344 JOURNAL OF COSMETIC SCIENCE cally with chromotropic acid (3,4). The chromotropic acid test is based on the reaction of formaldehyde with a solution of chromotropic acid (1,8-dihydroxynaphthalene-3, 6-di­ sulfonic acid) to produce a purple species in solution. The mechanism of this reaction has not been fully elucidated (5). One difficulty with this technique is that some perfume ingredients used in cosmetics liberate aldehydes in an acid medium and give a false­ positive test. Other techniques have been reported for the determination of carbonyl compound by derivatization with 2,4-dinitrophenylhydrazine (DNPH) utilizing gas chromatography (6). In another technique, high-performance liquid chromatography (HPLC) has been used, after the derivation of formaldehyde by DNPH. This technique has been reported by Wu et al. (7). The Conway microdiffusion technique has been employed for the determination of free formaldehyde (8). This method is based on the principle of gas diffusion from a relatively large volume of solution under analysis to a very small volume of aqueous trapping solution until the free formaldehyde concentration of the test solution is same as in the absorbent solution. The contribution of the present work is attributed to the application of the solid-phase microextraction (SPME) procedure for the determination of formaldehyde in cosmetic products. SPME is a powerful alternative to traditional techniques for the extraction of volatile or semivolatile organic compounds. The method, invented in the early nineteen nineties by Prof. Janusz Pawliszyn (9) from the University of Waterloo in Ontario, utilizes a small segment of fused silica fiber coated with an appropriate material and mounted on a syringe-like device for extraction of analytes from various matrices and introduced to a chromatographic system. No solvents are used in the process. Analyte extraction and pre-concentration are combined in a single step. The technique itself has been thoroughly described (10-12) for qualitative analysis as well as for quantitative determination ( 13-15). EXPERIMENT AL REAGENTS AND MATERIALS The reagents and materials used were water (HPLC grade, J. T. Baker Inc, Phillipsburg, NJ) 37% formaldehyde solution (Sigma, St. Louis, MO) 97% pentafluorophenylhy­ drazine (Aldrich, St. Louis, MO) sodium chloride (Extra Pure, EM Industries, Dam­ stadt, Germany) deuterated acetone (Aldrich, Milwaukee, WI) formaldehyde-free so­ dium lauryl sulfate (Sulfochem SLS-BZ, Chemron, Paso Robles, CA) and formaldehyde­ free sodium laureth sulfate (Sulfochem ES-2DX-BZ, Chemron). INSTRUMENTS AND EQUIPMENT The instruments and equipment used were SPME fiber, polydimethylsiloxane/ divinylbenzene (PDMS/DVB), 65 µm, catalog no. 57326-U (Supelco, Bellefonte, PA) a headspace vial, 10 ml (Supelco) a block heater (Alltech Associates Inc, Deerfield, IL) a gas chromatograph (HP 6890) equipped with FID (Agilent Technologies, Wilming­ ton, DE) a mass spectrometer (HP-5973, Agilent) SPME septa (Pre-drilled septa,

HS-SPME-GC DETERMINATION OF FORMALDEHYDE 345 Supleco) an inlet liner for SPME (0.75 mm ID, Supelco) and a capillary column (HP-1 methyl siloxane, 30 m x 0.25 mm x 0.25 µm film thickness, Agilent). PREPARATION OF SOLUTIONS Preparation of 25% sodium chloride solution. The proper amount of sodium chloride was dissolved in HPLC-grade water. Preparation of 1.5 mM pentafluorophenylhydrazine (PFPH). The proper amount of PFPH was dissolved in HPLC-grade water. This solution was used as a derivatization agent in the present work. Preparation of 0.5000 mMJ 0.2500 mMJ 0.1250 mMJ 0.0625 mMJ 0.0313 mMJ and 0.0010 mM of formaldehyde stock standard solutions These solutions were prepared using 3 7 % formaldehyde solution (assayed as per EPA method 8315A) and diluted with formaldehyde-free sodium lauryl sulfate (Sulfochem SLS-BZ). Preparation of 0.5 mM deuterated acetone stock internal standard solution. The proper amount of acetone was dissolved with 25% aqueous solution of sodium chloride. Preparation of surfactants and cosmetic products (formaldehyde-free) Jpiked with formaldehyde To determine the recovery and precision of the current method, samples of raw materials and cosmetic products that were spiked with formaldehyde (0.05%) were analyzed ten times. The coefficient of variation (CV%) and recovery for each spiked sample was calculated. Another spiked sample (15 µg/ml) of surfactant was also analyzed eight times to determine the limit of detection (LOD), with calculated signal-to-noise ratio = 3 (S/N = 3). PROCEDURE Hydrozone. Pentafluorophenylhydrazine reacts with aldehydes and the ketones group by nucleophilic addition to the carbonyl group followed by elimination of water and the formation of pentafluorophenylhydrozone. The addition of acid, in general, is recom­ mended to promote protonation of the carbonyl because hydrazines are weak nucleo­ philes. However, this phenomenon was not observed during the study (see Figure 1). Calibration standard for hydrozone derivative. We prepared at least five concentration levels of spiked formaldehyde in formaldehyde-free sodium lauryl sulfate. We added into a ✓ .: ::CH2 F NH2 F N;::::;,-- I I F NH HYO F NH + ===== F F H - H 20 F F F F (pentafluorophenyl)hydrazine formaldehyde formaldehyde (pentafl uorophenyl )hydrazone Figure 1. Reaction between pentafluorophenylhydrazine and formaldehyde to form the respective hydra­ zone.