## 1 Introduction  
Fruit leathers (FLs) are prepared from fruit pulp, sugars and food-grade colorants. These candy snacks are produced at rates of thousands of tons per month in the US. The not-to-specification material is usually disposed of and results in additional costs. The waste material remains edible and contains valuable ingredients such as fruit pulp, sugars and acidulates. However, an unappetizing brownish color from the mixture of colorants is a problem with recycling FL to the production process. Colorant removal is a necessary step in the recycling procedure. Activated carbon adsorption proved suitable, but impractical [1]. Ozonation has been a treatment of choice for the removal of color from water or industrial wastewater [2; 3]. Ozone actually has GRAS (generally regarded as safe) status from the US Food and Drug Administration [4]. Our previous publication described how ozonation was used for research on color removal from waste FLs [5]. In this research, we describe analytical method development for quantification of ozonation by-products in a very complex matrix of FL suspension/solution. Food colorants as used in FLs, 2-naphthalenesulfonic acid (Allura Red AC, Red 40), tartrazine (Yellow 5), and erioglaucine (Brilliant Blue FCF, Blue 1), were successfully decolorized by ozone treatment. A concern of this process is generation of carbonyl compounds [5]. Among the detected carbonyl compounds, 2-furfurlural and benzaldehyde are of some health concern [6]. In addition, both ethanal (acetaldehyde) that has food uses as a flavor adjuvant [7] or natural occurrence in food [8], and hexanal, used in foods as a flavorant at 0.005 to 4 ppm to impart a fruit flavor [9], can be of concern at higher concentrations [10]. Ozonation of azo dyes has also been shown to result in a variety of aldehydes, such as butanal, hexanal, heptanal, octanal, nonanal, and decanal [11]. Carbonyl compounds have also been found as major byproducts in other ozonolysis applications, such as treatment of paper pulp and water [12] and in the oxidative disinfection of drinking water [13]. Although most of these aldehydes are of negligible or minor concern, toxicity can arise during metabolism. The two major metabolic pathways of aldehydes in the human body are oxidation to carboxylic acids and reduction to alcohols, with oxidation being both dominant and irreversible [14]. Another metabolic pathway involves interaction between the carbonyl group and thiol or amine groups, which can lead to covalent crosslinking between DNA and proteins (DNA-protein, protein-protein, DNA-DNA) [15; 16; 17]. These reactions may ultimately result in mutation and tumor formation, as studies on laboratory animals have shown [10]. Derivatization is commonly used to stabilize and extract reactive compounds from complex matrixes. Carbonyl compounds are also reactive outside of the body, and are typically derivatized for sampling [12]. For example, solid-phase extraction (SPE) has also been coupled with PFBHA derivatization for the extraction of carbonyls from wine [18]. [PERSON] _et al._ used an annular denuder coated with _O_-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) for collection of biofunctional carbonyl compounds from ambient air [19]. The captured aldehydes were then extracted using acetonitrile/CH\({}_{2}\)Cl\({}_{2}\) for instrumental analysis. Derivatization reagent of 2,4-dinitrophenyl-hydrazine (DNPH) was used as the derivatization reagent coated onto silica gel cartridges in a study on carbonyls from engine exhaust [20]. A drawback of the methods described above is that they require laborious pre-analytical sample preparation and use of solvents. Solid-phase microextraction (SPME) is a technique that integrates both sampling and sample preparation steps [21]. SPME is reusable and does not require the use of solvents. On-fiber derivatization with SPME was developed by [PERSON] and [PERSON] [22] for gaseous formaldehyde. Derivatization time was as short as 10-300 s in this procedure.