﻿ If LOD is 0.01%, how much sample should I weigh and dilute? - Chromatography Forum

## If LOD is 0.01%, how much sample should I weigh and dilute?

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

### If LOD is 0.01%, how much sample should I weigh and dilute?

Hello,

I am attempting to develop a method for the analysis of sugars using HPLC-RID.

My limit of detection for a specific sugar is roughly 0.01% or 0.1 mg/ml standard.

In my sample I am expected to see roughly 1-20% of the standard. What should my sample preparation be (concentration in mg/ml)?

### Re: If LOD is 0.01%, how much sample should I weigh and dilute?

chemist23 wrote:
Hello,

I am attempting to develop a method for the analysis of sugars using HPLC-RID.

My limit of detection for a specific sugar is roughly 0.01% or 0.1 mg/ml standard.

In my sample I am expected to see roughly 1-20% of the standard. What should my sample preparation be (concentration in mg/ml)?

Does that mean you expect your sample to be 0.0001%-0.002% by weight/volume and you need to know how to concentrate, or that your sample will range in the 1-20% by weight/volume and you need to know how to dilute?
The past is there to guide us into the future, not to dwell in.

### Re: If LOD is 0.01%, how much sample should I weigh and dilute?

James_Ball wrote:
chemist23 wrote:
Hello,

I am attempting to develop a method for the analysis of sugars using HPLC-RID.

My limit of detection for a specific sugar is roughly 0.01% or 0.1 mg/ml standard.

In my sample I am expected to see roughly 1-20% of the standard. What should my sample preparation be (concentration in mg/ml)?

Does that mean you expect your sample to be 0.0001%-0.002% by weight/volume and you need to know how to concentrate, or that your sample will range in the 1-20% by weight/volume and you need to know how to dilute?

I am expecting the sample to have 1-20% weight/weight of the compound of interest. For example I am expecting 1-20% of my sample weight to be fructose.

In my trial runs for fructose standard, my lowest detection limit is ~ 0.1 mg/ml (0.01%).

How much sample should I weight and dilute?

### Re: If LOD is 0.01%, how much sample should I weigh and dilute?

chemist23 wrote:
James_Ball wrote:
chemist23 wrote:
Hello,

I am attempting to develop a method for the analysis of sugars using HPLC-RID.

My limit of detection for a specific sugar is roughly 0.01% or 0.1 mg/ml standard.

In my sample I am expected to see roughly 1-20% of the standard. What should my sample preparation be (concentration in mg/ml)?

Does that mean you expect your sample to be 0.0001%-0.002% by weight/volume and you need to know how to concentrate, or that your sample will range in the 1-20% by weight/volume and you need to know how to dilute?

I am expecting the sample to have 1-20% weight/weight of the compound of interest. For example I am expecting 1-20% of my sample weight to be fructose.

In my trial runs for fructose standard, my lowest detection limit is ~ 0.1 mg/ml (0.01%).

How much sample should I weight and dilute?

You will want at least 0.1mg/ml of final prep. 1% is 10,000mg/L or 10mg/ml. or 10mg/g in solid sample. So if you weigh 1g sample and dilute to 100ml final volume the solution should contain 10mg/100ml or 0.1mg/ml. That would put your lowest expected concentration at your lowest possible detection limit. Of course if you want to quantify you will want that sample to give a concentration above the detection limit so better to use more weight or less volume.

Another way to look at it is you expect 1% and you can see 0.01% so simply divide 1.0 by 0.01 and you get 100, which is the factor you can dilute your sample by to achieve your target concentration and you can do the 100 fold dilution in any manner you wish, 1g/100ml or 10g/1000ml ect.
The past is there to guide us into the future, not to dwell in.

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