When someone is evaluating dissimilar things, you might hear them say \u201cit\u2019s like comparing apples and oranges.\u201d In the world of pesticide residue analysis, where scientists evaluate real apples and oranges, there are big differences between them, but the variation doesn\u2019t stop there. Even within a commodity, there are potentially significant differences that can affect results. In this article, we will discuss the analysis of pesticides in oranges using QuEChERS and look at the effect of extracting whole fruit versus separate peel and pulp samples.<\/p>\n\n\n\n
From an analytical perspective, an orange\u2019s peel has characteristics that differ from those of the pulp within it. The principal differences between the peel and pulp considered here are the relative water, oil, and sugar content. Pulp contains high amounts of water and sugar compared to peel, whereas peel contains less water and more oil than pulp.<\/p>\n\n\n\n
When choosing sample preparation procedures, it is common to tailor the approach to the characteristics of the commodity. But, despite the very different characteristics of the orange\u2019s component parts, the whole fruit is often processed for analysis. While preparing the whole orange certainly can work for many pesticides, there may be instances where poor recoveries are observed. Poor recoveries have many potential causes, but in the case of heterogeneous samples, such as oranges, differences in the nature of the sample components could be a contributing factor. Here we present two examples that explore the analysis of pesticides in oranges and the differences that were observed based on sample preparation approaches.<\/p>\n\n\n\n
During a project where we were evaluating various QuEChERS products for the extraction and cleanup of a list of LC-amenable pesticides (cat.# 31971) in a wide variety of spiked commodities using LC-MS\/MS, we observed that when the orange was prepared separately as peel and pulp samples, a significantly larger number of pesticides exhibited higher recoveries in the separated peel and pulp samples compared to the whole orange sample (Figure 1).<\/p>\n\n\n