Vitamin Analysis

Sauberlich HE Skala JH Dowdy RP . Laboratory Tests For the Assessment of Nutritional Status. Cleveland, Ohio: CRC Press Inc, 1974.

FLAIR Concerted Action No. 10 Status Papers. Vitamins. Int J Vit Nutr Res 1993; 63: 247–95.

Gibson RS . Principles of Nutritional Assessment. Oxford: Oxford University Press, 1990.

Fidanza F , ed. Vitamin nutriture methodology. In: Nutritional Status Assessment: A Manual For Population Studies. London: Chapman & Hall, 1991: 185–330

Howard LJ . The neurologic syndrome of vitamin E deficiency: Laboratory and electrophysiological assessment. Nutr Rev 1990; 48: 169–77.

Goss-Sampson MA Muller DPR Lloyd JK . Clinical importance of vitamin E: A review. J Hum Nutr Dietet 1989; 2: 145–50.

Stephens NG Parsons A Schofield PM Kelly F Cheeseman K Mitchinson MJ . Randomised controlled trial of vitamin E in patients with coronary disease: Cambridge Heart Antioxidant Study (CHAOS). Lancet 1996; 347: 781–6.

De Leenheer AP Nelis HJ Lambert WE Bauwens RM . Review: Chromatography of fat-soluble vitamins in clinical chemistry. J Chromatogr 1988; 429: 3–58.

Neeld JB Pearson WN . Macro- and micromethods for the determination of serum vitamin A using trifluoroacetic acid. J Nutr 1963; 79: 454–62.

Thompson JN Erdody P Brien R Murray TK . Simultaneous Huorimetric determinations of vitamin A and E in human serum and plasma. Biochem Med 1973; 8: 403–14.

Sowell AL Huff DL Yeager PR Caudill SP Gunter EW . Retinol, α-tocopherol, lutein/zeaxanthin, β-cryptoxanthin, lycopene, α-carotene, trans β-carotene, and four retinol esters in serum determined simultaneously by reversed phase HPLC with multiwavelength detection. Clin Chem 1994;40:411–6.

Thurnham DI Smith E Flora PS . Concurrent liquid chromatographic assay of retinol, α-tocopherol, β-carotene, α-carotene, lycopene and β-cryptoxanthin in plasma, with tocopherol acetate as internal standard. Clin Chem 1988; 34: 337–81.

Vuilleumier JP Keller HE Fidanza F . Vitamin A (retinol) in plasma by HPLC. β-carotene in plasma by HPLC. Vitamin E (α-tocopherol). In: Fidanza F , ed. Nutritional Status Assessment—A Manual For Population Studies. London: Chapman & Hall: 1991: 191–5, 200–3, 209–14.

Schrijver J Speek AJ van den Berg H . Vitamin A (retinol) in plasma and serum by HPLC-micro-method. In. Fidanza F , ed. Nutritional Status Assessment—A Manual For Population Studies. London: Chapman & Hall, 1991: 195–200.

Epler KS Ziegler RG Craft NE . Liquid chromatographic method for the determination of carotenoids, retinoids and tocopherols in human serum and in food. J Chromatogr 1993; 619: 37–48.

MacCrehan WA Schonberger E . Determination of retinol, alpha-tocopherol and beta-carotene in serum by liquid chromatography with absorbance and electrochemical detection. Clin Chem 1987; 33: 1585–92.

Finckh B Kontush A Commentz J Hübner C Burdelski M Kohlshutter A . Monitoring of ubiquinol-10, ubiquinone-10, carotenoids and tocopherols in neonatal plasma microsamples using high performance liquid chromatography with coulometric electro-chemical detection. Anal Biochem 1995; 232: 210–6.

Shi H Ma Y Humphrey JH Craft NE . Determination of vitamin A in dried human blood spots by high performance capillary electrophoresis with laser-excited fluorescence detection. J Chromatogr B 1995; 665: 89–96.

Stoltzfus RJ Underwood BA . Breast-milk vitamin A as an indicator of the vitamin A status of women and infants. Bull WHO 1995: 73: 703–11.

Sharpless KS Duewer DL . Population distributions and inter-laboratory reproducibility for fat-soluble vitamin-related compounds in human serum. Anal Chem 1995; 67: 4416–22

Eisman JA . Vitamin D receptor gene alleles and osteoporosis. An affirmative view. J Bone Min Res 1995; 10: 1289–93.

