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PubMed1997

Choosing sample volume to achieve maximum detection sensitivity and resolution with high-performance liquid chromatography columns of 1.0, 2.1 and 4.6 mm I.D.

The relationship between sample volume and the chromatographic performance factors of detection sensitivity and resolution were explored for high-performance liquid chromatography (HPLC) columns of 1.0, 2.1 and 4.6 mm I.D. Performance was evaluated for isocratic and gradient elution in systems having low, intermediate and high extracolumn dispersion. Sample volumes ranged from 0.4 microliter to 2 ml. This paper provides guideline for selecting sample injection parameters so that the performance of microbore columns is not needlessly sacrificed by using too small or too large a sample volume. The guidelines are extracted from the works of others and are modified by our own experimental results. Comments are also made on the relative merits of various injection techniques.

Chromatography, High Pressure Liquid↗

PubMed1983

A comparison of diagnostic methods to differentiate diabetes insipidus from primary polyuria: a review of 21 patients.

Direct measurement of plasma AVP and indirect assessment of antidiuretic activity during standard dehydration tests were made in 21 polyuric and polydipsic patients to establish the efficacy of each method in determining the cause of polyuria. Patients with acquired nephrogenic diabetes insipidus (e.g. diabetes mellitus, renal failure, hypercalcaemia) were excluded from the study. Cranial diabetes insipidus was diagnosed by plasma AVP responses to osmotic stimulation during infusion of hypertonic 5% saline which were subnormal in 13 patients, 4 of whom had undetectable plasma AVP and 3 who had reduced but osmoregulated AVP release. Standard water deprivation tests confirmed cranial diabetes insipidus in all but 2 patients who were diagnosed as partial nephrogenic diabetes insipidus. The remaining 8 patients had normal, osmoregulated AVP secretion; the cause of their polyuria was determined by their renal response to desmopressin. Two patients had nephrogenic diabetes insipidus and 6 had primary polydipsia. The majority of polyuric patients could be accurately diagnosed by carefully performed dehydration tests. We suggest that direct measurements of plasma AVP during osmotic stimulation are only necessary to distinguish mild forms of cranial from nephrogenic diabetes, or to define precisely the characteristics of AVP secretion.

Adolescent↗