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Is 1 ppb equal to 1 μg/kg?
How do I convert salinity measured in mg/L Cl into parts per thousand as NaCl?IUPAC Recommendations for Concentration Units (ppb, ppm)Amount of substance of a molecule in a solute the same as amount of substance of constituent elements?Interpreting notation format 1.64E-02 from particulate emission dataWhat was the lithium concentration in 1940's 7-Up?Why are osmoles not considered SI units?Should residual sodium be considered in measuring sodium content of sweat?Concentration of mercury in bodyConversion from a PPB value to µg/m3 of IsobutyleneIUPAC Recommendations for Concentration Units (ppb, ppm)What does “at%” mean and how it differs from “mol%”?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
$begingroup$
In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I thought that 1 μg/kg = 1 ppb.
Is 1 ppb equal to 1 μg/kg ? What is a reason to consider ppb as incorrect ?
concentration notation units
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
$endgroup$
add a comment |
$begingroup$
In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I thought that 1 μg/kg = 1 ppb.
Is 1 ppb equal to 1 μg/kg ? What is a reason to consider ppb as incorrect ?
concentration notation units
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
$endgroup$
8
$begingroup$
Just using ppb is ambiguous unless you state the basis (eg w/w for mass %). ppb could also be referring to molar proportion or volume proportion.
$endgroup$
– matt_black
Apr 15 at 8:56
add a comment |
$begingroup$
In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I thought that 1 μg/kg = 1 ppb.
Is 1 ppb equal to 1 μg/kg ? What is a reason to consider ppb as incorrect ?
concentration notation units
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
$endgroup$
In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I thought that 1 μg/kg = 1 ppb.
Is 1 ppb equal to 1 μg/kg ? What is a reason to consider ppb as incorrect ?
concentration notation units
concentration notation units
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
edited Apr 15 at 1:32
andselisk♦
21.7k8 gold badges75 silver badges144 bronze badges
21.7k8 gold badges75 silver badges144 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
asked Apr 15 at 1:18
NakxNakx
1816 bronze badges
1816 bronze badges
8
$begingroup$
Just using ppb is ambiguous unless you state the basis (eg w/w for mass %). ppb could also be referring to molar proportion or volume proportion.
$endgroup$
– matt_black
Apr 15 at 8:56
add a comment |
8
$begingroup$
Just using ppb is ambiguous unless you state the basis (eg w/w for mass %). ppb could also be referring to molar proportion or volume proportion.
$endgroup$
– matt_black
Apr 15 at 8:56
8
8
$begingroup$
Just using ppb is ambiguous unless you state the basis (eg w/w for mass %). ppb could also be referring to molar proportion or volume proportion.
$endgroup$
– matt_black
Apr 15 at 8:56
$begingroup$
Just using ppb is ambiguous unless you state the basis (eg w/w for mass %). ppb could also be referring to molar proportion or volume proportion.
$endgroup$
– matt_black
Apr 15 at 8:56
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
You are correct suggesting that 1 μg/kg implies 1 ppb, however the reverse is not true. For instance, 1 ppb can also be 1 nmol/mol, and the reader will never have a chance to deduce which one is it unless you explicitly define the usage of the "parts per something" in the text.
This clutters the manuscript with redundant notes and causes overall confusion.
IUPAC also lists all similar symbols (ppm, ppt, ppb etc.) as deprecated; from IUPAC's “Green Book” [1, p. 98]:
Although ppm, ppb, ppt and alike are widely used in various applications of
analytical and environmental chemistry, it is suggested to abandon completely their use because of the ambiguities involved. These units are unnecessary and can be easily replaced by SI-compatible quantities such as pmol/mol (picomole per mole), which are unambiguous. The last column contains suggested replacements (similar replacements can be formulated as mg/g, μg/g, pg/g etc.).