Peacock M . Vitamin D receptor gene alleles and osteoporosis: A contrasting view. J Bone Min Res 1995; 10: 1294–7.

Stamp TCB . Factors in human vitamin D nutrition and in the production and cure of classical rickets. Proc Nutr Soc 1975; 34: 119–30.

Gregory JR Collins DL Davies PSW Hughes JM Clarke PC . In: Report of the diet and nutrition survey. National Diet and Nutrition Survey: Children Aged 1–5 to 4–5 Years, Vol. I. London: HMSO, 1995.

Seamark DA Trafford DJH Makin HL . The estimation of vitamin D and its metabolites in human plasma. J Steroid Biochem 1981; 14: 111–23.

Porteous CE Coldwell RD Trafford DJH Makin HLJ . Recent developments in the measurement of vitamin D and its metabolites in human body fluids. J Steroid Biochem 1987; 28: 785–801.

Iqbal SJ . Vitamin D metabolism and the clinical aspects of measuring metabolites. Ann Clin Biochem 1994; 31: 109–24.

Hollis BW . Assessment of vitamin D. Nutritional and Hormone Status: What to measure and how to do it. Calif Tissue Int 1996; 58: 4–5.

Hollis BW . 1,25-dihydroxyvitamin D₃-26,23-lactone interferes in determination of 1,25-dihydroxyvitamin D by RIA after immuno-extraction. Clin Chem 1995; 41: 1313–4.

Hollis BW Kamerud JQ Kurkowski A Beaulieu J Napoli JL . Quantification of circulating 1,25-dihydroxyvitamin D by radio-immunoassay with an 1–125 labelled tracer. Clin Chem 1996; 42: 586–92.

Lawson DEM . Competitive binding assay for 25-hydroxyvitamin D using specific binding proteins. In: McCormick DB Wright LD , eds. Methods in Enzymology, Vol. 67. New York: Academic Press, 1980: 459–65.

Van den Berg H Schrijver J Boshuis PG . Vitamin D (25-OHD) in serum by competitive protein binding assay. In: Fidanza F , ed. Nutritional Status Assessment—A Manual for Population Studies. London: Chapman & Hall, 1991: 203–9.

Hollis BW Napoli JL . Improved radioimmunoassay for vitamin D and its use in assessing vitamin D status. Clin Chem 1985; 31: 1815–9.

Hollis BW Kamerud JQ Selvaag SR Lorenz JD Napoli JL . Determination of vitamin D status by radioimmunoassay with an ¹²⁵I-labelled tracer. Clin Chem 1993; 39: 529–33.

King EH Hopfer SM Stone JA . Evaluation of the Incstar 25-hydroxy-vitamin D (25-OH-D) ¹²⁵I RIA kit. Clin Chem 1994; 40: 1035A.

Abbotts J Davies PSW Prentice A Stirling DM Yan L Bates C . 25(OH)-vitamin D assay in plasma: Experience in using a commercial kit assay for survey work. Ann Clin Biochem 1995; 32: 591–2.

Turnbull H Trafford DJH Makin HLJ . A rapid and simple method for the measurement of plasma 25-hydroxyvitamin D₂ and 25-hydroxyvitamin D₃ using Sep-Pak C₁₈ cartridges and a single high performance liquid chromatographic step. Clin Chim Acta 1982; 120: 65–76.

Carter GD Hewitt J . 25-Hydroxyvitamin D (25-OHD) assays: The state of the art [Abstract]. J Endocrinol 1996; 148 (suppl): P313.

Gunter EW Lewis BG Koncikowski SM . Laboratory Procedures Used for the Third National Health and Nutrition Examination Survey (NHANES III), 1988–1994. Atlanta, GA: US Dept of Health and Human Services PHS, CDC, NCEH; Hyattsville, MD: NCHS.

Vieth R Chan A Pollard A . ¹²⁵I-R1A kit cannot distinguish vitamin D deficiency as well as a more specific assay for 25-hydroxyvitamin D. Clin Biochem 1995; 28: 175–9.

