QC1 LEC PRE FI: Precipitation Method

Precipitate

Occur when cations and anions in aqueous solution combine to form an insoluble ionic solid called a _______

Precipitation Method

Require the formation of relatively insoluble substances or precipitates

• Cessation of Precipitation

• Turbidity

Determination of Endpoint can be done in:

1. _____ or the appearance of a _____

Internal Indicators

Determination of Endpoint can be done in:

2. Use of _____

Potentiometric/Amperometric

Determination of Endpoint can be done in:

3. Instrumental Methods: ____/____

• Ferric Ammonium Sulfate

• Potassium Chromate

• Adsorption Indicators

Indicators

• Dichlororfluorescein (DCF)

• Eosin Y TS

• Tetrabromophenolphthalein Ethyl Ester (TEE) TS

Adsorption Indicators

Ferric Ammonium Sulfate

What indicator has the usage of Direct and Residual Titrations with Standard Ammonium Thiocyanate Solution

Ferric Ammonium Sulfate

What indicator is being described:

• 8g of NH₄Fe(SO₄)₂·12H₂O (Ammonium Iron Sulfate Dodecahydrate) in sufficient water to make 100mL

100mL

In Ferric Ammonium Sulfate,

• 8g of NH₄Fe(SO₄)₂·12H₂O (Ammonium Iron Sulfate Dodecahydrate) in sufficient water to make _____

Ammonium Iron Sulfate Dodecahydrate

NH₄Fe(SO₄)₂·12H₂O

White

In Ferric Ammonium Sulfate,

• Thiocyanate reacts with Hg/Ag to produce a ____ ppt

Red

In Ferric Ammonium Sulfate,

• Once all Hg/Ag have precipitated, thiocyanate ions react with indicator, it forms ____ (endpoint) Ferric Thiocyanate

Potassium Chromate

What indicator is being described:

• 10g of K₂CrO₄ in sufficient water to make 100mL solution

White

In Potassium Chromate,

• Forms ____ ppt with AgCl at start of reaction

Red

In Potassium Chromate,

• Forms ___ ppt of Ag Chromate - marks endpoint

AgCl

Potassium Chromate has coprecipitation with ___

Adsorption Indicators

Are weak organic acids that vary in strength

Dichlororfluorescein (DCF) TS

What Adsorption Indicator is being described:

• 100mg of DCF in 60mL ROH → add 2.5mL of 0.1N NaOH → mix and dilute with water to 100mL

Eosin Y TS

What Adsorption Indicator is being described:

• 500mg of Eosin Y in 100mL of water

Tetrabromophenolphthalein Ethyl Ester (TEE) TS

What Adsorption Indicator is being described:

• 100mg of TEE in 90mL of glacial HAc and dilute with glacial HAc to 100mL

Fresh Solution

Tetrabromophenolphthalein Ethyl Ester (TEE) TS is prepared as ____

Endpoint

_____ is indicated by Abrupt change of color of the silver halide ppt due to absorbed indicator anions

Diffuse-light condition 

Endpoint is best seen at _____

• 0.1N Silver Nitrate (AgNO₃)

• 0.1N Ammonium Thiocyanate (NH₄SCN)

Standard Solutions

slow

In 0.1N Silver Nitrate,

• Diluted HCL is a ___ precipitant

Hydrochloric Acid

In 0.1N Silver Nitrate,

• This aids in the precipitation with large particles of silver

Purple

In 0.1N Silver Nitrate,

• Free silver is produced _____ when exposed to light

0.1N Ammonium Thiocyanate (NH₄SCN)

In preparation & standardization,

• A secondary standard; Deliquescent

0.1N Silver Nitrate (30mL) + HNO₃ (2mL)

Analyte of 0.1Ammonium Thiocyanate

Ferric Ammonium Sulfate (2mL)

Indicator of 0.1N Ammonium Thiocyanate

Permanent Reddish-Brown

Endpoint of 0.1N Ammonium Thiocyanate

Nitric Acid (HNO₃)

In Ammonium Thiocyanate

• This prevents hydrolysis of FeNH₄(SCN)₂

Calculation for Normality

Direct Titration

Direct Titration/Residual Titration:

• Used for compounds that are readily convertible into soluble salts

Silver & Mercury

Example of Direct Titration

Ammonium Thiocyanate Solution (NH₄SCN

Titrant in Direct Titration

Ferric Ammonium Sulfate

Indicator in Direct Titration

Red ppt of Ferric Thiocyanate

Endpoint in Direct Titration

Direct Titration

acidified

In Direct Titration,

• Solution must be ___ with HNO₃

In direct titration, acidifying HNO₃ prevents ____ of ferric salts in neutral solution

Chlorides

In direct titration, ___ must be absent

Since chlorides of silver and mercury are more soluble than the respective thiocyanates

In direct titration, why is chlorides must be absent?

