Table 3.

Factor analysis of amino acids. Top panel: eigenvalues and percentage variance for six factors (F1—6) extracted from all data and the rotated factor matrix. Bold values indicate the factor that best represents each amino acid (i.e. correlation coefficient). Middle panel: one‐way generalized linear model (GLM) comparing methods. Bottom panel: Sidak post hoc pairwise comparisons of each method against the microcapillary method for each factor

	Factor
	1	2	3	4	5	6
Eigenvalue	5.96	4.38	1.74	1.48	1.14	1.06
% variance	23.4	20.6	15.4	10.5	6.71	6.17
Amino acids
Alanine (Ala)	−0.213	0.666	0.227	0.099	−0.229	−0.134
Arginine (Arg)	0.075	0.164	0.16	0.904	0.114	−0.095
Asparagine (Asn)	−0.066	0.027	0.157	0.032	0.929	−0.071
Aspartic acid (Asp)	0.059	0.685	0.273	0.096	0.007	0.312
Cystine (Cys)	0.111	0.096	0.025	0.874	−0.099	0.311
GABA	0.871	0.394	−0.029	0.145	−0.03	−0.102
Glutamic acid (Glu)	−0.001	0.513	0.39	0.45	0.02	−0.389
Glycine (Gly)	−0.215	0.778	0.21	0.211	−0.001	0.337
Histidine (His)	−0.156	0.261	0.755	0.003	0.384	0.083
Isoleucine (Ile)	0.891	−0.081	−0.057	−0.077	−0.037	0.074
Leucine (leu)	−0.112	0.305	0.232	0.149	−0.066	0.737
Lysine (lys)	0.148	0.854	0.019	0.009	0.095	0.164
Methionine (Met)	−0.255	0.872	0.193	0.094	0.141	−0.067
Phenylalanine (Phe)	0.28	0.428	0.596	0.106	−0.307	−0.182
Proline (Pro)	0.859	−0.17	−0.059	−0.09	−0.014	0.029
Serine (Ser)	−0.076	0.188	0.879	0.203	−0.108	0.11
Threonine (Thr)	−0.114	0.121	0.877	0.023	0.213	0.142
Tyrosine (Tyr)	0.953	−0.111	−0.035	0.147	−0.039	−0.107
Valine (Val)	0.956	−0.152	−0.052	0.153	−0.036	−0.079
1‐way GLM
${\mathrm{\chi }}_4^2$	597	186	6.97	3,23	5.07	19.6
p	<.001	<.001	.137	.520	.281	<.001
Sidak's pairwise post hoc tests against the microcapillary method
p‐value
Filter paper	.419	.931	.925	.985	.990	.969
Micro‐rinse	<.001	.003	.925	.733	.990	.969
Rinse 2 ml	.047	<.001	.231	.925	.441	.548
Wash 2 ml	.013	<.001	.679	.852	.990	.050

Post hoc comparisons are restricted to each column.

GABA, gamma‐aminobutyric acid.