Gregory JR Collins DL Davies PSW Hughes JM Clarke PC . Report of the diet and nutrition survey, National Diet and Nutrition Survey: Children Aged 1–5 to 4–5 Years. Vol. 1. London: HMSO, 1995.

Shearer MJ Vitamin K . Lancet 1995; 345: 229–34.

Shearer MJ Bach A Kohlmeier M . Chemistry, nutritional sources, tissue distribution and metabolism of vitamin K with special reference to bone health. J Nutr 1996; 126: 1181S–86S.

Sokoll LJ O'Brien ME Camilo ME Sadowski JA . Under-carboxylated osteocalcin and development of a method to determine vitamin K₁ status. Clin Chem 1995; 41: 1121–8.

Sokoll LJ Sadowski JA . Comparison of biochemical indexes for assessing vitamin K nutritional status in a healthy adult population. Am J Clin Nutr 1996; 63: 566–73.

Shearer MJ . Measurement of phylloquinone (vitamin K₁) in serum or plasma by HPLC. In: Fidanza F , ed. Nutritional Status Assessment—A Manual For Population Studies. London: Chapman & Hall, 1991: 214–20.

Haroon Y Bacon DS Sadowski JA . Liquid chromatographic determination of vitamin K₁ in plasma, with fluorometric detection. Clin Chem 1986; 32: 1925–9.

Langenberg JP Tjaden UR . Determination of (endogenous) vitamin K₁ in human plasma by reversed-phase high performance liquid chromatography using fluorometric detection after post-column electro-chemical reduction. Comparison with ultraviolet, single and dual electrochemical detection. J Chromatogr 1984; 305: 61–72.

Lambert WE de Leenheer AP Lefevere MF . Determination of vitamin K in serum using HPLC with post-column reaction and fluorescence detection. J Chromatogr Sci 1986; 24: 76–9.

Jacob E Elmadfa I . Rapid HPLC assay for the assessment of vitamin K₁, A, E and beta-carotene status in children (7–19 years). Int J Vit Nutr Res 1995; 65: 31–5.

MacCrehan WA Schonberger E . Determination of vitamin K₁ in serum using catalytic-reduction liquid chromatography with fluorescence detection. J Chromatogr B 1995; 670: 209–17.

Greer FR . The importance of vitamin K as a nutrient during the first year of life. Nutr Res 1995; 15: 289–310.

Sauberlich HE Dowdy RP Skala JH . Laboratory Tests For the Assessment of Nutritional Status: Thiamin (Vitamin B₁). Cleveland, Ohio: CRC Press, 1974: 22–30.

Vuilleumier JP Keller HE Fidanza F Bitsch R Schrijver J Speek AJ . Erythrocyte transketolase activity; total thiamin in whole blood by HPLC; thiamin in urine. In: Fidanza F , ed. Nutritional Status Assessment—A Manual For Population Studies. London: Chapman & Hall, 1991: 228–44.

Schouten H Van Eps Statius LW Boudier Struyker AM . Transketolase in blood. Clin Chim Acta 1964; 10: 474–6.

Smeets EHJ Muller H de Wael J . A NADH-dependent transketolase assay in erythrocyte hemolysates. Clin Chem Acta 1971; 33: 379–86.

Bayoumi RA Rosalki SB . Evaluation of methods of coenzyme activation of erythrocyte enzymes for detection of deficiency of vitamins B₁, B₂ and B₆ . Clin Chem 1976; 22: 327–35.

Walzem RL Clifford AJ . Determination of blood transketolase: An improved procedure with optimized conditions. J Micronutr Anal 1988; 4: 17–32.

Vuilleumier JP Keller HE Keck E . Clinical chemical methods for the routine assessment of the vitamin status in human populations. Part III: The apoenzyme stimulation tests for vitamin B₁, B₂ and B₆ adapted to the Cobas-Bio analyzer. Int J Vit Nutr Res 1990; 60: 126–35.

Mount J Hedman E Herd C Jupp R Kearney E Marsh A . Adaptation of coenzyme stimulation assays for the nutritional assessment of vitamins B₁, B₂ and B₆ using the Cobas Bio Centrifugal analyser. Ann Clin Biochem 1987; 24: 41–6.

Anderson SH Nicol AD . A fluorimetric method for measurement of erythrocyte transketolase activity. Ann Clin Biochem 1986; 23: 180–9.

