INTRO TO ANACHEM AND MEASUREMENTS Flashcards
Is a branch of chemistry involved with the analysis of
chemical substances
; Characterization of matter
ANALYSIS
ANALYTICAL CHEMISTRY
In Analysis
‘Ana’ meaning ___ and
‘lyein’ meaning _______
up; loosen
Defined as the identification and determination of
the relative amounts of one or more components in a
mixture
ANALYSIS
two major areas of analytical chemistry
Qualitative Analysis and Quantitative Analysis
identification of
substances of interest
* Answers the question, “What is in the
sample?
QUALITATIVE ANALYSIS
determination of
concentration or amount of substances present in a
given sample
* Answers the question, “How much is in the
sample?”
QUANTITATIVE ANALYSIS
ANALYTICAL METHODS:
CLASSICAL (CHEMICAL OR WET); MODERN (INSTRUMENTAL)
Methods in which basic types of equipment are used
based on simple chemical analysis
CLASSICAL (CHEMICAL OR WET)
2 METHODS OF CLASSICAL METHOD
Gravimetric Method and Volumetric Method
determine the mass of
the analyte or some compound chemically related
to it
Gravimetric Method
measure the volume of a
a solution containing sufficient reagent to react
completely with the analyte
Volumetric Method
3 Methods of Modern Analytical Method
Electroanalytical Method, Spectroscopic Method, Miscellaneous Method
measurement of
electrical properties (voltage, current, resistance,
quantity of electrical charge)
Electroanalytical Method
based on the
measurement of the interaction between
electromagnetic radiation and analyte atoms or
molecules, or the production of such radiation by
analytes
Spectroscopic Methods
measurement of such
quantities as:
▪ mass-to-charge ratio
▪ rate of radioactive decay
▪ heat of reaction
▪ rate of reaction
▪ sample thermal conductivity
▪ optical activity
▪ refractive index
Miscellaneous Methods
In two types of Analytical Method (Classical and Modern) which is more efficient?
Modern (Instrumental)
State if this method is classical/instrumental and the example it has:
Titrimetric
Classical
Example: Acid/Base, Redox, Precipitation Titrations
State if this method is classical/instrumental and the example it has:
Gravimetric
Classical
Example: Analysis of inorganic ions (constant mass)
State if this method is classical/instrumental and the example it has:
Separation
Classical; Example: TLC, PC, CC, IEC
Instrumental; Example: GLC, HPLC
State if this method is classical/instrumental and the example it has:
Electrochemical
Classical; Example: Potentiometric, conductimetric titrations
Instrumental; Example: Polarography, ion selective electrodes
State if this method is classical/instrumental and the example it has:
Spectroscopy Absorption and Spectroscopy Emission
Instrumental
Example: UV, IR, NMR, ESR, AAS, Flame Photometry, AES, MS
State if this method is classical/instrumental and the example it has:
Nuclear/X-ray
Instrumental
Example: MS (isotopes), X-ray fluorescence, NA
State if this method is classical/instrumental and the example it has:
Thermal
Instrumental
Example: DTA, TGA, DSC
State if this method is classical/instrumental and the example it has:
Combination Techniques
Instrumental
Example: GS/MS, GC/IR, HPLC, MS
What are the modern (instrumental) equipments?
AAS (spectrometer)
UV-Vis Spectrophotometer
NMR (Nuclear Magnetic Resonance Spectroscopy)
HPLC (High-Performance Liquid Chromatography)
True or False: A classical method accounts for about 10% of all
the current analytical work.
True
A classical method is ________ sensitive (up to
microgram units)
less
Determines one
analyte at a time
Classical
Accounts for 90% of the
current analytical work
INSTRUMENTAL
Instrumental Method is_________ sensitive
Very
May determine
several samples
compounds (multi-analyzer, even>10)
Instrumental Method
In Classical Method, it has small concentration
range of ____orders of
magnitude (i.e.
powers of 10)
2-3
In Instrumental Method is has more than ___________
of magnitude (i.e.
power of 10)
6 orders
It is quicker and
cheaper for large
samples
Instrumental
Instrumental Method is more efficient thus, have ________________handling and are more__________.
automatic data; reliable
The structured steps in chemical analysis
Involves sample preparation, separation, and
measurement
Analytical Process
What are the things involved in Analytical Process
- Sample Preparation
- Measurement
- Signal belonging, - guarantee, - selection, -parameter
- Calibration
- Chemometrics
- Data evaluation and interpretation
- Chemometric Data Analysis
Steps of the Analytical Process
- Problem Definition
- METHOD SELECTION
- SAMPLING
- SAMPLE PREPARATION
- ANALYSIS (Separation)
- CALCULATION AND REPORTING (Measurement)
– identify the problem and
formulate questions
* What is the problem? What needs to be found?
Qualitative and/or quantitative?
* What will the information be used for? Who will use
it?
* When will it be needed?
* How accurate and precise does it have to be?
* What is the budget?
PROBLEM DEFINITION
select method of analysis
FACTORS
* Sample type, size of sample, sample
preparation
* Concentration and range (sensitivity needed)
* Selectivity needed (interferences)
* Accuracy/precision needed
* Tools/instruments available
* Expertise/experience
* Cost
* Speed
* Does it need to be automated?
* Are methods available in chemical literature?
* Are standard methods available?
METHOD SELECTION
– obtain bulk sample and extract smaller
laboratory sample from bulk
Process of collecting a small mass of a material
whose composition accurately represents the bulk
of the material being sampled
FACTORS
* Sample type/homogeneity/size
* Size: macro, semi-macro, micro, ultra
* Type: major, minor, trace, ultra
* Sampling statistics/errors
SAMPLING
prepare sample for
analysis
FACTORS
* Solid, liquid, or gas?
* Dissolve?