$$
beginarraylllll
hline
textName & textSymbol & textValue & textExamples & textReplacement \
hline
ldots & & & & \
textpart per billion & textppb & 10^-9 & textThe air quality standard for ozone is a & punmol/mol \
& & & textvolume fraction of~varphi = 120~textppb & \
ldots & & & & \
hline
endarray
$$
References
- IUPAC “Green Book” Quantities, Units, and Symbols in Physical Chemistry, 3rd ed.; Cohen, R. E., Mills, I., Eds.; IUPAC Recommendations; RSC Pub: Cambridge, UK, 2007. (PDF)
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
$endgroup$
8
$begingroup$
Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
$endgroup$
– Loong♦
Apr 15 at 6:59
3
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
$endgroup$
– hBy2Py
Apr 15 at 19:08
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
$endgroup$
– M. Farooq
Apr 15 at 19:39
1
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
$endgroup$
– andselisk♦
Apr 15 at 19:49
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
$endgroup$
– M. Farooq
Apr 15 at 20:38
|
show 1 more comment
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1 Answer
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1 Answer
1
active
oldest
votes
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oldest
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active
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votes
$begingroup$
You are correct suggesting that 1 μg/kg implies 1 ppb, however the reverse is not true. For instance, 1 ppb can also be 1 nmol/mol, and the reader will never have a chance to deduce which one is it unless you explicitly define the usage of the "parts per something" in the text.
This clutters the manuscript with redundant notes and causes overall confusion.
IUPAC also lists all similar symbols (ppm, ppt, ppb etc.) as deprecated; from IUPAC's “Green Book” [1, p. 98]:
Although ppm, ppb, ppt and alike are widely used in various applications of
analytical and environmental chemistry, it is suggested to abandon completely their use because of the ambiguities involved. These units are unnecessary and can be easily replaced by SI-compatible quantities such as pmol/mol (picomole per mole), which are unambiguous. The last column contains suggested replacements (similar replacements can be formulated as mg/g, μg/g, pg/g etc.).
$$
beginarraylllll
hline
textName & textSymbol & textValue & textExamples & textReplacement \
hline
ldots & & & & \
textpart per billion & textppb & 10^-9 & textThe air quality standard for ozone is a & punmol/mol \
& & & textvolume fraction of~varphi = 120~textppb & \
ldots & & & & \
hline
endarray
$$
References
- IUPAC “Green Book” Quantities, Units, and Symbols in Physical Chemistry, 3rd ed.; Cohen, R. E., Mills, I., Eds.; IUPAC Recommendations; RSC Pub: Cambridge, UK, 2007. (PDF)
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
$endgroup$
8
$begingroup$
Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
$endgroup$
– Loong♦
Apr 15 at 6:59
3
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
$endgroup$
– hBy2Py
Apr 15 at 19:08
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
$endgroup$
– M. Farooq
Apr 15 at 19:39
1
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
$endgroup$
– andselisk♦
Apr 15 at 19:49
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
$endgroup$
– M. Farooq
Apr 15 at 20:38
|
show 1 more comment
$begingroup$
You are correct suggesting that 1 μg/kg implies 1 ppb, however the reverse is not true. For instance, 1 ppb can also be 1 nmol/mol, and the reader will never have a chance to deduce which one is it unless you explicitly define the usage of the "parts per something" in the text.
This clutters the manuscript with redundant notes and causes overall confusion.