Puxty JAH Haskew AE Ratcliffe JG McMurray J . Changes in erythrocyte transketolase activity and the thiamine pyrophosphate effect during storage of blood. Ann Clin Biochem 1985; 22: 423–7.

Nixon PF Price J Norman-Hicks M Williams GM Kerr RA . The relationship between erythrocyte transketolase activity and the ‘TPP effect’ in Wernicke's encephalopathy and other thiamine deficiency states. Clin Chim Acta 1990; 192: 89–98.

Baines M Davies G . The evaluation of erythrocyte thiamin diphosphate as an indicator of thiamin status in man, and its comparison with erythrocyte transketolase activity measurements. Ann Clin Biochem 1988; 25: 698–705.

Bates CJ . Human riboflavin requirements and metabolic consequences of deficiency in man and animals. Wld Rev Nutr Diet 1987; 50: 215–65.

Tillotson JA Baker EM . An enzymatic measurement of riboflavin status in man. Am J Clin Nutr 1972; 25: 425–31.

Hornbeck CL Bradley DW . Concentrations of FAD and glutathione as they affect values for erythrocyte glutathione reductase. Clin Chem 1974; 20: 512–3.

Bayoumi RA Rosalki SB . Evaluation of methods of coenzyme activation of erythrocyte enzymes for detection of vitamins B₁, B₂ and B₆ . Clin Chem 1976; 22: 327–35.

Garry PJ Owen GM . An automated flavin adenine dinucleotide-dependent glutathione reductase assay for assessing riboflavin nutriture. Am J Clin Nutr 1976; 29: 663–74.

Powers HJ Bates CJ Prentice AM Lamb WH Jepson M Bowman H . The relative effectiveness of iron and iron with riboflavin in correcting a microcytic anaemia in men and children in rural Gambia. Hum Nutr Clin Nutr 1983; 37C: 413–25.

Thurnham DI Rathakette P . Incubation of NAD(P)H₂: glutathione oxidoreductase (EC 1.6.4.2) with flavin adenine dinucleotide for maximal stimulation in the measurement of riboflavin status. Br J Nutr 1982; 48: 459–66.

Vuilleumier JP Keller HE Fidanza F Bitsch R Schrijver J Speek AJ . Erythrocyte glutathione reductase activity: Flavin adenine dinucleotide (FAD) in whole blood by HPLC; riboflavin in urine by HPLC. In: Fidanza F , ed. Nutritional Status Assessment—A Manual For Population Studies. London: Chapman & Hall, 1991: 244–58.

Bates CJ Powers HJ Prentice AM . Measurement of riboflavin status by activation coefficient of erythrocyte glutathione reductase, and its automation with a Roche Cobas Bio centrifugal analyzer. In: Fidanza F , ed. Nutritional Status Assessment Methodology for Individuals and Groups. Perugia, Group of European Nutritionists, 1986: 173–83.

Schaumberg H Kaplan J Windebank A Vick N Rasmus S Pleasure D Brown MJ . Sensory neuropathy from pyridoxine abuse. A new megavitamin syndrome. N Engl J Med 1983; 309: 445–8.

Bender DA . Lack of concordance between two biochemical indices of vitamin B₆ nutritional status. Proc Nutr Soc 1993; 52: 315A.

Vuilleumier JP Keller HE Fidanza F Schrijver J Speek AJ van den Berg H . Erythrocyte aspartate transaminase; pyridoxal 5′-phosphate (PLP) in whole blood by HPLC; Pyridoxal 5′-phosphate in plasma by radioenzymatic assay using tyrosine decarboxylase apoenzyme; 4-pyridoxic acid in urine by HPLC. In: Fidanza F , ed. Nutritional Status Assessment—A Manual For Population Studies. London: Chapman & Hall, 1991: 266–82.

Edwards P Liu PKS Rose GA . A simple liquid chromatographic method for measuring vitamin B₆ compounds in plasma. Clin Chem 1989; 35: 241–5.

Gregory JF . Determination of pyridoxal 5′-phosphate as the semi-carbazone derivative using high performance liquid chromatography. Anal Biochem 1980; 102: 374–9.