* Ash of digest?
* Chemical separation or masking of
interferences needed?
* Need to concentrate analyte?
* Need to change (derivatize) the analyte for
detection?
* Need to adjust solution conditions (pH, add
reagents)?
SAMPLE PREPARATION
analytical measurement of
the analyte in question
Perform any necessary chemical separations:
* Distillation
* Precipitation
* Solvent extraction
* Solid phase extraction
* Chromatography (may be done as part of the
measurement step)
* Electrophoresis (may be done as part of the
measurement step)
Perform the Measurement:
* Calibration
* Validation/controls/blanks
* Replicates
ANALYSIS (Separation)
– calculate results, interpret/present data and draw
conclusion. Give recommendation.
* Statistical analysis (reliability)
* Report results with limitations/accuracy
information
CALCULATION AND REPORTING (Measurement)
Samples of about the same size that are
carried through an analysis in exactly the same way
REPLICATES
To improve the reliability and to obtain information
about the variability of results, two to five portions,
AKA replicates of a sample are carried through an
entire analytical procedure.
REPLICATES
Individual results from a set of measurements are
seldom the same, so we usually consider the “best”
estimate to be the central value for the set.
REPLICATES
To determine the central value, we can either use the
MEAN or the MEDIAN
MEASURES OF CENTRAL VALUE OR TENDENCY
the sum of numbers (replicate
measurements) divided by number of measurements
in the set; Similar to average
MEAN
the middle value in a set of that has been
arranged in numerical (increasing or decreasing)
order
MEDIAN
Used when a set of data contains an outlier
MEDIAN
a result that differs significantly / far away
from others in the set. It can have a
significant effect on the MEAN of the set but
has NO effect on the MEDIAN.
outlier
The _______ will not discriminate the outlier
median
Construct the formula of the Mean with these given values:
65.5
66.7
68.8
69.1
69.2
70.0
(65. 5 + 66. 7 + 68. 8 + 69. 1 + 69. 2 + 70. 0)/6 = Mean
Construct the formula of the Median with these given values:
65.5
66.7
68.8
69.1
69.2
70.0
(68. 8 + 69. 1)/2=Median
ANALYTICAL MEASUREMENTS(A & P):
ACCURACY & PRECISION
describes the nearness of an
experimental value or a mean to the true value.
Although the true value can never be exactly known,
accepted value is often used.
ACCURACY
statistically measured
through absolute or relative error
Accepted value
refers to the agreement between
values in a set of data (closeness of data).
PRECISION
It describes the reproducibility of
measurements
PRECISION
PRECISION is Statistically measured through:
▪ Standard deviation
▪ Variance
▪ Coefficient of variation
▪ Other measures
MEASUREMENT OF ACCURACY: You determine the error first before the accuracy with
these 2 measurements. What are those?
ABSOLUTE ERROR, RELATIVE ERROR
is equal to the difference
between the actual reading Xi, and the true (or
accepted) value Xt; bears a sign
ABSOLUTE ERROR
describes the error in relation to
the magnitude of the true value, and may, therefore,
be more useful than considering the absolute error in
isolation
RELATIVE ERROR
EA = Xi – Xt
(lowerscript ang A)
(ABSOLUTE ERROR)
Et =( (Xi−Xt) / Xt) × 100%
(RELATIVE ERROR)
Where Xi =
actual reading
Xt =
= true or accepted value
the most recognized measure of precision
STANDARD DEVIATION
May be used to calculate the precision of
measurements for an entire population (σ) or
a sample (s) of the population
STANDARD DEVIATION
If you have plenty of data, __ is better to use
SD
If we’re dealing with only 2 replicates,
you can opt for measurement for
_______.
Range
RSD = (S / x̄)
where:
s – (?)
x̄ – (?)
sample standard deviation, mean
Is basically the RSD in percentage
CV = (S/x̄) × 100%
COEFFICIENT OF VARIATION
The square of the Standard Deviation
VARIANCE
The sample variance (s^2) is
an estimate
of the population variance (σ2)
The difference between the largest value
in the set and the smallest
SPREAD OR RANGE
ω = XH – XL
where: XH =?
XL = ?
Highest Value; Lowest Value
consists of all certain digits in a
measurement plus the first uncertain digit
SIGNIFICANT FIGURES
Laboratory investigations usually involve the
taking of and ____________________ of measurements.
interpretation
RULES FOR SIGNIFICANT FIGURES:
RULE 1: All nonzero digits in a measurement
are significant.
RULE 2: Interior zeros (zeros between nonzero
numbers) are significant.
RULE 3: Leading zeros (zeros at the beginning of
a number) are NOT significant.
RULE 3: Trailing zeros (zeros at the end of a
number)
When adding or subtracting measurements with
significant figures, the result has the same number
of decimal places as the measurement with the
________________ number of decimal places.
lowest
When multiplying or dividing measurements with
significant figures, the result has the same number
of significant figures as the measurement with the
lowest number of ______________.
significant figures
In a ________________ of a number, keep as many digits to the
right of the decimal point as there are significant
figures in the original number.
logarithm
In an ___________________________of a number, keep as many digits
as there are digits to the right of the decimal point
in the original number.
antilogarithm
Antilog is basically a reverse function of Log.
You can calculate it by pressing _____ key
before pressing the log key.
[Shift]
RULES FOR ROUNDING OFF NUMBERS:
If the digit to be dropped is greater than 5, the last
retained digit is increased by ___.
one
If the digit to be dropped is less than 5, the last
remaining digit is left _______.
as it is
If the digit to be dropped is 5, and if any digit following
it is not zero, the last remaining digit is increased by
____.
one.
If the digit to be dropped is 5 and is followed only by
zeroes, the last remaining digit is increased by one if
it is ___, but left as it is if ____.
odd; even
