title: Rapid analysis of the skin irritant p-phenylenediamine (PPD) in henna products using atmospheric solids analysis probe mass spectrometry.
abstract: Henna (Lawsonia inermis) is applied to stain keratin, present in hair, skin and fingernails, a red-orange or rust colour. Producers of temporary tattoos mix the aromatic amine compound, para-phenylenediamine (PPD) into natural henna to create 'black henna' that rapidly stains the skin black. However, PPD may cause severe delayed hypersensitivity reactions following skin contact. This study proposes a rapid direct-analysis method to detect and identify PPD using an atmospheric solids analysis probe (ASAP) coupled to a Q-ToF mass spectrometer (MS). Since laborious, multistep methods of analysis to determine PPD are undesirable, due to the instability of the compound in solution, a screening method involving no sample preparation steps was developed. Experiments were carried out to optimise the corona current, sample cone voltage, source temperature, and desolvation gas temperature to determine ideal ASAP-Q-ToF-MS analysing conditions. Eleven of the 109 henna samples, originating from various countries, tested positive for PPD when henna products were screened using ASAP-MS, without any form of sample preparation other than grinding. Ultra-performance liquid chromatography electrospray ionisation-mass spectrometry (UPLC-Q-ToF-MS) was subsequently used to confirm the results from ASAP and to determine the concentrations of PPD in henna products. The allergen was detected in the same eleven samples, with concentrations ranging from 0.05-4.21% (w/w). It can be concluded that the sensitivity of the ASAP-MS technique is sufficient (limit of detection=0.025% w/w) to allow screening of henna samples for the presence of PPD. This relatively new technique can be applied to commercial products without extraction, sample treatment or chromatographic separation.
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Science, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa.
authors.forename: Weiyang
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Science, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa.
authors.forename: Thobile A N
authors.initials: TAN
authors.lastname: Nkosi
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Science, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa; SAMRC Herbal Drugs Research Unit, Faculty of Science, Tshwane University of Technology, Private Bag X680, Pretoria, 0001, South Africa.
authors.forename: Sandra
authors.initials: S
authors.lastname: Combrinck
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Science, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa; SAMRC Herbal Drugs Research Unit, Faculty of Science, Tshwane University of Technology, Private Bag X680, Pretoria, 0001, South Africa. Electronic address: viljoenam@tut.ac.za.
authors.forename: Alvaro M
authors.initials: AM
authors.lastname: Viljoen
authors.affiliation: 339 Tallmadge Rd., Kent, OH 44240, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Cartwright-Jones
mesh_terms: D000485:Allergens / Q000009:adverse effects / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004396:Coloring Agents / Q000009:adverse effects / Q000032:analysis / Q000737:chemistry; D007509:Irritants / Q000009:adverse effects* / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D009285:Naphthoquinones / Q000008:administration & dosage* / Q000032:analysis / Q000737:chemistry*; D010655:Phenylenediamines / Q000009:adverse effects* / Q000737:chemistry*; D012867:Skin / Q000187:drug effects*
chemical_list: D000485:Allergens; D004396:Coloring Agents; D007509:Irritants; D009285:Naphthoquinones; D010655:Phenylenediamines; C005090:lawsone; C029728:4-phenylenediamine
keywords: Atmospheric pressure solids analysis probe; Henna; Lawsonia inermis; para-Phenylenediamine (PPD)