Jeff C Eichhorst

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Newborn screening programs detect treatable disorders in infants before they become symptomatic. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has greatly increased the screening possibilities by monitoring levels of amino acids and acylcarnitines. After the initial screening step, LC-MS/MS can also be used in screening positive samples as a(More)
PRIMARY OBJECTIVE To replace immunoassay screening for drugs of abuse (DOA) with a cost-effective tandem mass spectrometry method. SECONDARY OBJECTIVE To substantially expand the drugs of abuse assay menu. DESIGN AND METHODS The requirement was to perform high throughput DOA screening for 200 urine specimens/day for 40 drugs/metabolites. The total(More)
OBJECTIVE To develop a routine method for detecting methylphenidate (Ritalin) use among drug abusers using liquid chromatography-tandem mass spectrometry (LC/MS/MS). The new methodology was designed to replace less reliable and/or more expensive and time-consuming techniques (GC/MS and ELISA) currently employed in our laboratory, and to provide a combined(More)
The objective was to develop a simple routine method for quantitative measurement of endogenous formic acid in plasma and whole blood using headspace gas chromatography-flame ionization detection. (GC-FID). Two-hundred microliters of sample was placed in a 1-mL glass vial. Fifty microliters of aqueous ethanol (10%) was added as an internal standard and a(More)
17alpha-Hydroxyprogesterone is a metabolic precursor of cortisol; elevated levels of 17alpha-hydroxyprogesterone are indicative of congenital adrenal hyperplasia. Traditional determination by immunoassay is plagued by poor antibody specificity, resulting in significant interferences. This study explores an LC-MS/MS method for the quantitation of 17OHP in(More)
OBJECTIVES To determine the effects of metabolism and protein binding on the relationship between administered dose, blood levels of R methadone and biological response by measuring the free and protein-bound forms of the R and S enantiomers of methadone and EDDP, its metabolite. DESIGN AND METHODS To measure free and total drug, trough levels were(More)
We report a positive newborn screen for 3-hydroxyisovalerylcarnitine (C(5)OH) with an absence of 3-methylcrotonyl-coenzyme A carboxylase deficiency in the neonate. Subsequent blood tests demonstrated persistently elevated C(5)OH. Serial testing of the mother identified markedly elevated C(5)OH in both maternal blood and breast milk. High C(5)OH milk(More)
OBJECTIVE To measure free and protein-bound R- and S-enantiomers of methadone and its major metabolite, 2-ethylidine-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in serum. METHODS To determine free fraction, samples were filtered using ultrafiltration membranes with a molecular weight cut-off of 10,000 Da and extracted using liquid-liquid extraction. The(More)
OBJECTIVE To develop a routine method for quantitative measurement of the folate catabolites p-aminobenzoylglutamate (pABG) and acetamidobenzoylglutamate (apABG) in serum and urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS). DESIGN AND METHODS Urine, serum and aqueous standards were thawed. Two microliters of d3-glutamic acid (d3-Glu;(More)
A case involving a fatal poisoning (suicide) by the insecticide malathion is described. The intact insecticide was found in the post-mortem blood and gastric contents at concentrations of 1.8 and 978 micrograms/ml, respectively. None of the insecticide was found in the autopsied liver tissue. Gas chromatography-mass spectrometry (GC-MS) techniques were used(More)