Gravimetric Analysis Finals

8/12/2019 Gravimetric Analysis Finals

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Finals

Gravimetric Method Assay of Sodium Lauryl Sulfate for Sodium Content

Special Method Acid Value Determination of Cooking Oil Saponification Value of Cooking Oil Assay of Phenol Content of Clove Oil Assay of Caffeine Content of Instant Coffee

Powder


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Gravimetric AnalysisAssay of Sodium Lauryl Sulfate Content

Ex 23

Compiled by Danielle Co


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Gravimetric analysis

The principle behind gravimetric analysis isthat the mass of an ion in a pure compoundcan be determined and then used to find themass percent of the same ion in a knownquantity of an impure compound

quantitative methods that are based ondetermining the mass of a pure compound towhich the analyte is chemically related


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Classifications of Gravimetric methods

, the analyte isseparated from a solution of the sample as aprecipitate and is converted to a compoundof known composition that can be weighed


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, the analyte isseparated from other constituents of asample by conversion to a gas of known

chemical composition. The weight of this gasthen serves as a measure of the analyteconcentration.

, the analyte isseparated by deposition on an electrode byan electrical current. The mass of thisproduct then provides a measure of the

analyte concentration.

Classifications of Gravimetric methods


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Traditional Method.Cheap, easily available apparatus, simple tocarry out.Slow, especially when accurate results arerequired.

Wide range of sample concentrations (ng - kg).No calibration required (except for thebalance).

Accurate


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the analyte is converted to a sparingly solubleprecipitate. This precipitate is then filtered,washed free of impurities, converted to aproduct of known composition by suitableheat treatment, and weighed


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1. Preparation of the solution2. Digestion3. Precipitation4. Digestion5. Filtration6. Washing7. Drying or igniting8. Weighing9. Calculation


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Properties of Precipitating Agent:

Should react specifically or selectively withthe analyte

Specific precipitating agentrare, react only with a single chemical species

Selective precipitating agentmore common, react with a limited number ofspecies


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Properties of Good Precipitate:

Easily filtered and washed free ofcontaminants.Of sufficiently low solubility that no significantloss of the analyte occurs during filtration andwashing.Unreactive with constituents of the

atmosphereOf known chemical composition after it isdried or, if necessary, ignited.


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Use in making shampoos, toothpastes,mouthwashes, bodywash, soaps, detergentsand body washSide effects: Hair loss, skin & eye irritation,cancer


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Na2SO4 + BaCl22H2O BaSO4 + 2 NaCl+ 2 H2O


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Wt of ppt obtained the one that we obtained after

drying inside the ovenMW of anlayte MW of the chemical that is soughtMW of ppt MW of the chemical being dried &weighed


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Ex 24

Determining the degradation of oil products


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Acid Value/Acid Number/Acidity Index

the weight of KOH in mg needed to neutralizethe organic acids present in 1g of fat and it is ameasure of the free fatty acids (FFA) presentin the fat or oil

0.5 N , 0.1 N , 0.02 Nalkali

Oil sample and

phenolphthalein


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1. Determines the age of the oil (Rancidity)Presence of free fatty acids

An increment in the amount of FFA in a sample of

oil or fat indicates hydrolysis of triglycerides Chemical treatment Catalytic action of light & heat (High temperature and

relative humidity during storage)


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Usually the causes are enzymes (lipases)and microorganisms (lipases-producing,like Candida albicans ). Lipases are enzymes,which break down fats into monoglycerides(digest fats).

For Saturated Fatty Acids (butter, coconut)Rancidity gives off flavorful smell (tastysmell)


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Rancidity

- oxygen damages foodsOxygen molecules interact with the structure ofthe oil and damage its natural structure in a way

that can change its odor, its taste, and its safetyfor consumptionFor Mono & Polyunsaturated Fatty acids

off-flavors and odors due to the formation ofperoxides, carbonyls, aldehydes, trienes


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2. Determination of Adulterants3. Used to monitor the quality of the oil and

prevent problems caused by degradation.


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If stored in light, clear bottles, in tins with alarge air bubble at the top, at higher storagetemperature or at direct sunlight

During cooking, especially if it is highlyunsaturated. The higher the temperature (likein frying), the faster it oxidizesDuring storage, if attacked by lipase-producingbacteria and microorganismsIf passed trough machines or vessels, made ofor containing iron


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Is rancid oil bad for your health?

I experience a BleedingLiver , Necrotic liver

My kidney is damagedand I over eat!


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store cooking oils in dark or covered/wrappedbottles away from direct sunlight, or in metal tinswith the oil nearing the top of the tinstore cooking oils in cool and dark places bestrefrigerated (keep in mind that highlymonounsaturated oils, like olive oil will becomesemi-solid at low temperatures)use lower cooking temperatures (with the right

cooking oils below) and DO NOT reuse oils forcooking or frying!in commercial applications, with the use of natural(polyphenols, ascorbic acid, mixed tocopherols) or

synthetic antioxidants, added to oils


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What oils should you use for cooking? The best oils for cooking are those that are highly

saturated or primarily monounsaturated in thisorder:

coconut oil (warning: low smoke point use lowercooking temperatures)

butter, organic (or ghee clarified butter) palm oil lard extra-light olive oil pomace oil extra-virgin olive oil (lower smoke point)


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Formula for Acid value

mgKOH/meqKOH is 56.11


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Saponification

a process that produces soap, usually fromfats and lye

involves base (usually sodiumhydroxide commonly called causticsoda NaOH) hydrolysis of triglycerides, whichare esters of fatty acids, to form the

sodium salt of a carboxylate


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the number of milligramsof potassium hydroxide requiredto saponify 1g of fat under theconditions specified

Saponification Value

Saponification Number

Koettsdorfer Number

Sap Value


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Saponification Value interpretation

Lesssoapiness

Moresoapiness


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Good soap Substance present inoils or fat that are notsaponified by alkalihydroxides but aresoluble in ordinary fatsolvents

Fail to form soap

SaponifableMatters

UnsaponifiableMatters


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Saponification equation

Gravimetric Analysis Finals

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