Dale A. Chatfield
Professor Emeritus and Former Chair
- Ph. D., University of North Carolina
- M.S., Oakland University, Michigan
- B.S., Oakland University, Michigan
To understand the functions of the cell in diseased states, it is advantageous to study the biochemistry of single cells. This places a tremendous burden on the analyst to find extremely sensitive methods of chemical detection. Towards this end, the focus of our laboratory is to develop analytical methods to separate and detect biologically important compounds at femtomole to attomole (10-15 to 10-18 mole) concentrations. The samples we analyze are molecules that are of interest for medical diagnostics and research. The testing methodologies that we use are chromatographic concentration and separation techniques with mass spectrometric (MS) methods for identification and quantitative analysis.
The MS methods of analysis lend well to the analysis of extremely small (nanoliter) samples, but these require special handling procedures to get the samples into the MS. We are refining techniques in the manufacture of 10 to 75 um diameter micro-HPLC monolithic silica chromatographic columns. Students in my research group acquire a thorough understanding of how to use instruments to their optimum capacity, construction and modification of existing equipment. In addition they acquire skills in method development and validation of analytical procedures. Several applications of these methods are described below.
The measurement of chemicals in the blood has been used as the "gold standard" in medical diagnosis of health and of disease states. Alternate non-invasive methods of sample collection are being sought so that patients can self-administer tests at home. Two candidate methods we have studied include breath and saliva collection and analysis. We have developed a breath collection device to detect all volatile organic compounds (VOCs) in breath to 0.02 ppb from a single breath. Among the >250 compounds normally present in breath are endogenous compounds, body metabolites expelled via breath from the blood. We have used breath samples to monitor exposure to toxic chemicals and to identify endogenous biomarker compounds in healthy subjects. Parotid saliva collection is an ideal candidate for home diagnostic use because patients can collect it within a few minutes. Whole saliva has been used for some time to monitor many compounds such as steroids, drugs and metabolites produced from oxidative stress, periodontal disease, diabetes, and cancer, among others. With it we have measured more than 120 VOC constituents in whole and parotid saliva.
The Center for Disease Control (CDC) has implicated childhood exposure from cigarette smoke to symptoms of emphysema. Thus, there is great interest in determining levels of secondhand smoke exposure in the home and workplace. We have developed and validated a method using a passive monitor to measure nicotine concentrations in air. The accepted method to monitor nicotine exposure is from the measurement of nicotine metabolites in urine samples. With the assistance of the CDC, we have developed and validated methods to detect cotinine, a major nicotine metabolite, and more recently extended the method to include trans-2'-hydroxycotinine. These methods use the sensitive methods of liquid chromatography and tandem mass spectrometry.
Bile acids synthesized from cholesterol in the body are involved in fat digestion via enteropatic circulation. Secondary bile acids, formed by intestinal bacteria, are implicated in childhood intestinal disorders (diarrhea). In conjunction with UCSD Medical School, we have developed procedures to measure 39 different secondary bile acid derivatives using GC-MS procedures. Samples from preclinical studies have shown that in most cases altered bile acid metabolism is responsible for of childhood constipation.
- Schmitz KE, Hovell MF, Wong CA, et al.,
The Reliability and Practicality of the Arkansas Method Assay of Isoniazid Adherence
Clinical Nursing Research 2010, 19 131-143.
- Hofmann AF, Loening-Baucke V, Lavine JE, et al.,
Altered Bile Acid Metabolism in Childhood Functional Constipation: Inactivation of Secretory Bile Acids by Sulfation in a Subset of Patients
Journal of Pediatric Gastroenterology and Nutrition 2008, 47 598-606.
- Matt GE, Quintana PJE, Hovell MF, et al.,
Residual tobacco smoke pollution in used cars for sale: Air, dust, and surfaces
Nicotine and Tobacco Research 2008, 10 1467-1475.
- Wang L, Liu XD, Chatfield D, et al.,
Simultaneous determinations of nicotine and metabolites by LC-MS using an acclaim mixed-mode HILIC-1 column
LC GC North America 2008, Feb 56-57.
- Hamilton JP, Xie GF, Raufman JP, et al.,
Human cecal bile acids: concentration and spectrum
American Journal of Physiology-Gastrointestinal and Liver Physiology 2007, 293 G256-G263.