Application Released: November 2017 Application Note 135 The complementary roles of dynamic headspace and sorptive extraction in the analysis of fragranced consumer products using TD–GC–MS Summary Background to the sampling equipment This Application Note describes the analysis of three fragranced In this study, three sampling procedures were used, to consumer products – fabric conditioner, washing detergent and establish how well they performed for each sample: washing powder – using three sampling approaches in • Method A – Dynamic headspace sampling using the conjunction with analysis by thermal desorption–gas Micro-Chamber/Thermal Extractor™ (µ-CTE™) (Figure 1). chromatography–mass spectrometry (TD–GC–MS). As well as ™ comparing the analyte ranges covered by dynamic headspace • Method B – Headspace sorptive extraction using HiSorb sampling, headspace sorptive extraction and immersive sorptive probes (Figure 2). extraction, the ability of Markes’ re-collection technology to • Method C – Immersive sorptive extraction using HiSorb streamline method development and validation is discussed. probes. These three methods are outlined in Figure 3. Introduction The success of many personal care and household cleaning products has long depended on the precise mix of aroma- active compounds that they release. For example, manufacturers are continuously developing new formulations that offer different (or longer-lasting) fragrances, while consumers loyal to a well-established brand can notice even the slightest variation in fragrance quality. In addition, there has been increasing concern over the presence of potentially harmful compounds – such as allergens – in fragrance formulations. These factors have led to an ongoing need to monitor the volatile and semi-volatile organic compounds (VOCs and SVOCs) released by fragranced consumer products. Sampling and analysing VOCs and SVOCs from a wide range of products and materials has long been carried out using gas Figure 1: The six-chamber (left) and four-chamber (right) models of chromatography (GC), enhanced by pre-concentration using the µ-CTE™. Both models use gentle heating and a flow of inert gas thermal desorption (TD). TD provides a versatile and high- to release VOCs and SVOCs from solid or liquid samples. sensitivity alternative to traditional sample preparation methods for GC, such as solvent extraction or static headspace, and involves minimal manual sample handling while being applicable to the widest possible range of GC-compatible analytes. In the field of consumer products, TD has generally been associated with sampling vapours released from solid samples, but recent developments in sorptive extraction have improved the applicability of TD pre-concentration technology to aqueous samples. This improvement in the versatility of TD is particularly valuable for analysis of fragranced products, where the Figure 2: Regular-length and short-length HiSorb probes (left), samples requiring analysis may be powders, waxes, creams or available in stainless steel or inert-coated stainless steel. The probes liquids. This Application Note aims to highlight this versatility are fitted with a section of PDMS (right) that adsorbs vapour-phase or solution-phase VOCs and SVOCs from the samples, facilitating by demonstrating the use of dynamic headspace sampling, minimal sample handling. headspace sorptive extraction and immersive sorptive extraction for the analysis of VOCs and SVOCs in three fragranced cleaning products – two liquids and one powder. Markes International Ltd T: +44 (0)1443 230935 F: +44 (0)1443 231531 E: [email protected] www.markes.com Page 2 Background to thermal desorption Dynamic Headspace Immersive A headspace B sorptive C sorptive All three sampling approaches described above involve extraction extraction extraction analysis by thermal desorption (TD). This is a versatile GC pre-concentration technology that is used to analyse VOCs 1 1 1 and SVOCs in a wide range of sample types. By concentrating organic vapours from a sample into a very small volume of carrier gas (Figure 4), TD maximises sensitivity for trace-level target compounds, helps to minimise interferences, and routinely allows analyte detection at the ppb level or below. It also greatly improves sample throughput, by combining Sample loading: Headspace Immersive sample preparation, desorption/extraction, pre-concentration The sample is sampling: sampling: and GC injection. In this study we use the TD100-xr™ for fully placed inside one A short-length A standard-length of the chambers of HiSorb probe is HiSorb probe is automated analysis of up to 100 sample tubes. the µ-CTE. suspended above immersed in the the solid or liquid sample in a 20 mL sample in a 20 mL vial. (Short-length A Tube desorption and inlet split: vial. probes can be used with 10 mL vials). Sample tube heated in a flow of carrier gas and analytes swept onto an electrically 2 2 cooled focusing trap, typically held between ambient be tu e and –30°C. pl m Sa p be tra tu g n in s tio