Surface‐EnhancedRaman Spectroscopy: Theory and Application to the Analysis of Chlorpyrifos in Orange Juice

Abstract

Pesticides are required to increase crop yields and volumes to feed the growing world use population. Unfortunately, many developing countries use an excess of pesticides or those which are banned. Nearly half of the fruit consumed in the USA is imported, and it is estimated that 5% exceeds acceptable pesticide levels. Less than 1% of the food is tested because methods are slow and the equipment is restricted to the laboratory. This chapter describes the use of surface‐enhanced Raman spectroscopy to perform field measurements of pesticides in fruit. Raman spectroscopy provides the necessary specificity to distinguish the numerous pesticides in use, while surface enhancement using silver nanoparticles provides the necessary part‐per‐billion sensitivity. A simple SERS‐active sampling device and field‐usable Raman analyzer were used to measure 50 ppb chlorpyrifos in orange juice within 10 min. This chapter also includes a brief description of SERS theory.

Measurement of CO2 in Water from an Ultraviolet Oxidizer for a Space-Worthy Wastewater Recovery System Using Raman Spectroscopy

“…Silver colloids were prepared according to previously published procedures. 14 Initial solutions of 300 g/L KHCO 3 were prepared, diluted, and pH adjusted to 8 and 11.5 using NaOH, to produce two series of samples from 3 to 120 mg/L carbon for measurements. The samples were added to the quartz cuvettes, capped, and sealed with parafilm VWR (Radner, PA) to prevent CO 2 loss.…”

“…SERS involves the generation of a plasmon field at the surface of gold or silver nanoparticles by a laser that amplifies the Raman signal intensity of a chemical in that field by as much as six orders of magnitude. 13,14 While SERS has been predominantly used to measure trace chemicals, such as drugs in biological fluids, 15 there are several publications describing SERS measurements of CO 2 on copper surfaces to elucidate catalysis, 16,17 and one publication of CO 2 in water with modest enhancements of 10 2 and 10 4 on gold and silver, respectively. 18…”

“…SERS involves the generation of a plasmon field at the surface of gold or silver nanoparticles by a laser that amplifies the Raman signal intensity of a chemical in that field by as much as six orders of magnitude. 13,14 While SERS has been predominantly used to measure trace chemicals, such as drugs in biological fluids, 15 there are several publications describing SERS measurements of CO 2 on copper surfaces to elucidate catalysis, 16,17 and one publication of CO 2 in water with modest enhancements of 10 2 and 10 4 on gold and silver, respectively. 18 Here, we present the development of a compact Raman system used to measure SERS of carbonate (CO 3 =) at the required TOCA concentrations, and measure Raman of CO 2 in the effluent water collected from a new oxidizer at KBRwyle being developed for the next generation TOCA.…”

Detection of Bacillus anthracis Spores Using Peptide Functionalized SERS-Active Substrates

“…While sensitivity of the analyzer was sufficient to detect visible quantities of spores, it was unable to detect invisible quantities on contaminated surfaces that could result in infection. Recognizing this limitation we also have been investigating surface-enhanced Raman spectroscopy to detect trace quantities of spores, since it is capable of increasing Raman signal intensities by as much as 6 orders of magnitude [16]. These efforts focused on the detection of dipicolinic acid (DPA) as an anthrax biomarker [17] as it represents approximately 10% of the spore weight as calcium dipicolinate (CaDPA) [18,19].…”