IUPAC also lists all similar symbols (ppm, ppt, ppb etc.) as deprecated; from IUPAC's “Green Book” [1, p. 98]:
Although ppm, ppb, ppt and alike are widely used in various applications of
analytical and environmental chemistry, it is suggested to abandon completely their use because of the ambiguities involved. These units are unnecessary and can be easily replaced by SI-compatible quantities such as pmol/mol (picomole per mole), which are unambiguous. The last column contains suggested replacements (similar replacements can be formulated as mg/g, μg/g, pg/g etc.).
$$
beginarraylllll
hline
textName & textSymbol & textValue & textExamples & textReplacement \
hline
ldots & & & & \
textpart per billion & textppb & 10^-9 & textThe air quality standard for ozone is a & punmol/mol \
& & & textvolume fraction of~varphi = 120~textppb & \
ldots & & & & \
hline
endarray
$$
References
- IUPAC “Green Book” Quantities, Units, and Symbols in Physical Chemistry, 3rd ed.; Cohen, R. E., Mills, I., Eds.; IUPAC Recommendations; RSC Pub: Cambridge, UK, 2007. (PDF)
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
$endgroup$
8
$begingroup$
Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
$endgroup$
– Loong♦
Apr 15 at 6:59
3
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
$endgroup$
– hBy2Py
Apr 15 at 19:08
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
$endgroup$
– M. Farooq
Apr 15 at 19:39
1
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
$endgroup$
– andselisk♦
Apr 15 at 19:49
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
$endgroup$
– M. Farooq
Apr 15 at 20:38
|
show 1 more comment
$begingroup$
You are correct suggesting that 1 μg/kg implies 1 ppb, however the reverse is not true. For instance, 1 ppb can also be 1 nmol/mol, and the reader will never have a chance to deduce which one is it unless you explicitly define the usage of the "parts per something" in the text.
This clutters the manuscript with redundant notes and causes overall confusion.
IUPAC also lists all similar symbols (ppm, ppt, ppb etc.) as deprecated; from IUPAC's “Green Book” [1, p. 98]:
Although ppm, ppb, ppt and alike are widely used in various applications of
analytical and environmental chemistry, it is suggested to abandon completely their use because of the ambiguities involved. These units are unnecessary and can be easily replaced by SI-compatible quantities such as pmol/mol (picomole per mole), which are unambiguous. The last column contains suggested replacements (similar replacements can be formulated as mg/g, μg/g, pg/g etc.).
$$
beginarraylllll
hline
textName & textSymbol & textValue & textExamples & textReplacement \
hline
ldots & & & & \
textpart per billion & textppb & 10^-9 & textThe air quality standard for ozone is a & punmol/mol \
& & & textvolume fraction of~varphi = 120~textppb & \
ldots & & & & \
hline
endarray
$$
References
- IUPAC “Green Book” Quantities, Units, and Symbols in Physical Chemistry, 3rd ed.; Cohen, R. E., Mills, I., Eds.; IUPAC Recommendations; RSC Pub: Cambridge, UK, 2007. (PDF)
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
$endgroup$
You are correct suggesting that 1 μg/kg implies 1 ppb, however the reverse is not true. For instance, 1 ppb can also be 1 nmol/mol, and the reader will never have a chance to deduce which one is it unless you explicitly define the usage of the "parts per something" in the text.
This clutters the manuscript with redundant notes and causes overall confusion.
IUPAC also lists all similar symbols (ppm, ppt, ppb etc.) as deprecated; from IUPAC's “Green Book” [1, p. 98]:
Although ppm, ppb, ppt and alike are widely used in various applications of
analytical and environmental chemistry, it is suggested to abandon completely their use because of the ambiguities involved. These units are unnecessary and can be easily replaced by SI-compatible quantities such as pmol/mol (picomole per mole), which are unambiguous. The last column contains suggested replacements (similar replacements can be formulated as mg/g, μg/g, pg/g etc.).