Ubbink JB Serfontein WJ de Villiers LS . Stability of pyridoxal 5′-phosphate semicarbazone: Applications in plasma vitamin B₆ analysis and population surveys of vitamin B₆ nutritional status. J Chromatogr 1985; 342: 277–84.

Naoi M Ichinose H Takahashi T Nagatsu T . Sensitive assay for determination of pyridoxal 5′-phosphate in enzymes using high performance liquid chromatography after derivatisation with cyanide. J Chromatogr 1988; 434: 209–14.

Millart H Lamiable D . Determination of pyridoxal 5′-phosphate in human serum by reversed-phase high performance liquid chromatography combined with spectrofluorimetric detection of 4-pyridoxic acid 5′-phosphate as a derivative. Analyst 1989; 114: 1225–8.

Schoental R . Mouldy grain and the aetiology of pellagra: The role of the toxic metabolites of Fusarium. Biochem Soc Trans 1980; 8: 147–50.

Fu CS Swendseid ME Jacob RA McKee RW . Biochemical markers for assessment of niacin status in young men: Levels of erythrocyte niacin coenzymes and plasma tryptophan. J Nutr 1989; 119: 1949–55.

Carpenter KJ Kodicek E . The fluorimetric estimation of N'-methyl-nicotinamide and its differentiation from coenzyme 1. Biochem J 1950; 46: 421–6.

Sandhu JS Fraser DR . Measurement of niacin metabolites in urine by high pressure liquid chromatography. A simple, sensitive assay of niacin nutritional status. Int J Vit Nutr Res 1981; 51: 139–44.

Somogyi A Siebert D Bochner F . Determination of endogenous concentrations of N¹-methyl-nicotinamide in human plasma and urine by high performance liquid chromatography. Anal Biochem 1990; 187: 160–5.

Shibata K Kawada T Iwai K . Microdetermination of N¹-methyl-2-pyridone-5-carboxamide, a major metabolite of nicotinic acid and nicotinamide, in urine by high performance liquid chromatography. J Chromatogr 1987; 417: 173–7.

Shibata K Kawada T Iwai K . Simultaneous microdetermination of nicotinamide and its major metabolities. N¹-methyl-2-pyridone-5-carboxamide and N¹-methyl-4-pyridone-3-carboxamide, by high performance liquid chromatography. J Chromatogr 1988; 424: 23–8.

Shibata K Matsuo H . Correlation between niacin equivalent intake and urinary excretion of its metabolites, N¹-methyl-nicotinamide, N¹-methyl-2-pyridone-5-carboxamide and N¹-methyl-4-pyridone-3-carboxamide, in humans consuming a self-selected food. Am J Clin Nutr 1989; 50: 114–9.

Picciano MF Stokstod ELR Gregory JF , eds. Folic Acid Metabolism in Health and Disease. New York: Wiley-Liss, 1990.

Bailey LB , ed. Folate in Health and Disease. New York: Marcel Dekker Inc, 1995.

O'Broin S Kelleher B . Microbiological assay on microtitre plates of folate in serum and red cells. J Clin Pathol 1992; 45: 344–7.

Shane B Tamura T Stokstad ELR . Folate assay: A comparison of radioassay and microbiological methods. Clin Chim Acta 1980; 100: 13–9.

Rothenberg SP DaCosta M Rosenberg Z . A radioassay for serum folate: Use of a two-phase sequential-incubation, ligand binding system. N Engl J Med 1972; 286: 3–7.

Dawson DW Fish DI Frew IDO Roome T Tilston I . Laboratory diagnosis of megaloblastic anaemia: Current methods assessed by external quality assurance trials. J Clin Pathol 1987; 40: 393–7.

Brown RD Jun R Hughes W Watman R Arnold B Kronenberg H . Red cell folate assays: Some answers to current problems with radio-assay variability. Pathology 1990; 22: 82–7.

Van den Berg H Finglas PM Bates C . FLAIR intercomparisons on serum and red cell folate. Int J Vit Nutr Res 1994; 64: 288–93.

Raiten DJ Fisher KD , eds. Assessment of folate methodology used in the third National Health and Nutritional Examination Survey (NHANES III, 1988–1994). J Nutr 1995; 125: 1375S–98S.

Gunter EW Bowman BA Caudill SP Twite DB Adams MJ . Results of an international round robin for serum and red cell folate. Clin Chem 1996; 42: 1689–94.

