qc 1 review
TRANSCRIPT
*Analytical Chemistry* Aka. Pharmaceutical Analysis* Branch of chemistry which provides information relative to the composition of matter.
*2 Divisions of Analytical Chemistry1. Qualitative
oAnswer the question:•What is present in a given sample?
oDetermine the composition of the sample.
2. QuantitativeoAnswer the question:•How much is present in the sample?
oDetermine the proportion of components in a given sample?
*Classification of Analysis
1.Based on the sample size2.Based on the extent of
determination3.Based on nature of method4.Based on materials used
* I. Based on the sample
1.Ultra-micro : <1 mg2.Micro : 1 mg – 10 mg3.Semi-micro : 10 mg – 100
mg4.Macro : 100 mg – 1 g
* II. Based on the extent of determination
1.Proximate – total amount of class / group of active principles in a given sample.
2.Ultimate – amount of a specific compartment / single chemical species present in the sample.
* III. Based on nature of method1. Classical
oAka. General or ChemicaloEg. Titrimetric, Gravimetric
2. InstrumentationoUsed for more accurate analysisoEg. Spectrophotometer, Polarimeter
3. Miscellaneous / Specific method oInvolves crude drugs and natural products derived from themoEg. Water content determination, Ash content, Acid value
*IV. Based on materials used
1.ChemicaloUse of chemical reagents
2.PhysicaloUse of instruments & special apparatus
3.BiologicaloUse of microorganisms or animals
*Basic Principles
1.pH
2.Buffer Capacity
*I. pH
1. Negative logarithm of molar concentration of Hydrogen ion;.
2. pH = -log[H+] or pH = log 3. Henderson-Hasselbalch
equationopH = pka + log oropH = pka + log • pKa – acid dissociation constant
*I. pHSample problem:1. Calculate the pH of solution that contains
3.7 x 10 -2 moles of Hac and 4.8 x 10 -2 moles of NaAc in a liter of solution pKa = 9.26.
2. What is the ratio of the salt & acid conc. if the solution has a pH of 4.5 and pKa of 4.76?
Answers: 1.) pH=9.37; 2.) 0.58
*I. pH4. Properties:oProtolysis – a process whereby a proton
is transferred from one molecule to another.oAutoprotolysis – a process whereby
there is a transfer of a proton from one molecule to another identical molecule.oAmphoteric – property where a
substance can act as either as acid or base.
*II. Buffer Capacity
1. Ability of buffer solution to resist change in pH upon addition to acid/alkali.
2. BC equation = 3. Van slyke:
Amount in g/L of strong acid or a strong base required to be added to a solution to change it’s pH by 1 unit.
*Methods used for Official Assay
1.Titrimetry**2.Gravimetric **3. Spectrometric method4. Electrometric method5. Chromatographic method6. Miscellaneous method
*Assay
An investigative (analytic) procedure in laboratory medicine, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence or amount or the functional activity of a target entity (the analyte).
*I. Titrimetry**
1. Aka. Volumetric AnalysisoA process of determining volume of standard solution (of known concentration) required to react with a known amount of substance being assayed.
*I. Titrimetry**2. Definition of terms:o Analyte – aka. sample, active constituent, titrando Standard solution – aka. volumetric solution,
titrant o Indicator – chemicals capable of changing color at
or near end point in w/c equivalent quantities of analyte & std solution have reacted.
o Equivalent point – aka. Theoretical pt. or Stoichiometric pt. is a point where the added substance is chemically equivalent to the analyte or sample.
o End point – experimental approximate of the Eq.Pt. which could be observable.
*I. Titrimetry**3.Apparatus used:
a.Burets:oMohr’s / baseoGeissler’s / acid
b.Cleaning solutions:oNa2Cr2O7 in H2SO4
o(NH4)2S2O8 in H2SO4
oNa3PO4
oSynthetic detergents
*I. Titrimetry**4. Indicators
INDICATOR pH range
ACID BASE
Malachite green
0.0-2.0 Yellow Green
Methyl orange 3.2-4.4 Red-Orange
Yellow
Methyl Red 4.2-6.2 Red YellowBromthymol blue
6.0-7.6 Yellow Blue
Phenolphthalein
8-10 Colorless Red
Thymol blue 8-9.2 Yellow Blue
*I. Titrimetry**5. Types of titration:
a) Based on # of volumetric solutionoDirect titrationoIndirect / Residual titration
b) Based on chemical reactionoNeutralizationoRedOxoReactions involving Combinations of Ions
*A. Based on # of volumetric solution1.Direct titration
* 1 std. sol’n + Analyte%P = x 100
2.Indirect / Residual titration* 2 std. solution + Analyte* Involves addition of excess std.
solution (primary std) & the excess is back titrated w/ another std. solution (secondary std).
