Common lab report errors:
Writing the methods section as a “how-to” manual.
This is incorrect:
To collect the air sample take the high volume air sampler to the desired location
for sampling. Unscrew the four nuts on the filter holder and remove the frame.
Rinse both the frame and holder with acetone. Next take the filter from its foil
pouch using rinsed tongs and place it in the center of the holder. Replace the
frame on the holder and screw the four nuts back down.
This is correct (from Totten et al., 2004):
Each sample was extracted in a Soxhlet apparatus for 24 h in petroleum ether
(PUFs), dichloromethane (QFFs), or 1:1 acetone/hexane (XAD). For XAD
samples, the extracts were then liquid-liquid extracted in 60 mL of Milli-Q water.
The aqueous fractions were back-extracted with 3  50 mL of hexane in
separatory funnels with 1 g of sodium chloride. These and all other extracts were
then reduced in volume by rotary evaporation and subsequently concentrated via
N2 evaporation
Inexact phrases
Phrases such as “very similar”, “a lot higher”, “pretty good agreement” etc. are
COMPLETELY MEANINGLESS. They should always be replaced with exact phrases
such as “concentrations were within 10% of each other”, or “sample A was more than
twice as high as sample B.” Let the reader judge whether 10% is “pretty good” or
whether twice as high is “a lot higher.”
Significant figures. When in doubt use only 2. Two sig figs suggests that you have less
than 10% uncertainty in your numbers, because the universal assumption is that where no
specific error limits are given, the last digit is uncertain to  1. So 10 is assumed to be 10
 1, which implies an uncertainty of 10%. Likewise, 99 implies 99  1, which represents
about 1% uncertainty (1/99 = 1%). It is highly unlikely that anything we do in this lab
will give you an uncertainty of less than 1%, so you are usually safe with 2 significant
figures. What is significant? Here are some examples:
2 sig figs:
3 sig figs:
4 sig figs:
3400
30400
304100
34
304
3041
3.4
30.4
30.41
0.0034
0.00304
0.003041
30.*
30.0
30.00
3.0
0.00300
0.003000
0.0030
*having the decimal point there makes the zero significant.
By the way, when you write numbers smaller than 1, there should be a zero before
the decimal point: 0.46 is correct, .46 is not.
Equations should be numbered, and every symbol used in the equation must be defined
and the units of the symbol should also be clearly stated.
References. When you reference or “cite” something, it means that you refer to it in the
text, and then list the full reference at the end of the paper in the References or Works
Cited section. You must cite a reference whenever you quote from it, restate an idea
from it, or use facts or numbers from it. You should include the citation every time you
use something from it, thus you may have to cite the same reference several times in your
lab report. You may use either the parenthetical or numbered method of citation. In
general, references to works that have not been peer reviewed should be avoided.
This includes dissertations and web pages and class handouts! Periodical references
should contain ALL authors’ surnames followed by initials, journal abbreviation, year,
volume number, and page range.
For parenthetical references, use the following format:
One author: PCBs have been measured in New Jersey air (Totten, 2000).
Two authors: PCBs have been measured in New Jersey air (Totten and Potter, 2000).
> two authors: PCBs have been measured in New Jersey air (Totten et al., 2000).
The References section then lists the references in alphabetical order. Useful tip: you
can highlight all of your references and go to Table…Sort and then leave the defaults
(which are to sort by paragraphs), click “okay”, and Word will sort your references
alphabetically for you (they don’t have to be in a table).
For numbered references, they must be numbered in the order in which you refer to them
in the text. The first time you cite a reference, it is (1) and so on. If you refer to the same
paper later in report, it is still (1). The References section then lists the references in the
order in which they were cited, NOT in alphabetical order.
What is a peer-reviewed reference? Generally, anything in a journal is peer-reviewed.
Everything else is not, including books, class handouts, government reports, and
dissertations. WEB PAGES, INCLUDING WIKIPEDIA, ARE NOT PEER
REVIEWED AND SHOULD BE AVOIDED AS REFERENCES. CITING
INFORMATION OBTAINED VERBALLY (FOR EXAMPLE, THROUGH A
LECTURE) IS ALSO UNACCEPTABLE. THIS INCLUDES CITING
POWERPOINT LECTURE NOTES. GO BACK TO THE ORIGINAL WRITTEN
PEER-REVIEWED REFERENCE.
The format of the references at the end of the lab report is up to you, but below are a
couple of examples of good formats. Note how they both include ALL authors.
Elsevier format:
Falconer, R.L. and Bidleman, T.F., 1994. Vapor Pressures and Predicted Particle/Gas
Distributions of Polychlorinated Biphenyl Congeners as Functions of
Temperature and Ortho-Chlorine Substitution. Atmospheric Environment, 28:
547-554.
ACS format:
Bamford, H. A.; Poster, D. L.; Baker, J. E. Henry's Law constants of polychlorinated
biphenyl congeners and their variation with temperature. J. Chem. Eng. Data
2000, 45, 1069-1074.
Formatting errors. Get to know Word.
For subscripts and superscripts, there are two good ways to format them:
1. Highlight the text (usually a number) you want to format and go to on the
Home tab click on the super or subscript buttongs. Since this is tedious, you
may choose to…
2. There is an even easier way, which is to highlight the text and then hit CTRLSHIFT-EQUALS SIGN for superscripts and CTRL-EQUALS SIGN for
subscripts.
Equations: Go to Insert…Equation. This opens up an equation editor that should be
self-explanatory (I hope). If the equation symbol is grayed out on your version of
word, try cutting a pasting an equation in from one of the course handouts. Then
double-click on it to edit it.
Greek symbols: Go to Insert…Symbol. If the symnbol you want isn’t in the bos of
frequently used symbols, select “more symbols.” This opens a dialogue box. You
may have to go to the Font box and scroll down to select Symbol font. This font
contains most Greek letters as well as the , , arrows, and other useful stuff.
English errors: common mistakes include:
Then/than – “Then” refers to time in some way. “The standards were stirred and
then analyzed.” “Than” makes a comparison: “The sulfate levels in the urban
samples where higher than those in the rural samples.”
Absorbance/Absorbency – Absorbance is what we measure with a
spectrophotometer. Absorbency is the property of a substance that allows it to
absorb water. Absorbency is usually used when describing toilet paper, not your
sample solution.
Like/such as – If you can substitute “such as” for “like” in a sentence without
changing the meaning, you should. Although we use it in many ways,
technically, “like” can mean only two things, either “enjoy” or “similar to”. I like
chocolate, and men are like dogs.
Do/due – “Due” means “resulting from”. Poor results were due to equipment
malfunction.
A chromatograph is an instrument. A chromatographer is the person who is
running the chromatograph. Chromatography is the output of the
chromatograph.
Run. You should almost never use “run” or “ran” in a lab report. Unless you put
on your track shoes and ran a mile, there is no need to use the verb run. You
analyze or measure samples, you do not run them.