Lucock MD Hartley R Smithclls RW . A rapid and specific HPLC-electrochemical method for the determination of endogenous 5-methyl-tetrahydrofolic acid in plasma using solid phase sample preparation with internal standardisation. Biomed Chrom 1989; 3: 58–63.

Wilson DH Hermann R Hsu S Biegalski T Sohn L Forsythe C . Ion capture assay for folate with the Abbott IMx analyzer. Clin Chem 1995; 41: 1780–1.

Ueland PM Refsum H Brattstrom L . Plasma homocysteine and cardiovascular disease. In: Frances RBJ , ed. Atherosclerotic Cardio-vascular Disease. Hemostasia and Endothelial Function, Chap 8. New York: Marcel-Dekker Inc., 1992: 183–236.

Kelleher BP O'Broin SD . Microbiological assay for vitamin B₁₂ performed in 96-well microtitre plates. J Clin Pathol 1991; 4: 592–5.

Allen RH Seetharam B Podell E Alpers DH . Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factors. J Clin Invest 1978; 61: 47–54.

Mollin DL Hoffbrand AV Ward PG Lewis SM . Interlaboratory comparison of scrum vitamin B₁₂ assay. J Clin Pathol 1980; 33: 243–8.

Herbert V Colman N Palat D Manusselis C Drivas G Block E . Is there a ‘gold standard’ for human serum vitamin B₁₂ assay? J Lab Clin Med 1984; 104: 829–41.

Lee DSC Griffiths BW . Human serum vitamin Bp assay methods a review. Clin Biochem 1985; 18: 261–6.

Gilois CR Beattie G Mills SP . Measurement of vitamin B₁₂ and serum folic acid: a comparison of methods. Med Lab Sci 1986; 43: 140–4.

Das KC Manusselis C Herbert V . Determination of vitamin B₁₂ (cobalamin) in serum and erythrocytes by radioassay and of holo-transcobalamin II (Holo-TC II) and holo-haptocorrin (Holo-TC I and III) in serum by adsorbing holo-TC II on microfine silica. J Nutr Biochem 1991; 2: 455–64.

O'Sullivan JJ Leeming RJ Lynch SS Pollock A . Radioimmunoassay that measures serum vitamin B₁₂ . J Clin Pathol 1992; 45: 328–31.

Stabler SP Lindenbaum J Allen RH . The use of homocysteine and other metabolites in the specific diagnosis of vitamin B₁₂ deficiency. J Nutr 1996; 126: 1266S–72S.

Van den Berg H Schrijver J . Vitamin B₁₂ (total cobalamins) in serum by competitive protein-binding assay. In: Fidanza F , ed. Nutritional Status Assessment — A Manual For Population Studies. London: Chapman & Hall, 1991: 290–6.

Roth KS . Biotin in clinical medicine—a review. Am J Clin Nutr 1981; 34: 1967–74.

Carlson GL Williams N Barber D Shaffer JL Wales S Isherwood D . Biotin deficiency complicating long-term total parenteral nutrition in an adult patient. Clin Nutr 1995; 14: 186–90.

Schrijver J van Breederode N van den Berg H Bitsch R . Biotin in whole blood by nicrobiological assay; biotin in plasma or urine by RIA. In: Fidanza F , ed. Nutritional Status Assessment: A Manual for Population Studies. London: Chapman & Hall, 1991: 296–303.

Sanghvi RS Lemons RM Baker H Thoene JG . A simple method for determination of plasma and urinary biotin. Clin Chim Acta 1982; 124: 85–90.

Wellenberg GJ Banks JN . Enzyme linked sorbent assay to quantify d-biotin in blood. J Sci Fd Agric 1993; 63: 1–5.

Velazquez A Zamudio S Baez A Murguia-Corral R Rangel-Peniche B Carrasco A . Indicators of biotin status: A study of patients on prolonged total parenteral nutrition. Eur J Clin Nutr 1990; 44: 11–16.

Velazquez A Teran M Baez A Gutierrez J Rodriguez R . Biotin supplementation affects lymphocyte carboxylases and plasma biotin in severe protein-energy malnutrition. Am J Clin Nutr 1995; 61: 385–91.