*Indirect titration* Used when:
1. Sample is insoluble or forms a ppt.2. Sample is volatile3. Slow reaction4. Reaction does not have sharp end point
*End point1. Visual end point - use of indicators2. Electrometric end point – use of
instruments in ampherometry, conductivity or HF titration
*Indirect titration* Formula• %P = x100
*Blank Determination* Performing the entire titration
process without the analyte- Rationale: 1. to enhance end point reliability
2. to account for correction* Formula• %P = x 100
*Sample problem* A 0.3 g sample of Sod. bicarbonate
(MW=84 g/mol) requires 4 mL of 0.9 N HCL. What is its % purity?
* If sample magnesia magma weighing 5 g when dissolved in 25 mL 1 N H2SO4 required 10 mL of 1 N NaOH to titrate the excess acid, what is the % purity of magnesia magma? (Mg = 24; O = 16; H=1)
*B. Based on chemical reaction1.Neutralization
* Acid-base reaction* Alkalimetry & Acidimetry
2.RedOx* Chemical reaction involves a change in the
balance number of reacting substance3.Reactions involving Combinations of Ions* Volumetric precipitation* Complexation / Chelometry reaction
*I. NeutralizationA.Acidimetry1.Direct• Sample: NaHCO3, Na2CO3, NaOH• Vs: HCl, H2SO4
2. Indirect • Sample: ZnO, Methenamine• 1* std: HCl, H2SO4• 2* std: NaOH
*I. NeutralizationB.Alkalimetry1.Direct• Sample: H3PO4, H3BO3, HCl• Vs: NaOH
2. Indirect • Sample: Aspirin• 1* std: NaOH• 2* std: K biphthalate
*II. Reduction-oxidation
1.Permanganometry2.Iodimeetry3.Iodometry4.Cerimetry
*II. Reduction-oxidation1.Permanganometry* Direct• Sample: H2O2• Vs: KMnO4* Indirect • Sample: Malic Acid, TiO2• 1* std: KMnO4• 2* std: Na2C2O4
*II. Reduction-oxidation2. Iodimetry* Assay of reducing agents* Involves iodine* Direct• Sample: Ascorbic acid; Tartar
emetic• Vs: I2
* Indirect • Sample: Calomel, antipyrine• 1* std: I2
• 2* std: As2O3
*II. Reduction-oxidation3. Iodometry* Assay of oxidizing agents* Involves iodide* Direct• Sample: CuSO4, NaOCl• Vs: Na2S2O3
* Indirect • Sample: Phenol, Resorcinol, PbO• 1* std: Na2S2O3• 2* std: K2Cr2O7
*II. Reduction-oxidation
Indicators:1. Starch TS:* Iodimetry : colorless* Iodometry : blue
2. Chloroform, CCl4
*II. Reduction-oxidation
4.Cerimetry• Sample: Vit. K (Menadione);
FeSO4• Vs: Ce(SO4)2• Indicator: Orthophenantroline TS
(Red to Blue)
*III. Reaction involving combination of ions1. Volumetric precipitation
a) Volhard - Formation of insoluble colored complex. Ex. Aminophlline
b)Mohr – Formation of 2nd precipitate. Ex. SLS
c) Gay-Lussac – Cessation of precipitation. Ex. NaCl
d)Liebig – Appearance of turbidity Ex. Organic Nitrogen compounds
e) Fajans – Change in color of precipitate Ex. Pheyleprine HCl; Tubocurarine HCl
*III. Reaction involving combination of ions2. Complexation / Chelometry reaction
* Sample: CaCO3, ZnO, Mg (direct)Bi & Al cmpds (residual)
VS: EDTA – ethelynediaminetetraacetic acidIndicator: hydronaphtol blue* Masking – metal detection in presence of
another metal.Masking agent Element masked
Triethanolamine Al, Fe, MnThioglycol Hg, Cu, BiCyanide Zn, Co, Ni, CuFluoride Ca, Mg, Al
II.Gravimetry**
1. Analysis where in constituents of a sample are separated & the product is weighed
2. Determining the weight of the substance in a sample from the weight of chemically equivalent amount of some other substances
3. Examples: MgO in Mg citrate sol’n.;Na2SO4 in SLS
II.Gravimetry**
Formula:%P = x 100 or;%P =
II.Gravimetry**
Sample Problem:If a 0.5 g sample KI yielded 0.8 g
of AgI ppt by gravimetric assay. What would be the % purity of KI? (MW of KI = 166 g/mol; MW of AgI = 235 g/mol)