u c o ec F oll -c re t/ li Equilibration: Analyte extraction: p S The chamber lids The HiSorb Agitator are closed, and the efficiently mixes system allowed to and heats the equilibrate under a sample, to maximise During either set gas flow and extraction efficiency. stage, the flow of temperature. analytes can be split and re-collected onto a clean sorbent tube. 3 3 C G o B Trap desorption and outlet split: T Focusing trap rapidly heated (up to 100°C/s) in a reverse flow of carrier gas (‘backflush’ p be tra tu g n operation), to transfer in s tio Sampling: Probe washing: u c the analytes to the GC o ec TD tubes are Probes are washed F oll -c column. re attached to the with HPLC-grade t/ li p chamber outlets, water, dried with a S and vapours from lint-free tissue, and the sample are then inserted into a swept onto them. TD tube. 4 Figure 4: Schematic showing the operation of cryogen-free thermal desorption as used in Markes’ instruments. Analysis: The tubes are analysed by automated, unattended TD–GC–MS. Figure 3: Workflow for the three sampling methods used in this study. Markes International Ltd T: +44 (0)1443 230935 F: +44 (0)1443 231531 E: [email protected] www.markes.com Page 3 Experimental TD: Instrument: TD100-xr™ (Markes International) Samples: Cold trap: Tenax TA (Markes International part no. Three fragranced household products were analysed: U-T9TNX-2S) Desorption time: 10 min • Sample 1 – Liquid fabric conditioner Desorption temp.: 280°C • Sample 2 – Liquid washing detergent Trap low temp.: 25°C • Sample 3 – Washing powder. For the immersive sorptive Heating rate: Max extraction study, a solution was prepared by dissolving 1 g Trap high temp.: 290°C of powder in 18.5 mL water. Trap hold time: 1.5 min Outlet split: 100 mL/min Dynamic headspace sampling (Method A): Split ratio: 51:1 Instrument: Six-chamber Micro-Chamber/Thermal Flow path temp.: 180°C Extractor (Markes International) GC: Sample: 2 g (solid) or 1 mL (liquid) sample Column: VF-624ms™, 60 m × 0.32 mm × 1.8 µm placed in disposable aluminium sample Oven: 40°C (3 min), then 6°C/min to 230°C tray (15 min) Chamber temp.: 40°C Inlet: 180°C Chamber flow: 50 mL/min, nitrogen Carrier gas: Helium, 2.0 mL/min Sampling time: 15 min ® Septum purge: 3.0 mL/min Sorbent tube: Packed with Tenax TA (Markes MS transfer line: 240°C International part no. C1-AXXX-5003) MS: Headspace sorptive extraction (Method B): Ion source: 230°C Sample: 10 mL (liquid) or 2 g (solid) sample in Quadrupole: 150°C 20 mL headspace vial, sealed with a Mass range: m/z 35–450 HiSorb septum seal and cap Sampler: Short-length, inert HiSorb-P1 probe Data analysis: (Markes International part no. TargetView™ GC–MS software (Markes International) was H1-AXABC-5) used to selectively remove unwanted background noise from TD tube: Empty (Markes International part no. the chromatograms, and so improve the identification of C0-AXXX-0000) lower-level analytes during subsequent automated Sample incubation: HiSorb Agitator (Markes International) comparison against a 407-component fragrance-compound Sampling temp: 40°C target library. TargetView also generated peak-area Agitation speed: 300 rpm information that allowed the amounts of each analyte Sampling time: 90 min sampled with the different techniques to be compared. Immersive sorptive extraction (Method C): Sample: 18.5 mL sample in 20 mL headspace Results and discussion vial, sealed with a HiSorb septum seal and cap 1. Overall fragrance profiles Sampler: Standard-length, inert HiSorb-P1 probe The fragrance profiles of the fabric conditioner, washing (Markes International part no. detergent and washing powder (using each of the sampling H1-AXAAC-5) techniques) are shown in Figures 5, 6 and 7 respectively, with Other conditions as for Method B. major components being labelled. Corresponding lists of compounds identified by comparison against the fragrance- compound target library are shown in Tables A1–A3 (see Appendix). Markes International Ltd T: +44 (0)1443 230935 F: +44 (0)1443 231531 E: [email protected] www.markes.com Page 4 2 24 59 A 32 65 22 1 Acetone Dynamic 36 16 Ethyl 2-methylpentanoate headspace 37 45 counts) 1 22 n-Hexyl acetate 7 sampling 46 24 Limonene 16 92 Abundance (µ-CTE) 48 78 32 Dihydromyrcenol (× 10 1 42 90 93 36 Tetrahydrolinalool 0 37 Linalool 42 Benzyl acetate 24 45 Citronellyl butanoate 3 46 Gardeniol B 59 Headspace 48 Terpineol 2 22 50 β-Citronellol counts) sorptive 32 45 65 7 16 extraction 36 46 59 Isobornyl acetate 37 Abundance 1 (HiSorb) 92 65 Terpinyl acetate (× 10 48 42 78 90 93 68 Geranyl acetate 70 Eugenol 0 78 Indan-1,3-diol monoacetate 92 90 Coumarin 59 93 2 92 Lilial C 32 65 78 90 97 93 Rosacetol Immersive 68 24 36 94 Amyl salicylate counts) sorptive 22 37 70 98 100 7 95 n-Heptyl-γ-butyrolactone 1 extraction 42 94 50 95 97 Methyl (3-oxo-2-pentyl- Abundance (HiSorb) (× 10 16 cyclopentyl)acetate 98 n-Hexyl salicylate 0 100 n-Hexyl cinnamaldehyde 5 10 15 20 25 30 35 40 45 Retention time (min) Figure 5: TD–GC–MS analysis of fabric conditioner using Methods A–C.