term hard water comes from the fact that these metal ions precipitate soap molecules from water making it "hard" to get things clean. The calcium in hard water precipitates as calcium carbonate (lime scale), if the water is boiled. Water hardness is usually determined by measuring the total amount of calcium and magnesium present, since the concentrations of these ions far exceed those of other alkaline earth metals. The accepted
practices for reporting hardness is as mg CaCO3/L, as if all of the hardness were from calcium carbonate. Table 1 gives a classification of the hardness of water.
Table 1. Water Hardness Classification
Hardness, mg CaCO3/L Hardness Hardness
< 15 very soft 15-50 soft 50-100 mediumhard 100-200 hard > 200 very hard Reaction:
First the EDTA (H2Y2-) will complex with the calcium ions, forming a red solution:
H2In-+ Ca2+→ CaIn-+ 2H+
At the endpoint, the EDTA will complex with the calcium and the indicator becomes unbound, which isindicated by the red → blue color change:
EDTA + CaIn-+2 H+→ H2In-+CaEDTA
(red) (blue)
Procedure:
A. Solution preparation
1. Buffer solution: Dissolve 17.5 g ammonium chloride (NH4Cl) in 142 mL concentrated
ammonium hydroxide and dilute to 250 mL with distilled water.
2. Standard calcium solution: Place ~ 1.5 g anhydrous calcium carbonate (in oven) into a beaker, and place in a dessicator for 10 minutes. Weigh exactly 1.000g anhydrous
calcium carbonate into a clean 600 mL Erlenmeyer flask and add 200 mL deionized water. Add a few drops of 6 M HCl until all CaCO3has dissolved. Add 200 mL distilled
water and boil for a few minutes to expel CO2. Transfer quantitatively to a 1000 mL
volumetric flask and dilute to the mark with distilled water.
3. Dissolve 3.723 g disodium EDTA in distilled water and dilute to 1 L.
B. Standardization of the EDTA Solution
1. Before using the EDTA to titrate water samples we must know its exact concentration. We will use the solution of calcium carbonate (1.00 g CaCO3/ L) as the primary standard.
2. Measure exactly 15.0 mL of the CaCO3solution into a 250 mL flask. Add approximately 30 mL of deionized water to the flask.
3. Add 2.0 mL of the buffer solution. The remainder of the titration must be completed within 15 minutes of the time when the buffer is added.
4. Add 4 drops of Eriochrome Black T indicator solution.
5. Titrate using the EDTA titrant. At the end point the color should change from red to a pale blue.
6. Repeat this procedure at least twice.
C. Water Samples
1. Measure exactly 25.0 mL of the hard water sample into a 250 mL flask.
2. Add approximately 25 mL of deionized water to the flask.
3. Add 2.0 mL of the buffer solution. The remainder of the titration must be completed within 15 minutes of the time when the buffer is added. 3. Add 4 drops of Eriochrome Black T indicator solution.
4. Titrate using the EDTA titrant. At the end point the color should change from red to blue.
5. Repeat this procedure at least twice.
6. Use this data and the data from parts A and B to calculate the hardness of your water sample in mg CaCO3/L. Calculation: A= vol. EDTA, mL B= mg equivalent to 1 mL EDTA C= [(M,mol/L)(1000 g/mol)(1000mg/g)] 7. Calcium hardness Titrimetric method SMEWW 3800
(Standard Methods for the Examination of Water and Wastewater)
The test for calcium hardness is very similar to the total hardness test. Traditionally, either murexide indicator is used. The determination of calcium in the presence of magnesium is based on the same principle, but at a pH value of 12. In this condition, magnesium ions are precipitated as hydroxide and do not interfere with the determination of calcium. The magnesium present in the sample may be calculated by substracting the volume of EDTA solution required for the calcium determination from the volume required for the total hardness determination for equal volumes of the sample.
Reaction:
1. 1.0 N NaOH solution, 40 g NaOH dissolve in L distilled water
2. Murexide Indicator , mix 200 mg murexide and 100 mL NaCl (dry powder mixture)
Procedure:
1. Measure 100 mL water sample, 2. Add 2 mL of 1.0 N NaOH
3. Add ≈ 0.1g-0.2g MUREXIDE, mix
4. If the solution becomes light purple this indicates NO hardness, but 5. If pale pink solution is observed,
6. Titrate the solution with EDTA (0.01 M) till light purple end point. 7. Record volume of titrant
Calculation:
)(0.843)
8. Water Chlorides (Cl-)
APHA-AWWA 4500 Cl-B(SMEWW)
Principles:
In a neutral or slightly alkaline solution, potassium chromate gives a red end point in the silver nitrate titration of chloride after all the chloride is precipitated as silver chloride.
