Hi,

As you know, Trihalomethanes are a bunch of molecules, not a particular one. So, you need to be aware of what are you exactly interested in.

However, there are few instruments e.g. HPLC-MS, GC-MS which may help you in detection and determination of the amount/recovery of an exact molecule- but not all of them at once.

Dear Olalekan,

What is the method of your study?

Preparing Standards / experimental samples:

• Prepare THM Standard Ampule, 10 mg/L as chloroform for the preparation of standards ranging from 0.01, to 1 mg/L.

• Collect standards / samples in 40-mL glass bottles sealed with Teflon®-lined septa caps.

• Fill the bottles slowly to overflowing so that no air is included with the sample.

• Seal the bottles tightly and invert to check that no air has been trapped.

• Because trihalomethane compounds (THMs) are extremely volatile, immediate analysis yields

the greatest accuracy. If the samples cannot be analyzed immediately, cool samples to 4 °C.

This will slow the formation of any additional THM compounds in chlorinated samples.

• Store the samples at 4 °C in an atmosphere free of organic vapors. Samples should not be

held more than 14 days. 0.1 N Sodium Thiosulfate can be used to dechlorinate samples for

longer storage.

• Add 1 drop of 0.1 N Sodium Thiosulfate to dechlorinate a finished or distribution system

sample collected in a 125 mL bottle.

Determination of THM in experimental samples:

• Using HACH THM Plus method for the spectroscopic determination of THM as chloroform.

• The THM Plus method reacts with the trihalogenated disinfection by-products formed as the result

of the disinfection of drinking water with chlorine in the presence of naturally occurring organic

materials. These disinfection by-products (DBPs) may be produced in the treatment plant or the

distribution system as long as the water is in contact with free chlorine residual. The formation of

the DBPs is influenced by chlorine contact time, chlorine dose and residual, temperature, pH,

precursor concentration, and bromide concentration.

• The predominant DBPs formed by the chlorination of drinking water are the trihalomethanes or

THMs. The four trihalogenated compounds that form are chloroform, bromoform,

dichlorobromomethane, and dibromochloromethane. These four compounds comprise the Total

Trihalomethanes (TTHMs) group which is regulated under the Safe Drinking Water Act. The

combined concentration of the TTHMs, is regulated in drinking water samples. Other DBPs that

may be present and react under the conditions of the THM Plus method are listed in Interferences.

In the THM Plus method, THM compounds present in the sample react with

• N, N,-diethylnicotinamide under heated alkaline conditions to form a dialdehyde intermediate. The

sample is then cooled and acidified to pH 2.5. The dialdehyde intermediate formed is then reacted

with 7-amino-1,3 napthalene disulfonic acid to form a colored Schiff base. The color formed is

directly proportional to the total amount of THM compounds present in the sample. Test results are

measured at 515 nm and reported as ppb chloroform.

Please see:

Trihalomethanes, THM Plus™ Method 10132 - Hach:

https://www.hach.com/asset-get.download-en.jsa?id=7639983908

(DBPs) of drinking water using the THM Plus method - Hach:

https://www.hach.com/asset-get.download.jsa?id=50617268695