$$
beginarraylllll
hline
textName & textSymbol & textValue & textExamples & textReplacement \
hline
ldots & & & & \
textpart per billion & textppb & 10^-9 & textThe air quality standard for ozone is a & punmol/mol \
& & & textvolume fraction of~varphi = 120~textppb & \
ldots & & & & \
hline
endarray
$$
References
- IUPAC “Green Book” Quantities, Units, and Symbols in Physical Chemistry, 3rd ed.; Cohen, R. E., Mills, I., Eds.; IUPAC Recommendations; RSC Pub: Cambridge, UK, 2007. (PDF)
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
edited Apr 15 at 12:40
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
answered Apr 15 at 1:31
andselisk♦andselisk
21.7k8 gold badges75 silver badges144 bronze badges
21.7k8 gold badges75 silver badges144 bronze badges
8
$begingroup$
Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
$endgroup$
– Loong♦
Apr 15 at 6:59
3
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
$endgroup$
– hBy2Py
Apr 15 at 19:08
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
$endgroup$
– M. Farooq
Apr 15 at 19:39
1
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
$endgroup$
– andselisk♦
Apr 15 at 19:49
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
$endgroup$
– M. Farooq
Apr 15 at 20:38
|
show 1 more comment
8
$begingroup$
Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
$endgroup$
– Loong♦
Apr 15 at 6:59
3
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
$endgroup$
– hBy2Py
Apr 15 at 19:08
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
$endgroup$
– M. Farooq
Apr 15 at 19:39
1
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
$endgroup$
– andselisk♦
Apr 15 at 19:49
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
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– M. Farooq
Apr 15 at 20:38
8
8
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Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
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– Loong♦
Apr 15 at 6:59
$begingroup$
Similarly in the related standard ISO 80000: "Abbreviations such as ppm, pphm, ppb and ppt are language-dependent and ambiguous and shall not be used. Instead, the use of powers of 10 is recommended."
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– Loong♦
Apr 15 at 6:59
3
3
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
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– hBy2Py
Apr 15 at 19:08
$begingroup$
This difficulty with "parts-per" notations should probably be extended to percentages as well (given that, really, 'percent' is just 'parts per hundred'). I can't tell you how many times I've struggled to identify what kind of percentage is meant: % w/w? % w/v? at. %? % v/v? For % v/v, what are the bases? Is 10% one volume A for every 9 volumes of B? For every 10 volumes of B? For 10 volumes of final mixture/solution? Headaches, headaches, headaches, every dang time.
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– hBy2Py
Apr 15 at 19:08
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
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– M. Farooq
Apr 15 at 19:39
$begingroup$
@ andselisk, I am slightly confused by this new recommendation. My question is related to the denominator in nmol/mols. Suppose I prepare 100 ppb NaCl in water. Do I have 100 nmol of NaCl in 1 mol of water? How we practically prepare it. What if my solvent is a mixture such as air. How will we calculate moles of air? This new definition does not seem to be any better than the previous ones.
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– M. Farooq
Apr 15 at 19:39
1
1
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
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– andselisk♦
Apr 15 at 19:49
$begingroup$
@M.Farooq I'm not sure I understand, and this is not a novel directive, part-per-somehing has never been a favored/preferred notation as long as I remember myself. ppb is just a fraction, use whatever quantities of the same dimensions; you have to find out the amounts to calculate ppb anyways, why is this suddenly a problem?
$endgroup$
– andselisk♦
Apr 15 at 19:49
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
$endgroup$
– M. Farooq
Apr 15 at 20:38
$begingroup$
@andselisk, I am actually wondering about different scenarios. There is a very subtle difference in using nmol/mol vs. ug/kg. The typical definition of ppb is ug X in a kg of solution not the solvent. 100 ppb NaCl in water mean 100 ug NaCl "in" 1 liter of water solution. The total volume is 1 L. The analyte is a part of the solvent weight. With 100 ppm NaCl as 100 nmol NaCl dissolved in 1 mol water. In this case, NaCl is not a part of solvent. Similarly if I have a mixture as a solvent, whose moles should we use? The 1 L and kg definition do not care about the identity of the solvent system.
$endgroup$
– M. Farooq
Apr 15 at 20:38
|
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Just using ppb is ambiguous unless you state the basis (eg w/w for mass %). ppb could also be referring to molar proportion or volume proportion.
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– matt_black
Apr 15 at 8:56