If silver ion (Ag+) is added to water which contains chloride ion (Cl-), the two combine to form
silver chloride, which is very insoluble:
Ag+ + Cl-→AgCl(ppt)
The "ppt" in parentheses after the reaction is used to indicate that the silver chloride precipitates (turns into a solid). Silver and chromate ion (CrO4-2) also combine to form silver chromate:
Ag+ + CrO
4-2→Ag2CrO4(ppt)
This compound has a higher solubility product; as long as there is chloride present, any silver chromate that forms will disappear as the silver gets taken out of solution by the silver chloride. Once the chloride is gone, the silver chromate persists. This compound is red, so it is visible in a beaker of water.
To measure chloride in a water sample, we add some potassium chromate solution, which is yellow. To the yellow sample, we slowly add silver nitrate solution (a soluble form of nitrate). A red color may appear briefly as silver chromate forms and redissolves. The silver chloride which precipitates may not be noticeable because it is white. At some point, all the chloride will have been precipitated. We can tell that this point has been reached because the red color will stay. The color change is called the endpoint, because we stop adding silver nitrate once it has been reached. A test in which we slowly add one solution to another and then stop at some
endpoint, is called a titration. The solution added, in this case silver nitrate, is called the titrant. For the number of milliliters of titrant used to be meaningful, we need to know the amount of silver in each milliliter. We get this number by titrating a chloride solution of known chloride concentration. We know the concentration of the chloride standard because we make it up by weighing a precise amount of sodium chloride and adding a measured volume of water. To get the molarity of the silver nitrate solution, we use this formula:
Molarity AgNO3 = M NaCl * mL NaCl/mL AgNO3
Note: This is C2 = C1 * V1/V2
1. Potassium chromate indicator solution: Dissolve 5 g K 2CrO4 in about 5 mL distilled
water (dH2O). Add a few drops of silver nitrate until a definite red precipitate forms. Let
stand 12 hours, filter and dilute to 100 mL with dH2O.
2. Standard sodium chloride (0.0141 M): Dissolve 824.0 mg NaCl (dried at 140°C) in dH2O
and dilute to 1000 mL. One milliliter of this solution contains how many milligrams of chloride?
3. Standard silver nitrate titrant (0.0141 M): Dissolve 2.395 g AgNO3 in dH2O and dilute to
1000 mL. Standardize against 0.0141 M NaCl. One milliliter of this solution will react with how many milligrams of chloride?
Procedure:
1. Measure 25 mL of sample with a graduated cylinder. If doing a standard, take 1.0 mL or other precise volume of standard sodium chloride solution made up to 25 mL with distilled water.
2. Sample pH must be in the range 7 to 10. 3. Add 5 drops of chromate indicator solution.
4. Titrate with silver nitrate solution until a pinkish or reddish tinge persists in the yellow solution.
5. Titrate a couple of blanks, standards, and/or samples until you can consistently recognize the endpoint. (Blanks would be just distilled water and typically require only one or two drops of titrant.)
Calculation:
To get the concentration of chloride in a sample, use the following formula:
Where:
A = mL titrant used for sample
B = mL titrant used for blank (this might be 0 mL) M = molarity of silver nitrate
DOST IX Regional Standards and Testing Laboratories also conduct the following test for chemical and physical laboratory analysis:
Test Method Reference
Acidity AOAC 930.35
Alkalinity APHA-AWWA 2320 Ash content (general) AOAC 923.03
Carbohydrate Phil. Food Composition Table (FNRI) Clean anhydrous PNS 602;1992 Annex D
Calcium determination AOAC 976.09 COD (closed reflux colorimetric method) SMEWW 5220 D Conductivity SMEWW 2510 B
Energy Phil. Food Composition Table (FNRI) Fat content (general) AOAC 989.05
Fiber AOAC 978.10
FOG SMEWW 5520D
Heating value Bomb calorimetry Iodine no.(Hanus Method) AOAC 920.158
Iodine content BFAD recommended method Moisture AOAC 925.10
IV. CONCLUSION & RECOMMENDATION
The student that has conducted its On the Job Training in DOST IX Regional Standards and Testing Laboratories has properly ended its 420 hr training in the said agency. It is believed that upon the end of its terminal report, the student have adhered the vision and mandate of the agency that governed the action of the agency for its own function and for the welfare of the mankind. The agency have provided testing center for metrological, microbiological, physical and chemical laboratory tests and analyses, and the student have conducted its training in the chemical and physical laboratory, were chemistry as its subject matter is mostly applied.
The conductance of this OJT from the start, foresee a great opportunity amongst student, not only the acquisition of knowledge of chemistry principles which are applied in each test, it also bring a good experience to be gained by the student during its training period, the student skills in the profession was enhanced and improved a thousand fold (the writer of the paper my say). Moreover the trainee had also the opportunity to assist the personnel and be part in the analyses conducted, a good start for human relation for their future workplace.
Furthermore, even the time would not allow, the students need to improve in the experiments conducted or test to practice accurate and precise results in every analysis, also greater effort to have human relation with the bosses and most especially your co-analyst.
