Hi

Firstly ppg is not an international unit, the units are µg/L or µg/kg

This notion of trace is related to the power of analytical tools used, and efforts to be made to measure it.

1 µg/L and 0.1µG/L are the detection limits of the analytical methods there are some three or four decades.

In addition, in case of the envionmental measurement, the "race to ppt" does not make too much sense,

The no observed effect concentration (NOEC) or predicted no effect concentration (PNEC) must guide our analytical effort.

So instead of saying "traces and ultra-trace", use concentrations as NOEC or PNEC or any other concentrations with toxicological significance

Each country has their own agencies for trace analysis values. There are some databases for pesticides MRL values are-EU Pesticides database, Codex etc.

@ Philippe:

Thanks,

If our sample (e.g liquid samples) some elements is present so how to categorize that under major, minor, trace and ultra trace level based on the concentration?

The Metal Trace Elements (former heavy metals) are conventionally defined as metals with an average natural concentration in the upper continental crust less than 1g/kg ( geological background) . Some of them are essential to the functioning of biological processes : the oligo-elements; but they can be toxic to higher levels (eg, Cu and Zn) .

and some geological formations may have abnormally high concentrations of trace elements (eg. Ore veins : mines)

So, the notion of trace elements is purely conventional and presents little interest in environmental toxicology (NOEC, PNEC or any relevant toxocological essay. If you need to interpret some analytical results, refer rather to toxic concentrations, these notions of trace and ultratrace which are concepts related to our analytical capabilities.

roughly, you can use the following levels:

major elements: mg/L

trace elements: µg/L

ultra-trace elements: ng/L

But remember, as stated by Paracelsus in the sixteenth century, that : Alle Dinge sind Gift, und nichts ohne Gift ; allein die Dosis macht das ein Ding kein Gift ist.

or more simply : only the dose makes the poison

Synthetic compounds have nothing to do in the environment and are therefore always present as trace (hopefully).

@ Philippe: please mention the range

for analyte

1-100% Major

0.01-1% Minor

1 ppb to 100ppm Trace

0.1g macro

0.01-0.1g semimicro

0.0001- 0.01g micro

Hi... In groundwater analysis many authors define as:

Major constituents: Substances in concentrations over 1mg/L

Minor constituents: Substances in concentrations between 1mg/L and 0.1 mg/L

Trace constituents: Substances in concentrations under 0.1 mg/L

I never have read about ultra trace leves of concentration, but you can consult these information in book as:

Knödel, Lange & Voigt. (2007) Environmental Geology: Handbook of Field Methods and Case Studies. Section 5.3: Methods for characterizing geochemical and microbiological conditions. (Thes book is a reference manual from Federal Institute for Geosciences and Natural Resources of Germany)

Singhal & Gupta. (2010). Applied Hydrogeology of Fractured Rocks. (They are from India)

I Repeat: These ranges was defined for GROUNDWATER Analysis. As in another answers was be written, these distribution of ranges depend of media which you are characterized and criteria for their distribution depends of natural backgrounds in each one (Air, water, soil, biological tissue).

Another reference for discussion about use of units as ppm, ppb or ppt you can found in Dobs (1989). Concentration units in water chemistry. Pure &Appl. Chem., Vol. 61, No. 8, pp.1511-1515 (An article published by IUPAC). And for the discussion about 'Heavy Metals' you can see this article: Duffus (2002). "Heavy Metal" - A meaningless term?. Pure Appl. Chem., Vol. 74, No. 5, pp. 793–807 (An article published by IUPAC too).

I hope that help.

Greetings!

According to IUPAC definition the major, minor, trace and ultr-trace analytes is defined accoriding to their prasence as Major(>1%), minor(1-0.01%), trace (0.01-0.0001%) and ultra-trace(

According to IUPAC definition the major, minor, trace and ultr-trace analytes is defined accoriding to their prasence as Major(>1%), minor(1-0.01%), trace (0.01-0.0001%) and ultra-trace(

The definition of IUPAC is very clear on this. Major ( greater than 1%), minor(between 0.1 per thousand and 1 percent), trace (between 0.1 per thousand and 0.1ppm), ultra trace (less than 0.1ppm).

IMHO this discussion is a reminiscence of the problem of universals!

What is the interest to know whether a compound is present in major or trace concentration?

What matters in envrionnemental point of view is what are its possible effects.

Possible effect but also quantity and avalaibility. With speciation, some elements are toxic and other not. see AsIII, As V, ...

According to Analytical Chemistry books such as" Fundamentals of Analytical Chemistry" Skoog& West, I agree to Mahesh Tiwari.

for analyte

1-100% Major

0.01-1% Minor

1 ppb to 100ppm Trace

0.1g macro

0.01-0.1g semimicro

0.0001- 0.01g micro

According to Analytical Chemistry books such as " Fundamental of Analytical Chemistry" Skoog & West, I agree to Mahesh Tiwari:

for analyte

1-100% Major

0.01-1% Minor

1 ppb to 100ppm Trace

0.1g macro

0.01-0.1g semimicro

0.0001- 0.01g micro

For me, the distinction between trace and ultra-trace element concentration does not make much sense. It will strongly depend on the accuracy/precision of the analytical technique used in the analyses. What is in "ultra-trace" concentrations in a laboratory or equipment, may be just "trace" in another facility/technique with a much higher resolution. Nowadays there exist extremely accurate spectroscopic methods (e.g., NAA) which allow to detect elements in environmental samples at concentrations of ppt. Also, this classification varies largely between different scientific fields, e.g., the consideration of "ultra trace" will not be the same in biogeochemistry or ecology than in metrology or in advanced materials science.

Major elements are usually considered to be above 1%, minor elements are between 0.1% and 1%, and trace elements are below that and usually measured in ppm.

Best Regards