Basu TK Dickerson JWT . Vitamins In Human Health and Diseuse. Aberdeen: CAB International, 1996.

Maiani G Azzini E Ferro-Luzzi A Vitamin C . Int J Vit Nutr Res 1993; 63: 289–95.

Washko PW Welch RW Dhariwal KR Wang Y Levine M . Ascorbic acid and dehydroascorbic acid analyses in biological samples. Anal Biochem 1992; 204: 1–14.

Wang S Schram IM Sund RB . Determination of plasma ascorbic acid by HPLC: Method and stability studies. Eur J Pharm Sci 1995; 3: 231–9.

Roe JH Kuether CA . The determination of ascorbic acid in whole blood and urine through the 2,4-dinitrophenylhydrazine derivative of dehydroascorbic acid. J Biol Chem 1943; 147: 399–107.

Bates C Schrijver J Speek AJ van den Berg H . Vitamin C in plasma and buffy coat of blood by dinitrophenyl hydrazine assays; Total vitamin C in whole blood and plasma by HPLC-micro-method. In: Fidanza F , ed. Nutritional Status Assessment — A Manual For Population Studies. London: Chapman & Hall, 1991: 309–19.

Deutsch MJ Weeks CE . Microfluorometric assay for vitamin C. J Assoc Official Agric Chem 1965; 48: 1248–56.

Vuilleumier JP Keck E . Fluorimetric assay of vitamin C in biological materials, using a centrifugal analyzer with fluorescence attachment. J Micronutr Anal 1989; 5: 25–34.

Moeslinger T Brunner M Wolf I Spieckermann PG . Spectrophotometric determination of ascorbic acid and dehydroascorbic acid. Clin Chem 1995; 41: 1177–81.

Sanderson MJ Schorah CJ . Measurement of ascorbic acid and dehydroascorbic acid in gastric juice by HPLC. Biomed Chromatogr 1987; 2: 197–202.

Ross MA . Determination of ascorbic acid and uric acid in plasma by high performance liquid chromatography. J Chrom 1994; 657: 197–200.

Kutnink MA Skala JH Sauberlich HE Omaye ST . Simultaneous determination of ascorbic acid, isoascorbic acid (erythorbic acid) and uric acid in human plasma by high performance liquid chromatography with amperometric detection. J Liq Chromatogr 1985; 8: 31–46.

Washko PW Hartzell WO Levine M . Ascorbic acid analysis using high performance liquid chromatography with coulometric electrochemical detection. Anal Biochem 1989; 181: 276–82.

Bates CJ . Use of homocysteine to stabilise ascorbic acid, or to reduce dehydroascorbic acid, during HPLC separation of large volumes of tissue extracts. Clin Chim Acta 1992; 205: 249–52.

Bates CJ . Members of EC FLAIR Concerted Action No. 10. Micronutrient Measurement, Absorption and Status: Plasma Vitamin C assays: A European Experience. Int J Vit Nutr Res 1994; 64: 283–7.

Margolis SA Paule RC Ziegler RG . Ascorbic and dehydroascorbic acids measured in plasma preserved with dithiothreitol or meta-phosphoric acid. Clin Chem 1990; 36: 1750–5.

Deutsch JC Kolhouse JF . Ascorbate and dehydroascorbate measurements in aqueous solutions and plasma determined by gas chromatography-mass spectrometry. Anal Chem 1993; 65: 321–6.

Toth JP Gregory JF . Analysis of folacin by GC/ MS: Structures and mass spectra of fluorinated derivatives of para-aminobenzoyl glutamic acid. Biomed Environm Mass Spectrom 1988; 17: 73–9.

Dueker SR Jones AD Smith GM Clifford AJ . Stable isotope methods for the study of β-carotene-d₈ metabolism in humans utilizing tandem mass spectrometry and high performance liquid chromatography. Anal Chem 1994; 66: 4177–85.

Caimi RJ Brenna JT . High-sensitivity liquid chromatography—combustion isotope ratio mass spectrometry of fat-soluble vitamins. J Mass Spectrom 1995; 30: 466–72.

Gregory J Foster K Tyler H Wiseman M . The Dietary and Nutritional Survey of British Adults (Office of Population Censuses and Surveys. Social Survey Division). London: HMSO, 1990.