Assay of Phenylmercuric Nitrate

In direct titration, what assay is being described:

• Used for mercury content determination

0.1N Ammonium Thiocyanate

Titrant of Phenylmercuric Nitrate

Ferric Ammonium Sulfate

Indicaror of Phenylmercuric Nitrate

62.75% - 63.50% Hg

NF requirement of Phenylmercuric Nitrate

Assay of Phenylmercuric Nitrate

In direct titration, what assay is being described:

• Antiseptic and Antifungal agent; Preservative in Pharmaceutical 0.0025%

Sodium Lauryl Sulfate

A cleaning agent

Na Dodecyl Sulfate

Assay of Sodium Lauryl Sulfate, AKA?

0.1N Silver Nitrate

Titrant of Assay of Sodium Lauryl Sulfate

Potassium Chromate

Indicator of Assay of Sodium Lauryl Sulfate

Assay of Sodium Lauryl Sulfate

In direct titration, this has coprecipitation of Ag Chromate and Ag Chloride

Assay of Iopanoic Acid Tablets

3-amino-α-ethyl-2,4,6-triiodobenzenepropanoic acid

Assay of Iopanoic Acid Tablets

In direct titration,

• This assay is used for iodine ion determination

0.05N Silver Nitrate

Titrant of Assay of Iopanoic Acid Tablets

Glacial HAc + TEE TS

Indicator of Assay of Iopanoic Acid Tablets

Yellow ppt changes to green

Endpoint of Assay of Iopanoic Acid Tablets

0.1N Silver Nitrate

Titrant of Benzyltrimethylammonium Chloride

Dichlorofluorescein

Indicator of Benzyltrimethylammonium Chloride

• Volhard Method

• NaCl Purity Determination

• Assay of NaCl

• Assay for Iodide content of Povidone-Iodine (Betadine)

• Assay of Theophylline

Residual Titration

Jacob Volhard

Who discovered the Volhard Method

Volhard Method

NaCl Purity determination can also be determined by ___

Absent

Sodium Chloride Purity Determination can be determined by Volhard Method provided by, substances which give precipitates with silver nitrate are ____

0.1N Silver Nitrate

Titrant 1 of Assay of NaCl (added in excess)

0.1N Ammonium Thiocyanate

Titrant 2 of Assay of NaCl

Ferric Ammonium Sulfate

Indicator of Assay of NaCl

Nitric Acid

In residual titration, assay of NaCl

• This Acid is added to prevent ppt of silver with other halides

In residual titration, assay of NaCl

• This is added to form a film over precipitated AgCl particles

100.5%

In residual titration, assay of NaCl has a USP req of ____

%Purity of NaCl Formula

Betadine

Assay for Iodide Content of Povidone-Iodine or ___

Assay for Iodide Content of Povidone-Iodine (Betadine)

In residual titration, what assay is described:

• Reaction must produce reduced iodine ion

0.1N Silver Nitrate

Titrant 1 of Assay for Iodide Content of Povidone-Iodine (Betadine)

Ferric Ammonium Sulfate

Indicator for Assay for Iodide Content of Povidone-Iodine (Betadine)

0.1N Ammonium Thiocyanate

Titrant 2 Assay for Iodide Content of Povidone-Iodine (Betadine)

Sodium Bisulfite T. S

In residual titration, Assay for Iodide Content of Povidone-Iodine (Betadine)

• This makes iodine colorless (reduced iodine)

Nitric Acid

In residual titration, Assay for Iodide Content of Povidone-Iodine (Betadine)

• Prevent hydrolysis of ferric alum and ppt of silver as carbonate, phosphate, etc.

6.6%

In residual titration, what is the USP requirement of Assay for Iodide Content of Povidone-Iodine (Betadine)

8-chlorotheophylline

Assay Of Theophylline or AKA ___

Aminophylline

Assay Of Theophylline, Official Prep ____

 0.1N Silver Nitrate

Titrant 1 of Assay of Theophylline

Ferric Ammonium Sulfate

Indicator of Assay of Theophylline

0.1N Ammonium Thiocyanate

Titrant 2 of Assay Of Theophylline

Nitric Acid

In Assay of Theophylline, what is used to acidify silver nitrate

Sodium Tetraphenylboron Titration

Used as titrant to quantitatively precipitate such organic nitrogen compounds as alkaloids, amine, and quaternary salts, as well as ammonium, potassium, and silver ions. 

Chloroform

Extratcion Indicator of Sodium Tetraphenylboron Titration

Bromophenol Blue

In Sodium Tetraphenylboron Titration

• Quaternary Compounds + Anionic Dye, such as ___

Insoluble Compound

In Sodium Tetraphenylboron Titration

• Colored Complex + Titrant Na(C₆H₅)₄B =____

colorless

Endpoint of Sodium Tetraphenylboron Titration

• Determined when the chloroform layer becomes _____ due to the liberation of nitrogen from dye complex to precipitate with the tetraphenylboron

Sodium Tetraphenylboron Titration

• Offers advantages than tedious residual methods 

• Its uses alkaloidal precipitants such as Potassium ferric cyanide and K₂CrO₄ (alkaloidal ppts)

• Benzethonium Chloride

• Cetylpyridinium Chloride

In Sodium Tetraphenylboron Titration, drugs that undergo this reaction)