analytical chem exam 1

population

large material system that is to be studied

sample

small representative portion of population

sample =

matrix + target analyte

matrix

removal of analyte from sample

chemistry

scientific study of the properties, composition,& structure of matter, the changes in structure & composition of matter, and accompanying energy changes

thales

believed matter was made of water; predicted the solar eclipse of 585 B.C.

aristotle

believed matter was made of water, earth, air , fire and the 4 qualities (hot,cold,wet,dry)

empedocles

believed matter was made of water, earth, air, and fire

democritus

believed matter was made of atoms

dalton

believed different atoms had different relative weights

bohr

believed in a positively charged nucleus and orbiting negatively charged electrons

gell-mann and zweig

believed matter was made of quarks

quarks

subatomic particles that make up protons and neutrons

protons have 3 quarks,

2 up and 1 down

neutrons have 3 quarks:

1 up and 2 down

one up quark is worth

2/3 of a positive charge

one down quark is worth

-1/3 of a positive charge

protons stay in the nucleus due to

a strong force of electromagnetic repulsion

protons are held together by a strong nuclear force via

the exchange of photons

quarks are held together by strong forces via

the exchange of gluons

mass is an attribute of matter once it interacts with

the Higgs field

what was the purpose of van helmont’s tree experiment

he wanted to confirm Thale’s matter theory

analytical chemistry

a scientific discipline that develops and applies methods, instruments, and strategies to obtain information on the composition and nature of matter in space and time

miniaturization

making instruments smaller to make (in field) analysis a simpler process

lower detection limits

allows detection for as small of a sample concentration as possible

the larger the deviation from the base line

the larger the response

signal

response to the prescience of an analyte

limit of detection

signal / noise = 3; signal observed due to target analyte

limit of quantitation

signal/noise = 10

trends of analytical chemistry

• miniaturization

• lower detection limits

• instrumental approach

• higher speed

• higher sensitivity

• automation

• integration of disciplines

sensitivity

detector signal per unit concentration of the analyte; tan a = AB/OB

standard solutions

have the ideal range of analyte concentrations

different analytes give

different responses of unit concentration

pillars of analytical chem

• chromatography

• mass spec

• spectroscopy

• spectrophotometry

• electroanalytical chem

• chemometrics

chemometrics

application of statistical and mathematical methods of chemical analysis

steps of chemical analysis

• formulating the problem

• literature search for analytical procedures

• sampling

• sample prep

• analysis

  • separation

  • section

  • quantitation

• reporting and interpretation

• drawing conclusions and refs

easiest way to get a sample from a heterogeneous population

make it homogenous

theophyline

theobromine’s isomer

what do caffeine and theobromine have in common

they are structurally similar

stationary phase of HPLC

special material that contains silica particle for support of organic ligands

mobile phase of HPLC

pushing sample through column via liquid

as a sample go through the column

it separates into individual components

same amount of chromatographic zones

as components in the sample

photodiode array detector

detects all UV absorbing analytes at the same time

1799

metric system introduced in france

1960

international system of units is published (SI)

what are the 7 base units

second, meter, kg, ampere, mole, Kelvin, and candela

second in the base unit for

time

meter in the base unit for

length

kg is the base unit for

mass/quantity

amphere is the base unit for

current

mole is the base unit for

amount of a substance

Kelvin is the base unit for

temperature

candela is the base unit for

luminosity

how many other named units are there

22

how are base units determined

by being assigned to a particular constant of nature at a fixed value

a second is associated with the

Cs-133 hyper fine transition frequency

a meter is associated with the

speed of ight in vacuum

a kg is associated with the

planck’s constant

an amphere is associated with the

elementary charge

a kelvin is associated with the

botzmann constant

a mole is associated with the

avogadro’s number

a candela is associated with the

luminous efficacy

molar mass

number of grams of a substance that contains avogadro’s number of molecules ; g/mol

solution

homogeneous mixture of molecules of two or more substances

solute

minor component(s) of a solution

solvent

major component of a solution

solution concentration

quantitative expression fo the solute contains in unit volume or unit mass of the solution or solvent

weight percentage

(solute/solution) x 100%

volumetric percentage

(solute/solution) x 100%

molarity (M)

# of mols of solute/ volume of solution (L)

# of mols of solute

mass (g) x volume (L)

as volume and temperature increases,

molarity decreases

dilution ratio

Mconc x Vconc = Mdil x Vdil

# of mols

mass (g)/ molar mass (g/mol)

molality (m)

# of mols of solute/ mass of solvent (kg)

# of mols of solute using molality

molality x mass of solvent (kg)

aqueous solution

water is the solvent

mass of a solution

density x volume

mass of solute in a solution

# of mols x molar mass

parts per million

weight of solute/ weight of solution x 10^6

parts per billion

weight of solute/ weight of solution x 10^9

parts per trillion

weight of solute/ weight of solution x 10^12

grams to micrograms

# of grams x 10^6

weight of solute using ppm

1. assume weight of solution is 1 L, so 1000g

2. multiply ppm times 1000 and divide that by 10^6

3. to find number of mols divide that number by the molar mass

4. number of mols/ 1 L= molarity

finding number of mols using wt %

(wt %) x (densityxV)

equilibrium

ststaee of balance between 2 opposing forces