Available Methods

(A)  Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

ICP-MS is a method used to quantify most elements in the periodic table. It uses argon plasma to form ions from samples. The ions are then analysed with mass spectrometry.

Pros: Requires very small amount of sample
Cons: Certain elements cannot be analysed

(B)  High Performance Liquid Chromatography (HPLC)

HPLC is a chromatographic method which is able to be used to quantitate the concentration of p-phenylenediamine in samples.

Pros: Does not require much pre-treatment for sample, accurate injection even with manual injection with Rheodyne loop injector
Cons: Samples have to be fully dissolved in aqueous solvents


(C) Gas Chromatography Mass Spectrometry(GC-MS)

GC-MS is another viable chromatographic method able to quantitate the concentration of p-phenylenediamine. It uses a gaseous mobile phase.

Pros: Able to quantitate from peak area of retention time
Cons: Low-volatility samples require chemical derivatization

Selected method for analysis:

HPLC is selected for analysis as it does not require laborious sample preparation such as chemical derivatization. HPLC is also less expensive compared to the other methods. It also has fast analysis time. Henna is readily available in liquid form for dissolving. Reverse-HPLC can be used for the analysis of PPD since PPD is non-polar. On the other hand, ICP-MS is used to determine the metal components of the dye which is not the main purpose of our analysis.